So what's the observation or what's the experience from everyday life that tells us that gas is, in fact move at high velocities? Well, for example, if you forgot to wash your feet or you've been wearing your shoes for way too long, you know that if you take off your shoes and there's a girl or a voice sitting across the room, they will definitely smell you instantaneously. That's why you better keep your shoes on. That's because when you take off your shoes the molecules of air trap in your socks and in your shoes escape and move at very high speeds in all different directions. So the person sitting across the room from you will definitely smell you. So you better keep those shoes on.