Imagine a cat, a black cat. Walking alone in the dark. With silence as his company. The black cat is crawling towards a box. A black box. He smells something, some fishy box, he thinks. He can smell tuna fish inside that black box, but the box itself is rather interesting. It is a simple box, but he feels danger.
He use his paws to touch that box. One touch, the box doesn’t budge, second touch, it is stay still. Curios, he thinks. If he knew that curiosity kills cat, he won’t do what he about to do next. He enter the box, slowly, cautiously.
He can smell his prize, a tuna fish. But then an unexpected turn of event come. The box slam shut. He’s trapped inside!
Panic, he crawl the wall in the box, but the box stay intact. Now, I’m dead, the cat thinks. And then he see it. A light in the corner of the box, glowing light. If he is a physicist then he will know that that is a radioactive substance that have 50% chance to deteriorate an emitting radioactive rays that will kill him. If he is a physicist then he will know that he is in a quantum superposition. He is both alive and dead at that time.
But he don’t know. He just touch that substance.
Now, is that cat alive?
Let us open that box, shall we?