A question about expansion

[trumptor]

I was wondering about our knowledge about light waves. How do we know that light waves don't degenerate and lose their frequencies with distance? I don't mean in an easily measurable distance. I mean over great distances like between galaxies.<br /><br />Could the perceived red-shifting due to expansion be accounted for in this way and that we are really in a static universe? I would like to know why or why not if somebody would help me out. <div class="Discussion_UserSignature"> <p><em><font color="#0000ff">______________</font></em></p><p><em><font color="#0000ff">Caution, I may not know what I'm talking about.</font></em></p> </div>

 

[dragon04]

If how we determine red-shift is correct, then a photon doesn't or can't "attenuate" over even distances of billions of light years.<br /><br />Also, we determine that red-shift in varying ways over varying distances, so it appears that a photon itself is a constant as opposed to a variable. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[michaelmozina]

<blockquote><font class="small">In reply to:</font><hr /><p>I was wondering about our knowledge about light waves. How do we know that light waves don't degenerate and lose their frequencies with distance? I don't mean in an easily measurable distance. I mean over great distances like between galaxies.<p><hr /></p></p></blockquote><br /><br />We definitely aren't 100% sure of why light from distant objects is redshifted. You might look up the term "tired light theories". There have been many tired light theories proposed over the years. IMO, the most interesting newer variations of tired light theories (in terms of math) have been put forth by Ari Brynjolfsson.<br /><br />http://arxiv.org/find/all/1/all:+Brynjolfsson/0/1/0/all/0/1<br /><br />The general theme of these tired light propositions is that redshifting is a result of the photon's interactions with plasma along the way. <br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>Could the perceived red-shifting due to expansion be accounted for in this way and that we are really in a static universe? <p><hr /></p></p></blockquote><br /><br />Yes, that's certainly *one possible* and valid scientific way to interpret redshifted photons, but it's a far "less popular" interpretation. You might also want to checkout the work of Halton Arp.<br /><br />http://en.wikipedia.org/wiki/Halton_Arp<br />http://www.electric-cosmos.org/arp.htm<br /><br />Arp has shown that there are a number of physically connected galaxies that have very different redshifts. <br /><br />You might also want to checkout MECO theory. It's a GR based theory that suggests that very heavy objects (like neutron stars) can have an internalized redshift component.<br /><br />The arguments and battles between static universe theory and expansion theory h <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[origin]

<font color="yellow">We definitely aren't 100% sure</font><br /><br />Here he goes again... We are also not <b>100% sure</b> that the center of the moon isn't filled with cream cheese however, we are sure enough that it is not necessary to research the matter.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[porkchopsnapplesauce]

Hi All,<br /><br />I am new here and had a question about expansion that I never really understood. <br /><br />The question is how do we know the Universe is expanding at a faster rate then it was in the past? The part I don't understand is related to the redshift. Wouldn't the galaxy's closer to us have the larger red shift then those further away if the Universe was expanding faster now then before? My understanding was that this is the opposite of what we are seeing, and those with the largest redshift are also those that are the furthest away (hence oldest).<br /><br />I know I am mixing something up, just not sure what.<br /><br />Thanks

 

[SpeedFreek]

I made the same false assumption as you have, when I started trying to understand all this stuff.<br /><br />The first thing to consider is that cosmological redshift, the stretching of light due to the expansion of space, is a <i>cumulative</i> effect. All the time that light is passing through space that is expanding, that light is being stretched.<br /><br />If the rate of expansion had always been constant, we would see that the further an object is from us, the higher its redshift would be, and the relationship between redshift and distance would be linear.<br /><br />But the rate of expansion has not been constant. In the distant past, just after the big-bang, the rate of expansion was immense! After galaxies formed, points in space that were closer than 1 billion light years apart from each other were receding from each other at the speed of light. As time went on, the expansion slowed down towards the present, where it is objects that are around 10 billion light years away that are receding at the speed of light.<br /><br />Until recently, we thought the rate of expansion was still slowing down.<br /><br />The problem is that as we look at closer distances (and thus as closer times) to ourselves, the effects of the expansion of space are much harder to detect.<br /><br />When we measure the redshift of our closest neighbour galaxy, andromeda, which is only 2.5 million light years away, we find that it is actually moving towards us. This is because andromeda and the milky way are gravitationally bound to each other. Galaxies cluster together due to gravity, and it is only in the space between these <i>gravity bound clusters of galaxies</i> that space expands. Wherever gravity binds galaxies, that gravity overwhelms any effects of expansion, meaning those galaxies can move towards each other.<br /><br />So we have to look a fair distance away before we can measure any redshifts that are caused by the expansion of space. The redshifts of galaxies in our own cluster are due t <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[SpeedFreek]

Yes of course, I thought I had covered that when I said:<br /><br />"Wherever gravity binds galaxies, that gravity overwhelms any effects of expansion, meaning those galaxies can move towards each other."<br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>