Jupiter Effect answer

Regarding Cecil’s column http://www.straightdope.com/classics/a1_159b.html

While I can’t disagree with Cecil’s answer, I’d like to point out, that at the time that Jupiter Effect was published, Pluto’s mass was assumed to be MUCH more than it is known to be now. It wasn’t until the discovery of Pluto’s moon, Charon, in 1977, that it was possible to accurately determine the mass of Pluto. In absense of any other measurements, Pluto’s mass was set at being near to the large mass assumed by Percival Lowell in his hypothetical “Planet X” reasoning, which launched the search for a planet that resulted in the discovery of Pluto.

For a time Pluto was assumed to have the mass of Neptune, or Uranus, in a body the size of the Moon, leading to the belief that Pluto was the densest object in the Solar System.

Since 1974 two things have changed: With a satellite orbiting Pluto it is possible to determine the mass of Pluto quite accurately by measuring the period of it’s satellite’s rotation; And secondly it’s been determined that Percival Lowell’s original calculations, pointing to an eccentricity in the orbit of Neptune, leading him to hypothesize that there was another large planet to be discovered orbiting the Sun outside of Neptune’s orbit, were in error.

Related question:

If the planets did actually line up, say all within one degree, are they anywhere near close enough to each other to create any noticable effect? Does that sort of alignment ever happen? It seems like it would be inevitable, given enough time, but I’m not sure how to prove it. Anybody here work out the numbers on that?

Feel free to disqualify Pluto, if that makes it easier.

There would be no noticeable effect. Here is a page I wrote about it, with math.

Well, not really. My 1975 Britannica gives an estimate of 0.08-0.17 Earth masses, and, of course, the real figure turned out more like 0.0024 for Pluto and Charon combined…

Pluto could be a hundred times the mass of Jupiter and it would still have a fraction of the gravitational effect on the Earth as does our Moon. Of course, the orbits of the outer planets would be seriously perturbed, but the point is, as far as causing “the end of the Earth” or whatever, it’s just a dopey theory, top to bottom.

(Bad Astronomer: Loved your book.)


I can’t help but notice that the article was originally written on 5th February 1982, while the proposed disaster was predicted for the 10th March 1982. Surely Mr Adams’ statement “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” was (at the time) a tad previous?


Like BA, I’ve debated this a number of times, only to be forced to one unmistakable conclusion: people are going to believe what they want to believe. I ran my numbers and argument a bit differently (I included the Sun’s mass (99% of the solar system will not be ignored!)) and came up with, of course, the exact same conclusion: that it’s a bunch of bunk.

I then got all snippy and decided to take on the astrologers by proving to them that the doctor between their mothers legs exerted a far greater gravitational influence than the planet Saturn (or even Mars), so why did they never take the doctor’s weight into account when they cast charts?

Oh, to be young and arrogant again. :wink:

Yes, people will believe what they want to believe, but some people lack information to make an informed judgement, and when provided the information accept it. True believers, no, but the general mis/dis/uninformed? Sure.