Seeking clarification on red-shift

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In summary, red-shift can be caused by two distinct mechanisms - gravitational redshift and cosmological redshift. Gravitational redshift occurs when a photon loses energy as it escapes a star, making it appear redder. Cosmological redshift, on the other hand, is caused by the expansion of the universe, which stretches the wavelength of the photon and also makes it appear redder. These are two separate processes, but both result in a photon's frequency being lowered.
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acesuv
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I've recently read that red-shift is caused when a photon escapes a star and loses some of its energy, lowering its frequency and therefore making it appear redder. However, I've become very familiar with the fact that light will red-shift as it travels across the universe; I've been under the impression that this is due to the expansion of the universe, which somehow stretches the wavelength of the photon, making it redder.

Am I correct in what I have said? Are these two distinct mechanisms which lower a photon's frequency, or are they the same thing? I have a rather loose conception of how the expansion of space may stretch a photon's frequency, and I think this may be because I heard it on a layman's documentary.
 
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Hi there! There exist both gravitational redshift and cosmological redshift. See here for a brief summary of the phenomena: http://www.asterism.org/tutorials/tut29-1.htm
 

1. What is red-shift?

Red-shift is a phenomenon in which light from an object appears to have longer wavelengths, shifting towards the red end of the spectrum. This is caused by the object's motion away from the observer, known as the Doppler effect.

2. How is red-shift related to the expansion of the universe?

The expansion of the universe causes the wavelengths of light from distant objects to stretch, resulting in red-shift. This is a key piece of evidence for the theory of the Big Bang, as it suggests that the universe is expanding in all directions.

3. What is the difference between red-shift and blue-shift?

Red-shift refers to the lengthening of wavelengths, while blue-shift refers to the shortening of wavelengths. Red-shift occurs when an object is moving away from the observer, while blue-shift occurs when an object is moving towards the observer.

4. How is red-shift used to measure the distance of galaxies?

By measuring the amount of red-shift in the light from a galaxy, scientists can determine its velocity and distance from Earth. This is known as the Hubble law, which states that the farther away a galaxy is, the faster it is moving away from us.

5. Can red-shift be used to study the evolution of the universe?

Yes, red-shift plays a crucial role in understanding the evolution of the universe. By observing the red-shift of light from distant objects, scientists can measure the rate of expansion of the universe and track its history and development over time.

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