Light travels at a constant speed of 3.0×108 m/s in a vacuum. (a) it takes light about 1.3 seconds to travel from the earth to the moon. estimate the distance of the moon from the earth's surface, in meters. (b) the astronomical unit (abbreviated au) is equal to the distance between the earth and the sun. one au is about 1.5×1011 m. if the sun suddenly ceased to emit light, how many minutes would elapse until the earth went dark?