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> I'm not sure why physicists think gravity is a force and Pauling exclusion principle isn't. http://physics.stackexchange.com/questions/44712/is-pauli-repulsi

by avian 11y ago

> I'm not sure why physicists think gravity is a force and Pauling exclusion principle isn't. http://physics.stackexchange.com/questions/44712/is-pauli-repulsion-a-force-that-is-completely-separate-from-the-4-fundamental http://physics.stackexchange.com/questions/44712/is-pauli-re... http://physics.stackexchange.com/questions/141865/how-does-the-pauli-exclusion-principle-create-a-force-in-degenerate-matter http://physics.stackexchange.com/questions/141865/how-does-t...

scotty79 11y ago
> It is not a force, since at the particle level forces have carriers that are exchanged between particles so that momentum and energy change. In other words, we couldn't fit it to model of quantum fields and carriers and it fits perfectly other model where it's not a force. Gravity could be described with same exact words. Although I agree that exclusion principle superficially looks much less like a force than gravity does. Still, gravity is exactly same as forces that come from choosing accelerating frame of reference ... are there plans to look for carriers of those forces as well? Or should we expect gravitons popping up once we accelerate that don't exist for stationary observer?
- evanb 11y ago
  Gravitons are usually formulated by perturbing the metric around the flat Minkowski metric, but you can do perturbation theory around any metric, include those that describe accelerating frames. So, you might actually get gravitons in an accelerated frame. What you call background metric and what you call gravitons can get mixed together. However, because gravity is formulated in a generally covariant (ie. invariant under diffeomorphisms) the physical predictions must nevertheless agree when formulated in a frame-independent manner, much as they must in special relativity. Maybe the best example of quantum effects being different for accelerating and stationary observers is the Unruh Effect ( https://en.wikipedia.org/wiki/Unruh_effect https://en.wikipedia.org/wiki/Unruh_effect ). If an observer accelerates relative to a 0-temperature vacuum, they will see a blackbody background with T ~ a.
  - scotty79 11y ago
    Existence of particles depending on what frame of reference you pick sounds like whole new level of relativity. Not sure how this possibly could work with energy conservation.

by avian 11y ago

scotty79 11y ago

> It is not a force, since at the particle level forces have carriers that are exchanged between particles so that momentum and energy change. In other words, we couldn't fit it to model of quantum fields and carriers and it fits perfectly other model where it's not a force. Gravity could be described with same exact words. Although I agree that exclusion principle superficially looks much less like a force than gravity does. Still, gravity is exactly same as forces that come from choosing accelerating frame of reference ... are there plans to look for carriers of those forces as well? Or should we expect gravitons popping up once we accelerate that don't exist for stationary observer?

evanb 11y ago
Gravitons are usually formulated by perturbing the metric around the flat Minkowski metric, but you can do perturbation theory around any metric, include those that describe accelerating frames. So, you might actually get gravitons in an accelerated frame. What you call background metric and what you call gravitons can get mixed together. However, because gravity is formulated in a generally covariant (ie. invariant under diffeomorphisms) the physical predictions must nevertheless agree when formulated in a frame-independent manner, much as they must in special relativity. Maybe the best example of quantum effects being different for accelerating and stationary observers is the Unruh Effect ( https://en.wikipedia.org/wiki/Unruh_effect https://en.wikipedia.org/wiki/Unruh_effect ). If an observer accelerates relative to a 0-temperature vacuum, they will see a blackbody background with T ~ a.
- scotty79 11y ago
  Existence of particles depending on what frame of reference you pick sounds like whole new level of relativity. Not sure how this possibly could work with energy conservation.