# Laser Light vs Gravity

Tyloki

## Main Question or Discussion Point

I understand that the path of light from a Star bends when it moves beside a large mass.

My question is this:

Does the path of Laser Light bend when it moves beside a large mass, and if so, does it bend in the same way the light from a star bends?

I'm curious to know if the fact that light from a star goes in all directions makes any difference on the way the light travels when it meets a planet or other large mass.

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chroot
Staff Emeritus
Gold Member
Originally posted by Tyloki
I'm curious to know if the fact that light from a star goes in all directions makes any difference on the way the light travels when it meets a planet or other large mass.
Each individual photon will follow the shortest possible path through the curved space. If the photons all have different initial directions, as from a nearby star, they will all follow different paths through the space.

Laser light, on the other hand, consists of photons all going in the same direction, and thus all the photons will follow virtually the same trajectory through the curved space.

- Warren

Tyloki
Basically, if we were to follow a single photon from a star and a single photon from a laser, the 2 would follow the same path when traveling around a large plant?

I'm asking because I'm curious about the nature of light with respect to space-time. Do light waves cause Space to vibrate, and if so, are those waves in any way similar to the waves on the surface of a puddle? If they are, is it at all possible that the mass would cause some sort of interference that would cause the photons from star light to move in a different way than the ones from a laser?

chroot
Staff Emeritus
Gold Member
Originally posted by Tyloki
Basically, if we were to follow a single photon from a star and a single photon from a laser, the 2 would follow the same path when traveling around a large plant?
Assuming the two photons are travelling the same initial direction, yes.
Do light waves cause Space to vibrate, and if so, are those waves in any way similar to the waves on the surface of a puddle?
No, space does not vibrate.

- Warren

I fail to see the difference in Photons that come from a star and from a laser....so if the protons are the same then how could their travel be different along the same path? yes? no? do I not have the full idea of a laser or of a proton?

chroot
Staff Emeritus
Gold Member
Originally posted by Coughlan
I fail to see the difference in Photons that come from a star and from a laser....
Exactly correct. Assuming they are travelling in the same direction initially, the photons from either source would follow the same path.

- Warren

pmb

Originally posted by chroot
Each individual photon will follow the shortest possible path through the curved space. If the photons all have different initial directions, as from a nearby star, they will all follow different paths through the space.
That is not exactly correct. Light follows a geodesci i.e. a path of extremal length. In the case of light that extremal length is always zero. However this is not a Eucledian distance but another kind of "distance."

For definition of "geodesic" see
http://www.geocities.com/physics_world/ma/geodesic.htm

Pete