Robert Brown

Who Refused to Explain It · Botanist · 1773–1858

Who saw in 1827 that tiny particles suspended in water will not keep still, tested the obvious explanation to destruction by grinding up dead pollen, glass, soot and a fragment chipped from the Sphinx and finding that all of them danced alike — and then declined to say what caused it, because he did not know.

Who was Brown?

Robert Brown was born at Montrose in 1773, studied medicine at Edinburgh, and was recruited by Joseph Banks as naturalist on the Investigator under Matthew Flinders, which surveyed the coasts of Australia between 1801 and 1805. He returned with some four thousand species, most of them new to science, and spent the rest of his life as the foremost descriptive botanist in Britain, librarian and then heir to the care of Banks's collections. In the summer of 1827 he was examining, under a simple single-lens microscope of the kind made for him by Bancks, the pollen of the plant Clarkia pulchella in water. Within the grains were small particles, and they moved: an irregular, ceaseless jostling with no direction and no rest. The natural explanation was that he was watching something alive — pollen is, after all, a reproductive organ. So Brown tested it. He used pollen from herbarium specimens that had been dead for a century, and the particles moved as before. He went further and left the living world behind entirely: powdered glass, soot, metals, minerals, and famously a fragment chipped from a stone of the Great Sphinx. Ground fine enough and suspended in water, every one of them showed the same restless motion. That settled what it was not. Brown published the observations in 1828 in a short pamphlet, and he did not offer a cause, because he had none and would not manufacture one. The explanation — that the particle is being struck unequally, from all sides and at every instant, by the moving molecules of the water — was given by Einstein in 1905 and confirmed experimentally by Perrin in 1908, which is also when it became one of the strongest pieces of evidence that matter is made of particles at all. Brown's other lasting contribution, made in 1831 while examining orchids, was to recognise that a body found in nearly every plant cell is a constant feature of it, and to name it the nucleus.

Major achievements

• Collected and described some four thousand Australian species from the Investigator voyage of 1801–05
• Observed in 1827 the ceaseless irregular motion of particles suspended in water
• Showed by experiment that the motion is not vital — century-old dead pollen moved just the same
• Extended the test to ground glass, soot, metals and a fragment of the Sphinx, and found the motion in all
• Published the observations in 1828 without proposing a cause

Life in brief

• 1773 — Born at Montrose: Son of a clergyman.
• 1801 — Sails on the Investigator: Naturalist to Flinders's survey.
• 1805 — Home with four thousand species: Most of them new.
• 1827 — The pollen of Clarkia: Particles that would not keep still.
• 1828 — The pamphlet: Ground glass, soot, a chip of the Sphinx — and no cause.
• 1831 — The nucleus named: A constant body in the plant cell.
• 1858 — Dies in London: The cause still unknown to him.

Explore the life of Brown — five chapters

1. Four Thousand Species — Naturalist on a survey of the Australian coast
2. A Constant Body in Every Cell — Naming the nucleus, 1831
3. The Pollen That Would Not Keep Still — June 1827
4. And No Cause — A pamphlet that stops where the evidence stops
5. Eighty Years Later — The motion becomes the proof that atoms are real

Read the five-chapter life of Robert Brown →

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