# High Frequency Photons: More Mass, More Bend?

• B
• mdeng
In summary: Well, this get's back to a Newtonian example I gave some years ago: If you 'drop' a Jupiter mass BH from a tower, it will reach the ground faster than a canonball - because the Earth moves so fast to the common center of mass. But this violates the the common understanding that we are discussing test objects of miniscule mass compared to Earth - even if one might be thousands of times the mass of another.This is not considered a violation of 'universal free fall' because it is outside the bounds of applicability of that principle.
mdeng
TL;DR Summary
gravitational rainbow effects
Since high frequency photons have more relativistic mass, should we expect them to bend more than lower frequency lights when traveling through a gravitational field, thus produce a rainbow effect? But we don't seem to experience rainbow effects with star light.

Motore, OmCheeto and PeroK
mdeng said:
should we expect them to bend more than lower frequency lights when traveling through a gravitational field
No. There are many issues with your question. Just to mention a couple:

- Relativistic mass is essentially nothing but a different name for energy. Its has fallen out of use in most of the physics community.
- You cannot use relativistic mass and just insert it into Newtonian gravitation formulae. Newtonian gravity is not compatible with relativity.
- Even if you could use Newtonian gravitation and relativistic mass, you should not expect high frequency photons to bend more. Even in classical mechanics with Newtonian gravity, the motion of a test particle in a gravitational field does not depend on the mass of the test particle.

Hornbein, vanhees71, topsquark and 3 others
Thanks. But what's behind the statement of "even light can't escape the gravitational pull of a black hole", is it not due to photons having mass therefore are subject to the pull?

PeroK
mdeng said:
Thanks. But what's behind the statement of "even light can't escape the gravitational pull of a black hole", is it not due to photons having mass therefore are subject to the pull?
No. Even in Newtonian gravity you could have massless objects affected by gravity.

But in GR the reason light cannot escape a black hole is because there are no null geodesics going away from the singularity inside the horizon

topsquark
Oh, I also realized my ignorance in my question because, as another post said, "If you shoot two rocks past the Earth, one more massive than the other, with the same initial positions and velocities, they will both follow identical trajectories. By analogy, the same should be true for two photons of different energies which are shot with the same initial positions and velocities (the velocities have to be the same in this case because they're both photons)."

mdeng said:
Thanks. But what's behind the statement of "even light can't escape the gravitational pull of a black hole", is it not due to photons having mass therefore are subject to the pull?
No. That is a very popularized statement and as all popularized statements should be taken with a gallon of salt. The reason light cannot escape a black hole is the way that spacetime curves around it.

vanhees71 and topsquark
hmmm... I seem to recall that "light" generates a gravitational field because although it doesn't have mass, it does have momentum. So if we were to take a light beam and shoot it past a star, that light beam should tug on that star. And that tugging should be seen reciprocally by the light beam. Otherwise, it seems to violate Newton's law of action and reaction.

Now if two light beams with different frequencies were to take that journey, it seems the answer to the OP's question would be yes.

I can forewarn you that if your answer includes the word "tensor" I will not understand it. I spent about a week trying to figure out what those are, but I could find no clear examples.

-------
ps. Just notice the [A] level marker. Ok to call on Drakkith to let me know that this is so far over my head that even the simplest explanation will be beyond the wildest dreams of my comprehension.

OmCheeto said:
hmmm... I seem to recall that "light" generates a gravitational field because although it doesn't have mass, it does have momentum. So if we were to take a light beam and shoot it past a star, that light beam should tug on that star. And that tugging should be seen reciprocally by the light beam. Otherwise, it seems to violate Newton's law of action and reaction.

Now if two light beams with different frequencies were to take that journey, it seems the answer to the OP's question would be yes.
Well, this get's back to a Newtonian example I gave some years ago: If you 'drop' a Jupiter mass BH from a tower, it will reach the ground faster than a canonball - because the Earth moves so fast to the common center of mass. But this violates the the common understanding that we are discussing test objects of miniscule mass compared to Earth - even if one might be thousands of times the mass of another. This is not considered a violation of 'universal free fall' because it is outside the bounds of applicability of that principle.

In this sense, if you somehow had a light pulse whose total energy were a significant fraction of Earth's in their common center of momentum frame, passing earth, it would behave differently than one with plausible energy. However, a key difference is that in the COM frame you would have measurable motion of the earth.

vanhees71, topsquark and OmCheeto
mdeng said:
But what's behind the statement of "even light can't escape the gravitational pull of a black hole", is it not due to photons having mass therefore are subject to the pull?
It is not.
Light always travels in a straight line (formally called a “lightlike geodesic”) through spacetime. The apparent deflection of light in a gravitational field is actually the light moving in a straight line through curved spacetime, somewhat analogous to how a straight line on the curved surface of the Earth appears curved on a two-dimensional flat map (look at the airplane route between Tokyo and Chicago for an example).

Inside the event horizon of a black hole, the spacetime is so curved that no lightlike geodesic in any direction will pass out through the event horizon; instead they all eventually reach the singularity. The most intuitive way of seeing this may be to Google for “tipped light cone black hole” which will bring up some good diagrams.

vanhees71, PeroK and topsquark
mdeng said:
Since high frequency photons have more relativistic mass, should we expect them to bend more than lower frequency lights when traveling through a gravitational field
No, because, even leaving aside the other valid objections that others have already made, in GR an object's trajectory through spacetime does not depend on its mass. Gravity is not a Newtonian force in GR; it's spacetime geometry. An object's trajectory (assuming no non-gravitational forces act on it, which applies to the scenario you are posing) depends only on its initial 4-velocity and the geometry of spacetime.

vanhees71 and topsquark
OmCheeto said:
I can forewarn you that if your answer includes the word "tensor" I will not understand it. I spent about a week trying to figure out what those are, but I could find no clear examples.

OmCheeto, topsquark and DrClaude

## 1. What are high frequency photons?

High frequency photons are particles of electromagnetic radiation that have a higher energy and shorter wavelength compared to lower frequency photons. They are also known as gamma rays and have the ability to penetrate through materials and cause damage to living cells.

## 2. How does the mass of a high frequency photon affect its behavior?

The mass of a high frequency photon does not affect its behavior. Photons are considered to be massless particles and their behavior is determined by their energy and wavelength. However, high frequency photons have a higher energy and can therefore cause more damage compared to lower frequency photons.

## 3. Why do high frequency photons bend more than low frequency photons?

This phenomenon is known as refraction and it occurs when light passes through a medium with a different density. High frequency photons have a shorter wavelength, which means they interact more with the atoms in the medium, causing them to bend more compared to low frequency photons with longer wavelengths.

## 4. What are some practical applications of high frequency photons?

High frequency photons have a variety of practical applications, such as in medical imaging and cancer treatment. They can also be used in industrial processes, such as sterilization and food preservation. In addition, high frequency photons are used in communication technology, such as in satellite transmissions and fiber optic cables.

## 5. Can high frequency photons be harmful to humans?

Yes, high frequency photons can be harmful to humans if they are exposed to them in large doses. This is because their high energy can cause damage to living cells and DNA. However, in small doses, high frequency photons are used in medical treatments and are not harmful. It is important to limit exposure to high frequency photons and use protective measures when working with them.

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