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There are situations in which it may seem that matter, energy, or information-carrying signal travels at speeds greater than c, but they do not. For example, as is discussed in the propagation of light in a medium section below, many wave velocities can exceed c. The phase velocity of X-rays through most glasses can routinely exceed c, [45] but phase velocity does not determine the velocity at which waves convey information. [46] Magalotti, Lorenzo (2001) [1667], Saggi di Naturali Esperienze fatte nell' Accademia del Cimento (digital, onlineed.), Florence: Istituto e Museo di Storia delle Scienze, pp. 265– 266 , retrieved 25 September 2015 Taylor, EF; Wheeler, JA (1992). Spacetime Physics: Introduction to Special Relativity (2nded.). Macmillan. p.59. ISBN 978-0-7167-2327-1. Midwinter, JE (1991). Optical Fibers for Transmission (2nded.). Krieger Publishing Company. ISBN 978-0-89464-595-2.

Converter: Write Integer & Decimal Numbers in Words, US American English

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