Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yor_on on 12/04/2010 06:34:12
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The Q. is as above.
Reference Discovery that quasars don't show time dilation mystifies astronomers (http://www.physorg.com/news190027752.html) And an earlier paper from 2001 by Hawkins Time Dilation and Quasar Variability. (http://iopscience.iop.org/1538-4357/553/2/L97/fulltext?ejredirect=migration)
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Could Halton Arp be right after all? That the redshift we measure is a Doppler redshift, not a cosmological one. Here is an original paper by Halton Arp. ATLAS OF PECULIAR GALAXIES. (http://nedwww.ipac.caltech.edu/level5/Arp/paper.pdf)
As well as this paper by M. B. Bell (2004)that seems to support his view that quasars are 'objects' ejected from the galaxies. Distances of Quasars and Quasar-Like Galaxies: Further Evidence that QSOs may be Ejected from Active Galaxies (http://arxiv.org/pdf/astro-ph/0409025v1)
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Or do you have another explanation?
Gravitational lensing?
Micro lensing?
How do they do it.
All of them?
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The problem is more complex than just that the expansion of the universe is wrong. Other observations DO show the expected time dilations. Notably supernova decay curves which are predictable by atomic decay. My guess is that some of the variability is due to "twinkling" caused by microlensing effects. There is an article on this in this week's New Scientist.
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Yes you're perfectly correct SoulSurfer. I got it slightly wrong reading the article in physorg. The idea isn't that the redshift is observed to be the same for all quasars, no matter their relative distance versus our Earth. The redshift 'works' as advertised :), meaning that quasars further away will have an increased redshift due to the universes expansion.
What is wrong with the picture is instead the 'brightness variations' observed. Think of it as lighthouses having a certain periodicity. The further away the slower that periodicity should be seen as happening for us, as the the light traveling towards us get more and more 'stretched' aka redshifted. Well, the quasars don't seem to care about that? They don't change periodicity, no matter their relative distance as observed by the redshift of those waves. and that's even weirder :)
So, how do they do it?
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As for what a quasar is?
"The word 'quasar' is a contraction of 'quasi-stellar radio source'. The first quasars were discovered in the early 1960s, when astronomers measured their very strong radio emissions. Scientists were subsequently surprised to see faint blue star-like points of light, rather than galaxies, when they looked at the same parts of space with optical telescopes. When the quasar's light was analyzed, it was seen that patterns known from laboratory studies of atomic processes were present with very large redshifts (which means the objects are moving away from us at high velocity!).
We now know that, in fact, most quasars are 'radio quiet', i.e., they have very little radio wave emission, but the name quasar has been kept anyway. We also now know that many (perhaps all) quasars are small regions of intense activity within otherwise normal galaxies. What is responsible for all the energy that quasars are seen to be producing - sometimes hundreds of times the energy from normal galaxies? The best explanation seems to be that quasars are super-massive black holes in the centers of galaxies. As material spirals into the black holes, a large part of the mass is converted to energy. It is this energy that we see."
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As for how we measure redshift?
"To determine the redshift, one searches for features in the spectrum such as absorption lines, emission lines, or other variations in light intensity. If found, these features can be compared with known features in the spectrum of various chemical compounds found in experiments where that compound is located on earth. A very common atomic element in space is hydrogen.
The spectrum of originally featureless light shone through hydrogen will show a signature spectrum specific to hydrogen that has features at regular intervals. If restricted to absorption lines it would look similar to the illustration (top right). If the same pattern of intervals is seen in an observed spectrum from a distant source but occurring at shifted wavelengths, it can be identified as hydrogen too. If the same spectral line is identified in both spectra but at different wavelengths then the redshift can be calculated using the table below.
Determining the redshift of an object in this way requires a frequency- or wavelength-range. In order to calculate the redshift one has to know the wavelength of the emitted light in the rest frame of the source, in other words, the wavelength that would be measured by an observer located adjacent to and comoving with the source. Since in astronomical applications this measurement cannot be done directly, because that would require traveling to the distant star of interest, the method using spectral lines described here is used instead. Redshifts cannot be calculated by looking at unidentified features whose rest-frame frequency is unknown, or with a spectrum that is featureless or white noise (random fluctuations in a spectrum)."
So what we do is to look at 'hydrogen signatures' and see where they are placed in those spectral lines to determine the redshift. Which explains how a light wave as seen arriving from a quasar both can have a high periodicity and, yet, still be red shifted.
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So what is microlensing?
As I understands that you then have a VMO like a black hole or a neutronstar, brown dwarf etc, orbiting each one of those quasars, bending and magnifying their light. What I'm unsure on is how those would synchronize their time so perfectly, and also differently, depending on their relative distance versus, just us??? That's even weirder as it then seems as if we were the center for those quasars and their orbiting VMO:s? They are timed against Earth?
Now, that makes me rather nervous :) and slightly religious..
So no, I don't think so myself, it have to be a property of those quasars somehow? First of all, if we have the same behavior for 800 quasars, spread out all over the sky, whatever it is creating it then have to be something related to specifically to quasars, as it seems to me. So it has to do with quasars one way or another. If I use my light house analogy, assuming that they blink once every fourth second and then find that all light houses 'blinked' the same, no matter their distance. Wouldn't that mean that the ones farthest away had to have a faster revolving light, to bring me those flashes in the same relative timespan?
Why would it be so? As I understand it we are said to have had an inflationary period early in our universe that sort of allowed space to expand faster than light? And also we don't know how that BB came to be, it might have been an explosion but if it was it didn't have a defined center as i understands it, so there is a big chance that as it come to be, there was a volume created immediately, and in that case those quasars or their seeds were already widely spread in that volume. If it is so that quasars further away 'blinks' at the same rate as those close to us, could it have something to do with that? How old are they, could they have been there at the very beginning of times arrow? And if so, is it a property of that first creation that makes them behave as they do? are they keeping some sort of cosmic 'time' :)
Wild guesses.
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You are thinking the wrong way.
Firstly microlensing is caused by smallish undetectable point objects within our and other galaxies not anything close to the quasar. It is already known that the light from distant quasars goes through many galaxies on its way to us because of the "Lyman alpha forest"
The variability of quasars is random but has a range of frequencies over which it happens so the variability is a statistical analysis of the variability of light from quasars. Now, if this variability was inherent to the quasars themselves and did not change much with age etc of the quasar, it would be expected that the statistical variability of more remote quasars would tend towards longer periods because of the time dilation effects. This does not appear to occur. If however it was due to the myriad of small undetectable light objects between us and the quasar a bit like the way the atmosphere causes the light from stars to twinkle it is a property of the intervening space.
The way to prove this would be to look at the fine variability statistics of distant supernovae or other distant stellar objets which should show similar fluctuations in their light curves.
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Okay I tried to find it on the net, and this is what I got :)
Definitely the wrong source then? Or I misread it? Galactic microlensing (http://relativity.livingreviews.org/Articles/lrr-1998-12/) It was a new one to me.
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Rereading it I see that they nowhere speaks about orbiting, it was me thinking of binary black holes there. Awh sh*. The danger of jumping to conclusions :)
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Okay a better source for microlensing. Weird, but when I searched on the same subject yesterday I didn't see that one. "Microlensing: where no distortion in shape can be seen but the amount of light received from a background object changes in time. The background source and the lens may be stars in the Milky Way in one typical case, and stars in a remote galaxy and an even more distant quasar in another case."
So it's the time that changes in this case, which makes a he** of a lot more sense to me.
I presume they mean the frequency, and luminosity too?
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Soulsurfer, did you understand exactly how he defined that there was no time dilation? I'm sort of unsure how he did it? No matter what 'blinks' we see we can always count to the two frames involved, right? Ours and the source?
"In order to measure the effects of time dilation, we split the quasar light curves into low- and high-redshift samples. The idea was to compare the resulting SEDs to look for the expected shift of the high-redshift sample towards longer time-scales relative to the low-redshift sample. Fig. 4 shows the low- and high-redshift SEDs separately, and it can be seen that in spite of the restriction in luminosity the SEDs are well defined, with excellent agreement between the different data sets where they overlap. The data are well fitted by the function P(f ) in equation (2), and the fit parameters of interest are given in Table 1. "
I think it goes back to looking for those signatures of redshift and comparing them to the luminosity shown. As I understands it he found a correlation comparing those two sets, our frame, the quasars frame, that pointed to that there was no time dilation shown. But it's a murky read for me, would you know?
And did he mean that they showed the exact same variation, as observed from us, before he corrected the variation periods to their own frame, or after? "But he finds that all the variation periods correlate perfectly if you don't time dilate them, in other words as if we here on earth are seeing them as they are in their own reference frame."
What you seem to be saying is that we expect all quasars to have different variability? And that he have made a statistical analysis of that variability? And from there drawn the conclusion that there is no time dilation shown? Or I am reading you wrong? You're saying that the further away the more time dilation we would expect, and so a longer interval between the 'peaks' of light. Well, okay, that I got actually :) But what methodology did he use to infer it?
As plainly as possible, if you will :)
As this is something I'm totally new to.
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I did not have any problem with the basic statistics of the paper (which is rather old) it was pretty well as I described to you. There are lots of better measurements going on nowadays and with the multi measurement electronic sensor telescopes in use these days vastly increase the data gathering capacity of telescopes for these broad based statistical measurements.
you must remember that astronomy is a very statistical subject and most astronomical conclusions only come from thousands or millions of measurements that are analysed in different ways. Modern computing power also allows old datasets to be re analysed in new ways.
small scale gravitational distortion is starting to become observable the new planet transit discovery telescopes looking at many stars will also detect local microlensing effects which have a different light variation curve. and looking at images with very high resolution the effects of many small objects will start to show up putting limits on what detail can be seen on distant objects but at the same time giving us insight on the material that lies between us and the object.
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You're right, in the 2001 paper he describes it.
"For the study of time dilation, we first make the assumption that the light variations are intrinsic to the quasars, and so the light curves are subject to the effects of time dilation. Thus, for each light curve we rescale the time interval by a factor of (1 + z)-1, where z is the redshift of the quasar, and resample the power spectra on a uniform scale. This should remove the effects of time dilation, with the result that there should be no trend of timescale with redshift. This has the effect of shifting the contributions of all quasars to higher frequencies. It is a big effect, especially for high-redshift quasars, in several cases resulting in low-frequency bins being completely emptied."
The problem was that I never read it :) I got access to the new one and in that one it was a lot murkier :) He* I might even understand this ::))
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It seems that quasars are very hard to generalize. "The best explanation seems to be that quasars are super-massive black holes in the centers of galaxies. As material spirals into the black holes, a large part of the mass is converted to energy. It is this energy that we see."
So depending on what they are feed they will vary their brightness. But it doesn't explain how they can 'seem the same' to us?
Here you can download his new paper.
On time dilation in quasar light curves (http://front.math.ucdavis.edu/1004.1824)
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So let us summarize it.
The redshift is the same as for all other objects out there. The quasars seems to follow the same distance-redshift correlation that we expect from our generalized 'standard candles'. Now there are some discussion about the interpretation of those, but generally they seems to be accepted as giving us a correct definition of distance/redshift. The quasars, also called AGN:s (active galactic nuclei), another irritating abbreviation. It seems astronomy is filled with those kind of 'buzz words', making it quite hard to understand what they refer to at times.
Anyway, those quasars 'evolution' is not following those redshifts though. When measuring the quasars respective light variations over time, and manipulating it through Fourier transformations, the spectrum shown of those light variations should be 'down shifted' to lower frequencies, the further away a quasar is, but that doesn't happen, they all stay the same? And as far as I understand this is before adjusting for time dilation. So when doing that then? What will happen to those light variations then as shown from their own 'frame of reference'? They will have to vary then, right? As we're measuring different distances through the redshift. Now, this all is how I understands it naturally :) And I'm still wondering what it really means :)
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All quasars appear to flicker (that's as good a word as any, though imprecise). If all quasars are pretty much the same in all time periods and if this flickering is something that they do themselves, then there should be the same kind of flickering in all times.
One way of assessing the flickering is to look at the amount of fluctuations at different scales. For example, we measure how different a quasar is every x seconds and use a selection of different values of x to characterize the flickering of that quasar. Now, we make this judgment from our position, so we expect that distant quasars will tend to have the same flickering patterns, but that their flickering patterns will look different to us because x seconds as we see it is really less than x seconds to the quasar. So our profile of quasar flickering near to us should look different from quasar flickering far away.
But it doesn't.
Now it could be that the quasar flickering, or the chunk of it that we're measuring, is not something that happens to the quasar, but it something that happens between us and the quasar (like the way stars twinkle because of the air in our atmosphere). In this case, we should have different expectations about the difference in quasar flickering over distances.
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Yes PhysBang, but as I understand it this 'flickering' is measured before adjusting for time dilation. After adjusting for that, that is, all quasars shown from their own 'frame of reference' their 'flickering's' will differ, if that assumption of mine is correct. That as the redshift seen seems to be correct, and considering that all quasars before this adjustment, if I got it right, all flicker the same according to our observations.
You could say that all quasars 'eat' differently. We can't really say if all quasars accretion disks are the same, can we? It seems very reasonably to assume that they aren't and if that would be then you will have a different 'brightness' to them. And after adjusting for distance and time this is what we will see too, isn't it? That they then 'flickers differently' when seen from their own frame.
The other way to treat it is of course to somehow invalidate the research's methodology and say that it isn't really clear. And to speak about microlensing introduces a he** of a lot of VMO:s (Very Massive Objects) everywhere. I read someone saying that if that was correct, then you don't need any dark matter or dark energy to explain the' missing mass', as those VMO:s will do perfectly well.
And assuming that his methodology is as good as I would expect it to be after so many years, the mystery, if I understand his measuring right, isn't that they 'flicker' the same, because they don't, not from their own frame, only when seen from us without adjusting for their redshift. But I might have got this wrong though? It's a very murky read to us non- astronomers :)
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Yes PhysBang, but as I understand it this 'flickering' is measured before adjusting for time dilation.
That's what I'm saying. All quasars appear to flicker. If they themselves flicker, then we expect to see time dilation. We can only measure the flickering as we see it, not as it is at the source.
After adjusting for that, that is, all quasars shown from their own 'frame of reference' their 'flickering's' will differ, if that assumption of mine is correct. That as the redshift seen seems to be correct, and considering that all quasars before this adjustment, if I got it right, all flicker the same according to our observations.
As it appears now, all flickering looks the same, which means that if it is intrinsic to the quasars, then the kind of flickering that quasars do changes over time in just such a way as to cancel out time dilation. A strange idea.
You could say that all quasars 'eat' differently. We can't really say if all quasars accretion disks are the same, can we? It seems very reasonably to assume that they aren't and if that would be then you will have a different 'brightness' to them. And after adjusting for distance and time this is what we will see too, isn't it? That they then 'flickers differently' when seen from their own frame.
It could be that there is simply different material in the younger universe and this influences how quasars look. But why should this more-or-less exactly cancel out time dilation? It's possible, but odd.
The other way to treat it is of course to somehow invalidate the research's methodology and say that it isn't really clear. And to speak about microlensing introduces a he** of a lot of VMO:s (Very Massive Objects) everywhere. I read someone saying that if that was correct, then you don't need any dark matter or dark energy to explain the' missing mass', as those VMO:s will do perfectly well.
Well, no amount of VMOs will account for the measurements of dark matter from the Bullet Cluster or from the background radiation, but it might be that a reasonable proposal based around VMOs would account for galaxy and galaxy clustering mass. This would be a problem.
And assuming that his methodology is as good as I would expect it to be after so many years, the mystery, if I understand his measuring right, isn't that they 'flicker' the same, because they don't, not from their own frame, only when seen from us without adjusting for their redshift. But I might have got this wrong though? It's a very murky read to us non- astronomers :)
You have it right. The quasars, when averaged out using statistical analysis, all look the same. If there is time dilation, this means that the older, more distant ones look different when one is right next to them.
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It's simply, if I may say so, weird :)
But loveable..
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There is something subtle here that I'm still missing?
There have to be for it to be a question of 'time dilation'.
As I understands it there is not a question of 'time dilation' at all, is there?
They do vary in intensity, as seen from their own frame of reference, but when measured from us all show the same 'clock work' synchronization that seems just implausible if I get it right? To take that as a proof of no time dilation seems quite stupid to me?
What is weird if this is correct is the mechanism behind them giving us the same synchronity, no matter their distances. To explain it with brown dwarfs somehow synchronizing them seems also to crave different magnitudes in mass for those dwarfs, doesn't it?
So we would, by some incredible chance, be situated just at the right distance to all of them, relative the size or/and distance of those brown dwarfs, to see all quasars blink exactly the same? Due to gravitational microlensing?
Well, that do make me religious :)
We are then somehow the 'center' of that phenomena?
It makes, to me, more sense to accept that they do 'blink' differently as seen from their own frames, but possibly also have grown differently depending on distance. What's weird with that idea is that it seems to introduce a Copernican universe where we somehow then would be at some center of creation?
How was it we explained that from everywhere in the universe we would see all other heavenly objects leave us, all running away? A balloon right :) Where we in a 2D-representation would be situated on its very skin, with that same balloon constantly being inflated by expansion?
And that's what we call 'the cosmological redshift', where in fact as seen from 'A' the distance to 'B' can grow 'faster than light'. And the explanation for how that is possible comes down to that all points between galaxies, as I understands it, concentrically grows with more points coming too, so that light from 'B', although moving as fast as allowed in our universe (Speed of light in a vacuum) still can't span the distance constantly created between 'A' and 'B'.
Doppler redshift though will always be seen as being less than the speed of light, as there is no expansion involved in describing it. So, how would Arp describe it? Can Doppler redshift explain why we don't notice any variations, without adjusting for redshift? I don't think so, the difference between Doppler redshift and Cosmological redshift seems to me just to be one of magnitude, isn't it?
Using Doppler redshift only, you will still have the same effect it seems to me, even if by a lesser magnitude? Which makes me suspect that there is something I'm still missing here :)
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This one is still confusing to me. First of all, when they write "The phenomenon of time dilation is a strange yet experimentally confirmed effect of relativity theory. One of its implications is that events occurring in distant parts of the universe should appear to occur more slowly than events located closer to us."
They do not mean time dilations, instead this is referring to a expansion of space. There is nothing in Einsteins Relativity stating that the further away, the 'slower' it goes (as measured by you), as far as I know?
So it begins from a wrongly stated assumption to me. The real assumption here is that a expansion 'fills in' a space, making it look as blinking light signals, with their complementary 'empty stretches' becoming slower, 'stretched out in time' not only red shifted. And that doesn't seem to be the case.
That makes it simpler, if I'm correct here.
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Actually it is a prime example of the idea of a 'container universe', isn't it? A whole common universe, seamless, in where we all exist. What if space, or a vacuum, doesn't exist then? The distortion we see, calling a accelerating expansion, not being any result of a 'medium', called a vacuum, growing. It's very hard to argue that a 'nothing' can increase in magnitude.
The seamless 'common' universe we believe in is observer dependent. And if you use a clock and a ruler (which I'm sure you do) for your experiments, then you need to define how your repeatable experiment can exist in a observer dependent universe. It's not enough stating that 'it works, as proven countless times'.
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Let's use a uniform motion, something 'inertially moving' for that experiment. Does it matter to it if you would accelerate, relative some arbitrarily defined 'fixed stars' to then move uniformly again, repeating the experiment? Why shouldn't it matter?
It will matter for that common 'seamlessly existing' universe you define. But will it matter for your repeatable experiment?
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You contract the seamlessly existing common universe relative that uniform motion, doesn't you? How did you do that?
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It's not about accelerations, it's about the measurements you make, defining existing distances.
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put another way, can you imagine a way in where we find different relative motions to exist, all equivalent when it comes to your repeatable experiment, not being a result of a assumption of something 'containing it'? Try.
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And if I now want to define it from 'energy'. The energy I spent accelerating, would it be equivalent to the energy needed for the mass in a universe 'contracting' its distances, as measured in front of me? Or if you like, how did I contract that vacuum? It can't be, and I doubt the stress energy tensor can explain why uniform motion keep a universe contracted for you after that initial acceleration. What one have to remember is that this also is observer dependent, meaning that most all observers in a universe will find a different distance and time from yours, even though we, for this argument, can assume them all to be in a uniform motion, allowing them to do your repeatable experiment.
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the only way a stress energy tensor can explain it is from an assumption of a container, distorting relative local mass and motion. That also, to me, defines it as a 'absolute motion' as it is able to keep the distortion in a relative motion, expending no further energy locally measured. Unless you find another way to define what this 'container universe' should be seen as. No way around it. And, no, Einstein is correct. I'm using his ideas because he's correct. It's just the implications I wonder about.
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and distortion needs to be taken with a pinch of salt. It's not a distortion according to you measuring, it's your reality.
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So what this thread should be about is not time dilations, but the accelerating expansion we measure. But we find it to exist. http://news.nationalgeographic.com/news/2011/10/111004-nobel-prize-physics-universe-expansion-what-is-dark-energy-science/
and we also have Einsteins 'cosmological constant'
https://duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fjila.colorado.edu%2F~pja%2Fastr3830%2Flecture35.pdf
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Time dilation can be nearly equivalent in different regions of the universe. For instance in galaxies that have nearly identical mass. In the empty space between time will run faster. At the event horizon of a black hole we have a point where time theoretically stops and is the same for every black hole anywhere. It is not the case that the further away you go the dilation changes in only one direction of magnitude. It varies up and down depending upon the proximity of large masses. This is why the quasar data would be puzzling. It shouldn't be the same because the masses near to different quasars will not be equivalent.
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No Jeffrey, not as I read it. I see the opposite, an assumption of a distance (space) between light becoming a time dilation, although it in reality is about a expanding (accelerating) universe. You get a effect in where light signals gets 'spaced out' the further they propagate from some source, but it's not equivalent to what we define as a time dilation. A time dilation, as you say, is about either a mass, or motion. the only way you will be able to argue this as a equivalence to a time dilation is presuming space (a vacuum) to move. Feel free to instruct me how I can prove that one.
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Ah yes :) forgot to say that this is not what we se, apparently. What we see is not what we would expect from a vacuum 'expanding', although we still define some of the redshift we observe to it. the point is though, that if you want to assume a time dilation in this case you will need to construct a logical proof of how a vacuum moves. It doesn't move as far as I can imagine it.
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Think of it as waves, ignore the 'spaces' between signals. They are expected to redshift, do you agree? Would you now define that as light climbing? Out of a gravitational well? What about the redshift we see between two objects leaving each other?
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Another argument is whether you the want to define this expansion to a whole universe, or just the 'empty' parts of it, without matter. To me it's a whole universe that has to 'expand' if so, gravity acting as buoys. It might be possible to argue that 'micro gravity' then either keeps this 'time dilation' inside bounds in rest mass, or that, as the expansion is supposed to be in all points of a universe, it is equivalently 'time dilated'.
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also, it is about what makes a arrow. There I define it as a property. One might argue that it is 'propagating light' that defines it, but I don't think that is solely correct. Propagating light is indeed a clock, observer defined, but it's not the arrow, the arrow is a property existing everywhere to me. I'm questioning the vacuum, still wondering what it is, I'm also questioning our definitions of dimensions, 'preexisting' as some 'container universe'.
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Please don't read this as I think inflation, and a subsequent accelerating expansion is wrong. I think it is a very likely description of our universe. But those arguments above, and more, is what I go out from, trying to guess how it could be. I simplify it by getting rid of the 'container', treating it locally, doing so 'propagation of light in a vacuum' becomes something different to me. The ways to think about it is like mirrors to each other, you can get change without a propagation, and I think you can get a distance defined too. Instead of using the assumptions we built constants from, I prefer to puzzle :) from the assumption of constants being what create a universe, observer dependently.