I heard that the speed of gravity was the same as light

[bindibadgi]

It was high school stuff until Einstein came along. It's not so simple any more, and skwinty hasn't actually got it wrong. It causes many headaches!

Back to the discussion though, if we think in terms of information, we have a problem with the effects of gravity being felt instantaneously. If a huge galaxy suddenly swung by our neighbourhood, and we felt the effect before we could see it, then we have information travelling faster than light. I don't think Einstein would be pleased!

[renormalised (Carl)]

Originally Posted by bindibadgi

It was high school stuff until Einstein came along. It's not so simple any more, and skwinty hasn't actually got it wrong. It causes many headaches!

Back to the discussion though, if we think in terms of information, we have a problem with the effects of gravity being felt instantaneously. If a huge galaxy suddenly swung by our neighbourhood, and we felt the effect before we could see it, then we have information traveling faster than light. I don't think Einstein would be pleased!

Always someone has to spoil the party

No, all it just means is that the information that's being carried by the gravitational field has arrived earlier than the information brought by its light. One just happens to be faster than the other. It just means that Einstein was "wrong" in thinking that light was the cosmic "speed limit", in so far as any information that was being sent to an observer. He is correct for visual information (light) but not for gravitational information, in this particular case (given the new interpretation in the paper mentioned).

In actual fact, neither condition is in violation of SR or GR, if you don't accept that light is the fastest carrier of information. In both their respective instances, neither light nor gravity can travel at infinite velocity in spacetime. That would be breaking SR and GR. What's being proposed is a modification and extension of SR and GR. People assume that both those theories at present are complete. They're not. Einstein himself never considered them as such.

To prove if this was correct or not, you could setup an experiment or make an observation of something where this process might be happening.

[edwardsdj (Doug)]

In Newton's theory, gravity is a force that acts at a distance between massive bodies. The propagation of this force is instantaneous. Newton was deeply troubled by the fact that he could offer no explanation for the mechanism of action of this force.

Einstein developed a field theory of gravity (much like Maxwells field theory of electromagnetics). In Einstein's theory (General Relativity) matter causes the space-time to warp and it is this warping of the space-time that causes bodies in free-fall to exhibit a curved motion through the space-time. Einstein thus proposed a mechanism for the action of the gravitational force over distance.

In General Relativity, gravity propagates at the speed of light. In much the same way that Maxwell realised that electric and magnetic fields propagate at the speed of light forty years earlier.

[edwardsdj (Doug)]

Originally Posted by renormalised

Always someone has to spoil the party

No, all it just means is that the information that's being carried by the gravitational field has arrived earlier than the information brought by its light. One just happens to be faster than the other. It just means that Einstein was wrong in thinking that light was the cosmic "speed limit", in so far as any information that was being sent to an observer. He is correct for visual information (light) but not for gravitational information, in this case.

In actual fact, neither condition is in violation of SR or GR, if you don't accept that light is the fastest carrier of information. In both their respective instance, neither light nor gravity can travel at infinite velocity in spacetime. That would be breaking SR and GR. What's being proposed is a modification and extension of SR and GR. People assume that both those theories at present are complete. They're not. Einstein himself never considered them as such.

To prove if this was correct or not, you could setup an experiment or make an observation of something where this process might be happening.

From these statements and those in another thread lately, I feel you would benefit greatly from the study of any first-year physics textbook before generating misinformation and confusion.

Experiments have been done to confirm the prediction of General Relativity that gravity propagates at the speed of light. The experiment involved the study of a distant quasar being gravitationally lensed by Jupiter. The speed of gravity was found to be 1.06 times the speed of light (as I recall) which confirmed General Relativity to within the experimental error.

[Gerald Sargent]

As a professional geologist/geophysist I see things on a time scale a
bit longer than physics has been around. I do not dispute any of the
experiments that have been done on the speed of light from planet
earth. However as everything is related to fundamental "measuring
sticks" , the so called speed of light being the basic measuring stick
of most of our measures. If however this changes as one passes into
outer space a lot of measure become questionable.
A german pysicist ahs demonstrated a "speed of light" of several
times the accepted speed in passing information through a brass
slug. I gather that he has the greatest difficulty in getting his work
published past the "establishment"
I accept that the accepted speed of light here is approximately
correct, it does however vary in the 4th significant figure as I learned
the hard way some years ago when doing the position fixing for landing
an oil pipeline from the Leman Bank (off East Anglia, UK) when we
pulled the pipe 1/2 miles ashore from the intended position. Research
revealed that this was due to the varying gross electrical resistivy of
the substrate and we actually made charts to enable these errors
to be allowed for in subsequent work.
However back in geologic time that speed may have vaired by a
quite significant amount - I am sure that it, and the value of the
gravitations constant also, varied quite a lot, my twopennyworth
- Gerald.

[renormalised (Carl)]

Originally Posted by edwardsdj

From these statements and those in another thread lately, I feel you would benefit greatly from the study of any first-year physics textbook before generating misinformation and confusion.

Experiments have been done to confirm the prediction of General Relativity that gravity propagates at the speed of light. The experiment involved the study of a distant quasar being gravitationally lensed by Jupiter. The speed of gravity was found to be 1.06 times the speed of light (as I recall) which confirmed General Relativity to within the experimental error.

Excuse me....you have no idea what I know or don't know, so before you go casting aspersions upon me (or anyone else for that matter), think carefully about what you say. You might find yourself neck deep in the proverbial.

I'm fully aware of what SR and GR say, and the postulates of both theories. For a start, if I didn't understand them, I wouldn't be doing a masters degree in science (Astronomy and Astrophysics) and averaging 93% in my assessed work. If you read what I have said, instead of going on about the veracity of Einstein, you'd have seen that I prefaced my statements with "if such and such)". There are other interpretations of the observations in the physics journals and whilst they don't always agree completely with the orthodox interpretation, they don't throw the baby out with the bathwater.

If you actually read what I have written before you go interpreting what I have said, you'll see (in this case) that I said "if" something or rather, knowing that experimental evidence needs to be found before something can be declared proven or not. I never said that it was proven that gravity moves faster than light, just that "if" it does, then this or that would happen. But don't think that some scientist haven't questioned Einstein more critically than most would otherwise. Just because experimental evidence appears to confirm his assertions so far, doesn't mean that sometime in the future he will not be proven incorrect. The problem with myopically believing in something is you miss things which may show you that reality could very well be otherwise. Or if you do see them, you just dismiss them out of hand. It happens all too much in science.

In so far as that "other thread" is concerned, I am quite correct in my assertions. Any theory which predicts infinities in its equations is in serious trouble....when it approaches those limits where the infinities appear. That's why renormalisation exists...especially for quantum theories. Infinities are inelegant and theoretical physicists hate inelegant theories. Anything which negates the embarrassment of having infinite values appearing within their equations is seen as a blessing. Infinities generate problems which are extremely hard, if not almost impossible, to deal with.

In so far as your quoted experiment, I find it rather disconcerting that a value of 1.06c was seen as being within experimental error, considering that a 6% error is seen as acceptable when nearly all other experiments in SR/GR have been verified to within 1 part in 10^20 or better as far as error is concerned. I would question their methods and experimental assumptions.

[CoombellKid]

Gee... dont tell any sky divers

NEWS Flash!!!!
Sky diver made 16km wide crater after his chute failed.

regards,CS

[renormalised (Carl)]

As a professional geologist/geophysist.....

Hello, Gerald....from a fellow geologist

I feel for those scientist that can't get their papers past the "establishment". It just goes to show you that no matter how rigorous and scientifically sound your paper might be, if you don't agree with the status quo, you might as well go play in the mud. There's so much politics and academic hubris within the scientific community, especially in physics and such, that it's a wonder any progress is made. They deny it, but they're just as myopic and one eyed as priests in any religion.

As a matter of fact, you could say that science has become the new religion.

[renormalised (Carl)]

It doesn't....it's just the effect of accelerated motion along a circular path, w.r.t. the mass of an object.

[edwardsdj (Doug)]

Originally Posted by renormalised

Excuse me....you have no idea what I know or don't know, so before you go casting aspersions upon me (or anyone else for that matter), think carefully about what you say. You might find yourself neck deep in the proverbial.

In another thread you started describing the second law of thermodynamics as the third law.

You then went on to state that the absolute zero temperature state was a state of maximum entropy. The third law of thermodynamics states that absolute zero is the state of zero entropy.

As I say, the chapter or section titled "Thermodynamics" in any first year physics textbook will make all of this clear.

Hope this is of some help

Have fun,
Doug

[Ian Robinson]

Originally Posted by Gerald Sargent

As a professional geologist/geophysist I see things on a time scale a
bit longer than physics has been around. I do not dispute any of the
experiments that have been done on the speed of light from planet
earth. However as everything is related to fundamental "measuring
sticks" , the so called speed of light being the basic measuring stick
of most of our measures. If however this changes as one passes into
outer space a lot of measure become questionable.
A german pysicist ahs demonstrated a "speed of light" of several
times the accepted speed in passing information through a brass
slug. I gather that he has the greatest difficulty in getting his work
published past the "establishment"
I accept that the accepted speed of light here is approximately
correct, it does however vary in the 4th significant figure as I learned
the hard way some years ago when doing the position fixing for landing
an oil pipeline from the Leman Bank (off East Anglia, UK) when we
pulled the pipe 1/2 miles ashore from the intended position. Research
revealed that this was due to the varying gross electrical resistivy of
the substrate and we actually made charts to enable these errors
to be allowed for in subsequent work.
However back in geologic time that speed may have vaired by a
quite significant amount - I am sure that it, and the value of the
gravitations constant also, varied quite a lot, my twopennyworth
- Gerald.

Hi Gerald, do you have a link for that (experiment) ?

For the value of c to be variable in a vacuum over cosmological and geological time scales , this requires e0 and mu0 and other fundamental properties to be variable.
It probably also means that everything we know about deep space (and the universial constant is wrong , ie it varies) and perhaps the age of the oldest galaxies is not right.
Interesting hypotheses. These kinds of questions are the spice of life .

PS : (while we are mentioning credentials , not a geologist , I'm but a humble chemical engineer who has recently studied physics and computer engineering , and am now , for want of something better to do , doing a masters degree).

[renormalised (Carl)]

Originally Posted by edwardsdj

In another thread you started describing the second law of thermodynamics as the third law.

You then went on to state that the absolute zero temperature state was a state of maximum entropy. The third law of thermodynamics states that absolute zero is the state of zero entropy.

As I say, the chapter or section titled "Thermodynamics" in any first year physics textbook will make all of this clear.

Hope this is of some help

Have fun,
Doug

I made a couple of silly mistakes, so what. Anyone else could. Plus it's been 20 years or so since I did undergrad physics....I'm entitled to make a few faux pas. I remember actually having thanked you for correcting me at the time, but in this particular instance, your repeating of my mistake in order to make a point about my apparent lack of knowledge is the height of arrogance and crassness.

[renormalised (Carl)]

For the value of c to be variable in a vacuum over cosmological and geological time scales , this requires e0 and mu0 and other fundamental properties to be variable.
It probably also means that everything we know about deep space (and the universial constant is wrong , ie it varies) and perhaps the age of the oldest galaxies is not right.
Interesting hypotheses. These kinds of questions are the spice of life .

Ian, this is something that cosmologist are seriously considering. There's evidence that the fine structure constant, G and a few others are variable and may have been different in the past. I can't remember off hand the actual articles, but they wouldn't be too hard to find if you like to search for them.

(YUUMMM...jelly trifle......way off topic, but I'm tucking into a trifle whilst I type this out)

[Paddy (Patrick)]

Interesting thread which raises quite a few questions that I've been pondering over. I do hope that all of you learned gentlemen continue to discuss the issue with respect for differences.

[Ian Robinson]

Originally Posted by renormalised

Ian, this is something that cosmologist are seriously considering. There's evidence that the fine structure constant, G and a few others are variable and may have been different in the past. I can't remember off hand the actual articles, but they wouldn't be too hard to find if you like to search for them.

I think I may have seen them in my travels .... like I said .... they are interesting questions .

If I remember correctly , there is no evidence that the fundamental constants and fundament properties have varied measureably in recent time (which geological time scales (only a few billion years) would be cf cosmological time scale to 14 billion years, in the Dark Ages say where cosmologists are not sure).

[renormalised (Carl)]

Very interesting questions, indeed.

From what I can remember, I don't think there's been a measurable change in the constants for the last few billion years...so far as I know. I'll have to catch up with the latest papers and see what they say.

[Ian Robinson]

Originally Posted by renormalised

(YUUMMM...jelly trifle......way off topic, but I'm tucking into a trifle whilst I type this out)

I can top that .... got a roast leg of lamb (with garlic and herb rubbing) cooking in the oven) and it smells wonderful. :drool:

[renormalised (Carl)]

Originally Posted by Ian Robinson

I can top that .... got a roast leg of lamb (with garlic and herb rubbing) cooking in the oven) and it smells wonderful. :drool:

I defer to your greater culinary droolness

[skwinty (Steve)]

Originally Posted by csb

Skwinty, sorry but I am going to tear your 'assumptions' to bits..in a friendly manner with no malice intended. For you are completely wrong in your whole statement. This is High school stuff.

Please glue my assumptions back together again and read them properly this time.

[Jen]