# Shapiro effect ? Speed of gravity waves and light ?

#### Farsight

I am a little concerned that I might be being misled, in some subtle way by Farsight. Is the explanation ref variable light speed correct in explaining the Shapiro effect. I follow the argument and it seems plausible.
I'm not misleading you. See Shapiro's paper. He says this: "Because, according to the general theory, the speed of a light wave depends on the strength of the gravitational potential along its path".

That's what Einstein said too, time and time again. However after he died Peter Bergmann popularized the idea that the speed of light doesn't change with gravitational potential. See Wikipedia:

"Peter Bergmann did not agree with Einstein, but left the dispute out of his earlier book[8] in 1942 to get Einstein’s endorsement. After Einstein died Bergmann wrote a new book[9] in 1968 claiming that vector light velocity could change direction but not speed. This has become a prevailing opinion in science, but not in agreement with Einstein’s unambiguous math. Bergman did acknowledge that the apparent speed of light would change in a gravity field and go to zero at an event horizon as viewed by a distant observer[10]".

If the speed of light in the vacuum is not constant away from gravitational sources ie in an expanding space, possibly expanding at different rates, then does this not make the measurements look a little more difficult.
It would. Note that if space expands between the galaxies but not within as per the raisin-cake analogy, every galaxy will be surrounded by a region of space where the speed of light varies. And a gravitational field is a place where the speed of light varies.

#### Farsight

Light is measured as constant due to the clock rates changing speeds and and rulers changing lengths in different reference frames. Can you suggest another method measuring light speed to show it is not constant.
You use optical clocks. See the interview with David Wineland of NIST: “if one clock in one lab is 30cm higher than the clock in the other lab, we can see the difference in the rates they run at”. An optical clock goes slower when it’s lower. This is said to be the hard scientific evidence for gravitational time dilation. But it’s really the hard scientific evidence for light goes slower when it’s lower. That's because there is no actual thing called time flowing through the optical clocks. But there is light moving inside them.

Inflation is standard model, what would you replace it with Hoyles universe, Cosmic Cyclic Cosmology What?
Google the Standard Model of Cosmology and you can read the article on the Lambda CDM model. It says "The ΛCDM model can be extended by adding cosmological inflation, quintessence and other elements that are current areas of speculation and research in cosmology". So I'd say inflation isn't really part of the Standard Model of Cosmology. So I wouldn't replace it with anything. IMHO big bang cosmology is better off without it.

Thats what I think I said Photons have inertia also Einstein stated E^2=(mc^2)^2+(pc)^2 the E=mc² is an abbreviation
Good stuff.

Without constant light speed a lot of theories appear a bit wobbly. Are you saying the standard model view of the universe is wrong? If so how so?
I think big bang cosmology is largely correct, but that some of the things people think of as being part of the standard model of cosmology, are not. Things like inflation. This article is worth reading: Physicist Slams Cosmic Theory He Helped Conceive

interested

#### interested

I understand no one takes the concept Big Bang singularity seriously, this is why Inflation was developed by Guth and then modified by Linde.

Your Links do not support the Lambda CDM model they criticise it

"The prevailing model of the Big Bang is based upon the GTR. According to this theory, extrapolation of the expansion of the universe backward in time yields an infinite mass-energy density and temperature at a finite time, approximately 13.8 billion years ago. Thus the “birth” of the universe appears to be associated with a singularity, which describes not only a breakdown of the GTR, but also all the laws of physics. This suggests a dubious assumption associated with the Big Bang hypothesis, indicating that the GTR with the FLRW metric is not valid for extremely small regions of space. "

Also in addition to this Dark matter is not required by Quantum theory, and has never been detected in the lab or by any other experiment.

My simple understanding is that during the inflationary stage of the universe virtual particles became separated for long enough to become real resulting in hot big bang. Which is a little more plausible than a primordial atom and a singularity. Also Penroses Cosmic Cyclic Universe allows for multiple Big Bangs, which is interesting.

Once matter becomes real, gravity happens and slows down the inflationary stage of the universe to what we have today. As until galaxies slowly disappear over the visible horizon, and gravity is reduced inflation can occur again, resulting in another hot big bang.

How would FTL be detected in an inflationary stage of the universe, the clocks would simply go faster. It would only be detectable to an external observer.

Edit Variable speed of light theories do defy GR, Inflation driven by dark energy unrestricted by gravity does not. A link briefly discussing both Theory that challenges Einstein's physics could soon be put to the test, Also https://arxiv.org/pdf/0705.4507.pdf “Note on varying speed of light theories”

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#### Farsight

@Farsight thanks for the answers and links. I understand no one takes the concept Big Bang singularity seriously, this is why Inflation was developed by Guth and then modified by Linde. Your Links do not support the Lambda CDM model they criticise it

"The prevailing model of the Big Bang is based upon the GTR. According to this theory, extrapolation of the expansion of the universe backward in time yields an infinite mass-energy density and temperature at a finite time, approximately 13.8 billion years ago. Thus the “birth” of the universe appears to be associated with a singularity, which describes not only a breakdown of the GTR, but also all the laws of physics. This suggests a dubious assumption associated with the Big Bang hypothesis, indicating that the GTR with the FLRW metric is not valid for extremely small regions of space".
This claim is based on Penrose-Hawking singularity theorems, which are said to be in line with general relativity, but aren't. See singularities in collapsing stars and expanding universes where you can read that “the surface is in such a strong gravitational field that even light is dragged inwards”. This is absolutely wrong. In a gravitational field, the ascending light beam speeds up. In a strong gravitational field it speeds up even more. Einstein thought of the event horizon as the singularity. See his 1939 paper on a stationary system with spherical symmetry consisting of many gravitating masses. He said “g44 = (1 – μ/2r / 1 + μ/2r)² vanishes for r = μ/2. This means that a clock kept at this place would go at the rate zero”. He also said “In this sense the sphere r = μ/2 constitutes a place where the field is singular”.

Also in addition to this Dark matter is not required by Quantum theory, and has never been detected in the lab or by any other experiment.
But galaxies do exhibit flat rotation curves. There's more gravity than there ought to be.

My simple understanding is that during the inflationary stage of the universe virtual particles became separated for long enough to become real resulting in hot big bang.
Sorry, but virtual particles are virtual. They aren't short-lived real particles. The notion that they are is one of those "lies to children" that physicists tell because they don't understand why charged particles move towards one another and around one another and apart from one another.

Which is a little more plausible than a primordial atom and a singularity.
I'm no fan of point-singularities. I think of the early universe as something like a "frozen star". That was the original interpretation of a black hole, and I'm fairly sure it's correct. See Robert Oppenheimer and Hartland Snyder’s 1939 paper on continued gravitational contraction. Also see what Remo Ruffini and John Wheeler said in their 1971 article introducing the black hole: “in this sense the system is a frozen star”.

Also Penroses Cosmic Cyclic Universe allows for multiple Big Bangs, which is interesting.
I'm not a fan of Penrose.

Once matter becomes real, gravity happens and slows down the inflationary stage of the universe to what we have today. As until galaxies slowly disappear over the visible horizon, and gravity is reduced inflation can occur again, resulting in another hot big bang.
Sorry, but gravity doesn't slow down the expansion of the universe. A gravitational field is like a pressure gradient in space. The expansion of the universe occurs because space has a "cosmic pressure". Google on “dark energy” “cosmic pressure”. Erwin Schrodinger came up with cosmic pressure in 1918. See How Einstein Discovered Dark Energy by Alex Harvey.

How would FTL be detected in an inflationary stage of the universe, the clocks would simply go faster. It would only be detectable to an external observer.
That's right. The same is true if light moved very slowly in the early universe.

Edit Variable speed of light theories do defy GR
They don't defy Einstein's GR. He said the speed of light varied in a gravitational field time and time again. But after he died they changed the theory so that it's no longer true to the original.

Inflation driven by dark energy unrestricted by gravity does not. A link briefly discussing both Theory that challenges Einstein's physics could soon be put to the test, Also https://arxiv.org/pdf/0705.4507.pdf “Note on varying speed of light theories”
The speed of light varies, but it's slower when the energy density is higher, not faster. Magueijo has got it back to front.

#### interested

This claim is based on Penrose-Hawking singularity theorems, which are said to be in line with general relativity, but aren't. See singularities in collapsing stars and expanding universes where you can read that “the surface is in such a strong gravitational field that even light is dragged inwards”. This is absolutely wrong. In a gravitational field, the ascending light beam speeds up. In a strong gravitational field it speeds up even more. Einstein thought of the event horizon as the singularity. See his 1939 paper on a stationary system with spherical symmetry consisting of many gravitating masses. He said “g44 = (1 – μ/2r / 1 + μ/2r)² vanishes for r = μ/2. This means that a clock kept at this place would go at the rate zero”. He also said “In this sense the sphere r = μ/2 constitutes a place where the field is singular”.
The link doesnt work for me.
The clock speeds up as it ascends, the measured speed of light locally remains the same. But to a distant observer using the Shapiro effect, a difference might be expected. If the clock were to go at the rate zero, this implies a serious red shift in light. Light or a wave with zero frequency goes out of existence ie it loses all its energy to the gravitational field.

But galaxies do exhibit flat rotation curves. There's more gravity than there ought to be.
Exactly indicating that there is likely a problem with GR.

Sorry, but virtual particles are virtual. They aren't short-lived real particles. The notion that they are is one of those "lies to children" that physicists tell because they don't understand why charged particles move towards one another and around one another and apart from one another.
I think you are mistaken. Casimir effect springs to mind.

"Quantum mechanics allows, and indeed requires, temporary violations of conservation of energy, so one particle can become a pair of heavier particles (the so-called virtual particles), which quickly rejoin into the original particle as if they had never been there. If that were all that occurred we would still be confident that it was a real effect because it is an intrinsic part of quantum mechanics, which is extremely well tested, and is a complete and tightly woven theory--if any part of it were wrong the whole structure would collapse. "

Also check out the dynamic casimir effect.

PS how do you think charged particles move towards one another and around one another and apart from one another. If the likes of Feynman is mistaken ?

I'm not a fan of Penrose.
Neither am I. He does have some peculiarities, ie he is a bit odd I do not buy multiverses either, and suspect it is an example of stretching the math beyond reality.
The Cyclic universe theory he has is plausible, he is however struggling to find evidence for it.

Sorry, but gravity doesn't slow down the expansion of the universe. A gravitational field is like a pressure gradient in space. The expansion of the universe occurs because space has a "cosmic pressure". Google on “dark energy” “cosmic pressure”. Erwin Schrodinger came up with cosmic pressure in 1918. See How Einstein Discovered Dark Energy by Alex Harvey.
Dark Energy the cosmological constant expands space causing the distances between galaxies to increase. I guess this can be regarded as a radiation pressure between virtual particles/zero point energy of the vacuum. However when gravity is strong enough galaxies can and do devour other galaxies due to gravitational attraction. The space between those galaxies can be viewed as contracting.

They don't defy Einstein's GR. He said the speed of light varied in a gravitational field time and time again. But after he died they changed the theory so that it's no longer true to the original.
The fact is the speed of light is measured to be constant because of the reasons we have discussed. What we can observe is that time slows down in a gravitational field.

#### interested

@Farsight after due consideration ref the comments on the speed of light.

it is impossible to measure light to propagate at anything other than exactly c in a given medium; no experiment one can dream up can do that, just as no observer will ever see his own clock slow down. Of course you can look upon a distant frame and use your own local methods of assigning labels to events to come up with a figure for the speed of light in that remote frame; and you will find that it differs from what you measure locally. However, what you actually measured is not the speed of light, but simply how your local frame is related to that other remote frame. It's still valid, but only for you, not for the remote frame itself.

In GR it is clear that c is constant. Einsteins earlier comments ref VLS were thrown out when GR was finalised. I suspect you are confusing coordinate systems