Non-geometric approach to gravity impossible?

In summary: However, this seems like a more difficult task than modeling it without invoking curvature in space-time.
  • #106
atyy said:
I don't know in detail. I can point you to Weinberg's text and you'll have to do some additional work yourself, but I believe it doable from general considerations.

Ok. I have the MTW book. What particular pages can I find the answers of how to decompose the FRW Spacetime into flat space equivalent so that I can maybe contribute a future article in Sci.Am and and state that "You know, in FRW universe, it's not really curved, it only appeared curved. We are really living in flat spacetime with spin-2 field giving us the curveness." I'm sure the sci-am editors would love it.
 
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  • #107
waterfall said:
Ok. I have the MTW book. What particular pages can I find the answers of how to decompose the FRW Spacetime into flat space equivalent so that I can maybe contribute a future article in Sci.Am and and state that "You know, in FRW universe, it's not really curved, it only appeared curved. We are really living in flat spacetime with spin-2 field giving us the curveness." I'm sure the sci-am editors would love it.

If I can't find it in MTW.. the simplest I'd use is this:

In Milne universe, there is zero energy density, no cosmic microwave background radiation, no matter of any kind.

When one adds matter and spin-2 fields. Then it becomes FRW Universe with the curveness only as illusion".

I think the above makes sense. Do you agree with it atyy?
 
  • #108
waterfall said:
If I can't find it in MTW.. the simplest I'd use is this:

In Milne universe, there is zero energy density, no cosmic microwave background radiation, no matter of any kind.

When one adds matter and spin-2 fields. Then it becomes FRW Universe with the curveness only as illusion".

I think the above makes sense. Do you agree with it atyy?

Or you could say the spin 2 field is illusion. The only thing that counts as clearly not subject to interpretation is predictions of observation or experiments. Beyond that, curvature and fields, both, are not observable per se.
 
  • #109
waterfall said:
If I can't find it in MTW.. the simplest I'd use is this:

In Milne universe, there is zero energy density, no cosmic microwave background radiation, no matter of any kind.

When one adds matter and spin-2 fields. Then it becomes FRW Universe with the curveness only as illusion".

I think the above makes sense. Do you agree with it atyy?

You guys may ask what is the point of all this. The point is this. The mere facts about gravitons makes General Relativity just an effective field theory. Meaning GR is not a priori. What is a priori are gravitons. Note you can't combine gravitons and General Relativity because geometry can't have gravitons. Therefore let's accept the GR we are studying is not really a priori or primary. Perhaps just a classical limit. The true thing are the gravitons and spin-2 fields in flat spacetime. This is the real meat of it.
 
  • #110
waterfall said:
You guys may ask what is the point of all this. The point is this. The mere facts about gravitons makes General Relativity just an effective field theory. Meaning GR is not a priori. What is a priori are gravitons. Note you can't combine gravitons and General Relativity because geometry can't have gravitons. Therefore let's accept the GR we are studying is not really a priori or primary. Perhaps just a classical limit. The true thing are the gravitons and spin-2 fields in flat spacetime. This is the real meat of it.

Note that no one has observed a graviton, and Tony Rothman has 'nearly proved' that no graviton will ever be detected in the way photons are. Further, in a graviton theory, the flatness of spacetime is inherently unobservable and unrelated to predictions of time or distance measurements.
 
  • #111
PAllen said:
Note that no one has observed a graviton, and Tony Rothman has 'nearly proved' that no graviton will ever be detected in the way photons are. Further, in a graviton theory, the flatness of spacetime is inherently unobservable and unrelated to predictions of time or distance measurements.

But 97% of Ph.D.s believe in gravitons.. this is precisely what String Theory is about.. gravitons. The 3% are the Loop Quantum Gravity camp which believes geometry or GR is primary, they are just a minority.. so if you believe in the latter.. then you belong to the minority LQG camp.
 
  • #112
waterfall said:
But 97% of Ph.D.s believe in gravitons.. this is precisely what String Theory is about.. gravitons. The 3% are the Loop Quantum Gravity camp which believes geometry or GR is primary, they are just a minority.. so if you believe in the latter.. then you belong to the minority LQG camp.
Whether true or not, science is not about believing.
 
  • #113
Passionflower said:
Whether true or not, science is not about believing.

Bottomline is that we need a theory of quantum gravity. Gravitons are good approach becuase of the success of QED, Electroweak, Strong Force which is based on particles and quantum field theory. You can' make a geometry theory out of them. This is why Gravity force needs to follow the path of field approach. This is what makes String Theory so popular. And if you think String Theory has the geometry as a priori and the gravitons are just an excitation of the gravitational wave.. then you are wrong. Gravitons exist in string theory in the sense that when you have gravitons, you have gravity. And for gravitons to exist. You need quantum fields. This makes Geometry as secondary. This is the precise reasons why I want to understand more about spin-2 fields in flat spacetime. Because if they are unlikely on empirical grounds like FRW metric unable to decompose to spin-2 field + flat spacetime. Then we have to go to geometry and LQG may be a way to go or other geometry based theory.
 
  • #114
And now we have moved beyond asking questions and into the realm of pushing your viewpoint.
 
<h2>1. What is the non-geometric approach to gravity?</h2><p>The non-geometric approach to gravity is a theoretical framework that attempts to explain gravity without relying on the concept of space-time curvature, as proposed by Einstein's theory of general relativity. It suggests that gravity is not a fundamental force, but rather an emergent phenomenon arising from the interactions of other fundamental particles.</p><h2>2. Why is the non-geometric approach considered impossible?</h2><p>The non-geometric approach to gravity is considered impossible because it goes against the well-established and experimentally verified theory of general relativity. It also lacks supporting evidence and has not been able to make accurate predictions about gravitational phenomena.</p><h2>3. What are the main criticisms of the non-geometric approach to gravity?</h2><p>One of the main criticisms of the non-geometric approach is that it fails to explain the observed bending of light around massive objects, known as gravitational lensing. It also does not account for the effects of gravity on the flow of time, as predicted by general relativity.</p><h2>4. Are there any ongoing research efforts towards the non-geometric approach to gravity?</h2><p>While the non-geometric approach to gravity is not widely accepted in the scientific community, there are ongoing research efforts to explore alternative theories of gravity. Some scientists are investigating modified versions of general relativity that do not rely on the concept of space-time curvature.</p><h2>5. What are the potential implications of the non-geometric approach to gravity being proven impossible?</h2><p>If the non-geometric approach to gravity is proven impossible, it would reinforce the validity of general relativity as the most accurate theory of gravity to date. It would also highlight the importance of experimental evidence and the rigorous testing of scientific theories. Additionally, it could lead to further advancements and refinements in our understanding of gravity and the universe.</p>

1. What is the non-geometric approach to gravity?

The non-geometric approach to gravity is a theoretical framework that attempts to explain gravity without relying on the concept of space-time curvature, as proposed by Einstein's theory of general relativity. It suggests that gravity is not a fundamental force, but rather an emergent phenomenon arising from the interactions of other fundamental particles.

2. Why is the non-geometric approach considered impossible?

The non-geometric approach to gravity is considered impossible because it goes against the well-established and experimentally verified theory of general relativity. It also lacks supporting evidence and has not been able to make accurate predictions about gravitational phenomena.

3. What are the main criticisms of the non-geometric approach to gravity?

One of the main criticisms of the non-geometric approach is that it fails to explain the observed bending of light around massive objects, known as gravitational lensing. It also does not account for the effects of gravity on the flow of time, as predicted by general relativity.

4. Are there any ongoing research efforts towards the non-geometric approach to gravity?

While the non-geometric approach to gravity is not widely accepted in the scientific community, there are ongoing research efforts to explore alternative theories of gravity. Some scientists are investigating modified versions of general relativity that do not rely on the concept of space-time curvature.

5. What are the potential implications of the non-geometric approach to gravity being proven impossible?

If the non-geometric approach to gravity is proven impossible, it would reinforce the validity of general relativity as the most accurate theory of gravity to date. It would also highlight the importance of experimental evidence and the rigorous testing of scientific theories. Additionally, it could lead to further advancements and refinements in our understanding of gravity and the universe.

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