I believe in the existence of aliens. The scope of universe is beyond our imagination and the complete knowledge about everything that lies out there is still not know to us. There are still thousands of mysteries that are yet to be unraveled.
There is every possibility that there Are planets similar to earth with inhabitants on them, in some far away galaxy millions or trillions of light years away from us. They could be similar or probably ahead of us in terms of technological advantage.
Proof of their existence would be something very offbeat and different than what we are used, something supernatural probably have been found time and again, and their cause for being their has not been able to be expalined by the brightest of our scientific geniuses. The occurrence of crop circles in definite and unusual patterns have been experienced many times, is one example of an unexplained phenomenon.
Scientists saw unusual phenomena in Odessa catacombs. They found bones of fossilized ostriches, camels and hyenas in the burrow which was a cave in ancient times. The bones were processed one million year ago with some metal tools.
There was no contemporary human being one million years ago, the Stone Age had not even started at that time. What kind of metal tools could it be? There are round and square holes and grooves in the bones, some of the bones are polished.
Steel rectangle 67�67�47 millimeters in size and 785 grams in weight was found in by Austrian physician Mr. Gurlt in the layer of coal the tertiary period. This item was made by human beings.
Balls of perfect geometry curved from granite were found in South America. The balls were located at the tops of correct polygons. It is hard to imagine that people knew Geometry several thousand years ago.
Read the link on the crop circles carefully and you will know what I mean.