Some opinions state the possibility of aliens come from outer space, from the earth, with a time machine (they can control the time), from another dimension. Here are some evidence and opinion.
Mayan crystal skull, produces sound like soft music, someone who can hear it can have a long life.
Mysterious mummy with a large triangular shaped skull found in Peru, believed to be aliens.
It is argued that the Egyptian and Mayan pyramids are the legacy of UFOs because of the similar building pyramids found on Mars with the same degree of latitude to the latitude degrees of pyramid on Earth. And difficult to explain how humans build those huge buildings, even though that time we have only very early human technology.
Stephen Hawking believes there could be a UFO and they need a source of energy and a big place, they can and will destroy human.
Some opinions expressed aliens are able to control space and time, so they do not use the transportation known to man. Transportation known to man is to move within a certain distance within a certain time, so speed is defined as the distance divided by time (v = s / t). While an alien can move from one place to another without moving in a certain distance in certain time, possibly by using wormhole. Therefore the distance between galaxies that reach millions and even billions of light years is not a problem for them.
Number of stars which are reaching 200 billion in our galaxy, reaching 3 thousand million billion across the sky, even NASA suggests more bigger number or infinite, there could be life on planets around those stars, same like on earth, they might have more advanced technology than humans.
Mysterious rays in the sky because of rocket launch that could be seen from a distance. Even it can past the horizon because of the atmosphere reflection.
Crops circle can be created by humans.
If such creatures do exist why they are so shy or arrogant and dont want to socialize normally to human? In our history, people of the earth or man would rather socialize than fight. Even between the two human parties who are fighting each other, sometime there is a cease-fire, and sometime they help each other who hit by disaster. Why are aliens, if they do exist, do not do the same thing, ie get along with humans?
According to the holly books that are believed by many people, Adam & Eve were only sent and lived on earth. Humans are highest degree creatures because they have capability to think, in other words human is the only smart animal that can have culture. Some other animals are smart enough, like: bees are able to make a house, but model of bee house has never changed. Chimpanzees, orangutans can use simple tools such as seed-breaking tool. But animals have no ability to develop a more complex technology.
Whatever conclusion we have made, the universe is given to man to be explored, but of course not to destroy it.