What is the speed of gravity?

Question

Say, for arguements sake, the sun simply disappeared, and empty space was all that was left (ie no remaining mass), at what point would the earth fly off at a tangent to its orbit? 8 minutes later or instantaneously?

Answer 1

Your question is really about the propagation speed of gravity. It's still debated among scientists. The 1993 Nobel Prize in physics was awarded to a team who reached this conclusion based on astronomical observations. Watch for results from the LIGO (Laser Interferometer Gravitational-Wave Observatory) and LISA (Laser Interferometer Space Antenna) projects, and the work of Joseph Taylor and Russel Hulse at Princeton.

Gravitation is an extremely weak force, very hard to measure. It's hard to set up an experiment with changing gravitational fields. I wouldn't call it conclusive yet, but I think most physicists would place their bets that gravitation propagates at the speed of light.

So, to answer your question, I would place my bet that gravitation propagates at the speed of light. Einstein considered that it might be instantaneous.

Answer 2

Wait a minute ... 8 minutes later is NOT the answer.

Eight minutes is the time it takes for us to see light from the sun. So if the sun simply disappeared, we would still see it for 8 minutes.

But if it disappeared, gravity from the Sun can't exist. There is no real 'speed of gravity', per say. The strength of gravity varies depending on the mass and other factors of the body of matter. If no body of matter exists which can create gravitational pull, there's no gravitational force. In other words, once the Sun disappears, its gravity disappears too.

So the Earth would stop going in its orbit right away. It wouldn't probably fly off at a tangent though, it might just go in another curve i think, because of the gravity of other planets, and because gravity isn't a constant. But whatever it does, it does it right away.

Answer 3

Although gravity appears to be a constant it is not. There is actually a anti gravity machine in Sweden and has been for almost ten years. Gravity is a wave mechanism. If the sun went missing we would not fly off out of orbit we would continue on a parabolic curve in the direction the earth was headed at the time of release. All the other planets, the moon and all space debris like asteroids etc would also be released. they would stop their normal orbits and what a mess that would be. Fun to think about. Wouldn't want to be there

Answer 4

I agree with gravity speed, to a point. On earth it is said to be 32ft and some centimeters per sec,per sec, per sec till contact with the attracting object.
If the space that the star we call Sol or the Sun were to become antimatter or dark space, the force of the event at the time that it occurs would have an instant effect on the Earths relationship with the unknown event.
Just erase the sun, or negate its effect on all the bodies in this System that would be an unknown event.
The planets would go Comet until they found a star or some fairly large mass of gravity to either be destroyed by or fall into syncopation with and then orbit.
We would all die, maybe 8mintues is too fast, we could run underground and maybe last a few hours, or more.
That is one sure way to stop Global Warming, radical but effective.
Now my brain hurts.
Great question.

Answer 5

I don’t believe everything VanFlandern says, but I do believe his is right about the speed of gravity. http://www.metaresearch.org/home/viewpoint/Kopeikin.asp

In Einstein’s General Relativity (GR), the vector representing the gravitational field (responsible for gravitational force) of a star 10,000 light-years away points to where the star is now, not where it was 10,000 years ago. Einstein didn’t acknowledge that he was implying an infinite speed of propagation; instead he said gravity does not propagate at all; it’s just a symmetrical warping of space centered on where the object is now. Einstein also predicted the existence of gravitational waves, which do propagate at the speed of light. Confusion between gravitational waves and gravitational fields has led to the widespread mistaken belief that gravity force propagates at the speed of light, according to GR.

VanFlandern acknowledges that gravity waves do propagate at light speed. He says gravity force does propagate and it has a finite speed, which is at least 20 billion times faster than light. Gravity force is carried by something resembling the classical gravitons of the Fatio/LeSage
http://en.wikipedia.org/wiki/Le_Sage's_theory_of_gravitation
http://www.mathpages.com/home/kmath131/kmath131.htm
model (not the same as the modern gravitons of the standard model). The classical graviton is not governed by the rules of GR because it is the carrier of the forces whose effects are described by GR. That’s all GR is—a description of the effects on matter of forces that are carried by faster-than-light gravitons, which are not matter. (Actually, Fatio, LeSage and VanFlandern do not address electrostatic forces. My own Fractal Foam Model of Universes postulates that all the fundamental forces of nature are transmitted by the same type of thing, which is not a particle but a p-wave which propagates thru the ether at the speed of gravity, whereas light waves are s-waves in the ether. http://forum.physorg.com/index.php?showtopic=15240.)

Faster-than-light propagation of gravity force does not violate causality. The whole causality misconception comes from the idea that a signal traveling faster than light will arrive before it left. That is simply not true because a signal has no clock. What if it were possible (and I’m not saying it is) to send messages at the speed of gravity—20 billion c? Suppose clocks on Earth and on PlanetX, 20 billion light-years away are synchronized in the way described by Einstein; at T = 0, a signal is sent from Earth to PlanetX, arriving there at T = +1 year; the signal says, “here comes our astronaut.” PlanetX then signals Earth saying, “got your message.”; the signal reaches Earth at T = +2 years. Meanwhile, the astronaut passes Earth at T = 0 with relative velocity toward PlanetX = 0.999,999,999,99 c; the astronaut passes PlanetX at T= +0.2 years by his own clock and at T = +20 billion and 0.2 years by PlanetX clocks, which are still synchronized with Earth clocks in the stationary coordinates, though not synchronized in the astronaut’s coordinates. PlanetX then signals Earth saying, “your astronaut has arrived”; the signal reaches Earth at T = +40 billion and 1.2 years. I’m too lazy, at the moment to work this out with realistic accelerations, etc., using GR; but please tell me, where’s the contradiction or paradox?

Answer 6

Gravitation propagates at lightspeed. If it were quantized it would propagate by massless (infinite range) tensor spin-2 (gravitation is uniformly attractive) bosons called gravitons.

It obviously cannot propagate faster than lightspeed or causality would be violated. The universe does not tolerate contradiction. If it traveled at less than lightspeed it would fall off with distance faster than 1/r^2 for having a massed propagator (look at the ranges of the Strong and Weak force). Lightspeed it is, exactly.

Answer 7

gravity itself does not have a speed. gravity depends on the planetary body ur talking about. the force of gravity is different from planet to planet. and by the way the answers are so wrong if the sun just vanished we may make around the spot where the sun was a few times because of centrifigal force and the simple mass of the planet but that is doubtful. everything on this planet depends on the sun. it wouldnt matter if the earth spun into space. we be dead to soon to notice. and gravity itself doesnt have a speed its a force u can measure how strong it is. but its what it pulls on where speed is involved

Answer 8

The same as the speed of light!!

so yes If the sun were to disapear would take about 8 minutes for the earth to fly off.

This a direct consequence of general relativity...gravitational waves travel at the spped of light

THE PERSON WHO SAID IT HAPPENS INSTANTANIOUSLY IS AN IDIOT!!!
THAT WOULD MEAN SOMETHING HAS TRAVELED FASTER THAN THE SPEED OF LIGHT WHICH IS A VIOLATION OF GENERAL RELATIVITY

Answer 9

This is the question of the ages in physics. In the application you pose, the string would be cut immediately.
BUT
Harmonics of gravity would reside for a small Significant Moment, providing integrity which would diminish geometrically or hyperbolically.
Thus, Earth would immediately begin to track off in a different arc, and that arc would geometrically devolve toward a straight line as the eight minutes expire.

Answer 10

Go to youtube.com and look for the vid "The Elegant Universe: Eisntein's Dream"

I think the answer is at part two or three of the whole episode