Even if we assumed life existed somewhere else in the universe, a visit by extraterrestrials, to Earth, such as is claimed in UFO reports, seems completely impracticable, if not impossible. The distances (and therefore the likely travel times) are unimaginably vast.
The closest star to Earth, Proxima Centuri (Alpha Centuri C), is 40.7 trillion kilometers (approximately 25 trillion (25,000,000,000,000,000) miles) away. The Apollo flights took three days to get to the moon. At the same speed, one would need 870,000 years to get to this nearest star. Of course, one could accelerate (particularly unmanned) probes to a greater speed.
To be continued...
Sign of Design: One reason put forward for saying that Genesis is "non-scientific" is that the account is brief. But since when does brevity equal inaccuracy?