Mouvement brownien
Smoke particles under a microscope jiggle endlessly with no one pushing them. This simulation shows why: invisible molecules are colliding with them from every side, and the imbalance at any instant is enough to move them.
Comment utiliser cette simulation
- Change the temperature and the fluid molecule density
- Adjust the size of the suspended particle
- Trace the particle's path over time
Ce qu’il faut observer
- The motion never settles down, however long you wait
- Smaller particles jiggle more, because the collision imbalance matters more relative to their mass
- Raising the temperature makes the motion more vigorous
La physique derrière
A suspended particle is bombarded from all directions by fluid molecules. On average the collisions cancel, but at any instant there is a random imbalance that pushes the particle a short way. The resulting path is a random walk, and its net displacement grows with the square root of time rather than in proportion to it.