Invariant interval

Imagine you are standing in one place and you see a car moving past you. You might notice that the car looks smaller as it gets farther away from you, and it looks bigger as it gets closer to you. But there is something that doesn't change no matter how far away the car is or how fast it's moving. That thing is the time it takes for the car to pass you.

That time is what we call an invariant interval. It's like a special kind of clock that always measures the same amount of time no matter what else is happening. In physics, we use the concept of an invariant interval to talk about the distance between two events in space and time.

Let's say that you see a flash of lightning in the sky and then you hear the sound of thunder. The time between the flash of lightning and the sound of thunder is an invariant interval. Even if someone else is standing in a different spot, they will also measure the same amount of time between the flash of lightning and the sound of thunder.

This is very important because it helps us understand how space and time work together. The fact that some things in the universe always stay the same, no matter what else is happening, tells us that there are some rules that apply to everything. Invariant intervals help us make sense of the world around us and the way it works.