Originally Posted by Rabbit

I assume you mean the speed of light.

Yes, and it would take tens of thousands of years to reach the nearest star. For an alien to come here, either in person or by robot proxy, in our lifetime as a direct response to receiving a signal from Earth, his craft would have to travel at a very large fraction of lightspeed, thus his technology would have to be in advance of our own. If his technology were in advance of our own, he would have been transmitting signals longer than we have and we would therefore have received his signal before he received ours. We haven't received any signals, ergo, there are no sufficiently advanced aliens within 100 light years, that being roughly the amount of time we have been transmitting.

I wouldn't even be that optimistic. If I saw a "visitor from outer space", I'd first want to know why he chose, out of all the vastness of space, to come to this locality, because, given that the galaxy is at least 100,000 light years across and we have been advertising our presence for only 100 years and given also that we are capable of imminent self-destruction, our presence represents not just a needle in the haystack of space, but also of time. A random alien, from any place or time in the galaxy, would have a vanishingly small chance of finding us even if he knew precisely where to look. And for him to be able to actually land here presupposes at the very least that his body can tolerate Earth gravity and why should it?

I'd be inclined to ask the alien, who will no doubt speak suspiciously good English with an American accent, who did his make up, beep beep!