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?
— Seth Shostak
Very few societies on Earth developed science as we know it today. On the other hand, the number is not zero - the Greeks, the Chinese, and the Maya did, among others. Once invented, science proved so useful that it spread like mold on a petri dish.
The Moon stabilizes Earth's obliquity. Well, almost. The tilt actually varies between 22 and 24.5 degrees - and the variation is enough to induce such environmental inconveniences as the occasional ice age. Without the Moon, it might be much worse.
The Moon is a ball of left-over debris from a cosmic collision that took place more than four billion years ago. A Mars-sized asteroid - one of the countless planetesimals that were frantically churning our solar system into existence - hit the infant Earth, bequeathing it a very large natural satellite.
'Battleship' is not a film that Francois Truffaut would have made. Nor would any of those other namby-pamby European directors. Nope, this picture eschews that Continental obsession with small stories, set in quaint towns filled with pockmarked folk doing their banal things.
Thanks to the fact that the Earth isn't a perfect sphere, and invoking a bunch of Newtonian physics, you can deduce that our planet wobbles, too, taking roughly 26,000 years to trace out a small circle on the sky, a phenomenon known as precession.
The strongest signals leaking off our planet are radar transmissions, not television or radio. The most powerful radars, such as the one mounted on the Arecibo telescope (used to study the ionosphere and map asteroids) could be detected with a similarly sized antenna at a distance of nearly 1,000 light-years.
The next time you check your moves in the mirror and reflect on how special you are, consider that somewhere in this universe or in another parallel universe, your double might be doing the same. This would be the ultimate Copernican Revolution. Not only are we not special, we could be infinitely ordinary.
Astronomers still can't decide what the shape of our universe is. Is it closed and finite, which is to say, is there a countable tally of all the galaxies that exist, even beyond the ones we can see? Or is it infinite? The latter possibility is still on the table.
Scientists - who prefer explanations subject to laboratory tests - figure that everything we see today was as inevitable as wrinkles, once the Big Bang established physics. Stars and planets were cooked up as huge clouds of matter collapsed and coalesced.
A practical way to travel between the stars is a must-have for space opera, and a sine qua non for our frequently vaunted future as a galactic society.
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.
Are two eyes, four appendages and an upright posture really essential for any creature that can ace the galactic SAT's? Maybe not. In fact, I'd venture that any aliens we ever detect or (less likely) encounter will look quite different than this self-referential stereotype.
The space elevator's not just another competitive technology, promoted by people who simply like the idea of diminishing the luster of the thrusters. It would open wide the doors to space.
It seems that 'rocket scientist' is a job category that's here for the long haul, like 'mortician.' But all this activity masks an important point: rockets are not a terribly efficient way to lift things into space.
The most attractive habitats for synthetic sentience might be the vicinities of exceptional sources of energy - for example black holes, or even the neighbourhoods of large stars, which routinely boil off the energy of ten thousand suns. These are the destinations they may seek.
Three-fourths of the universe is hydrogen, and oxygen is incredibly abundant, too. So H2O is something you can find nearly everywhere.
In general, when moviemakers talk to scientists, they usually see them as a resource to solve particular technical problems or script problems for them. So, something like: what sort of weaponry would aliens be able to wield?
We haven't yet found a speck of evidence for biology on another world, so we have no objective way to judge whether life is a onetime fluke or a near-inevitable phenomenon.
Even if the Moon didn't exist - even if it had been vaporized billions of years ago by cantankerous Klingons - there would still be (somewhat lower) tides raised by the Sun. For creatures dependent on the oceans' ebb and flow, life could go on.
About the only things that are unique to Earth are our biota and our culture. If aliens ever come here, they'd most likely be either biologists or music fans. Neither one has much reason to antagonize our armed forces.
Frankly, I'll believe in horoscopes the day I can describe my personality to an astrologer and they tell me what date I was born.
Note to academics: Aristarchus' track record of astronomical research would probably have guaranteed him tenure somewhere, if tenure had been invented. His stack of reprints included measuring the distances of the Moon and Sun.
Lamentably, alien audiences may be frustrated by the switch to digital television. That's because the transmitter power for DTV is fairly evenly spread across the spectrum. The spikiness is gone, and from afar, the attention-grabbing squeals of analog television's carriers have been replaced by DTV's smooth, low hiss.
The limitless content of our universe might be only one instance of a large (and possibly infinite) number of other universes.
It's worth noting that invoking God as the entity who set our universe in motion isn't contradicted by the data. Of course, scientists would say the supreme being hypothesis is faith, and outside the realm of science - that it's not amenable to experiment. But we currently have the same problem with the notion of parallel universes.
Consider: The human genome consists of about 3.3 billion base pairs. Since there are only four types of pair, that amounts to 0.8 gigabytes of information, or about what you can fit on a CD. With a microwave radio transmitter, you could beam that amount of information into space in a few minutes, and have it travel to anyone at light speed.
Every day, the temperature of Sol's surface increases by five billionths of a degree, a change of no consequence for thousands of millennia to come. But a few hundred million years from now, barring a fix by our descendants, this relentless heating will substantially change Earth's biosphere in ways that might not be survivable for us.
Forecasting Armageddon has become trendy of late, with a great deal of attention being given to an interpretation of the Mayan Calendar suggesting that Mother Earth is destined for doom in December of 2012.
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.
A factory that can turn carbon nanotubes into a sheet a yard wide and long enough to stretch one-fourth of the way to the moon is not something you'll find at your local industrial park. That's the show-stopper for the space elevator. The ribbon.
Despite tantalizing suggestions of fossilized microbes in meteorites, puzzling and possibly biogenic methane gas in the martian atmosphere, and a long-standing controversy over the Viking lander experiments of nearly 40 years ago, there's still no Exhibit A that points unequivocally to biology in our own back yard.
Our computers double in capability on time scales of only a few years. It's hardly outrageous to believe that we will successfully develop thinking machines within a handful of decades, or at most a century or two. If that happens, these artificial sentients will quickly leave us behind.
The fact that we can't easily foresee clues that would betray an intelligence a million millennia farther down the road suggests that we're like ants trying to discover humans. Ask yourself: Would ants ever recognize houses, cars, or fire hydrants as the work of advanced biology?
It seems obvious that if a species has the brainpower for speech, along with the sort of appendages that can manipulate a pair of pliers, it will eventually blunder into science, technology, and radio.
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.
There's no doubt that the Moon is more than a handy night light and a hair restorer for werewolves. It's responsible for the substantial amplitude of earthly ocean tides. These are of obvious influence if you're a geoduck, a type of clam that people dig up at low tide.
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.
The bottom line is that the position of the Sun relative to the stars slowly changes for any given date, and over the course of 26,000 years, it can easily slide between constellations. So you may think you're a Pisces, but you're actually an Aquarius.
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.
Ever since the Second World War, television signals (as well as FM radio and radar) have served as Homo sapiens' emissaries into deep space. High-frequency, high-power broadcasts have filled an Earth-centered bubble more than 60 light-years in radius with signals.
If the cosmos isn't finite, then far, far away, floating duplicates of your brain - with all its experiences, thoughts, and emotions - are occasionally (and temporarily) thrown together by the random combining of atoms. Such 'Boltzmann brains,' as they're called, are a disturbing consequence of an unlimited universe.
The split between religion and science is relatively new. Isaac Newton, who first worked out the laws by which gravity held the planets and even the stars in their traces, was sufficiently impressed by the scale and regularity of the universe to ascribe it all to God.
It's easy to reckon that the oomph to hurl even a Smart Car-size spacecraft to another star at, say, 20 percent the speed of light (and land it when it arrives) is the energy contained in 50 billion gallons of gasoline. The tank's not big enough.
Today's voguish threats, including climate change, population growth, massive war, and resource depletion, are all amenable to a fix if we act prudently. And even if we don't, these problems are incapable of obliterating all of humanity, let alone destroying the Earth. No, the real End of Days will happen slowly, as the Sun ages.
Imagine if the dinosaurs had tried picturing the rulers of their planet 100 million years hence. They'd undoubtedly envision these creatures as... dinosaurs! Conceiving of aliens as polished versions of ourselves is appealing, but unconvincing.
I you look at the drawings of aliens made by people who believe that Earth is under saucer attack, you'll quickly note that most of these invaders fit the Tinseltown mold. But you have to admit: the grays are highly anthropomorphic.
What's a space elevator? Simply described, it's a thin ribbon, about 3 feet wide and 60 thousand miles long, stretching upwards from the surface of the Earth. The lower end is bolted to a heavy anchor (think of an oil drilling platform), and the top is capped with a counterweight.
While human space travel is daunting, machines - with their indefinitely long lifetimes - could travel the galaxy. It might make little difference to them that bridging the distance from one star to the next could take hundreds of thousands of years or more.
One of the jovian moons, Europa, is coated with twice as much liquid water as is sloshing around our planet.
