And other news from science and technology.

(For the latest Human Nature columns on Terri Schiavo, mandatory pregnancy, and more, click here.)

The American Medical Association proposed to ban teenagers from using indoor tanning equipment. The issue is skin cancer. Some states already require parental consent for tanning salons.

A day of abstinence improves male fertility. A study suggests sperm quantity and quality peak after a day off but decline if you wait longer.

Brain size correlates with intelligence-test scores. To comfort small-headed people, researchers point out that Einstein's brain wasn't very big.

A solar-powered spacecraft crashed during launch due to a failed booster rocket. Pre-launch press reports hailed it as the first privately funded spacecraft. Then they hailed it as the first solar-propelled spacecraft. Now it's $4 million worth of junk.

The government is funding the search for a male birth control pill. One study has found a compound that makes male rats temporarily infertile; researchers aim to find a half-dozen more such chemicals.

Political scientists tried to  quantify the role of genes in politics. Using twin studies, they deduced that genes caused about 40 percent of ideological differences over school prayer, the Moral Majority, capitalism, and property taxes, but genes explained only 14 percent of differences in party affiliation. The researchers suggest politics will become more polarized as people seek like-minded mates.

Chess computers are beating grandmasters. Three machines outscored three grandmasters last fall (one of the humans tied one of the machines; he lost to the other two machines); two more matches begin this week. Grandmasters used to boast about beating the machines; now they say the goal is just to do your best.

Michael Schiavo buried his wife. The gravestone says she "Departed this Earth" on the day she suffered massive brain damage in 1990. It says she was "at peace" on the day she officially died in 2005.

Florida Gov. Jeb Bush ordered an investigation into whether Michael Schiavo delayed calling 911 when his wife collapsed. The incident happened 15 years ago; last week's autopsy report found no evidence to support rumors that Schiavo strangled his wife, broke her bones, or neglected her after she suffered brain damage.