# Tag Info

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Why is space a vacuum ? Because, given enough time, gravity tends to make matter clump together. Events like supernovae that spread it out again are relatively rare. Also space is big. Maybe someone could calculate the density if visible matter were evenly distributed in visible space. I imagine it would be pretty thin. (Later) Space is big. Really ...

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Space is sometimes described as a vacuum better than mankind could create in any laboratory. But it is not a vacuum, but a tenuous plasma carrying the interplanetary medium (solar wind). It is also structured, forming the Heliospheric current sheet. This means that space has the characteristics of a plasma. It is electrically conductive, carries magnetic ...

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The questions you ask are really difficult to answer. Mass is not a property of space (or space-time itself), but of physical objects in classical physics. In General relativity, it is difficult to speak about mass clearly, there is no good general definitions. Now, there are two naive metaphysics about space-time. The substantivalists think that space-time ...

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If (hypothetically) you could find a far off region of space where there is no radiation of any sort, and you place a hot object there, then it would radiate away its heat and gain no heat back from its surroundings. The rate of radiation would gradually decrease but eventually it would lose its last photon and enter a ground state of absolute zero ...

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Check synchrotron radiation in the wiki article. When high-energy particles are in rapid motion, including electrons forced to travel in a curved path by a magnetic field, synchrotron radiation is produced. bold mine. Charges when accelerated radiate electromagnetic radiation, and the curved paths in the synchrotron give a continuous angular ...

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Virtual particles are far more plausible because of experimental results such as the Casimir Effect which is non classical and predicted as a consequence of the "reality" of virtual particles.

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First, space is not a complete vacuum. You still have some particles going around in there. In common mind, space is empty, but it is only "empty" because you have some massive particles in it (like planets, stars etc.). Around these particles you have a strong gravity field (of course in the other, "empty" regions you have that too, but only very weak ...

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Particles do not constantly appear out of nothing and disappear shortly after that. This is simply a picture that emerged from taking Feynman diagrams literally. Calculating the energy of the ground state of the field, i.e. the vacuum, involves calculating its so-called vacuum expectation value. In perturbation theory, you achieve this by adding up Feynman ...

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Any object that approximates a black body (which means pretty much everything) radiates heat according to the Stefan-Boltzmann law: $$W = \sigma T^4$$ If we could insulate the object from all incoming radiation (which is impossible, but let's go with it for the sake of this question) the change of temperature with time would be given by: $$C ... 1 No one really knows the answers to you questions. Spacetime is most assuredly made of something as it is not a void and, by General Relativity, shown to be inhomogeneous: curvature over here in this piece of spacetime can be different from the curvature in that piece over there, so it has position-dependent properties. You could construe the cosmological ... 1 There are, of course, 3 mechanisms for heat transfer - conduction, convection and radiation. So isolated in vacuum convection and conduction will play no role (provided, of course, the vacuum is perfect, which is a pretty good assumption for space, but not quite reality). I am guessing from your question that no radiation hits the object in your thought ... 1 As far as I know, the number of points to not have any influence on divergent behaviour. The infinite vacuum energy comes from the fact that we allow arbitrary frequencies for our quantum fields. There is no difference if we sum or integrate a constant from zero to infinity, the result is still infinite.$$\sum_{k=0}^\infty {1\over 2} \sqrt{k^2+m^2} ...

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Sorry for being oxymoronic here, but your questions (OP) are in their very meaning, illogical. I mean to say that you have used extremely misleading terminology to present your question. I am unable to understand what exactly you intend to ask. Why is space a vacuum? Space is a vacuum because the word vacuum means "empty space". If the universe had no ...

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You are probably referring to the phenomenon where pairs of particles can appear and disappear randomly inside a vacuum. Such a situation where energy is then extracted from these pairs can occur, for example, at the edge of a black hole, where a matter and antimatter pair would be created. The antimatter would go into the black hole, while the matter flies ...

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Maybe what you are looking for then, is the Casimir effect?? Here, the energy in a vacuum between two plates produces a force between them.

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