[timey]

Happy to have alerted you to the continued presence of the website.  I simply copied and pasted your description and it was the first item.

[PmbPhy]

Happy to have alerted you to the continued presence of the website.  I simply copied and pasted your description and it was the first item.

Thanks.

I deleted the rest of your post because being a moderator means enforcing the forum rules and your response violated those rules. You cannot simply place judgment calls on someone like that, i.e. assume they meant something when there's nothing in their response to indicate it. I certainly never mean what you always assume I mean. And when you make such claims its quite rude and therefore violates forum rules.

That doesn't mean that you can't tell someone what you think. That's what a PM is for. You do not chew someone out in the forum like you have a tendency to do. Especially being as wrong as often as you are. And I know because I am the worlds leading authority on what I think and why I say what I do and I can tell you as a fact that in all cases you have been wrong.

I'm stating this in open forum so that everyone one here knows that it's wrong to make assumptions about peoples motives. If you think they meant something then simply ask them. Do not accuse them. Do so in PM if you must. I will delete all such accusations when I see them. Accuse people on your own time and in private. It has nothing to do with the subject at hand

[PmbPhy]

I deleted your post again for the same reason - airing your personal gripes in open forum. Don't do it again.

[alancalverd]

In response to timey

GR, like SR, is a mathematical model based on the idea that observation equals reality.

You would do well to review your understanding of atomic clocks, but the mechanism of the clock is irrelevant if you use the GR approach.

At present we do not have much of an idea as to how gravity works, because we have not identified a long-range mass-dependent attractant carrier.

I gather there is some background spat between timey and PmbPhy and I've been asked to intervene, but in the absence of the evidence all I can say is that I am delighted to have made two such robustly and eloquently outspoken friends through this forum, and I hope you will both adopt a similar attitude. But then I was brought up on a diet of Kipling:

Oh, East is East, and West is West, and never the twain shall meet,
Till Earth and Sky stand presently at God's great Judgment Seat;
But there is neither East nor West, Border, nor Breed, nor Birth,
When two strong men stand face to face though they come from the ends of the earth!

[timey]

Did you read the link Alan?

http://www.geocities.ws/physics_world/gr/grav_red_shift.htm

Whether posted by purposeful design, or coincidence, this link echoes that which I was outlining to you in post 31 and 32.

You would do well to review your understanding of atomic clocks, but the mechanism of the clock is irrelevant if you use the GR approach.

Could you please outline what your contention is with my understanding of atomic clocks?
I understand, to describe in the most basic terms, that a microwave beam resonating at a certain frequency causes electron transitions in atoms.  When viewed in a potential differing from that of the observer, this resonating frequency causing electron transitions is observed to differ.  The amount by which the frequency differs is predicted by GR, therefore the clock not only appears to be ticking faster in the higher potential 'from' a lower potential, it IS actually ticking faster.

[alancalverd]

Good reference. Note in particular

What’s wrong with Schild’s argument? First one needs to be careful when interpreting the statement "The frequency of light decreases..." Caution must be exercised when using "the" when discussing relativity. The frequency reckoned but which observer?

which is why I always stick to the pedantic statement "....when observed by an observer at the lower gravitational  potential..."

Electron transitions, and more importantly in the case of atomic clocks, hyperfine spin-spin transitions, are associated with the absorption or emission of photons, from x-rays through the visible spectrum and down to microwaves. However you observe the characteristic photon of an atomic clock, it appears to have a higher energy if the clock is at a higher gravitational potential than the observer. Why "appears to"? (a) because that's a statement of experimental observation and (b)  the electron spin vector is only quantised by interacting with the magnetic moment of the nucleus , which  isn't changed by gravitation. If it was, then the bandwidth as well as the observed centre frequency would change with gravitational potential.

For the benefit of anyone who hasn't seen this before: three blokes on a train in Patagonia saw a black cow and a white cow in a field. The statistician said "half the cows in Patagonia are black". The mathematician said "There is at least one  black cow in Patagonia" and the physicist said "I see two bovine quadrupeds, at least one side of one of which is black".

[DudleyC]

I dont quite think so. Maybe our technology cannot support to make the frequency as low or as high as what we want it to be.

[Colin2B]

........the electron spin vector is only quantised by interacting with the magnetic moment of the nucleus , which  isn't changed by gravitation. If it was, then the bandwidth as well as the observed centre frequency would change with gravitational potential.

The point Alan makes here is an important one.
Consider also the transitions themselves. If we have 2 observers in different gravitational potentials and midway between the 2 we set off a flash of light to indicate start of counting the transitions, and a second flash to indicate stop counting, both observers will count the same number of transitions. However, start and stop are simultaneous events for both observers so the nature of the transitions has not changed, only the time over which each observer measures the transitions and hence calculates the frequency. So it is the difference in time which is the issue, not a fundamental change in the transitions. As Alan points out, using the to describe a frequency needs to be done with caution and it is far better to describe what is measured by each observer.

[timey]

What I think it is important to realise is that any photon that is emitted by the clock in the higher potential has been blueshifted by the time it is observed in the lower potential.  If you minus the magnitude of the blueshift then the clock isn't ticking faster.  General relativity states that the clock is indeed ticking faster.  This is where G.E. Marsh and C. Nissim-Sabat make their argument in response to Schild.

Electron transitions, and more importantly in the case of atomic clocks, hyperfine spin-spin transitions, are associated with the absorption or emission of photons, from x-rays through the visible spectrum and down to microwaves. However you observe the characteristic photon of an atomic clock, it appears to have a higher energy if the clock is at a higher gravitational potential than the observer. Why "appears to"? (a) because that's a statement of experimental observation and (b)  the electron spin vector is only quantised by interacting with the magnetic moment of the nucleus , which  isn't changed by gravitation. If it was, then the bandwidth as well as the observed centre frequency would change with gravitational potential.

Please note (and believe me I am literally crawling at snails pace through the maths in the link), that it is indeed a gravity potential consideration that is being added.

On the basis that General Relativity and Quantum are incompatible, this is of interest to me.  Any comment?

[jeffreyH]

Maybe it'll eventually click, maybe it won't...

[timey]

Maybe it'll eventually click, maybe it won't...

If you are indeed responding to my post, and not someone else's...

Maybe what will eventually click Jeff?

[evan_au]

Which choice of reference frame would result in equating a wavelength the size of the universe?

EM waves have the problem that the universe has at certain times been opaque to them, which effectively prevents them from being the width of the universe.

But if we move away from just EM waves, some researchers are searching for gravitational waves that were once almost the size of the universe. It is thought that quantum fluctuations in the early universe (microseconds after the Big Bang) would have produced gravitational waves. Because the universe would have become transparent to gravitational waves in this early epoch of the universe, they might be detectable now (with the right detectors).

Some teams are trying to build detectors that would pick up relic gravitational waves that have frequencies as high as 10¹¹ Hz (compared to the 50-1000Hz detectable by LIGO).

But the theory of cosmic inflation suggests that the very early universe expanded faster than the speed of light for a short time, and so since that time, no waves could be formed that are the width of the universe.

See: https://en.wikipedia.org/wiki/Inflation_(cosmology)

[jeffreyH]

Maybe it'll eventually click, maybe it won't...

If you are indeed responding to my post, and not someone else's...

Maybe what will eventually click Jeff?

I was replying to Colin.

[timey]

Which choice of reference frame would result in equating a wavelength the size of the universe?

EM waves have the problem that the universe has at certain times been opaque to them, which effectively prevents them from being the width of the universe.

But if we move away from just EM waves, some researchers are searching for gravitational waves that were once almost the size of the universe. It is thought that quantum fluctuations in the early universe (microseconds after the Big Bang) would have produced gravitational waves. Because the universe would have become transparent to gravitational waves in this early epoch of the universe, they might be detectable now (with the right detectors).

Some teams are trying to build detectors that would pick up relic gravitational waves that have frequencies as high as 10¹¹ Hz (compared to the 50-1000Hz detectable by LIGO).

But the theory of cosmic inflation suggests that the very early universe expanded faster than the speed of light for a short time, and so since that time, no waves could be formed that are the width of the universe.

See: https://en.wikipedia.org/wiki/Inflation_(cosmology)

http://news.stanford.edu/news/2014/march/physics-cosmic-inflation-031714.html

https://www.newscientist.com/article/dn25293-space-time-ripples-hint-at-physics-beyond-the-big-bang/

https://www.newscientist.com/article/mg23230970-700-cosmic-coincidences-everything-points-in-one-direction/

Here are some more detailed links about the cosmic microwave background and gravitational waves.

This is what Lee Smolin said in his book "The Trouble With Physics" written in 2006:

:Lee Smolin
An oscillation at a wavelength of the scale R takes up a huge part of the sky - about 60 degrees; consequently we see only a few wavelengths, and there are only a few pieces of data, so what we are seeing may just be a random statistical fluctuation.  The chances of the evidence for a preferred direction being a statistical anomaly have been estimated at less than 1 part in 1000.  But is may be easier to believe in this unlikely bad luck than to believe that the predictions of inflation are breaking down.

But the point that I am trying to make here is that the 'length' of a wave-period is reliant upon which rate of time one measures the wavelength from.  The choice of reference frame one measures from affects the measurement.
For instance - if we (hypothetically) measure a wavelength from a reference frame where a clock is ticking really fast, the wavelength will 'appear' longer than if you measure it from a reference frame where a clock is ticking really slow.
Then it becomes very pertinent indeed to consider the fact that the measurement of 'lights' wavelength can only be measured as it is 'in' the reference frame that the observer is observing from, and that any wavelength observed is shifted by the gravitational field it travels through before it reaches the observers frame.  Where it is important to note the fact that a clock's wavelength is observed 'from' the lower potential to decrease when the clock is placed in a higher gravity potential, as compared to the clock that is observed in the lower potential, that GR predicts that this time dilation is a physical reality, and most importantly that light shifting from the lower potential into the higher potential will be observed 'in' the higher potential, measured via the faster ticking higher potential clock, to be of a longer wavelength compared to when it was measured in the lower potential via the slower ticking clock.

[guest4091]

Doppler shift: the origin or base frequency (determined by design and settings of emitter) remains constant, but perceived frequency varies with motion of emitter or detector or both.
Measure the freq approaching as f1. Measure the freq receding as f2.
Base freq f=sqrt(f1*f2).
In a g-field, observing a static clock A results in a perceived doppler shift depending on
observer position relative to A. Moving A to a different position changes it's base frequency.

A clock is a frequency so why should there be any difference from photon to clock?
Light loses energy in leaving the surface of a mass. A clock runs slower on the surface than above it, so what's the difference?
And then there's the light clock! (it’s a clock and it’s light)

What do you think?

[PmbPhy]

Doppler shift: the origin or base frequency (determined by design and settings of emitter) remains constant, but perceived frequency varies with motion of emitter or detector or both.

I'd like to make one point clear here in case someone takes your comment as meaning that there's some sort of optical illusion going on here.

I'm going to point out that there's nothing "perceived" about the frequency of light. The frequency of light is completely undetermined by its origin and only determined by the frame of reference in which its measured. Its almost impossible (or perhaps it really is as yet impossible) to speak of the emitter of the photons which constitute the 3K microwave background radiation.

A clock is a frequency so why should there be any difference from photon to clock?

Because a clock is not a frequency. It merely ticks at a certain frequency. The rate at which a clock ticks is merely one property of a clock. Also there are frames of reference in which a clock is at rest but there are no frames of reference in which a photon can be at rest. A clock has rest mass, a photon doesn't. A clock has a temperature, a photon doesn't. etc.

Light loses energy in leaving the surface of a mass.

That's a common misconception. As reckoned by any observer at rest relative to the source of the gravitational field, the energy of a photon is constant as if moves through field as its is frequency. Only the locally measured energy and frequency are different.

[timey]

Doppler shift: the origin or base frequency (determined by design and settings of emitter) remains constant, but perceived frequency varies with motion of emitter or detector or both.
Measure the freq approaching as f1. Measure the freq receding as f2.
Base freq f=sqrt(f1*f2).
In a g-field, observing a static clock A results in a perceived doppler shift depending on
observer position relative to A. Moving A to a different position changes it's base frequency.

A clock is a frequency so why should there be any difference from photon to clock?
Light loses energy in leaving the surface of a mass. A clock runs slower on the surface than above it, so what's the difference?
And then there's the light clock! (it’s a clock and it’s light)

What do you think?

Alrighty phyti... I am really appreciating your post.

A clock is a frequency so why should there be any difference from photon to clock?
Light loses energy in leaving the surface of a mass. A clock runs slower on the surface than above it, so what's the difference?

According to Marsh and Nissim-Sabat (as far as I can make out from the maths) the clock (in the higher potential) is considered to have additional gravity potential energy (still waiting for an authority on maths to confirm this for me)

http://www.geocities.ws/physics_world/gr/grav_red_shift.htm

And this brings us back to Alan's consideration

:Alan, post 45
Electron transitions, and more importantly in the case of atomic clocks, hyperfine spin-spin transitions, are associated with the absorption or emission of photons, from x-rays through the visible spectrum and down to microwaves. However you observe the characteristic photon of an atomic clock, it appears to have a higher energy if the clock is at a higher gravitational potential than the observer. Why "appears to"? (a) because that's a statement of experimental observation and (b)  the electron spin vector is only quantised by interacting with the magnetic moment of the nucleus , which  isn't changed by gravitation. If it was, then the bandwidth as well as the observed centre frequency would change with gravitational potential.

On the basis that General Relativity and Quantum are not compatible theories, can anyone else see why this may be interesting?

What do you think?

I think the same thing that every physicist I've read concludes, this being that there is something about the nature of 'time' that physics is missing.

[evan_au]

Which choice of reference frame would result in equating a wavelength the size of the universe?

The assumption here is that in selecting a frame of reference relative to the photon, it does not affect the size of the universe.

No-one is quite sure how you would unambiguously determine the boundaries of the universe (or even if it has any boundaries), but...
- if you select a hypothetical photon that is emitted at the source with a wavelength of 4.1 billion light-years (30% of the width of the observable universe = 13.8 billion light-years)
- then accelerate away from the source such that the wavelength of the photon is now 13.8 billion light-years (nominally the width of the observable universe)
- then you would find that in your new frame of reference, the width of the universe is no longer 13.8 billion light years, but something different
- and,what's more, the width is different looking forwards/backwards or sideways/up/down!

The other way of fiddling with time is to use gravitational wells:
- If you put the source of photons with 4.1 billion light-year wavelength in a deep gravitational well, the photons will lose energy climbing out of the well, and it is true that they may well end up with a wavelength of 13.8 billion light-years.

Speculation: If the universe has no specific boundary, it is possible that photons of this wavelength will interfere destructively with themselves if the size of the universe is not an integral number of wavelengths. So perhaps wavelengths might be quantised on very large scales (but they would take longer than the current age of the universe to interfere with themselves, and by then the size of the universe would have changed....)

[timey]

Which choice of reference frame would result in equating a wavelength the size of the universe?

The assumption here is that in selecting a frame of reference relative to the photon, it does not affect the size of the universe.

Ok - well working from an assumption that there is only one universe, as opposed to a multiverse, if the universe started off as a point then the space that the universe is expanding into is being created as per the expansion.  Therefore the size of the universe is related to it's age.  But as we are calculating the age of the visible universe by the remit of observation of wavelengths, wavelengths that we are measuring via the tick rate of a clock, then both the waves that we are observing to make this assessment and the clock we are measuring the period of the waves via are subject to different measurements dependent on which choice of reference frame.
From our reference frame, here on earth, the age of the universe will 'perhaps' differ from a measurement taken elsewhere in the universe.

This is why (I think at least) that it is important to consider the fact that light and a clock are shifting frequency in opposing directions in the gravity field, i.e. the clock according to GR is increasing in frequency in the higher gravity potential, and the light according to GR is decreasing in frequency in the higher gravity potential.  And that for the light to be measured 'in' the higher potential via the 'faster' ticking clock as decreased in frequency compared to how it was previously measured 'in' the lower potential measured via the 'slower' ticking clock is highly pertinent.  Highly pertinent because the clock is telling us that time is running faster 'at' altitude, therefore the light must also be affected by this faster rate of time where it's frequency 'should' increase as the clock's has, but the light is measured by the faster ticking clock as being a lower frequency.  By remit of logic the light is decreased in frequency by twice the magnitude that the clock is increased in frequency.

This train of thought was outlined by Marsh and Nissim-Sabat in the link that Pete posted.

The fact that it is the gravity field that is causing these frequency changes is then pertinent to the measurement of the exact age of the universe.
However, I have noticed that gravity field assessment becomes fuzzy in the face of the necessity for Dark Matter to describe the observed motion of galaxies...

[guest4091]

Timey;

the clock according to GR is increasing in frequency in the higher gravity potential, and the light according to GR is decreasing in frequency in the higher gravity potential.

If the clock is a light clock, this looks like a contradiction.
GR requires so much math just to get nano sec results! That must be why it has little interest for me. It won't change Dominoes's slogan to "we deliver within 30 ns of expected delivery time".