Six of the scariest ideas in science

Popular Science magazine listed six of the scariest ideas in science on Saturday. One is Merciless Robot Soldiers. The South Korean government and Samsung Techwin recently debuted SGR-A1, a weaponized robot that autonomously tracks intruders up to about two and a half miles away with high-resolution and infrared cameras. Anyone who doesn't give the robot's voice-recognition system the correct secret code is identified as an enemy to a remote human operator, who directs the Robot to unleash a warning, rubber bullets, tear gas or live rounds.

Reanimated Infection Up to 50 million people worldwide perished in the 1918 Spanish flu pandemic. Within a year, the virus mutated, immunity spread, and the flu vanished. In October 2005, a team led by the Centers for Disease Control and Prevention pieced together the virus's genome from lung tissue of a 1918 flu victim buried in Alaskan permafrost and brought her killer back from the dead. It's out there, in a lab fridge, deadly as ever, right now.

The 22-Hour Workday A new crop of "wakefulness- promoting" drugs can improve alertness?awith no real side effects. Last summer Darpa, the U.S. Department of Defense's advanced-research arm, tested the drug CX717 by exposing subjects to battle conditions for four consecutive 20-hour days. Sleeping only four daylight hours, they remained amped and alert. Meanwhile, prescription modafinil can keep civilians fresh for 48 hours. Its successor, armodafinil, poised for FDA approval, lasts even longer.

Planetary Solar Shield The latest plan for fighting global warming sounds more like intergalactic warfare: Launch clouds of miniature spacecraft that bend 1.8 percent of the sun's light away from Earth. Roger Angel of Steward Observatory Mirror Laboratory in Arizona has worked out the math. Now, with financial backing from the NASA Institute for Advanced Concepts, he's making a prototype of a light-diverting material. The gram-weight flyers he has in mind would be shot into L1 orbit, a sweet spot that follows the same yearly path as the Earth. From that vantage, the crafts' collective shadow would help cool the entire planet.

The Ultimate Vicious Carnivore Scientists at the Institute of Cytology and Genetics in Novosibirsk, Russia, have been selectively breeding silver foxes for hostility. After 36 generations, the 200-some foxes scream, snap, and lunge when humans approach their cages.

Grow New Appendages Amphibians can regenerate limbs. Mammals can't. "This is a significant problem," says Tulane University cell biologist Ken Muneoka. Now two teams of bioscientists are out to correct our evolutionary shortcoming under a recent 7.6-million dollars Darpa grant. The current goal is to produce a mammalian blastema?athe cell bud that forms a new amphibian limb. In four years, Darpa wants a regrown mouse finger. Human research is the logical next step.