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How does light lose energy as it travels over distance? 
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#1
Jun1512, 08:51 PM

P: 40

So the universe is said to be expanding because light's wavelength is spreading out at a greater rate per greater distance, but with the wavelength becomes longer, the energy becomes smaller, so where is that energy going? How is it actually being lost?



#2
Jun1512, 09:07 PM

P: 3

I don't think energy is being lost I think our observations of it become different. For instance when moving closer to a light source
the light becomes stronger and the frequency we observe becomes larger. The inverse happens when we move further away from the light source. The doppler effect makes it seem like the light is changing frequency. 


#3
Jun1512, 10:24 PM

P: 1,781

The question remains: where does (did) the energy of a cosmologically redshifted photon go? If you get on a train moving very fast and look behind you the light is also redshifted. Where did the energy go in this easier case? 


#4
Jun1512, 10:30 PM

P: 1,414

How does light lose energy as it travels over distance?
If our universe is a finite expanding wave in some medium of unknown structure, then it's reasonable to suppose that the total energy of our universe is decreasing  and if so, then the behavior of waves in media at less than the universal scale is in accordance with the behavior of the universal wave. 


#5
Jun1512, 11:57 PM

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#6
Jun1612, 12:32 AM

PF Gold
P: 1,376

I view it that way  light that is travelling toward us does not undergo any change, it's coordinate system that changes over time i.e. measurement sticks become shorter and clocks become faster. So the question actually should be where matter gets energy instead of where light is putting it. 


#7
Jun1812, 09:25 AM

P: 44

I can see how it would work with waves, since although a wave would get longer it would also come in for a longer time so the total amount would stay the same. I have no idea how this would work with photon's since you'd need to get more of them somehow.



#8
Jun1812, 10:44 AM

P: 27

I already answered this question in this other thread.



#9
Jun1812, 01:58 PM

P: 22




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