# B Gravity & geometry

1. Mar 2, 2017

### mieral

If gravity was not geometry.. what conservation law(s) would be broken?
For example.. if gravity was a force.. would other laws of physics be broken?

But gravity as geometry may not be complete answer because it has to be made compatible with quantum. Its quite puzzling.

2. Mar 2, 2017

### phinds

You are asking "if the laws of physics did not apply then what would the laws of physics say about <insert nonsense of your choice>".

3. Mar 2, 2017

### mieral

I heard of the Noether Theorem.. thought there was a necessary requirement why space has to be bind to time as geometry.

If not.. maybe the source code of the universe is geometry to the core.

Ok.. please transfer this thread to the Beyond the Standard Model as we are digging up some connections. Thanks

4. Mar 2, 2017

### phinds

I'm not a moderator so I can't move the thread but I can tell you that "beyond the standard model" does NOT mean "stuff that conflicts with known science".

5. Mar 2, 2017

### mieral

Beyond the standard model is Quantum Gravity. I thought why gravity was geometry had a reason.. wasn't it to make symmetry of space and time. Is this the only reason why gravity was geometry? But then geometry has to satisfy quantum and geometry can't be all it. That is why I think this topic is more appropriate for beyond the standard model.

6. Mar 2, 2017

### Staff: Mentor

Geometric theories follow the equivalence principle and explain the equality of inertial and gravitational mass.

7. Mar 2, 2017

### martinbn

In classical/non-relativistic physics, where gravity is a force, what conservation laws are broken and what other laws of physics are broken?

8. Mar 2, 2017

### mieral

Beats me. What?

9. Mar 2, 2017

### martinbn

You are asking the question "if gravity is not geometry but a force what conservation laws and other laws of physics are broken", you tell us why you expect that any laws will be broken? For example what conservation laws do you think are broken in classical physics?

10. Mar 2, 2017

### mieral

I remember reading it's Point of View Invariance. The rest I don't remember. But so what if point of view invariance is lost.. maybe conservation of energy? I forgot that's why I'm asking.

11. Mar 2, 2017

### martinbn

I think I see what your confusion might be. The invariance in Noether's theorem and the invariance in general relativity are different. It is actually the other way around than what is implied in your question. In classical physics you do have the invariance that gives you conservation of energy, but not every spacetime has it.

12. Mar 2, 2017

### Staff: Mentor

These questions are not answerable because you have not told us what specific model you want to use. "If gravity was not geometry" just tells us what model not to use (the usual spacetime geometry model of GR). It doesn't tell us what model to use.

"If gravity was a force" could be interpreted as saying "use Newtonian mechanics", but we already know what Newtonian mechanics predicts and which of those predictions don't match reality. If there is some other model that says gravity is a force, you'll need to tell us what it is.

No, it isn't. The reason we use spacetime geometry in relativity is that it works: the theory we build on that model matches reality. But there are plenty of other possible theories that are consistent with Noether's Theorem. You can formulate Noether's Theorem in Newtonian physics.

If you mean the principle of relativity, this is not limited to GR either. Newtonian mechanics has a principle of relativity.

In the absence of a specific question that can be answered, this thread is closed.