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And the higher one runs faster, no? The observer has to be somewhere!
No. He looks down and sees that the lower clock appears to be running slower than his, and looks up to see the higher clock apparently running faster than his. If he was below the lower clock, both would appear to be running faster.Here's an old story that explains a lot. A politician, a statistician and a physicist were travelling through Peru in a train. They saw two cows in a field, one black, one white. The politician said "the overwhelming majority of Peruvian cows are black". The statistician said "on a possibly nonrepresentative sample of two frrom an unknown population, my best estimate is that half the cows in Peru are black". The physicist said "At 1800GMT on 23 June 2014 I saw two bovine quadrupeds in a field in Peru. At least one side of one of them was black."Stick to physics and you won't go far wrong!
Faster than what? As far as an observer next to the clock is concerned, it is running at exactly the same speed, wherever it happens to be in the universe, because whatever he is using to measure it, is also at the same gravitational potential. The surface of the earth is not a special point in the universe. Indeed, identical "surface" primary standard clocks at NIST Boulder (altitude 1655m) and NPL Teddington (altitude 3m) run at different rates as seen by each other. Which one is correct? The answer is, of course, "both", because they both use the same fundamental property that is unaffected by any extermal influence. And the same is true of the clock on a space probe, whether in a zero gravity field or approaching Jupiter or a black hole. The explanation is that time is warped by a gravitational field, and calculations based on known gravitational fields fortunately yield correct clock variation factors, so GR is at least selfconsistent, explanatory and predictive, even if it doesn't explain everything.
They all are as far as I'm concerned, but we measure physics via the standard second and any variations can be held relative to a standard second.
One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.
QuoteThey all are as far as I'm concerned, but we measure physics via the standard second and any variations can be held relative to a standard second.QuoteOne second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.No suggestion of where in the universe, because it is exactly the same everywhere. The underlying principle of relativity is that physics doesn't change, because there are no special places in the universe, but our perception at point A of what is happening at point B depends on the relative speed and gravitational potential of A and B.
NIST proved that the cycles of radiation are increased in frequency when placed in the higher gravity potential.
Newly developed optical clocks are so precise that they register the passage of time differently at elevations of just a few dozen centimeters or velocities of a few meters per second
QuoteNIST proved that the cycles of radiation are increased in frequency when placed in the higher gravity potential.That is impossible, thanks to the equivalence principle. You can only measure the frequency of a clock with another clock. What they measured was the increase in frequency of the elevated clock as seen from the lower clock. Or the decerease in frequency of the lower clock as seen from the upper one. Note the Scientific American headlineQuoteNewly developed optical clocks are so precise that they register the passage of time differently at elevations of just a few dozen centimeters or velocities of a few meters per secondi.e. it isn't the clock that changes, but time.
but it is observed that the frequency of its cycles is increased.
Quote from: alancalverd on 21/07/2016 17:51:47QuoteNIST proved that the cycles of radiation are increased in frequency when placed in the higher gravity potential.That is impossible, thanks to the equivalence principle. You can only measure the frequency of a clock with another clock. What they measured was the increase in frequency of the elevated clock as seen from the lower clock. Or the decerease in frequency of the lower clock as seen from the upper one. Note the Scientific American headlineQuoteNewly developed optical clocks are so precise that they register the passage of time differently at elevations of just a few dozen centimeters or velocities of a few meters per secondi.e. it isn't the clock that changes, but time.Good. Maybe we might be getting somewhere.
Placing clocks in elevation every metre and using the clock on the ground as a standard, we can then say by how much faster each clock is running faster than the clock on the ground.
You say the clock does not physically change, but it is observed that the frequency of its cycles is increased.You are saying this is because time is running faster at that elevated location. Time runs faster there because the gravity field shifts in time.
I am suggesting that it is the atom that is shifted by the gravity field, and that its frequency increases because of the addition of gravity potential energy at elevation. All atoms will be shifted in frequency and energy in elevation proportionally, and the equivalence principle is upheld.
Now it is possible to view the gravity field itself (open space) as being subject to inverted time dilation, where time runs slower in the weaker gravity field.Looking at the red shift blue shift phenomenon, light when travelling through space, is always of a lesser frequency in the weaker gravity field. Light viewed without relativistic mass is not subject to gravity potential energy.
Quotebut it is observed that the frequency of its cycles is increased. note the word OBSERVED, and it is only as observed FROM BELOW. You cannot measure any change in frequency of you are at the same level as the clock, because the clock has not changed. If it had, you would get different results with different clocks or different mossbauer photons, but you don't. The fractional frequency shift is exactly the same for all sources, regardless of mechanism, so it's nothing to do with the source. So all the stuff about the atom's frequency changing is nonsense.
All of the wiki, text books, clock data, etc, all state that the cesium atom's cycles increase in frequency in the higher gravity potential.
A prediction of General Relativity is that clocks closer to a massive object will SEEM to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites APPEAR to be ticking faster than identical clocks on the ground.
QuoteAll of the wiki, text books, clock data, etc, all state that the cesium atom's cycles increase in frequency in the higher gravity potential.No they don't, because that would be wrong. Here, for example , is a standard (Ohio State University) text on GPS time correctionQuoteA prediction of General Relativity is that clocks closer to a massive object will SEEM to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites APPEAR to be ticking faster than identical clocks on the ground. My capitals. Note the non-magic words of physics. There is no suggestion that anything has happened to the clocks, because nothing can happen to them. If it did, the effect would be different for different clocks, but it is exactly the same for all mechanisms (apart from pendulums, obviously) .
Look Alan - NIST conducted tests on clocks that were 1metre apart in elevation. Both clocks can be observed simultaneously...
The NIST experiments focused on two scenarios predicted by Einstein's theories of relativity. First, when two clocks are subjected to unequal gravitational forces due to their different elevations above the surface of the Earth, the higher clock—experiencing a smaller gravitational force—runs faster. Second, when an observer is moving, a stationary clock's tick appears to last longer, so the clock appears to run slow.
Quote from: timey on 22/07/2016 05:29:15Look Alan - NIST conducted tests on clocks that were 1metre apart in elevation. Both clocks can be observed simultaneously...I googled up and found this articlehttp://www.nist.gov/public_affairs/releases/aluminum-atomic-clock_092310.cfmQuoteThe NIST experiments focused on two scenarios predicted by Einstein's theories of relativity. First, when two clocks are subjected to unequal gravitational forces due to their different elevations above the surface of the Earth, the higher clock—experiencing a smaller gravitational force—runs faster. Second, when an observer is moving, a stationary clock's tick appears to last longer, so the clock appears to run slow.I'm curious about the first experiment, whether the higher clock really runs faster due to smaller gravitational force, or it was actually due to higher gravitational potential. To resolve this, they can repeat this experiment underground.If the difference is really due to gravitational force, then the result of the underground experiment should be flipped (higher clock would run slower than lower clock due to bigger gravitational force).If the result still the same, then the difference would be caused by gravitational potential.
Both clocks can be observed simultaneously...
The experiment I have devised to test my theory suggests holding 2 atomic clocks (edit: on ground) at the exact same elevation from sea level (accounting for and avoiding equatorial bulge factor) so that the clocks are experiencing equal gravity potential, but placed in locations of know significant difference of geological density.
QuoteBoth clocks can be observed simultaneously... And where was the observer? He can't have been at both elevations simultaneously!QuoteThe experiment I have devised to test my theory suggests holding 2 atomic clocks (edit: on ground) at the exact same elevation from sea level (accounting for and avoiding equatorial bulge factor) so that the clocks are experiencing equal gravity potential, but placed in locations of know significant difference of geological density.You won't have much luck if you rely on geology, but you could do a much more sensitive experiment, much more easily, by surrounding a cesium clock with lead bricks and seeing if it speeds up or slows down when compared with another one.If it's symmetrically surrounded, then the should be no change. If you put a load of bricks on one side only, you will have decreased the local gravitational potential so it should slow down compared with the reference clock. Talk to NPL Time Standards Division. They have accessible clocks and can reference them to the NIST transmissions. There are plenty of lead bricks on the NPL campus. It would make a fascinating TV clip - much more audience-accessible than a mossbauer test. In fact it's a pretty slick means of measuring G!
The observer is at both elevations.
I like your slick gravity measurement idea, but wonder if we possess electronics that could measure the ever so slight frequency change such a small amount of gravitational change provided by just bricks alone would effect on the cesium atoms energy transitions.