How would we know the difference between an expanding universe and a collapsing one?

P

Parilyz

Registered Member
Disclaimer: I'm an amateur just looking for some insight.
Here's my idea I want to share:
Let's say that our universe was inside a black hole (I know, some other people have already started exploring this). If time or maybe space were being stretched inwards, if we were on the slope of the inward stretching space within, from our perspective, would the universe around us not appear as though it were expanding? How would we know? If space itself were stretching along an exponential curve inside said black hole, would we be able to use any kinds of observations to differentiate from an expanding universe? Could each black hole be a 'house' for new universes? Could the 'everything' (not sure if it should be called a dimension, might be the wrong word) be an infinite amount of universes inside black holes residing in subsequent universes? Like those Russian dolls, but infinite in either direction? I often think of fractal patterns found in nature and it makes me wonder if the universe itself and it's subsequent construction is not like the Mandelbrot - that we could 'zoom in' to a black hole, find another universe that had it's own black holes just like we see in our universe, and repeat down the 'zoom line' forever?
 
Parilyz said:
Disclaimer: I'm an amateur just looking for some insight.
Here's my idea I want to share:
Let's say that our universe was inside a black hole (I know, some other people have already started exploring this). If time or maybe space were being stretched inwards, if we were on the slope of the inward stretching space within, from our perspective, would the universe around us not appear as though it were expanding? How would we know? If space itself were stretching along an exponential curve inside said black hole, would we be able to use any kinds of observations to differentiate from an expanding universe? Could each black hole be a 'house' for new universes? Could the 'everything' (not sure if it should be called a dimension, might be the wrong word) be an infinite amount of universes inside black holes residing in subsequent universes? Like those Russian dolls, but infinite in either direction? I often think of fractal patterns found in nature and it makes me wonder if the universe itself and it's subsequent construction is not like the Mandelbrot - that we could 'zoom in' to a black hole, find another universe that had it's own black holes just like we see in our universe, and repeat down the 'zoom line' forever?
Click to expand...
We know our universe is expanding by observations of distant galaxies, standard candles within those galaxies and also the CMBR.
Current consensus is that our Universe is 13.8 billion years old and is spatially infinite.
In 1998 it was discovered that the rate of acceleration was increasing and in the last few weeks it looks like the Cosmological constant is probably not a constant.
It is estimated that the entire universe is much larger than the observable universe.
IF all of that is happening inside a black hole, how could we tell?
 
Parilyz said:
Disclaimer: I'm an amateur just looking for some insight.
Here's my idea I want to share:
Let's say that our universe was inside a black hole (I know, some other people have already started exploring this). If time or maybe space were being stretched inwards, if we were on the slope of the inward stretching space within, from our perspective, would the universe around us not appear as though it were expanding? How would we know? If space itself were stretching along an exponential curve inside said black hole, would we be able to use any kinds of observations to differentiate from an expanding universe? Could each black hole be a 'house' for new universes? Could the 'everything' (not sure if it should be called a dimension, might be the wrong word) be an infinite amount of universes inside black holes residing in subsequent universes? Like those Russian dolls, but infinite in either direction? I often think of fractal patterns found in nature and it makes me wonder if the universe itself and it's subsequent construction is not like the Mandelbrot - that we could 'zoom in' to a black hole, find another universe that had it's own black holes just like we see in our universe, and repeat down the 'zoom line' forever?
Click to expand...
Yes, I think Pinball1970 's "How could we tell?" point is what divides science from metaphysical speculation. I suppose it's a matter of aesthetic preference, really, whether one wants to imagine such possibilities or whether one decides to stick to what can be inferred from observable phenomena. In particle physics, string theory is a bit the same, suffering from the drawback that none of its speculations seem to lead to any means of being tested to see if nature is really like that or not. Some people are drawn to the idea of multiple universes as a way of dealing with the issue of why the physical constants (in our universe, as it were) have the values they do, since one could envisage a whole series of universes exploring all the possible permutations of values for them. (Personally, I'm not persuaded this is a problem.)

I don't know enough about cosmology to comment in detail on your idea about "inward stretching" of space, though. Has not Carlo Rovelli gone into this a bit?
 
Parilyz:
Parilyz said:
Here's my idea I want to share:
Let's say that our universe was inside a black hole (I know, some other people have already started exploring this).
Click to expand...
If that were the case, then everything in the universe would be moving inexorably towards the centre of the hole. Instead, we see the universe expanding in all directions.
Parilyz said:
If time or maybe space were being stretched inwards, if we were on the slope of the inward stretching space within, from our perspective, would the universe around us not appear as though it were expanding?
Click to expand...
If a black hole has constant mass, the spacetime around it is essentially static. It does not "stretch". Unless I'm misunderstanding what you mean, perhaps. What do you actually mean?
Parilyz said:
If space itself were stretching along an exponential curve inside said black hole, would we be able to use any kinds of observations to differentiate from an expanding universe?
Click to expand...
Why would space stretch inside a black hole? What would cause the stretching? You'd need to add or subtract mass, wouldn't you?
Parilyz said:
Could each black hole be a 'house' for new universes?
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Who knows? Do you think it could be? If so, why? I'm not sure what "a 'house' for new universes" even means.
Parilyz said:
Could the 'everything' (not sure if it should be called a dimension, might be the wrong word) be an infinite amount of universes inside black holes residing in subsequent universes?
Click to expand...
Black holes all have finite mass. Infinite universes, on the other hand, would have infinite mass.
Parilyz said:
I often think of fractal patterns found in nature and it makes me wonder if the universe itself and it's subsequent construction is not like the Mandelbrot - that we could 'zoom in' to a black hole, find another universe that had it's own black holes just like we see in our universe, and repeat down the 'zoom line' forever?
Click to expand...
Imagination is all well and good, but at some point the rubber has to hit the road. Is there any physical theory that you're aware of which suggests that what you imagine could actually be the case? Or are you just tossing the idea out there to see if somebody else can make some sense of it?
 
James R.:

dd we are try to engineer the sneqier 7

Yeah, this should purchase me a life-time membership herein.
 
Moderator note: Mr. G has been warned for off-topic posting, and more generally for just cluttering up threads with valueless posts.

Due to accumulated warning points, we won't be seeing him again for a couple of weeks, at least.
 
Is the universe reducible in picture to quantum physics? And, alternatively, expandible in picture to gravity physics? Newton's apple fell into a pointedly closing, narrowing, barrier system, a contraction, to quantum physics. BUT, it was falling TOWARD an opening system, an accelerating expansive system and opening picture, of gravity physics. When you advance forward in space and time does the universe open -- accelerate in expansion -- before you in picture and futures or collapse, contracting into points, in closures and pasts (aka histories)? Does it open behind you or collapse in closures to a point (to points)? The opening, expansive, systemic to the infinity and infinities of gravity versus the relative finite but very real 'Alice in Wonderland: Through The Looking Glass' illusions (entropy, inertia) of closed systemic quantum physics.
 
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Parilyz said:
Disclaimer: I'm an amateur just looking for some insight.
Here's my idea I want to share:
Let's say that our universe was inside a black hole (I know, some other people have already started exploring this). If time or maybe space were being stretched inwards, if we were on the slope of the inward stretching space within, from our perspective, would the universe around us not appear as though it were expanding? How would we know? If space itself were stretching along an exponential curve inside said black hole, would we be able to use any kinds of observations to differentiate from an expanding universe? Could each black hole be a 'house' for new universes? Could the 'everything' (not sure if it should be called a dimension, might be the wrong word) be an infinite amount of universes inside black holes residing in subsequent universes? Like those Russian dolls, but infinite in either direction? I often think of fractal patterns found in nature and it makes me wonder if the universe itself and it's subsequent construction is not like the Mandelbrot - that we could 'zoom in' to a black hole, find another universe that had it's own black holes just like we see in our universe, and repeat down the 'zoom line' forever?
Click to expand...
This is an interesting thought experiment, I guess. I’m thinking that if we were living within such a “universe,” like Pinball mentions above, we’d be able to tell it’s expanding the same way we do now - by observing how space behaves. A universe inside of a black hole would not change the “evidence” of expansion, but other things could be different.
 
My big problem is that space is flexibly shapeable because of gravity. Time isn't, it will lose or gain photo-frames, lose or gain photon streams, ending up looking like a Cantor set:

en.wikipedia.org

Cantor set - Wikipedia

en.wikipedia.org en.wikipedia.org
 
Wizard of Whatever said:
Simple one seems to be red shift vs. blue shift.
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Not as simple as you might think. You see a black hole from the outside-in, or think you are seeing it from the outside-in, and think there probably must be a singularity at the center of it. You advance toward the event horizon and find it widening out in accelerating expansion, an accelerating opening up up of space and time universe. A universe has systematically closed behind you. Another universe has opened, is opening in accelerating expansion, before you from an event horizon you never actually realize you've surpassed until you look and see the collapsed cosmological constant of Planck (BC/BB) Horizon, the horizon singularity, you've always noted as the distant beginning and end point of the observable universe.

You did not, you could not possibly, hit the black hole directly or go against the flow without being destroyed regardless of your shielding, the direction of the streaming space and time through what you now find to be a natural wormhole, however temporary or long lasting, between universes. You never got away from the red shifting of an opening universe picture before you from the horizon point of singularity, a closing universe picture to the horizon point of singularity behind you.

You could achieve essentially the same physics of universe opening before you, the same red shifting picture of accelerating expansion of universe, by the simple means of traveling aboard a spaceship under a constant of acceleration, a ship powering constantly to anywhere through future past histories opening up before you, the past future histories always out of the distant collapsed cosmological constant horizon, or at and in the eye of the beholder like a Flatland photo-frame artistic work "Mandelbrot Set."
 
Add post #17:

Have you ever really looked at a picture, particularly a landscape painting, where it, its universe, opens out from a 0-point horizon to you in view? Where if went into the picture that universe would continuously accelerate in expansion, in universe opening to you, from a singularity of 0-point horizon. You might realize that there are an infinity of such 0-points to an infinity of such universe pictures, such future past histories that would accelerate in expansion (accelerate in opening).

A universe traveler might could travel from the Milky Way galaxy to the Andromeda galaxy in possibly months' time. From the middle out, Andromeda galaxy exists observably to the Earth bound observer, 2025CE, as Andromeda 2.3 million years BCE to the Milky Way's 2025CE. The traveler space and time travels from Andromeda 2.3 million years BCE, as observed from the orbit of Earth, to Andromeda 2025CE . . . crossing forward in space and time 2.3 million years of Andromeda's future past histories, to Andromeda 2025CE, in the passage time clocked aboard ship of a few months. If you can really think and realize, a realized passage at less than the speed of light, the 2.3 million years (light years) and, additionally, a few months. The few months transit space-time, forward in space and time over the 2.3 million light years, meaning transit at less than the speed of light. The sighting of the Milky Way galaxy having gone from 2025CE to 2.3 million years BCE, having now fallen behind in space-time, being the faster than the speed of light observation. A straight trade off of observed universes, of spaces, of times, one for one. Accelerating expansion of universe picture, of Andromeda picture, forward out of a 0-point Horizon singularity of an infinity of such 0-point singularities. Accelerating contraction of Milky Way picture, rearward in space and time . . . toward a 0-point Horizon singularity of an infinity of such 0-point singularities.
 
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Atlan0001 said:
Add post #17:

Have you ever really looked at a picture, particularly a landscape painting, where it, its universe, opens out from a 0-point horizon to you in view? Where if went into the picture that universe would continuously accelerate in expansion, in universe opening to you, from a singularity of 0-point horizon. You might realize that there are an infinity of such 0-points to an infinity of such universe pictures, such future past histories that would accelerate in expansion (accelerate in opening).

A universe traveler might could travel from the Milky Way galaxy to the Andromeda galaxy in possibly months' time. From the middle out, Andromeda galaxy exists observably to the Earth bound observer, 2025CE, as Andromeda 2.3 million years BCE to the Milky Way's 2025CE. The traveler space and time travels from Andromeda 2.3 million years BCE, as observed from the orbit of Earth, to Andromeda 2025CE . . . crossing forward in space and time 2.3 million years of Andromeda's future past histories, to Andromeda 2025CE, in the passage time clocked aboard ship of a few months. If you can really think and realize, a realized passage at less than the speed of light, the 2.3 million years (light years) and, additionally, a few months. The few months transit space-time, forward in space and time over the 2.3 million light years, meaning transit at less than the speed of light. The sighting of the Milky Way galaxy having gone from 2025CE to 2.3 million years BCE, having now fallen behind in space-time, being the faster than the speed of light observation. A straight trade off of observed universes, of spaces, of times, one for one.
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This is hard science sir.
 
Pinball1970 said:
This is hard science sir.
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And a 1-dimensional statement ("This is hard science sir") from 1-dimensional thought and thinking. Andromeda doesn't exist 2.3 million years ago regardless of observation, sir! It exists, NOW, in some future observation from an Earth-bound observer! Travelers would not space and time travel to the relative observation from the Earth-bound observer! That, sir, is the hard science, don't you know!

Andromeda would be displaced, by the traveler, forward in space and time from the horizons, from the singularity, behind it. The Milky Way would be displaced, by the traveler, rearward in space and time toward the horizons, toward the singularity, behind it. That is the hard science of "Cosmology", sir!
 
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