Is the universe spherical and shaped like a bubble or is it flat?

[Aidan345733]

Could the universe have been created by the collision of two older universes with the same dimensions?
Could the expansion we observe be caused by these two universes still merging like boubbles coming together and the resulting increase of gas makes the film grow larger?

 

[phinds]

Could the universe have been created by the collision of two older universes with the same dimensions?

No. That would have left remnants that we could detect (and which we don't). Besides, what dimension is that? The consensus currently is that our universe is and always has been infinite in extent.

Could the expansion we observe be caused by these two universes still merging like boubbles coming together and the resulting increase of gas makes the film grow larger?

No. Again, that would result in characteristics that we could detect and reality is nothing like that.

You'd do better to learn some actual cosmology instead of worrying about wild hypotheses.

 

[rootone]

Could the universe have been created by the collision of two older universes with the same dimensions?

There are no observations which suggests this.

 

[Aidan345733]

If the consensus is that the universe is and always has been infinite then how can we detect expansion? Infinity doesn’t expand it is just there going on forever.

 

[Aidan345733]

I also know this is rather unlikely and find it fun to play out different scenarios that may be a fun possibility but my biggest question is, if in the beginning the entire universe was condensed down into a singularity then that would, by definition be a black hole and we don’t see new universes spontaneously popping out of the millions of existing black holes in our universe.

 

[phinds]

If the consensus is that the universe is and always has been infinite then how can we detect expansion? Infinity doesn’t expand it is just there going on forever.

Your point of view is a widespread misconception. Google the Hilbert Hotel

 

[phinds]

I also know this is rather unlikely and find it fun to play out different scenarios that may be a fun possibility but my biggest question is, if in the beginning the entire universe was condensed down into a singularity then that would, by definition be a black hole

No, it would not. You misunderstand the word "singularity"

and we don’t see new universes spontaneously popping out of the millions of existing black holes in our universe.

Irrelevant since based on a false premise.

AGAIN, I suggest that you'd do better to learn some actual cosmology instead of worrying about wild hypotheses, particularly since yours are based on misconceptions that a little learning will cure.

 

[Aidan345733]

The Hilbert hotel paradox doesn’t awnser any of the questions referenced above and defiantly doesn’t awnser how an infinite universe created from the original expansion from the Big Bang could be fast enough to result in an infinite universe. From what I understand, which you may think isn’t much, the universe is a flat 3+1 dimensional plane and that is only coming from calculations that we have done within our cosmological event horizon. I understand a singularity as an infinitely dense point in space with infinitely high entropy and an infinite curve in space- time that has an event horizon where, once any electromagnetic radiation passes it is red shifted into oblivion. There is also a mathematical definition of a singularity which is not the same as the physical one. The mathematical definition of a singularity is “A point at which the derivative does not exist for a given function but every neighborhood of which contains points for which the derivative exists. Also called singular point.”

 

[Orodruin]

From what I understand, which you may think isn’t much, the universe is a flat 3+1 dimensional plane

Not "not so much" as much as "wrong". The spatial part of the Universe may be flat, but this does not mean that the Universe is flat as a 3+1-dimensional Lorentzian manifold.

I understand a singularity as an infinitely dense point in space with infinitely high entropy and an infinite curve in space- time that has an event horizon where, once any electromagnetic radiation passes it is red shifted into oblivion.

This is also not correct. The Big Bang "singularity" is more like a moment in time which is in everyone's past than it is a point in space. The same goes for the singularity of the Schwarzschild solution - it is more like a moment in time which is in the unavoidable future of anyone who passes the event horizon.

I would repeat the advice of @phinds to learn what the theory actually says before worrying about the implications that can be drawn from it. Otherwise what you are doing is just conjecture based upon possible misinterpretations.

 

[Aidan345733]

Those previous definitions are correct and I understand what you are saying and I also understand that once you pass the event horizon the singularity is all around you there is absolutely no direction that you can go at any speed that would lead away from that singularity and that is the problem. If the Big Bang happened because of a sudden drop in entropy then the singularity would have had to have been disrupted in order for any expansion to happen and, so since we can’t measure anything before the plank time we have no way to know how this happens.

 

[phinds]

The Hilbert hotel paradox ...

It is not a paradox, it's simply an explanation/description of how something infinite can expand.

Look Aidan, we're not trying to give you a hard time here, we're just giving you the best advice we can which is that you learn some actual cosmology before making such speculations, which are based on what you will come to understand are misconceptions. Why did you join a forum full of people who know what they are talking about if you are not going to take our advice?

EDIT: our posts crossed. I see that you know more than your OP suggested, but again, you have some misconceptions.

 

[Aidan345733]

I appreciate the advice but at my point in life I do not have a true opportunity to really learn any cosmology or astronomy. It could help if you know where I was coming from in originally creating this post. I think that my misconceptions came from an idea in string theory, which I understand is not a actual theory because it can never be tested in any practical ways, that stated they there could be up to 10^500 universes and I wanted other people’s opinions on those questions that could arise from this possibility. I thought it to be a fun mind game that could get people thinking. Thank you to everyone for helping show flaws to this idea and to really help show how far I still have to learn and grow.

 

[Orodruin]

Those previous definitions are correct and I understand what you are saying and I also understand that once you pass the event horizon the singularity is all around you there is absolutely no direction that you can go at any speed that would lead away from that singularity and that is the problem.

I am sorry, but you saying that you understand when you are clearly not understanding is a problem for you being able to actually learning something new. The singularity in a Schwarzschild black hole is not "all around you" in any sense of the word. It is an event that will come to pass in your future.

 

[phinds]

I appreciate the advice but at my point in life I do not have a true opportunity to really learn any cosmology or astronomy. It could help if you know where I was coming from in originally creating this post. I think that my misconceptions came from an idea in string theory, which I understand is not a actual theory because it can never be tested in any practical ways, that stated they there could be up to 10^500 universes and I wanted other people’s opinions on those questions that could arise from this possibility. I thought it to be a fun mind game that could get people thinking. Thank you to everyone for helping show flaws to this idea and to really help show how far I still have to learn and grow.

An admirable goal, but unfortunately, when it is based on speculation it is not in keeping with the raison d'etre of this forum, which is to discuss mainstream science, not speculate about what might be.

 

[pinball1970]

I appreciate the advice but at my point in life I do not have a true opportunity to really learn any cosmology or astronomy.

Some overview books on this and decent web sites too. Ill leave those references to the other guys who know this stuff though, I don't want to steer you in the wrong direction.

 

[PeroK]

I appreciate the advice but at my point in life I do not have a true opportunity to really learn any cosmology or astronomy.

Here's a really good Insight on the expanding universe:

https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/

 

[Aidan345733]

This does help clear up misconceptions and I may not quite yet know the math but I do understand what the author is saying and where I got my misconceptions from.

 

[Aidan345733]

To Orodruin here is a link to an extremely basic video explaining my my previous comment about a singularity, whatch it all the way through and you will see what I mean. The information in the video came from a book written by Neil DeGrasse Tyson and is fairly accurate.

 

[Aidan345733]

And no I don’t get all of my information from non credible sources, like YouTube.

 

[Orodruin]

To Orodruin here is a link to an extremely basic video explaining my my previous comment about a singularity, whatch it all the way through and you will see what I mean. The information in the video came from a book written by Neil DeGrasse Tyson and is fairly accurate.

First of all, when you link an 8 minute video to give a specific argument, you should refer to where in the video what you want to refer to occurs and not expect people to have to see the entire video.

Second, the video (and the books of DeGrasse Tyson) is clearly a popularised account and you cannot expect it to give you very accurate information. Popular science is most often filled with "wow"-factors rather than accuracy. Already in the first few minutes of the video, I note several factual inaccuracies and over-simplifications and it continues on from there.

Edit: Long story short: Do not trust that video.

 

[Aidan345733]

I know it is grossly simplified and was just using it to show that even in main stream science you need a way to get the public interested. Once you cross the event horizon the gravitational pull is so strong it curves space tome to such an extent that there is no way to escape. A singularity it the infinitely small point of highest gravity and once you cross the horizon you can’t escape it. That is what I meant.

 

[Orodruin]

Once you cross the event horizon the gravitational pull is so strong it curves space tome to such an extent that there is no way to escape.

The video is directly wrong about basically everything they say about what happens when you fall into a black hole. In particular, I find it amusing that they first assume the existence of a (unphysical) rocket that can go faster than the speed of light and then get it wrong in regards to whether or not that rocket would be able to escape the black hole (it would).

A singularity it the infinitely small point of highest gravity and once you cross the horizon you can’t escape it. That is what I meant.

Again, this is not a correct view. The singularity is not a point in space. It is certainly not "all around you". It is much more similar to a moment in time and trying to avoid it would be like trying to avoid midnight - it comes whether you want it to or not. I suggest you forget everything you saw and heard in that video if you want any chance of building an accurate picture of what goes on in a black hole.

 

[Aidan345733]

Ok then.

 

[phinds]

@Aidan345733 I empathize with your position. I spent about 2 years thinking that, because I had read NUMEROUS pop-sci books and watched tons of TV shows w/ reputable physicists like NDG Tyson and many others, that I had at least some rudimentary understanding of cosmology. It took at least another year to unlearn all that crap and come to a full-gut realization that pop-sci is JUST entertainment, not science, and this is true even when the presenters are reputable physicists (who, by the way, very frequently say stuff in their pop-sci presentations that they know damned good and well would get them laughed out of the room at a convention of actual physicists).

 

[pinball1970]

@Aidan345733 I empathize with your position. I spent about 2 years thinking that, because I had read NUMEROUS pop-sci books and watched tons of TV shows w/ reputable physicists like NDG Tyson and many others, that I had at least some rudimentary understanding of cosmology. It took at least another year to unlearn all that crap and come to a full-gut realization that pop-sci is JUST entertainment, not science,).

lots references to pop science on pf. A a thread would be a good idea I think. Book status: science pop sconce or in between.

 

[pinball1970]

Damn it. Science! On bus agin

 

[Joseph de Nicola]

Aidan345733 wrote:

"I also know this is rather unlikely and find it fun to play out different scenarios that may be a fun possibility but my biggest question is, if in the beginning the entire universe was condensed down into a singularity then that would, by definition be a black hole and we don’t see new universes spontaneously popping out of the millions of existing black holes in our universe."Imagine that in the same way a star with enough mass eventually collapses into a black hole, that it would take the combined mass of all the black holes in this universe to collapse into a new big bang. That would explain why new universes aren't popping out of all the black holes. But the black holes are constantly merging. The SMBH at the center of our Milky way can be thought of as a member of a binary black hole, with its partner being the SMBH at the center of Andromeda. In around 4.5 billion years they will merge. Perhaps at a certain point, enough SMBHs will accumulate to create such a strong gravitational force that it begins to reverse the effects of the inflationary period that began with big bang. You see where this is going. Imagine the entire universe eventually condensed into one huge black hole mass, with a few stray atoms some light years away, waiting for those last few bits of mass to join it to achieve critical mass, where that black hole collapses into a singularity and then bounces into a new bang.

Also, there is enough good mathematics supporting various multiverse scenarios that I don't think one can assume that this or any universe is infinite. Space is curved, therefore, one of the three proposed models of the universe's shape, positive curvature, would dictate that the universe is spherical, a very large bubble that only looks flat to us in the same way the Earth seems flat while we are walking on it - because it's so vast.

"If the universe has a positive curvature, it’s a closed universe. A two-dimensional model of such a universe would look like a sphere. It’s impossible to have parallel geodesics (straight lines on a curved surface) -- the two lines will cross at some point. In a closed universe, there is enough matter to reverse expansion. Eventually, such a universe will collapse on itself. A closed universe is a finite universe -- it will only expand to a certain size before collapsing."

 

[Drakkith]

Imagine that in the same way a star with enough mass eventually collapses into a black hole, that it would take the combined mass of all the black holes in this universe to collapse into a new big bang.

This is not supported by mainstream physics. At best there may be a few highly theoretical models which make vague predictions concerning this, but in no way is this a well supported idea. One problematic thing that comes to mind is that this says nothing about all the matter and energy not locked up in black holes. All that gas, dust, and radiation roaming about contributes an awful lot to the mass of the universe. Another thing is that we don't even know how many black holes there are in the observable portion of the universe, let alone the rest of the universe.

But the black holes are constantly merging. The SMBH at the center of our Milky way can be thought of as a member of a binary black hole, with its partner being the SMBH at the center of Andromeda. In around 4.5 billion years they will merge.

Unlikely. The SMBH at the center of our universe is smaller in size than our solar system. The chances of another black hole of comparable size getting close enough to it to merge is extremely remote. Even if they enter into a closer orbit around their barycenter, the time it would take for gravitational radiation to bleed off enough energy for their orbits to carry them close enough to merge might be longer than the time it takes them to evaporate via hawking radiation.

Perhaps at a certain point, enough SMBHs will accumulate to create such a strong gravitational force that it begins to reverse the effects of the inflationary period that began with big bang. You see where this is going. Imagine the entire universe eventually condensed into one huge black hole mass, with a few stray atoms some light years away, waiting for those last few bits of mass to join it to achieve critical mass, where that black hole collapses into a singularity and then bounces into a new bang.

I assume you're talking about something similar to the 'big bounce' scenario, where the universe reverses its expansion and collapses in on itself, only to rebound at a certain point. If so, you should know that black holes have nothing to do with this beyond contributing their normal mass. Just like regular matter and dark matter.

Also, there is enough good mathematics supporting various multiverse scenarios that I don't think one can assume that this or any universe is infinite.

On the contrary, the idea that the universe is infinite in size is very well supported by math, while multiverse theories have only the vaguest mathematical treatment. Basically, there isn't enough good math to support any multiverse theory over any of the others, let alone over a single-universe theory (aka the standard model of cosmology). Going beyond the math, there isn't a shred of evidence from observations or experiments supporting multiverse theories over the standard model of cosmology at this time.

Space is curved, therefore, one of the three proposed models of the universe's shape, positive curvature, would dictate that the universe is spherical, a very large bubble that only looks flat to us in the same way the Earth seems flat while we are walking on it - because it's so vast.

It's possible, but there have been no measurements made to date that have found any deviation from a flat shape. Note that the shape of the universe and the curvature of space as usually talked about in GR are related, but not the same thing. Space can be curved locally while the universe can be flat. An analogy (and only an analogy) is to think of a large sheet of thin metal with a hammer divot in the middle of it. Locally, the surface of the metal might be heavily curved near the divot. But the overall shape is still a flat sheet. Unfortunately it is very difficult to go from a 2d analogy to the 4d model, so don't expect everything to make perfect sense without a serious amount of time and effort spent learning the details of GR and cosmology.