Click Play to start the simulation
Click Pause to pause the simulation
When the simulation is paused, you can click Step to simulate a single tick
To draw a rectangle, left-click, move your mouse, and left-click again to finish drawing the rectangle
Right-click to cancel the drawing action
Right-clicking an existing rectangle will delete it
Use the 4 radio buttons to select what type of rectangle will be drawn
- Wall will draw a solid wall that bodies will bounce off of
- Spawn Bodies will spawn a set of bodies within the bounds of the rectangle you draw. A dropdown will allow you to select the parameters of the bodies.
- Delete Bodies will delete any bodies within the bounds of the rectangle you draw.
- Measure Statistics will draw a persistent measurement zone. The number of bodies within the measurement zone, and the total and mean kinetic energies of those bodies, will be displayed on the right panel.
You can click the Generate Brownian Motion or Generate 2nd Law of Thermodynamics buttons to generate pre-built scenarios, or add your own walls and bodies to create your own experiments!
Brownian motion is the motion of a microscopic particle suspended in a liquid or gas. The atoms or molecules of the liquid or gas move freely, meaning they only change velocity in collisions with other particles. The microscopic particle, for example a grain of pollen, will move on a seemingly random path. In reality, its motion is due to collisions of the gas particles - too small to see - with the pollen. A higher mean velocity of the gas particles, which is proportional to a higher temperature, will result in more rapid and erratic movement. Experiments with Brownian motion allowed physicists to confirm the atomic model without directly observing atoms.
In our simulation, you can change the number, mass, velocity, and radius of the "atoms" and see how it affects the motion of the larger particle.
The second law of thermodynamics states that the entropy of a closed system will never spontaneously decrease over time. Put simply, this means a closed system will tend toward thermodynamic equilibrium, so thermal energy will flow from hot regions to cool regions, and never the other way around.
In our simulation, we can observe that the left chamber, with low velocity particles (low temperature), and the right chamber, with high velocity particles (high temperature) will gradually tend toward equilibrium: equal mean kinetic energy in both chambers (equal temperatures). Our simulation is an approximation of an ideal gas, with the molecules of the gas freely moving. We only simulation the translation of the particles, we neglect rotational and vibrational states. The simulation may sometimes show the entropy to decrease (heat will flow from cold to hot), since it is only an approximation.