I'm with Van.
I'm with Van.
[quote="Sam5"]I can wait.Originally Posted by Van Rijn
I'm still thinking about it.Originally Posted by Ricimer
take your time. I'm quick about it, cause I've been trained to think about such things (and all the physics behind it).
What's your solution?Originally Posted by Tensor
Ok, I’m tending to lean in the direction of your solution being correct.
Gosh Sam5, it almost sounds like you're saying that this slowing down of atomic clocks affects everything, almost as if time slows down itself!Originally Posted by Sam5
You never answered my question about whether or not you think that space is just flat, 3D Euclidean like. The reason I ask this is because, so far, all you've done is argue for a one particular description of gravitational redshift over another with no mention of how the two could be experimentally differentiated. But you have often made remarks about people "mystifying" it with spacetime descriptions. If you really believe that space is flat, then it is more than just a difference in description. You would, presumably, have your own account of Mercury's orbit for instance, given that you don't believe the warped spacetime explanation.
Hey, get out of here, boy! These guys want to talk in term of “time dilation” so I figure I’ll speak their language. If an atom slows down its oscillation rate in a gravity field, that can also be described in plain ol’ classical terms too. If you slow down your photongraph record the sound waves emitted will be lower. I call it tomAto and you call it tomaaahto.Originally Posted by worzel
*Note to young whippersnappers: A “phonograph” is what we old-timers used before we had CDs. Back in our day, CD meant “Civil Defense”.
Originally Posted by worzelWell, a serious question is actually whether you think this effect is limited to atoms. For example, when we observe spectral lines in the Sun's light, those are caused by atomic transitions, with the frequency governed by the electromagnetic force between the nucleus and the outer electrons. On the other hand, in Pund and Rebka's experiment, their "clocks" were actually nuclear rather than atomic. That is, they were looking at gamma rays emitted from the nuclei of atoms, so in that case the frequency of the radiation is controlled by the energy levels of the nucleus, which is bound instead by the strong force. So these two types of interactions actually have nothing to do with each other as far as the mechanisms involved are concerned. Yet it's interesting that in both cases, the change in frequency is given by the same relationship from general relativity, so the amount that a nuclear "clock" is slowed is precisely the same as the amount an atomic "clock" is slowed.Originally Posted by Sam5
You are, as ever, as clear as mud. One the one hand it is just a case of tomAtoes verses tomaaahtoes, and yet on the other, time dialation is somehow analogous to paying your 45 at 33. And apologies if it was a stupid one, but you still didn't answer my question.Originally Posted by Sam5
Originally Posted by Grey
Interesting, thanks for the description.
Another question is whether we think the effect depends on the gravitational forces being experienced by the atom/nucleus. Here is a thought experiment, and we can try the two explanations Sam5 has provided. Unfortunately, I can't think of a good way to conduct the experiment in reality.Originally Posted by Grey
Imagine something emitting photons at a constant frequency. It could be from electrons dropping through well defined energy levels in an atom or it could be from well defined excitation states of a nucleus.
Suppose we place such an emitter somewhere in a very high Earth orbit, and we also place an identical emitter at the center of the Earth, or in the center of any shell of matter, with a little hole for the photons to get out.
The total gravitational force experienced at the center of the Earth, or in the high orbit, is zero.
The photons emitted from the center of the Earth are then received in the high orbit, and compared with the photons produced by an identical emitter in orbit.
- Question 1. Will the photons from the center of the Earth will be redshifted?
I think they will be redshifted. I guess Sam5 might agree. I know Grey will agree.
There are two explanations for this. The one I prefer goes as follows:
- Explanation 1: We can calculate the time dilation of the emitter with respect to the receiver by applying relativity and considering paths from the emitter to the receiver. The emitter is running in exactly the same way as it does anywhere else, producing photons of a fixed characteristic frequency at the emitter. Due to differences in the passage of time at the emitter, and at the receiver, this frequency relative to the receiver is lower: a redshift. The receiver observes the photons with this redshift arising from time dilation.
Some other people here prefer a different explanation, which really corresponds to using a different co-ordinate system in GR.
- Explanation 2: The emitter is running in exactly the same way as it does anywhere else, producing photons of a fixed characteristic frequency at the emitter. As the photons travel from the emitter to the receiver, up through the gravitational field, they lose energy and their frequency drops. By the time they arrive at the receiver, they have the redshift that we can calculate by GR.
My preference for the first explanation is subjective. The second explanation is not really wrong. I'm inclined to think it can lead to confusions; but this thread has certainly shown me that the first explanation can lead to confusions as well! In any case, GR comes with the tools and techniques for mapping between co-ordinate systems, and giving a precise transformation from one explanation into the other.
Now as I understand the matter, Sam5 has a third explanation. However, I am not sure that Sam5 would agree, and he is welcome to correct my understanding of his position. The following explanation is my own wording, not that of Sam5.
- Explanation 3. The emitter actually behaves differently when at the center of the Earth, and the photons emitted have a different frequency. This frequency corresponds to the redshift seen by the observer.
Sam5 may confirm this, or not. If he confirms it, there is a problem… what physical laws can be used to calculate the emitter frequency? What are the variables involved? The emitter is weightless in both cases, so it can’t simply be the force experienced.
Cheers -- Sylas
Except that the typical "tired light" theories assume that light is losing energy due to some interaction, not because it was emitted in a gravitational potential different form the observer.Originally Posted by Sam5
The emission of light is not due to oscillations.Originally Posted by Sam5
Are you confusing emission of light with old-type atomic clocks?
Emission of light comes from electrons changing between states with different energy.
Old-type atomic clocks used molecules where one atom oscillates between two positions.
The gravitational red-shift is observed over the whole range of frequencies for EM emission, even those that have nothing to do with "atomic lock oscillation rates" or electronic transitions.
The tower experiment used gamma-radiation, which is produced by nuclear transitions in radioactive Fe nuclei (nothing to do with electrons).
Yep, you are confused.Originally Posted by Sam5
The light emitted is not the result of pendulum-like oscillations in atoms.Originally Posted by Sam5
And the effect is not restricted to light.
I think this is your fundamental misunderstanding. (We *are* talking GR here, right, not some sort of against-the-mainstream modification?)Originally Posted by Sam5
Most of us are talking about GR. Sam5's talking about some sort of against-the-mainstream modification.Originally Posted by jnik
Originally Posted by jnik
Well, there was a brief discussion about biological time (thermodynamic time) on this board a couple of weeks ago:
From the CNN source, (here):
“It works, essentially, like hypothermia. Recall those miraculous cases of people who fall into icy ponds and appear dead but recover after they're warmed up? The extreme cold preserves their brain cells from the certain death that would otherwise quickly follow oxygen deprivation.
Within minutes of inhaling the gas, the mice appeared unconscious. Their body temperature plummeted from the normal 98 degrees down to 59 degrees and their respiration slowed to fewer than 10 breaths a minute, down from a normal 120 breaths a minute, Roth reported.
Overall, their metabolic rate dropped by 90 percent -- meaning normal cellular activity slowed to almost a standstill, thus reducing the need for oxygen.”
I brought this very subject up here more than a year ago, and I tried to explain how it works. Some people might remember my “frozen embryo” posts. But the SR and GR relativists here didn’t like the idea since Einstein never mentioned it, so I just dropped the subject. You might want to look it up in biology books.
This basic idea is still ATM in the field of physics, but it has been very mainstream in the field of biology for many decades.
Weeks? Seems to me it's been years since you first brought up cryogenics in a relativity-related discussion on this BB.
And after all this time, you still don't understand that it's got nothing to do with it. Absolutely nothing.
Actually, I think it was a “time” related thread. I tried to explain the difference between the physics view of time, being mostly based on atomic time, and the biological view of time, being a thermodynamic phenomenon such as explained in the CNN news story. But nobody here seemed interested because Einstein never said much of anything about biological time.Originally Posted by SeanF
Remember how I tried to explain to you that Hawking was wrong about this, because he was thinking in terms of physics atomic time instead of biological thermodynamic time:
“Newton’s laws of motion put an end to the idea of absolute position in space. The theory of relativity gets rid of absolute time. Consider a pair of twins. Suppose that one twin goes to live on the top of a mountain while the other stays at sea level. The first twin would age faster than the second.”
A slowing down of biological time, as you call it, is a process actually slowing down. That is, the process takes longer. Time dilation in relativity is the slowing of time itself in one frame as viewed from another. You can measure the former in its own frame. You cannot measure the latter in your own frame, indeed the concept of time dilation in your own frame has no meaning.Originally Posted by Sam5
You obviously don't believe this, and think instead that time dilation is just the slowing down of some atomic process, but that is not what relativity says. If you accept that the speed of light is c in all intertial frames (and not just "appears to be") then how do you explain that without length contraction and time dilation?
Please, do not confuse metrology with physics.Originally Posted by Sam5
Metrology searches for standards of units, and having good standards does help.
If biological time is based on thermodynamics, it is already included in physics.Originally Posted by Sam5
When we say in Relativity that time slows down, it affects every physical process, including thermodynamic ones.
So both of the two relatively moving twins in SR see each other freeze?Originally Posted by papageno
Then how can the traveled clock in the “peculiar consequence” thought experiment in the SR theory “lag behind” the “stationary” clock when they unite? Wouldn’t the observer that traveled with the clock that traveled notice, in his own frame, that his own clock “lags behind” the other and therefore ran slow? And wouldn’t he actually notice that the other clock seemed to him to run fast during his travel?Originally Posted by worzel
The observer who travelled with the clock would not notice that his clock ran slowly, only that the other clock ran fast. The observer who didn't travel would not notice that his clock ran fast, only that the other clock ran slow.Originally Posted by Sam5
No, in SR theory both of two relatively moving observers see each other’s clocks run slow, with no exceptions.Originally Posted by worzel
I can sum it up more simply. First, just “relative motion” alone can’t slow down any clock. In the original SR theory, all motion is just “relative”, with no gravity or acceleration. All the SR stories about a traveling twin “aging more slowly” than a twin that “stays at home” is a lot of hokum, fable, and urban legend. It doesn’t happen. In the SR theory, both clocks are always inside “inertial frames” and the motion between the two clocks is just “relative”.Originally Posted by papageno
However, in GR theory, atomic clocks really do slow down in a gravity field and when accelerated, but the slow-down is so slight it can’t possibly ever affect human biological time. If an atomic-time slow-down occurred so much it began to affect human biological time, the human would be crushed to death by the extreme gravity/acceleration long before any biological time dilation effect would be noticed.
On the other hand, biological heat-time metabolism slow-downs are caused by temperature factors over just a slight change in temperature.
It is clear now that you do not grasp the concept of frame of reference and observer.Originally Posted by Sam5
Motion is "relative" also in the "original" Newtonian mechanics...Originally Posted by Sam5
But the frames of reference do not coincide, which is why transformations of coordinates are needed..Originally Posted by Sam5
I don't remember anybody claiming that it has been observed in biological process in humans. If somebody did, feel free to provide references.Originally Posted by Sam5
By the way, it does not work only for atomic clocks.
So, it does not mean that it would not happen in principle.Originally Posted by Sam5
So, what is the point? What does this have to do with gravitational redshift?Originally Posted by Sam5
Biological processes depend on chemical and thermodynamic processes, which do depend on temperature (thermo-, as in thermometer).
Why did you bring up "biological time"?
Because of all the silly thought experiments about “traveling twins” aging more slowly. These are fantasies, sci-fi stories.Originally Posted by papageno
Sorry, but there are a lot of people at CERN, Fermilab, Brookhaven, Stanford, Dubna, Serpukhov, Hamburg, etc. who see this every day at their particle accelerators. It is no "urban legend". [-(Originally Posted by Sam5
The keyword in your post is “accelerator”. I’ve already mentioned acceleration effects.Originally Posted by Celestial Mechanic