June 29, 2009 - ES Tonight

sagar: Author=’Larry Sessions’ program=” video=”Artist’s rendering of a moon base operation. Courtesy NASA.What if you had a time machine and could travel back into the past? You can’t do that, but you can look back in time – literally – when you look out in space. Due to the limited speed of light, absolutely everything we see is in the past, from a tiny fraction of a second for things around us to thousands of years for distant stars.

Take the star Spica, for example. It’s that bright star in the southern heavens just as it gets dark tonight. The waxing gibbous moon is a bit off to the right (west). Our view of the moon is less than a second and a half old, but the light from Spica left the star 260 years ago. We see it as it was in the year 1747.

So what happened on Earth in the year that light left Spica? Aside from the birth of Johann Bode (of Bode’s Law fame) and Thomas Lind’s discovery that citrus fruits prevent scurvy, not much. Still, it’s fascinating to know you’re looking back in time, when you look at distant stars!

Written by Deborah Byrd

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