Wikipedia articles of interest
“Evidence suggests that an algal scum formed on the land 1,200 million years ago, but it was not until the Ordovician period, around 450 million years ago, that land plants appeared.”
The period before 450 million years ago of course covers more than 9/10ths of the history of the Earth.
“The early Devonian landscape was devoid of vegetation taller than waist height. Without the evolution of a robust vascular system, taller heights could not be attained. There was, however, a constant evolutionary pressure to attain greater height. The most obvious advantage is the harvesting of more sunlight for photosynthesis – by overshadowing competitors – but a further advantage is present in spore distribution, as spores (and, later, seeds) can be blown greater distances if they start higher.”
However plants didn’t stay short for long: “the late Devonian Archaeopteris, a precursor to gymnosperms which evolved from the trimerophytes, reached 30 m in height.”
Here’s what the Earth looked like back then (Wikipedia, link):
This is all part of why it’s so difficult to imagine what earth was like when you go millions of years back in time. We take so many things in our environment for granted. Grasses as we know them didn’t come about until somewhere around the K-T boundary.
“An acid-base reaction is a chemical reaction, that occurs between an acid and a base. Several concepts that provide alternative definitions for the reaction mechanisms involved and their application in solving related problems exist. Despite several differences in definitions, their importance becomes apparent as different methods of analysis when applied to acid-base reactions for gaseous or liquid species, or when acid or base character may be somewhat less apparent.”
There are quite a few different theories described in the article, I didn’t know that I didn’t know this. The article contains a brilliant example of a case where ‘everybody knew that this theory was true until it was proven wrong’:
“The first scientific concept of acids and bases was provided by Antoine Lavoisier circa 1776. Since Lavoisier’s knowledge of strong acids was mainly restricted to oxoacids, such as HNO3 (nitric acid) and H2SO4 (sulfuric acid), which tend to contain central atoms in high oxidation states surrounded by oxygen, and since he was not aware of the true composition of the hydrohalic acids (HF, HCl, HBr (hydrogen fluroide), and HI) (hydrogen iodide), he defined acids in terms of their containing oxygen, which in fact he named from Greek words meaning “acid-former” (from the Greek οξυς (oxys) meaning “acid” or “sharp” and γεινομαι (geinomai) meaning “engender”). The Lavoisier definition was held as absolute truth for over 30 years, until the 1810 article and subsequent lectures by Sir Humphry Davy in which he proved the lack of oxygen in H2S, H2Te, and the hydrohalic acids.”
3. Anglo-Zulu War. This article is part of the featured British Empire Portal, which contains quite a few articles I’ll probably have to read at some point. As written in the introduction to the portal: “By 1921, the British Empire held sway over a population of about 458 million people, approximately one-quarter of the world’s population. It covered about 36.6 million km² (14.2 million square miles), about a quarter of Earth’s total land area.” If you want to understand the world of 100 years ago, or the world some time before that, you really can’t ignore the history of the British Empire.
4. Medieval technology. Mostly links, but there are lots of them, and I’d guess there are quite a few good articles hidden here. Did you know that functional buttons – buttons with buttonholes for fastening or closing clothes – wasn’t invented until the 13th century?