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New Theories / Re: Gravitational shift or not?
« on: 27/03/2018 21:59:39 »
You are quite right to say that photons don't change their speed (as seen by someone measuring it in their laboratory).
But observers do change their perception of time depending on where they are in a gravitational well.
- For someone in a deep gravitational well, their time goes more slowly. So they perceive the frequency of an incoming photon to be higher than someone outside the gravitational well. This is gravitational blueshift for incoming photons.
- Similarly, someone outside the gravitational well will have time pass more quickly than someone inside a gravitational well. So they perceive the frequency of the photons as lower. This is gravitational redshift for escaping photons.
Perhaps another way to look at this is from the viewpoint of photon energy:
- A photon has mass
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy as it climbs out of the gravitational well that its energy would become zero and its frequency would become zero. There is then nothing to detect, and light can't escape a black hole.
See: https://en.wikipedia.org/wiki/Gravitational_redshift
They start with an incredibly high surface temperature, hot enough to emit X-Rays, so in that sense I guess you could say that their color is blue.
But this is due to the spectrum of black body radiation, rather than any gravitational effects.
See: https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature
Edit: I added the purple text to clarify the confusion I caused below...
But observers do change their perception of time depending on where they are in a gravitational well.
- For someone in a deep gravitational well, their time goes more slowly. So they perceive the frequency of an incoming photon to be higher than someone outside the gravitational well. This is gravitational blueshift for incoming photons.
- Similarly, someone outside the gravitational well will have time pass more quickly than someone inside a gravitational well. So they perceive the frequency of the photons as lower. This is gravitational redshift for escaping photons.
Perhaps another way to look at this is from the viewpoint of photon energy:
- A photon has mass
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy as it climbs out of the gravitational well that its energy would become zero and its frequency would become zero. There is then nothing to detect, and light can't escape a black hole.
See: https://en.wikipedia.org/wiki/Gravitational_redshift
Quote
Neutron stars are often seen blue.Neutron stars are extremely small, and often shrouded in the scattered remains of the star that exploded during their formation. Some of them also have a very hot accretion disk, as they consume matter from nearby stars.
They start with an incredibly high surface temperature, hot enough to emit X-Rays, so in that sense I guess you could say that their color is blue.
But this is due to the spectrum of black body radiation, rather than any gravitational effects.
See: https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature
Edit: I added the purple text to clarify the confusion I caused below...
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