alpha2cen Posted January 6, 2011 Posted January 6, 2011 There are two stars which are 0.1 light years far away. Two stars are attracted each other by gravity. If one day one star disappears, how about the other star movement?
alpha2cen Posted January 6, 2011 Author Posted January 6, 2011 Are there any experimentally measured data? The limitation is speed of the light.
CaptainPanic Posted January 6, 2011 Posted January 6, 2011 There are two stars which are 0.1 light years far away. Two stars are attracted each other by gravity. If one day one star disappears, how about the other star movement? If no force acts on an object, what does it do? Today's choices are: A. Travel in a straight line. B. Stop instantly, while waiting for further instructions. C. Do a funny dance I think you can answer this one yourself. 1
alpha2cen Posted January 6, 2011 Author Posted January 6, 2011 If no force acts on an object, what does it do? Today's choices are: A. Travel in a straight line. B. Stop instantly, while waiting for further instructions. C. Do a funny dance I think you can answer this one yourself. It's another problem. Between two objects gravity had existed, but one moment one object disappeared which was too far away.
Klaynos Posted January 6, 2011 Posted January 6, 2011 http://en.wikipedia.org/wiki/Speed_of_gravity#Possible_experimental_measurements
alpha2cen Posted January 6, 2011 Author Posted January 6, 2011 http://en.wikipedia....al_measurements Thank you for good answering.
IM Egdall Posted January 6, 2011 Posted January 6, 2011 If our Sun were to suddenly disappear, the Earth would continue in its orbit around where the Sun was for about 8.3 minutes. Then the Earth would fly out of orbit into space in a straight line (ignoring the gravity from the other planets). Gravitational disturbances travel at the speed of light, some 670 million miles an hour. At this speed, it takes about 8.3 minutes to travel the roughly 93 million miles from the Sun to the Earth. Oh, and sunlight would also continue to be pouring down on the Earth for about 8.3 minutes after the Sun dissapears because light also travels at the speed of light.
alpha2cen Posted January 7, 2011 Author Posted January 7, 2011 Are there any theoretical link speed of gravity has to be same as speed of light?
ajb Posted January 7, 2011 Posted January 7, 2011 Are there any theoretical link speed of gravity has to be same as speed of light? General Relativity In particular look up gravitational waves. In short, small perturbations of a massive object cause gravitational waves that radiate at the speed of light. In this sense, gravity travels at the speed of light.
alpha2cen Posted January 8, 2011 Author Posted January 8, 2011 (edited) Between two objects gravity had existed, but one moment one object disappeared which was too far away. Then, how gravity arrived with time? Example A star--------------------------------------------------------------- B star gravity1......1.....1.....1.....1.....1.....1.....1.....1......1......1...1initial state ...........0......1.....1.....1.....1.....1.....1....1......1......1.....1....1 one star disappear ...........0......0.....0.....0.....1.....1.....1....1......1......1.....1....1 C answer ...........0......0.2..0.5...0.7..1....1.....1....1......1.....1.....1.....1 D answer Above example which one is correct between answer C and D? and Why? Edited January 10, 2011 by alpha2cen
Spyman Posted January 10, 2011 Posted January 10, 2011 Does the star disappear successively as 1...0.7...0.5...0.2...0 or instantly as 1...0 ?
alpha2cen Posted January 10, 2011 Author Posted January 10, 2011 Does the star disappear successively as 1...0.7...0.5...0.2...0 or instantly as 1...0 ? The question is like this. Star disappears instantly as 1...0.
D H Posted January 10, 2011 Posted January 10, 2011 The question is like this. Star disappears instantly as 1...0. The question is nonsense. You are asking what physics says will happen after something currently deemed to be physically impossible happens. Because stars don't instantly disappear, there is no physically plausible answer to your question.
alpha2cen Posted January 11, 2011 Author Posted January 11, 2011 The question is nonsense. You are asking what physics says will happen after something currently deemed to be physically impossible happens. Because stars don't instantly disappear, there is no physically plausible answer to your question. If there are equations which describe such system, we can obtain tendency curves for this artificial situation. When supernova explosion happen, how about the gravity near around the supernova? Most of the mass might disappear into the light, some of mass might remains. This is a decreasing step function.
Spyman Posted January 11, 2011 Posted January 11, 2011 (edited) It might have been said to you in several different threads already, but I think it needs to be repeated again: According to Relativity BOTH energy and mass warps spacetime equally. So due to conservation laws it is not possible to instantaneously remove a source of gravity from a location, even if all mass in a supernova explosion would be converted to energy in one single event, all that resulting light would still have the same gravity as the mass had before and then gravity would decrease gradually as the photons starts to radiate away with the speed of c. However that is not what you was asking about and not the reason for why I asked how the star disappeared. The rate of how fast mass/energy are accumulated/dispersed is not the same as which speed the change itself is spreading with. As I understand relativity the propagation of the change is moving outward from the source with c but the slope of the change doesn't change with distance, it remains constant. If a star varies its output with regular intervals then the frequency of the twinkles is measured to be equal for a close and a distant observer, but if the star would suddenly change the interval frequency then the closer observer would measure this change before the distant one. Likewise if the observers had sensitive enough equipment they could measure how the gravity decreases in steps with the same interval as the light twinkles and agree on the frequency but disagree on the time when the change of interval did happen. So if we assume that we could remove a star instantly then I think a distant observer would measure a normal gravity and light from this star until the abrupt change would arrive, were both gravity and light would vanish simultaneous and equally instantly as the star was removed. Edited January 11, 2011 by Spyman
alpha2cen Posted January 12, 2011 Author Posted January 12, 2011 From a theoretical point of view answer C is correct. Light speed is constant in the vacuum. And, as Gravity speed is the same as light speed, former contributer mentioned, there is no reason to delay Gravity speed in the vacuum.
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