Seth Shostak

If you still believe that aliens would travel hundreds of light years to carve temporary graffiti in our wheat, then your imagination is one of the seven wonders of the world, and should be bronzed.

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.

We can never prove that we're alone in the universe. But the Allen Telescope Array could prove that we're not.

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.

'Dating Game' wasn't social commentary, political analysis, Shakespearean-level drama or even blunt-force comedy. It was just the televised equivalent of meeting someone at a bar. But it appealed to our most basic Darwinian instinct: selecting a good mate. You can't go wrong when a show's premise is hard-wired into human DNA.

Ever since the infamous quiz show scandals of the 1950s, the feds had insisted that TV game shows be honest - or that at least they didn't cheat. So as a 'Dating Game' bachelor, I didn't know what I was going to be asked. The other bachelors and I were required to concoct our answers in real time.

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.

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.

Most of the things at the zoo don't look like us. We're one design that works. Our chimp pals sort of look like us, so that's a different take on the same basic design. But fish don't look like us, and giraffes don't. They look a little like us, but not too much. And insects certainly don't look like us, and they work just fine.

It's hardly a secret that I'm skeptical of declarations that the aliens are out and about on our planet. Still, I try to answer every one of these mails and phone calls because, after all, it's not a violation of physics to travel from one star system to another.

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.

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.

The majority of my UFO diet consists of reports describing suspected encounters. This is not surprising, as there are thousands of sightings annually. The emailer has seen something unusual in the sky that he interprets as probable evidence of alien presence.

Since the Renaissance, a concept called 'progress' has been baked into our society. Progress - founded on an accumulation of knowledge through experience (and in the case of science, through experiment). To build on the past rather than endlessly relive it. That's what separates us from the beasts.

The ideas of science germinate in a matrix of established knowledge gained by experiment; they are not lonesome thoughts, born in a rarified realm where no researcher has ever gone before.

It's hard to imagine anything more interesting than learning how we're woven into the enormous tapestry of existence. Where did our universe come from? How special is our world, and how special are we? We allocate tens of billions of dollars annually to NASA, NSF and academia in search of the answers.

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.

The cosmos is three times as old as Earth. During most of creation's 14 billion year history, our solar system wasn't around. Nonetheless, the early universe still had the right stuff for life, and contained worlds that were just as suitable for spawning biology and intelligence as our own.