Entropy and Energy

Khashishi

Here's another simple way to think about it. An open system doesn't actually evolve to minimum energy. Actually, it evolves toward a temperature which matches the temperature of the surroundings. In deep space, the temperature of the surroundings is about 2.7K, which is very cold. Most systems we care about have much higher temperature, so heat leaks out. So, this is why it looks like the system evolves towards minimum energy.

For comparison, an excited hydrogen atom (n=2) has an energy of 10.2 eV, which has a temperature equivalent of 118000K. On Earth, the hydrogen atom is constantly colliding with other atoms, so it will evolve toward thermal equilibrium, which is somewhere around 300K, so almost all the hydrogen atoms will go to the ground state (ignoring the obvious possibility of forming molecules).