• The equation for the spacetime interval: (ct)²−x² = ± (constant)²
• This represents the spacetime interval in a spacetime diagram.
• Think of it as a graph where time and space are plotted together.

Real-world example: When you plot a graph in math class with X & Y axes, think of a spacetime diagram as plotting time against space. This visual aids in understanding relativistic concepts.

• For the equation with a positive right-hand side.
• Imagine you're watching two events
• First one is where both you and your friend agree on when and where it happened.
• The second one is trickier. You see it in one way, but your friend moving at a different speed sees it differently.
• In simpler terms, these events occur at different times but same place.

Real-world example: Think of it like two friends watching a race. One stands still, while the other moves. Both see the race start, but they disagree on when the other events in the race happen because of their motion.

• This time, events take place at different positions but same time.

Real-world example: Imagine two fireworks set off at the same time, but at different places in a city. Everyone in the city sees them go off simultaneously, but they're at different locations.

• Spacetime diagrams can represent how time appears to stretch or compress based on your relative motion (Time dilation).
• Similarly, the length of objects appears to change based on your motion (Length contraction).

Real-world example

• Think of a moving train: for someone inside the train, a game of catch feels normal. But to someone outside, it looks as if everything inside is happening slower (time dilation).
• Also, from outside, the train might appear shorter than it is (length contraction).