How does gravity curve spacetime?

Question

How does gravity cause a curve in spacetime?

What is the reasoning?

And how does curvature of spacetime occur?

Answer 1

Gravity doesn't curve spacetime. The distribution of mass /energy curves spacetime fabric that is perceived by us as gravity. If Equivalance principle is true, then gravity can be explained as a geometry of spacetime caused by the presence of matter. So why does the presence of a mass affect the property of spacetime?



There is no definite answer. But here is my crude reasoning. Assume that the mass does NOT curve spacetime. Then all heavenly objects will fling apart and drift in space. Also the individual matter that the heavenly bodies are made off would not be together. Everything will be floating as dust. The density of matter in space would approach zero! An empty space with zero matter does not make sense. Zero matter means zero energy. Energy does not require space, but matter requires. So If matter is zero, space also has to be zero and therfore time too. This leads to absurdum. So mass must curve the spacetime to preserve its existence.



I know this is unsatisfactory. Our Universe is really weird !

Answer 2

Gravity is a force that pulls. When I drop a pen, for example, it moves toward the ground. So I think that out in space the gravity from a planet pulls space and time toward it. I think it would shift space and time toward the gravity. This could be the curve you stated in your question. I also remember reading that blackholes have gravity and there is also antigravity which might be refered to as white holes. So if it is true that gravity causes a curve in spacetime then antigravity, which is the opposite of gravity, must cause the opposite of a curve in space time.

Answer 3

1. Hold a bedsheet flat and taut. (A "stretchy" sheet or blanket works best.) Have students stand around the bedsheet.

2. Roll several small balls back and forth across it. Observe their paths. The balls roll straight across the sheet. If Student A rolls a ball across the sheet toward Student B, the ball rolls straight to Student B- its path does not change.

3. Now place a heavy ball or weight in the center of the bedsheet. Hold the sheet taut, but let it sag in the middle where the weight is.

4. Roll the small balls across the sheet again. Observe their paths. This time, if Student A rolls a ball across the sheet toward Student B, the ball curves away from Student B- its path does change. Try and make the balls curve around the weight in some kind of orbit.



Why do the balls curve around the weight? Because they have no choice! In this model of spacetime, as the balls roll across the sheet, they are "gripped" by the sheet. Whatever shape the sheet takes, the balls will follow. In areas of space where the structure is flat, the balls roll straight. In areas of space near masses, spacetime curves and the balls curvewith it.





Mass distorts spacetime, causing it to curve.



Gravity can be described as motion caused in curved spacetime .Gravity in general relativity is described in terms of curved spacetime. The idea that spacetime is distorted by motion, as in special relativity, is extended to gravity by the equivalence principle. Gravity comes from matter, so the presence of matter causes distortions or warps in spacetime. Matter tells spacetime how to curve, and spacetime tells matter how to move (orbits).

Answer 4

This is a difficult question to answer. The sheet and bowling ball analogy is the most popular one but, to me, it lacks something, it is, in a way, two dimensional and does not show how any object approaching a mass from any direction is forced to follow the curvature of space. Imagine that space is a tightly compressed series of invisible rings that offer no resistance to objects passing through them in this compressed state. When you introduce a mass into this compressed series of rings the rings are expanded into concentric layers that are close together around the mass and are separated by bigger gaps as they move out from the mass, these separated gaps offer degrees of attraction to another object moving into the area and the moving object is guided toward the ring that compensates for it's speed and mass, if the speed and mass of the object is too great to be positively influenced by the rings the object will not be deflected enough to follow any one ring and will curve but break free of the rings and continue on its way through space. A lower mass will follow a ring and take up orbit around the mass that caused the seperation of the rings.

Answer 5

gravity is the curvature of space-time, not the cause of it.

Momentum and energy are the cause of it, but it is important to remember in general relativity that gravity is the curved geometry rather than the force curving our 4-fold geometry.

Answer 6

Let's start with E=MC2: or, energy equals mass times two, space time and curvatures of space. Einsteins theory of space travel and time.

Space is curved as well we know, a rocket has to go around the Earth to pick up speed and cannot go directly to the objective, in this case another planet but has to aim ahead in the same manner a hunter will aim ahead at moving game to hit it, a "lead" you might say.



This in itself takes twice as much time, maybe three times the time and energy (fuel) to get to the planet, right?

Have you ever watch "Star gate" the TV program? what if we could use a Star gate and just walk across a line, this goes directly to the objective, this is the explanation, going directly to the planet and not using the curve of space, like we have to now.

Or, using a "worm hole" like the movie with Jody Fisher when she uses a worm hole and skips across the galaxies in seconds to other planets, to her she is gone for 18 hours but, to the people on Earth, she is gone for 13 seconds.

This is the space curve or curvature of space time and skipping it, if it were possible like Einsteins theory says.

Answer 7

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