Speed of light

The speed of light was, according to Eugene Jones, 299,792,458 metres per second. (TV: Random Shoes) One could travel faster than this rate; this was called faster-than-light travel. Monarch attempted to travel at this speed and travel backwards in time. After stopping him, the Fifth Doctor stated that such a thing was impossible. (TV: Four to Doomsday) The Third Doctor, however, seemed to think it was and was even experimenting on it himself. (TV: The Claws of Axos)

According to Adric, the Theory of Relativity, e=mc2, meant "energy equals mass times the speed of light squared". (TV: Four to Doomsday)

The speed of thought was equivalent. (PROSE: The Sands of Time)