1. Quantum Physics
It is not very likely that a ranger and four hobbits will come knocking on your door. But as far as electrons are concerned, likely is all you are going to get in this world.
Imagine them in front of your door!
Strider – nobly dishevelled, looking forward to a pint.
Four hobbits – cheerfully hungry. Frodo, thoughtful. Sam, rather shy. Pippin, with a birthday-trick in his pocket. Merry, ready to give you a song.
It is not very likely that they are outside right now.
But if someone knocks on your door in a minute, are you going to open it?