joigus

"Occasionally, an obsession does turn out to be something good." Chen Ning Yang The key word here is "occasionally." "It was a crazy idea, I grabbed the back of a napkin and did the necessary calculations." Murray Gell-Mann The key words here are "necessary calculations."

Interesting... Tidal effects come to mind at your suggestion, because those are second-order effects, which requires an order-2 tensor.

Boy, was that a good explanation! +1 And this was intended as a joke. Coordinates mean nothing, it's the metric tensor contracted with the coordinates, as Markus so brilliantly has explained. Just to clarify...

That's only because I'm a remote object, and you're giving me the wrong coordinates. Apology accepted.

Don't put words in my keyboard. The only one who believes in remote dilation as a frame-independent phenomenon here is you! That remote dilation is only in your mind. You don't even understand that, which says all about you as a "thinker." The fact of whether something suffers frame-dependent dilation or not does involve having things other than photons in it. In fact, in order to write down the geodesic equation for photons you must do an affine transformation, because their proper time is identically zero, so no common-sense clocking will help you describe their histories. But what am I telling you; you know next to nothing about relativity, that not being the worst. The worst being that you don't bother to examine your own assumptions, or anybody's criticism. Can you imagine Einstein telling Hilbert "please consider my silly mistake as a valid assumption"? Einstein quickly re-wrote his paper. Learnt much from Hilbert, and went on to publish one of the most important papers in the history of physics. I will pop up every now and then to see what experts and other serious thinkers have to say. Your post is only valuable in that sense. The only trouble is I will have to check for you twisting everything I or anybody else has said, just because you don't understand the first thing about relativity, you don't read what you write, let alone others, and you stubbornly stick to a bunch of silly pseudo-scientific propositions to no end.

You're most welcome. It's such a pleasure to break the spell. Good luck to everybody else.

And I've I told you: MigL also told you: And, along the same lines, I said: IOW, it's not t2-t1 for the arrival times of the signals that mark up the ticking of the clock --the perceived time, which is the thing you seem to be thinking about, although nobody can be sure-- what determines the clock's ticking, it's the mean average of tout and tin. tout and tin being the delays in the forward and backward trip of your signals. The process repeated for 2 fiducial ticks of the remote clock, and then the calculation. The source of all your inconsistencies about "remote clocks" starts, I'm sure, from the very simple fact that you don't understand what it means to measure time in SR, let alone in GR, which is affected by second order derivatives. There are as many as 20 independent ones, that's known since the 19th Century. We could talk Einstein, we could talk Weyl if you want, but let's drop the tensors for a while, if you please. Please, tell me that you recognize something like what follows in terms of outgoing and ingoing signals in order to define coordinate time: \[t=\frac{1}{2}\left(t_{\textrm{out}}+t_{\textrm{in}}\right)\] where tout is the coordinate time of signal sending in your system, and tin is the coordinate time of signal receiving in your system. The coordinate time of distant events must be defined in terms of the times signals delay. k-calculus was developed by H. Bondi and is a very simple tool to understand this, and if you take my advise and read carefully chapter 1 of D'Inverno, which I recommended you, you will understand. IOW, you can keep your own close observations as your clock, so to speak, but for remote objects, you must send signals and, upon receiving them back, guess the coordinate time for the distant object. It's always like that in any relativity, S or G. Please, oh please, try to understand that and maybe we can talk about something meaningful and go on to tensors. Otherwise nothing we discuss is going to be meaningful. I think that's a preliminary requisite. I don't have much time, sorry if I mistyped or made another similar mistake.

Because I was the one to mention radiation pressure, and just to clarify, I never intended to argue that radiation pressure is a plausible point of departure to build the components of either the energy-momentum tensor, or the Einstein tensor, or anything else in GR. It was intended as a simple illustration that the slowing down of clocks (a frame-dependent effect, as I've repeated here to the OP till I got blue in the face) has nothing to do with the slowing down of photons. And it was in response to this rather bizarre statement by the OP: (my emphasis) And as photons do not slow down in any sense that I know of in a gravitational field, and please correct me if I'm wrong, I surmised that if a clock made of photons (and necessarily other things non-photonic) does slow down in a gravitational field, what other reason could it be attributed to but the fact that it's not made just out of photons, but also massive / charged matter interacting with them? IOW, the photons that are going back and forth inside the clock cannot be accountable for the slowing down of the clock, but the presence of the cavity, with which they interact. What the detailed analysis of this interaction would be is another matter, which I won't even try to analyze here or elsewhere. But there, that's how else you could explain it: because it's not 'just' photons falling! On the other hand, I totally agree with what the experts have said as far as I've been able to read and understand. And specifically concur totally with the point that considering space-time as a "medium" is completely the wrong way to try to approach it. My last point, and sorry for the lengthy argument. I'm not saying that GR is necessarily to stay with us forever, or that I'm 100 % sure of its total infallibility. But for anybody who claims to have come up with something new and/or better to supersede it or rival it, as Strange has been the most insistent to say on on this forum (from which the only thing of interest is the opinion of the learned people who have responded to the tsunami of nonsense) the minimum required is to reproduce its many impressive results. And sorry for the diacritics. They're just to emphasize what I consider the important points I want to make.

Only case in which I thought that could make any sense is about static solutions. But not even there. Thank you very much. +1 Eqs. rendered badly, prob. because insertion of HTLM tags. Dunno. Anyway, I meant, To be more precise. Einstein demanded, \[ \sqrt{-g}=1\] with, \[g=\textrm{det}g_{\mu\nu}\] which, as Hilbert pointed out, can't be in a diffeomorphism invariant theory. His first version of field eqs. was, \[R_{\mu\nu}=\frac{8\pi G}{c^{4}} T_{\mu\nu}\] which doesn't covariantly conserve matter energy, his goal. As, \[D_{\mu}R^{\mu\nu}\neq0\] The moral of all this: Einstein was carefully scanning for mistakes in his proposal. You don't come across like you are, rjbeery.

To be more precise. Einstein demanded, \[\sqrt{-g}=1\] with, \[g=\textrm{det}g_{\mu\nu}\] which, as Hilbert pointed out, can't be in a diffeomorphism invariant theory. His first version of field eqs. was, \[R_{\mu\nu}=8\pi GT_{\mu\nu}\] which doesn't covariantly conserve matter energy, his goal. As, \[D_{\mu}R^{\mu\nu}\neq0\]

That's very interesting. Thank you. The concept of photons was Einstein's pride and joy, but it took decades for people to buy into it. It's not an easy concept and it remains so to this day. At the time when he published GR's founding papers, the concept hadn't still made it through the barrier of incredulity. Another thing is the concept of "invariance under general coordinate transformations," which to this day finds physicists discussing as to what it means exactly. In my opinion, it was a simplifying assumption that Einstein took, because he was in direct competition with David Hilbert to be the one to get first at the final form of the field equations. AAMOF, Einstein made a mistake on the first paper, including a condition that the determinant of minus the metric be 1, which is not an invariant constraint. Hilbert immediately noticed, and so told him. Einstein corrected it, and went on to learn about the Ricci tensor, which gave him the final form of the field equations. So did Hilbert too. Science historians admit today that Einstein got there first.

Right you are. It's absorbing photons. I hadn't noticed. Thank you. But as far as I've been able to read the photon clock made in Caltech does use radiation pressure. The point I was trying to make is that if you build a periodic system (clock) by having photons bounce back and forth, such photons aren't free-falling anymore; they are interacting by means of non-gravitational forces. What the OP was arguing, at the point that the question surfaced, was that free-falling photons must slow down. The reason being (as I understood the OP) that bouncing photons in a photon clock must slow down too to account for time dilation and length contraction. My argument, IOW: any such clock is not just made of photons bouncing in mid air, so to speak. It involves matter and interactions.

This is only valid for static solutions!

And it does. Welcome to our world (the real one.) Radiation pressure is proportional to the number of photons per unit time that hit the mirror and the average energy of the photons, which is, \[\hbar\omega\] which is affected by frame-dependence. Inverse time transforms exactly like frequency. In GR is a bit more complicated, but it can be locally understood in terms of inertial frames. So it's not an invariant (or your cryptic "absolute" word.) Radiation pressure is a frame-dependent object as well. I rest my case. This is about the first time that you've asked a question. I think you can learn some relativity in a reasonable time (compared to Eddington's years) today thanks to the fact that you've got lots of material, in the form of online courses. Many people here can help you. There are wonderful free e-books out there. You're not dumb, you're just sticking to your guns to the point of nonsense. You can teach yourself relativity by reading good books and following excellent courses, but you've wandered alone for too long. Neither Einstein nor Eddington were lone wanderers. Every (static) exact solution in GR carries with it what you call an acceleration field. What the meaning of it is is far less clear to me. What's sure is that changing coordinates to locally flat (inertial) takes you to what the free-falling observer sees. But the starting point from the exact solution is far less clear in my opinion. I'm looking forward to what the experts in this community have to say. Mercury's precession is already a solved problem to 43'' of arc per century. Bettering that is a pretty tall order. I would start with vector calculus and a relatively simple model of field theory, like Maxwell's equations. When Einstein postulated his equations, he took Maxwell's as a model.

Missed this. This really says it all. A viewing angel is telling me from nth layer that you're mistaken. Cheers

So you do dimensional analysis... I'm impressed!

Blimey! 7 years! No wonder he's experiencing time dilation. Thanks a lot, Studiot.

Thank you, Markus. Although you've shot too far ahead for him. I can't +1-you because I've run out of points.

'Absorption and instantaneous re-emission' was a colloquial way of saying 'radiation pressure' of the photons on the cavity where you're confining them to make the clock. I said that to have you picture in your mind that the photons are interacting within the clock by means of non-gravitational forces. Then I rephrased it as 'radiation pressure,' just to see whether you understood it better: Then, on your linked Caltech article (https://www.caltech.edu/about/news/caltech-scientists-create-tiny-photon-clock-1029😞 Lo and behold, your Caltech publication confirms my diagnostic. What was I telling you? Radiation pressure. You've missed the point completely. That's what makes your clock be affected by time dilation (never mind it's made of photons.) And I, and everybody here, is tired of repeating to you, but there it goes once more: Time dilation is a frame-dependent effect. As I spent many hours, c. 1990, thinking about toy models for massive elementary particles made up of bouncing photons (massless) and had to rule them out because I wasn't able to postulate the self-interaction, I know what I'm talking about. IOW, I had the same idea (just the non-crazy snippet) than you 30 years ago and it took me less than 24 hours to throw it in the garbage can. I didn't in my wildest dreams try to model gravity with that, though. And please, don't try to smother me with big names like Eddington or Feynman to try and push ahead a crazy idea. We're all grown-ups here, or are we?

I never said that. The bouncing photon clock that you talked about involves photons interacting with matter, which no longer is a photon travelling through the gravitational field. Such system, with two parallel mirrors and a photon bouncing back and forth, doesn't work like you claim it does. If you ever see a radiation pressure fan or radiometer, you will understand what I mean just looking at it. You won't have to think or listen to anybody, or read what they say, which for you is a definite advantage: photons push against a mirror, you see? That's why your idea didn't work. But I'm starting to lose track of what you're saying. You've talked so much nonsense today I can't keep track. Now those are real photons, not the ones that are in your mind. Cheers

Yes, this is Richard Feynman in 1965. Have you heard of entropic gravity? Erik Verlinde deduces Einstein's equations and Newton's laws. And it is by no means sure it is the right theory: https://en.wikipedia.org/wiki/Entropic_gravity#Criticism_and_experimental_tests IOW, people don't buy it just yet. Why should scientists pay more attention to you than to Verlinde, for example? Com'on, don't make a fool of yourself any longer. This is really painful to witness.

rjbeery, I'm giving you some homework: https://www.amazon.com/Introducing-Einsteins-Relativity-Ray-dInverno/dp/0198596863 You don't sound to me like you're completely off your rocker. Maybe you've tried to get into the forest a little too deep, a little too devil-may-care, and without dropping your breadcrumbs on the floor. I don't want to be completely negative. So there you are.

When a particle is massive, wavelength has to do with mass by De Broglie's relation, \[p=mv=\frac{h}{\lambda}\] p is called 'momentum.' m is the particle's mass, v is the particle's velocity, \lambda is the wavelength and h is Planck's constant. For photons though, it's also, \[p=\frac{h}{\lambda}\] But expressing p as mv is no longer valid. So the photon's wavelength has nothing to do with its mass.

1) I do not believe anything, I need, demand AAMOF in this context, logical proof or experimental evidence. You have neither. 2) Clock rate is a relative (frame-dependent) quantity. Plus you only too obviously don't understand special relativity, let alone GR.

Before re-iterating too much, I would suggest you re-read what people are telling you, and then re-think for a change.