
September 6th, 2002, 09:13 PM
#1
Einstein's general theory of relativity
Is the speed of light the same as the speed of gravity?
A new more accurate test is being carried out on Sunday to try and confirm whether or not this is true. The results of this potentially have far reaching implications, as this is the fundemental hypothesis for Einstein's general theory of relativity.
One or two sites have reported this, but I noticed it at news.bbc.co.uk/1/hi/sci/tech/2238452.stm

September 6th, 2002, 09:39 PM
#2
Interesting.
It could also open new doors on the "dark energies" and their interactions with gravity.
I have ever think the "antigravity" phenomenon which may keep on expanding the universe could also be a better physical basis than the speed of gravity.
I'll wait to know more about the results.
Life is boring. Play NetHack... more

September 7th, 2002, 02:48 AM
#3
it takes light 8 1/2 min to travel aprox 93 million miles... if the sun could instantly turn off its gravitational pull it would take 8 1/2 min for us here on earth to feel the effect.

September 7th, 2002, 05:02 AM
#4
Very strange... I was under the impression that the assumption was that gravity effects moved instantaneously.
From here.
Indeed, it is widely accepted, even if less widely known, that the speed of gravity in Newton's Universal Law is unconditionally infinite. (e.g., Misner et al., 1973, p.177) This is usually not mentioned in proximity to the statement that GR reduces to Newtonian gravity in the lowvelocity, weakfield limit because of the obvious question it begs about how that can be true if the propagation speed in one model is the speed of light, and in the other model it is infinite.
[HvC]Terr: L33T Technical Proficiency

September 7th, 2002, 05:35 AM
#5
Junior Member
NFO Page
In the simple Newtonian model, gravity propagates instantaneously: the force exerted by a massive object points directly toward that object's present position. For example, even though the Sun is 500 light seconds from the Earth, Newtonian gravity describes a force on Earth directed towards the Sun's position "now," not its position 500 seconds ago. Putting a "light travel delay" (technically called "retardation") into Newtonian gravity would make orbits unstable, leading to predictions that clearly contradict Solar System observations.

September 7th, 2002, 12:42 PM
#6
ok...too put it simply, If I have a Ginormus Rope which is fastened at Point A, and I'm at Point B, the minute I let go at Point B, the rope will fall at Point A....
It's a stream of energy, If it is broken, it fall's on both side's
 Noia
PS: Dark Energy is related to Simple Harmonic Motion's
With all the subtlety of an artillery barrage / Follow blindly, for the true path is sketchy at best. .: Bring OS X to x86!:.
Og ingen kan minnast dei linne drag i dronningas andlet den fagre dag Då landet her kvilte i heilag fred og alle hadde kjærleik å elske med.

September 7th, 2002, 01:44 PM
#7
Junior Member
The important question about all of this is:
so where does this leave Star Trek?
Shiraz

September 7th, 2002, 02:21 PM
#8
Junior Member
thought this mite be of intrest to some of you out there
http://www.eutopia.no/Pawels.htm
[shadow]I Have Not Failed I Have Just Fond 10,000 Ways It Will Not Work[/shadow][

September 8th, 2002, 09:50 AM
#9
In response to Terr's and pandora's posts, I'm not convinced that these conclusions are valid.
From a mathematical point of view, if you take Einstein's theories as a starting point, then you can derive Newton's equations from them, if you ignore the speed of light/gravitational speed. In mathematical terms you are disregarding second order parts of the equations, as for most practical purposes, they have no effect on earth.
Introducing 'retardation' into Newton's framework seems way off target, given that Einstein's model includes this, which is lost when you you change to a Newtonian framework.

September 8th, 2002, 01:06 PM
#10
The speed of light is app 186,000 miles a second. The affects of gravity appear to be instantly transmitted.
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