Why does gravity affect light if light doesnt have mass??
Author : jschroep420
Submitted : 20180614 04:24:57 Popularity:
Tags: affect gravity light mass doesnt
As Neb and a couple others have explained, light follows space along the shortest distance between two points on the curved surface. That's called the geodesic
As Neb and a couple others have explained, light follows space along the shortest distance between two points on the curved surface. That's called the geodesic: 1. relating to or denoting the shortest possible line between two points on a sphere or other curved surface
And by the general theory of relativity space.time gets curved in the presence of mass.energy. The effects we get from that curved space.time are those we attribute to gravity. And that's why light is affected by gravity, it's because the space the light is traveling through is affected.
So anything, massive or not, will follow the curves of space as they are created by the presence of mass.energy. When you drop your physics textbook in class, it falls following the curve of space between your desk top and the floor.
Why does seeing someone or something have an impression on your mind even if those things never touch your mind?
Gravity warps the space light travels in therefore affecting the light's direction
Gravity warps the space light travels in.so the light bends as it follows along the space not unlike water following the bend in a pipe. The gravity doesn't directly affect the light, only it's propagation medium (space time)
it only affects the path of light in the sense that it affects the space that the light is passing through. If space(time) is bent, light will seem to bend even though, from the point of view of the light itself, it does not.
Light has energy and its path is therefore deflected according to the massenergy equivalence of the famous equation.
Gravity does not affect light. A gravitational field does NOT affect light, no matter how strong it is.
As pointed by @John De Witt: "Light, unless refracted or reflected, goes in a straight line."
Once you know this, you must know that the optical density of any elastic transparent medium increases as gravity increases, so the light curves in regions where stronger gravitational forces are present.
Finally, you may know that the gravitational and magnetic forces in the Black Hole are so strong that matter transforms into a 'singularity' where light cannot exist as photons.
This has nothing to do with mass or momentum. You can derive geodesic equations from solutions of general relativity that describe the path that ANYTHING takes in spacetime. The geodesic equation DOES NOT depend on the mass or momentum of the object  depends solely on geometry of spacetime and choice of coordinates.
*Edit for idiot who downvoted me
Here is a geodesic equation from general relativity: d²xᵃ⁄dλ² = Γᵃᵤᵥ(dxᵘ/dλ)(dxᵛ/dλ)
Where is the mass, momentum, or other fundamental property in the equation? This depends on the components of the metric tensor and choice of coordinates.
Light does not have mass, but they do have momentum, and a change in momentum yields a force, so in actual fact, light is able to physically interact with matter.
If you'd rather think of it this way, it doesn't. Light, unless refracted or reflected, goes in a straight line. What gravity does is change "straight." That make you feel better?


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