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A star, a star (and a couple of planets) December 10, 2008

Posted by ourfriendben in wit and wisdom.
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It’s me, Richard Saunders of Poor Richard’s Almanac fame, here today to talk about the Star of Bethlehem, which is beloved worldwide, but is especially beloved around here, so close to Bethlehem, Pennsylvania, the “Christmas City” whose Moravian stars shine on trees and doorsteps throughout the region. For millennia, astronomers have wondered what the brilliant star that led the Magi to the Holy Land that first Christmas might have been. Now, thanks to technological advances and the miracle of computers, they think they’ve come up with a pretty convincing answer.

The frontrunner for the Star of Bethlehem is not a single star but a star and two planets that came together in a truly stellar conjunction in the night sky around 2 B.C., reaching their brightest point in June of that year. The star, unusually bright anyway, is Regulus, the planets Venus and Jupiter. This theory has been in vogue since Griffith Observatory astronomer John Mosley first proposed it over 20 years ago. But it made headlines again this week when Australian astronomer Dave Reneke ran an astronomical sky-mapping software program back over 2,000 years and was able to determine that this conjunction was at its brightest on June 17th, 2 B.C.

You can read a summary of “the search for the Star” and learn more about Mosley’s and Reneke’s findings in an article on www.msnbc.msn.com called “Christmas in June? Stars say maybe.” Incidentally, Jupiter and Venus made headlines again last week when they appeared together in conjunction with the crescent moon. (You may have noticed two very bright “stars” in the sky for the past month or so, looking sort of like Orion’s belt without the buckle. Those “stars” are in fact Jupiter and Venus.)

Seeing Jupiter and Venus shining bright made me wonder how it was that planets could outshine stars, anyway. Well, the answer to that one’s easy: Like our moon, they’re simply reflecting the sun’s light. Though we’re accustomed to seeing the view of the Earth from space that shows a blue-green ball, if we saw Earth from farther off, it too would glow like a star. Leonardo da Vinci was the first to realize this, and he even coined a name for it, “earthshine.”

Thinking about Jupiter and Venus made me wonder about something else, too. All the planets in our solar system are named for ancient Greek and Roman gods: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, even poor Pluto. But if there was a Greek or Roman god named “Earth,” that’s news to me. So how did Earth get its name?

In fact, “earth” comes from Old English “eorthe” and “ertha” and German “erde,” and means exactly what it means to us today: the ground. We’ve been using the word “Earth” to describe our planet for a thousand years. But what did the ancient Greeks and Romans call it?

Maybe a name you’re probably familiar with, Gaia. In Greek mythology, Gaia was a goddess who presided over the Earth. She was also the wife of Uranus. Today, the “Gaia Hypothesis” posits that the Earth is a single giant organism with a cosmic awareness, and people who appreciate the idea of planetary unity often refer to Earth as Gaia. (Apparently, quite a few of them are naming their daughters Gaia, too—who knew? Or at least, when I Googled the origin and meaning of Gaia, what came up first were a bunch of baby-name sites.) 

So, okay, how’d we get from a goddess to the ground—back down to earth, so to speak? Well, if you go back far enough, practically all of us started out calling ourselves something that meant “the people” in our tribal language. Along the same lines, I guess maybe we figured that “the ground” was an appropriate name for the planet we lived on. Not very romantic, but certainly practical.

Let’s turn our attention back to the stars, I mean, planets. If you’ve missed the dynamic duo of Venus and Jupiter, cast your eyes heavenward! It’s truly a beautiful sight.