0 Members and 1 Guest are viewing this topic.

Neutron stars are often seen blue.

- 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.

- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

- 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.

Evan - there is a misdemeanor in the logic presented here.You say here below (example 1) that a photon gains energy as it falls into a gravitational well and that - If a photon gains energy, its frequency is higher.Quote from: evan_au on 27/03/2018 21:59:39- 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.But here you say (example 2) that - If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.Quote from: evan_au on 27/03/2018 21:59:39- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.Having already explained that:Quote from: evan_au on 27/03/2018 21:59:39- 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.So which is it?Does a photon falling into a gravtational well gain energy and frequency - (blueshift) as in example 1?Or does a photon falling into a gravitational well lose energy and frequency - (redshift) as in example 2?

that a photon trying to climb out of a gravity well is redshifted, whereas a photon falling into the well is blueshifted.

How can he mean thisQuote from: Kryptid on 28/03/2018 00:54:32that a photon trying to climb out of a gravity well is redshifted, whereas a photon falling into the well is blueshifted.If he said this:Quote from: evan_au on 27/03/2018 21:59:39- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

- 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 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.

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 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.

A clock raised above a gravitational mass will be observed to tick faster...why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?

A logical explanation of mine to this is that photons instead, gain frequency inside a gravitational field and in black holes their wavelength becomes too small, or their frequency too big that it can't escape the black hole.

- A photon loses energy as it climbs out of a gravitational well

why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?

A clock ticking slower has a reduced frequency/energy....... A clock ticking faster has an increased frequency/energy.

Quote from: timey on Yesterday at 03:25:49why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?

there is a possibility that the temperature of the black hole does increase with added mass

My reference clock, when making these considerations, is 'always' the far away clock, that confirms that the clock where you are situated is ticking differently to the clock you are observing. (I did mention this in the post 7)

So - according to the far away clock, the clock that is elevated from the ground has a higher frequency than the clock on the ground.A higher frequency is usually accompanied by a higher energy.

@jeffreyH The far away clock is a recognised concept in relativity with which to detect if 2 clocks that are in closer proximity to each other are ticking differently.@evan_au Yes - there isn't that much known about black holes that isn't theoretical, where the theories can't quite cope with the concepts anyway. And some of what is known about black holes doesn't fit with theory. That's what makes black holes a really fun subject to discuss on New Theories. However, the OP has not returned, and I've got stuff to do anyway, so I'll leave you's to it.

@Colin2B You saidquote"The photon frequencies behave in exactly the same way as the clocks."Wrong!Have a 'source' release a photon at G, and A will observe that photon to be redshifted, F will observe that photon to be further redshifted. Move the 'source' from G to A, and F will observe the 'source' releasing a photon at A, as blushifted compared to the photon the 'source' released at G.

They measured a clock on the ground with a far away clock, and, after they jacked the clock up a metre elevation, they measured it again with the far away clock.