Detecting Cosmic Neutrinos with IceCube at the Earth’s South Pole

I thought there were a bit too many questions/interruptions for my taste, mainly because you can’t really hear the questions posed by the members of the audience, but aside from that it’s a decent lecture. I’ve added a few links below which covers some of the topics discussed in the lecture.

Neutrino astronomy.
Antarctic Impulse Transient Antenna (ANITA).
Neutral pion decays.
IceCube Neutrino Observatory.
Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector (Science).
Atmospheric and astrophysical neutrinos above 1 TeV interacting in IceCube.
Notes on isotropy.
Measuring the flavor ratio of astrophysical neutrinos.
Supernova 1987A neutrino emissions.

July 18, 2017 Posted by | Astronomy, Lectures, Physics, Studies | Leave a comment


“The purpose of this book is to give the reader a very brief introduction to various different aspects of gravity. We start by looking at the way in which the theory of gravity developed historically, before moving on to an outline of how it is understood by scientists today. We will then consider the consequences of gravitational physics on the Earth, in the Solar System, and in the Universe as a whole. The final chapter describes some of the frontiers of current research in theoretical gravitational physics.”

I was not super impressed by this book, mainly because the level of coverage was not quite as high as has been the level of coverage of some of the other physics books in the OUP – A Brief Introduction series. But it’s definitely an okay book about this topic, I was much closer to a three star rating on goodreads than a one star rating, and I did learn some new things from it. I might still change my mind about my two-star rating of the book.

I’ll cover the book the same way I’ve covered some of the other books in the series; I’ll post some quotes with some observations of interest, and then I’ll add some supplementary links towards the end of the post. ‘As usual’ (see e.g. also the introductory remarks to this post) I’ll add links to topics even if I have previously, perhaps on multiple occasions, added the same links when covering other books – the idea behind the links is to remind me – and indicate to you – which kinds of topics are covered in the book.

“[O]ver large distances it is gravity that dominates. This is because gravity is only ever attractive and because it can never be screened. So while most large objects are electrically neutral, they can never be gravitationally neutral. The gravitational force between objects with mass always acts to pull those objects together, and always increases as they become more massive.”

“The challenges involved in testing Newton’s law of gravity in the laboratory arise principally due to the weakness of the gravitational force compared to the other forces of nature. This weakness means that even the smallest residual electric charges on a piece of experimental equipment can totally overwhelm the gravitational force, making it impossible to measure. All experimental equipment therefore needs to be prepared with the greatest of care, and the inevitable electric charges that sneak through have to be screened by introducing metal shields that reduce their influence. This makes the construction of laboratory experiments to test gravity extremely difficult, and explains why we have so far only probed gravity down to scales a little below 1mm (this can be compared to around a billionth of a billionth of a millimetre for the electric force).”

“There are a large number of effects that result from Einstein’s theory. […] [T]he anomalous orbit of the planet Mercury; the bending of starlight around the Sun; the time delay of radio signals as they pass by the Sun; and the behaviour of gyroscopes in orbit around the Earth […] are four of the most prominent relativistic gravitational effects that can be observed in the Solar System.” [As an aside, I only yesterday watched the first ~20 minutes of the first of Nima Arkani-Hamed’s lectures on the topic of ‘Robustness of GR. Attempts to Modify Gravity’, which was recently uploaded on the IAS youtube channel, before I concluded that I was probably not going to be able to follow the lecture – I would have been able to tell Hamed, on account of having read this book, that the name of the ‘American’ astronomer whose name eluded him early on in the lecture (5 minutes in or so) was John Couch Adams (who was in fact British, not American)].

“[T]he overall picture we are left with is very encouraging for Einstein’s theory of gravity. The foundational assumptions of this theory, such as the constancy of mass and the Universality of Free Fall, have been tested to extremely high accuracy. The inverse square law that formed the basis of Newton’s theory, and which is a good first approximation to Einstein’s theory, has been tested from the sub-millimetre scale all the way up to astrophysical scales. […] We […] have very good evidence that Newton’s inverse square law is a good approximation to gravity over a wide range of distance scales. These scales range from a fraction of a millimetre, to hundreds of millions of metres. […] We are also now in possession of a number of accurate experimental results that probe the tiny, subtle effects that result from Einstein’s theory specifically. This data allows us direct experimental insight into the relationship between matter and the curvature of space-time, and all of it is so far in good agreement with Einstein’s predictions.”

“[A]ll of the objects in the Solar System are, relatively speaking, rather slow moving and not very dense. […] If we set our sights a little further though, we can find objects that are much more extreme than anything we have available nearby. […] observations of them have allowed us to explore gravity in ways that are simply impossible in our own Solar System. The extreme nature of these objects amplifies the effects of Einstein’s theory […] Just as the orbit of Mercury precesses around the Sun so too the neutron stars in the Hulse–Taylor binary system precess around each other. To compare with similar effects in our Solar System, the orbit of the Hulse–Taylor pulsar precesses as much in a day as Mercury does in a century.”

“[I]n Einstein’s theory, gravity is due to the curvature of space-time. Massive objects like stars and planets deform the shape of the space-time in which they exist, so that other bodies that move through it appear to have their trajectories bent. It is the mistaken interpretation of the motion of these bodies as occurring in a flat space that leads us to infer that there is a force called gravity. In fact, it is just the curvature of space-time that is at work. […] The relevance of this for gravitational waves is that if a group of massive bodies are in relative motion […], then the curvature of the space-time in which they exist is not usually fixed in time. The curvature of the space-time is set by the massive bodies, so if the bodies are in motion, the curvature of space-time should be expected to be constantly changing. […] in Einstein’s theory, space-time is a dynamical entity. As an example of this, consider the supernovae […] Before their cores collapse, leading to catastrophic explosion, they are relatively stable objects […] After they explode they settle down to a neutron star or a black hole, and once again return to a relatively stable state, with a gravitational field that doesn’t change much with time. During the explosion, however, they eject huge amounts of mass and energy. Their gravitational field changes rapidly throughout this process, and therefore so does the curvature of the space-time around them.

Like any system that is pushed out of equilibrium and made to change rapidly, this causes disturbances in the form of waves. A more down-to-earth example of a wave is what happens when you throw a stone into a previously still pond. The water in the pond was initially in a steady state, but the stone causes a rapid change in the amount of water at one point. The water in the pond tries to return to its tranquil initial state, which results in the propagation of the disturbance, in the form of ripples that move away from the point where the stone landed. Likewise, a loud noise in a previously quiet room originates from a change in air pressure at a point (e.g. a stereo speaker). The disturbance in the air pressure propagates outwards as a pressure wave as the air tries to return to a stable state, and we perceive these pressure waves as sound. So it is with gravity. If the curvature of space-time is pushed out of equilibrium, by the motion of mass or energy, then this disturbance travels outwards as waves. This is exactly what occurs when a star collapses and its outer envelope is ejected by the subsequent explosion. […] The speed with which waves propagate usually depends on the medium through which they travel. […] The medium for gravitational waves is space-time itself, and according to Einstein’s theory, they propagate at exactly the same speed as light. […] [If a gravitational wave passes through a cloud of gas,] the gravitational wave is not a wave in the gas, but rather a propagating disturbance in the space-time in which the gas exists. […] although the atoms in the gas might be closer together (or further apart) than they were before the wave passed through them, it is not because the atoms have moved, but because the amount of space between them has been decreased (or increased) by the wave. The gravitational wave changes the distance between objects by altering how much space there is in between them, not by moving them within a fixed space.”

“If we look at the right galaxies, or collect enough data, […] we can use it to determine the gravitational fields that exist in space. […] we find that there is more gravity than we expected there to be, from the astrophysical bodies that we can see directly. There appears to be a lot of mass, which bends light via its gravitational field, but that does not interact with the light in any other way. […] Moving to even smaller scales, we can look at how individual galaxies behave. It has been known since the 1970s that the rate at which galaxies rotate is too high. What I mean is that if the only source of gravity in a galaxy was the visible matter within it (mostly stars and gas), then any galaxy that rotated as fast as those we see around us would tear itself apart. […] That they do not fly apart, despite their rapid rotation, strongly suggests that the gravitational fields within them are larger than we initially suspected. Again, the logical conclusion is that there appears to be matter in galaxies that we cannot see but which contributes to the gravitational field. […] Many of the different physical processes that occur in the Universe lead to the same surprising conclusion: the gravitational fields we infer, by looking at the Universe around us, require there to be more matter than we can see with our telescopes. Beyond this, in order for the largest structures in the Universe to have evolved into their current state, and in order for the seeds of these structures to look the way they do in the CMB, this new matter cannot be allowed to interact with light at all (or, at most, interact only very weakly). This means that not only do we not see this matter, but that it cannot be seen at all using light, because light is required to pass straight through it. […] The substance that gravitates in this way but cannot be seen is referred to as dark matter. […] There needs to be approximately five times as much dark matter as there is ordinary matter. […] the evidence for the existence of dark matter comes from so many different sources that it is hard to argue with it.”

“[T]here seems to be a type of anti-gravity at work when we look at how the Universe expands. This anti-gravity is required in order to force matter apart, rather than pull it together, so that the expansion of the Universe can accelerate. […] The source of this repulsive gravity is referred to by scientists as dark energy […] our current overall picture of the Universe is as follows: only around 5 per cent of the energy in the Universe is in the form of normal matter; about 25 per cent is thought to be in the form of the gravitationally attractive dark matter; and the remaining 70 per cent is thought to be in the form of the gravitationally repulsive dark energy. These proportions, give or take a few percentage points here and there, seem sufficient to explain all astronomical observations that have been made to date. The total of all three of these types of energy, added together, also seems to be just the right amount to make space flat […] The flat Universe, filled with mostly dark energy and dark matter, is usually referred to as the Concordance Model of the Universe. Among astronomers, it is now the consensus view that this is the model of the Universe that best fits their data.”


The universality of free fall.
Galileo’s Leaning Tower of Pisa experiment.
Isaac Newton/Philosophiæ Naturalis Principia Mathematica/Newton’s law of universal gravitation.
Kepler’s laws of planetary motion.
Luminiferous aether.
Special relativity.
General relativity.
Spacetime curvature.
Pound–Rebka experiment.
Gravitational time dilation.
Gravitational redshift space-probe experiment (Essot & Levine).
Michelson–Morley experiment.
Hughes–Drever experiment.
Tests of special relativity.
Eötvös experiment.
Torsion balance.
Cavendish experiment.
Geodetic precession.
Gravity Probe B.
White dwarf/neutron star/supernova/gravitational collapse/black hole.
Hulse–Taylor binary.
Arecibo Observatory.
PSR J1738+0333.
Gravitational wave.
Square Kilometre Array.
PSR J0337+1715.
Weber bar.
Laser Interferometer Space Antenna.
Edwin Hubble/Hubble’s Law.
Physical cosmology.
Alexander Friedmann/Friedmann equations.
Cosmological constant.
Georges Lemaître.
Ralph Asher Alpher/Robert Hermann/CMB/Arno Penzias/Robert Wilson.
Cosmic Background Explorer.
The BOOMERanG experiment.
Millimeter Anisotropy eXperiment IMaging Array.
Wilkinson Microwave Anisotropy Probe.
High-Z Supernova Search Team.
CfA Redshift Survey/CfA2 Great Wall/2dF Galaxy Redshift Survey/Sloan Digital Sky Survey/Sloan Great Wall.
Gravitational lensing.
Inflation (cosmology).
Lambda-CDM model.
Large Synoptic Survey Telescope.
Grand Unified Theory.
Renormalization (quantum theory).
String theory.
Loop quantum gravity.
Unruh effect.
Hawking radiation.
Anthropic principle.

July 15, 2017 Posted by | Astronomy, Books, cosmology, Physics | Leave a comment

Probing the Early Universe through Observations of the Cosmic Microwave Background

This lecture/talk is a few years old, but it was only made public on the IAS channel last week (…along with a lot of other lectures – the IAS channel has added a lot of stuff recently, including more than 150 lectures within the last week or so; so if you’re interested you should go have a look).

Below the lecture I have added a few links with stuff (wiki-articles and a few papers) related to the topics covered in the lecture. I didn’t read those links, but I skimmed them (and a few others, which I subsequently decided not to include as their coverage did not overlap sufficiently with the stuff covered in the lecture) and decided to add them in order to remind myself what kind of stuff was included in the lecture/allow others to infer what kind of stuff might be included in the lecture. The links naturally go into a lot more detail than does the lecture, but these are the sort of topics discussed/included.

The lecture is long (90 minutes + a short Q&A), but it was interesting enough for me to watch all of it. The lecturer displays a very high level of speech disfluency throughout the lecture, in the sense that I might not be surprised if I were told that the most commonly word encountered during this lecture was ‘um’ or ‘uh’, rather than more commonly encountered mode words like ‘the’, but you get used to it (at least I managed to sort of ‘tune it out’ after a while). I should caution that there’s a short ‘jump’ very early on in the lecture (at the 2 minute mark or so) where a small amount of frames were apparently dropped, but that should not scare you away from watching the lecture; that frame drop is the only one of its kind during the lecture, aside from a similar brief ‘jump’ around the 1 hour 9 minute mark.

Some links:

Astronomical interferometer.
Fourier transform.
Boomerang : A Balloon-borne Millimeter Wave Telescope and Total Power Receiver for Mapping Anisotropy in the Cosmic Microwave Background.
Observations of the Temperature and Polarization Anisotropies with Boomerang 2003.
Detection of the Power Spectrum of Cosmic Microwave Background Lensing by the Atacama Cosmology Telescope.
Secondary anisotropies of the CMB (review article).
Planck early results. VIII. The all-sky early Sunyaev-Zeldovich cluster sample.
Sunyaev–Zel’dovich effect.
A CMB Polarization Primer.
Spider: a balloon-borne CMB polarimeter for large angular scales.

July 13, 2017 Posted by | Astronomy, cosmology, Lectures, Physics | Leave a comment


“Every atom of our bodies has been part of a star, and every informed person should know something of how the stars evolve.”

I gave the book three stars on goodreads. At times it’s a bit too popular-science-y for me, and I think the level of coverage is a little bit lower than that of some of the other physics books in the ‘A Very Brief Introduction‘ series by Oxford University Press, but on the other hand it did teach me some new things and explained some other things I knew about but did not fully understand before and I’m well aware that it can be really hard to strike the right balance when writing books like these. I don’t like it when authors employ analogies instead of equations to explain stuff, but on the other hand I’ve seen some of the relevant equations before, e.g. in the context of IAS lectures, so I was okay with skipping some of the math because I know how the math here can really blow up in your face fast – and it’s not like this book has no math or equations, but I think it’s the kind of math most people should be able to deal with. It’s a decent introduction to the topic, and I must admit I have yet really to be significantly disappointed in a book from the physics part of this OUP series – they’re good books, readable and interesting.

Below I have added some quotes and observations from the book, as well as some relevant links to material or people covered in the book. Some of the links below I have also added previously when covering other books in the physics series, but I do not really care about that as I try to cover each book separately; the two main ideas behind adding links of this kind are: 1) to remind me which topics (…which I was unable to cover in detail in the post using quotes, because there’s too much stuff to cover in the book for that to make sense…) were covered in the book, and: 2) to give people who might be interested in reading the book an idea of which topics are covered therein; if I neglected to add relevant links simply because such topics were also covered in other books I’ve covered here, the link collection would not accomplish what I’d like it to accomplish. The link collection was gathered while I was reading the book (I was bookmarking relevant wiki articles along the way while reading the book), whereas the quotes included in the post were only added to the post after I had finished adding the links from the link collection; I am well aware that some topics covered in the quotes of the book are also covered in the link collection, but I didn’t care enough about this ‘double coverage of topics’ to remove those links that refer to material also covered in my quotes in this post from the link collection.

I think the part of the book coverage related to finding good quotes to include in this post was harder than it has been in the context of some of the other physics books I’ve covered recently, because the author goes into quite some detail explaining some specific dynamics of star evolution which are not easy to boil down to a short quote which is still meaningful to people who do not know the context. The fact that he does go into those details was of course part of the reason why I liked the book.

“[W]e cannot consider heat energy in isolation from the other large energy store that the Sun has – gravity. Clearly, gravity is an energy source, since if it were not for the resistance of gas pressure, it would make all the Sun’s gas move inwards at high speed. So heat and gravity are both potential sources of energy, and must be related by the need to keep the Sun in equilibrium. As the Sun tries to cool down, energy must be swapped between these two forms to keep the Sun in balance […] the heat energy inside the Sun is not enough to spread all of its contents out over space and destroy it as an identifiable object. The Sun is gravitationally bound – its heat energy is significant, but cannot supply enough energy to loosen gravity’s grip, and unbind the Sun. This means that when pressure balances gravity for any system (as in the Sun), the total heat energy T is always slightly less than that needed (V) to disperse it. In fact, it turns out to be exactly half of what would be needed for this dispersal, so that 2T + V = 0, or V = −2 T. The quantities T and V have opposite signs, because energy has to be supplied to overcome gravity, that is, you have to use T to try to cancel some of V. […] you need to supply energy to a star in order to overcome its gravity and disperse all of its gas to infinity. In line with this, the star’s total energy (thermal plus gravitational) is E = T + V = −T, that is, the total energy is minus its thermal energy, and so is itself negative. That is, a star is a gravitationally bound object. Whenever the system changes slowly enough that pressure always balances gravity, these two energies always have to be in this 1:2 ratio. […] This reasoning shows that cooling, shrinking, and heating up all go together, that is, as the Sun tries to cool down, its interior heats up. […] Because E = –T, when the star loses energy (by radiating), making its total energy E more negative, the thermal energy T gets more positive, that is, losing energy makes the star heat up. […] This result, that stars heat up when they try to cool, is central to understanding why stars evolve.”

“[T]he whole of chemistry is simply the science of electromagnetic interaction of atoms with each other. Specifically, chemistry is what happens when electrons stick atoms together to make molecules. The electrons doing the sticking are the outer ones, those furthest from the nucleus. The physical rules governing the arrangement of electrons around the nucleus mean that atoms divide into families characterized by their outer electron configurations. Since the outer electrons specify the chemical properties of the elements, these families have similar chemistry. This is the origin of the periodic table of the elements. In this sense, chemistry is just a specialized branch of physics. […] atoms can combine, or react, in many different ways. A chemical reaction means that the electrons sticking atoms together are rearranging themselves. When this happens, electromagnetic energy may be released, […] or an energy supply may be needed […] Just as we measured gravitational binding energy as the amount of energy needed to disperse a body against the force of its own gravity, molecules have electromagnetic binding energies measured by the energies of the orbiting electrons holding them together. […] changes of electronic binding only produce chemical energy yields, which are far too small to power stars. […] Converting hydrogen into helium is about 15 million times more effective than burning oil. This is because strong nuclear forces are so much more powerful than electromagnetic forces.”

“[T]here are two chains of reactions which can convert hydrogen to helium. The rate at which they occur is in both cases quite sensitive to the gas density, varying as its square, but extremely sensitive to the gas temperature […] If the temperature is below a certain threshold value, the total energy output from hydrogen burning is completely negligible. If the temperature rises only slightly above this threshold, the energy output becomes enormous. It becomes so enormous that the effect of all this energy hitting the gas in the star’s centre is life-threatening to it. […] energy is related to mass. So being hit by energy is like being hit by mass: luminous energy exerts a pressure. For a luminosity above a certain limiting value related to the star’s mass, the pressure will blow it apart. […] The central temperature of the Sun, and stars like it, must be almost precisely at the threshold value. It is this temperature sensitivity which fixes the Sun’s central temperature at the value of ten million degrees […] All stars burning hydrogen in their centres must have temperatures close to this value. […] central temperature [is] roughly proportional to the ratio of mass to radius [and this means that] the radius of a hydrogen-burning star is approximately proportional to its mass […] You might wonder how the star ‘knows’ that its radius is supposed to have this value. This is simple: if the radius is too large, the star’s central temperature is too low to produce any nuclear luminosity at all. […] the star will shrink in an attempt to provide the luminosity from its gravitational binding energy. But this shrinking is just what it needs to adjust the temperature in its centre to the right value to start hydrogen burning and produce exactly the right luminosity. Similarly, if the star’s radius is slightly too small, its nuclear luminosity will grow very rapidly. This increases the radiation pressure, and forces the star to expand, again back to the right radius and so the right luminosity. These simple arguments show that the star’s structure is self-adjusting, and therefore extremely stable […] The basis of this stability is the sensitivity of the nuclear luminosity to temperature and so radius, which controls it like a thermostat.”

“Hydrogen burning produces a dense and growing ball of helium at the star’s centre. […] the star has a weight problem to solve – the helium ball feels its own weight, and that of all the rest of the star as well. A similar effect led to the ignition of hydrogen in the first place […] we can see what happens as the core mass grows. Let’s imagine that the core mass has doubled. Then the core radius also doubles, and its volume grows by a factor 2 × 2 × 2 = 8. This is a bigger factor than the mass growth, so the density is 2/(2 × 2 × 2) = 1/4 of its original value. We end with the surprising result that as the helium core mass grows in time, its central number density drops. […] Because pressure is proportional to density, the central pressure of the core drops also […] Since the density of the hydrogen envelope does not change over time, […] the helium core becomes less and less able to cope with its weight problem as its mass increases. […] The end result is that once the helium core contains more than about 10% of the star’s mass, its pressure is too low to support the weight of the star, and things have to change drastically. […] massive stars have much shorter main-sequence lifetimes, decreasing like the inverse square of their masses […] A star near the minimum main-sequence mass of one-tenth of the Sun’s has an unimaginably long lifetime of almost 1013 years, nearly a thousand times the Sun’s. All low-mass stars are still in the first flush of youth. This is the fundamental fact of stellar life: massive stars have short lives, and low-mass stars live almost forever – certainly far longer than the current age of the Universe.”

“We have met all three […] timescales [see links below – US] for the Sun. The nuclear time is ten billion years, the thermal timescale is thirty million years, and the dynamical one […] just half an hour. […] Each timescale says how long the star takes to react to changes of the given type. The dynamical time tells us that if we mess up the hydrostatic balance between pressure and weight, the star will react by moving its mass around for a few dynamical times (in the Sun’s case, a few hours) and then settle down to a new state in which pressure and weight are in balance. And because this time is so short compared with the thermal time, the stellar material will not have lost or gained any significant amount of heat, but simply carried this around […] although the star quickly finds a new hydrostatic equilibrium, this will not correspond to thermal equilibrium, where heat moves smoothly outwards through the star at precisely the rate determined by the nuclear reactions deep in the centre. Instead, some bits of the star will be too cool to pass all this heat on outwards, and some will be too hot to absorb much of it. Over a thermal timescale (a few tens of millions of years in the Sun), the cool parts will absorb the extra heat they need from the stellar radiation field, and the hot parts rid themselves of the excess they have, until we again reach a new state of thermal equilibrium. Finally, the nuclear timescale tells us the time over which the star synthesizes new chemical elements, radiating the released energy into space.”

“[S]tars can end their lives in just one of three possible ways: white dwarf, neutron star, or black hole.”

“Stars live a long time, but must eventually die. Their stores of nuclear energy are finite, so they cannot shine forever. […] they are forced onwards through a succession of evolutionary states because the virial theorem connects gravity with thermodynamics and prevents them from cooling down. So main-sequence dwarfs inexorably become red giants, and then supergiants. What breaks this chain? Its crucial link is that the pressure supporting a star depends on how hot it is. This link would snap if the star was instead held up by a pressure which did not care about its heat content. Finally freed from the demand to stay hot to support itself, a star like this would slowly cool down and die. This would be an endpoint for stellar evolution. […] Electron degeneracy pressure does not depend on temperature, only density. […] one possible endpoint of stellar evolution arises when a star is so compressed that electron degeneracy is its main form of pressure. […] [Once] the star is a supergiant […] a lot of its mass is in a hugely extended envelope, several hundred times the Sun’s radius. Because of this vast size, the gravity tying the envelope to the core is very weak. […] Even quite small outward forces can easily overcome this feeble pull and liberate mass from the envelope, so a lot of the star’s mass is blown out into space. Eventually, almost the entire remaining envelope is ejected as a roughly spherical cloud of gas. The core quickly exhausts the thin shell of nuclear-burning material on its surface. Now gravity makes the core contract in on itself and become denser, increasing the electron degeneracy pressure further. The core ends as an extremely compact star, with a radius similar to the Earth’s, but a mass similar to the Sun, supported by this pressure. This is a white dwarf. […] Even though its surface is at least initially hot, its small surface means that it is faint. […] White dwarfs cannot start nuclear reactions, so eventually they must cool down and become dark, cold, dead objects. But before this happens, they still glow from the heat energy left over from their earlier evolution, slowly getting fainter. Astronomers observe many white dwarfs in the sky, suggesting that this is how a large fraction of all stars end their lives. […] Stars with an initial mass more than about seven times the Sun’s cannot end as white dwarfs.”

“In many ways, a neutron star is a vastly more compact version of a white dwarf, with the fundamental difference that its pressure arises from degenerate neutrons, not degenerate electrons. One can show that the ratio of the two stellar radii, with white dwarfs about one thousand times bigger than the 10 kilometres of a neutron star, is actually just the ratio of neutron to electron mass.”

“Most massive stars are not isolated, but part of a binary system […]. If one is a normal star, and the other a neutron star, and the binary is not very wide, there are ways for gas to fall from the normal star on to the neutron star. […] Accretion on to very compact objects like neutron stars almost always occurs through a disc, since the gas that falls in always has some rotation. […] a star’s luminosity cannot be bigger than the Eddington limit. At this limit, the pressure of the radiation balances the star’s gravity at its surface, so any more luminosity blows matter off the star. The same sort of limit must apply to accretion: if this tries to make too high a luminosity, radiation pressure will tend to blow away the rest of the gas that is trying to fall in, and so reduce the luminosity until it is below the limit. […] a neutron star is only 10 kilometres in radius, compared with the 700,000 kilometres of the Sun. This can only happen if this very small surface gets very hot. The surface of a healthily accreting neutron star reaches about 10 million degrees, compared with the 6,000 or so of the Sun. […] The radiation from such intensely hot surfaces comes out at much shorter wavelengths than the visible emission from the Sun – the surfaces of a neutron star and its accretion disc emit photons that are much more energetic than those of visible light. Accreting neutron stars and black holes make X-rays.”

“[S]tar formation […] is harder to understand than any other part of stellar evolution. So we use our knowledge of the later stages of stellar evolution to help us understand star formation. Working backwards in this way is a very common procedure in astronomy […] We know much less about how stars form than we do about any later part of their evolution. […] The cyclic nature of star formation, with stars being born from matter chemically enriched by earlier generations, and expelling still more processed material into space as they die, defines a cosmic epoch – the epoch of stars. The end of this epoch will arrive only when the stars have turned all the normal matter of the Universe into iron, and left it locked in dead remnants such as black holes.”

Stellar evolution.
Gustav Kirchhoff.
Robert Bunsen.
Joseph von Fraunhofer.
Absorption spectroscopy.
Emission spectrum.
Doppler effect.
Stellar luminosity.
Cecilia Payne-Gaposchkin.
Ejnar Hertzsprung/Henry Norris Russell/Hertzsprung–Russell diagram.
Red giant.
White dwarf (featured article).
Main sequence (featured article).
Gravity/Electrostatics/Strong nuclear force.
Pressure/Boyle’s law/Charles’s law.
Hermann von Helmholtz.
William Thomson (Kelvin).
Gravitational binding energy.
Thermal energy/Gravitational energy.
Virial theorem.
Kelvin-Helmholtz time scale.
Chemical energy/Bond-dissociation energy.
Nuclear binding energy.
Nuclear fusion.
Heisenberg’s uncertainty principle.
Quantum tunnelling.
Pauli exclusion principle.
Eddington limit.
Electron degeneracy pressure.
Nuclear timescale.
Number density.
Dynamical timescale/free-fall time.
Hydrostatic equilibrium/Thermal equilibrium.
Core collapse.
Hertzsprung gap.
Supergiant star.
Chandrasekhar limit.
Core-collapse supernova (‘good article’).
Crab Nebula.
Stellar nucleosynthesis.
Neutron star.
Schwarzschild radius.
Black hole (‘good article’).
Roy Kerr.
Jocelyn Bell.
Anthony Hewish.
Accretion/Accretion disk.
X-ray binary.
Binary star evolution.
SS 433.
Gamma ray burst.
Hubble’s law/Hubble time.
Cosmic distance ladder/Standard candle/Cepheid variable.
Star formation.
Pillars of Creation.
Jeans instability.
Initial mass function.

July 2, 2017 Posted by | Astronomy, Books, Chemistry, Physics | Leave a comment


Here’s what I wrote about the book on goodreads:

“I think the author was trying to do too much with this book. He covers a very large number of topics, but unfortunately the book is not easy to read because he covers in a few pages topics which other authors write entire books about. If he’d covered fewer topics in greater detail I think the end result would have been better. Despite having watched a large number of lectures on related topics and read academic texts about some of the topics covered in the book, I found the book far from easy to read, certainly compared to other physics books in this series (the books about nuclear physics and particle physics are both significantly easier to read, in my opinion). The author sometimes seemed to me to have difficulties understanding how large the potential knowledge gap between him and the reader of the book might be.

Worth reading if you know some stuff already and you’re willing to put in a bit of work, but don’t expect too much from the coverage.”

I gave the book two stars on goodreads.

I decided early on while reading the book that the only way I was going to cover this book at all here would be by posting a link-heavy post. I have added some quotes as well, but most of what’s going on in this book I’ll only cover by adding some relevant links to wiki articles dealing with these topics – as the link collection below should illustrate, although the subtitle of the book is ‘A Very Short Introduction’ it actually covers a great deal of ground (…too much ground, that’s part of the problem, as indicated above…). There are a lot of links because it’s just that kind of book.

First, a few quotes from the book:

“In thinking about the structure of an accretion disc it is helpful to imagine that it comprises a large number of solid rings, each of which spins as if each of its particles were in orbit around the central mass […] The speed of a circular orbit of radius r around a compact mass such as the Sun or a black hole is proportional to 1/r, so the speed increases inwards. It follows that there is shear within an accretion disc: each rotating ring slides past the ring just outside it, and, in the presence of any friction or viscosity within the fluid, each ring twists or torques the ring just outside it in the direction of rotation, trying to get it to rotate faster.

Torque is to angular momentum what force is to linear momentum: the quantity that sets its rate of change. Just as Newton’s laws yield that force is equal to rate of change of momentum, the rate of change of a body’s angular momentum is equal to the torque on the body. Hence the existence of the torque from smaller rings to bigger rings implies an outward transport of angular momentum through the accretion disc. When the disc is in a steady state this outward transport of angular momentum by viscosity is balanced by an inward transport of angular momentum by gas as it spirals inwards through the disc, carrying its angular momentum with it.”

“The differential equations that govern the motion of the planets are easily written down, and astronomical observations furnish the initial conditions to great precision. But with this precision we can predict the configuration of the planets only up to ∼ 40 Myr into the future — if the initial conditions are varied within the observational uncertainties, the predictions for 50 or 60 Myr later differ quite significantly. If you want to obtain predictions for 60 Myr that are comparable in precision to those we have for 40 Myr in the future, you require initial conditions that are 100 times more precise: for example, you require the current positions of the planets to within an error of 15m. If you want comparable predictions 60.15Myr in the future, you have to know the current positions to within 15mm.”

“An important feature of the solutions to the differential equations of the solar system is that after some variable, say the eccentricity of Mercury’s orbit, has fluctuated in a narrow range for millions of years, it will suddenly shift to a completely different range. This behaviour reflects the importance of resonances for the dynamics of the system: at some moment a resonant condition becomes satisfied and the flow of energy within the system changes because a small disturbance can accumulate over thousands or millions of cycles into a large effect. If we start the integrations from a configuration that differs ever so little from the previous configuration, the resonant condition will fail to be satisfied, or be satisfied much earlier or later, and the solutions will look quite different.”

“In Chapter 4 we saw that the physics of accretion discs around stars and black holes is all about the outward transport of angular momentum, and that moving angular momentum outwards heats a disc. Outward transport of angular momentum is similarly important for galactic discs. […] in a gaseous accretion disc angular momentum is primarily transported by the magnetic field. In a stellar disc, this job has to be done by the gravitational field because stars only interact gravitationally. Spiral structure provides the gravitational field needed to transport angular momentum outwards.

In addition to carrying angular momentum out through the stellar disc, spiral arms regularly shock interstellar gas, causing it to become denser, and a fraction of it to collapse into new stars. For this reason, spiral structure is most easily traced in the distribution of young stars, especially massive, luminous stars, because all massive stars are young. […] Spiral arms are waves of enhanced star density that propagate through a stellar disc rather as sound waves propagate through air. Like sound waves they carry energy, and this energy is eventually converted from the ordered form it takes in the wave to the kinetic energy of randomly moving stars. That is, spiral arms heat the stellar disc.”

“[I]f you take any reasonably representative group of galaxies, from the group’s luminosity, you can deduce the quantity of ordinary matter it should contain. This quantity proves to be roughly ten times the amount of ordinary matter that’s in the galaxies. So most ordinary matter must lie between the galaxies rather than within them.”

“The nature of a galaxy is largely determined by three numbers: its luminosity, its bulge-to-disc ratio, and the ratio of its mass of cold gas to the mass in stars. Since stars form from cold gas, this last ratio determines how youthful the galaxy’s stellar population is.

A youthful stellar population contains massive stars, which are short-lived, luminous, and blue […] An old stellar population contains only low-mass, faint, and red stars. Moreover, the spatial distribution of young stars can be very lumpy because the stars have not had time to be spread around the system […] a galaxy with a young stellar population looks very different from one with an old population: it is more lumpy/streaky, bluer, and has a higher luminosity than a galaxy of similar stellar mass with an old stellar population.”


Accretion disk.
Supermassive black hole.
Magnetorotational instability.
Astrophysical jet.
Herbig–Haro object.
SS 433.
Cygnus A.
Collimated light.
Light curve.
Lyman-alpha line.
Balmer series.
Star formation.
Stellar evolution.
Black-body radiation.
Helium flash.
White dwarf (featured article).
Planetary nebula.
Solar transition region.
Carbon detonation.
X-ray binary.
Inverse Compton scattering.
Quasi-periodic oscillation.
Urbain Le Verrier.
Perturbation theory.
Elliptic orbit.
Axial precession.
Orbital resonance.
Jupiter trojan (featured article).
Late Heavy Bombardment.
Lorentz factor.
Radio galaxy.
Gamma-ray burst (featured article).
Cosmic ray.
Hulse–Taylor binary.
Special relativity.
Lorentz covariance.
Lorentz transformation.
Relativistic Doppler effect.
Superluminal motion.
Fermi acceleration.
Shock waves in astrophysics.
Ram pressure.
Synchrotron radiation.
General relativity (featured article).
Gravitational redshift.
Gravitational lens.
Fermat’s principle.
SBS 0957+561.
Strong gravitational lensing/Weak gravitational lensing.
Gravitational microlensing.
Shapiro delay.
Gravitational wave.
Dark matter.
Dwarf spheroidal galaxy.
Luminosity function.
Lenticular galaxy.
Spiral galaxy.
Disc galaxy.
Elliptical galaxy.
Stellar dynamics.
Constant of motion.
Bulge (astronomy).
Interacting galaxy.
Coma cluster.
Galaxy cluster.
Anemic galaxy.
Decoupling (cosmology).

June 20, 2017 Posted by | Astronomy, Books, Physics | Leave a comment

Cosmology: Recent Results and Future Prospects

This is another old lecture from my bookmarks. I’m reasonably certain the main reason why I did not blog this earlier is that it’s a rather general and not very detailed overview lecture, so it doesn’t actually contain a lot of new stuff. Hubble’s work, the discovery of the cosmic microwave background, properties of the early universe and how it evolved, discussion of the cosmological constant, dark matter and dark energy, some recent observational results – most of the stuff he talks about should be familiar territory to people interested in the field. Before I watched the lecture I had expected it to include a lot more ‘recent results’ and ‘future prospects’ than were actually included; a big part of the lecture is just an overview of what we’ve learned since the 1930es.

June 7, 2017 Posted by | Astronomy, Lectures, Physics | Leave a comment

Nuclear physics

Below I have posted a few observations from the book, as well as a number of links to coverage of other topics mentioned/covered in the book. It’s a good book, the level of coverage is very decent considering the format of the publication.

“Electrons are held in place, remote from the nucleus, by the electrical attraction of opposite charges, electrons being negatively and the atomic nucleus positively charged. A temperature of a few thousand degrees is sufficient to break this attraction completely and liberate all of the electrons from within atoms. Even room temperature can be enough to release one or two; the ease with which electrons can be moved from one atom to another is the source of chemistry, biology, and life.”

“Quantum mechanics explains the behaviour of electrons in atoms, and of nucleons in nuclei. In an atom, electrons cannot go just where they please, but are restricted like someone on a ladder who can only step on individual rungs. When an electron drops from a rung with high energy to one that is lower down, the excess energy is carried away by a photon of light. The spectrum of these photons reveals the pattern of energy levels within the atom. Similar constraints apply to nucleons in nuclei. Nuclei in excited states, with one or more protons or neutrons on a high rung, also give up energy by emitting photons. The main difference between what happens to atomic electrons relative to atomic nuclei is the nature of the radiated light. In the former the light may be in the visible spectrum, whose photons have relatively low energy, whereas in the case of nuclei the light consists of X-rays and gamma rays, whose photons have energies that are millions of times greater. This is the origin of gamma radioactivity.”

“[A]ll particles that feel the strong interaction are made of quarks. […] Quarks that form nuclear particles come in two flavours, known as up (u) or down (d), with electrical charges that are fractions, +2/3 or −1/3 respectively, of a proton’s charge. Thus uud forms a proton and ddu a neutron. In addition to electrical charge, quarks possess another form of charge, known as colour. This is the fundamental source of the strong nuclear force. Whereas electric charge occurs in some positive or negative numerical amount, for colour charge there are three distinct varieties of each. These are referred to as red, green, or blue, by analogy with colours, but are just names and have no deeper significance. […] colour charge and electric charge obey very similar rules. For example, analogous to the behaviour of electric charge, colour charges of the same colour repel, whereas different colours can attract […]. A proton or neutron is thus formed when three quarks, each with a different colour, mutually attract one another. In this configuration the colour forces have neutralized, analogous to the way that positive and negative charges neutralize within an atom.”

“The relativistic quantum theory of colour is known as quantum chromodynamics (QCD). It is similar in spirit to quantum electrodynamics (QED). QED implies that the electromagnetic force is transmitted by the exchange of massless photons; by analogy, in QCD the force between quarks, within nucleons, is due to the exchange of massless gluons.”

“In a nutshell, the quarks in heavy nuclei are found to have, on average, slightly lower momenta than in isolated protons or neutrons. In spatial terms, this equates with the interpretation that individual quarks are, on average, less confined than in free nucleons. […] The overall conclusion is that the quarks are more liberated in nuclei when in a region of relatively high density. […] This interpretation of the microstructure of atomic nuclei suggests that nuclei are more than simply individual nucleons bound by the strong force. There is a tendency, under extreme pressure or density, for them to merge, their constituent quarks freed to flow more liberally. […] This freeing of quarks is a liberation of colour charges, and in theory should happen for gluons also. Thus, it is a precursor of what is hypothesized to occur within atomic nuclei under conditions of extreme temperature and pressure […] atoms are unable to survive at high temperatures and pressure, as in the sun for example, and their constituent electric charges—electrons and protons—flow independently as electrically charged gases. This is a state of matter known as plasma. Analogously, under even more extreme conditions, the coloured quarks are unable to configure into individual neutrons and protons. Instead, the quarks and gluons are theorized to flow freely as a quark–gluon plasma (QGP).”

“The mass of a nucleus is not simply the sum of the masses of its constituent nucleons. […] some energy is taken up to bind the nucleus together. This ‘binding energy’ is the difference between the mass of the nucleus and its constituents. […] The larger the binding energy, the greater is the propensity for the nucleus to be stable. Its actual stability is often determined by the relative size of the binding energy of the nucleus to that of its near neighbours in the periodic table of elements, or of other isotopes of the original elemental nucleus. As nature seeks stability by minimizing energy, a nucleus will seek to lower the total mass, or equivalently, to increase the binding energy. […] An effective guide to stability, and the pattern of radioactive decays, is given by the semi-empirical mass formula (SEMF).”

“For light nuclei the binding energy grows with A [the mass of the nucleus – US] until electrostatic repulsion takes over in large nuclei. […] At large values of Z [# of protons – US], the penalty of electrostatic charge, which extends throughout the nucleus, requires further neutrons to add to the short range attraction in compensation. Eventually, for Z > 82, the amount of electrostatic repulsion is so large that nuclei cannot remain stable, even when they have large numbers of neutrons. […] All nuclei heavier than lead are radioactive.”

“Three minutes after the big bang, the material universe consisted primarily of the following: 75% protons; 24% helium nuclei; a small number of deuterons; traces of lithium, beryllium, and boron, and free electrons. […] 300,000 years later, the ambient temperature had fallen below 10,000 degrees, that is similar to or cooler than the outer regions of our sun today. At these energies the negatively charged electrons were at last able to be held fast by electrical attraction to the positively charged atomic nuclei whereby they combined to form neutral atoms. Electromagnetic radiation was set free and the universe became transparent as light could roam unhindered across space.
The big bang did not create the elements necessary for life, such as carbon, however. Carbon is the next lightest element after boron, but its synthesis presented an insuperable barrier in the very early universe. The huge stability of alpha particles frustrates attempts to make carbon by collisions between any pair of lighter isotopes. […] Thus no carbon or heavier isotopes were formed during big bang nucleosynthesis. Their synthesis would require the emergence of stars.”

“In the heat of the big bang, quarks and gluons swarmed independently in quark–gluon plasma. Inside the sun, relatively cool, they form protons but the temperature is nonetheless too high for atoms to survive. Thus inside the sun, electrons and protons swarm independently as electrical plasma. It is primarily protons that fuel the sun today. […] Protons can bump into one another and initiate a set of nuclear processes that eventually converts four of them into helium-4 […] As the energy mc² locked into a single helium-4 nucleus is less than that in the original four protons, the excess is released into the surroundings, some of it eventually providing warmth here on earth. […] because the sun produces these reactions continuously over aeons, unlike big bang nucleosynthesis, which lasted mere minutes, unstable isotopes, such as tritium, play no role in solar nucleosynthesis.”

“Although individual antiparticles are regularly produced from the energy in collisions between cosmic rays, or in accelerator laboratories such as at CERN, there is no evidence for antimatter in bulk in the universe at large. […] To date, all the evidence is that the universe at large is made of matter to the exclusion of antimatter. […] One of the great mysteries in physics is how the symmetry between matter and antimatter was disturbed.”

Some links:

Nuclear physics.
Alpha decay/beta decay/gamma radiation.
Positron emission.
Rutherford model.
Bohr model.
Nuclear fission.
X-ray crystallography.
EMC effect.
Magic number.
Cosmic ray spallation.
Asymptotic giant branch.
CNO cycle.
Transuranium elements.
Island of stability.
Transfermium Wars.
Nuclear drip line.
Halo nucleus.
Lambda baryon.
Quark star.
Radiation therapy.
Rutherford backscattering spectrometry.
Particle-induced X-ray emission.

June 5, 2017 Posted by | Books, Physics | Leave a comment

Extraordinary Physics with Millisecond Pulsars

A few related links:
Millisecond pulsar.
PSR J0348+0432.
Pulsar timing array.
Detection of Gravitational Waves using Pulsar Timing (paper).
The strong equivalence principle.
European Pulsar Timing Array.
Parkes Observatory.
Gravitational wave.
Gravitational waves from binary supermassive black holes missing in pulsar observations (paper – it’s been a long time since I watched the lecture, but in my bookmarks I noted that some of the stuff included in this publication was covered in the lecture).

May 24, 2017 Posted by | Astronomy, Lectures, Papers, Physics | Leave a comment

Out of this World: A history of Structure in the Universe

This lecture is much less technical than were the last couple of lectures I posted, and if I remember correctly it’s aimed at a general audience (…the sort of ‘general audience’ that attends IAS lectures, but even so…). The lecture itself is quite short, only roughly 35 minutes long, but there’s a long Q&A session afterwards.

May 21, 2017 Posted by | Astronomy, Lectures, Physics | Leave a comment

Hydrodynamical Simulations of Galaxy Formation: Progress, Pitfalls, and Promises

“This calculation was relatively expensive, about 19 million CPU hours were spent on it.”


Posts including only one lecture is a recent innovation here on the blog as I have in the past bundled lectures so that a lecture post would include at least 2 or 3 lectures, but I am starting to come around to the idea that these new types of posts are a good idea. I have been going over some old lectures I’ve watched in the past recently, and it turns out that there are quite a few lectures I never got around to blogging; I have mentioned before how the 3 lectures per post format was likely suboptimal, in the sense that they tended to lead to lectures never being covered e.g. because of the long time lag between watching a lecture and blogging it (in the case of book blogging I tend to be much more likely to spend my time covering books I read recently, rather than books I read a while ago, and the same dynamic goes for lectures), and I think this impression is now confirmed.

As some of the lectures I’ll be covering in posts like these in the future are lectures I watched a long time ago my coverage will probably be limited to the actual lectures and the comments I wrote down when I first watched the lecture in question. I don’t want to add a few big lecture posts to just get rid of the backlog, mostly because this blog is obviously not nearly as active as it used to be, and adding single-lecture posts dropwise is an easy (…low-effort) and convenient way for me to keep the blog at least somewhat active. What I wrote down in my comments about the lecture above when I watched it, aside from the quote above, is that considering the very high-level physics included it was sort of surprising to me that the lecture was not so technical as to not be worth watching – but it wasn’t. You’ll certainly not understand all of it, but it’s interesting stuff.

May 18, 2017 Posted by | Astronomy, Lectures, Physics | Leave a comment

Random stuff

It’s been a long time since I last posted one of these posts, so a great number of links of interest has accumulated in my bookmarks. I intended to include a large number of these in this post and this of course means that I surely won’t cover each specific link included in this post in anywhere near the amount of detail it deserves, but that can’t be helped.

i. Autism Spectrum Disorder Grown Up: A Chart Review of Adult Functioning.

“For those diagnosed with ASD in childhood, most will become adults with a significant degree of disability […] Seltzer et al […] concluded that, despite considerable heterogeneity in social outcomes, “few adults with autism live independently, marry, go to college, work in competitive jobs or develop a large network of friends”. However, the trend within individuals is for some functional improvement over time, as well as a decrease in autistic symptoms […]. Some authors suggest that a sub-group of 15–30% of adults with autism will show more positive outcomes […]. Howlin et al. (2004), and Cederlund et al. (2008) assigned global ratings of social functioning based on achieving independence, friendships/a steady relationship, and education and/or a job. These two papers described respectively 22% and 27% of groups of higher functioning (IQ above 70) ASD adults as attaining “Very Good” or “Good” outcomes.”

“[W]e evaluated the adult outcomes for 45 individuals diagnosed with ASD prior to age 18, and compared this with the functioning of 35 patients whose ASD was identified after 18 years. Concurrent mental illnesses were noted for both groups. […] Comparison of adult outcome within the group of subjects diagnosed with ASD prior to 18 years of age showed significantly poorer functioning for those with co-morbid Intellectual Disability, except in the domain of establishing intimate relationships [my emphasis. To make this point completely clear, one way to look at these results is that apparently in the domain of partner-search autistics diagnosed during childhood are doing so badly in general that being intellectually disabled on top of being autistic is apparently conferring no additional disadvantage]. Even in the normal IQ group, the mean total score, i.e. the sum of the 5 domains, was relatively low at 12.1 out of a possible 25. […] Those diagnosed as adults had achieved significantly more in the domains of education and independence […] Some authors have described a subgroup of 15–27% of adult ASD patients who attained more positive outcomes […]. Defining an arbitrary adaptive score of 20/25 as “Good” for our normal IQ patients, 8 of thirty four (25%) of those diagnosed as adults achieved this level. Only 5 of the thirty three (15%) diagnosed in childhood made the cutoff. (The cut off was consistent with a well, but not superlatively, functioning member of society […]). None of the Intellectually Disabled ASD subjects scored above 10. […] All three groups had a high rate of co-morbid psychiatric illnesses. Depression was particularly frequent in those diagnosed as adults, consistent with other reports […]. Anxiety disorders were also prevalent in the higher functioning participants, 25–27%. […] Most of the higher functioning ASD individuals, whether diagnosed before or after 18 years of age, were functioning well below the potential implied by their normal range intellect.”

Related papers: Social Outcomes in Mid- to Later Adulthood Among Individuals Diagnosed With Autism and Average Nonverbal IQ as Children, Adults With Autism Spectrum Disorders.

ii. Premature mortality in autism spectrum disorder. This is a Swedish matched case cohort study. Some observations from the paper:

“The aim of the current study was to analyse all-cause and cause-specific mortality in ASD using nationwide Swedish population-based registers. A further aim was to address the role of intellectual disability and gender as possible moderators of mortality and causes of death in ASD. […] Odds ratios (ORs) were calculated for a population-based cohort of ASD probands (n = 27 122, diagnosed between 1987 and 2009) compared with gender-, age- and county of residence-matched controls (n = 2 672 185). […] During the observed period, 24 358 (0.91%) individuals in the general population died, whereas the corresponding figure for individuals with ASD was 706 (2.60%; OR = 2.56; 95% CI 2.38–2.76). Cause-specific analyses showed elevated mortality in ASD for almost all analysed diagnostic categories. Mortality and patterns for cause-specific mortality were partly moderated by gender and general intellectual ability. […] Premature mortality was markedly increased in ASD owing to a multitude of medical conditions. […] Mortality was significantly elevated in both genders relative to the general population (males: OR = 2.87; females OR = 2.24)”.

“Individuals in the control group died at a mean age of 70.20 years (s.d. = 24.16, median = 80), whereas the corresponding figure for the entire ASD group was 53.87 years (s.d. = 24.78, median = 55), for low-functioning ASD 39.50 years (s.d. = 21.55, median = 40) and high-functioning ASD 58.39 years (s.d. = 24.01, median = 63) respectively. […] Significantly elevated mortality was noted among individuals with ASD in all analysed categories of specific causes of death except for infections […] ORs were highest in cases of mortality because of diseases of the nervous system (OR = 7.49) and because of suicide (OR = 7.55), in comparison with matched general population controls.”

iii. Adhesive capsulitis of shoulder. This one is related to a health scare I had a few months ago. A few quotes:

Adhesive capsulitis (also known as frozen shoulder) is a painful and disabling disorder of unclear cause in which the shoulder capsule, the connective tissue surrounding the glenohumeral joint of the shoulder, becomes inflamed and stiff, greatly restricting motion and causing chronic pain. Pain is usually constant, worse at night, and with cold weather. Certain movements or bumps can provoke episodes of tremendous pain and cramping. […] People who suffer from adhesive capsulitis usually experience severe pain and sleep deprivation for prolonged periods due to pain that gets worse when lying still and restricted movement/positions. The condition can lead to depression, problems in the neck and back, and severe weight loss due to long-term lack of deep sleep. People who suffer from adhesive capsulitis may have extreme difficulty concentrating, working, or performing daily life activities for extended periods of time.”

Some other related links below:

The prevalence of a diabetic condition and adhesive capsulitis of the shoulder.
“Adhesive capsulitis is characterized by a progressive and painful loss of shoulder motion of unknown etiology. Previous studies have found the prevalence of adhesive capsulitis to be slightly greater than 2% in the general population. However, the relationship between adhesive capsulitis and diabetes mellitus (DM) is well documented, with the incidence of adhesive capsulitis being two to four times higher in diabetics than in the general population. It affects about 20% of people with diabetes and has been described as the most disabling of the common musculoskeletal manifestations of diabetes.”

Adhesive Capsulitis (review article).
“Patients with type I diabetes have a 40% chance of developing a frozen shoulder in their lifetimes […] Dominant arm involvement has been shown to have a good prognosis; associated intrinsic pathology or insulin-dependent diabetes of more than 10 years are poor prognostic indicators.15 Three stages of adhesive capsulitis have been described, with each phase lasting for about 6 months. The first stage is the freezing stage in which there is an insidious onset of pain. At the end of this period, shoulder ROM [range of motion] becomes limited. The second stage is the frozen stage, in which there might be a reduction in pain; however, there is still restricted ROM. The third stage is the thawing stage, in which ROM improves, but can take between 12 and 42 months to do so. Most patients regain a full ROM; however, 10% to 15% of patients suffer from continued pain and limited ROM.”

Musculoskeletal Complications in Type 1 Diabetes.
“The development of periarticular thickening of skin on the hands and limited joint mobility (cheiroarthropathy) is associated with diabetes and can lead to significant disability. The objective of this study was to describe the prevalence of cheiroarthropathy in the well-characterized Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort and examine associated risk factors […] This cross-sectional analysis was performed in 1,217 participants (95% of the active cohort) in EDIC years 18/19 after an average of 24 years of follow-up. Cheiroarthropathy — defined as the presence of any one of the following: adhesive capsulitis, carpal tunnel syndrome, flexor tenosynovitis, Dupuytren’s contracture, or a positive prayer sign [related link] — was assessed using a targeted medical history and standardized physical examination. […] Cheiroarthropathy was present in 66% of subjects […] Cheiroarthropathy is common in people with type 1 diabetes of long duration (∼30 years) and is related to longer duration and higher levels of glycemia. Clinicians should include cheiroarthropathy in their routine history and physical examination of patients with type 1 diabetes because it causes clinically significant functional disability.”

Musculoskeletal disorders in diabetes mellitus: an update.
“Diabetes mellitus (DM) is associated with several musculoskeletal disorders. […] The exact pathophysiology of most of these musculoskeletal disorders remains obscure. Connective tissue disorders, neuropathy, vasculopathy or combinations of these problems, may underlie the increased incidence of musculoskeletal disorders in DM. The development of musculoskeletal disorders is dependent on age and on the duration of DM; however, it has been difficult to show a direct correlation with the metabolic control of DM.”

Rheumatic Manifestations of Diabetes Mellitus.

Prevalence of symptoms and signs of shoulder problems in people with diabetes mellitus.

Musculoskeletal Disorders of the Hand and Shoulder in Patients with Diabetes.
“In addition to micro- and macroangiopathic complications, diabetes mellitus is also associated with several musculoskeletal disorders of the hand and shoulder that can be debilitating (1,2). Limited joint mobility, also termed diabetic hand syndrome or cheiropathy (3), is characterized by skin thickening over the dorsum of the hands and restricted mobility of multiple joints. While this syndrome is painless and usually not disabling (2,4), other musculoskeletal problems occur with increased frequency in diabetic patients, including Dupuytren’s disease [“Dupuytren’s disease […] may be observed in up to 42% of adults with diabetes mellitus, typically in patients with long-standing T1D” – link], carpal tunnel syndrome [“The prevalence of [carpal tunnel syndrome, CTS] in patients with diabetes has been estimated at 11–30 % […], and is dependent on the duration of diabetes. […] Type I DM patients have a high prevalence of CTS with increasing duration of disease, up to 85 % after 54 years of DM” – link], palmar flexor tenosynovitis or trigger finger [“The incidence of trigger finger [/stenosing tenosynovitis] is 7–20 % of patients with diabetes comparing to only about 1–2 % in nondiabetic patients” – link], and adhesive capsulitis of the shoulder (5–10). The association of adhesive capsulitis with pain, swelling, dystrophic skin, and vasomotor instability of the hand constitutes the “shoulder-hand syndrome,” a rare but potentially disabling manifestation of diabetes (1,2).”

“The prevalence of musculoskeletal disorders was greater in diabetic patients than in control patients (36% vs. 9%, P < 0.01). Adhesive capsulitis was present in 12% of the diabetic patients and none of the control patients (P < 0.01), Dupuytren’s disease in 16% of diabetic and 3% of control patients (P < 0.01), and flexor tenosynovitis in 12% of diabetic and 2% of control patients (P < 0.04), while carpal tunnel syndrome occurred in 12% of diabetic patients and 8% of control patients (P = 0.29). Musculoskeletal disorders were more common in patients with type 1 diabetes than in those with type 2 diabetes […]. Forty-three patients [out of 100] with type 1 diabetes had either hand or shoulder disorders (37 with hand disorders, 6 with adhesive capsulitis of the shoulder, and 10 with both syndromes), compared with 28 patients [again out of 100] with type 2 diabetes (24 with hand disorders, 4 with adhesive capsulitis of the shoulder, and 3 with both syndromes, P = 0.03).”

Association of Diabetes Mellitus With the Risk of Developing Adhesive Capsulitis of the Shoulder: A Longitudinal Population-Based Followup Study.
“A total of 78,827 subjects with at least 2 ambulatory care visits with a principal diagnosis of DM in 2001 were recruited for the DM group. The non-DM group comprised 236,481 age- and sex-matched randomly sampled subjects without DM. […] During a 3-year followup period, 946 subjects (1.20%) in the DM group and 2,254 subjects (0.95%) in the non-DM group developed ACS. The crude HR of developing ACS for the DM group compared to the non-DM group was 1.333 […] the association between DM and ACS may be explained at least in part by a DM-related chronic inflammatory process with increased growth factor expression, which in turn leads to joint synovitis and subsequent capsular fibrosis.”

It is important to note when interpreting the results of the above paper that these results are based on Taiwanese population-level data, and type 1 diabetes – which is obviously the high-risk diabetes subgroup in this particular context – is rare in East Asian populations (as observed in Sperling et al., “A child in Helsinki, Finland is almost 400 times more likely to develop diabetes than a child in Sichuan, China”. Taiwanese incidence of type 1 DM in children is estimated at ~5 in 100.000).

iv. Parents who let diabetic son starve to death found guilty of first-degree murder. It’s been a while since I last saw one of these ‘boost-your-faith-in-humanity’-cases, but they in my impression do pop up every now and then. I should probably keep at hand one of these articles in case my parents ever express worry to me that they weren’t good parents; they could have done a lot worse…

v. Freedom of medicine. One quote from the conclusion of Cochran’s post:

“[I]t is surely possible to materially improve the efficacy of drug development, of medical research as a whole. We’re doing better than we did 500 years ago – although probably worse than we did 50 years ago. But I would approach it by learning as much as possible about medical history, demographics, epidemiology, evolutionary medicine, theory of senescence, genetics, etc. Read Koch, not Hayek. There is no royal road to medical progress.”

I agree, and I was considering including some related comments and observations about health economics in this post – however I ultimately decided against doing that in part because the post was growing unwieldy; I might include those observations in another post later on. Here’s another somewhat older Westhunt post I at some point decided to bookmark – I in particular like the following neat quote from the comments, which expresses a view I have of course expressed myself in the past here on this blog:

“When you think about it, falsehoods, stupid crap, make the best group identifiers, because anyone might agree with you when you’re obviously right. Signing up to clear nonsense is a better test of group loyalty. A true friend is with you when you’re wrong. Ideally, not just wrong, but barking mad, rolling around in your own vomit wrong.”

vi. Economic Costs of Diabetes in the U.S. in 2012.

“Approximately 59% of all health care expenditures attributed to diabetes are for health resources used by the population aged 65 years and older, much of which is borne by the Medicare program […]. The population 45–64 years of age incurs 33% of diabetes-attributed costs, with the remaining 8% incurred by the population under 45 years of age. The annual attributed health care cost per person with diabetes […] increases with age, primarily as a result of increased use of hospital inpatient and nursing facility resources, physician office visits, and prescription medications. Dividing the total attributed health care expenditures by the number of people with diabetes, we estimate the average annual excess expenditures for the population aged under 45 years, 45–64 years, and 65 years and above, respectively, at $4,394, $5,611, and $11,825.”

“Our logistic regression analysis with NHIS data suggests that diabetes is associated with a 2.4 percentage point increase in the likelihood of leaving the workforce for disability. This equates to approximately 541,000 working-age adults leaving the workforce prematurely and 130 million lost workdays in 2012. For the population that leaves the workforce early because of diabetes-associated disability, we estimate that their average daily earnings would have been $166 per person (with the amount varying by demographic). Presenteeism accounted for 30% of the indirect cost of diabetes. The estimate of a 6.6% annual decline in productivity attributed to diabetes (in excess of the estimated decline in the absence of diabetes) equates to 113 million lost workdays per year.”

vii. Total red meat intake of ≥0.5 servings/d does not negatively influence cardiovascular disease risk factors: a systemically searched meta-analysis of randomized controlled trials.

viii. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. Did I blog this paper at some point in the past? I could not find any coverage of it on the blog when I searched for it so I decided to include it here, even if I have a nagging suspicion I may have talked about these findings before. What did they find? The short version is this:

“A modest reduction in salt intake for four or more weeks causes significant and, from a population viewpoint, important falls in blood pressure in both hypertensive and normotensive individuals, irrespective of sex and ethnic group. Salt reduction is associated with a small physiological increase in plasma renin activity, aldosterone, and noradrenaline and no significant change in lipid concentrations. These results support a reduction in population salt intake, which will lower population blood pressure and thereby reduce cardiovascular disease.”

ix. Some wikipedia links:

Heroic Age of Antarctic Exploration (featured).

Wien’s displacement law.

Kuiper belt (featured).

Treason (one quote worth including here: “Currently, the consensus among major Islamic schools is that apostasy (leaving Islam) is considered treason and that the penalty is death; this is supported not in the Quran but in the Hadith.[42][43][44][45][46][47]“).

Lymphatic filariasis.

File:World map of countries by number of cigarettes smoked per adult per year.

Australian gold rushes.

Savant syndrome (“It is estimated that 10% of those with autism have some form of savant abilities”). A small sidenote of interest to Danish readers: The Danish Broadcasting Corporation recently featured a series about autistics with ‘special abilities’ – the show was called ‘The hidden talents’ (De skjulte talenter), and after multiple people had nagged me to watch it I ended up deciding to do so. Most of the people in that show presumably had some degree of ‘savantism’ combined with autism at the milder end of the spectrum, i.e. Asperger’s. I was somewhat conflicted about what to think about the show and did consider blogging it in detail (in Danish?), but I decided against it. However I do want to add here to Danish readers reading along who’ve seen the show that they would do well to repeatedly keep in mind that a) the great majority of autistics do not have abilities like these, b) many autistics with abilities like these presumably do quite poorly, and c) that many autistics have even greater social impairments than do people like e.g. (the very likeable, I have to add…) Louise Wille from the show).

Quark–gluon plasma.

Simo Häyhä.

Chernobyl liquidators.

Black Death (“Over 60% of Norway’s population died in 1348–1350”).

Renault FT (“among the most revolutionary and influential tank designs in history”).

Weierstrass function (“an example of a pathological real-valued function on the real line. The function has the property of being continuous everywhere but differentiable nowhere”).

W Ursae Majoris variable.

Void coefficient. (“a number that can be used to estimate how much the reactivity of a nuclear reactor changes as voids (typically steam bubbles) form in the reactor moderator or coolant. […] Reactivity is directly related to the tendency of the reactor core to change power level: if reactivity is positive, the core power tends to increase; if it is negative, the core power tends to decrease; if it is zero, the core power tends to remain stable. […] A positive void coefficient means that the reactivity increases as the void content inside the reactor increases due to increased boiling or loss of coolant; for example, if the coolant acts as a neutron absorber. If the void coefficient is large enough and control systems do not respond quickly enough, this can form a positive feedback loop which can quickly boil all the coolant in the reactor. This happened in the RBMK reactor that was destroyed in the Chernobyl disaster.”).

Gregor MacGregor (featured) (“a Scottish soldier, adventurer, and confidence trickster […] MacGregor’s Poyais scheme has been called one of the most brazen confidence tricks in history.”).


Irish Civil War.

March 10, 2017 Posted by | Astronomy, autism, Cardiology, Diabetes, Economics, Epidemiology, History, Infectious disease, Mathematics, Medicine, Papers, Physics, Psychology, Random stuff, Wikipedia | Leave a comment

Particle Physics



(Smbc, second one here. There were a lot of relevant ones to choose from – this one also seems ‘relevant’. And this one. And this one. This one? This one? This one? Maybe this one? In the end I decided to only include the two comics displayed above, but you should be aware of the others…)

The book is a bit dated, it was published before the LHC even started operations. But it’s a decent read. I can’t say I liked it as much as I liked the other books in the series which I recently covered, on galaxies and the laws of thermodynamics, mostly because this book was a bit more pop-science-y than those books, and so the level of coverage was at times a little bit disappointing compared to the level of coverage provided in the aforementioned books throughout their coverage – but that said the book is far from terrible, I learned a lot, and I can imagine the author faced a very difficult task.

Below I have added a few observations from the book and some links to articles about some key concepts and things mentioned/covered in the book.

“[T]oday we view the collisions between high-energy particles as a means of studying the phenomena that ruled when the universe was newly born. We can study how matter was created and discover what varieties there were. From this we can construct the story of how the material universe has developed from that original hot cauldron to the cool conditions here on Earth today, where matter is made from electrons, without need for muons and taus, and where the seeds of atomic nuclei are just the up and down quarks, without need for strange or charming stuff.

In very broad terms, this is the story of what has happened. The matter that was born in the hot Big Bang consisted of quarks and particles like the electron. As concerns the quarks, the strange, charm, bottom, and top varieties are highly unstable, and died out within a fraction of a second, the weak force converting them into their more stable progeny, the up and down varieties which survive within us today. A similar story took place for the electron and its heavier versions, the muon and tau. This latter pair are also unstable and died out, courtesy of the weak force, leaving the electron as survivor. In the process of these decays, lots of neutrinos and electromagnetic radiation were also produced, which continue to swarm throughout the universe some 14 billion years later.

The up and down quarks and the electrons were the survivors while the universe was still very young and hot. As it cooled, the quarks were stuck to one another, forming protons and neutrons. The mutual gravitational attraction among these particles gathered them into large clouds that were primaeval stars. As they bumped into one another in the heart of these stars, the protons and neutrons built up the seeds of heavier elements. Some stars became unstable and exploded, ejecting these atomic nuclei into space, where they trapped electrons to form atoms of matter as we know it. […] What we can now do in experiments is in effect reverse the process and observe matter change back into its original primaeval forms.”

“A fully grown human is a bit less than two metres tall. […] to set the scale I will take humans to be about 1 metre in ‘order of magnitude’ […yet another smbc comic springs to mind here] […] Then, going to the large scales of astronomy, we have the radius of the Earth, some 107 m […]; that of the Sun is 109 m; our orbit around the Sun is 1011 m […] note that the relative sizes of the Earth, Sun, and our orbit are factors of about 100. […] Whereas the atom is typically 10–10 m across, its central nucleus measures only about 10–14 to 10–15 m. So beware the oft-quoted analogy that atoms are like miniature solar systems with the ‘planetary electrons’ encircling the ‘nuclear sun’. The real solar system has a factor 1/100 between our orbit and the size of the central Sun; the atom is far emptier, with 1/10,000 as the corresponding ratio between the extent of its central nucleus and the radius of the atom. And this emptiness continues. Individual protons and neutrons are about 10–15 m in diameter […] the relative size of quark to proton is some 1/10,000 (at most!). The same is true for the ‘planetary’ electron relative to the proton ‘sun’: 1/10,000 rather than the ‘mere’ 1/100 of the real solar system. So the world within the atom is incredibly empty.”

“Our inability to see atoms has to do with the fact that light acts like a wave and waves do not scatter easily from small objects. To see a thing, the wavelength of the beam must be smaller than that thing is. Therefore, to see molecules or atoms needs illuminations whose wavelengths are similar to or smaller than them. Light waves, like those our eyes are sensitive to, have wavelength about 10–7 m […]. This is still a thousand times bigger than the size of an atom. […] To have any chance of seeing molecules and atoms we need light with wavelengths much shorter than these. [And so we move into the world of X-ray crystallography and particle accelerators] […] To probe deep within atoms we need a source of very short wavelength. […] the technique is to use the basic particles […], such as electrons and protons, and speed them in electric fields. The higher their speed, the greater their energy and momentum and the shorter their associated wavelength. So beams of high-energy particles can resolve things as small as atoms.”

“About 400 billion neutrinos from the Sun pass through each one of us each second.”

“For a century beams of particles have been used to reveal the inner structure of atoms. These have progressed from naturally occurring alpha and beta particles, courtesy of natural radioactivity, through cosmic rays to intense beams of electrons, protons, and other particles at modern accelerators. […] Different particles probe matter in complementary ways. It has been by combining the information from [the] various approaches that our present rich picture has emerged. […] It was the desire to replicate the cosmic rays under controlled conditions that led to modern high-energy physics at accelerators. […] Electrically charged particles are accelerated by electric forces. Apply enough electric force to an electron, say, and it will go faster and faster in a straight line […] Under the influence of a magnetic field, the path of a charged particle will curve. By using electric fields to speed them, and magnetic fields to bend their trajectory, we can steer particles round circles over and over again. This is the basic idea behind huge rings, such as the 27-km-long accelerator at CERN in Geneva. […] our ability to learn about the origins and nature of matter have depended upon advances on two fronts: the construction of ever more powerful accelerators, and the development of sophisticated means of recording the collisions.”

Particle physics.
Strong interaction.
Weak interaction (‘good article’).
Electron (featured).
Quark (featured).
Fundamental interactions.
Electromagnetic spectrum.
Cathode ray.
Alpha particle.
Cloud chamber.
Atomic spectroscopy.
Resonance (particle physics).
Spin (physics).
Beta decay.
Neutrino astronomy.
Particle accelerator/Cyclotron/Synchrotron/Linear particle accelerator.
Particle detector.
Cherenkov radiation.
Sudbury Neutrino Observatory.
Quantum chromodynamics.
Color charge.
Force carrier.
W and Z bosons.
Electroweak interaction (/theory).
Exotic matter.
Strange quark.
Charm (quantum number).
Inverse beta decay.
Dark matter.
Standard model.
Higgs boson.
Quark–gluon plasma.
CP violation.

February 9, 2017 Posted by | Books, Physics | Leave a comment

The Laws of Thermodynamics

Here’s a relevant 60 symbols video with Mike Merrifield. Below a few observations from the book, and some links.

“Among the hundreds of laws that describe the universe, there lurks a mighty handful. These are the laws of thermodynamics, which summarize the properties of energy and its transformation from one form to another. […] The mighty handful consists of four laws, with the numbering starting inconveniently at zero and ending at three. The first two laws (the ‘zeroth’ and the ‘first’) introduce two familiar but nevertheless enigmatic properties, the temperature and the energy. The third of the four (the ‘second law’) introduces what many take to be an even more elusive property, the entropy […] The second law is one of the all-time great laws of science […]. The fourth of the laws (the ‘third law’) has a more technical role, but rounds out the structure of the subject and both enables and foils its applications.”

Classical thermodynamics is the part of thermodynamics that emerged during the nineteenth century before everyone was fully convinced about the reality of atoms, and concerns relationships between bulk properties. You can do classical thermodynamics even if you don’t believe in atoms. Towards the end of the nineteenth century, when most scientists accepted that atoms were real and not just an accounting device, there emerged the version of thermodynamics called statistical thermodynamics, which sought to account for the bulk properties of matter in terms of its constituent atoms. The ‘statistical’ part of the name comes from the fact that in the discussion of bulk properties we don’t need to think about the behaviour of individual atoms but we do need to think about the average behaviour of myriad atoms. […] In short, whereas dynamics deals with the behaviour of individual bodies, thermodynamics deals with the average behaviour of vast numbers of them.”

“In everyday language, heat is both a noun and a verb. Heat flows; we heat. In thermodynamics heat is not an entity or even a form of energy: heat is a mode of transfer of energy. It is not a form of energy, or a fluid of some kind, or anything of any kind. Heat is the transfer of energy by virtue of a temperature difference. Heat is the name of a process, not the name of an entity.”

“The supply of 1J of energy as heat to 1 g of water results in an increase in temperature of about 0.2°C. Substances with a high heat capacity (water is an example) require a larger amount of heat to bring about a given rise in temperature than those with a small heat capacity (air is an example). In formal thermodynamics, the conditions under which heating takes place must be specified. For instance, if the heating takes place under conditions of constant pressure with the sample free to expand, then some of the energy supplied as heat goes into expanding the sample and therefore to doing work. Less energy remains in the sample, so its temperature rises less than when it is constrained to have a constant volume, and therefore we report that its heat capacity is higher. The difference between heat capacities of a system at constant volume and at constant pressure is of most practical significance for gases, which undergo large changes in volume as they are heated in vessels that are able to expand.”

“Heat capacities vary with temperature. An important experimental observation […] is that the heat capacity of every substance falls to zero when the temperature is reduced towards absolute zero (T = 0). A very small heat capacity implies that even a tiny transfer of heat to a system results in a significant rise in temperature, which is one of the problems associated with achieving very low temperatures when even a small leakage of heat into a sample can have a serious effect on the temperature”.

“A crude restatement of Clausius’s statement is that refrigerators don’t work unless you turn them on.”

“The Gibbs energy is of the greatest importance in chemistry and in the field of bioenergetics, the study of energy utilization in biology. Most processes in chemistry and biology occur at constant temperature and pressure, and so to decide whether they are spontaneous and able to produce non-expansion work we need to consider the Gibbs energy. […] Our bodies live off Gibbs energy. Many of the processes that constitute life are non-spontaneous reactions, which is why we decompose and putrefy when we die and these life-sustaining reactions no longer continue. […] In biology a very important ‘heavy weight’ reaction involves the molecule adenosine triphosphate (ATP). […] When a terminal phosphate group is snipped off by reaction with water […], to form adenosine diphosphate (ADP), there is a substantial decrease in Gibbs energy, arising in part from the increase in entropy when the group is liberated from the chain. Enzymes in the body make use of this change in Gibbs energy […] to bring about the linking of amino acids, and gradually build a protein molecule. It takes the effort of about three ATP molecules to link two amino acids together, so the construction of a typical protein of about 150 amino acid groups needs the energy released by about 450 ATP molecules. […] The ADP molecules, the husks of dead ATP molecules, are too valuable just to discard. They are converted back into ATP molecules by coupling to reactions that release even more Gibbs energy […] and which reattach a phosphate group to each one. These heavy-weight reactions are the reactions of metabolism of the food that we need to ingest regularly.”

Links of interest below – the stuff covered in the links is the sort of stuff covered in this book:

Laws of thermodynamics (article includes links to many other articles of interest, including links to each of the laws mentioned above).
System concepts.
Intensive and extensive properties.
Mechanical equilibrium.
Thermal equilibrium.
Diathermal wall.
Thermodynamic temperature.
Thermodynamic beta.
Ludwig Boltzmann.
Boltzmann constant.
Maxwell–Boltzmann distribution.
Conservation of energy.
Work (physics).
Internal energy.
Heat (physics).
Microscopic view of heat.
Reversible process (thermodynamics).
Carnot’s theorem.
Fluctuation-dissipation theorem.
Noether’s theorem.
Thermal efficiency.
Rudolf Clausius.
Spontaneous process.
Residual entropy.
Heat engine.
Coefficient of performance.
Helmholtz free energy.
Gibbs free energy.
Phase transition.
Chemical equilibrium.
Absolute zero.

February 5, 2017 Posted by | Books, Physics | Leave a comment


I have added some observations from the book below, as well as some links covering people/ideas/stuff discussed/mentioned in the book.

“On average, out of every 100 newly born star systems, 60 are binaries and 40 are triples. Solitary stars like the Sun are later ejected from triple systems formed in this way.”

“…any object will become a black hole if it is sufficiently compressed. For any mass, there is a critical radius, called the Schwarzschild radius, for which this occurs. For the Sun, the Schwarzschild radius is just under 3 km; for the Earth, it is just under 1 cm. In either case, if the entire mass of the object were squeezed within the appropriate Schwarzschild radius it would become a black hole.”

“It only became possible to study the centre of our Galaxy when radio telescopes and other instruments that do not rely on visible light became available. There is a great deal of dust in the plane of the Milky Way […] This blocks out visible light. But longer wavelengths penetrate the dust more easily. That is why sunsets are red – short wavelength (blue) light is scattered out of the line of sight by dust in the atmosphere, while the longer wavelength red light gets through to your eyes. So our understanding of the galactic centre is largely based on infrared and radio observations.”

“there is strong evidence that the Milky Way Galaxy is a completely ordinary disc galaxy, a typical representative of its class. Since that is the case, it means that we can confidently use our inside knowledge of the structure and evolution of our own Galaxy, based on close-up observations, to help our understanding of the origin and nature of disc galaxies in general. We do not occupy a special place in the Universe; but this was only finally established at the end of the 20th century. […] in the decades following Hubble’s first measurements of the cosmological distance scale, the Milky Way still seemed like a special place. Hubble’s calculation of the distance scale implied that other galaxies are relatively close to our Galaxy, and so they would not have to be very big to appear as large as they do on the sky; the Milky Way seemed to be by far the largest galaxy in the Universe. We now know that Hubble was wrong. […] the value he initially found for the Hubble Constant was about seven times bigger than the value accepted today. In other words, all the extragalactic distances Hubble inferred were seven times too small. But this was not realized overnight. The cosmological distance scale was only revised slowly, over many decades, as observations improved and one error after another was corrected. […] The importance of determining the cosmological distance scale accurately, more than half a century after Hubble’s pioneering work, was still so great that it was a primary justification for the existence of the Hubble Space Telescope (HST).”

“The key point to grasp […] is that the expansion described by [Einstein’s] equations is an expansion of space as time passes. The cosmological redshift is not a Doppler effect caused by galaxies moving outward through space, as if fleeing from the site of some great explosion, but occurs because the space between the galaxies is stretching. So the spaces between galaxies increase while light is on its way from one galaxy to another. This stretches the light waves to longer wavelengths, which means shifting them towards the red end of the spectrum. […] The second key point about the universal expansion is that it does not have a centre. There is nothing special about the fact that we observe galaxies receding with redshifts proportional to their distances from the Milky Way. […] whichever galaxy you happen to be sitting in, you will see the same thing – redshift proportional to distance.”

“The age of the Universe is determined by studying some of the largest things in the Universe, clusters of galaxies, and analysing their behaviour using the general theory of relativity. Our understanding of how stars work, from which we calculate their ages, comes from studying some of the smallest things in the Universe, the nuclei of atoms, and using the other great theory of 20th-century physics, quantum mechanics, to calculate how nuclei fuse with one another to release the energy that keeps stars shining. The fact that the two ages agree with one another, and that the ages of the oldest stars are just a little bit less than the age of the Universe, is one of the most compelling reasons to think that the whole of 20th-century physics works and provides a good description of the world around us, from the very small scale to the very large scale.”

“Planets are small objects orbiting a large central mass, and the gravity of the Sun dominates their motion. Because of this, the speed with which a planet moves […] is inversely proportional to the square of its distance from the centre of the Solar System. Jupiter is farther from the Sun than we are, so it moves more slowly in its orbit than the Earth, as well as having a larger orbit. But all the stars in the disc of a galaxy move at the same speed. Stars farther out from the centre still have bigger orbits, so they still take longer to complete one circuit of the galaxy. But they are all travelling at essentially the same orbital speed through space.”

“The importance of studying objects at great distances across the Universe is that when we look at an object that is, say, 10 billion light years away, we see it by light which left it 10 billion years ago. This is the ‘look back time’, and it means that telescopes are in a sense time machines, showing us what the Universe was like when it was younger. The light from a distant galaxy is old, in the sense that it has been a long time on its journey; but the galaxy we see using that light is a young galaxy. […] For distant objects, because light has taken a long time on its journey to us, the Universe has expanded significantly while the light was on its way. […] This raises problems defining exactly what you mean by the ‘present distance’ to a remote galaxy”

“Among the many advantages that photographic and electronic recording methods have over the human eye, the most fundamental is that the longer they look, the more they see. Human eyes essentially give us a real-time view of our surroundings, and allow us to see things – such as stars – that are brighter than a certain limit. If an object is too faint to see, once your eyes have adapted to the dark no amount of staring in its direction will make it visible. But the detectors attached to modern telescopes keep on adding up the light from faint sources as long as they are pointing at them. A longer exposure will reveal fainter objects than a short exposure does, as the photons (particles of light) from the source fall on the detector one by one and the total gradually grows.”

“Nobody can be quite sure where the supermassive black holes at the hearts of galaxies today came from, but it seems at least possible that […] merging of black holes left over from the first generation of stars [in the universe] began the process by which supermassive black holes, feeding off the matter surrounding them, formed. […] It seems very unlikely that supermassive black holes formed first and then galaxies grew around them; they must have formed together, in a process sometimes referred to as co-evolution, from the seeds provided by the original black holes of a few hundred solar masses and the raw materials of the dense clouds of baryons in the knots in the filamentary structure. […] About one in a hundred of the galaxies seen at low redshifts are actively involved in the late stages of mergers, but these processes take so little time, compared with the age of the Universe, that the statistics imply that about half of all the galaxies visible nearby are the result of mergers between similarly sized galaxies in the past seven or eight billion years. Disc galaxies like the Milky Way seem themselves to have been built up from smaller sub-units, starting out with the spheroid and adding bits and pieces as time passed. […] there were many more small galaxies when the Universe was young than we see around us today. This is exactly what we would expect if many of the small galaxies have either grown larger through mergers or been swallowed up by larger galaxies.”

Links of interest:

Galaxy (‘featured article’).
Leonard Digges.
Thomas Wright.
William Herschel.
William Parsons.
The Great Debate.
Extinction (astronomy).
Henrietta Swan Leavitt (‘good article’).
Cepheid variable.
Ejnar Hertzsprung. (Before reading this book, I had no idea one of the people behind the famous Hertzsprung–Russell diagram was a Dane. I blame my physics teachers. I was probably told this by one of them, but if the guy in question had been a better teacher, I’d have listened, and I’d have known this.).
Globular cluster (‘featured article’).
Vesto Slipher.
Redshift (‘featured article’).
Refracting telescope/Reflecting telescope.
Disc galaxy.
Edwin Hubble.
Milton Humason.
Doppler effect.
Milky Way.
Orion Arm.
Stellar population.
Sagittarius A*.
Minkowski space.
General relativity (featured).
The Big Bang theory (featured).
Age of the universe.
Malmquist bias.
Type Ia supernova.
Dark energy.
Cosmic microwave background.
Cold dark matter.
Lambda-CDM model.
Lenticular galaxy.
Active galactic nucleus.
Hubble Ultra-Deep Field.
Stellar evolution.
Velocity dispersion.
Hawking radiation.
Ultimate fate of the universe.


February 5, 2017 Posted by | Astronomy, Books, cosmology, Physics | Leave a comment

Random stuff

i. Fire works a little differently than people imagine. A great ask-science comment. See also AugustusFink-nottle’s comment in the same thread.


iii. I was very conflicted about whether to link to this because I haven’t actually spent any time looking at it myself so I don’t know if it’s any good, but according to somebody (?) who linked to it on SSC the people behind this stuff have academic backgrounds in evolutionary biology, which is something at least (whether you think this is a good thing or not will probably depend greatly on your opinion of evolutionary biologists, but I’ve definitely learned a lot more about human mating patterns, partner interaction patterns, etc. from evolutionary biologists than I have from personal experience, so I’m probably in the ‘they-sometimes-have-interesting-ideas-about-these-topics-and-those-ideas-may-not-be-terrible’-camp). I figure these guys are much more application-oriented than were some of the previous sources I’ve read on related topics, such as e.g. Kappeler et al. I add the link mostly so that if I in five years time have a stroke that obliterates most of my decision-making skills, causing me to decide that entering the dating market might be a good idea, I’ll have some idea where it might make sense to start.

iv. Stereotype (In)Accuracy in Perceptions of Groups and Individuals.

“Are stereotypes accurate or inaccurate? We summarize evidence that stereotype accuracy is one of the largest and most replicable findings in social psychology. We address controversies in this literature, including the long-standing  and continuing but unjustified emphasis on stereotype inaccuracy, how to define and assess stereotype accuracy, and whether stereotypic (vs. individuating) information can be used rationally in person perception. We conclude with suggestions for building theory and for future directions of stereotype (in)accuracy research.”

A few quotes from the paper:

Demographic stereotypes are accurate. Research has consistently shown moderate to high levels of correspondence accuracy for demographic (e.g., race/ethnicity, gender) stereotypes […]. Nearly all accuracy correlations for consensual stereotypes about race/ethnicity and  gender exceed .50 (compared to only 5% of social psychological findings; Richard, Bond, & Stokes-Zoota, 2003).[…] Rather than being based in cultural myths, the shared component of stereotypes is often highly accurate. This pattern cannot be easily explained by motivational or social-constructionist theories of stereotypes and probably reflects a “wisdom of crowds” effect […] personal stereotypes are also quite accurate, with correspondence accuracy for roughly half exceeding r =.50.”

“We found 34 published studies of racial-, ethnic-, and gender-stereotype accuracy. Although not every study examined discrepancy scores, when they did, a plurality or majority of all consensual stereotype judgments were accurate. […] In these 34 studies, when stereotypes were inaccurate, there was more evidence of underestimating than overestimating actual demographic group differences […] Research assessing the accuracy of  miscellaneous other stereotypes (e.g., about occupations, college majors, sororities, etc.) has generally found accuracy levels comparable to those for demographic stereotypes”

“A common claim […] is that even though many stereotypes accurately capture group means, they are still not accurate because group means cannot describe every individual group member. […] If people were rational, they would use stereotypes to judge individual targets when they lack information about targets’ unique personal characteristics (i.e., individuating information), when the stereotype itself is highly diagnostic (i.e., highly informative regarding the judgment), and when available individuating information is ambiguous or incompletely useful. People’s judgments robustly conform to rational predictions. In the rare situations in which a stereotype is highly diagnostic, people rely on it (e.g., Crawford, Jussim, Madon, Cain, & Stevens, 2011). When highly diagnostic individuating information is available, people overwhelmingly rely on it (Kunda & Thagard, 1996; effect size averaging r = .70). Stereotype biases average no higher than r = .10 ( Jussim, 2012) but reach r = .25 in the absence of individuating information (Kunda & Thagard, 1996). The more diagnostic individuating information  people have, the less they stereotype (Crawford et al., 2011; Krueger & Rothbart, 1988). Thus, people do not indiscriminately apply their stereotypes to all individual  members of stereotyped groups.” (Funder incidentally talked about this stuff as well in his book Personality Judgment).

One thing worth mentioning in the context of stereotypes is that if you look at stuff like crime data – which sadly not many people do – and you stratify based on stuff like country of origin, then the sub-group differences you observe tend to be very large. Some of the differences you observe between subgroups are not in the order of something like 10%, which is probably the sort of difference which could easily be ignored without major consequences; some subgroup differences can easily be in the order of one or two orders of magnitude. The differences are in some contexts so large as to basically make it downright idiotic to assume there are no differences – it doesn’t make sense, it’s frankly a stupid thing to do. To give an example, in Germany the probability that a random person, about whom you know nothing, has been a suspect in a thievery case is 22% if that random person happens to be of Algerian extraction, whereas it’s only 0,27% if you’re dealing with an immigrant from China. Roughly one in 13 of those Algerians have also been involved in a case of ‘body (bodily?) harm’, which is the case for less than one in 400 of the Chinese immigrants.

v. Assessing Immigrant Integration in Sweden after the May 2013 Riots. Some data from the article:

“Today, about one-fifth of Sweden’s population has an immigrant background, defined as those who were either born abroad or born in Sweden to two immigrant parents. The foreign born comprised 15.4 percent of the Swedish population in 2012, up from 11.3 percent in 2000 and 9.2 percent in 1990 […] Of the estimated 331,975 asylum applicants registered in EU countries in 2012, 43,865 (or 13 percent) were in Sweden. […] More than half of these applications were from Syrians, Somalis, Afghanis, Serbians, and Eritreans. […] One town of about 80,000 people, Södertälje, since the mid-2000s has taken in more Iraqi refugees than the United States and Canada combined.”

“Coupled with […] macroeconomic changes, the largely humanitarian nature of immigrant arrivals since the 1970s has posed challenges of labor market integration for Sweden, as refugees often arrive with low levels of education and transferable skills […] high unemployment rates have disproportionately affected immigrant communities in Sweden. In 2009-10, Sweden had the highest gap between native and immigrant employment rates among OECD countries. Approximately 63 percent of immigrants were employed compared to 76 percent of the native-born population. This 13 percentage-point gap is significantly greater than the OECD average […] Explanations for the gap include less work experience and domestic formal qualifications such as language skills among immigrants […] Among recent immigrants, defined as those who have been in the country for less than five years, the employment rate differed from that of the native born by more than 27 percentage points. In 2011, the Swedish newspaper Dagens Nyheter reported that 35 percent of the unemployed registered at the Swedish Public Employment Service were foreign born, up from 22 percent in 2005.”

“As immigrant populations have grown, Sweden has experienced a persistent level of segregation — among the highest in Western Europe. In 2008, 60 percent of native Swedes lived in areas where the majority of the population was also Swedish, and 20 percent lived in areas that were virtually 100 percent Swedish. In contrast, 20 percent of Sweden’s foreign born lived in areas where more than 40 percent of the population was also foreign born.”

vi. Book recommendations. Or rather, author recommendations. A while back I asked ‘the people of SSC’ if they knew of any fiction authors I hadn’t read yet which were both funny and easy to read. I got a lot of good suggestions, and the roughly 20 Dick Francis novels I’ve read during the fall I’ve read as a consequence of that thread.

vii. On the genetic structure of Denmark.

viii. Religious Fundamentalism and Hostility against Out-groups: A Comparison of Muslims and Christians in Western Europe.

“On the basis of an original survey among native Christians and Muslims of Turkish and Moroccan origin in Germany, France, the Netherlands, Belgium, Austria and Sweden, this paper investigates four research questions comparing native Christians to Muslim immigrants: (1) the extent of religious fundamentalism; (2) its socio-economic determinants; (3) whether it can be distinguished from other indicators of religiosity; and (4) its relationship to hostility towards out-groups (homosexuals, Jews, the West, and Muslims). The results indicate that religious fundamentalist attitudes are much more widespread among Sunnite Muslims than among native Christians, even after controlling for the different demographic and socio-economic compositions of these groups. […] Fundamentalist believers […] show very high levels of out-group hostility, especially among Muslims.”

ix. Portal: Dinosaurs. It would have been so incredibly awesome to have had access to this kind of stuff back when I was a child. The portal includes links to articles with names like ‘Bone Wars‘ – what’s not to like? Again, awesome!

x. “you can’t determine if something is truly random from observations alone. You can only determine if something is not truly random.” (link) An important insight well expressed.

xi. Chessprogramming. If you’re interested in having a look at how chess programs work, this is a neat resource. The wiki contains lots of links with information on specific sub-topics of interest. Also chess-related: The World Championship match between Carlsen and Karjakin has started. To the extent that I’ll be following the live coverage, I’ll be following Svidler et al.’s coverage on chess24. Robin van Kampen and Eric Hansen – both 2600+ elo GMs – did quite well yesterday, in my opinion.

xii. Justified by More Than Logos Alone (Razib Khan).

“Very few are Roman Catholic because they have read Aquinas’ Five Ways. Rather, they are Roman Catholic, in order of necessity, because God aligns with their deep intuitions, basic cognitive needs in terms of cosmological coherency, and because the church serves as an avenue for socialization and repetitive ritual which binds individuals to the greater whole. People do not believe in Catholicism as often as they are born Catholics, and the Catholic religion is rather well fitted to a range of predispositions to the typical human.”

November 12, 2016 Posted by | Books, Chemistry, Chess, Data, dating, Demographics, Genetics, Geography, immigration, Paleontology, Papers, Physics, Psychology, Random stuff, Religion | Leave a comment

Random Stuff

i. On the youtube channel of the Institute for Advanced Studies there has been a lot of activity over the last week or two (far more than 100 new lectures have been uploaded, and it seems new uploads are still being added at this point), and I’ve been watching a few of the recently uploaded astrophysics lectures. They’re quite technical, but you can watch them and follow enough of the content to have an enjoyable time despite not understanding everything:

This is a good lecture, very interesting. One major point made early on: “the take-away message is that the most common planet in the galaxy, at least at shorter periods, are planets for which there is no analogue in the solar system. The most common kind of planet in the galaxy is a planet with a radius of two Earth radii.” Another big take-away message is that small planets seem to be quite common (as noted in the conclusions, “16% of Sun-like stars have an Earth-sized planet”).

Of the lectures included in this post this was the one I liked the least; there are too many (‘obstructive’) questions/interactions between lecturer and attendants along the way, and the interactions/questions are difficult to hear/understand. If you consider watching both this lecture and the lecture below, I would say that it would probably be wise to watch the lecture below this one before you watch this one; I concluded that in retrospect some of the observations made early on in the lecture below would have been useful to know about before watching this lecture. (The first half of the lecture below was incidentally to me somewhat easier to follow than was the second half, but especially the first half hour of it is really quite good, despite the bad start (which one can always blame on Microsoft…)).

ii. Words I’ve encountered recently (…or ‘recently’ – it’s been a while since I last posted one of these lists): Divagationsperiphrasis, reedy, architravesettpedipalp, tout, togs, edentulous, moue, tatty, tearaway, prorogue, piscine, fillip, sop, panniers, auxology, roister, prepossessing, cantle, catamite, couth, ordure, biddy, recrudescence, parvenu, scupper, husting, hackle, expatiate, affray, tatterdemalion, eructation, coppice, dekko, scull, fulmination, pollarding, grotty, secateurs, bumf (I must admit that I like this word – it seems fitting, somehow, to use that word for this concept…), durophagy, randy, (brief note to self: Advise people having children who ask me about suggestions for how to name them against using this name (or variants such as Randi), it does not seem like a great idea), effete, apricity, sororal, bint, coition, abaft, eaves, gadabout, lugubriously, retroussé, landlubber, deliquescence, antimacassar, inanition.

iii. “The point of rigour is not to destroy all intuition; instead, it should be used to destroy bad intuition while clarifying and elevating good intuition. It is only with a combination of both rigorous formalism and good intuition that one can tackle complex mathematical problems; one needs the former to correctly deal with the fine details, and the latter to correctly deal with the big picture. Without one or the other, you will spend a lot of time blundering around in the dark (which can be instructive, but is highly inefficient). So once you are fully comfortable with rigorous mathematical thinking, you should revisit your intuitions on the subject and use your new thinking skills to test and refine these intuitions rather than discard them. One way to do this is to ask yourself dumb questions; another is to relearn your field.” (Terry Tao, There’s more to mathematics than rigour and proofs)

iv. A century of trends in adult human height. A figure from the paper (Figure 3 – Change in adult height between the 1896 and 1996 birth cohorts):


(Click to view full size. WordPress seems to have changed the way you add images to a blog post – if this one is even so annoyingly large, I apologize, I have tried to minimize it while still retaining detail, but the original file is huge). An observation from the paper:

“Men were taller than women in every country, on average by ~11 cm in the 1896 birth cohort and ~12 cm in the 1996 birth cohort […]. In the 1896 birth cohort, the male-female height gap in countries where average height was low was slightly larger than in taller nations. In other words, at the turn of the 20th century, men seem to have had a relative advantage over women in undernourished compared to better-nourished populations.”

I haven’t studied the paper in any detail but intend to do so at a later point in time.

v. I found this paper, on Exercise and Glucose Metabolism in Persons with Diabetes Mellitus, interesting in part because I’ve been very surprised a few times by offhand online statements made by diabetic athletes, who had observed that their blood glucose really didn’t drop all that fast during exercise. Rapid and annoyingly large drops in blood glucose during exercise have been a really consistent feature of my own life with diabetes during adulthood. It seems that there may be big inter-individual differences in terms of the effects of exercise on glucose in diabetics. From the paper:

“Typically, prolonged moderate-intensity aerobic exercise (i.e., 30–70% of one’s VO2max) causes a reduction in glucose concentrations because of a failure in circulating insulin levels to decrease at the onset of exercise.12 During this type of physical activity, glucose utilization may be as high as 1.5 g/min in adolescents with type 1 diabetes13 and exceed 2.0 g/min in adults with type 1 diabetes,14 an amount that quickly lowers circulating glucose levels. Persons with type 1 diabetes have large interindividual differences in blood glucose responses to exercise, although some intraindividual reproducibility exists.15 The wide ranging glycemic responses among individuals appears to be related to differences in pre-exercise blood glucose concentrations, the level of circulating counterregulatory hormones and the type/duration of the activity.2

August 13, 2016 Posted by | Astronomy, Demographics, Diabetes, language, Lectures, Mathematics, Physics, Random stuff | Leave a comment

Einstein quotes

“Einstein emerges from this collection of quotes, drawn from many different sources, as a complete and fully rounded human being […] Knowledge of the darker side of Einstein’s life makes his achievement in science and in public affairs even more miraculous. This book shows him as he was – not a superhuman genius but a human genius, and all the greater for being human.”

I’ve recently read The Ultimate Quotable Einstein, from the foreword of which the above quote is taken, which contains roughly 1600 quotes by or about Albert Einstein; most of the quotes are by Einstein himself, but the book also includes more than 50 pages towards the end of the book containing quotes by others about him. I was probably not in the main target group, but I do like good quote collections and I figured there might be enough good quotes in the book for it to make sense for me to give it a try. On the other hand after having read the foreword by Freeman Dyson I knew there would probably be a lot of quotes in the book which I probably wouldn’t find too interesting; I’m not really sure why I should give a crap if/why a guy who died more than 60 years ago and whom I have never met and never will was having an affair during the early 1920s, or why I should care what Einstein thought about his mother or his ex-wife, but if that kind of stuff interests you the book has stuff about those kinds of things as well. My own interest in Einstein, such as it is, is mainly in ‘Einstein the scientist’ (and perhaps also in this particular context ‘Einstein the aphorist’), not ‘Einstein the father’ or ‘Einstein the husband’. I also don’t find the political views which he held to be very interesting, but again if you want to know what Einstein thought about things like Zionism, pacifism, and world government the book includes quotes about such topics as well.

Overall I should say that I was a little underwhelmed by the book and the quotes it includes, but I would also note that people who are interested in knowing more about Einstein will likely find a lot of valuable source material here, and that I did give the book 3 stars on goodreads. I did learn a lot of new things about Einstein by reading the book, but this is not surprising given how little I knew about him before I started reading the book; for example I had no idea that he was offered the presidency of Israel a few years before his death. I noticed only two quotes which were included more than once (a quote on pages 187-188 was repeated on page 453, and a quote on page 295 was repeated on page 455), and although I cannot guarantee that there aren’t any other repeats almost all quotes included in the book are unique, in the sense that they’re only included once in the coverage. However it should also be mentioned in this context that there are a few quotes on specific themes which are very similar to other quotes included elsewhere in the coverage. I do consider this unavoidable considering the number of quotes included, though.

I have included some sample quotes from the book below – I have tried to include quotes on a wide variety of topics. All quotes without a source below are sourced quotes by Einstein (the book also contains a small collection of quotes ‘attributed to Einstein’, many of which are either not sourced or sourced in such a manner that Calaprice did not feel convinced that the quote was actually by Einstein – none of the quotes from that part of the book’s coverage are included below).

“When a blind beetle crawls over the surface of a curved branch, it doesn’t notice that the track it has covered is indeed curved. I was lucky enough to notice what the beetle didn’t notice.” (“in answer to his son Eduard’s question about why he is so famous, 1922.”)

“The most valuable thing a teacher can impart to children is not knowledge and understanding per se but a longing for knowledge and understanding” (see on a related note also Susan Engel’s book – US)

“Teaching should be such that what is offered is perceived as a valuable gift and not as a hard duty.”

“I am not prepared to accept all his conclusions, but I consider his work an immensely valuable contribution to the science of human behavior.” (Einstein said this about Sigmund Freud during an interview. Yeah…)

“I consider him the best of the living writers.” (on Bertrand Russell. Russell incidentally also admired Einstein immensely – the last part of the book, including quotes by others about Einstein, includes this one by him: “Of all the public figures that I have known, Einstein was the one who commanded my most wholehearted admiration.”)

“I cannot understand the passive response of the whole civilized world to this modern barbarism. Doesn’t the world see that Hitler is aiming for war?” (1933. Related link.)

“Children don’t heed the life experience of their parents, and nations ignore history. Bad lessons always have to be learned anew.”

“Few people are capable of expressing with equanimity opinions that differ from the prejudices of their social environment. Most people are even incapable of forming such opinions.”

“Sometimes one pays most for things one gets for nothing.”

“Thanks to my fortunate idea of introducing the relativity principle into physics, you (and others) now enormously overrate my scientific abilities, to the point where this makes me quite uncomfortable.” (To Arnold Sommerfeld, 1908)

“No fairer destiny could be allotted to any physical theory than that it should of itself point out the way to the introduction of a more comprehensive theory, in which it lives on as a limiting case.”

“Mother nature, or more precisely an experiment, is a resolute and seldom friendly referee […]. She never says “yes” to a theory; but only “maybe” under the best of circumstances, and in most cases simply “no”.”

“The aim of science is, on the one hand, a comprehension, as complete as possible, of the connection between the sense experiences in their totality, and, on the other hand, the accomplishment of this aim by the use of a minimum of primary concepts and relations.” A related quote from the book: “Although it is true that it is the goal of science to discover rules which permit the association and foretelling of facts, this is not its only aim. It also seeks to reduce the connections discovered to the smallest possible number of mutually independent conceptual elements. It is in this striving after the rational unification of the manifold that it encounters its greatest successes.”

“According to general relativity, the concept of space detached from any physical content does not exist. The physical reality of space is represented by a field whose components are continuous functions of four independent variables – the coordinates of space and time.”

“One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike – and yet it is the most precious thing we have.”

“”Why should I? Everybody knows me there” (upon being told by his wife to dress properly when going to the office). “Why should I? No one knows me there” (upon being told to dress properly for his first big conference).”

“Marriage is but slavery made to appear civilized.”

“Nothing is more destructive of respect for the government and the law of the land than passing laws that cannot be enforced.”

“Einstein would be one of the greatest theoretical physicists of all time even if he had not written a single line on relativity.” (Max Born)

“Einstein’s [violin] playing is excellent, but he does not deserve his world fame; there are many others just as good.” (“A music critic on an early 1920s performance, unaware that Einstein’s fame derived from physics, not music. Quoted in Reiser, Albert Einstein, 202-203″)

April 12, 2016 Posted by | Books, History, Physics, Quotes/aphorisms, Science | Leave a comment

A few lectures

Below are three new lectures from the Institute of Advanced Study. As far as I’ve gathered they’re all from an IAS symposium called ‘Lens of Computation on the Sciences’ – all three lecturers are computer scientists, but you don’t have to be a computer scientist to watch these lectures.

Should computer scientists and economists band together more and try to use the insights from one field to help solve problems in the other field? Roughgarden thinks so, and provides examples of how this might be done/has been done. Applications discussed in the lecture include traffic management and auction design. I’m not sure how much of this lecture is easy to follow for people who don’t know anything about either topic (i.e., computer science and economics), but I found it not too difficult to follow – it probably helped that I’ve actually done work on a few of the things he touches upon in the lecture, such as basic auction theory, the fixed point theorems and related proofs, basic queueing theory and basic discrete maths/graph theory. Either way there are certainly much more technical lectures than this one available at the IAS channel.

I don’t have Facebook and I’m not planning on ever getting a FB account, so I’m not really sure I care about the things this guy is trying to do, but the lecturer does touch upon some interesting topics in network theory. Not a great lecture in my opinion and occasionally I think the lecturer ‘drifts’ a bit, talking without saying very much, but it’s also not a terrible lecture. A few times I was really annoyed that you can’t see where he’s pointing that damn laser pointer, but this issue should not stop you from watching the video, especially not if you have an interest in analytical aspects of how to approach and make sense of ‘Big Data’.

I’ve noticed that Scott Alexander has said some nice things about Scott Aaronson a few times, but until now I’ve never actually read any of the latter guy’s stuff or watched any lectures by him. I agree with Scott (Alexander) that Scott (Aaronson) is definitely a smart guy. This is an interesting lecture; I won’t pretend I understood all of it, but it has some thought-provoking ideas and important points in the context of quantum computing and it’s actually a quite entertaining lecture; I was close to laughing a couple of times.

January 8, 2016 Posted by | Computer science, Economics, Game theory, Lectures, Mathematics, Physics | Leave a comment

Physically Speaking: A Dictionary of Quotations on Physics and Astronomy

Here’s my goodreads review of the book. As mentioned in the review, the book was overall a slightly disappointing read – but there were some decent quotes included in the book, and I decided that I ought to post a post with some sample quotes here as it would be a relatively easy post to write. Do note while reading this post that the book had a lot of bad quotes, so you should not take the sample quotes I’ve posted below to be representative of the book’s coverage in general.

i. “The aim of science is to seek the simplest explanation of complex facts. We are apt to fall into the error of thinking that the facts are simple because simplicity is the goal of our quest. The guiding motto in the life of every natural philosopher should be “Seek simplicity and distrust it.”” (Alfred North Whitehead)

ii. “Poor data and good reasoning give poor results. Good data and poor reasoning give poor results. Poor data and poor reasoning give rotten results.” (Edmund C. Berkeley)

iii. “By no process of sound reasoning can a conclusion drawn from limited data have more than a limited application.” (J.W. Mellor)

iv. “The energy produced by the breaking down of the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine.” (Ernest Rutherford, 1933).

v. “An experiment is a question which science poses to Nature, and a measurement is the recording of Nature’s answer.” (Max Planck)

vi. “A fact doesn’t have to be understood to be true.” (Heinlein)

vii. “God was invented to explain mystery. God is always invented to explain those things that you do not understand. Now, when you finally discover how something works, you get some laws which you’re taking away from God; you don’t need him anymore. But you need him for the other mysteries. So therefore you leave him to create the universe because we haven’t figured that out yet; you need him for understanding those things which you don’t believe the laws will explain, such as consciousness, or why you only live to a certain length of time – life and death – stuff like that. God is always associated with those things that you do not understand.” (Feynman)

viii. “Hypotheses are the scaffolds which are erected in front of a building and removed when the building is completed. They are indispensable to the worker; but he must not mistake the scaffolding for the building.” (Goethe)

ix. “We are to admit no more cause of natural things than such as are both true and sufficient to explain their appearances.” (Newton)

x. “It is the province of knowledge to speak and it is the privilege of wisdom to listen.” (Oliver Wendell Holmes)

xi. “Light crosses space with the prodigious velocity of 6,000 leagues per second.

La Science Populaire
April 28, 1881″

“A typographical error slipped into our last issue that is important to correct. The speed of light is 76,000 leagues per hour – and not 6,000.

La Science Populaire

May 19, 1881″

“A note correcting a first error appeared in our issue number 68, indicating that the speed of light is 76,000 leagues per hour. Our readers have corrected this new error. The speed of light is approximately 76,000 leagues per second.

La Science Populaire
June 16,1881″

xii. “All models are wrong but some are useful.” (G. E. P. Box)

xiii. “the downward movement of a mass of gold or lead, or of any other body endowed with weight, is quicker in proportion to its size.” (Aristotle)

xiv. “those whom devotion to abstract discussions has rendered unobservant of the facts are too ready to dogmatize on the basis of a few observations” (-ll-).

xv. “it may properly be asked whether science can be undertaken without taking the risk of skating on the possibly thin ice of supposition. The important thing to know is when one is on the more solid ground of observation and when one is on the ice.” (W. M. O’Neil)

xvi. “If I could remember the names of all these particles, I’d be a botanist.” (Enrico Fermi)

xvii. “Theoretical physicists are accustomed to living in a world which is removed from tangible objects by two levels of abstraction. From tangible atoms we move by one level of abstraction to invisible fields and particles. A second level of abstraction takes us from fields and particles to the symmetry-groups by which fields and particles are related. The superstring theory takes us beyond symmetry-groups to two further levels of abstraction. The third level of abstraction is the interpretation of symmetry-groups in terms of states in ten-dimensional space-time. The fourth level is the world of the superstrings by whose dynamical behavior the states are defined.” (Freeman Dyson)

xviii. “Space tells matter how to move . . . and matter tells space how to curve.” (John Wheeler)

xix. “the universe is not a rigid and inimitable edifice where independent matter is housed in independent space and time; it is an amorphous continuum, without any fixed architecture, plastic and variable, constantly subject to change and distortion. Wherever there is matter and motion, the continuum is disturbed. Just as a fish swimming in the sea agitates the water around it, so a star, a comet, or a galaxy distorts the geometry of the space-time through which it moves.” (Lincoln Barnett)

xx. “most physicists today place the probability of the existence of tachyons only slightly higher than the existence of unicorns” (Nick Herbert).

December 19, 2015 Posted by | Astronomy, Books, Physics, Quotes/aphorisms, Religion | Leave a comment

A few lectures

I was debating whether to post this, but considering how long it’s been since my last post I decided to do it. A large number of lectures have recently been uploaded by the Institute for Advanced Studies, and despite the fact that most of my ‘blogging-related activities’ these days relate to book reading I have watched a few of those lectures, and so I decided to post a couple of the lectures here:

I liked this lecture. Part II of the lecture in particular, starting around the 38 minute mark, dealt with stuff reasonably closely related to things I’d read about before (‘relatively’…) recently, back when I read Lammer’s text (blog coverage here); so although I didn’t remember the stuff covered in Lammer’s text in too much detail, it was definitely helpful to have worked with this stuff before. However I do believe you can watch the lecture and sort of understand what she’s talking about without knowing a great deal about these topics, at least if you don’t care too much about understanding all the details (I’d note that there are a lot of things going on ‘behind the scenes’ here, and that you can say a lot of stuff about topics closely related to this talk, like outgassing processes and how they relate to things like volcanism as well as e.g. the dynamic interactions between atmospheric molecules and the solar wind taking place in the early stages of stellar evolution). As is always the case for IAS lectures it’s really hard to hear the questions being asked and that’s annoying, but actually I think miss Schilchting is reasonably good at repeating the question or sort of answer them in a way that enables you to gather what’s ‘going on’; at least the fact that you can’t hear the questions is in my opinion a somewhat bigger problem in the lecture below (relatedly you can actually also see where the laser pointer is pointing in this lecture, at least some of the time – you can’t in the lecture below).

As mentioned this one was harder to follow, at least for me.

I hope to find time to blog a bit more in the days to come. One of several reasons why I’ve not blogged more than I have during the last weeks is that I recently realized that if I put in a bit of effort I’d be able to reach 150 books this year (I’m currently at 143 books, but very close to 144), with 50 non-fiction books (I think going for 52 would be a bit too much, but I’m not ruling it out yet – I’m currently at 47 non-fiction books (…but very close to 48)). I should note that I update the book post to which I link above much more often than I update ‘the blog’ in general with new posts. The reason why the ‘read 150 books this year goal’ is relevant is of course that every time I blog a book here on the blog, this takes away a substantial amount of time which I can’t spend actually reading books. Goodreads incidentally have recently made a nice ‘book of the year’ profile where you can see more details about the books I’ve read etc. From that profile I realized that my implicit working goal of reading 100 pages/day over the year has already been met (I’m currently at ~42.000 pages).

December 18, 2015 Posted by | Astronomy, Books, Lectures, Physics | Leave a comment