Title: 4 Simultaneity
Course: Relativity > Section: Module 9: 4 Simultaneity

4. Simultaneity

Explanation:

Simultaneity is the idea that two events occurring at the same time for one observer may not occur simultaneously for another observer moving relative to the first. This challenges our intuitive understanding of time.

Example:

If two lightning strikes hit two different points along a train track, a person on the train moving toward one strike might see it before the other. An observer standing still on the ground might see the strikes as simultaneous, demonstrating that time is relative.

5. Mass-Energy Equivalence