Although we've long seen LEDs glow, we haven't always known why it happens

Editor's note: A big congratulations today to Theo Gray, whose Gray Matter column was nominated for a 2010 ASME award in the Columns and Commentary category. Great to see Theo's excellent work being recognized. Here, his latest column from the March issue:

The first light-emitting diodes went on sale in 1962, and you could have any kind you wanted as long as it was dim and red. Green, yellow and orange came next, but blue LEDs didn't debut until 1989. So it may surprise you that the first LEDs, discovered in 1907, included blue-and were made of sandpaper. Read more »

Most houses require hundreds of feet of electrical wire to connect light switches to a main power source, but not my eco-friendly dream home. I've installed a wireless lighting system called Verve that uses radio waves instead of copper wiring to command all the lights and outlets in my house. The system not only saves copper (imagine the savings in a skyscraper) but also lets me put switches wherever I want-beside the kids' beds, in my pocket or even on the dash of my car-without the need to pull out wires or rip up walls. Read more »