A question about gravity?

Question

If a rocket ship came out of (theoretical) hyperspace in the solar system, how does the sun "know" it is there (in terms of gravitational pull)?
Doesn't this violate relativity?

Answer 1

The sun DOESN'T know the ship is there, and it doesn't have to: Gravity is a warping or deformation of the four-dimensional fabric of space-time, not an actual pulling.

The earth travels around the sun because the earth is actually travelling IN A STRAIGHT LINE in its "local" space. The end result is an ellipse because the space around the sun is literally bent into a curved shape.

So, your ship can travel faster than light, but it can't travel faster than space -- which is to say, wherever it arrives after its hyperspace trip -- it IS where it IS and if the space is bent the ship will follow the contour of its local space regardless of how far it is from the source of the gravitational spacetime warping. No information or "graviton" needs to actually travel from the ship to the sun.

Answer 2

String theorists claim there must be at least 11 dimensions. So we can't think about this in only 3 dimensions.

Unfortunately, the only way we can clear it up is by providing examples in 3D.

Think about pressure. Like air pressure or water pressure. Helium is lighter than air. So a helium balloon will float up, trying to get above the heavier air. The matter is trying to reach an equilibrium.

Well, in space-time (4D), gravity works kind of like that. It all has to do with density. Matter is more dense than space, so matter collects. The Earth is pulled to the Sun (and vice versa), because both are more dense than the surrounding space (which has no density - it's nothing). Just like the balloon that is pulled up to be with the helium. It goes up because the air above it is a little less dense than the air beneath it; It's actually being squeezed upwards!

The instant your rocket ship appears anywhere, it will start being pulled towards the nearest star. Spacetime is a little more "dense" on one side of the ship than the other. The ship will accelerate towards our sun like a ball rolling down a hill (or more 3 dimensionally, like a balloon being squeezed through the air).

The more matter an object has, the more gravity it has. This is why suns eventually collapse and make black holes (actually black spheres). The more mass a black hole collects, the more gravity is has. The more gravity it has, the more it shrinks, and the more it pulls in more mass.

Eventually, the matter and space will be completely separate, as black holes are pulled towards each other to make one black hole. The more mass it gets, the smaller it will be.

Hope that helps.

Answer 3

The reverse of this sort of thought experiment is one of the things that led Einstein to the General Theory of Relativity. He aked, "If the Sun suddenly vanished, how long would it be before the Earth stopped orbiting it." He conjectured that the Earth could not "know" the Sun had vanished any faster than the speed of light would allow it (i.e. that gravity travels at the speed of light), because otherwise this would upset his Special Theory of Relativity (the one everyone babbles incoherently about here).

His final theory proposed that gravity was equivalent to curvature in space-time. This treatment has the advantage that you don't have to start messing locally with real physical objects to make them fit relativity, the curvature of space looks after it for you.

You can then think of the problem of the vanishing Sun as one in which this change in curvature propagates through space-time at the speed of light (a gravity wave).

Of course, you cannot just vanish stars, so real physicists look for real gravity waves that would be caused for instance by two stars rotating around each other.

Answer 4

Knowing and feeling are not in the realm of science for inanimate objects. The gravitational fields simply exist between the rocket and the sun. The "shape" and all measurable properties of "gravity" are theories that can be believed or not. For example the effects of gravity are defined by formulas that are made up by man. These formulas are simply tools to facilitate human experience. They give no other insight.

Answer 5

You already violated science by talking about hyperspace so why not just keep on violating!

Answer 6

very simple answer: Newton said: "What goes up....must come down"