First came dark matter, the gravitational source from within our galaxy that astronomers couldn't see. Then came dark energy, the undetectable force pushing the expansion of the universe. Now, NASA scientists believe they have confirmed a new player, dubbed "dark flow," that is dragging hundreds of galaxies along the same path. Even stranger, the researchers believe that dark flow is actually the gravitational pull from matter beyond the edge of the known universe.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.