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Physicists Do What Einstein Thought Impossible
An anonymous reader writes "Einstein worked on Brownian motion (the movement of small particles in a fluid as they collide with the fluid's molecules) in 1905, but said it would be 'impossible' to determine the speed and direction of a single particle during this dance. Now researchers have gone and done it, by suspending a dust-sized glass sphere in air (which slowed down its dance moves, since it had fewer collisions with spaced-out air molecules than it would have had with water molecules). The researchers held the sphere in place with 'laser chopsticks,' and then watched how the glass bead bounced around to determine its direction and speed (abstract)."
They would clearly be more "chopsticky".
It must have been something you assimilated. . . .
TFA doesn't refute any of Einsteins conclusions about Brownian motion. It only shows that it was something impossible to do at Einsteins time. What a cheap way to grab attention!
Brownian Motion is a mathematical construct, which, among other things, is nowhere differentiable (almost surely). You can pin a BM down into sets with high probability, but no, you can't really predict it. It is merely used to *model* the movement of a particle in a fluid, it is not actually the process by which the molecules move. Indeed, "such a path represents the motion of a particle that in its wanderings back and forth travels an infinite distance in finite time. [BM] does not in its fine structure represent physical reality." (Billingsley, "Probability and Measure"). At least the science is interesting.