Photon Orbits, can they occur?

[IDMclean]

It occured to me today that assuming we have a gravitational source, and it emits a photon. Could the Photon's trajectory curve due to space-time such that it goes into orbit about the gravitational source, and if so how long/far would it have to travel before the curviture brought it into orbit?

 

Note, I am not necessarily talking about blackholes but smaller things like solar systems, suns, planets, etc.

[Boerseun]

It occured to me today that assuming we have a gravitational source, and it emits a photon. Could the Photon's trajectory curve due to space-time such that it goes into orbit about the gravitational source, and if so how long/far would it have to travel before the curviture brought it into orbit?

 

Note, I am not necessarily talking about blackholes but smaller things like solar systems, suns, planets, etc.

If any object's mass is sufficient to make a photon 'orbit', you'll have a black hole by definition.

 

Making a photon 'orbit' is certainly possible, all you'll have to do is to add mass, until the desired spacetime curvature is achieved! :shrug:

[Farsight]

KickAss: I hope to explain something very relevant to this in the next week or so.

 

Boerseun: I hope you'll be pleasantly surprised.

[Boerseun]

KickAss: I hope to explain something very relevant to this in the next week or so.

 

Boerseun: I hope you'll be pleasantly surprised.

Go for it...

[IDMclean]

Well what I mean is. As a photon travels away from or towards a gravitational source it's trajectory gets bent as it follows the geodesic.

 

Now with a blackhole the curviture near the center is so extreme as to not allow photons to escape.

 

What I am asking is, if you continue to curve a photon's trajectory as it travels away from a gravitational source, will there be a sufficient distance that will produce a photon orbit? Say a few light years or so. If so, how would we know about these photon orbits? Seeing as we wouldn't be able to see them.

[snark1100]

curious thought...the only objects massive enough and compact enough for a photon to be bound to it would seem to be a black hole though. intuitively, it would be able to orbit at exctly the event horizen, the boundary of it's being trapped, but i'll try the calculation.

[LaurieAG]

Well what I mean is. As a photon travels away from or towards a gravitational source it's trajectory gets bent as it follows the geodesic.

 

Now with a blackhole the curviture near the center is so extreme as to not allow photons to escape.

 

What I am asking is, if you continue to curve a photon's trajectory as it travels away from a gravitational source, will there be a sufficient distance that will produce a photon orbit? Say a few light years or so. If so, how would we know about these photon orbits? Seeing as we wouldn't be able to see them.

 

Interesting. Did you know that you can model a photon orbit with a 'feedback' loop?

[Boerseun]

Say a few light years or so. If so, how would we know about these photon orbits? Seeing as we wouldn't be able to see them.

Because you won't see it, it'll qualify as a black hole. The orbit would be the event horizon, and if you're talking of an orbit of a few light-years wide, you'll simply have a black hole a few light years wide. And that will take quite a lot of mass. But it would certainly be possible, if collecting and assembling the mass wasn't an issue...

I'm not too sure of their size, but the biggest black holes exist at the hearts of galaxies. And even they won't have enough mass to have an event horizon measured in light-years!

[IDMclean]

I have to ask, does mass cause curviture across an infinite space-time sheet (Continious Space-Time)? If mass (any non-zero mass) causes energy to change it's curve over distance (perhaps an infinite distance), then would not a slight bend result in a eventual orbit?

[LaurieAG]

I have to ask, does mass cause curviture across an infinite space-time sheet (Continious Space-Time)? If mass (any non-zero mass) causes energy to change it's curve over distance (perhaps an infinite distance), then would not a slight bend result in a eventual orbit?

 

Stephen Hawking covered this topic in one of his books from the 90's. Have you read about what happens when the orbiting photon crosses (comes back upon) its own track?

 

Considering that a feedback model of an orbiting photon allows you to create an accurate (and very stable) model of an Einstein Ring (based on an interruption to the photon loop), why would you want to introduce infinity, let alone time travel?

[IDMclean]

I did not introduce time-travel except in the standardly accepted forward direction.

 

All I am saying is that I conventionally think of a photon being emitted in a straight line. However I have been thinking about it and it occured to me that a photon emitted will have it's path curved (or at least conceptually it will) by the body that emits it. Now admittedly at the small scale this curve is negligable, however assuming the curving continues infinitely, then eventually the photon should fall into orbit around the emitting body, perhaps even eventually falling back into the emitting body with sufficent time. Assuming it isn't absorbed by another body.

 

Which is to say that a light orbit will be achieved by a body of rest mass irregardless (or in regard to?) of it's swartzchild radius. I am not talking about blackholes. I am talking about normal everyday masses. Considered as closed systems. Keeping in mind that the closed system strictly can not lose or gain energy or mass, all conservations must be observed. Assuming that the body considered emits the photon, it would eventually have to re-absorb the photon in order to keep it from leaving the system, right?

 

Just a puzzle in my head, that I know I could solve if I had better maths, but currently am incapable of expressing except in plain english (nothing wrong with that).

[LaurieAG]

All I am saying is that I conventionally think of a photon being emitted in a straight line. However I have been thinking about it and it occured to me that a photon emitted will have it's path curved (or at least conceptually it will) by the body that emits it. Now admittedly at the small scale this curve is negligable, however assuming the curving continues infinitely, then eventually the photon should fall into orbit around the emitting body, perhaps even eventually falling back into the emitting body with sufficent time. Assuming it isn't absorbed by another body.

 

Hello KickAssClown,

 

This first image is of the set-up that I used around 8 years ago to simulate an orbiting photon. If you'd like to learn how to use this type of setup to simulate an Einstein Ring, I have a series of screen capture images that show the general process.

[pgrmdave]

I have to ask, does mass cause curviture across an infinite space-time sheet (Continious Space-Time)? If mass (any non-zero mass) causes energy to change it's curve over distance (perhaps an infinite distance), then would not a slight bend result in a eventual orbit?

 

Not necessarily - you could end up with a different type of conic section.