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@knzhou is right in his comment. Light cannot escape from a black hole (BH) because gravity causes a high enough curvature that its paths (lightlike geodesics) outwards all become tangential to the horizon at the Horizon. They don't have to interact with anything, shooting them as straight out from inside the horizon as possible they simply cannot overcome ...


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We know so little about quantum gravity that there's very little (okay, nothing) about the Planck epoch that we can say with confidence, but it's believed that a semiclassical GR description of the Big Bang initial singularity would be that of a naked singularity, so nothing escaped from behind an event horizon.


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The fancy word for a Universe that expands equally in every direction is an isotropic Universe, and one that expands at different rates in different directions is anisotropic. The usual assumption is that the expansion rate is the same in all directions (i.e., the Universe is isotropic); this is the standard Freidman-Robertson-Walker metric for an ...


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We believe that the universe expand in every direction evenly. Even-if there's any unevenness, it's hard to see, and will only be clear at very very large scales. Some people have combed the CMB (cosmic microwave background) and argue that there's maybe some evidence that things aren't perfectly even, but it's not really clear. Right now it really looks like ...


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Short answer: Yes Explanation: The answer to this question is something well documented in astrophysics. The "Size" of a universe is modeled by metaphorical expanding fluids known as the Freidman Equations. These equations say that from a singular point, the universe will expand at rates according to the travel of its components: energy and matter, for ...


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It is an assumption that the universe expands evenly in all directions, and the experimental evidence so far confirms the assumption. Our mathematical description of the expanding universe is based on the assumption that on a very large scale the universe is homogeneous and isotropic, which basically means it's the same everywhere and in all directions. ...


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Our universe looks not only isotropic (the same in all directions) but also homogeneous (the same at each x, y, z at any one time). The fact that our position is not unique is not a principle, it is determined to be so from astrophysical and cosmological observations. Of course, the meaning is that these are so for cosmological distances, i.e., in the large, ...


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Because when we look around, we see that things are, on large scales, the same in all directions. This would be true in such a model only if we were at the centre of this system. That seems ludicrously unlikely: what are the chances that we are lucky enough to be at the one place in the universe where everything looks the same in all directions? So ...


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No one knows. One other thing ... the big bang hypothesis does not explain the origin of the universe (although I recognize that you used the word "formation", not "origin", but I'm not sure what exactly you meant by "formation"). It explains what happens after a certain epoch in our universe's history. What happens before that is completely unknown. ...


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In a nutshell, no. General relativity says that objects with mass cannot travel faster than the speed of light. Space itself can travel faster than the speed of light because it doesn't have mass. However, space isn't moving, it is stretching. If you imagine the Milky Way and other galaxies are on a coordinate plane, the proportions between the galaxies are ...


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Short answer, no. Relativity "forbids" massive matter moving at (or faster than) the speed of light within spacetime, but the recession of distant galaxies is due to the expansion of spacetime itself. As an analogy, put some points on a graph drawn on a rubber sheet, then stretch the rubber sheet. The points will move away from each other, without actually ...


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The reason that energy is usually conserved in most contexts is that Noether's theorem guarantees that energy is conserved in systems with time translational invariance. But the metric of the universe as a whole is (approximately) the Friedmann–Lemaître–Robertson–Walker metric, which does not have time translational invariance (more precisely, there does ...


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Dark matter is uncharged, it might be its own antiparticle. No relationship to matter and antimatter, where mainly its charge conjugation and parity. we don't know that dark matter has any antiparticle broken symmetry. And there is no known relationship between matter and dark matter, except they interact gravitationally and maybe through weak interactions....


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Like it was said before, there is no a priori reason why nature should treat everything symmetrically. Much to the contrary, we know several examples of P- and CP-violating processes. And in other cases we do not even know the reason why a process is "symmetric", when in principle it would be allowed to violate CP (see: the strong CP problem). I guess you ...


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There's not reason to assume nature should treat everything symmetrically. There are many phenomena in nature that we actually know are asymmetric. For example the weak force violates parity symmetry (meaning the weak force has a preference for right or left handedness).


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How can we look into the past? Light has a fixed velocity of almost 300.000 meters per second. Sunlight takes about 8 minutes to reach us. So we see the sun always 8 minutes ago. As the other answer says, stars are much further away and it takes light that much longer to reach us. How do we know how far away the stars are? There are various methods that ...


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Stars are very far away. So light takes a while to get from stars to you. The light arriving now shows you what the stars looked like when the light left. It is like getting a letter from a far away friend. The letter took a few days to arrive. It has news from a few days ago.


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You go outside at night and you look at the sky. That's the universe and that's the past streaming in on you. With your own eyes, of course, you can't see much farther than approx. 2.5 million years back - the Andromeda galaxy is easily seen, even though it's not as pretty as in astrophotographs: https://en.wikipedia.org/wiki/Andromeda_Galaxy. What you will ...


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No, the age of the universe doesn't depend on the observer. What depends on the observer is the "perceived" time that has passed since the Big Bang. What you are asking is if the conformal time and the age of the universe are the same and the answer is negative as you can see in that link.


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Given a few plausible assumptions about the universe its spacetime geometry is described by a solution to the Einstein equations called the FLRW metric. If we know the densities of various types of matter/energy present, e.g. photons/matter/dark energy/anything else, then we can calculate how the expansion of the universe varies with time. Generally ...


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I don't know if negative pressure (but see my added edit below) , more importantly there is a theory of inflation, and some good evidence for it. It was caused by a yet unknown inflation field, with its parameters somewhat matching what the cosmic microwave background (CMB) measurements show. [edit added: The field is a quantum field that rolled from a high ...


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Pocket universes have arisen in different theories. Just to name you two, one is alan Gut's inflationary theory idea that Eternal inflation produces pocket universes with all physically allowed vacua and histories. Another is that from sean carroll, who claims that inside every black hole there is an entirely new universe.



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