whlzki Posted February 17, 2012 Share Posted February 17, 2012 I wasn't sure where to ask such a simple question - so please accept my apology first for my complete lack of knowledge. So... This one simple thought threw me off completely. And I knew it sounded stupid, but I just couldn't get over it! My physic's teacher is out of reach, so I had to turn to the internet for some solid answers. If high level cosmic background waves from the big bang stretched over time to form longer waves (which can be recorded and thus, we can calculate the age of the universe (?)), why hasn't the visible light waves from the very distance galaxies stretched? What is the difference between the visible light of the EM spectrum and the 'light' we see from distant stars? Aren't they exactly the same things...? And continuing from that thought... If light travels in photons (which I believe to be travelling in waves), why does light have a constant speed that will last forever(?)? ... I think I'm missing the point and confusing completely different things together. Link to comment Share on other sites More sharing options...
mathematic Posted February 17, 2012 Share Posted February 17, 2012 "why hasn't the visible light waves from the very distance galaxies stretched?" It is stretched (called 'red shift'). "What is the difference between the visible light of the EM spectrum and the 'light' we see from distant stars? Aren't they exactly the same things...?" It is all e-m radiation, but it encompasses all wavelengths. Light has a constant speed - basic assumption of special relativity. All measurements have confirmed it. Link to comment Share on other sites More sharing options...
D H Posted February 17, 2012 Share Posted February 17, 2012 why hasn't the visible light waves from the very distance galaxies stretched? It has. This is why the most distant galaxies in the Hubble deep field are noticeably red. This redshift is one of the many reasons for the Webb space telescope. The visible light from the furthest galaxies has been red shifted right out of the visible range into the infrared. Finally, this observable redshift is how astronomers "measure" distance to those far-away galaxies. 2 Link to comment Share on other sites More sharing options...
PaulS1950 Posted February 18, 2012 Share Posted February 18, 2012 Expanding space is only one possible explaination for the BMR and the red-shift of light from galaxies. Another possible explaination is that 13.7 billion years ago things were moving very fast away from itself and we are measuring that dopler effect rather than an expanding universe. All the observations would be the same regardless of the cause. The farther away we look the further back in time we see. Ocams (sp) razor would beg why add an expansion, dark energy and a host of other parallels that are not needed when you allow an explosions to burst forth and slow down? Paul Link to comment Share on other sites More sharing options...
swansont Posted February 18, 2012 Share Posted February 18, 2012 Recall that the CMBR is the light that is from the recombination, about 375,000 years after the big bang. Light from galaxies is younger, and so would have not experienced as much of the universe's expansion. Which means it can't have redshifted as much. Link to comment Share on other sites More sharing options...
whlzki Posted February 18, 2012 Author Share Posted February 18, 2012 I see... so even though the light has shifted from the distant galaxies, the speed is still constant? And so is that why we say the 'visible universe'? the part of the universe that we can detect? Link to comment Share on other sites More sharing options...
D H Posted February 18, 2012 Share Posted February 18, 2012 Expanding space is only one possible explaination for the BMR and the red-shift of light from galaxies.[ Another possible explaination is that 13.7 billion years ago things were moving very fast away from itself and we are measuring that dopler effect rather than an expanding universe. All the observations would be the same regardless of the cause. You are looking at the big bang as an explosion in space rather than an explosion of space. All of the observations would not be the same regardless of the cause. Most of what we are seeing in the redshift of the not-so-faraway galaxies is velocity. There is however a big problem with your concept: The remotest of galaxies are apparently moving away from us at a velocity greater than the speed of light. Anything with a redshift greater than three is receding superluminally. This, and a number of other things, are why you cannot look at the big bang as if it were an explosion in space. Link to comment Share on other sites More sharing options...
swansont Posted February 18, 2012 Share Posted February 18, 2012 I see... so even though the light has shifted from the distant galaxies, the speed is still constant? And so is that why we say the 'visible universe'? the part of the universe that we can detect? For regions far enough away, the intervening space is expanding faster than the light can traverse it, so we will never be able to observe that region. 1 Link to comment Share on other sites More sharing options...
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