How Gravity Works

[lpetrich]

Those are global effects, not local effects, so they don't count...

Oh, they count all right. But there you go, dismissing the scientific evidence that's right in front of your nose. You'll do the same for parallel-mirror light clocks. Oh look, the one down at the surface of the planet has a lower reading. Ah yes, that's because of the time dilation! Ooh, let's talk about time machines! Quack quack quack!

Except that SR and GR predict how much these effects will be, and so far, they've been right on the dot. And all you can come up with is outright dismissal.

Farsight, let's face it. You've been unable to predict the sizes of these effects.

The only one ducking and diving here is you. In the case of the specific experiments that you cite, calculation is required. You are talking about the "variable" speed of light. How does it vary? How does this allow us to get specific results from experiments? Are you just saying by Papal fiat that light varies in speed by just the right amount to get the results of any measurement, no matter what the experiment is?

No, I'm just giving the scientific evidence and the references to Einstein and the simple logic that you can't counter.

There you go again, Farsight. Treating Einstein's writings as some sort of Holy Writ, to be selectively quoted to support one's pet beliefs.

[Ulven]

Farsight,

Relativity: The Special and General Theory was a popular science book. This is the everyday usage. Check the translation with native-German speakers and they'll confirm what I say. Take care with online translations. For example somebody has changed the google translate to read "type" instead of "locality".

You might say that, in a sense, I did check with a native-German speaker: Herr Einstein himself.

In the popular science book “Die Evolution der Physik” (Einstein and Infeld) he states very clearly: “Will man eine Geschwindigkeit characterisieren, so bedarf es dazu sowohl einer Zahl als auch einer Richtungsangabe.” Roughly translated this says that if you want to characterise a velocity (Geschwindigkeit), you will require a number as well as a specification of direction. You can check the translation with Google if you like, it’s not perfect, but it’s close enough. I think I’ll stick to Einstein’s interpretation of the word, rather than yours.

The referenced book was published in 1950, by the way, and he goes on to explain the general theory of relativity and the behaviour of light in gravitational fields. Strangely enough, not once does he mention that the speed of light varies in the field, although he mentions that light is deflected from its rectilinear motion by the field, i.e. that its velocity changes. It appears that he had abandoned your theory at that point in his life.

Yes, I've read it all, umpteen times. Look at the top of page 179. It's perfectly clear. The motion through space is plotted as four-dimensional line in the mathematical space we call spacetime. When "the spacetime is curved" the motion through space isn't uniform, but the motion is still through space, not through spacetime. Have a google on "Nasty Little Truth About Spacetime Physics".

That's about as foolish as claiming that a particle doesn't move through three-dimensional space..it moves through three separate one-dimensional spaces.

[Farsight]

Except that SR and GR predict how much these effects will be, and so far, they've been right on the dot. And all you can come up with is outright dismissal.

There you go again, Farsight. Treating Einstein's writings as some sort of Holy Writ, to be selectively quoted to support one's pet beliefs.

I don't dismiss SR or GR. You're the one dismissing what Einstein actually said.

[Twiglet]

Except that SR and GR predict how much these effects will be, and so far, they've been right on the dot. And all you can come up with is outright dismissal.

There you go again, Farsight. Treating Einstein's writings as some sort of Holy Writ, to be selectively quoted to support one's pet beliefs.

I don't dismiss SR or GR. You're the one dismissing what Einstein actually said.

Why don't you go and solve Jims simple gravity problem here farsight?

[Farsight]

You might say that, in a sense, I did check with a native-German speaker: Herr Einstein himself. In the popular science book “Die Evolution der Physik” (Einstein and Infeld) he states very clearly: “Will man eine Geschwindigkeit characterisieren, so bedarf es dazu sowohl einer Zahl als auch einer Richtungsangabe.” Roughly translated this says that if you want to characterise a velocity (Geschwindigkeit), you will require a number as well as a specification of direction. You can check the translation with Google if you like, it’s not perfect, but it’s close enough. I think I’ll stick to Einstein’s interpretation of the word, rather than yours.

I have no issue with that statement. He's talking about a vector-quantity velocity there. But look again at the other quote:

"In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)".

One of the two fundamental assumptions of the special theory of relativity was the constant speed of light. So a vector-quantity velocity here doesn't make sense. Now take a look at A curvature of rays of light can only take place when the velocity of propagation of light varies with position. If you apply a vector-quantity velocity and break it down into speed and direction, and then say the speed doesn't change, that must mean the direction changes. So restate the sentence as A curvature of rays of light can only take place when the direction of propagation of light varies with position. This is a nonsensical tautology. It's saying light changes direction because it changes direction. Look at the OP again for the various Einstein quotes, and have a read of Is The Speed of Light Constant? where the author agrees with my take on this, saying:

"Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity."

The referenced book was published in 1950, by the way, and he goes on to explain the general theory of relativity and the behaviour of light in gravitational fields. Strangely enough, not once does he mention that the speed of light varies in the field, although he mentions that light is deflected from its rectilinear motion by the field, i.e. that its velocity changes. It appears that he had abandoned your theory at that point in his life.

That's wishful thinking I'm afraid, Ulven. He was struggling with his unified model until he died.

That's about as foolish as claiming that a particle doesn't move through three-dimensional space..it moves through three separate one-dimensional spaces.

No it isn't. Particles do move through three-dimensional space. What they don't move through is time. And when you combine space and time into spacetime, they don't move through that either. Go and read Nasty Little Truth About Spacetime Physics to understand why motion through spacetime is as foolish as motion through a block universe.

[ChildInAZoo]

I am quite happy with the idea of light moving at different speeds in GR. Now can we see how Farsight Relativity would calculate the rotation curve of a galaxy?

[Farsight]

No. It would take me too long, and it wouldn't help at all because Einstein's GR says energy causes gravity, and matter only causes gravity because of the energy content. So one works back to an energy-distribution that fits the observed galactic rotation curve, and you still don't know how that energy is configured. You don't know that it is disposed as particulate dark matter at all. Like I said, dark matter is just one hypothesis that attempts to explain gravitational anomalies, and has not in itself been observed.

[newolder]

... Like I said, dark matter is just one hypothesis that attempts to explain gravitational anomalies, and has not in itself been observed.

In order to test theories containing particulate dark matter instruments are deployed. Early results are not discouraging. If confirmed, how will you change your mind?

[ChildInAZoo]

No. It would take me too long, and it wouldn't help at all because Einstein's GR says energy causes gravity, and matter only causes gravity because of the energy content. So one works back to an energy-distribution that fits the observed galactic rotation curve, and you still don't know how that energy is configured. You don't know that it is disposed as particulate dark matter at all. Like I said, dark matter is just one hypothesis that attempts to explain gravitational anomalies, and has not in itself been observed.

So you admit that GR can tell us the distribution of mass-energy. So you admit that GR tells us that the galaxies we see look just like they would if dark matter were there. So in what way does your theory "do away with dark matter"?

[lpetrich]

(Farsight's fumblings and Einstein-thumping over the speed of light in a vacuum...)

It's very well-established that SR is a local approximation of GR, and Einstein was discussing one of the implications of that. Due to traveling in curved space-time, the speed of light in a vacuum becomes globally variable, even if it is locally constant.

He was struggling with his unified model until he died.

So what? Einstein did plenty of VERY good work.

Particles do move through three-dimensional space. What they don't move through is time.

Farsight, for all your Einstein-thumping, you have chosen to ignore where Einstein himself had disagreed. That trajectories go through space-time is a reasonable interpretation of Newtonian mechanics, and it's a necessary part of SR and GR, due to space-time unification.

I am quite happy with the idea of light moving at different speeds in GR. Now can we see how Farsight Relativity would calculate the rotation curve of a galaxy?

No. It would take me too long, and it wouldn't help at all because Einstein's GR says energy causes gravity, and matter only causes gravity because of the energy content.

Farsight, that sort of attitude will never get your published in a reputable journal. You HAVE to work such things out in order to be taken seriously in the mainstream scientific community.

So one works back to an energy-distribution that fits the observed galactic rotation curve, and you still don't know how that energy is configured. You don't know that it is disposed as particulate dark matter at all. Like I said, dark matter is just one hypothesis that attempts to explain gravitational anomalies, and has not in itself been observed.

One can work out how different sorts of dark matter would be distributed, like "cold", "warm", and "hot" dark matter. One finds from such working out that cold dark matter is the best fit.

[Twiglet]

I am quite happy with the idea of light moving at different speeds in GR. Now can we see how Farsight Relativity would calculate the rotation curve of a galaxy?

No. It would take me too long, and it wouldn't help at all because Einstein's GR says energy causes gravity, and matter only causes gravity because of the energy content.

Farsight, that sort of attitude will never get your published in a reputable journal. You HAVE to work such things out in order to be taken seriously in the mainstream scientific community.

A tall order to work out GR predictions for someone either unable or unwilling to work out the solution to Jims simple gravity and friction problem

[Farsight]

In order to test theories containing particulate dark matter instruments are deployed. Early results are not discouraging. If confirmed, how will you change your mind?

Early results are very discouraging, newolder. There's been considerable dissent about this, see for example http://physicsworld.com/blog/2010/05/xenon100.html. But you must know by now that I'm always referring to scientific evidence. It isn't something I dismiss. Show me some evidence that proves me wrong and I'll apologise profusely, and I'll admit I was wrong. I've done it before, and doubtless I'll be doing it again. But I don't think I'll be doing it about particulate dark matter any time soon. It was proposed by Zwicky in 1934. That's 76 years ago. That's a long time to believe in something for which there is no scientific evidence, whilst rejecting what Einstein said about energy causing gravity and describing a gravitational field as inhomogeneous space.

[Farsight]

The reading is done. Now we are asking questions about what we read. One questions is whether or not your theory can use evidence like every other theory is expected to. The details of the GPS system and the details of Shapiro time delay are mathematical details of measurement. So let's see how what you wrote in the OP leads to matching the measurements. If you don't do this, you have no evidence.

You're kidding yourself, but nobody else. The evidence is the measurements. The Shapiro delay is a fact of life, the light goes slower. Mathematical details aren't evidence.

[ChildInAZoo]

In order to test theories containing particulate dark matter instruments are deployed. Early results are not discouraging. If confirmed, how will you change your mind?

Early results are very discouraging, newolder. There's been considerable dissent about this, see for example http://physicsworld.com/blog/2010/05/xenon100.html. But you must know by now that I'm always referring to scientific evidence. It isn't something I dismiss. Show me some evidence that proves me wrong and I'll apologise profusely, and I'll admit I was wrong. I've done it before, and doubtless I'll be doing it again. But I don't think I'll be doing it about particulate dark matter any time soon. It was proposed by Zwicky in 1934. That's 76 years ago. That's a long time to believe in something for which there is no scientific evidence, whilst rejecting what Einstein said about energy causing gravity and describing a gravitational field as inhomogeneous space.

Zwicky did not propose particulate dark matter, let alone the kind that we measure in different ways today. I suspect that someone has pointed this out to you before but you are now continuing to dishonestly make this claim because you think that it helps your rhetoric.

But you have not shown us what replaces dark matter in your theory. All you have said is that we do not need it, but you haven't shown us what we do need, and how we can use the numerous observations out there to actually measure whatever it is in your theory that replaces dark matter.

You're kidding yourself, but nobody else. The evidence is the measurements. The Shapiro delay is a fact of life, the light goes slower. Mathematical details aren't evidence.

The mathematical details I want is how your theory matches the measurements. You haven't talked about any measurements in any of your posts.

[newolder]

Early results are very discouraging, newolder.

Then we disagree.

Physicians Informed About The Possible Dark Matter Particles are Registered
Published by noriuBMWX5
May 31, 2010, Category: Astronomy


Read more: http://scienceray.com/astronomy/physici ... z0qB7pw0R7