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The typical speed of an air molecule is a few hundred meters per second, while escape velocity from Earth is over 10,000 meters per second. So almost all the air molecules just fall back down. They're affected by gravity just like everything else! We do lose some air molecules this way, though. In particular, hydrogen and helium are lighter, so they move ...


10

Air fails to escape into space for the same reason you fail to: gravity. As noted in Kevin's answer, occasionally some do get going fast enough to escape. You would too, if enough stuff hit you hard enough. :) Space is a vacuum (for some definition of vacuum), because vacuum is simply the absence of air/gas pressure, and there aren't enough gas molecules in ...


3

To get an understanding on quantum field theory issues, you have to understand the difference between virtual particles and real particles. Virtual particles, in contrast to real particles, are a mathematical construct inspired by the Feynman diagrams used to describe interactions. These diagrams start with real particles, i.e. particles that have the mass ...


2

You can describe nothingness in a rigorous and consistent way, even with a canonical categorical model. If nothing is not just absence of stuff and light otherwise darkness in an empty area, but absence of space and time itself, how is it possible to describe it mathematically? Just the exact same way you use axioms such as $\forall x\forall y \exists ...


2

Gravity. You can think of planets like wells or deep holes in the ground (gravity wells). Denser things fall to the bottom (rocks), less dense things rest on top of that (water), even less dense things on top of that (air), and finally the least dense thing on top of everything (vacuum). The air, for the most part, isn't leaving the planet for the same ...


2

Yes and no. A vacuum solution could be stationary, could be static, could be neither. For the orbiting black holes you end up with gravitational waves and gravitational radiation. You either have some going out, and the bodies in spiraling or you have some coming in and driving the system or both. And the point is that you have to specify the state of the ...


1

To give a simple answer: Space is an (almost) vacuum, since there is simply not enough air left to be there. Where did all this air go? Due to gravity the air is attracted to large objects, like planets and exactly this gravity is also keeping the air close to the object - preventing it from "flowing back into space"


1

The real underlying basis of an electromagnetic wave is a synergy of zillions of photons. In this sense it is only macroscopically that the classical theory applies. The way the build up happens, photons into an electromagnetic wave, is not simple but an example can be seen here. Hand waving: the photon as an elementary particle is a quantum mechanical ...


1

Yes, in space this would be possible. The reason that one cannot open up a space inside a plastic bag when it is empty and sealed is because of the air pressure surrounding the bag. A huge number of air molecules are constantly bombarding the plastic bag from all directions (a.k.a. air pressure), so it would take a large amount of evenly distributed force ...


1

A simple answer is that there is no point at which you are close to the speed of light, you might be close to the speed of light relative to other objects however you can keep trying to accelerate, and your slow relative to other objects. Your both fast and slow. From the point of view of an object looking at you, they may see you travelling close to the ...



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