Is Gravity Really a Pseudo-Force in Modern Physics?

[PhilosophyofPhysics]

I was reading a Feynman lecture and I believe he said something about pseudo-forces being proportional to the masses and that gravity could be one. Then I think he said that in GR gravity is like a pseudo-force. Is gravity considered as a pseudo-force if the geometry of spacetime is its cause?

Are any of the new theories of quantum gravity working on a quantum geometry and not including actual "gravity particles" like gravitons?

 

[john baez]

I was reading a Feynman lecture and I believe he said something about pseudo-forces being proportional to the masses and that gravity could be one. Then I think he said that in GR gravity is like a pseudo-force. Is gravity considered as a pseudo-force if the geometry of spacetime is its cause?

Yes, that's a popular viewpoint on general relativity. Of course, gravity arises from how energy and momentum curve spacetime, and it's a very real thing, so one shouldn't infer from the term "pseudo-force" that gravity is somehow "fake". But, it's not a force in the sense of something which causes particles to accelerate - particles move along geodesics, "as straight as possible".

Are any of the new theories of quantum gravity working on a quantum geometry and not including actual "gravity particles" like gravitons?

Sure! The closely related ideas called "loop quantum gravity" and "spin foam models" are all the result of people trying to develop a theory of quantum geometry. Try these for starters:

Institute for Gravitational Physics and Geometry, http://www.gravity.psu.edu/research/poparticle.shtml"

Carlo Rovelli, http://relativity.livingreviews.org/Articles/lrr-1998-1/"

John Baez, This Week's Finds in Mathematical Physics:
http://math.ucr.edu/home/baez/week109.html" .