Planetary Alignment Decreases Gravity    (April Fool's Day - 1976)

During an interview on BBC Radio 2, on the morning of April 1, 1976, the British astronomer Patrick Moore announced that an extraordinary astronomical event was about to occur. At exactly 9:47 am, the planet Pluto would pass directly behind Jupiter, in relation to the Earth. This rare alignment would mean that the combined gravitational force of the two planets would exert a stronger tidal pull, temporarily counteracting the Earth's own gravity and making people weigh less. Moore called this the Jovian-Plutonian Gravitational Effect.

Moore told listeners that they could experience the phenomenon by jumping in the air at the precise moment the alignment occurred. If they did so, he promised, they would experience a strange floating sensation.

At 9:47, Moore declared, "Jump now!" A minute passed, and then the BBC switchboard lit up with dozens of people calling in to report that the experiment had worked!

A Dutch woman from Utrecht said that she and her husband had floated around the room together. Another caller claimed she had been seated around a table with eleven friends and that all of them, including the table, had begun to ascend.

But not everyone was happy. One angry caller complained he had risen from the ground so rapidly that he hit his head on the ceiling, and he wanted compensation.

Moore's announcement was, of course, an April Fool's Day joke. It became one of the most celebrated April Fool's Day hoaxes of the late 20th century. However, it wasn't just a random joke. Moore intended it as a spoof of a pseudoscientific astronomical theory that had recently been promoted in a book by John Gribbin and Stephen Plagemann called The Jupiter Effect.


Published in late 1974, the Jupiter Effect's starting point was the observation that in 1982 a rare alignment of the planets was going to occur, in which all the planets, including Earth, would line up on one side of the sun. This much was agreed upon by all astronomers. This unusual planetary alignment occurs every 179 years, and had last been seen in 1803. But then the authors argued that this alignment was going to cause "one of the greatest disasters of modern times." Through an extended chain of events, it would trigger a series of massive earthquakes on Earth. Los Angeles in particular, the authors said, would be completely destroyed.

The chain of events, as laid out by Gribbin and Plagemann, went as follows. The aligned planets would exert an increased tidal force on the sun. This would trigger an excess of sunspots, causing more solar particles to be flung into the Earth's upper atmosphere. The energy flowing into the atmosphere would generate stronger winds, increasing the earth's rate of spin. The faster spin would place stress on the Earth's crust, and this would, finally, bring about massive earthquakes.

The authors singled out Los Angeles as being in particular danger because it was on the San Andreas fault, which they believed to be under enormous strain. They were sure that, given the slightest nudge, such as that provided by the Jupiter Effect, the fault would move violently — with catastrophic consequences.


The Jupiter Effect received extensive coverage in the media. Interest in it was heightened by the fact that its release coincided with the release of the movie Earthquake starring Charlton Heston, which depicted what might happen "when the big one finally hits L.A." Also, Gribbin and Plagemann weren't just random crackpots, but were actually bona fide scientists. Plagemann, 32, was an astronomer who had consulted for NASA, and Gribbin, 28, was an assistant editor at the science journal Nature.

Senator Frank E. Moss of Utah, chairman of the Aeronautical and Space Sciences Committee, became so worried by what he read in the book that he asked NASA to check into the theory. NASA astronomers responded that while they couldn't definitively rule out that the events predicted by Gribbin and Plagemann wouldn't happen, they felt it all had a very low probability of coming true.

The response from NASA was typical of the response by the scientific community. Astronomers conceded that forces in the solar system might influence earthquakes on Earth. But they insisted that these forces weren't well enough understood to allow the prediction of earthquakes, and they criticized Gribbin and Plagemann for making unfounded leaps of logic that reduced their book to little more than pseudoscience.

Edward Upton of the Griffith Observatory in Los Angeles was particularly harsh in his condemnation. He described the Jupiter Effect as the "Great Earthquake Hoax" and dismissively wrote that it had "the same credibility as a reading of tea leaves."

Upton pointed out a variety of weaknesses in Gribbin and Plagemann's argument. For instance, during the "grand alignment" of the planets in 1982, the planets wouldn't be all lined up in a row, as the cover of the Jupiter Effect implied. Instead, they would be scattered in a spread of 100 degrees of the ecliptic (sun path). Upon noted this was an alignment "only in the sense that the spread is usually much greater than 100 degrees."

Also, there had been no major earthquake the last time the planets had formed a grand alignment, back in 1803. And their decision to single out Los Angeles for destruction seemed totally arbitrary.

The reviewer in the journal Science similarly wrote, "The selectivity in examining the evidence is excessive, the popularized format of the book precludes serious scientific modeling, and the correlations demonstrated are too weak to warrant practical action."

When Patrick Moore joked about the Jovian-Plutonian Gravitation Effect in April 1976, concerns about the Jupiter Effect were still fresh in the public's mind. The implicit absurdity in Moore's spoof was that he replaced a grand alignment of all the planets, as was going to occur in 1982, with an alignment of only Jupiter and Pluto — the joke being that Pluto's mass is so small that such an alignment would have next to no effect on Jupiter's tidal force.

But Moore's joke didn't do much to change public fears about the Jupiter Effect, and Moore became frustrated when, in 1979, he saw that the theory was still being promoted by the media. In fact, it was being dramatized in a program at the London Planetarium. This prompted him to write a letter to the journal New Scientist:


What ultimately reduced the Jupiter Effect to obscurity was the fact that none of its predictions came true. Los Angeles survived 1982 unscathed.

But even before 1982, Gribbin and Plagemann had begun to back off from their theory. In an article in New Scientist (Jul 17, 1980), Gribbin conceded, "Our forecast of peak solar activity coupled with increased seismic risk in 1982 was wrong." But he continued to believe there was a strong link between solar activity (particularly sunspots) and seismic activity on Earth.

In 1982, Gribbin and Plagemann came out with a sequel, The Jupiter Effect Reconsidered, in which they revised the theory to suggest the effect had actually taken place in 1980, and that it had triggered the volcanic eruption of Mount St. Helens. However, the sequel didn't sell as well as the original.

By 1999, Gribbin had repudiated the Jupiter Effect theory entirely and wrote, "I'm sorry I ever had anything to do with it."

Did you try to float Weightless on the Planet Earth? I say: Moore fool you. (by Paul)

Floating sensation — Feet leaving the ground — the clock chimes nine forty-seven. (by Alex)