When our entire section of the universe was in a single hot dark dense state, right before our big bang, what was the escape velocity?
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4You can’t escape from the universe. The universe doesn’t have an escape velocity, so the question is based on a false premise. – Ghoster Mar 20 '24 at 23:52
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I meant our section of the universe, not the universe. – Mark Swartz Mar 20 '24 at 23:53
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Plus, whether or not you can escape from the universe, can an escape velocity be calculated for a single hot dark dense state consisting of one big bang of mass anyway? – Mark Swartz Mar 20 '24 at 23:57
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2There is no such thing as “one big bang of mass”. – Ghoster Mar 20 '24 at 23:58
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It isn’t clear what you’re talking about. I consider the Big Bang to have been the limit $t\to 0$ or $a\to 0$ in a Friedmann model. Talking about what was before this singularity is meaningless. Are you talking about immediately before inflation? If so, that’s vague because there are lots of inflationary models. – Ghoster Mar 21 '24 at 00:01
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I'm asking if a single dark hot dense state with a mass of one big bang would have an escape velocity, and if the answer is that there would be an escape velocity then the question would be how did our ever expanding section of the universe achieve escape velocity, so I was first wondering if anyone ever calculated the escape velocity for one big bang of mass. – Mark Swartz Mar 21 '24 at 00:07
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Let us continue this discussion in chat. – Mark Swartz Mar 21 '24 at 00:15
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If you are thinking that the universe started as a small point with all the mass concentrated there, see What really happened at the Big Bang? – mmesser314 Mar 21 '24 at 02:47
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Also see Did the Big Bang happen at a point? – PM 2Ring Mar 21 '24 at 06:02
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Voting to reopen. A perfectly clear question, even though it is based on some misapprehensions. Also has a good answer below. – gandalf61 Mar 21 '24 at 07:39
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To answer your question, it is worth noting that “escape velocity” is a term frequently used concerning objects within gravitational fields whereby an object opposes the gravitational pull of another. This point (in the case of the Big Bang singularity) represents the whole universe in an extremely dense form rather than a localized field of gravity consisting of distinct objects. Let us also consider the idea of the entire universe as one massive body (even though this is not wholly accurate) for argument's sake, then calculating its escape speed would be meaningless since there is no external field of gravitational force to escape from. The universe would amount to nothing else besides itself and thus cannot have any other thing against which to measure escape velocity. In the context of Big Bang, however, expansion does not need to achieve escape velocity in the usual sense. Instead, it occurs because space itself undergoes a rapid expansion as described by cosmic inflation theory and later by general relativity's description of accelerated expansion of the universe. Thereby, the existence of this expansion does not necessarily imply that universal magnitude has achieved a certain specific rate relative to some kind of external gravitational field but simply indicates that such motion characterizes its structure as it changes over time for all matter-energy with respect to inertia according to fabric physics nature.
Adversing
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Thank you for your answer, but if big bangs are natural and they occur somewhere in the universe then would there be an escape velocity from the single hot dark dense state with a mass of one big bang, and if so, what would that be? – Mark Swartz Mar 21 '24 at 00:35
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@MarkSwartz that's not how it works, and any velocity would be meaningless. – JEB Mar 21 '24 at 00:38
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@MarkSwartz You don't really understand what the Big Bang is. Try this video from Sabine Hossenfelder. – StephenG - Help Ukraine Mar 21 '24 at 00:50
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Advertising thank you for your answer, but if after stellar collapse, the original space remains and only the matter is compressed, doesn't that imply that big bangs go into original space, and only the matter is bulkier? – Mark Swartz Mar 21 '24 at 14:22
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Similarly to wit the star collapse, the compression of matter is concentrated within the space. Big Bang on the other hand is associated with the creation and the expanded space because the matter and energy are evenly distributed in this space. Therefore, it is incorrect to say that the Big Bang has expanded into the original space and not that Big Bang itself formed the first space. I suggest you to watch the video linked by @MarkSwartz to fully understand what I mean. – Adversing Mar 21 '24 at 16:09