Find the Age of the Universe when Matter and Radiation densities were equal

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Discussion Overview

The discussion revolves around the effects of black holes on spacetime, gravitational dynamics within galaxies, and the nature of dimensions in theoretical physics. Participants explore concepts related to general relativity, the influence of black holes on nearby stars, and speculative theories about the dimensionality of the universe.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that black holes warp time and space, potentially creating localized effects that could lead to misconceptions about the age of the universe in different regions.
  • Others argue that the "time warping" caused by black holes is a local phenomenon, primarily affecting observations near the black hole and not extending significantly beyond that region.
  • There is a question about the gravitational influence of black holes on the dynamics of galaxies, with some participants noting that while black holes contribute to the total mass, their effect diminishes with distance.
  • Participants discuss the dimensionality of the universe, with some asserting that current theories primarily consider a four-dimensional model, while others mention ten-dimensional models as speculative without empirical evidence.
  • Speculation arises regarding the nature of spacetime, with one participant suggesting a liquid state theory, while others clarify that gravitational waves already influence spacetime.
  • There is a request for clarification on formulas related to the effects of black holes and gravitational time dilation, with references to general relativity as a framework for understanding these concepts.

Areas of Agreement / Disagreement

Participants express differing views on the extent of black holes' influence on spacetime and gravitational dynamics, with no consensus reached on the implications of speculative theories regarding dimensions or the nature of spacetime.

Contextual Notes

Limitations include the speculative nature of theories regarding higher dimensions and the liquid state of spacetime, as well as the dependence on interpretations of general relativity and gravitational effects.

FallenGod
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The universe is believed to be 13.8 billion years old and at least 45 billion light-years in radius. Now there is also a black hole at the center of our galaxy, with my basic understanding of black holes I understand that this would warp time and space, is it possible that it's warped so much that we are living in a small pocket of the universe that is 13.8 billion years old and the rest of the universe at least the parts not affected by any influence of black holes are older?
 
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FallenGod said:
The universe is believed to be 13.8 billion years old and at least 45 billion light-years in radius. Now there is also a black hole at the center of our galaxy, with my basic understanding of black holes I understand that this would warp time and space, is it possible that it's warped so much that we are living in a small pocket of the universe that is 13.8 billion years old and the rest of the universe at least the parts not affected by any influence of black holes are older?
No, you misunderstand the effects. BH "time warping" is a purely local phenomenon and is only meaningful when considered relative to an observer far away from the BH and do not affect that observer, just his observations of what he "sees" in the vicinity of the BH.
 
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I'm sorry to ask but could you explain more? I fear I still misunderstand why it wouldn't be true. I believe you because you would know more than me but in my mind it still seems as if a local phenomenon could still act the way I said. Unless the "time warping" is at the closest points of a black hole and doesn't extend as far as it's other gravitational effects?
 
FallenGod said:
I'm sorry to ask but could you explain more? I fear I still misunderstand why it wouldn't be true. I believe you because you would know more than me but in my mind it still seems as if a local phenomenon could still act the way I said. Unless the "time warping" is at the closest points of a black hole and doesn't extend as far as it's other gravitational effects?
That's correct. The "time warping" is local to the region of the BH. The gravitational effect extends, in theory at least, to infinity, but both the power of the gravity and the affect of the "time warping" drop off precipitously as you move away from the BH.
 
Not only a black hole but any massive object changes the curvature of space, (locally).
This results in gravity as described by general relativity.
However the amount of gravity is only significant close to the massive object, it becomes nearly zero at any appreciable distance.
The Milky way's SMBH does have a number of very nearby stars orbiting it, but it has no effect on more distant stars.
 
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Is there a formula that can be used to find the area of affect of the "time warping"? Or is it just assumed the limit is the edge of the BH?

So is the Milky Way not really orbiting a black hole but just moving in tandem with it?
 
FallenGod said:
Is there a formula that can be used to find the area of affect of the "time warping"? Or is it just assumed the limit is the edge of the BH?
https://en.wikipedia.org/wiki/Gravitational_time_dilation

So is the Milky Way not really orbiting a black hole but just moving in tandem with it?
The objects in the Milky way, NOT the milky way itself, are orbiting the center of the galaxy. The BH is at the center of the galaxy but only accounts for something like 1% of the total mass of the galaxy so contributes little to the orbital dynamics other than to that of the stars VERY close into it.
 
That makes a lot of sense to be honest. But i have to ask. Are we assuming a 4 dimensional universe or a 10 dimensional universe?
 
The currently accepted theory of gravity is general relativity which models spacetime in terms of 3 spatial dimensions and 1 time dimension.
10 dimensional models and others belong to string theories, where the additional dimensions are very small in scale.
They apply mostly (if they are correct), to consideration of subatomic scale entities, not to very large objects like galaxies.
 
  • #10
FallenGod said:
That makes a lot of sense to be honest. But i have to ask. Are we assuming a 4 dimensional universe or a 10 dimensional universe?
10 dimensional universes are PURE speculation and there is zero empirical evidence for them.
 
  • #11
phinds said:
The objects in the Milky way, NOT the milky way itself, are orbiting the center of the galaxy. The BH is at the center of the galaxy but only accounts for something like 1% of the total mass of the galaxy so contributes little to the orbital dynamics other than to that of the stars VERY close into it.
Would the "little" that it contributes to the orbital dynamics of further-out-stars be the fact that they orbit around the SMBH at all?
 
  • #12
I think the accepted idea is that galaxies form from collapsing gas and dust clouds that have some angular momentum to begin with.
A black hole in the center is not a prerequisite, but most galaxies end up that way
 
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  • #13
Comeback City said:
Would the "little" that it contributes to the orbital dynamics of further-out-stars be the fact that they orbit around the SMBH at all?
They orbit around the center of the galaxy based on the total mass of the galaxy. The BH contributes to that total.
 
  • #14
I researched the 10 dimensional universe and wow I didn't know it was just speculation. I always thought that since the galaxy had a black hole in the center that we were affected by it. I heard of a theory on spacetime being a liquid state, a quantum gravity theory to be exact, but again just personal speculation, if spacetime were in a liquid state would gravitational forces send force waves out?
 
  • #15
FallenGod said:
I researched the 10 dimensional universe and wow I didn't know it was just speculation. I always thought that since the galaxy had a black hole in the center that we were affected by it. I heard of a theory on spacetime being a liquid state, a quantum gravity theory to be exact, but again just personal speculation, if spacetime were in a liquid state would gravitational forces send force waves out?
Gravitational forces ALREADY send out waves. Google LIGO
 
  • #16
I need to say more when I say things lol. I didn't mean waves as in gravitational forces like the usual but as in waves that influence spacetime. I can't put it into words but rather pictures...
 
  • #17
FallenGod said:
I need to say more when I say things lol. I didn't mean waves as in gravitational forces like the usual but as in waves that influence spacetime. I can't put it into words but rather pictures...
Gravitational wave DO influence spacetime.

EDIT: and by the way, I'd suggest you drop the "spacetime as a liquid" concept.
 
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  • #18
is it not a liquid? Or is that just another theory that can't be proven? Does it just exist?
 
  • #19
FallenGod said:
is it not a liquid? Or is that just another theory that can't be proven? Does it just exist?
Google Michelson–Morley experiment
 
  • #20
Alright I'll google that. Do you have any clue about why the name of this thread was changed?
 
  • #21
FallenGod said:
Alright I'll google that. Do you have any clue about why the name of this thread was changed?
Sometimes the mods change the thread title so that other viewers have a better idea of what the thread is about.
You could connect any of them for an explanation, they aren't monsters.
 
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  • #22
Oh that's actually cool. I don't know how to do what the question is or even what it all means though which is the major reason I was asking.
 
  • #23
FallenGod said:
Is there a formula that can be used to find the area of affect of the "time warping"?
Yes there is, it is called general relativity.
If you want the intricate details there are people here who can explain that better than I can.
 
  • #24
FallenGod said:
Alright I'll google that. Do you have any clue about why the name of this thread was changed?
No, you should PM a moderator and ask.

EDIT: oops, I missed a couple of posts and didn't realize rootone already told you that.
 
  • #25
So Einstein's field equations would be used?
 

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