One of the fundamental forms of energy in the Universe. It changes characteristics radically depending on its frequency and wavelength, which tend to correlate closely with each other. Generated in relatively pure form by numerous natural processes such as solar fusion, electromagnetism normally interacts with other energy forms. As of this writing, it is generally thought to travel at a constant speed, known as the "speed of light", or 186,000 miles per second. Larry Spring has demonstrated that electromagnetic energy usually travels through space as an expanding sphere, and will tend to do so until it encounters an obstacle.