Quantum Gravity

[geordief]

(as I am "arguing" from ignorance feel free to relocate this thread:) )

 

 

I have heard it said repeatedly that Einstein's equations fail at situations described as singularities and that there is in consequence an aim to fashion equations that might describe such situations in terms of both General Relativity and Quantum Mechanics(a hypothesized Quantum Gravity).

 

Might it rather be that General Relativity is completely irrelevant in these situations ? Why is it that the equations describing the very small are unable to deal with these situations without the help of GR which only becomes applicable later on as the situation develops?

 

(again apologies for the level of ignorance ;perhaps the answer is obvious or the question badly formed or inconsequential)

[Strange]

The problem is that these difficulties arise when you have a combination of very high mass (therefore gravity is relevant) and very tiny dimensions (therefore, presumably, quantum behaviour is important). Examples, such as the mass of a star compressed to "something" at the centre of a black hole. Or the early universe, where the entire mass of the observable universe appears to have been compressed to less than the size of an atom.

 

Possibly, a quantum-gravity theory will explain these better (and maybe explain why things were not as intensely compressed as a simple application of GR alone suggests. For example, one recent attempt to approximate this suggests that the universe could be infinitely old: https://phys.org/news/2015-02-big-quantum-equation-universe.html

[geordief]

Is it possible that at some stage ,before mass reaches a mathematical degree of infinite greatness (ie a cutoff point) Quantum Mechanics simply takes over and gravity no longer has an arena to perform in?

 

is it inevitable that QM and GR are merged as models.

 

To coin a phrase could there be something of a step change involved ?

 

Of course if successful predictions are made that shows a kind of mathematical merger works then I am completely wrong,I suppose.

 

EDIT:sorry i didn't look at your link before I posted . Yes perhaps that might be more along the lines of what I was imagining.

Edited June 21, 2017 by geordief

[swansont]

Is it possible that at some stage ,before mass reaches a mathematical degree of infinite greatness (ie a cutoff point) Quantum Mechanics simply takes over and gravity no longer has an arena to perform in?

 

 

 

If that happened, it would be described as part of a theory of quantum gravity. You would have to explain this transition from having gravity to having none.

[geordief]

Thanks , I won't post any more(in this thread) for fear of posting more refined BS

Edited June 21, 2017 by geordief

[StringJunky]

 

 

If that happened, it would be described as part of a theory of quantum gravity. You would have to explain this transition from having gravity to having none.

Couldn't gravity be emergent i.e. it didn't exist because other conditions weren't met at that point?

[swansont]

Couldn't gravity be emergent i.e. it didn't exist because other conditions weren't met at that point?

 

 

I suppose so. But it would still be a description of some theory.

[Strange]

Is it possible that at some stage ,before mass reaches a mathematical degree of infinite greatness (ie a cutoff point) Quantum Mechanics simply takes over and gravity no longer has an arena to perform in?

 

 

That's a good question. (And a good reply from swansont.)