John Mravcak, age 9, of Edison, New Jersey, for his question:

What is inside a light bulb?

The one thing they try to seal out is oxygen. This is because oxygen gas makes things burn faster. If there were any oxygen inside a light bulb, the little wire filament that glows with light would burn out much sooner than it does. There is, as we know, a lot of oxygen in ordinary air. So they remove the ordinary air from inside a light bulb. They replace it with small amounts of argon and perhaps other gases that do not help things to burn.

The two wire prongs inside a light bulb are connected to the electric wires that carry current through the house. That is, they are connected when the bulb is screwed into the socket. The ends of the prongs are connected to a fine wire filament. When the switch is turned on, electric current goes into the bulb and tries to squeeze through the narrow filament. This traffic jam creates a lot of heat and the filament glows with bright light. And all these wire trappings are sealed inside the glass bulb, along with a little gas.