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.
Out in the world, this is a normal process, but in the body, it can result in unnecessary and unwanted damage. Free radicals are free because they float around until they stabilize, and radical in the sense that there are a wide variety of molecules from which they can take an electron.