# Tag Info

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Simulating gravity in space basically means simulating weight, which requires acceleration. So basically, the question is, how do we create acceleration in space. The easiest method for simulating gravity in space is by spinning the space station. In this case, the reaction force to centripetal force substitutes the force of gravity, which pushes the inner ...

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There can be no such thing as a "supermassive neutron star". The theoretical upper mass limit for a neutron star is somewhere between 2 and 3 solar masses. Any more massive and they inevitably form black holes. So I am not clear what kind of "neutron objects" you were thinking of? Nor is it clear what you mean by "non-stellar" objects that will have the ...

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The dark matter model that is used to explain the "missing mass" problem relating to our Galactic rotation curve, consists of a pseudo-spherical distribution that is much more extended than the visible stars and gas. Even though this "halo" contains more than ten times the mass of the visible matter, when you work out what it's density should be in the solar ...

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There is no proof that dark matter exists. Until any real evidence is collected that can constitute proof, anything about dark matter's properties and possibilities is mere speculation. On the other hand, there's no proof that it doesn't exist. For all we know, we might be surrounded by it as we speak. Is anything affected? Who knows.

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The black hole region of a spacetime is defined as a region where nothing can escape to infinity and an event horizon at a given time is the boundary of a connected region of space which is part of the black hole region. As you're after a simple answer I won't give a formal definition of a black hole or an event horizon, but they can be found in Wald. The ...

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Heat death of the Universe doesn't mean that there is no energy in it, it means it has reached thermodynamic equilibrium and hence no useful energy in it. This could in theory occur in an infinite Universe. Of course thermodynamics is statistical in nature, so an argument could be made that some extremely unlikely event in a region of the Universe could ...

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Ultimately this is an application of Occam's razor In order for the light to be gravitationally redshifted, it would have to be coming out of a deep gravitational well. For the red shift observed in galaxies to be gravitational, you would have to suppose several things. First, that the stars in distant galaxies are somehow much denser: more than neutron ...

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I would hazard a guess at this point, but effects of gravitational red-shift would perhaps average out, so approximately 50% of light would orginate from objects with stronger gravitational fields and 50% from weaker gravitational fields. Hence, we would see blue-shifted and red-shifted objects if gravitational redshift is an prominent as assumed. However, ...

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The Schwarzschild metric by definition can be written in a spherically symmetric form, the Kerr metric is not spherically symmetric, but in Boyer–Lindquist coordinates the event horizon has a constant radial coordinate. For most people this will be good enough to say the event horizon of Kerr black holes (including Schwarzschild black holes) are perfect ...

3

You cannot see the event horizon. That being said: A non-rotating black hole, free of external influences, has perfect spherical symmetry. All its properties are exactly the same in any direction, period. This is the Schwarzschild metric. https://en.wikipedia.org/wiki/Schwarzschild_metric Even if it is electrically charged, if it's non-rotating, and free ...

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Probably not. If black holes do in fact exist, their shape must be affected by a number of factors. Matter (and therefore gravity) is not distributed evenly around the galaxies. The gravitational pull of cosmic bodies would take its toll. A perfectly spherical shape would suggest that the hole's gravity is so powerful as to render all other gravitational ...

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The Sun's luminosity is $3.8\times 10^{26}$ W. Application of mass energy equivalence tells you it loses mass at a rate of 4.25 million tonnes per second as hydrogen turns into helium. This is practically nothing as far as the structure of the star goes. Over its lifetime, the Sun has lost about 0.03% of its mass in this way. Radiation pressure is a ...

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Here's the bare bones reason for stars like our sun. The full story is much more...full. Expansion means cooling. Cooling means less fusion. Less fusion means less energy driving expansion, meaning the outward pressure is going down. Eventually gravity is pulling inward more strongly than radiation is pushing outward. So the material collapses again. ...

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As I understand it, general relativity says that there's gravitation everywhere in the universe, and this gravitation creates dips in space, so to speak, often represented in 2D as a weight on a rubber sheet, like the picture below. Source, so, a black hole might generate a perfectly spherical event horizon, but it generates it on a not perfectly flat 3 ...

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Some good answers, I'm going to give kind of summary, cause you touched on a few points. Why does gravity increase in star formation Gravitation is a product of a few forces. Mass, density and, not to be ignored, rotation speed. It's not actually the fusion process that keeps the sun from contracting, at least, not directly. It's heat that keeps ...

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As a star runs out of hydrogen fuel, the fusion slows, causing the gravity to overpower the outward force of pressure, thus contracting. Contraction of the star causes high temperature and pressure, to the extent that it is enough to fuse helium into carbon, then the energy released is stronger than the gravity, increasing the size of the star into a red ...

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I am going to start with this paragraph from Wikipedia (emphasis mine): The most important fusion process in nature is the one that powers stars. In the 20th century, it was realized that the energy released from nuclear fusion reactions accounted for the longevity of the Sun and other stars as a source of heat and light. The fusion of nuclei in ...

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In general relativity, gravity neither pushes nor pulls. To explain why ball travels in an arc you note the start and end points of the throw in 4d space time (3 space co-ordinates and 1 time coordinate) You then find the shortest path between these two 4d points in the curved spacetime surrounding the Earth. This shortest path is the path in spacetime that ...

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I'm guessing that this misunderstanding is a result of the oft-used rubber sheet analogy. The rubber sheet analogy says that, according to general relativity, mass curves space-time like a heavy bowling ball on a near-taut blanket (or rubber sheet) curves the blanket/sheet. This resulting curve makes other bits of matter/energy move in different ways. I'm ...

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