The ozone layer is important because it absorbs ultraviolet (UV) radiation from the sun, preventing most of it from reaching the earth's surface. Radiation in the UV spectrum has wavelengths just shorter than those of visible light. UV radiation with wavelengths between 280 and 315 nanometers (a nanometer is one millionth of a millimeter) is called UV-B, and is damaging to almost all forms of life. By absorbing most UV-B radiation before it can reach the earth's surface, the ozone layer shields the planet from the radiation's harmful effects. Stratospheric ozone also affects the temperature distribution of the atmosphere, thus playing a role in regulating the earth's climate.