But in truth the source of life is a difference in air pressure, the flow of air from spaces where it is thick to those where it is thin. The activity of our brains, the motion of our bodies, the action of every machine we have ever built, are driven by the movement of air, the force exerted as differing pressures seek to balance one another out. When the pressure everywhere in the universe is the same, all air will be motionless and useless; one day we will be surrounded by motionless air and unable to derive any benefit from it.
