Think About Light Speed

Think About Light Speed
by Dave Adalian

My birthday is in July, making this a perfect time to talk about cosmic distances and the speed of light.

Make sense?

It does if you realize somewhere out there is a star as many light years away from Earth as I am years old.

While I’ve been living my life, going to school, working, getting married and having children, light from my birthday star been streaming across the universe at, well, light speed, of course. Light speed is the fastest anything can go, as far as we can tell, about 186,000 miles every second--more than seven trips around Earth’s equator every time your heart beats.

How far will the light from my birthday star have come to get to me?

For perspective, remember the Moon averages a distance from Earth of about one and a half light seconds.

It took our space ships four days each way to close that meager gap.

The Sun, at an average distance of 93 million miles away, is only eight minutes distant at the speed of light.

The furthest planet out from the Sun, Pluto, is only a scant five and a quarter light hours from us. The Voyager probes, the fastest man-made objects there are, passed that distance in about 12 years.

Far beyond that, marking the distant edge of the Solar System, is the Oort Cloud, a sphere of comets surrounding our sun at a distance of about one and a half light years, or somewhere in the neighborhood of nine trillion miles.

The Voyager probes will need about 40,000 years to get there.

Light from my birthday star will have come the better part of 214 trillion miles, and it’ll hit us just as I finish my 36th trip around the Sun--a nifty coincidence making the occasion seem more grandiose.

This year, my birthday star is 54 Piscium--a dim star in the constellation Pieces. I could have searched one of several lists of stars available in books and online to find it, but instead I used a clever little program at the Joint Astronomy Centre.
If you let the Centre do the work, you’ll also get a map of the sky you can use to find your birthday star. If you have trouble finding your star, I or one of my fellow amateur astronomers would be happy to help at the Tulare Astronomy Association’s monthly star parties.

Clear skies!

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This column originally appeared in the Visalia (Calif.) Times-Delta on June 24, 2003.