Why does general relativity break down at high energies?

In summary, general relativity breaks down at high energies due to its inability to incorporate quantum effects, leading to inconsistencies when describing gravitational interactions at the Planck scale. The theory assumes a smooth spacetime continuum, but at such energies, spacetime is expected to exhibit quantum fluctuations, necessitating a unified framework that combines general relativity with quantum mechanics, such as string theory or loop quantum gravity. This breakdown highlights the limitations of classical theories in extreme conditions and the need for a more comprehensive understanding of gravity in the quantum realm.
  • #1
KleinMoretti
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TL;DR Summary
what does it mean for general relativity to break down at high energies
more specifically what does high energies mean in this context, does it actually mean a high amount of energy? I can intuitively understand why it breaks down at small scales where quantum effects take place. for example it is said that high speed collisions produce a lot of energy and general relativity will break down as (part) of the description of such collisions, but why is that
 
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  • #2
KleinMoretti said:
what does it mean for general relativity to break down at high energies
Why do you think it does?

KleinMoretti said:
it is said
Where? Please give a reference.
 
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  • #3
PeterDonis said:
Why do you think it does?
isn't it said that one of the reasons a theory of quantum gravity is needed is because GR breaks down at some point for example singularities
 
  • #4
KleinMoretti said:
isn't it said
Said where? Again, please give a reference.
 
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  • #5
KleinMoretti said:
one of the reasons a theory of quantum gravity is needed is because GR breaks down at some point for example singularities
That is a reason that is given for looking for a theory of quantum gravity. But "singularities" is not the same thing as "high energies".
 
  • #6
PeterDonis said:
But "singularities" is not the same thing as "high energies".
okay but they do signal a failure of the theory and you were asking why I thought GR breaks down, and that's why im asking what does high energies mean in this context
 
  • #7
PeterDonis said:
Said where? Again, please give a reference.
I meant that as general statement
 
  • #8
PeterDonis said:
Said where? Again, please give a reference.
'This raises an important point: though we think of general relativity and quantum theory as ‘nice’ theories from the point of view of philosophical investigation, in a very real sense they are not the whole story and break down at extreme scales."

Quantum Gravity

 
  • #9
KleinMoretti said:
they do signal a failure of the theory
They might. It's not a proven fact, just an opinion.

KleinMoretti said:
that's why im asking what does high energies mean in this context
And until you can give some specific reference that even uses the term "high energies" in this context, there is no point in even asking.

KleinMoretti said:
I meant that as general statement
Vague general statements about what "is said" are not a valid basis for discussion here. If you're going to claim that something "is said", you need to give a specific, valid reference that says it.

KleinMoretti said:
'This raises an important point: though we think of general relativity and quantum theory as ‘nice’ theories from the point of view of philosophical investigation, in a very real sense they are not the whole story and break down at extreme scales."

Quantum Gravity

This is a philosophy website, not a physics textbook or peer-reviewed paper.
 
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