The Curvature of spacetime?? how?

[DanielFB]

do you think it is possible for space time to be curved. If space could be curved then it wouldn't be space, it would be matter.

Space to me is a geometrical substratum supporting the universe, and it is not possible for it to be curved. If it was, it wouldn't be space, but a type of matter, like quantum foam.

danielfb

[Dark Mind]

I don't think space is "literally" being curved... That's just a type of metaphor used to describe the intensity of gravity, I believe. The bigger the "curve" in towards an object, the more pwerful the gravity is.

Essentially it is a type of "quantum foam"... metaphorically...

[HydrogenBond]

Space has distance and time components; this is what curves. Since gravity is connected to the attraction between matter than if space didn't have substance than it would imply that gravity can bend distance and time without mass. That would really screw with the laws of physics because nothing would be stationary as space pulsates in space and time. Space having some mass makes more sense. Space mass probally comes as a biproduct of fusion, which is why space contraction occurs where matter is highly pressurized. Space is gaining substance which diffuses to uniformly fill space. This makes the final universe state one of contraction.

[infamous]

Originally Posted by HydrogenBond

This makes the final universe state one of contraction.

Are you suggesting that space is contracting now, or, that space will someday begin to contract?

[Dark Mind]

I believe "Now".

...But not positive, just really sure .

[DanielFB]

this sounds good, but however, I regret to say that if space is now physical it can no longer be space. I like to think of it in terms of a football field and it's boundaries. Now, it matters not how many players there are in the field, the boundaries never increase. What happens is new. The players fill over the edges, but the boundaries remain really fixed into reality. The same applies to space. But if general relaitivity is right, space must now be thought of as a mental construct, and nothing physical, say.

[Erasmus00]

Originally Posted by HydrogenBond

Space has distance and time components; this is what curves. Since gravity is connected to the attraction between matter than if space didn't have substance than it would imply that gravity can bend distance and time without mass.

Thats not true. According to general relativity, mass curves the space around it. The idea of curvature is then connected to mass, but it does not require space to have any "substance" in the way you mean.

Space having some mass makes more sense. Space mass probally comes as a biproduct of fusion, which is why space contraction occurs where matter is highly pressurized. Space is gaining substance which diffuses to uniformly fill space. This makes the final universe state one of contraction.

Space mass coming as a biproduct of fusion doesn't make any sense. The sun would then be gaining mass. Also, the expansion of the universe would be decelerating, not accelerating as observed. Not to mention that the most accurate theory of gravity we thus far have (general relativity) predicts that, if nonzero, the curvature of empty space creates a sort of anti-gravitational effect.
-Will

[Dark Mind]

... Like I keep telling myself... Someday, someday I'll know this stuff...

[Qfwfq]

Originally Posted by DanielFB

Space to me is a geometrical substratum supporting the universe, and it is not possible for it to be curved.

Have you studied differential geometry?

As far as we currently can observe, the geometric interpretation can't be really verified. It is simply a logical consequence of the principle of equivalence. Actually, gravity can be viewed as a curvature of space-time and not necessarily of space. Observing the lare scale geometry of the universe it might, however, prove to have a global topology that isn't possible for a flat space.

[UncleAl]

Why should spacetime be Euclidean? Because you learned 2-D plane geometry in high school? Euclid won't even work on the surface of the Earth (surveying, navigation). You have a choice of eight fundamental 3-D geometries,

WP Thurston, "Three-dimensional geometry and topology," Vol. 1. Princeton Mathematical Press, Princeton, NJ, 1997

Given a nice laser and two mirrors. You make an arbitrary optical triangle with sides each a few million miles long in free fall orbiting the sun. The laser shoots a light beam to the first plane mirror, it reflects to the second plane mirror, and that reflects back to the laser. You add up the sum of the interior angles of the triangle. Three possiblities:

1) The sum is exactly 180 degrees. Plane (Euclid) geometry. The circumference divided by the diameter of a circle is exactly pi. Given a point not on a given line, there can be drawn only ONE line through that point parallel to the given line. Flat sheet of paper.

2) The sum is more than 180 degrees. Elliptic (Bolyai-Lobechevsky) geometry. The circumference divided by the diameter of a circle is less than pi. Given a point not on a given line, there can be drawn ZERO lines through that point parallel to the given line. Surface of the Earth.

3) The sum is less than 180 degrees. Hyperbolic (Riemann) geometry. The circumference divided by the diameter of a circle is more than pi. Given a point not on a given line, there can be drawn an INFINITE number of lines through that point parallel to the given line. Surface of a nuclear power plant cooling tower.

If you do the laser experiment, (2) not (1) will obtain. This can be modeled as gravitation arising from either spacetime curvature (Einstein, metric theories of gravitation) or spacetime torsion (Weitzenböck, affine/teleparallel theories of gravitation). Spacetime curvature and spacetime torsion give identical predictions for all gravitational phenomena at all scales. However, they are measurably different based on their assumptions.

http://arxiv.org/abs/gr-qc/0505092
http://arxiv.org/abs/gr-qc/0412034

Metric gravitation postulates the Equivalence Principle: all local bodies fall identically in vacuum. Affine gravitation makes no additional postulate. If you can provide two lumps that fall differently in vacuum, Einstein was wrong. Folks have looked,

http://www.mazepath.com/uncleal/eotvos.htm#b22

given the menu of ways of being fundamentally different,

http://www.mazepath.com/uncleal/eotvos.htm#b21

The last possiblity for measurable metric/affine theory divergence will have its empirical experiment completed in mid-September. What makes you think there are only three material dimensions?

http://arXiv.org/abs/astro-ph/0508572