One of the most beautiful wonders of nature God has given us is the amazing variety of shapes of snow crystals that fall from the sky on a cold winter's night.

On his widely popular Cosmos science program in 1980, Carl Sagan described our paltry existence in pathetic terms: "We live on an insignificant planet of a humdrum star, lost in a galaxy, tucked away in some forgotten corner of universe in which there are far more galaxies than people." Several developments since then have altered this perception dramatically.

When speculating about life in the universe, scientists need to be more realistic than Hollywood. In Star Trek, no matter where the actors land, they can walk around and breathe the air. That may be easier on directors, but for a surface to be habitable, there are physical requirements.