Speed of Space-Time: Exploring Light, Gravity & Warping

In summary, my friend and I were discussing light speed and how gravity seems to "bend" light. We all know of these gravitational "lenses" that are created by galaxies millions of light years away. But then I got thinking of the speed of light and gravity. According to some theories, the speed of light is the same as the speed of gravity. So if the sun disappeared, we would not notice until 8 minutes later. This scenario led to the question: If light takes 8 minutes to reach Earth from the sun, how long will it take before we notice the change of gravity from the sun not being there?
  • #1
dream431ca
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Ok, here me out on this one. I got thinking a while back after I read some very amazing books quantum physics and theory of relativity and and a thought just came to me. I might just be crazy though.

My friend and I were discussing light speed and how gravity seems to "bend" light. We all know of these gravitational "lenses" that are created by galaxies millions of light years away. But then I got thinking of the speed of light and gravity.

I made up a scenario of the disappearing sun. One day the sun disappears. Now, we all know that light takes 8 minutes or so to travel from the sun to the Earth. If the sun disappeared we would not know until 8 minutes later. Then I thought of this question: If light takes 8 minutes to reach Earth from the sun, how long will it take before we notice the change of gravity from the sun not being there?

In one of the books I read (I think it was the Fabric of the Cosmos), it explains that light and gravity have the same "speed" so to speak. If light and gravity have the speed, that means that the space-time is changing at the same rate as the speed of light. (When the sun disappeared, the space-time that was distorted will change back to flat space at the same rate as the speed of light).

What I'm saying is that the warping of space-time (gravity) will change at the same rate as the speed of light.

It's late and I had no coffee, so I could be out of my mind. What do you guys think?
 
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  • #2
Welcome to PF!

Hi dream431ca! Welcome to PF! :smile:
dream431ca said:
… What I'm saying is that the warping of space-time (gravity) will change at the same rate as the speed of light.

Yes, that's basically correct …

gravity is believed to move at the speed of light, so the gravitational effect of any change in the Sun (for example, the Sun pulsating in and out … it's difficult to see how it could actually move away :wink:) should reach us at the same time as we see it. :smile:
 
  • #3
Have a look at this
http://www.metaresearch.org/cosmology/speed_of_gravity.asp"
 
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  • #4


tiny-tim said:
gravity is believed to move at the speed of light,
Gravity doesn't move, it is already there. Statements like the above lead to wrong conclusions, about the direction of the gravitational pull of a moving gravity source. Gravity is not like light, but more like the electrical field. It is only the changes in gravity that propagate at light speed.
tiny-tim said:
so the gravitational effect of any change in the Sun (for example, the Sun pulsating in and out … it's difficult to see how it could actually move away :wink:) should reach us at the same time as we see it. :smile:
You mean the right thing, but laymen oft misunderstand this explanation.
 
  • #5
vin300 said:
Have a look at this
Van Flandern is a pretty notorious anti-relativity crank. Have a look only if you have a bunch of spare time and absolutely nothing better to do.
 
  • #6
"There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes. In particular, one does not think of particles as moving through space-time, or as following along their world-lines. Rather, particles are just in space-time, once and for all, and the world-line represents, all at once, the complete life history of the particle." R. Geroch, General Relativity from A to B (University of Chicago Press, Chicago, 1978), pp. 20-21.
 

FAQ: Speed of Space-Time: Exploring Light, Gravity & Warping

1. What is the speed of space-time?

The speed of space-time is the speed at which light travels through space, which is approximately 299,792,458 meters per second (or 299,792 kilometers per second).

2. How does light travel through space-time?

Light travels through space-time as a wave, with a wavelength and frequency that determine its energy and properties. It can also be described as a stream of particles called photons.

3. What is the relationship between light and gravity in space-time?

Einstein's theory of general relativity explains that gravity is a result of the curvature of space-time caused by the presence of mass. Light, being affected by the curvature of space-time, follows the path of least resistance around massive objects.

4. Can space-time be warped?

Yes, according to Einstein's theory of general relativity, space-time can be warped by the presence of mass or energy. This warping of space-time is what causes objects to experience the force of gravity.

5. What implications does the speed of space-time have on space travel?

The speed of space-time poses a major challenge for space travel, as it is currently impossible for any object to travel at the speed of light. This means that space travel will always be limited by the speed of light and the time it takes to travel through space-time.

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