Brownian motion

Let me tell you a story, of a particle;
A simple particle; passive in its lifestyle,
Identical in every way to its neighbors,
Individuality snatched by a lifetime of collisions.

One fine day mankind developed an interest
Something must be wrong from the onset
Poor guy, has such a dilute existence!
Let's label its life with a mean free length.

And then they thought they understood its nature
Simple enough; only a white noise would matter
A mere particle in a grand sophisticated universe
Yet these random dots usually make things better.