Modern Cosmology

First, one must grant the premise that by sheer laws of probability, many advanced alien civilizations exist throughout the universe. Professor Hawking’s trepidation about the wisdom of overtly seeking contact with them is well-founded. We have no way of discerning the intent of alien visitors except after-the-fact. The Darwinian concept of natural selection supports the assumption that aliens visiting newly discovered planets, like Earth, would place their own interests above those of unsophisticated indigenous residents.

If the rate of evolution observed on Earth from the first records of single-celled organisms to the current state of hominid achievement is any indication, one can expect that alien civilizations will achieve a similar level of technological development in 5 or 6 billion years. Our best estimates of the age of the universe range in excess of 13 billion years. Therefore, another statistical premise is that there will be lots of more advanced alien civilizations in the older, more distant reaches of the universe. All of this bodes ill for the outcome of any encounter with space aliens.

However, the one bright spot in this ominous conclusion are the constraints that light, time, and space place on both matter and energy (that means both us and our potential alien invaders). It’s no coincidence that every science fiction narrative of interstellar travel includes some currently undiscovered system that allows travel many times faster than the speed of light. In real science, however, Einstein’s relativity theories seem to have held up on one point: no particle or wave exceeds the speed of light. First, this means that the wave front of Earth’s first electromagnetic transmissions to the rest of the universe is barely more than 100 light-years distant. It could well be tens of millions of years before our unintended radio and television calling cards are noticed by the first avaricious aliens. Then, racing to Earth at near-light speed, it will take our would-be exploiters tens of millions more years to turn up on our doorstep. Unless they have very long life-spans, that would require a generational space ship with little prospect of returning to their home planet with whatever booty that they considered valuable enough to undertake a long and expensive expedition.

The only motivation for alien space plunders to visit Earth then, as Hawking suggested, would be to send out one-way colonists to expand the size and distribution of their race. Given sufficient time, that scenario is likely to play out multiple times. This is not so different, strange to say, from human’s own aspirations for space travel. Earth’s only hope will be that the laws of physics apply throughout the universe and place constraints on the types and power of possible weaponry that could be used against humans…and that by the time the invaders arrive, humans themselves will have discovered and deployed similar defense systems that would allow Earth to hold its own. Speculation about the future is by definition, fiction, but it sounds as if our most imaginative science fiction may turn out to be closer to the truth than we would like.

via Journal of Cosmology.