Did the Victorian scientist Robert Brown really see Brownian motion?
According to Daniel Deutsch, a chemist working independently in Pasadena,
California, Brown’s brass microscope was not sensitive enough to detect
the random movement of small particles in a fluid.
Brian Ford, another independent scientist, has challenged Deutsch. He
says he has seen Brownian movement through one of Brown’s own microscopes.
He has promised to eat his hat if he is wrong. Brownian movement played
an important role in the development of ideas about the microscopic world
and is still studied in schools today.
Deutsch articulated his arguments against Brown in the Bulletin of the
American Physical Society last year. He claimed that the pollen grains which
Brown looked at were too large to experience Brownian movement, which is
caused by the continual bumping of molecules in a fluid. Deutsch also claimed
that samples in Brown’s microscope were poorly insulated from external vibrations,
which would have swamped any real Brownian motion. ‘Brown was an exceedingly
competent and meticulous scientist,’ says Deutsch. ‘It just so happens that
the facts conspired against him.’
But Ford believes Deutsch is attempting an arrogant rewriting of history.
‘It is an example of the general patronising attitude towards our predecessors,’
he says. He attacks Deutsch’s criticisms in a recent paper in The Microscope,
entitled ‘Robert Brown, Brownian Movement and Teeth Marks on the Hatbrim.’
Ford says that Brown was looking not at whole grains of pollen but at
granules within the pollen. Deutsch accepts that such granules would have
been small enough to experience Brownian movement.
Ford also says that Brown succeeded in damping vibrations. The microscope
was screwed into a mahogany case, making it extremely stable. And the pollen
granules were immersed in water which was then emulsified in oil to block
‘Brown not only anticipated Deutsch’s questions, he constructed experiments
to refute them,’ says Ford.
A long correspondence is in prospect. Deutsch is preparing a 15 000-word
rebuttal of Ford’s criticisms. Meanwhile Ford is arranging a demonstration
of Brownian movement through Brown’s own microscope. He intends to collect
pollen grains in the spring, prepare them in the same way as Brown and video