Another very important concept in physics is relativity. Relativity is when you measure or compare something based on something else’s motion or appearance. In short, it is just the way you look at things. Sometimes, it is easier to understand a physics concept if you examine in a non-physics way. So here’s my explanation…

Take a look at this Goldfish cracker.

It seems tiny compared to my hand.

But compared to an ant, it is enormous!
That is using the theory of relativity. Compared to a human, a cracker is very small, but compared to a tiny insect, it is massive!
For a physics example, we could use a parked car. If we looked at one, it would seem like it has no velocity, but it is actually zooming with an incredibly high velocity through space, because it is on Earth, and that is what our planet is doing right now.

Another example of relativity is have you ever driven down the street and a train was moving right beside you? To your view it looks like you are stopped, and the train is moving at a very low velocity. But to a person sitting on a bench it looks like you are moving, but the train is just moving a little faster. When it comes to relativity, there is no right answer. In physics, constant velocity is relative because you don't feel like you are moving. You might look like you are moving when you pass something, but you might look like you are stopped when something is traveling faster than you. If a cop pulls you over and tells you that you were speeding, you can technically tell him you weren't, using the laws of physics and relativity. Compared to the ground you were speeding, but compared to the earth you were not. Although, one thing in physics that is not relative is acceleration. You can feel yourself accelerating, so it can't be compared to anything. You can say you are accelerating faster or slower, but you are either accelerating or you are not.