Jovian–Plutonian gravitational effect

Patrick Moore (4 March 1923 – 9 December 2012) was the doyen of British television astronomers, boasting a long career in public service broadcasting, a quick-fire manner of speech, and a number of eccentric habits, including the wearing of a monocle. A wartime navigator in the Royal Air Force's Bomber Command, he was elected a Fellow of the Royal Astronomical Society in 1945 and presented BBC Television's The Sky at Night programme from 1957 until his death. He was appointed an Officer of the Order of the British Empire in 1968. Above all, Moore had a high level of public recognition in the United Kingdom as a respected astronomer.[1]

The planet Jupiter is two and a half times as massive as all of the other planets in the Solar System combined.[2]

Pluto is so small and so remote from the Sun and the Earth that it was not discovered until 1930.[3] It was classified as a planet at the time and remained as such for 76 years until 2006, when the International Astronomical Union reclassified it as a dwarf planet, as it belongs to a belt of many similar small objects.[4] Thus, at the time of the hoax, Pluto was considered to be the ninth planet in the solar system.

On 1 April 1976, Moore stated to radio listeners that an astronomical event would take place at 9:47 a.m. that day, a conjunction of Jupiter and Pluto, which was expected to have an effect observable everywhere. As Pluto passed behind Jupiter, it would briefly cause a powerful combination of the two planets' gravitational forces which would noticeably decrease gravity on Earth. If listeners were to jump into the air at that exact moment, they would find they felt a floating sensation.[5][6]

Soon after 9:47 on that morning, the BBC began to receive hundreds of telephone calls from people reporting they had observed the decrease in gravity.[5] One woman who called in even stated that she and eleven friends had been sitting and had been "wafted from their chairs and orbited gently around the room".[7]

The story was quickly revealed as an April Fools' Day hoax. Martin Wainwright later wrote in The Guardian that Moore was "an ideal presenter" to carry off the hoax, with his weighty delivery having "an added air of batty enthusiasm that only added to his credibility".[7]

In 1980, Moore collaborated with Clyde Tombaugh, the man who had discovered Pluto in 1930, to publish a new book about the dwarf planet.[8]

The hoax claims that the gravitational pull of Jupiter and Pluto combined will cause one to spend a significantly longer amount of time in the air due to an increase in gravitational pull from the distant planets; however, this is incorrect. Although other planets do exert a gravitational pull on humans on Earth, the amount is very small.

Although Jupiter is very massive, it is also very far away. When at its closest distance to Earth of about 600 million kilometers, Jupiter has a gravitational pull of 0.00013 newtons on a person with a mass of 100 kg, according to Newton's law of gravity. About 7.5 million times weaker than the Earth's gravity, this is roughly equivalent to the gravitational attraction of a compact car from half a meter away. Similarly, the gravitational pull of the dwarf planet Pluto on a person on Earth is roughly equal to that of a marble 100 meters away. Thus, the gravitational impact of the planets is far too small to be able to cause a person to weigh noticeably less, or stay in the air noticeably longer when jumping.

• Pluto in fiction
• Jupiter in fiction
• The Jupiter Effect
• The War of the Worlds (radio drama)

• Tombaugh, Clyde W., Pluto in The Astronomy Encyclopaedia, ed. Patrick Moore (London, M. Beazley, 1987)

• sirpatrickmoore.com - official site