Physicists Create Crystals That Are Nearly Alive
Signs Of Life Palacci et al. They can't reproduce, but they still make us question what it really means to be "alive." The best way to understand something--such as life--is to build it yourself. That's why, determined to understand the way groups move, a team of New York University physicists set out to create particles that could imitate the way flocks of birds, schools of fish and even colonies of bacteria organize and move together. What they ended up with, described in Science magazine yesterday, were two-dimensional "living crystals" that form, break, explode and re-form themselves elsewhere. The researchers developed self-propelled particles that would turn on in response to blue light. When the light is on, the randomly swimming particles collide and cluster. A chemical reaction set off by the light causes the particles to crystalize. When the light turns off, the particles stop and split apart. The crystals...