The purpose of light bulbs:

The purpose of the light bulb is to give light when the Sun is not shining. Another way to say it is light bulbs were invented to help people see things better in the darkness and to be able to see their way through the night. The light bulb pretty much does the same thing that it did in the 1800s; it gives the earth light.

The 1800's light bulb

2000's light bulb