This is due to the fact that there is little food (flying insects) for them to eat. If they stayed awake in a warm home, without hibernating, then they would starve. We can begin the bat exclusion process during the winter months.
Mean free path of molecules in a gas. The molecules in a gas are assumed to be in continuous random motion making collisions with each other and with the walls of the container. The mean distance that the molecules travel between one collision and the next is called the mean free path of the molecules.
Using the ideas of kinetic theory, the idea that the properties of a gas are due to the motion of the atoms that compose it, Loschmidt calculated the mean free path of an atom based on diffusion rates. His result was that there are 6.022x10 atoms per 12 grams of carbon.