If light experiences gravitational redshift as said by GR

In summary, the conversation discusses the concept of gravitational redshift and its relation to the initial and final energy of light. It also brings up the idea of redshift from Hubble expansion and where the energy difference goes. The conclusion is that the energy difference goes towards changing the gravitational field strength and mass of the emitter, and also potentially towards the density of energy in the universe. Additionally, the Compton effect and photon momentum may cause a shift to the red side of the spectrum.
  • #1
touqra
287
0
If light experiences gravitational redshift as said by GR, then, where did the difference between the initial and final energy, [tex]E = \frac {hc}{\lambda}[/tex] go?

From Hubble expansion, there is also redshift. Where did the energy difference go?
 
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  • #2
Radiation? (I'm guessing)
 
  • #3
where redshift energies go to

In the simplest case (For that ,imagine two equal photons emited in opposite directions from the massive object):In cowering the difference between inital and final gravitational field strenght of the source of the gravity potential.Accompaning mass of the *emitter* before and after changes.Total energy of the system remains conserved of course.


As of from Hubble expansion red shift,and the question: Where did the energy difference go?:I would say nowhere.Only the density of the energy of the Universe should change.No?

cheers
 
  • #4
I would think that it goes to space itself. (If there is such a thing)
 
  • #5
E = hc/lamda

when you think of your equation, you notice that the energy is less when the photon of light is emmited back to earth. The reason for this is because of the Compton effect, and photon momentum. Since a photon with energy has a mass, when it strikes an object, some of its energy is lost since the collision is not perfectly ellastic. This would cause a shift to the red side of the spectrum.I think :confused: Let me thisnk about that one for a while, Ill get back to you.
 

What is gravitational redshift?

Gravitational redshift is a phenomenon predicted by Einstein's theory of General Relativity (GR). It refers to the shifting of the wavelength of light as it travels through a gravitational field. This means that light traveling out of a gravitational field will appear to have a longer wavelength, or be "redshifted", compared to light that is not affected by gravity.

How does GR explain gravitational redshift?

According to GR, gravity is not a force, but rather a curvature of spacetime caused by the presence of mass or energy. Light follows the curvature of spacetime, and as it travels through a gravitational field, it must expend energy to escape the field. This results in a decrease in the energy of the light, causing it to have a longer wavelength and appear redshifted.

Does light experience gravitational redshift in all gravitational fields?

Yes, according to GR, all gravitational fields will cause light to experience gravitational redshift. The amount of redshift will depend on the strength of the gravitational field and the distance the light has traveled through it.

Can gravitational redshift be observed in everyday life?

Yes, gravitational redshift can be observed in everyday life. One example is the redshift of light from distant stars as it passes through the gravitational field of our Sun. This effect is also taken into account in GPS systems, as the clocks on satellites are affected by the weaker gravitational field in orbit compared to clocks on Earth.

Are there any other factors that can cause redshift in light?

Yes, there are other factors that can cause redshift in light, such as the Doppler effect. This is the apparent change in frequency or wavelength of light caused by the relative motion of the source and the observer. However, gravitational redshift is distinct from the Doppler effect and is solely caused by the presence of a gravitational field.

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