Perhaps you saw the recent Venus transit of the Sun. But what about an Earth transit?
Obviously we can’t see such a phenomenon while sitting on the Earth itself. But some clever astronomers have done calculations to work out when the Earth would transit the Sun from the perspective of other bodies in the solar system, including the Moon and Jupiter.
“In January 2014, Jupiter will witness a transit of Earth. And we can see it too, the astronomers say, by training NASA’s Hubble Space Telescope on the huge planet and studying the sunlight it reflects.”
(From NBCNews, June 4, 2012)
Using Jupiter as a mirror seems a curious strategy, since the reflected light will also be influenced by the chemical makeup of Jupiter’s atmosphere. However, just as with the hunt for exoplanets, if we can stare at Jupiter for long enough before the transit occurs, we can build a good enough model so its factors can be subtracted out from the Earth+Jupiter signal during the transit. Scientists first plan to test this strategy with a Venus transit that Jupiter will see (Earth won’t) in September of this year. And I’ve seen talk that they used the Moon as a mirror to observe the recent Venus transit from the Earth vicinity — but I haven’t been able to find any images of the result yet. Here’s how it works: