Can you imagine having to live and work in the dark? Before the invention of the light bulb, people used a variety of different ways to light their way at night. Wax candles and lamps that burned oil and kerosene were common, but they were dirty and risky to use because they created flames to make light. All that changed in 1879 when Thomas Edison perfected a practical electric light bulb that was both bright and safe.

Parts of a Light Bulb
A light bulb has three main parts: a metal base that conducts electricity, a thin wire called a filament and a glass bulb that surrounds and protects the filament. The bulb protects the filament by keeping air away from it.

How It Works
When a bulb is screwed into an electrical socket, it creates a circuit, or loop, which allows electricity to flow into the bulb and through the filament. The filament is made of a metal called tungsten that doesn't let the electricity flow very easily, creating what is known as electrical resistance.

What Makes the Light?
When the electricity pushes its way through the filament, the filament heats up and gets so hot that it begins to glow. The filament glows brightly enough to create light.

Brightness
Some light bulbs are brighter than others depending on how much resistance the tungsten filament provides. You can tell how bright a light bulb is going to be because it has a number rating, expressed in watts. (Watts are a measure of energy used and are named after inventor James Watt.) The higher the number of watts, the more electricity the bulb uses and the brighter the light will be.

New Kinds of Light Bulbs
One problem with these light bulbs is that they aren't as efficient as they could be, which means that they use a lot of electricity compared to the amount of light they produce. To solve this problem, light bulb manufacturers now make light bulbs called compact fluorescent lights, or CFLs. CFLs are more efficient because instead of pushing electricity through a wire, they allow the electricity to flow through a glass tube and light up a combination gas and chemicals called argon and phosphor.

Light Bulb Safety
Modern light bulbs and CFLs are safer than the old candles and lamps they replaced, but they still need to be handled carefully. If a regular light bulb breaks there will be sharp glass that needs to be cleaned up. It can be even more dangerous if a CFL breaks, though, because the chemicals inside are poisonous, especially a a liquid metal called mercury. If one does break, stay away until an adult cleans it up.