I Didn’t Know That . . .

Q. Could silicon be the basis for alien life forms, just as carbon is here on earth?

A. Silicon-based life forms are popular in science fiction, but they are unlikely to occur because of the chemistry of the element, according to chemist Raymond Dessy of VirginiaPolytechnic Institute and State University. Writers choose silicon because it falls in the same column of the periodic table as carbon and can make four bond with other elements. But the similarities stop there. Most important, carbon combines with oxygen, producing gaseous carbon dioxide, which is easily disposed of by a living organism. But when silicon combines with oxygen, it forms a solid that would be difficult to get rid of. Also, silicon dose not readily form energy-containing compounds, like the sugars used by Earth life, so metabolism would be extremely difficult.