Re: "Ricochet" by higher density cold air?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1ZNUF</div><div class="ubbcode-body">Undisturbed air can stratify into thermoclines that will cause a bullet to deflect off of a denser layer of air. Don't know if you've ever seen early mornings in the mountains where woodsmoke seems to form a layer that it just won't rise above; that's a thermocline, or marked differnence in temperature and density between layers of air. Eventually air turbulenc will start to mix them up, but yes, you can "ricochet", or experience increased deflection, off of an undisturbed thermocline. Look for the phenomenon early in the morning and on damp, overcast days.</div></div>
C'mon now, just because atmospheric thermoclines exist, doesn't mean solid objects can bounce off of them. (Just like WMDs - just because they existed once somewhere, doesn't mean they were ever in Iraq). Show me some experimental evidence under controlled conditions to support that, or at least a valid mathematical model with good explanation of how it would be theoretically possible.
Sound waves (and possibly radio waves) can bounce off thermoclines but they have no mass. When mass is involved, then you have to bring momentum and reactive forces into the picture.
In order to get a falling bullet turning around to rise back up away from gravity, you have to have an upward force greater than gravity. Where's the force coming from? Especially on a still layer of cold air? There's only three conventional ways that could happen. Either through reactive conservation of momentum like a steel bearing falling on an anvil, or through aerodynamics of the bullet itself traveling through air like a glider's wing.
In the first case, the bullet would have to elastically deform itself then spring back in the opposite direction, same way a ball bearing hitting an anvil does. However, a bullet is too dense and its metal too strong for normal atmospheric air to deform it. And because the bullet is made of lead and copper, it has little elasticity. Once it's deformed, it stays that way. Alternatively, the air (rather than the bullet) would have to be quickly compressed then 'spring back' against the bullet, the way a pool table bank pushes a billiard ball back. That's a no-go too, because the bullet passes through the air. So any air that's compressed is just pushed away against other air. I doesn't come back at the bullet right away. (Sort of like any tax money you pay to the government for them to use in economic stimulus never comes back directly to you. It just gets lost out in banking land somewhere
).
In a related, second case, a 'skimming effect' like a flat pebble skipping across a lake, or hydroplaning tire might apply. But that involves a non-compressible liquid (water) resisting compression in all directions, and inertia of its mass and inertia of its surroundings acting as a container. So it can push back the pebble up into the less denser air, with enough force to throw it out of the water. Just as a bullet off of water would. But, simple cold air doesn't have enough density, nor is the thermocline sharp enough to get that effect.
In the third case, because the bullet is symmetrical and spinning at 180,000 rpm, it won't behave like an airplane wing. Around a wing there's a vacuum created on top and pressure on the bottom that pushes it up. A flying bullet has exactly the same shape on the top as on the bottom, so no wing effect and no force could come from that either.
The only possible force would come from moving air, rising up against the falling bullet. Like a cross-wind, but vertical.
But I'd be fascinated to hear how any bullet deflections off of air actually might work.
