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Stretched Light

ynot

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If uniformly expanding space stretches light then it should stretch it uniformly (equally in all directions). The overall shape of a uniformly stretched light wave would remain essentially the same but larger. As it wouldn’t actually be stretched as a shape, how can it be redshifted?

ETA - If constantly expanding space stretches light, doesn’t that mean that light constantly gets bigger? :eye-poppi
 
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If uniformly expanding space stretches light then it should stretch it uniformly (equally in all directions). The overall shape of a uniformly stretched light wave would remain essentially the same but larger. As it wouldn’t actually be stretched as a shape, how can it be redshifted?

ETA - If constantly expanding space stretches light, doesn’t that mean that light constantly gets bigger? :eye-poppi

Yes, it gets bigger. If you have a series of light pulses they get stretched apart too.

As the wavelength grows bigger in meters, the frequency of the light becomes less according to the yv = c relation. The falling frequency is an expansion red shift and energy disappears according to the relation E = vh. You get the energy back if you recollapse the space.
 
So “close-up” light can pass through a smaller opening then “far-away” light?
 
No, because everything is expanding at exactly the same rate, in exactly the same proportion.
 
No, because everything is expanding at exactly the same rate, in exactly the same proportion.
By "everything" do you mean that matter is expanding as well as space? Surely if "everything is expanding at exactly the same rate, in exactly the same proportion", then effectively nothing is expanding. Size is just relative isn't it.

If light is being stretched in the direction of its travel, doesn't it mean that it's travelling faster than c?
 
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By "everything" do you mean that matter is expanding as well as space? Surely if "everything is expanding at exactly the same rate, in exactly the same proportion", then effectively nothing is expanding. Size is just relative isn't it.

Matter is NOT expanding at the same rate - that's false. Matter which is bound into a structure, such as a molecule or the earth or even a galaxy, doesn't expand at all. It's only matter which is spread extremely thinly - so thinly that it essentially doesn't interact with anything - which is expanding, and even that kind of matter doesn't redshift at the same rate as light.

If light is being stretched in the direction of its travel, doesn't it mean that it's travelling faster than c?

Yes, in a sense. Light with extremely long wavelength doesn't propagate at all in an expanding universe, and light sufficiently far away from us will never reach us (at least not so long as the expansion of the universe continues to accelerate). However the speed of light as measured locally (meaning that both the wavelength and the distance over which the light travels is small compared to the size of the universe) is always equal to c.
 
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If light is being stretched in the direction of its travel, doesn't it mean that it's travelling faster than c?
No, light is becoming red-shifted because of expanding space. But light always travels at c.
 
No, light is becoming red-shifted because of expanding space. But light always travels at c.

Not really. In an expanding universe it doesn't "travel" at all if its wavelength is too long, essentially for the reason ynot asked about.
 
Matter is NOT expanding at the same rate - that's false. Matter which is bound into a structure, such as a molecule or the earth or even a galaxy, doesn't expand at all. It's only matter which is spread extremely thinly - so thinly that it essentially doesn't interact with anything - which is expanding, and even that kind of matter doesn't redshift at the same rate as light.

This is my poor phrasing that let ynot to this conclusion - my apologies, and thanks for clarifying it. :)

Regarding the speed of light being unvarying... well... it may or may not be true. (more recent info here.) I have no idea if this is still being actively considered, or has been explained away.

excerpt from 2004 article said:
Now, Lamoreaux, along with LANL colleague Justin Torgerson, has re-analysed the Oklo data using what he says are more realistic figures for the energy spectrum of the neutrons present in the reactor. The results have surprised him. Alpha, it seems, has decreased by more than 4.5 parts in 108 since Oklo was live (Physical Review D, vol 69, p121701).

That translates into a very small increase in the speed of light (assuming no change in the other constants that alpha depends on), but Lamoreaux's new analysis is so precise that he can rule out the possibility of zero change in the speed of light. "It's pretty exciting," he says.

So far the re-examination of the Oklo data has not drawn any fire. "The analysis is fine," says Thibault Damour of the Institute of Advanced Scientific Studies (IHES) in Bures-sur-Yvette in France, who co-authored a 1996 Oklo study that found no change in alpha. Peter Moller of LANL, who, along with Japanese researchers, published a paper in 2000 about the Oklo reactor that also found no change in alpha, says that Lamoreaux's assumptions are reasonable.

The analysis might be sound, and the assumptions reasonable, but some physicists are reluctant to accept the conclusions. "I can't see a particular mistake," says Flambaum. "However, the claim is so revolutionary there should be many independent confirmations."

While Flambaum's own team found that alpha was different 12 billion years ago, the new Oklo result claims that alpha was changing as late as two billion years ago. If other methods confirm the Oklo finding, it will leave physicists scrambling for new theories. "It's like opening a gateway," says Dmitry Budker, a colleague of Lamoreaux's at the University of California at Berkeley.
 
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So “close-up” light can pass through a smaller opening then “far-away” light?

Wave length is a factor of vibration , the size of the 'wave' is proportional to the frequency. However the size of the opening would not effect the 'size' of the wave length, the 'length' is the distance from crest to crest of trough to trough. But I could be way wrong.
 
By "everything" do you mean that matter is expanding as well as space? Surely if "everything is expanding at exactly the same rate, in exactly the same proportion", then effectively nothing is expanding. Size is just relative isn't it.

If light is being stretched in the direction of its travel, doesn't it mean that it's travelling faster than c?

Good question, no. The constant c is constant, according to the theory. That is why the wavelength gets shifted. The constant c is subject to HIP (Hiesenberg indeterminancy principle) so it can change relative to very short distances. But it is constant in any frame of reference larger than those where HIP comes in.

So while there may be wierd effects that bother the mind, such as, "Isn't the light from way far away having to travel farther and therefore violating the constant?" the answer is no. I can't explain it yet and will have to think about it.
 
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...the 'length' is the distance from crest to crest or trough to trough. But I could be way wrong.

Nope, that's the wavelength. (with a slight typo correction ;) )
 
Not really. In an expanding universe it doesn't "travel" at all if its wavelength is too long, essentially for the reason ynot asked about.

The only place this happens is near the event horizon around a black hole, or at distances matching the age of the universe, i.e. 13.7 billion ly. Near the event horizon (or any gravity well) time slows down as well so that the constant speed of light remains preserved.
 
The only place this happens is near the event horizon around a black hole, or at distances matching the age of the universe, i.e. 13.7 billion ly. Near the event horizon (or any gravity well) time slows down as well so that the constant speed of light remains preserved.

Which may account for the proposition that black holes, unless created at the time of the big bang, don't exist, but are in the process of coming into existence, the time for which expands without limit as the center is approached.
Also, as one approaches the event horizon, it appears to recede, as one's own time is slowed. Approaching the horizon then becomes an asymptotic process. (Just speculation) :jaw-dropp

The "amplitude" of the light wave - is it a fixed (quantum) dimension?
If it is, that would account for the "aperature" size being not a factor in the question of the light being "near" or "distant." Again, just wondering. :boggled:

Since the "wave-particle" issue is an attempt to force a mathematical concept into a mold shaped by our sensory experience (waves, particles), the metaphors are easily stretched beyond their applicability. :boxedin:
 
Also, as one approaches the event horizon, it appears to recede, as one's own time is slowed. Approaching the horizon then becomes an asymptotic process. (Just speculation) :jaw-dropp

It's only asymptotic when viewed from outside. As experienced from something falling through the event horizon, their own time won't ever feel slowed down, and they will pass through the event horizon plenty quickly in their own reference frame.

The "amplitude" of the light wave - is it a fixed (quantum) dimension?

No, amplitude is not quantized.
 
The only place this happens is near the event horizon around a black hole, or at distances matching the age of the universe, i.e. 13.7 billion ly. Near the event horizon (or any gravity well) time slows down as well so that the constant speed of light remains preserved.

In an expanding universe things are a little different. When the wavelength of light is of order the Hubble length (which is a bit longer than 13.7 Glyrs), the equation of motion is such that the field stops oscillating - in other words there are no longer wave solutions to Maxwell's equations. So there's not really any such thing as light any more, and it can't be said to travel at any particular speed.

And there's not really any slowing down of time due to metric factors - we could imagine attempting to emit light of this wavelength from the earth, for example by VERY slowly moving a charged particle. (What would happen is that the cone of influence of moving the charge would exapnd at c, but the electromagnetic fields inside the cone would not form waves.)
 
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