Light travels at a speed of exactly 299,792,458 meters per second in a vacuum, which is approximately 186,000 miles per second (or about 671 million miles per hour). This speed is a universal physical constant denoted by the symbol "c." It is the upper limit for the speed at which information, matter, or energy can travel through space. This speed of light applies to all forms of electromagnetic radiation, including visible light. It remains constant irrespective of the relative motion of the source or the observer, a fact central to Einstein's theory of relativity. Because light travels so fast, it can seem instantaneous over short distances, though for astronomical distances this delay becomes noticeable, allowing us to see objects in space as they were in the past.