(Skip to paragraph 4 if you have ADD.)(1) I think there is no such thing as aliens. Follow me here- I don't write often, and when I do, it's usually something worth thinking about.
(2) See, Einstein was the man. He used math to predict the behavior of physics before we had the equipment today to test it (by the way, we've tested almost everything he's predicted, and he's been 100% correct). He knew that time runs slower near big physical objects. That means your watch ticks a little bit slower when you're near my bicep as compared to your bicep (granted the difference cannot be detected by the human eye), but atomic clocks have proven otherwise.
(3) Following me? OK, light is the fastest thing in the universe. It travels at 186,282 miles per second. I didn't even look that up, mind you. If anything travels faster than that, it disintegrates. So nothing can travel faster than that. You can go 186,281 mps, but that's about it. Astronomers have tracked many of our nearby stars with planets with no evidence of life. That means that the nearest possible star with planets that are habitable to life is at least 20 light years away. A light year means the distance you travel if you moved at the speed of light FOR A YEAR. Yeah, so if you traveled at 186,282 miles PER SECOND, a light year is what you cover IN A YEAR. So no, nothing/no one can ever, EVER visit another planet with life. It's too far. I don't care how fast your ship is, I don't care how long you live.
(4) Which is why there are no such things as aliens (that's been to Earth). However, you can't discount, at all, any of the testimonies from Hicksville, USA on having oddball visitors. Ever noticed that most of their stories describe the same looking creatures? Big head, small body, big brain, small eyes, no muscle, all white? They don't talk, do they? That's why I think they aren't aliens at all. I think they're humans, but from the future. You've already read this far. May as well continue. You can't travel into the future. Sorry, Marty.
(5) It's not set, but you CAN travel into the past. I'm not lying when I say this, but MIT has proven this a few years back. They've put atomic clocks near high-massed objects and recorded differences in time passed there and in open areas. If you project these stats out, with enough gravity- you can literally move a physical object back in time. So in the future, as humans will no longer need to hunt, our bodies evolve- we get smarter- we rely on our eyes and brains more than our speed and agility; hence, the larger eyes, and brain, the smaller bodies. Shit, I took vitamins the other day that had more nutritional value than a regular meal.
(6) Imagine we're hundreds of years in the future and time travel was available. Wouldn't you think we'd go back in time to study our past? Our evolution? And do a bunch of tests on living subjects? Notice no one dies or really gets hurt off "abductions".
(7) So the next time Sam Cassell comes into your home and sticks some instruments up your butt, don't be alarmed.