DARPA turns 50. Here's some of what they're currently working on:

Researchers are working on a two-way speech translation system that would permit soldiers to go anywhere in the world and understand the people around them. The idea, Tether said, is to create a miniature headset that would immediately translate a foreign language into English and feed it to an earpiece. In turn, a reply by an English speaker would be converted into the appropriate language and broadcast from small speakers on the headset.

When the technology is perfected, "the world will become a safer place. People will be able to talk to one another and understand one another," Tether said.

Another project looks for ways to restore severely injured soldiers. Researchers are trying to develop a prosthetic arm and hand that can be directly controlled by the brain and used as a natural limb, with dexterity and sensations. Prototypes are in development, Tether said, and hold promise that disabled soldiers can stay in the military "and contribute as before" rather than be discharged.

DARPA conducts research in almost every field -- biology, microelectronics, satellites, unmanned cars and aircraft. "We are extraordinarily broad. If you can think of it, we're doing it," Tether said.

Of course, numerous projects are classified because they may have a useful military application or because DARPA does not want the world to know everything it is doing.