Scottish Botanist Robert Brown goes to Australia

It is hard to quantify the Scottish botanist Robert Brown’s contributions to botany and physics in a short essay, but he was the first British botanist to support and advocate the natural system of classification. In 1801, Brown went to Australia, landing at King George’s Sound near Albany Western Australia, Australia, to work with Joseph Banks, who later appointed Brown his librarian and bequeathed his extensive botanical collection and library. Brown transferred them to the British Museum and consequently made the head of this new department.

While in Austalia, Brown discovered and named several Australian plant species, including Brown’s banksia (Banksia brownii) and Brown’s box (Eucalyptus brownii),. He also saw that the broad classification of “naked seeds” was far too wide-ranging, and had to be divided — since then it was been divided again and is now encompasses 4 categories. All of which is quite commendable, but doubtful that would we would even be reading about him if that was the case — it is a little too esoteric to matter to anyone beyond botanists.

What Brown saw in his microscope

But then thanks to his relentless desire to leave no stone unturned, and seek out every vagary Brown happened up, an odd thing under his microscope. What he discovered was the pollen grains were moving about haphazardly in the medium (water). Being a good scientist, he changed the size of the grains, the quantity of grains, finally putting an empty drop of liquid nearby to see what would happen.

What he saw was the grains hit each other in random ways, much like the breaking shot of billiards or the game of air hockey as shown above, and deduced other smaller “cells” as he termed it, are there for the bouncing effect to happen — he did not think that they were merely hitting each other because if that was true he could map their trajectory. Instead, he wrote the random patterns were a byproduct of everything trying to find some equilibrium. A picture of Brown’s apparatus is here at Quora.

This grain experiment was important because it led to the idea that individual particles exist and have temperature even though Brown did have the mathematical formula to prove it.

Einstein and Brownian Motion

In his paper, Brown the of “invisible cells” populate the world. Chemists took this to be “molecules” but that does not fully capture the idea of heat and energy. Almost eighty fives year later, the equivalent of a Uranian cycle or a quarter of a Neptunian, the physicist Albert Einstein, lauded the botanist, for the idea of randomness and saw that the “cells” Brown was discussed were not molecules as the chemists thought, but atoms.

Einstein picked up on the idea as heat as energy and hailed the botanist as a major contributor to his quantitative theory of Brownian motion. These papers led to his Theory of Relativity. You can read it in full thanks to the Physics Department of the University of Sydney, New South Wales, Australia. It is also short, but dense, but better if you ignore the maths.

The Brownian Chart

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