Can light be in orbit around anything? Maybe all extra-galactic light we see is images in orbit?

Question

So we see faint objects billions of light years away. Maybe what happened is that us and nearby galaxies such as andromeda are in orbit around a massive gravitational source, light from andromeda goes into orbit around this source as well, then billions of years later we reach it by chance (our paths cross) and see what appears to be a galaxy billions of light years away. But it is actually just a very old image of andromeda.
And so on with all the other distant galaxies - they are just old orbital images.

Answer 1

an orbit occurs when something is gravitationally bound to something else, even though both things are separate from each other and moving. The moon is in orbit around the earth, and the earth makes a small "wobble" as it orbits the moon. Both are in orbit around the sun. Since the moon doesn't speed up (appreciably), we can think of it as traveling in one direction at a fixed speed. The mass of the earth warps space, pulling the moon toward it with a fixed acceleration. This pull, combined with the moon trying to go in a straight line, causes the moon to orbit the earth in a curved path. Think of a ball at the end of some string--you swing it over your head and it goes in circles because the string (gravity) pulls it toward your hand. If you let go, the ball flies off in a relatively straight line (Earth pulls it down, of course). Similarly, if the earth were to suddenly "let go" of the moon, the moon would fly off and have only to deal with the sun.

Now, gravity isn't likely to change, as mass is the direct determinant of gravity. Speed, however, can change. If the moon were to speed up, its orbit would move further from the earth, and likely become more eliptical --depending on how the speed change was accomplished. With enough extra speed, its orbit would become open, or hyperbolic; it would fly off and never come back. The speed that the moon would have to reach to break free of the earth's gravity is often reffered to as the escape velocity.

Now, this is all very simplified, but helps to understand what comes next.

Light has a fixed speed of about 186,000 miles per second. In order for light to get caught in an orbit, there would have to be a mass that had an escape velocity of greater than 186,000 miles per second. The only thing in existence that is that massive is a black hole. Once light goes into orbit around a black hole (which is not a hole at all, its just a really, really massive bunch of material) it can never escape, therefore, we would never actually see that light. That is why they call it a black hole.

So, the short answer is no, light isn't caught in orbit around some huge massive gravitational source. If it were, the object would have to be so big that all light was in orbit around it, and we would be too. Its hard to explain, but we wouldn't see anything...or not much, anyway, if this were the case. All the light would be going nearly the same direction, like a laser, and we would be right in the middle of it.

Answer 2

Let's deal with the common case (Newtonian physics) and not the bizarre exceptions (relativistic influences).

The answer is no, light does not orbit anything. Usually, light ( like all electro-magnetic radiation) travels in all directions away from its source in straight lines. Special sources can be created which radiate in specific directions. However, once radiated, light will continue to in a straight line until it encounters something to reflect, refract, diffuse or absorb it.

In a way, it would be easy mistakenly consider the fact that the sky is blue as evidence that light is in 'orbit' around the earth. In actuality of course, this is the result of atmospheric diffusion process which scatters short wavelengths. This, by the way, fully obeys the 'straight line rule' as stated above.

There are some strange and interesting exceptions to this 'straight line rule' brought about by relativistic influences of extreme gravitational fields, but none result in light traveling in an orbit. If you like the notion of light in 'orbit', you might enjoy learning more about relativistic behaviors of light, matter and time.

Answer 3

For light to orbit an object the usual orbital equation must be satisfied balancing centripetal force against gravitation. Given that light travels at lightspeed, the only radial gravitational field sufficiently strong to bend its path into a closed orbit would require skimming a black hole's event horizon.

The distribution of cosmic background radiation temperature variations is definitive - the universe is a rather simple straighforward place overall.

Answer 4

All I know and learnt is that light=light waves. That's how the whole shadow thing comes from. If light could orbit around things then our shadows would somehow be distorted.

As for outer space the same rule applies but there are much more sources of light and deflection of light.. Maybe that's what you mean.

Answer 5

The possibility exists but since the stars, or black holes, objects that can deflect beams of light, are always on the move, means that no light beam can revolve around a fixed set of stars or black holest to be continously bent to come back on itself.....the same originating location.

Answer 6

Technicall it could orbit a black hole. No what you suggest is impossible. It would have been detected by its gravitational effects years ago.

Answer 7

well I suppose that light obits around a black hole before it is sucked in, and to anser your question no