Gravity train

Okay kiddo, do you know what gravity is? It's what makes things fall down when you drop them, right? Well, a gravity train is kind of like a really long slide that goes through a tunnel.

Imagine you're on a big hill and you have a ball. If you drop the ball, it will roll down the hill because of gravity. Now imagine if you have a really long track that goes down through the hill, and the ball is on a train that travels on that track. The train will also roll down the hill because of gravity, but it will do it much faster than the ball because it has more weight and momentum.

So, a gravity train is a train that uses gravity to move through a tunnel. The train doesn't need to use fuel or electricity to move, it just relies on gravity to do all the work. It's a really cool idea because it's very energy-efficient and doesn't create any pollution.

Some people even think that gravity trains could be used in the future to transport people and goods around the world. But for now, we're still figuring out how to build them and make them safe.