A Beautiful Planet calls Earth's atmosphere "a delicate cocoon of air that shields us from our star's radiation." Of course, the atmosphere doesn't completely block electromagnetic radiation from the Sun; without some sunlight reaching the surface, plants could not harvest the Sun's energy, and practically no life as we know it could exist. The atmosphere's ozone layer does filter out much of the harmful ultraviolet light (or "UV rays") produced by the Sun. UV rays can cause skin cancer, and catastrophic damage to the ozone layer may have contributed to Earth's most extensive mass extinction of species ever, the End-Permian extinction (also known
Ultraviolet index numerical ranges, the recommendations for protection are as follows: When interpreting the UV Index and recommendations, be aware that: According to the U.S. Environmental Protection Agency, a helpful method to estimate the amount of UV radiation people are exposed to is by observing the length of their shadow. A taller shadow may mean a lower UV exposure while a shorter one could translate to exposure to higher levels of UV radiation. Ultraviolet index The ultraviolet index or UV Index is an international standard measurement of the strength of sunburn-producing ultraviolet (UV) radiation at a particular place and time. The scale