Several years ago there was a story going around that all the planets were going to line up on a certain date and the combined gravitational effect was going to wreak havoc on the earth, and for all I know send us crashing into the sun. As far as I know none of this ever happened, although, come to think of it, I was inexplicably depressed in 1981. What's the story on this?
I believe you’re referring to the "Jupiter Effect," a scenario put forth, in a book of the same name, by a couple jokers named J.R. Gribbin and S.H. Plagemann. Their treatise, first published back in 1974, predicted that a "superconjunction" of planets due on March 10, 1982, would exert extraordinary tidal forces on the sun and ultimately trigger massive earthquakes here on Mother Earth.
The theory, which involves sunspots, climatic change, and all sorts of other unsupportable hokum, was roundly debunked in various quarters, most notably by Belgian astronomer Jean Meeus, who pointed out that during the alleged "superconjunction," the planets would actually be spread out over a sun-centered arc of some 95 degrees.
If, for the sake of convenience, we ignore the effect of Pluto (an eminently ignorable planet, it has always seemed to me), we see that the planets have occupied far smaller sections of sky before– for example, 83 degrees in 1817, and 46 degrees in 1307–without apparent ill effect. Mr. Gribbin, for his part, was moved to state publicly that maybe he made a little mistake, an admission that seems to have been amply borne out by reality.
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