4 ms·> in vacuum it's 300 000km/h 300 000 km per secondby tromp 7y ago> in vacuum it's 300 000km/h 300 000 km per secondmcdevilkiller 7y agoAre you sure it's km/s? :Dtromp 7y agoAs https://en.wikipedia.org/wiki/Speed_of_light https://en.wikipedia.org/wiki/Speed_of_light puts it: "Its exact value is 299,792,458 metres per second (approximately 300,000 km/s"phaemon 7y agoYes, it is.