Schrödinger's Cat

A principle of the quantum theory named "superposition" states that if we don't know what the state of an object is then as long as we don't check, the object is actually in all possible states simultaneously. 

Erwin Schrodinger proposed a theoretical experiment in which a cat was put in a box with a bottle of poison and a tiny amount of radioactive substance and a Gieger counter (a device for detecting radiation). The radioactive material had a 50:50 chance of decaying. The Gieger counter was designed so that when it sensed the decay of radioactive material, it triggered a hammer which was poised to break the poison bottle and kill the cat. But as long as the box stays closed, we wouldn't know whether this has happened or not. So according to quantum law and superposition of states, the cat is both  alive and dead at the same time.

But if we take a look in the box, the superposition ceases and the cat is either dead or alive. So as the observation affects the outcome, the outcome doesn't exist until the observation is made.