Fact Check, debunking obviously false information

Quote from JohnDuffield

It doesn't matter how they look at the optical clock readings. Whatever method they use, they get a reading that says the lower optical clock goes slower than the upper optical clock. No observer sees the lower clock going faster. I don't need to account for photons travelling through a gravitational field. Not when I can show you Einstein saying "the speed of light is spatially variable” year after year. Read this:

https://en.wikipedia.org/wiki/Variable_speed_of_light#Einstein's_updated_proposals_(1905–1915)

I still don't understand your claim. Are you saying that a group of tiny scientists living inside the top clock would measure a different value for the speed of light than a second group of tiny scientists living in the bottom clock?

Quote from THHuxleynew

You have been arguing for 3 pages that it implies a variable speed of light when as I pointed out above there are two other possible things that could cause it: a change in relative time rate, or a change in distance travelled.

Huxley, you should take a tip of Einstein's operational definition of time, and you should take a cold empirical look at what clocks do. A clock is not some cosmic gas meter with time flowing through it. A clock as a contraption that features some kind of regular cyclical motion, which is counted and/or accumulated then displayed as "the time". That's it. The clue is in what the inner workings of a mechanical clock is called. It's called a movement. When a mechanical clock goes slower it's because the movement goes slower. When an optical clock goes slower it's because the light goes slower.

So your "change in relative time rate" just doesn't cut it. Nor does your "change in distance travelled". Why? Because the metre is “the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458^th of a second”. So when light goes slower the second is bigger, and the slower light and the bigger second cancel each other out. So the metre is unchanged.

Quote from Wyttenbach

It should be the other way round because gravity at the lower clock position squeezes the orbit.

It isn't. Remember this: Light goes slower when it's lower. Gravity is there because of this. If you were in a room where the lower optical clock went at the same rate as the upper optical clock, your pencil wouldn't fall down.

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This would, imply that the photon at a certain point in space/time has no energy at all....

It doesn't. The energy is where the four-potential is. E is where the four-potential varies spatially, B is where it varies over time. The four-potential is at a maximum in the middle of the photon where E and B are zero. See the Wikipedia Aharonov-Bohm article, which says Feynman wished he’d been taught electromagnetism from the perspective of electromagnetic potential rather than electromagnetic fields. I wish everybody was taught from that perspective. IMHO most physicists today don't understand electromagnetism, just as they don't understand gravity.

Quote from Bruce__H

I still don't understand your claim. Are you saying that a group of tiny scientists living inside the top clock would measure a different value for the speed of light than a second group of tiny scientists living in the bottom clock?

No. I'm saying a group of normal-size scientists would look at the lower optical clock and notice that it was going slower than the upper optical clock. Again, 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”. Both clocks are optical clocks. The lower clock goes slower because light goes slower when it's lower.

As for your hypothetical tiny scientists living inside the bottom clock, light goes slower when it's lower and so do they, because of the wave nature of matter. So they might think the speed of light is constant, but they'd be wrong. Check out Irwin Shapiro's 1964 paper on the Shapiro delay. Wikipedia faithfully quotes what he said: “the speed of a light wave depends on the strength of the gravitational potential along its path”. For some strange reason this now seems to be some lost secret of the ancients.

Quote from JohnDuffield

he four-potential is at a maximum in the middle of the photon where E and B are zero.

The true absolute E/B fields are complex and thus not zero at the same time. The logic above works only for the real part.

Quote from JohnDuffield

It isn't. Remember this: Light goes slower when it's lower.

This is was the "true" clock says. But you say time is based on path length of light, that in fact is shorter in the lower position and we thus should see the opposite behavior.

I believe we cannot separate a single behavior (speed of light) from the over all atomic clock behavior that is working slower - most likely because the electronics (bound electrons ) that is true mass based follows gravitation laws. Also the emitting nucleus is much more affected by gravity than the final measured photon.

"For example, gravity affects the rate that clocks run. One of the effects of gravity comes from Einstein's theory of general relativity. And one of the consequences of Einstein's theory of general relativity was that clocks, if they're placed near a gravitational mass, say the Earth—will run at a slower rate than if they're removed from the source—say clocks on a satellite."

That's a quote from David J Wineland, a Nobel Prize wining physicist, no less. Straight from Duffield's link. I'm surprised there's much argument over this.

Quote from Zeus46

That's a quote from David J Wineland, a Nobel Prize wining physicist, no less. Straight from Duffield's link. I'm surprised there's much argument over this.

Nobody is arguing about this. The connection to light (going slower) is the problem.

Thank you Zeus.

Wyttenbach: time is based on the motion of light. You sit there counting those caesium hyperfine light waves go by, and when you get to 9,192,631,770, that duration is a second. See what I said above about the metre. It's “the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458^th of a second”. So when light goes slower the second is bigger and the slower light and the bigger second cancel each other out. So the metre is unchanged.

Re separating a single behavior (speed of light), and electron is just light going round and round. It's the wave nature of matter. The same principle applies to protons. That's why protons also go round in circles in a uniform magnetic field. And why in low-energy proton-antiproton annihilation, we see gamma photons.

Annihilation images from CSIRO Australia Telescope National Facility

Quote from JohnDuffield

So your "change in relative time rate" just doesn't cut it. Nor does your "change in distance travelled". Why? Because the metre is “the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458^th of a second”. So when light goes slower the second is bigger, and the slower light and the bigger second cancel each other out. So the metre is unchanged.

You bring up standard definitions. And they make my case, the speed of light is by definition constant (for length defined as here).

Which is consistent with what 99.9% of people agree, but John here does not like:

In an accelerating frame c stays constant, but time dilates, relative to an inertial frame. According to the principle of general relativity, a gravitational field is equivalent to an accelerating frame.

So when light goes slower the second is bigger

Here we are again. Making a comparison between two frames F1, F2 where the gravitational field in F2 is larger than in F1. A 299792458m path in each frame will mean that light takes 1s frame time to travel the path. Time dilation of F2 relative to F1 means that 1s runs relatively slower.

Thus: speed is constant, time dilates => more fewer bounces observed in F2 than F1 for an observer in F1 (or F2).

John's confusion here is that in spite of studying general relativity he makes non-relativistic arguments.

Quote from THHuxleynew

You bring up standard definitions. And they make my case, the speed of light is by definition constant (for length defined as here).

Which is consistent with what 99.9% of people agree, but John here does not like:

In an accelerating frame c stays constant, but time dilates, relative to an inertial frame. According to the principle of general relativity, a gravitational field is equivalent to an accelerating frame.

it isn't just me saying the speed of light varies. Einstein said the speed of light varies, Irwin Shapiro said the speed of light varies. Don Koks says the speed of light varies. Ned Wright says the speed of light varies. See his Deflection and Delay of Light article. He doesn’t say the light is deflected because spacetime is curved. Instead he says this: “In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light. The figure below shows a bundle of rays passing the Sun at various distances”:

Gif from Ned Wright’s Deflection and Delay of Light

That delay is the Shapiro delay. It's there because "according to the general theory, the speed of a light wave depends on the strength of the gravitational potential along its path". The hard scientific evidence of NIST optical clocks says the speed of light varies. See what Wikipedia says: "Division of a scalar by a vector is not defined, so there is no other way to interpret the velocity of light in this usage except as a variable scalar speed". It also says this: "Peter Bergmann did not agree with Einstein, but left the dispute out of his earlier book in 1942 to get Einstein’s endorsement. After Einstein died Bergmann wrote a new book 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". I didn't write this article. I'm sorry Huxley, but what you think is general relativity, isn't the real thing. And in some important respects, when it comes to black holes, it's wrong. Because light can't go slower than stopped.

Quote from THHuxleynew

So when light goes slower the second is bigger

Here we are again. Making a comparison between two frames F1, F2 where the gravitational field in F2 is larger than in F1. A 299792458m path in each frame will mean that light takes 1s frame time to travel the path. Time dilation of F2 relative to F1 means that 1s runs relatively slower.

Those frames do not exist. The room you're in exists. The two optical clocks exist. Light exists. And the lower clock is going slower than the upper clock because light goes slower when its lower. It's that simple Huxley. There is no magical mysterious thing called time going slower inside those clocks. Have you never heard of A World without Time: The Forgotten Legacy of Godel and Einstein? PS: The clock rate depends on gravitational potential, not field, which is the gradient in potential. We say potential is lower at the lower elevation

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Thus: speed is constant, time dilates => more fewer bounces observed in F2 than F1 for an observer in F1 (or F2).

John's confusion here is that in spite of studying general relativity he makes non-relativistic arguments.

I'm not confused at all. Einstein was crystal clear: “Second, this consequence shows that the law of the constancy of the speed of light no longer holds, according to the general theory of relativity, in spaces that have gravitational fields. As a simple geometric consideration shows, the curvature of light rays occurs only in spaces where the speed of light is spatially variable”. You would dismiss Einstein and the evidence, and claim that the light pulse in the lower parallel-mirror clock is moving at the same speed as the light pulse in the upper clock? Let me assure you, it isn't. And by the way, the metre doesn't change, as I explained above.

Gif image by Brian McPherson

To summarise. JD has two bete noir:

(1) The speed of light varies. This is not necessarily wrong: there are versions of GR with variable c compatible with observations. To first order it is just a redefinition of what you mean by speed, and time, as shown in my replies above. However JD's reasons for maintaining this are not 2nd order effects (which he has never addressed), nor has he even done the math for the 1st order effects. He does so because "Einstein said it" - a bad idea to fix ones ideas about a physics theory on one historical personage.

(2) Worldlines falling into a black hole crossing an event horizon are "impossible". This is a clear factual error, JD's reasons for disliking this "it is ludicrous" don't wash, and he has not one shred of evidence. You cannot have equations compatible with the observations without such asymptotes (at least not simple ones, as Einstein wrote and have been elaborated since). Note that the event horizon creates an asymptotic and discontinuous releationship between time in two reference frames but is not a singularity - the normal equations work just fine there.

It is not clear to me whether JD has any observational predictions that differ from GR. I cannot find them in what he is posted, so his comments here have the demerit of being both wrong and uninteresting.

https://en.wikipedia.org/wiki/…s_for_a_range_of_theories

A great list of alternative GR theories noting which have now been ruled out by observations. There are still other (reasonably simple) theories possible, but less than previously now the gravitational waves have been detected and shown to travel at the (constant) speed of light.

We have got to the point where more would be repetitive even for me, so I will block JD. Please, if he posts anything new, and interesting, will others quote it and let me know?

Quote from THHuxleynew

(1) The speed of light varies.

Unluckily experiments down on earth on different altitudes did not yet show a different speed of light. Thus we should not discuss about things we can't measure as the decision is made by experiments and not by theory.

The frequency of the light in an atomic clock is defined by the vibration of the atom (bound electron) and not by the varying speed of light. Atoms do not follow GER but they follow gravity.

To make things even worse: Gravity is not a constant as the SO(4) formula shows, it slightly depends on the binding force of an electron. (This, varying g is also what experiments tell.)

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Unluckily experiments down on earth on different altitudes did not yet show a different speed of light. Thus we should not discuss about things we can't measure as the decision is made by experiments and not by theory.

After then the observations like Shapiro delay or gravitational lensing shouldn't be possible. I already explained here that constant speed of light applies only to INTRINSIC perspective, where observer is allowed to deform his time and meter rule together with space-time (i.e. with using lasers prototypes of time and space). Under such a situation the speed of light would be really invariant, because it's defined so by SI unit system. But I'm pretty sure, that if we would use good old iridium meter prototype we would measure different speed of light even here at Earth.

Thanks to NTP the dependency of speed of light on gravitational potential can measure everyone of us in essence. Everything what is required to do is to measure the length of day by pointing to some bright star by small telescope connected to photometer. You'll find it modulated by location of planets, by location of Jupiter planet in 5.9 year period in particular.

BTW The length of day also correlates with global temperatures, because longer trends in gravitational potential are affected by dark matter (distribution of planets across solar system) too.

Quote from Wyttenbach

Unluckily experiments down on earth on different altitudes did not yet show a different speed of light. Thus we should not discuss about things we can't measure as the decision is made by experiments and not by theory.

The frequency of the light in an atomic clock is defined by the vibration of the atom (bound electron) and not by the varying speed of light. Atoms do not follow GER but they follow gravity.

Experiments do show a varying speed of light. The NIST optical clock goes slower when it's lower. It's an optical clock. There is no thing called "time" going slower inside this clock. Zephir is right.

Yes, the frequency of the light in an atom is defined by the electron. But we can make an electron out of light in gamma-gamma pair production. Then when we annihilate it with the positron, we get light again. The electron is just light in a closed path. I would urge you to read Erwin Schrödinger's quantization as a problem of proper values, part II. He talked about wavefunction and phase and geometrical optics, and on page 18 said classical mechanics fails for very small dimensions of the path and for very great curvature. He said “let us think of a wave group of the nature described above, which in some way gets into a small closed ‘path’, whose dimensions are of the order of the wave length”. He was talking about the electron.

The point to note here is that what Huxley is saying, is that the speed of the two light pulses in the gif is defined to be the same. Take a look at them. Yes, the gif is exaggerated, but it's essentially correct. Do they look as if they're moving at the same speed to you? They are not. Einstein was right. So was Shapiro. So is Koks, and Wright, and a growing number of other people who now understand the tautology.

Zephyr,

You'll find it modulated by location of planets, by location of Jupiter planet in 5.9 year period in particular

That is fascinating. My gut tells me that any GR gravitational effect on length of day due to the extra potential from Jupiter is far too small to be so measured. However a direct change due to the earth's orbit changing slightly is very possible.

Also time dilation on earth will not alter the length of the earth day as measured by an earth atomic clock. Will it?

Gravitational time dilation is a phenomenon predicted by the theory of General Relativity whereby time passes more slowly in regions of lower gravitational potential. Scientists used the lander to test this hypothesis, by sending radio signals to the lander on Mars, and instructing the lander to send back signals, in cases which sometimes included the signal passing close to the Sun. Scientists found that the observed Shapiro delays of the signals matched the predictions of General Relativity

What definitely has been measured is the time dilation caused in signals passing close to the sun (and I'd expect Jupiter as well).

Looking up the Shapiro effect we get the details:

https://en.wikipedia.org/wiki/Shapiro_time_delay

Change of path causes only second order change in time, whereas time dilation causes 1st order change.

https://en.wikipedia.org/wiki/Day_length_fluctuations

Wikipedia thinks changes in the length of the day are due to angular momentum exchange between earth and atmosphere, oceans (and maybe the earth's core).