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Glenn G
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As the Universe expands and the photons stretch to longer wavelengths (say from UV photons to the CMBR now) where has the energy gone since longer wavelength photons have less energy?
Regards,
G.
Regards,
G.
mfb said:It is gone.
There is no global energy conservation in general relativity.
Cosmological redshift is a phenomenon in which light from distant galaxies appears to be shifted towards the red end of the electromagnetic spectrum. This is due to the expansion of the universe, which stretches the wavelengths of the light as it travels through space.
The energy of light is directly proportional to its frequency, so as the wavelength of light is stretched by cosmological redshift, its frequency decreases and therefore its energy decreases as well. This means that the light from distant galaxies appears redder and less energetic than it would if there were no cosmological redshift.
The energy is not actually "lost" in the traditional sense. It is simply spread out over a larger distance as the universe expands. This is similar to how the energy from a spring is spread out over a larger distance as it is stretched.
Cosmological redshift is measured using a unit called redshift z, which is calculated by comparing the observed wavelength of a distant object to its known rest wavelength. The higher the value of z, the greater the redshift and the farther away the object is from us.
Cosmological redshift is one of the key pieces of evidence for the expanding universe and the Big Bang theory. It also allows us to measure the distances and velocities of distant galaxies, which helps us understand the structure and evolution of the universe.