Seth Shostak

Consider that the overwhelming majority of those 40,000 near-Earth asteroids are small enough to fit on the parking lot at the mall. And while these rocky runts won't cause Armageddon, they could still flatten such popular hominid hangouts as Manhattan or downtown Des Moines.

On Mars, where the air is spare - a hundred times less dense than on Earth - someone could hear you scream. But you'd have to really strain to get anyone's attention. On the Red Planet, where the wind is high-pitched and faint, even a symphony orchestra will sound as thin as cheap gruel.

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.

When it comes to brains, size matters. It's not all that matters, of course. Whales and dolphins have brains that are larger than humans', but few of the flippered and fluked set win tenure at Stanford. Our brains are the largest in proportion to body size, and they're also highly sophisticated.

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.

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.

Sending greeting cards to aliens is hardly a new idea. In 2005, Craigslist solicited messages for broadcast to space by a transmitter in Florida, and in 2008, NASA beamed a Beatles song to the North Star (Polaris), on the assumption that any putative Polarians would appreciate the Fab Four's 1960s-genre compositions.

Five centuries ago, Copernicus upset humanity's applecart with the news that the Earth is not the center of the cosmos. It could be that, before you've paid off your house, we'll learn that the universe is not the center of the universe, either!

Eternal inflation,' as it's called - the endless generation of new universes - may be a hyper-cosmic imperative. It seems that it must happen.

We can no better imagine what will be happening on the moon 500 years from now than Columbus could imagine contemporary Manhattan. Except to say that it will be a place familiar to billions of people.

Clearly, enriching the cosmos with heavy elements takes a while. So there's inevitably an interval between the sterile aftermath of the Big Bang and a time when the cosmic chemistry set had enough ingredients to make rocky planets (and squishy biology).

Sure, our three-pound brains might be inadequate to understand the universe. But perhaps they're just good enough to build something that can.