The Success of Spaceguard

For years, many scientists warned of the dangers that asteroids pose to life on Earth, but for many years they weren’t listened to. Even after it was first proposed, in 1980, that the dinosaurs were killed off by a huge asteroid striking the Yucatán Peninsula in Mexico,1 there was, in the words of leading astronomer Clark R. Chapman, a “giggle factor” associated with the risk from asteroids.2 This all changed in 1994 when comet Shoemaker-Levy 9 thudded into the side of Jupiter with th...

 We Have the Power to Accelerate Things to Near the Speed ...

Six years ago, in the distant Trisolaran stellar system, Trisolaris accelerated two hydrogen nuclei to near the speed of light and shot them toward the solar system. These two hydrogen nuclei, or protons, arrived at the solar system two years ago, then reached the Earth.

 Nemesis

But why should comets become more likely to hit us every million years? Here we launch ourselves into deep speculation. It has been suggested that the sun has a sister star, and the two orbit each other with a periodicity of about 26 million years. This hypothetical binary partner, which has never been seen but which has nevertheless been given the dramatic name Nemesis, passes, once per orbital rotation, through the so-called Oort Cloud, the belt of perhaps a trillion comets which orbits the...

 It is No Accident that We Inhabit a Veritable Paradise

Imagine a spaceship full of sleeping explorers, deep-frozen would-be colonists of some distant world. Perhaps the ship is on a forlorn mission to save the species before an unstoppable comet, like the one that killed the dinosaurs, hits the home planet. The voyagers go into the deep-freeze soberly reckoning the odds against their spaceship's ever chancing upon a planet friendly to life. If one in a million planets is suitable at best, and it takes centuries to travel from each star to the nex...