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Probably you’ve heard the exciting news that NASA has discovered an earth-like planet circling a sun-like star “This is a major milestone on the road to finding Earth’s twin,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. Earth’s twin? With people like us — our twins — a parallel universe! Wow!
Well, no. But the Kepler program will run out of money if it doesn’t get a fresh infusion of funds, and now seemed like a good time to talk about finding an earth-like planet.
The planet pictured above is the one NASA has discovered. Or maybe not. The planet is too far away to be seen, in the ordinary sense of that word, by even the most powerful telescopes. NASA postulates its existence by circumstantial evidence. For example, if something repeatedly dims the the light from a star, you can assume that whatever is dimming the light is going around and around that star, like a planet. And if you figure out how rapidly the planet is circling the star and at what distance, you can make a good guess at how much radiant heat is falling on the planet. So you can build up, piecemeal, a picture of the planet. Then you tell an artist what you know, or what you guess, and the artist can paint a picture like this one.
NASA’s online announcement says, “The planet is about 2.4 times the radius of Earth. Scientists don’t yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets.” We don’t mean to be churlish, but apparently the circumstantial evidence isn’t even strong enough for us to play 20-Questions and figure out if this things is solid, liquid or gas.
Now SETI, (Search for Extra-Terrestrial Intelligence) is back on line again with it’s ATA (Alien Telescope Array), listening for electronic signals from an alien intelligence. And they plan to turn their attention to Kepler-22b. That planet is 600 light years distant from us so an electromagnetic wave that reaches us now would have been sent from Kepler-22b in 1411. We didn’t know about electricity back then, though Chaucer did write a book on the astrolabe a few years earlier. If we send a signal today to those advanced aliens, it will reach them in 2611, our time. (With any luck, we will have solved our illegal aliens problem by then and be ready for the extra-terrestrial aliens.) That’s a lag of 1200 years between saying “We’re here!” and getting a “And we’re over here!” reply. And 1200 years ago it was 811 on this planet. Maybe we should wait for a scientific breakthrough that will permit us to juggle space and time so we can visit Kepler-22b on our vacation. That’s got a better chance of happening and makes more sense than a conversation with a 1200 year time lag.