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Originally Posted by Moonliner

My thought is that any alien visiting earth would be the interstellar equivalent of an Anthropologist. Grad students doing field studies and the like. As such they would certainly not hover over the white house and toot their horn. They would set up blinds and study us in our natural environment perhaps snatching a few specimens from deserted country roads or on Friday nights when they’ve had a bit too much space-juice turning the robo-surgeon loose to carve their initials on some local bovine livestock. As long as we don't have anything they need (like dilithium or Ben and Jerries) we should be left in peace to eventually blow ourselves up.

Originally Posted by Goulish Delight

There's no supposedly about it. Time dilation (the slowing down of time for an object traveling at speed relative to an object at rest) is a central, and experimentally confirmed, component of Einstein's theory of relativity. It's what gives rise to the famed twim paradox.

It does pose some interesting issues. For example, let's assume that we satisfy ourselves with near-light speed travel. An astronaut could conceivably at those speeds reach another solar system 10 lightyears away (there are several that distance and closer). The good news: At those speeds, from the frame of reference of said astronaut, the distance will actually shrink (which is another way of expressing time dialation, I'm really still talking about the same effect), so it should take less than 10 years. The bad news...if it takes 8 years from the astronaut's perspective (16 total for the round trip), when he comes back, it will have been the full 20 years (okay, slightly longer if he's just under the speed of light).

As the distance increases, so does the gap. So there's a built in advantage and a built in disadvantage. The advantage is that the distances would be slightly more reachable than they'd appear from our perspective, allowing an astronaut to cross them in a fraction of the time that the measured distance might indicate. The disadvantage is that by the time the astronaut gets back, time on earth will have passed him by. He may have aged a couple years, while full generations have gone by at home.

Uh huh. My thoughts exactly. But here is the thing -- IT'S NEVER GOING TO HAPPEN!