Popular answers to this question included “silver,” “white,” “whatever color it’s reflecting,” and “no color at all.” But most mirrors are actually very faintly green. Yes, green.
Centurus A is an active galaxy 11 million light years away in the constellation Centaurus. It's a complex knot of hot and cold gases and dust, tracing out a collision from time long gone past. By looking at it in multiple wavelengths, astronomers can get a better understanding of its structure.
Humans and most other animals are only able to see light in the visible spectrum. But what about infrared, which the alien in Predator famously uses to see prey approaching just by their heat signature. Why can't we do that?
Not surprisingly, there are several ongoing attempts to increase the efficiency of solar cells: IBMs use of concentrator photovoltaics or the University of Delaware's technology that splits light into high energy, low energy, and medium energy chunks are a couple of examples. The latest breakthrough comes from Ohio…