The Universe

Kaku mentions an interesting example in his book, Parallel Worlds. Here is the story:

Erwin Schrodinger proposed a physics experiment. He put a cat in a sealed box. There is also a poison bottle in it also. Before he opened the box, he proposed the cat was alive and dead at the same time.

"Whenever guests came over to his house, he would say: look at the moon. Does it suddenly spring into existence when a mouse looks at it? Einstein believed the answer was no. But in some sense, the answer might be yes." Parallel Worlds, pg158, Michio Kaku.

Keeping this in mind, next time when you are not looking at the moon, the moon might not exist at all...