# Light bent in gravitational field

• tomz
In summary: The initial position and direction of motion of the ray of light are affected by the presence of the rocket. The motion of the rocket is not affected by the presence of the ray of light.In summary, the concept of whether a world-line is curved or not is defined independently of other world-lines. While the rocket and light beams may appear to have initially tangent trajectories, the relevant notion is a world-line in spacetime. The amount of bending does not depend on the speed of the rocket, and if there is no rocket, the presence of a light source will still result in bent light.
tomz
i am new to GTR. Mytext book use an example to show ligt bendinf.
when a light release from the back of the rocket which goes around the earth, since the rocket is in free fall, light would not bent relative to the rocket, but bent relative to earth.

my problem is, is that means the amount of bending depend on the speed of the rocket?
if the rocket is very fast, than light would travel greater distance relative the earth, so there more bending?

If there is no rocket, but just a light source above the earth, would it bent at all?

Thank you...

tomz said:
i am new to GTR. Mytext book use an example to show ligt bendinf.
when a light release from the back of the rocket which goes around the earth, since the rocket is in free fall, light would not bent relative to the rocket, but bent relative to earth.
The notion of whether a world-line is or is not curved (is or is not a geodesic) is defined independently of other world-lines. I think what's probably confusing you here is that you're imagining two trajectories in space, the rocket's and the light beams. These two trajectories are initially tangent, but later diverge. But the relevant notion is not a trajectory in space, it's a world-line in spacetime. The world-lines of the rocket and the light beam are *not* initially tangent.

It would indeed be a problem if two geodesics, initially tangent at a given point in spacetime, later diverged. But that isn't the case here.

tomz said:
my problem is, is that means the amount of bending depend on the speed of the rocket?
if the rocket is very fast, than light would travel greater distance relative the earth, so there more bending?

If there is no rocket, but just a light source above the earth, would it bent at all?

Nothing here depends on the source. Given the initial position and direction of motion of a ray of light, you can find its later motion.

## 1. How does gravity bend light?

Gravity bends light by warping the fabric of space-time itself. The more massive an object is, the more it bends the space around it, causing light to follow a curved path.

## 2. What is the significance of light being bent in a gravitational field?

This phenomenon is significant because it provides evidence for Einstein's theory of general relativity, which describes how gravity works as a result of the curvature of space-time.

## 3. Can light be bent by any type of gravitational field?

Yes, light can be bent by any type of gravitational field, including those created by massive objects such as planets, stars, and black holes.

## 4. How does the bending of light affect our perception of the universe?

The bending of light can cause objects to appear distorted or appear in a different location than their actual position. This can affect our perception of the universe and our understanding of the objects within it.

## 5. Is the bending of light in a gravitational field the same as the bending of light through a lens?

No, the bending of light in a gravitational field is a result of the curvature of space-time, while the bending of light through a lens is a result of refraction. However, both can cause light to follow a curved path.

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