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.
Admittedly, it would take industrial-grade chutzpah and a massive dose of malevolence for anyone to bulldoze the spot where Neil Armstrong stepped off the Eagle lander. But even innocent visits could be damaging.
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.
Are we the only members of the Galaxy that can actually understand what a galaxy is? Could Homo sapiens really be the pinnacle of Creation - the cleverest critters in the cosmos? If we learn the answer is 'no,' that would affect our philosophies forever.
The stars look the same from night to night. Nebulae and galaxies are dully immutable, maintaining the same overall appearance for thousands or millions of years. Indeed, only the sun, moon and planets - together with the occasional comet, asteroid or meteor - seem dynamic.
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.
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.
It's always a tough call deciding whether, as a scientist, you should argue publicly with the creationists. It's a dilemma that I encounter frequently in another subject area: Does it make sense to bandy words with someone from the UFO community?
The math is dead simple: it seems that the frequency of planets able to support life is roughly one percent. In other words, a billion or more such worlds exist in our galaxy alone. That's a lot of acreage, and it takes industrial-strength credulity to believe it's all bleakly barren.
Here's a news flash: scientists can be wrong. That's no big deal (unless the scientist is you), since research is self-correcting. Consequently, most errors by scientists become historical curiosities, with little long-term importance.
Faith is a personal matter, and should never be a cudgel to stifle inquiry. We tried that approach about 1,200 years ago. The experiment was called the Dark Ages.
You may not see massive UFO exhibits at your local science museum, but there's no dearth of saucer stories infesting my email. Every day, I receive several reports of alien sightings, extraterrestrial plans for Earth, and agitated screeds about the reluctance of scientists to take the whole subject seriously.
The overwhelming bulk of the cosmos is deathly quiet. But here and there - on worlds where matter is thick and conditions are right - noises are commonplace. And in some cases, these noisy worlds may ring with the sounds of life - the bleats and bellows of creatures we have never seen, but may someday discover.
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.
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.
The central region of the Milky Way, known as the bulge, is stuffed with literally tens of billions of stars. And most of these are old - considerably older than our Sun or its neighbors - because this part of the galaxy formed first. Consequently, bulge stars are generally deficient in heavy elements.
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.
I still remember my dismay in the summer of 2007 when - for the first time in the history of planet Earth - America's share of auto production dropped below 50 percent.
Is E.T. out there? Well, I work at the SETI Institute. That's almost my name. SETI: Search for Extraterrestrial Intelligence. In other words, I look for aliens, and when I tell people that at a cocktail party, they usually look at me with a mildly incredulous look on their face. I try to keep my own face somewhat dispassionate.
Plate tectonics is not all havoc and destruction. The slow movement of continents and ocean floors recycles carbon dioxide dissolved in the oceans back into the atmosphere. Without this slow speed carbon cycle, Earth's temperatures would cool dozens of degrees below your comfort zone.