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| basim |
 Posted: Fri Jul 11, 2008 11:02 pm Post subject: speed of gravitational effect |
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My question is, If sun is to blast,explode,or disappear at once some how, will the effect of that have an instant effect on the earth. Or earth will continue in the orbit for 8mins and then have the effect.?
I know it might not be possible. But the Question is gravity have instant effect or with the speed of light.??
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| kojax |
| Posted: Fri Jul 11, 2008 11:48 pm Post subject: |
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Forum Ph.D.
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It's an interesting question. I'm assuming you mean to ask what would happen if the sun just winked out of existence. It's purely academic, however. The matter and energy that make up the sun can move, but never disappear. In fact, it can only move at the speed of light or slower......
We can make a lot of very interesting questions out of this, however. What if the sun began moving away from us at the speed of light? I wonder what our orbit would look like then. |
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| Arch2008 |
| Posted: Sat Jul 12, 2008 9:28 am Post subject: |
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| The effect of gravity propagates at the speed of light. |
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| BumFluff |
| Posted: Sat Jul 12, 2008 10:15 am Post subject: |
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Joined: 06 Mar 2008
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Newton believed that it would have an instant effect. However when Einstein made his Theory of Relativity it argued against Newtons original hypothesis and it is now thought that if the Sun exploded we would not know it for 8 minutes.
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| kojax |
| Posted: Sat Jul 12, 2008 4:30 pm Post subject: |
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| .... except that the explosion would only happen at the speed of light. But yeah, we'd experience all effects, even the change in gravity, 8 minutes late. |
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| 425 Chaotic Requisition |
| Posted: Sat Jul 12, 2008 5:25 pm Post subject: |
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The Doctor
Joined: 18 Jun 2007
Posts: 3316
Location: England, UK.
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The Earth would continue to orbit the sun for the time it takes light to travel to Earth.
When Einstein made Special relativity, he realised eventually that his theory disagreed with Newton's idea of gravity. So thus he had to formulate a new theory on gravity to explain how gravity could still work. Hence, General relativity. It is ironic that sometimes you create one thing. You create multiple theologies when you never intened to. Coincidences,  .
So to answer your questions. What we observe, the effect would occur at the speed of light, and thus take 8 minutes to take affect.
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| cryptonic26 |
| Posted: Sat Jul 12, 2008 8:30 pm Post subject: |
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Would someone mind explaining the steps that were taken by the original theorist to reach an understanding that the effect of gravity has something to do with the speed of light?
Are there any reproducible experiments that would show this to be true? Or is this all theoretical conjecture based on good faith assumptions?
Just asking for some citations, or links to help verify this assertion. |
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| 425 Chaotic Requisition |
| Posted: Sun Jul 13, 2008 4:43 am Post subject: |
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The Doctor
Joined: 18 Jun 2007
Posts: 3316
Location: England, UK.
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OK Here:
Newton (before Einstein) stated that if the sun disappeared instantly, then all the planets orbiting the sun would all, at the same time spin off into the universe.
Now that means that that effect from the sun to each individual planet would take more or less time if we stand on Earth and observe the effect ourselves.
For instance, it takes light to travel to Earth, roughly 8 minutes. For Jupiter it takes apparently: 43 minutes (http://au.answers.yahoo.com/question/index?qid=20080416140022AAgJwx8) But this may not be truly valid.
Anyway, so you can see that if by Newtons explanation, Jupiter and Earth would go off at the same time. But Einstein in Special relativity said NOTHING can travel faster than light. That includes the speed of gravity. So when one day Einstein thought about this Sun vanishing phenomena, he realised that he had shown Newtons statement to be wrong, and thus had to explain the effect of the sun vanishing and the effect not happening faster than the speed of light. It took him over a decade, but to explain this effect he created General relativity.
Here is a video that makes much more sense:
http://uk.youtube.com/watch?v=tpbGuuGosAY&feature=PlayList&p=5D7284F21F0721F4&index=0
Sorry about the quality.
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| jackson33 |
| Posted: Sun Jul 13, 2008 6:41 am Post subject: |
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Energy (light) is a product. Once created and sent from the source, it travels at the suggested speed effecting matter to an ever decreasing degree (from dispersement), regardless what happens to its source. There is no reason to believe one photon from 10-13 bly away is any less powerful than one photon from out sun.
Gravity is an effect on matter and should exist only while the sources exist, in this case much like a string attached to two or multiple objects. If one of the sources instantly disappears, the string may still exist, but the effect should instantly cease.
If 99.95% of matter in one system disappears (our sun), there would be instantly another source for 98% of the total effect between the remaining matter, Jupiter. While the effects would be instant, matter still has limitations for acceleration and velocity. The probability is most remaining solar system matter would end up destroying Jupiter, as very large asteroids would earth, leaving a near dust cloud to drift through space.
This is my opinion only, I have no source. I do think there are some unknown things about gravity, which many people would agree.... |
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| 425 Chaotic Requisition |
| Posted: Sun Jul 13, 2008 9:56 am Post subject: |
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The Doctor
Joined: 18 Jun 2007
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Location: England, UK.
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| jackson33 wrote: |
| I do think there are some unknown things about gravity, which many people would agree.... |
Not half.
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| kojax |
| Posted: Sun Jul 13, 2008 10:00 am Post subject: |
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Forum Ph.D.
Joined: 27 Mar 2007
Posts: 1052
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| cryptonic26 wrote: |
Would someone mind explaining the steps that were taken by the original theorist to reach an understanding that the effect of gravity has something to do with the speed of light?
Are there any reproducible experiments that would show this to be true? Or is this all theoretical conjecture based on good faith assumptions?
Just asking for some citations, or links to help verify this assertion. |
Einstein's gravity predictions were much more complicated than Newtons, talking about "space time curvature" instead of a raw force. 2 major things confirmed it:
1) - The eliptical orbit of Mercury around the sun has something called a "precession" which means that the egg-shaped elipse pattern of it's orbit shifts a few degrees every few years. (Which has always been seen as a paradox in Newtonian mechanics)
The mathematics of Einstein's relativity theory not only predicted it, but actually demanded it, and nailed it's exact magnitude. (Einstein reportedly had heart palpitations when he finished working the formula out and realized it was such a perfect match)
2) - The Eddington expedition during a solar eclipse that set out to measure the shift in position of stars behind the sun (due to the sun's gravity pulling on the light as it passes).
The truth is that both Newton, and Einstein predicted that the light would be curved as it passed the sun, but Einstein predicted a different amount than Newton. Einstein turned out to be the one that was right.
The experiment has been repeated with greater accuracy since we got into space using satellites which can set blinders that block the sun perfectly from their view, leaving a clearer picture of what's behind it, and they always get Einstein's numbers, rather than Newton's. |
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| Janus |
| Posted: Sun Jul 13, 2008 12:10 pm Post subject: |
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Joined: 30 Jun 2007
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| kojax wrote: |
1) - The eliptical orbit of Mercury around the sun has something called a "precession" which means that the egg-shaped elipse pattern of it's orbit shifts a few degrees every few years. (Which has always been seen as a paradox in Newtonian mechanics)
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It should be pointed out that like the light bending around the Sun, it wasn't the precession per se, that was the problem, but the fact that the amount of precession was more than could be accounted for by Newton's laws.
One of the possible explanations floated for the excess precession was the existence of a planet inside the orbit of Mercury. This proposed planet was named Vulcan. Though there were a few false alarms, no such planet was ever found and with Einstein's Relativity it was no longer necessary.
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| cryptonic26 |
| Posted: Sun Jul 13, 2008 9:32 pm Post subject: |
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The thing about Albert's space-time distortion as an explanation of gravitational effect seems to be a little off kilter to me though? I mean, warping space should effect the absolute position of an object, but not it's local vector of movement, nor it's local position.
That is to say.. if you alter the coordinate system of an environment, locally you experience nothing out of the usual.. Everything that can be experienced should be effected by that coordinate grid. a particle moving from p(x1,y1,z1) to p(x2,y2,z2) would speed or slow from an external point of reference (due to the space warping causing the distance between these two points to change), but a local observer on the same coordinate grid would not be able to recognize that change without an external POR. That same particle should also experience absolute volume changes as it enters or exits regions of higher or lower density space; but not local changes.
A moving object with a trajectory that bypasses a massive object should dip in towards that object, and finally ascend back away from the object to continue on it's original trajectory with no alteration what so ever... IF a space warp were the only thing that caused the initial 'attraction', but this would only be visible from an external point of reference, as that space density gradient would cause observations from a local POR to appear as though the object just flew right past it without experiencing any sort of vector changes.
A simple space warp does not seem to account for locally observed acceleration, unless I'm totally lost with what is actually meant by 'warped' space...
Whatever way you look at it though, the effect of gravity isn't necessarily caused by a physical moving particle, therefore it doesn't necessarily have to adhere to the speed of light, since we don't really know weather or not something is actually moving at all? I know we have been in search of the fabled gravitron.. but we have not been able to isolate or identify a real case of it yet. Looks to me like the answer to all of this is still up for grabs. |
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| kojax |
| Posted: Sun Jul 13, 2008 11:13 pm Post subject: |
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Forum Ph.D.
Joined: 27 Mar 2007
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| cryptonic26 wrote: |
The thing about Albert's space-time distortion as an explanation of gravitational effect seems to be a little off kilter to me though? I mean, warping space should effect the absolute position of an object, but not it's local vector of movement, nor it's local position.
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I think sometimes it's just the language that's confusing. Trying to visualize space-time-distortion is always going to be a little bit of a dead end because it's not really a visual thing. Even the analogy of pushing down part of a trampoline to show how objects move to the part that's distorted probably doesn't capture the real meaning of the idea. |
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| Cosmo |
| Posted: Mon Jul 14, 2008 5:32 am Post subject: Re: speed of gravitational effect |
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Joined: 22 Nov 2007
Posts: 615
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| basim wrote: |
My question is, If sun is to blast,explode,or disappear at once some how, will the effect of that have an instant effect on the earth. Or earth will continue in the orbit for 8mins and then have the effect.?
I know it might not be possible. But the Question is gravity have instant effect or with the speed of light.?? |
There was a recent experiment/observation that has established that gravity propagates at the speed of light.
So it is not instantaneous.
Cosmo |
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