#366 Gravitational redshift from a falling or stationary source
Suppose we have a source that is falling towards a large mass. Suppose that it passes a second source that is being held stationary relative to that mass. Suppose they both send light signals to an observer that is farther away from the mass. Does the observer see the same redshift from each source or does the falling source show an extra redshift?
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If it is falling ‘away’ from the measuring point, and the measuring point is stationary relative to the large mass, then the sources have:
Edit: the measuring point does not need to be relatively stationary - the falling mass will have an extra redshift regardless
Thanks, @Francois-Zinserling . I realize that makes common sense. If it weren’t true, then you would not know whether a distant star was redshifted because it was falling or because it was in a gravitational well. And yet they are more or less the same thing. It feels wrong somehow. I wonder if there is astrophysical evidence for what you say. The laboratory gravitational shifts may be too small.
Gravitational redshift at e.g. earth is very small compared to its velocity counterpart. It would take a large mass to be comparatively redshifted.
Why are you asking? Are you cooking up something? 😁
You know it! It’s related to my shell black hole universe model, which I know you’re not too fond of. I argued before that 95% of the black hole universe’s mass is in a thick outer shell and that the Newtonian and GR shell theorems don’t apply (due to some relativity solutions by Jun Ni and others). This gave rise to a gravity gradient pointing towards the shell. This could explain the cosmic redshift, the time dilation in supernovae and the CMB temperature gradient, but there are some big problems. Galaxies closer to the centre of the shell than us should look blueshifted rather than redshifted. We don’t see those (but recently I found out there could be very few such galaxies). As well, if more distant galaxies are deeper in the gravity well of the shell than us, they should be falling faster towards it. There velocities would eventually be huge. I don’t think they are falling like that, but it would help the blueshift problem if they were! But then again, there would be the gravitational redshift from them also, since they would be closer to the shell than us. So we would be seeing a gravitational redshift PLUS a Doppler redshift, according to your interpretation. That would mean a composite redshift which would mess up everything. You asked!
I am actually quite fond of your black hole universe and it somewhat aligns with my pushgravity findings. Except I interpret it different (without messing up your maths, I think) and which might yet solve some of your paradoxes.
Some of the problems I would have with your interpretation are:
Here goes: You know when you are hypothetically looking at a black hole, something appears more redshifted as they approach the Sz radius, and eventually become invisible as it enters ‘below the line’. So the Newton and GR theories say anyway and it makes good sense to me.
Now from my interpretation we are not ‘inside’ a black hole, but when we look toward the horizon of our cosmos we see the (inner) surface of our ‘shell’ exactly as we would see the black hole (outer) surface - severely redshifted. A bit further and we see ‘nothing’. You may need to bend your mind a little to flip the black hole inside-out - so everywhere we look at the edge of our view looks like the surface of a black hole. We are not in it but it is outside our entire view. I hope this makes sense.
It is simply explained that the equivalent of your thick shell is ‘all the mass’ beyond the visible horizon. To infinity and beyond!
Then it is not the shell but all the mass within the ‘shell’ that weakens the remote ZPF pointed directly at us, crudely via gravity of each object along (but not directly in line of) the light path. This is why we see the remote light as weakened. The gravity of the ‘shell’ is neutralised because we are in the centre of this homogenous and isotropic shell so we are not sucked outward. A simple Newtonian solution proves this. Anyone elsewhere in the cosmos has his own distant shell and is thus in the centre of ‘his own universe’
Thanks! Well there are indeed some similarities in how we are seeing these things. The way you describe the cosmos is very much like how I would have described just a few years ago. Several things led me to think we are at the centre of a real shell black hole, not one whose ‘shell’ varies in position depending on the observer’s point-of-view. These are chiefly the Hubble luminosity of the shell BHU, which keeps the shell inflated against the gravitational collapse. Its power is c^5/4G. In a recent thread this was termed the ‘Planck power’, but my derivation of it has more to it. Secondly, the temperature gradient of the CMB (which most of ACG do not accept) is consistent with what would be found if the radiation trapped inside the shell universe during its formation were thermalized to CMB over billions of years - it would naturally track the gravity gradient of the shell. The CMB redshift can then be linked to gravity.
On your specific points: (1) it does seem odd that we could be so close to the centre of this thing, but consider this. If the interior of the shell universe does have a void at the centre, as we would expect if the GR solutions were like what Ni and Neslusan suggested; and given that the KBC Void is by far the largest of the known voids (maybe 7 times larger); and that the KBC Void is thus the most likely candidate void to lie at the centre of the BHU; and given that the centre of the KBC Void would thus likely lie at the centre of the BHU; and noting that the Milky Way is close to the centre of the KBC Void, maybe 100 Mpc from the centre - then that places us extremely close to the centre! What’s more, the density of the KBC Void seems to get less as you go to its centre. There could be very few galaxies between us and the centre.
On the black holes, I’m prepared to make a substantial bet - say, the whole city of Toronto - that they are mechanistically identical to how the black hole universe operates. Their characteristic ‘CMB’ is just much hotter, due to their higher Hubble luminosities.
On what the JWST sees, it is probably seeing galaxies already within the shell, though still inside the Schwarzschild radius. It’s likely a very thick shell, maybe 10-20% of the BHU radius. Maybe calling it a shell is misleading - more of a thick cloud. The Little Red Dots are probably the central black holes of galaxies forming, with no stars yet. But this is a continuous process, not a ‘one off’, like the LCDM supposes.
Your description of the redshift is actually very close to what I would say and also close to what Zwicky initially proposed. The trouble I am having is if I take the Hubble redshift to be that sort of thing, then how can it also be due to the gravity gradient with the shell. Unless they are both the same thing - the gravitational redshift, relativistic light deflection, Hubble redshift and gravity are all the same thing.
Then you went to the dark side! …. Just kidding.
Why not 2 or 3 BHU radii? From here it will still appear to be a solid shell. Like the opposite of Olber’s paradox. But then I don’t understand why you don’t agree that ‘everywhere’ will have its own thick shell and the physics there will look just like here.
Sadly, I don’t share your conviction. This is just too weird to wrap my mind around. And this, coming from me, the pushgravity peddler. :)
The Newtonian solution I know for the interior of a solid thick shell says there is 0 gravity everywhere within. I do not know how this will cope with GR, e.g. lightspeed gravity in a cosmic sized shell. I guess depending on how the shell forms or how large or old it is, but you could be stuck to the inside of a thick or solid shell until the gravity from the far side reaches you. Odd way of thinking about it. Don’t know why I’m mentioning it.
The Zwicky proposal (and mine) would have a problem if light and gravity from the remote cosmos weakens over the distance. Imagine for a moment Fatio and Le Sage’s corpuscles. Not saying this is a solution but it is a vivid picture I think we both understand. One of the main problems of Le Sage is that the gravity must then weaken over distances because the corpuscles are depleted. What we ‘see’ in the redshifted light of the CMB is indeed the weakened light from there, gradually weakened just like Fatio’s corpuscles. Even though the light source has a clear path, it will be weakened. TL for sure. If we could somehow measure the gravity from the CMB, it will be equally weakened.
To not suffer from ‘corpuscle depletion’, there must thus be nearby replenishers. Push-gravity is hard enough to sell. Now this too :)
Another point favouring the shell black hole universe that I forgot to mention is that it solves several problems in cosmology. The missing mass in the LCDM model is not dark matter or dark energy. It’s just ordinary baryonic matter. We can’t easily see the 95% contribution of the shell but the JWST observations are starting to show it - accounts of higher densities, more gas, etc. As well, if you calculate the gravitational gradient produced by the shell, supposing that attenuation wrecks Newton’s shell theorem (and the GR equivalent), you will see it can produce accelerations very close to the MOND acceleration.
The leap to shell black holes will be very easy for you, if you can accept the shell BHU !
You are right about attenuation of Le Sage particles (or waves) would deplete the gravitational stock, but I already have that covered. The gravitational blueshift of waves as they head back to the shell regenerates the particle and CMB energies in the shell, to begin a new round. Basically, I suggest that CMB energy drives gravity, associated with the cosmic redshift, and that the Hubble luminosity eventually reverses gravity, this being associated with the cosmic blueshift. There are still many dots to connect here.
Getting back to the initial query, it seems to me that if one takes a Newtonian perspective, then the gravitational redshift and the Doppler shift from a falling body could add up. But in general relativity, there is this idea that spacetime is moving. If a photon is emitted in this moving river of spacetime, it doesn’t seem to matter whether or not it’s being emitted from an object already flowing in this river. It actually needs an experimental or observational verification, one way or the other. Know of one?