system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Einstein said “If you can't explain it to a six year old, you don't understand it yourself.” How would he explain special relativity?
gpt
Einstein used  trains extensively but for modern kids cars are more appropriate. Here we go.

Ok so you know haw when you are in the car driving down the highway and you arn't speeding up or slowing down or turning if you don't look outside its kind of like the car isn't moving at all. Sure when you turn or change speed you get pushed into the seat or the seat belt but when cruising you could be parked. So when you look out of the window its a little like the world is moving not you.

Now on the highway there are other cars on the road and they can be going in opposite directions so the cars going the same way as you can seem to move slowly while traffic in the other lane is very fast. And the thing that's cool is that feeling of standing still while the world goes by happens to everybody so if you compared what the different cars saw they would all disagree about how fast all the cars where going. 

But here is the amazing thing if you can see how fast the lights from the headlights where going everyone in every car would agree on the same speed for everyone's headlights no matter how fast or what direction they were going. And the number they came up with would be the same number that anyone anywhere in the the world would come up with when they measured light speed.