it has mass (try to accelerate it), try to move something against it, it has momentum (it blows things over),
One example from everyday life that demonstrates the substance of the atmosphere is in wind resistance. When you stick your hand out of a moving car window, you feel a force pushing against your hand. This force is due to the resistance of the air molecules in the atmosphere pushing against your hand as you move through them. This sensation is an indication that the atmosphere has substance and is not just an empty void.
