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Monday, 20 June 2011

Not so dusty



As any fule kno, Brownian motion is a random jiggling of small particles suspended in a fluid. The name derives from botanist Robert Brown who first observed it in pollen grains suspended in water. It appeared to be an example of perpetual motion until Einstein explained the phenomenon using kinetic theory. Basically he ascribed the motion to random fluctuations in the way that fluid molecules impinge physically on the much larger particles. 

Over two thousand years ago, Lucretius observed Brownian motion in dust particles dancing in a shaft of sunlight, using it to prove the existence of atoms.

...look where the sun
Through some dark corner pours his brightest beams,
A thousand little bodies you will see,
Mix in the rays, and there forever fight
Arrayed in mimic troops, no pause they give
But meet and part again, nor ever cease.
From this you may conjecture of the germs [atoms]
What ‘tis for ever in the mighty void
To be tossed up and down. In some degree
Such small events may illustrate great things,
And give a clue to knowledge. So ‘tis well
That you should note these bodies how they rush
In the sun’s rays, because such rushes show
What secret hidden forces lie below.

2 comments:

James Higham said...

Particle theory. You've hit on a beautiful example of where the physical processes are approximated by a mathematical model.

It might surprise you that a metaphysicist in me thinks this is a perfectly valid thing to do. Real science sees and wishes to understand.

Particle theory is a fine model, as long as one accepts its limitations but that applies to observed metaphysical phenomena as well.

And whoever said there is no beauty in science and maths has obviously not observed a joyous normal curve or a poem on Brownian Motion.

A K Haart said...

Yes there is beauty in science, that's what is most upsetting when it is corrupted.