# How does Gravity behave at high energy?

At super high energy, Strong Force becomes weak to act like Electroweak Force (Grand Unification Theory; hand-waving version 2.2). Well, I am NOT trying to find Theory of Everything with this hand-waving question. I am just curious how Gravity behaves at high energy. It looks to me that it won't remain constant. A high speed motion should create strong ripples in Spacetime curvature.

Also, I am NOT talking about Quantum Gravity here in case you nag me about that. You don't need to give high energy to particles. There's no reason why a star or black hole can't be accelerated near $c$, mathematically.

How does Gravity behave at high energy?

• What has high energy? The object being influenced? The source of the gravitational field? – HDE 226868 Nov 23 '14 at 16:42
• @HDE Source or both. – Schrödinger's Cat Nov 23 '14 at 16:46
• have a look at the big bang cosmological model en.wikipedia.org/wiki/Big_Bang and TOE en.wikipedia.org/wiki/Theory_of_everything – anna v Nov 23 '14 at 16:47
• @anna I am not talking about that period. Even if Gravity was combined with other forces, that's in the Quantum Gravity domain because universe was small then. – Schrödinger's Cat Nov 23 '14 at 16:57

You say:

I am NOT talking about Quantum Gravity

but the change in strength of the strong and electroweak forces with energy is a quantum effect. It's due to a change in the coupling constant, which is known as running. There is no such effect in classical general relativity.

The analogous effect in GR would be for Newton's constant $G$ to be a function of energy. we would expect this to happen in some theory of quantum gravity, but in GR the constant $G$ is, well, a constant, and doesn't change with energy.

• So, this is it? There's nothing in entire physics around it? – Schrödinger's Cat Nov 23 '14 at 17:11
• @SachinShekhar: unless you consider quantum effects there is no mechanism to change the value of $G$. Quantum effects certainly will change $G$, but of course we have no theory of quantum gravity so we can't say exactly how it would change. – John Rennie Nov 23 '14 at 17:13
• I don't think it's that simple to say. Doesn't kinetic energy also create Spacetime curvature? – Schrödinger's Cat Nov 23 '14 at 17:15
• @SachinShekhar: yes it does, but that's just saying the curvature is dependant on the stress energy tensor - kinetic energy appears in the stress energy tensor as a momentum flow or a pressure. To be surprised at this would be like being surprised that increased mass causes increased curvature. – John Rennie Nov 23 '14 at 17:19
• I am not surprised at this, but I think Newtonian Gravity fails at this. Not due to increased mass, but due to kinetic energy. – Schrödinger's Cat Nov 23 '14 at 17:43