tlb wrote:Loren Pechtel wrote:But atmospheric pressure doesn't exist at the molecular level. It's just a bunch of molecules moving quite fast. That's what you're going to have to deflect. That's basically the same as the gravity field required to hold onto the atmosphere.
Pressure at the macro level can be related to kinetic energy density at the micro level, since it is the average force per unit area exerted on a plane by molecular collisions. As the pressure at sea level is set by gravity, you get the following effect: when air temperature increases or decreases (related to the average molecular kinetic energy) the air density decreases or increases in turn to keep the pressure constant.
PS: this is at the level of a room, trying to explain weather patterns of high and low pressure is more complicated; however it is still related to temperature.
You're not rebutting me at all. We experience pressure at the macro level, but at the micro level it's just the movement of molecules. Gravity is acting against the speed of the molecules heading towards the backstop and this is basically the same thing as a planet being able to drag back a molecule that is out in the thermosphere.
A good portion of the molecules in the atmosphere are moving faster than her slug thrower's bullets. You can't bounce those molecules without also bouncing the bullets.