Answerer

Hi guys, as I believe that everyone of you knows that mass can bend or sketch spacetime according to GR. But recently an idea comes to my head which suggests that spacetime may in some ways behave like a solid and has an elastic limit and breaking point of its own. So how many of you feel that this is possible? If so, what do you think will be its limit?

eh

No, according to cosmologists. There is no limit on how large the gravitational field can get.

Friar Bellows

Andrei Sakharov (yes, the Andrei Sakharov) proposed such a theory which views gravitation as an elasticity of space arising from some complicated particle physics, just as standard elasticity arises out of some complicated molecular physics.

But here's a question for you, Answerer. What happens when spacetime is stretched beyond its breaking point? What do you think happens when it "breaks"?

By the way, Penrose and others back in 1965 proved some theorems about the necessary existence of singularities. I'm not sure, though, what this says about the existence of infinite gravitational fields. I don't think a singularity is necessarily an example of an infinite gravitational field. But I'm just waffling in ignorance.

Answerer

Ha, I never expect the answers to be both 'Yes' and 'no' from you guys. So, what do the others think?


Your question seems to be a bit tricky. I, for one, believe that if there is a tear in spacetime continuity, our GR theory will lose its predictability in that region. Perhaps all singularities are the closest things to what we would call a tear in spacetime fabric. Since our universe is expanding faster and faster and if there is a limit for spacetime expansion, there is a high chance in the future whereby we may witness our universe tearing itself apart.
Anyway, I'm just imagining things and there is no one to tell me whether I could be right or wrong.

fando

Well, if you're curious about the idea of spacetime tearing, there was an interesting idea floating around in M-brane theory (string theory with membranes) that a Caleb-Yau space (a multidimensional spacetime) can rip and tear while transforming into another Caleb-Yau space. The actual discontinuity would be shielded from the universe by a membrane. Some didn't like the idea that spacetime can tear and wanted something more palatable. So, after some more poking around, it was discovered that in a certain metric, spacetime didn't actually tear while undergoing this transformation. If you wish to read more about this, I recommend reading the litterature. I'm sure Greene's The Elegant Universe covers this development in detail.

SULPHUR

I did not realise that that universe was still expanding at an a greater rate.I thought that the greatest acceleration at the the instant of the last big bang.

Liquidrage

It now appears to be generally accepted that our universe is accelerating. Recent research has confirmed earlier reports.

This creates a huge paradigm shift.

Long it's been thought that the expansion of the universe was due to the big bang and that gravity was countering this expansion.

But if we do indeed live in an accelerating universe then potentially expansion is an intrinsic property of space. The Cosmological Constant is no longer obtuse and becomes a force that would need to be unified just like gravity.
The initial conditions of the universe no longer seem so unlikely.

eh

The only thing Penrose and Hawking proved was that under GR, singularities must exist. But we know GR isn't accurate at quantum scales, and I don't know what scientist actually believes they exist in reality.

Oxymoron

Just to add a note of caution: yes, there are several experiments "confirm" the increase in the expansion rate; but it is not universally accepted as it depends upon the current models of supernova brightnesses and intergalactic absorption, which are not 100% robust.

Answerer

Wow, this is definitely something new. You claimed the spacetime don't actually tear but it transformed in another Caleb-Yau space. What is it anyway? At the meantime, I will look for the book you recommend, thanks.