What is a world line?
Q: What is a world line?
A: A world line is the unique path that an object has as it travels through both space and time, usually called spacetime.
Q: How does special relativity explain how time passes for objects travelling at different speeds?
A: According to special relativity, the faster an object goes, the more time slows down for that object. The slower object has a quicker passage of time than the very fast object, which means that time passes much more slowly for them.
Q: What happens when an object reaches the speed of light?
A: When an object reaches the speed of light, it will be zero on the t axis, meaning that it will have made no progress in the time direction. This means that time stops for the observer.
Q: In what areas are world lines used?
A: World lines are very often used in theoretical physics and special relativity, as well as general relativity.
Q: How can we visualize a world line?
A: We can visualize a world line by looking at illustrations which show how objects travelling at different speeds experience different rates of passing time.
Q: Is there any way to change or alter a world line once it is established?
A: Once a world line is established, it cannot be changed or altered since it represents an immutable path through spacetime.
Q: What does "t axis" refer to in regards to reaching the speed of light? A: The "t axis" refers to progress in terms of time - when an object reaches the speed of light its progress in terms of time is zero on this axis meaning that no progress has been made in terms of passing through space-time.
