irradiation

n. The process of being bombarded with electromagnetic particles. This usually refers to high-energy particles characteristic of radioactive decay such as is used in radiation therapy and are released in atomic explosions. Radiation from space includes a wide array of wave frequencies and energies such as visible light, ultraviolet light, radio waves, and gamma rays. Gamma rays are very high-energy rays which can pass all the way through the Earth so that some form of radiation is always striking both the Earth and our bodies and occasionally causing changes in our genes.