Does the Universe always have the same mass, or can it leak into other realms?

In summary, the conversation discusses various concepts related to the beginning of the universe, including the singularity before the Big Bang, the first law of thermodynamics, and the possibility of mass leaking out of the universe into other realms. The idea of other universes and the total energy of the universe is also mentioned. Some disagreement arises regarding the use of General Relativity to model the beginning of the universe and the formation of black holes. One user offers insight into the formation of black holes, while another criticizes the speculation about other universes.
  • #1
Gaz1982
64
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Forgive me if some of my question around here sound trite or have been covered before, I'm not a physicist, but I do have a great layerperson's interest and I feel like I need to move to the next level (beyond TV programmes I mean I mean)

So I have an opening question. Of course the "singularity" before the Big Bang was not infinitely dense or the Universe itself would still be infinitely dense; so am I to presume that consistent with the first law of thermodynamics, the Universe has always had exactly the same mass, and always will?

Unless of course, it is not a closed system and mass can "leak" out into other realms?

Thanks
 
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  • #2
The universe has always had the same TOTAL energy. The temperatures just after the big bang were too high for matter to form. But yes you are right.
Oh, and what other 'realms' could there be?
And why couldn't the universe have been infinitely dense at the big bang. Infinite density doesn't necessarily mean infinite mass( in which case you would be right) but it might also mean finite mass in an infinitesimal volume. So the universe could have been infinitely dense and the expansion of the universe means that you have regions that aren't infinitely dense.
 
  • #3
UncertaintyAjay said:
The universe has always had the same TOTAL energy. The temperatures just after the big bang were too high for matter to form. But yes you are right..

Cheers

Oh, and what other 'realms' could there be?

Other Universes. (Speculating)

And why couldn't the universe have been infinitely dense at the big bang. Infinite density doesn't necessarily mean infinite mass( in which case you would be right) but it might also mean finite mass in an infinitesimal volume. So the universe could have been infinitely dense and the expansion of the universe means that you have regions that aren't infinitely dense

Sure, OK. But infinitesimal volume makes no more sense to me than infinite mass. It gives us the spectre of the physical singularity.
 
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  • #4
I disagree with UncertaintyAjay's post. As indicated in the other thread the OP started, the total energy of the universe can't be easily defined. From what I understand there are some (most vocally Lawrence Krauss) who like to make statements about the total energy of the universe being zero, with the energy lost in the expansion "siphoned" into gravitational potential energy, but it's hardly the standard approach, and you are likely to find more people regarding that as muddling the issue - as indicated in that link I gave in the other thread.Similarly, singularities and infinities tend to suggest limitations to the theory, rather than actual physical reality. If you model the evolution of the universe backwards in time using General Relativity you end up with an infinitely dense singularity - but this is just an indication that you shouldn't try and use GR to model that region. And indeed, the Big Bang theory doesn't do that. It focuses on the expansion from a hot, dense state to what we see now, but claims no predictive power as to the beginning or what happened before (assuming it even makes sense to ask).
 
  • #5
But why doesn't infinitesimal volume not make sense? That's how black holes are formed. They shrink to incredibly small singularities. And I'm speculating too, but if there were other universes, then wouldn't the total energy in all the universes( combined) be the same, which I reckon amounts to the same thing.
 
  • #6
The singularities are pretty much what you get when you try to divide by zero. It's where the function you used to describe something stops being defined. It's a stretch to claim that it's has got any physical meaning.

Both BB and black hole singularities are the extrapolations of GR to a region where it is no longer applicable. We'd need a quantum theory of gravity, that is, a theory that takes into account quantum interactions, to model those regions.
 
  • #7
UncertaintyAjay said:
But why doesn't infinitesimal volume not make sense? That's how black holes are formed. They shrink to incredibly small singularities.
No, that is NOT how they are formed, it is how the math says they END UP, which is not the same thing at all.
And I'm speculating too, but if there were other universes, then wouldn't the total energy in all the universes( combined) be the same, which I reckon amounts to the same thing.
Pointless speculation as far as anything practical is concerned. If there are other universes they are not in causal contact with ours so they are irrelevant.
 
  • #8
Bandersnatch said:
I disagree with UncertaintyAjay's post.
Me too.
 
  • #9
Enlighten me then phinds, how are they formed?
 
  • #10
I'm no phinds, but I can try to enlighten.

All you need to do to get a BH is concentrate enough mass in a sphere of a radius lower than its Schwartzschild radius. That's when the event horizon forms and you've got a black hole. Whatever happens to the mass trapped inside is irrelevant.

In fact, there were some recent papers suggesting the mass inside may bounce back in a finite amount of time, and emerge from the event horizon. Make a forum search for "planck stars" if you're interested.
 
  • #11
Thanks bandersnatch
 
  • #12
Oh and phinds, you seem to turn up in a lot of threads in which I post( nothing wrong with that) What I do take issue with is the fact that not one of your replies towards me has been politely phrased, or , in fact , told me anything of use.While both you and Bandersnatch corrected me( and I accept that I was wrong) only Bandersnatch had anything of value to add . You seem to rejoice in criticizing others and don't seem to understand that making mistakes is a part of a learning process. So please, be a little less brusque in the future and offer something constructive.
 
  • #13
Hey, don't be too harsh on phinds. His grumpy streak is legendary among PF users. It's just a something we have to live with. ;)
 
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  • #14
Yeah, no, I get that he knows a lot of stuff, and understands things really well, but its time he became more polite. And seriously, I don't mind the criticism, its just that I don't learn much from his comments apart front the fact that I'm wrong.
 
  • #15
[Because E="UncertaintyAjay, post: 4910030, member: 529142"]But why doesn't infinitesimal volume not make sense? That's how black holes are formed. They shrink to incredibly small singularities. And I'm speculating too, but if there were other universes, then wouldn't the total energy in all the universes( combined) be the same, which I reckon amounts to the same thing.[/QUOTE]

Because a finite matter in a practically infinitely small space sounds like it breaks every principle imaginable
 
  • #16
Yeah, forget the stuff I said I was wrong. But I'll take another go anyway( corrcet me if I'm wrong) but yes, it dies violate every principle, which is why relativity can't model singularities.
 
  • #17
I can't even imagine one in practice.
 
  • #18
UncertaintyAjay said:
Yeah, no, I get that he knows a lot of stuff, and understands things really well, but its time he became more polite. And seriously, I don't mind the criticism, its just that I don't learn much from his comments apart front the fact that I'm wrong.
I do apologize for the briskness of my replies. I don't mean to be rude in any way, I just try to get things across briefly and I don't expand much, if at all, many of the times, which is an unfortunate tendency that I fight, mostly as a losing battle. I also agree w/ your observation that I tend to be more negative than is sometimes necessary. My inclination is along the lines of the advice I once heard about being minimalist if on the witness stand and a lawyer asks you "do know what time it is?" You look at your watch and see that it's 3pm so your inclination is to answer "3pm". My inclination is to follow the advice and answer "yes". It comes across as rude when I don't mean for it to be.
 
  • #19
Oh, well, in that case, I'm sorry too phinds.( Not a very minimalistic post ,that one, eh?)
 
  • #20
Gaz1982 said:
I can't even imagine one in practice.
One what? One singularity? It would be amazing if you COULD imagine one since it is not a "thing" it's just a word that represents "the place where the model breaks down". Someday, I hope, there will be a theory of Quantum Gravity that will give us a more meaningful insight into what is really going on at the center of a black hole. The word "singularity" has quite possibly caused more wasted keystrokes on this forum than any other single word/phrase.
 

FAQ: Does the Universe always have the same mass, or can it leak into other realms?

What is the mass of the universe?

The mass of the universe is estimated to be around 10^54 kilograms, which includes all matter and energy.

How do scientists measure the mass of the universe?

Scientists use a variety of techniques to estimate the mass of the universe, including studying the motions of galaxies, measuring the cosmic microwave background radiation, and observing the effects of gravitational lensing.

Is the mass of the universe constant?

No, the mass of the universe is not constant. As the universe expands, the amount of matter and energy within it also changes.

What makes up the majority of the mass in the universe?

About 27% of the mass of the universe is made up of dark matter, while normal matter (such as stars and galaxies) makes up about 5%. The remaining 68% is believed to be dark energy, which is responsible for the accelerating expansion of the universe.

Can the mass of the universe be calculated exactly?

No, the mass of the universe cannot be calculated exactly due to the uncertainty and limitations of our current scientific understanding and technology. Scientists continue to refine their estimates as new data and observations become available.

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