ELI5: Explain Like I'm 5

Autocollimation

Autocollimation is like playing catch with your own reflection. You know when you throw a ball to your friend and they throw it back to you? Well, imagine if there was a magic mirror that could throw the ball back to you automatically! That's what autocollimation does.

But autocollimation isn't just about playing catch. It's used in science and engineering to measure things very precisely. Scientists and engineers use fancy machines called autocollimators to help them do this.

Autocollimators work like this: there's a little light inside the machine that shines onto a mirror. The mirror reflects the light back into the machine, and the machine measures how the light waves are bouncing around inside. This tells the machine if the mirror is perfectly straight or if it's a little bit crooked.

So, if you were playing catch with an autocollimator, it would be like throwing a ball to a magic mirror that can tell you exactly how straight or crooked you threw it! Cool, huh?