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Tired light 
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#1
Feb411, 05:47 AM

PF Gold
P: 1,376

I read this in article "Misconceptions about the big bang" that was mentioned in another thread:
"For example, when a star explodes as a supernova, it brightens and then dims — a process that takes about two weeks for the type of supernova that astronomers have been using to map out space. During these two weeks, the supernova emits a train of photons. The tiredlight hypothesis predicts that these photons lose energy as they propagate but that the observer always sees a train that lasts two weeks." This article can be found here as well. I have some doubts about such a simple prediction for tired light. From quantum mechanics we know that photons are not like billiard balls. They have phase and as a result interference effects can take place. Now if we increase wavelength and therefore decrease frequency phase differences inside photon train will change. As a result there should appear some interference effects that will change photon train on the whole not only individual photons. Any comments? 


#2
Feb411, 12:23 PM

P: 728

We can change the velocity of light with refraction, it slows down and we can separate frequencies because different frequencies bend at different rates. Also we can slow the light down for example in a coax cable ~0.7c. However, I cant think of many other ways of changing the frequency other than doppler.
Fluorescence is one: http://en.wikipedia.org/wiki/Fluorescence Here's a list of ...esenses http://en.wikipedia.org/wiki/Luminescence Are you trying to find alternative explantions for red shift? and thus the rate of expansion of the observable universe? I doubt any of the above could produce black body radiation of the correct frequency. 


#3
Feb411, 04:03 PM

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PF Gold
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#4
Feb511, 12:50 AM

PF Gold
P: 1,376

Tired light



#5
Feb511, 01:13 AM

PF Gold
P: 1,376

But I think that ensemble interpretation is more downtoearth than any other interpretation. And from perspective of this interpretation "photon trains" or photon ensembles are necessary to explain quantum effects and resolve quantum paradoxes. 


#6
Feb511, 01:50 AM

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Anyway, we know that this sort of thing doesn't happen anyway, because very distance supernovae are too bright to be explained by tired light. 


#7
Feb511, 11:25 AM

PF Gold
P: 1,376

Anyways I am not sure that expanding universe can really help here. You see, if gravity and expansion are two opposite things then gravity is contraction of spacetime and the net effect of the two would be static universe. That thing about gravity is quite obvious if you consider how effects of black hole are described i.e. space like time inside event horizon. 


#8
Feb511, 12:34 PM

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#9
Feb511, 12:49 PM

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#10
Feb711, 07:25 AM

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#11
Feb711, 07:38 AM

PF Gold
P: 1,376

Assuming the opposite it is quite likely to occur. The question can be only about expansion (accelerated, decelerated or what ever) versus static universe of tired light model. And in that case distant light sources are too dim to be explained by naive version of tired light. 


#12
Feb711, 08:04 AM

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Now, it is very possible for a significant amount of interaction to occur within the host galaxy of whatever emitted the light (some are so dusty that hardly any visible light gets through). But once the photons reach interstellar space, there is almost no further interaction. But when we look far enough into the past, we actually see an apparent brightening of supernovae, which completely solidifies this as being impossible. I'd also like to point out that supernovae are only the first experimental evidence of the acceleration. Today we have many more pieces of evidence, and they all fit a LambdaCDM model of the universe. 


#13
Feb711, 09:01 AM

PF Gold
P: 1,376

Maybe you can give the source of your statement? "The time evolution of the cosmic scale factor depends on the composition of massenergy in the Universe. While the Universe is known to contain a significant amount of ordinary matter, [tex]\Omega _{M}[/tex], which decelerates the expansion, its dynamics may also be significantly affected by more exotic forms of energy. Preeminent among these is a possible energy of the vacuum ([tex]\Omega _{\Lambda}[/tex]), Einstein’s “cosmological constant,” whose negative pressure would do work to accelerate the expansion (Carroll, Press, & Turner 1992; Schmidt et al. 1998). Measurements of the redshift and apparent brightness of SN Ia of known intrinsic brightness can constrain these cosmological parameters." Does not sound like confirmation of some prediction. It sounds exactly like results are used to do some fitting of parameter(s). 


#14
Feb711, 10:18 AM

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http://lambda.gsfc.nasa.gov/product/...gy_reprint.pdf The parameter of interest is [itex]\tau[/itex] (the Greek letter tau), which is the optical distance to the surface of last scattering, which is constrained to be around 0.085, plus or minus about 0.015. This parameter is such that the amount of light we see is [itex]e^{\tau}[/itex] times the light that was emitted. For example, see here: http://hera.ph1.unikoeln.de/~heintzma/Sp_Art2/S406.htm Note that the different experiments all converge on the same values for these parameters. Granted, the supernova estimate is biased a bit towards the upper right, but this is likely due to a failure to take into account the effect of gravitational lensing on the supernova signals. 


#15
Feb711, 10:41 PM

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#16
Feb811, 11:38 AM

P: 728

Since we were also earlier talking about dark energy cosmology and LambdaCDM, I wanted to clarify the following:
Do we know, or is it perhaps assumed, that the effect of dark energy on space at any given moment of time is equal and homogenious throughout the whole universe? Or do we see variation in the magnitude of the effect of dark energy both at different distances and directions, as well as at different points in time? 


#17
Feb811, 03:11 PM

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#18
Feb911, 03:08 AM

PF Gold
P: 1,376

If you would be then you would find out my level in physics and math along the way. Instead you are offering to find me some reading. Well, I am not asking that. Why should I bother answering you? So maybe you can try to tell me what I "clearly don't understand" and I will tell you if I understand what I "don't understand". 


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