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- n. The speed of electromagnetic radiation in a perfect vacuum: exactly 299,792,458 metres per second by definition.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the speed at which light travels in a vacuum; the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second
Sorry, no etymologies found.