rationalskepticism.org

When interested in answering questions of plausible future technologies, we obviously can only reasonably appeal to what is known of physical law. In the not-so-distant past, the quantum computer was only a kind of mathematical abstraction, but of late developments in laboratories have been making their way into the popular science press. In the area of space exploration, the situation appears to have moved in an opposite kind of direction as assumptions that space flight could be done over long distances have run up against a harder analysis of what this really would entail. It has even become a kind of dogma that space flight is so limited theoretically that life is always essentially stuck in its neighborhood of origin. This is in contrast to prior confusion over why if life should be relatively ubiquitous, or even not so ubiquitous, we should now find ourselves with no reliable evidence that it exists anywhere other than on Earth. The presumed fact that intelligent life must almost certainly by now have had the opportunity to at least contact us from elsewhere butting up against the absence of evidence is called the Fermi Paradox, and a reasonable article on the subject can be found at wikipedia, though it doesn't handle certain things like the topic of this thread at all well. I leave the floor open for discussion with only a note that there was written last year an article dealing with a very very extreme type of plausible engineering involving the generation of artificial black holes being used, when 'tethered' to the back of a vehicle, for propulsion via Hawking radiation. The fact that such an article was written is an indication, and the authors say as much, that the options for space flight appear to be very limited. [I will provide a link to the article as soon as possible if someone else doesn't beat me to it.]

Note: Hawking radiation is a generally accepted, but still unobserved (and unobservable without small black holes), part of theoretical physics. Black holes, though commonly thought of as sinks that gobble up everything including light that comes too close, should theoretically evaporate according to a precise pace that speeds up as they get smaller. The article in question deals with the ideal size for the authors' proposal.