# Sunlight as a measuring tape

“The moon is about one light second away from the earth”, said Neil deGrasse Tyson.

I was watching Cosmos, the epic documentary series, and I thought of how incredible that is. 1 second appeals to our intuition so easily. Further, I know that light takes 8 minutes and 20 seconds to reach us from the sun. That is 500 seconds. Essentially, the sun is 500 times farther from us than the moon.

Why didn’t anybody tell me this before?!

Besides, it is a blessing that light travels at around 300,000 km per second. This immediately tells me how far the moon and the sun are from the earth. It makes light a great measuring tape for interplanetary distances.

We humans are much better at perceiving relative and round numbers than absolute, exact ones. So please make approximations where necessary. 384,000 km (the distance to the moon) is more accurate than 300,000 km. But one light second is about 20 times easier to remember, and is surely better than only knowing that the moon is far far away.

We could put these relative measures to much better use. Every primary school child ought to know that light leaving the sun reaches us in as much time as it takes to play two sound-tracks. The teacher could loop “Waiting for the sun”, by the Doors twice to have every kid in the class register this fact.

Light’s travel time puts the entire solar system is better perspective. Light from the sun reaches Jupiter in about as much time as a class period (45 min), and by lunch-break, it would have hit Neptune.

##### Note: Planetary distances are approximately to scale, but their sizes are not

Source (solar system distances): Nasa