I have ever heard a saying when I was a chid, that said a leaf was small,but each leaf was a whole world,which just liked our universe.You coun't count up all the particles inside. When I grew up, I was shocked by the philosophic thoughts contained in the saying. This reminds me that whether we do live in a leaf? or each of us is just a tiny part of a leaf? This thought can easily help answer the question which has been asking for over thousands of years: why the universe seems like endless. When we have enough food, we usually want todo other things, such as thinking about aliens, or does another you live in a parallel universes thinking about the same question as you? We try to find the answer, maybe the answer is as simple as the saying I just mentioned above. Mnay centuries ago,alot of people believed that the sky was round and the land was flat, never went to the edges of the land, you would fall of onto the dark.But when we read Bible, it says that God was sitting on the big cricle around the earth. Human being always just believe what they think are correct. This was called the dark under the lamp. Many people once claimed that they have witnessed aliens landed on earth. So,the problem is that do you believe the people who have seen aliens?