Disasters happen. We still have no way to eliminate earthquakes, wildfires, hurricanes, floods or droughts. We cope as best we can by fortifying ourselves against danger with building codes and levees, and by setting aside money to clean up afterwards.
Virtually any pointed edifice is considered a candidate for alien engineering. After all, how could the Egyptians or Mayans have possibly stacked up stone blocks into pyramids?
When I was a kid, which was just after Edison invented moving pictures, there were films that involved aliens coming to Earth for bad purposes.
The Earth has been lawned with life for something over 3.5 billion years. That's a span of time great enough to encompass some honest-to-goodness catastrophe. For example, 700 million years ago, Earth underwent a planet-wide deep freeze, with ice covering the oceans from the poles to the equator.
In days gone by, scientists would speak solemnly about our solar system's 'habitable zone' - a theoretical region extending from Venus to Mars, but perhaps not encompassing either, where a planet would be the right temperature to have liquid water on its surface.
Estimates are that at least 70 per cent of all stars are accompanied by planets, and since the latter can occur in systems rather than as individuals (think of our own solar system), the number of planets in the Milky Way galaxy is of order one trillion.
Television is ephemeral, a fact that some will find reassuring. But earthlings will continue to pump the kilowatts into the ether. And eventually, when those signals have washed over a few hundred thousand star systems, someone may notice.
Explorers tend to be the aggressive types - why else would they risk scurvy, mutiny and other bad things to go out there? So, you could say that any aliens that are actually moving and interested in going somewhere are likely to be more aggressive. But who knows?
The total funding of SETI (the Search for Extraterrestrial Intelligence) in the U.S. is 0.0003 percent of the tax monies spent on health and human services. And it's not even tax money. The SETI Institute's hunt for signals is funded by donations.
The thing to keep in mind is that we're still in the very early days when it comes to the search for extraterrestrial intelligence. Saying there's a silence is a bit like if Columbus, looking to discover a new continent, only sailed 10 miles off the coast of Spain before turning back to say, 'Nothing out there!'
Some pundits have proposed that the aliens have come here to breed with us. Apparently, too much bike riding or something similar has rendered them incapable of reproducing within their own species. But do extraterrestrial infants toddle through your neighborhood?
Clearly, unless thinking beings inevitably wipe themselves out soon after developing technology, extraterrestrial intelligence could often be millions or billions of years in advance of us. We're the galaxy's noodling newbies.
In a movie, it's often important to have aliens whose gestures and facial expressions can be 'read' by humans. And in the days before sophisticated computer animation, most extraterrestrial bit players were guys in rubber suits. Such practical considerations forced Hollywood's hand when it came to aliens - they look like us for good reasons.
Hollywood usually guesses that extraterrestrials would only be interested in one of three things: (1) They want to breed with us, because their own reproductive machinery is on the blink; (2) They want Earth's resources; or (3) They want the Earth. All of it.
'E.T.' was far-fetched. 'E.T.' was this wimpy-looking kid that came to Earth to pick some plants, but he came from the Andromeda Galaxy to do that.
Neil Armstrong was no Christopher Columbus. In most respects, he was better. Unlike the famous fifteenth century seafarer, Armstrong knew where he landed. He also spent his time in public service, not in jail, and his passing was marked by world-wide encomiums. He ended his days as a celebrated explorer rather than a royal inconvenience.
Everything you see is filtered through your visual system (imperfect) and your brain (also imperfect, despite what your mom told you). Witness testimony is the worst kind of evidence in science.
Star Trek's genial premise is that the cosmos is flush with intelligent species, and our descendants will interact with them face-to-face, thanks to warp drive and some winsome space cadets.
In archaeology, context is the basis of many discoveries that are imputed to the deliberate workings of intelligence. If I find a rock chipped in such a way as to give it a sharp edge, and the discovery is made in a cave, I am seduced into ascribing this to tool use by distant, fetid and furry ancestors.
When was the last time you bought an American-made radio or television? If you're Gen X or younger, the answer is 'never.' Does the label on that shirt or skirt you're wearing say 'Made in the U.S.A.'? If so, you probably got it at Goodwill, or maybe at a Smithsonian garage sale.