Richard Branson's not the only one eager to explore that other 70 percent of the world. Triton Submarines has designed a three-passenger sub able to dive 36,000 feet, reaching the deepest part of the world's oceans. And while Sir Richard envisions a spaceship-like craft, Triton's design evokes old school bathyspheres: it's a glass globe. Of course, water pressure poses a serious engineering challenge when you descend seven miles below the surface -- the last manned sub to reach that depth had only a single, small window made of plexiglass. The current design uses borosilicate glass
