Paradoxes are simple problems that contradict themselves. Paradoxes are very hard to solve but with the help of quantum theory many of them can be solved. Here is an example of a simple but very confusing paradox. It is called the Lying Paradox. The Picture below shows the Lying Paradox.

Imagine a person says to you that he always lies. Is he telling the truth or lying to you? He cannot be telling the truth because he would be lying. He cannot be lying, as he would be telling the truth. A very confusing problem. The greatest paradox thought up was the Grandfather Paradox. The paradox begins with you building a time machine. You decide to take a trip back in time. You set off on your journey and when the time machine arrives at its destination time it accidentally lands on your grandfather. Where you born is the question the paradox asks?

You could not be born if your grandfather was killed and if you were not born then he will not be killed. This is a very hard problem to solve but thanks to quantum theory, the solution is easy. When you travel back in time the universe splits into two parallel universes. The universe you came from and the universe were you existed in the past. The reason the universe splits in two is because that just existing in the past will change the future. So the choices you make while you are in the past have to be carried out in a parallel universe. When your time machine materialised on top of your grandfather as a boy, a new universe is created where your were never born and did not invent the time machine. You still exist, as you are from the universe parallel to the one where you were not born. It sounds confusing but the idea makes sense.