Speed of light fibre optic signals which travel 30–40% slower at the speed of light through glass. There are different ways to determine the value of "c". One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine "c" from other physical laws where it appears, for example, by determining the values of the electromagnetic constants "ε" and "μ" and using their relation to "c". Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam,
Speed of Darkness fiction, named The Science of Discworld, written by Terry Pratchett, Ian Stewart and Jack Cohen. In a 2011 interview on BBC Radio 1, frontman Dave King explained that the title track and album title was taken from a quote of Dino Misetić, the artist who designed the album cover, which appeared in the book Sarajevo Marlboro. Dino, who grew up in the Balkans during the Balkan Wars, is quoted in the book, saying: "They taught us what the speed of light is, but nobody can teach you what the speed of darkness is." Flogging Molly: Additional musicians: Speed of Darkness