- #1
blueelectrons
- 2
- 0
What is the exact difference between null geodesics and null curves? Please explain both qualitatively and quantitatively.
A null geodesic is a path or curve in spacetime that is followed by a massless particle, such as a photon. It is a path of zero length and is considered the straightest possible path in spacetime.
Null geodesics differ from timelike and spacelike geodesics in terms of their relationship to the spacetime metric. Timelike geodesics are curves that follow the flow of time, while spacelike geodesics are curves that are perpendicular to the flow of time. Null geodesics, on the other hand, have zero length and are neither timelike nor spacelike.
In general relativity, null geodesics play a crucial role in describing the motion of light and other massless particles in curved spacetime. They also provide a way to measure distances and angles in curved spacetime, which is important for understanding the effects of gravity on the path of light.
Yes, null geodesics can be curved in curved spacetime. This is because the path of a null geodesic is determined by the curvature of spacetime, just like timelike and spacelike geodesics. However, null geodesics always have zero length, so they may appear to be straight lines when viewed from a certain perspective.
A null geodesic is a specific type of curve that follows the shortest possible path in spacetime, while a null curve is a more general term that refers to any curve with zero length. Null geodesics are a subset of null curves, and they have additional properties such as being the path of a massless particle.