Light If you’re driving down a dark road on a starry night, you might want to check the odometer. Earlier this month, when traveling astronomer Dennis Mammana did he was greeted with the significant mileage reading of 186,282 miles. That’s the number of miles light travels in one second. Or, if you prefer kilometers, the number you are looking for is 299,792. Mammana muses that in driving to countless observatories, star parties, and night sky photo shoots it has taken his 1998 vintage sport utility vehicle over 13 years to cover that distance. Of course, he considers his next important mileage milestone to be the distance to the Moon.