ELI5: Explain Like I'm 5

Nephroid caustic

Have you ever seen the shape of a heart? It is sort of like a round shape with a point on the bottom. Now imagine a ball that is rolling around the outside of the heart shape. As it rolls, it leaves a trail behind it. This trail is called a nephroid caustic.

A nephroid caustic is a really cool mathematical shape that is made by shining a light through a heart-shaped object and seeing what happens to the light as it bounces off the object. The shape of the nephroid caustic is formed by the way the light bends and reflects off the surface of the heart-shaped object.

You might wonder why anyone would care about a nephroid caustic. Well, for one thing, it helps scientists and mathematicians understand how light moves and behaves. Plus, the shape is really beautiful and interesting to look at!

So next time you see a heart shape, try to imagine the ball rolling around it and leaving behind a cool-looking trail. That's what a nephroid caustic is all about!