How Would the Universe Evolve Without Gravitation?

[Loren Booda]

How would our universe have evolved without gravitation, and how so would the universe appear at present? Does such a situation somehow differentiate the possible perspectives of spacetime with or without compactified dimensions?

 

[jhmar]

Start at the beginning - define gravity and its cause.

 

[Mk]

Well I guess electromagnetism would be the dominant force, there would be no large systems, only ones closer down to electromagnetism's scale.

Opposite charges would clump together instead of just masses.

 

[pallidin]

I have heard that the gravity is an interdimensional quality.

 

[Loren Booda]

And I that it may be an intradimensional quality.

 

[masudr]

Our universe wouldn't have evolved without gravity.

 

[Loren Booda]

masudr,

Our universe wouldn't have evolved without gravity.

Please elucidate.

 

[Physics Monkey]

Hi Loren,

If you turned off gravity right now, the solar system would disperse and the sun would explode. Galaxies would fall apart and spacetime would cease to be dynamic. Gravity is the most important force at large distances, without it everything would break down. What masudr probably means is that universe would be a boring place if gravity had never existed. No inflation, no galaxy formation, no expansion of spacetime, no stars, no planets, no life. Everything is probably very hot and symmetric and dull. At least that's a rough picture of how I see it, please correct me if I'm wrong.

 

[Loren Booda]

Is inflation gravity-driven?

 

[Physics Monkey]

Inflation isn't driven by gravity per se, in the simplest models one has a single field called the inflaton that drives inflation. However, inflation wouldn't be possible without gravity since inflation is the rapid expansion of spacetime. Dynamic spacetime is essentially what gravity is.

 

[Loren Booda]

Extending that argument, since E-M (Maxwell's equations) involve relativity, would it not exist without spacetime? Could a universe of dark matter, or any matter, exist in a purely Euclidean space?

 

[Physics Monkey]

Well, Maxwell's equations are relativistic, but they don't necessarily require gravity to function. So no gravity just means spacetime is flat and doesn't have any dynamics, but one can still have electromagnetism on flat space. More interestingly, if the forces are unified, parhaps in the way the string theorists suggest, then it may indeed be impossible to have electromagnetism without gravity. We currently believe, for instance, that it is impossible to have electromagnetism without the weak force (since they are unified in the Standard Model).

 

[bettysfetish]

Well, I've been gone several months. I see most of you are still here. Anyway, I was simply going to answer Loren with, "No, nothing would have evolved without gravity" and be done with it. However the last post reminded me of a question I have that no one has been able or willing to answer.
Physics Monkey brings up a very interesting thought; "Can energy, in and of itself, exist without the presence of mass?" Gravity "Is" the most important force as one of you mentioned. "It is" an electromagnetic force, akin to what holds the atom together. I know their somehow inheirently different. If someone here can explain exactly what the difference is and why the two can't be unified I'd apprieciate it. If flat space can harbor "energy" then doesn't that lend some credence to the theory that all mass came from pure energy? And one more thing before I go; won't all matter eventually be converted back to energy via Black Hole processing. Shouldn't everything revert back to a flat one dimensional space occupied only be energy once more?
L8R

 

[Loren Booda]

Reminds me - from my website,

Consider, a problem in quantum geometrodynamics: the evolution of a zero curvature geodesic manifold in a massless, macroscopically uniform vacuum potential.