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.