The electromagnetic spectrum is a collective term for all of the known frequencies and their linked wavelengths of the known photons. It extends from below the low rates used for modern radio communication to gamma radiation at the short-wavelength end. As a result, thousands of kilometers down to a fraction of the size of an atom are being covered. On the other side, the length of a long-wavelength can be the universe's size, though it was believed until the 20th century that this spectrum was infinite. Think you can spot all the different words associated with the electromagnetic spectrum? Give it a try.