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Does vacuum or outer space contain any gases? Recently i watched a video on youtube,in which NASA installs a camera on a spacecraft.The footage shows some dust particles or some matter floating over the space craft's surface and as well from the thrust.What exactly is that? If there is nothing in vacuum,how come newton third law works out to make it move in turn? Here is the link

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Related: , and links therein. – Qmechanic Mar 16 '14 at 19:06
up vote 3 down vote accepted

Vacuum in outer space may contain cosmic dust which is composed of a few molecules or atoms left by by stars or other cosmic objects. In fact there are different types of dust such as star dust or intergalactic dust. There is aroud 1 atom per cubic centimeter. Now if you are talking about empty space or vacuum in quantum mechanics, vacuum is defined as the state with the lowest possible energy. In fact vacuum is not that empty, since due to Heisenberg principle, virtual particles are created and destroyed in pairs.

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My understanding is that the vacuum is defined to not contain any "matter", i.e. no gases or anything like that. What's fascinating is that under the model of Quantum Electrodynamics, there are still quantum fluctuations that allow one to observe virtual photons even in the vacuum.

Outer space, on the other hand, is NOT a vacuum. IIRC it's about 3 Kelvin, which is 3 degrees celsius above absolute zero, and therefore DOES contain (a minimal amount) of dust and gases and the like.

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