Dept.: Gray Matter
Project: Making a lightbulb
Time: 30 minutes
Cost: Roughly $50
Dabbler | | | | | MasterThomas Edison famously spent months trying to make a lightbulb work. He tested one material after another in an evacuated bell jar before he finally got a carbon filament to burn long enough to sell it with a straight face. When I had a free afternoon recently, I thought I'd see if I could do it too.
Edison's first mistake was living before tungsten wire was available. Tungsten is way better than carbon as a filament material, and now you can find it in any metal-supply shop. It lasts longer, is less brittle, and glows with a cleaner, whiter light. His second mistake, repeated in classroom physics demonstrations to this day, was using a vacuum to get the air out of the bulb. Clearing out the air is important because at yellow to white heat (3,500
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.