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Black holes ruled out as universe’s missing dark matter

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Re: Black holes ruled out as universe’s missing dark matter

#31

Post by dantillberg »

sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

Maybe the big bang did produce a black hole, and we're living inside it?

Back in my undergrad physics days, I postulated that our "universe" could be a big black hole inside some "extraverse". I worked through classical gravitational calculations to determine, from an estimate of the mass density of the universe, what the Schwarzschild radius (aka event horizon radius) of that black hole would be, and it came out to between 5 and 40 billion light years or so (the density of the universe is hotly debated, see other discussion in this thread about dark matter), which is at least the right order of magnitude.

Re: Black holes ruled out as universe’s missing dark matter

#32

Post by perl4ever »

InclinedPlane wrote: post #19
sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

This is an important question with a slightly surprising answer. First you need to understand that the Big Bang was not an explosion of matter into space, it was an explosion of matter and space (technically space-time). This might be hard to wrap your head around, it might be easier to think about space-time as non-infinite, say curving back on itself like the surface of a balloon (though as far as we can tell it is…

"First you need to understand that the Big Bang was not an explosion of matter into space, it was an explosion of matter and space (technically space-time)."

This is a type of statement I have read many, many times, but to me, it's the same as saying "wakalixes!". I've never read anything that gave me a hint of why and how there should be a difference between two objects receding from each other and "space itself" expanding.

Re: Black holes ruled out as universe’s missing dark matter

#33

Post by sulam »

pdonis wrote: post #23
sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

> if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? No, because it was expanding too rapidly. The usual intuitions about how much mass in how small a volume it takes to make a black hole assume that the mass is stationary, or nearly so.

This matches a description I was able to find online. What that seems to imply though is that expansion was literally faster than light. Yes? No?

[edit] and it seems this is true and can be explained by the space-time matrix not being bound by light speed limits.

Re: Black holes ruled out as universe’s missing dark matter

#34

Post by headShrinker »

sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

There are major challenges/issues with Big Bang theory. The easiest issue to see and understand is temperature in the CMB appears to indicate “communication”... basic descriptions of the problem here https://youtu.be/dbm3M9Bz4RE

No one really knows anything about the universe before 10^-42 seconds, and there is no physics to describe what likely happened. Photons/light and matter as we known it didn’t exist and wouldn’t for another 400,000 years.

There are many very deep issues that are explained pretty well here https://youtu.be/JDmKLXVFJzk It’s pretty heady so be ready

Re: Black holes ruled out as universe’s missing dark matter

#35

Post by pdonis »

sulam wrote: post #33
pdonis wrote: post #23

Earlier quoted context omitted.

> if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? No, because it was expanding too rapidly. The usual intuitions about how much mass in how small a volume it takes to make a black hole assume that the mass is stationary, or nearly so.

This matches a description I was able to find online. What that seems to imply though is that expansion was literally faster than light. Yes? No? [edit] and it seems this is true and can be explained by the space-time matrix not being bound by light speed limits.

> What that seems to imply though is that expansion was literally faster than light. Yes? No?

No. No particle of matter outruns a light ray at the same location and moving in the same direction. Or, to put it another way, all pieces of matter are moving within the light cones at their spacetime locations. "Moving within the light cones" is the correct General Relativity version of "nothing goes faster than light".

The coordinate speed of pieces of matter can be greater than c, but in a curved spacetime that, in itself, is not a problem.

Re: Black holes ruled out as universe’s missing dark matter

#36

Post by perl4ever »

InclinedPlane wrote: post #22
oldandtired wrote: post #13

Earlier quoted context omitted.

Let's change this a little bit. We have observed specific phenomena but not that which created such phenomena. As far as "Black Holes" as per theoretical descriptions are concerned, they cannot exist in a finite time universe as far as we (the observers) are concerned. The theoretical models used all have as a basic assumption that increasing gravity (whatever that may be) will cause a slow down in time as observed a…

We have observed matter falling into a black hole. We've watched "hot spots" in orbit of a black hole in the accretion disk shine their light at us as they orbited the black hole. We've watched as the orbit got tighter and tighter and the light was dimmed by gravitational red shifting, then we've watched the light blink out and disappear as the blob of gas fell below the event horizon. The evidence for the existence…

From your point of view, if so-called black holes are "fuzzballs"[1] is that a vindication or a refutation of the existence of black holes? Without a deep understanding of physics, I have the general attitude that infinities must be a mathematical error, and therefore something must stop black holes from collapsing totally, but whether they "exist" is only a matter of definitions.

[1]https://en.wikipedia.org/wiki/Fuzzball_(string_theory)

Re: Black holes ruled out as universe’s missing dark matter

#37

Post by mikekchar »

sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

Ob: I know nothing. But the way I look at it is: what is the difference between a point and infinite space? Taken from the perspective of light (travelling at the speed of light), the universe is still a single point. That is, the size of the universe is Lorenz contracted to zero. It also takes zero time to go from one end to the other ;-)

From the perspective of light, what is the difference in the universe at the instant of the big bang and some time after it? Well... potentially nothing. The structure of the universe only makes sense from within the context of the universe itself. The space of the universe only makes sense inside the universe. The time of the universe only makes sense inside the universe.

It's not the case that the big bang exploded material into empty space. The amount of energy/mass in the universe has never changed from the perspective of the universe. The big bang is the distinction of structure in the universe. What is the difference between a point and an infinite space of uniformity? When an infinite space of uniformity loses absolute uniformity, what happens?

Why did the universe not collapse into a singularity? Because it was already a singularity. It would require some kind of structure in space in order for a "collapse" to make sense. As soon as the structure is created, it is no longer uniform, and so it will no longer collapse uniformly - especially if space is expanding at the same time. I suspect there are several black holes at the "centre" of the universe, but I can not think of a way for all the matter to collapse into a singularity.

Re: Black holes ruled out as universe’s missing dark matter

#38

Post by ketralnis »

perl4ever wrote: post #32
InclinedPlane wrote: post #19

Earlier quoted context omitted.

This is an important question with a slightly surprising answer. First you need to understand that the Big Bang was not an explosion of matter into space, it was an explosion of matter and space (technically space-time). This might be hard to wrap your head around, it might be easier to think about space-time as non-infinite, say curving back on itself like the surface of a balloon (though as far as we can tell it is…

"First you need to understand that the Big Bang was not an explosion of matter into space, it was an explosion of matter and space (technically space-time)." This is a type of statement I have read many, many times, but to me, it's the same as saying "wakalixes!". I've never read anything that gave me a hint of why and how there should be a difference between two objects receding from each other and "space itself" ex…

New space is being created between those two things.

When they move 1 meter apart from each other through space, they'd move 1 meter back again to meet up. But when space itself is expanding between them, they've moved 1 meter apart but now to get back together they have to move 2 meters.

This has some other subtler ramifications. It means that the space between the two objects can increase at faster than the speed of light (because you can't move through space faster than light, but space can expand faster than light). Also, with the Higg's field's nonzero rest value _energy can be created from nothing_ by creating space. Yes, this violates conservation of energy.

Re: Black holes ruled out as universe’s missing dark matter

#40

Post by jobigoud »

dantillberg wrote: post #31
sulam wrote: post #4

This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…

Maybe the big bang did produce a black hole, and we're living inside it? Back in my undergrad physics days, I postulated that our "universe" could be a big black hole inside some "extraverse". I worked through classical gravitational calculations to determine, from an estimate of the mass density of the universe, what the Schwarzschild radius (aka event horizon radius) of that black hole would be, and it came out to…

How is it the right order of magnitude? Did you compute that based on the size of the observable Universe? But that's arbitrary, the Universe is way bigger than that.
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