/sci/ - Science & Math

It gets spread out over a greater area.
No energy is actually lost.

Huge article in Scientific American over this a few months back. Let me go find if for you...

>>2065886

This, the wavelength is increasing, it's not losing energy, just going below the visible spectrum

>>2065888
Hmm... all I can find is the intro. i don't have a subscription and I gave someone the original magazine.

http://www.scientificamerican.com/article.cfm?id=is-the-universe-leaking-energy

Sounds like an entropy problem to me. A large universe is a more disordered universe.

>>2065886
thing don't work that way in the quantum world of the photons

>>2065888
i would be very grateful if you can find it

>>2065895
thanks, i'll google for more

>>2065882
because frequency=speed/wavelength, obviously speed is constant, so when wavelength increases(which is what happens when blue light gos to red), its frequency is decreased, and no loss of energy occurs

>>2065886
>>2065892
no

The red-shifting of light IS the conservation of energy. If a photon is moving further away from a gravitational source, it has a greater potential energy. Just like a massive object must give up energy in the form of speed to move to a higher gravitational potential, light must give up energy in the form of frequency to move to a higher gravitational potential.

That's gravitational redshift. If you're thinking of redshift from velocity, everything has a different amount of kinetic energy depending on the reference frame in which you measure it. This again makes light consistent with massive objects. The kinetic energy of a massive object changes when the reference changes because the velocity changes. The kinetic energy of light changes because the frequency changes.

>>2065932
<span class="math">E = hf = \frac{hc}{\lambda}[/spoiler]
The energy of light changes when you change the frequency or wavelength. See>>2065934

>>2065944
What's h?

http://en.wikipedia.org/wiki/Redshift

Its a good site, OP have a browse.

The frequency lowers, but the photon has a longer fetch. So energy is conserved.

>>2065981
Plank's Constant.

think about it from the point of view of an electromagnetic wave:


an oscillating E and B field that are perpendicular to one another, with the oscillations perpendicular to to the direction of travel (poynting vector).


if the instantaneous point at which the maximum in the E field is at X = 0, normally the next maximum would occur at another point X = x1, at some time T=t1...


when the reciever/observer is moving away from the wave, then that maximum APPEARS to have shifted its position.
this is the classical picture. I dont really know how to explain it with QED.
also, even with non-relatistic QM, it has nothing to do with some special quantum property of the system.


Quantum effects dont even become significant for a traveling electrogmagnetic wave until you get deep in the UV/x-ray region of the spectrum...

even then, their affects are greatly explained by classical ED...


and it has nothing to do with the quantum nature of the particles that absorb/emit the photons.

>>2065993
*Planck

Sorry.

>>2065934
yes this is in the case of conventional red-shifting where depending on your speed relative to the light source you get redshift or blue-shift

but intergalactic space is not bent by gravity
i mean what happens to the energy lost in the red-shift caused by the expansion of the universe

>>2065997
Thanks

>>2065934
this was a good post. if you were here i'd give you a beer. never thought about it in that way before