CURRENT SCIENTIFIC THEORIES:
Current physics theory says that nothing can move backward in time, nor can anything interact in our reality if it travels faster than light. Physics says that time changes with velocity and gravitational fields. So, if a UFO took off from Earth at nearly the speed of light, and came back to Earth, passengers on the UFO would have barely aged, yet people on Earth would age normally. Therefore, it is possible that two identical twins could be different ages.
Recently it was announced by CERN that neutrinos were traveling faster than the speed of light in a vacuum, but they had faulty equipment. When they corrected their equipment, it showed that likely neutrinos traveled slower than the speed of light.
Neutrinos commonly do travel faster than light can travel through a media (matter). This is how they are detected. In matter, a neutrino gives off a cone of light (called Cherenkov Radiation), and that is detected with light sensors (in order to detect the neutrinos).
PREDICTIONS OF THE FUTURE:
In order for psychics to predict future events, information from the future would have to travel back to the past. Current theories of Physics seem to preclude that possibility. However, no one knows everything about science.
UFOS WOULD TAKE THOUSANDS OF YEARS TO REACH US:
To the home planet of the UFO, a long time would elapse as a spaceship travels to earth (if it is 10,000 light years from earth, and it is traveling at the speed of light, it would take 10,000 years to the people on the alien planet). However, to the alien in the spaceship, it would take very little time (because time dilates at high speeds).
WORMHOLES?
Many sci-fis on TV talk about wormholes (shortcuts in the fabric of spacetime that allow nearly instantaneous travel from one point in spacetime to another).
Maybe wormholes exist, or maybe not.
RADIO SIGNALS FROM OTHER WORLDS:
So far, we can't find any signals that prove the existence of life on other worlds.
Perhaps life is a lot rarer than we thought? DNA research shows that live evolved once and only once on Earth (unless some lifeforms died off). Every living thing on Earth is related.
It seems odd to most scientists that in the vastness of space, and among a myriad of planets (some Earthlike), there are not colonies of creatures.
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CONCLUSION:
Maybe life doesn't exist outside of Earth? It would take too long for an alien to get to Earth. No one can go back in time (as far as anyone knows).