Distance and Time

Suppose there are extraterrestrial civilizations out there. How to we make contact with them (assuming that we consider that to be desirable)? We could go to see them or they could come to see us. But if we consider that possibility, we are immediately confronted by two rather staggering barriers: the speed limit imposed by light, and the enormous distances between the stars.

Enormous Distances and a Cosmic Speed Limit

The distances between stars are so large compared with the size of planetary systems that even scientists trained to think in terms of very large numbers find it difficult to comprehend. We do not have the technology, nor can we conceive of the technology in the near term future, to accelerate a spacecraft to near light velocity. But even if we could, only the few nearest stars would be reachable in a normal human lifetime (as measured on Earth). Stars beyond that would presumably require setting sail from Earth with a colony aboard a spacecraft, never to return, with only the hope that a distant generation of the colony would be alive when the target star finally was reached.

Not with Present Technology or Science

Thus, barring technology breakthroughs that are presently beyond what we can even conceive, direct travel to the stars is not practical. Of course, if humankind survives for a thousand or a million or a billion years beyond today, who can say what technologies might be invented that will make these words seem quaint. But based on the technology that we can project today, we must rule out travel to the stars in the foreseeable future.