Second Moon

In 1846, Frederic Petit, director of the observatory of Toulouse, stated that a second moon of the Earth had been discovered. It had been seen by two observers, Lebon and Dassier, at Toulouse and by a third, Lariviere, at Artenac, during the early evening of March 21, 1846. Petit found that the orbit was elliptical, with:

• a period of 2 hours, 44 minutes, 59 seconds;
• an apogee of 3,570 kilometers (2,218 miles); and,
• a perigee of just 11.4 kilometers (7 miles).

Le Verrier, who was in the audience when Petit made the announcement, grumbled that one needed to take air resistance into account, something nobody could do at that time. Petit became obsessed with this idea of a second moon, and 15 years later announced that he had made calculations about a small moon of Earth which caused some then-unexplained peculiarities in the motion of our main Moon. Astronomers generally ignored this, and the idea would have been forgotten if a young French writer, Jules Verne, had not read an abstract. In Verne's novel From the Earth to the Moon, Verne lets a small object pass close to the traveller's space capsule, causing it to travel around the Moon instead of smashing into it:

"It is," said Barbicane, "a simple meteorite but an enormous one, retained as a satellite by the attraction of the Earth.""Is that possible," exclaimed Michel Ardan, "the earth has two moons?"
"Yes, my friend, it has two moons, although it is usually believed to have only one. But this second moon is so small and its velocity is so great that the inhabitants of Earth cannot see it. It was by noticing disturbances that a French astronomer, Monsieur Petit, could determine the existence of this second moon and calculated its orbit. According to him a complete revolution around the Earth takes three hours and twenty minutes. . . . "
"Do all astronomers admit the the existence of this satellite?" asked Nicholl.
"No," replied Barbicane, "but if, like us, they had met it they could no longer doubt it. . . . But this gives us a means of determining our position in space . . . its distance is known and we were, therefore, 7,480 kilometers above the surface of the globe where we met it."

Jules Verne was read by millions of people, but not until 1942 did anybody notice the discrepancies in Verne's text:

1. A satellite 7,480 kilometers (4,648 miles) above the Earth's surface would have a period of 4 hours, 48 minutes, not 3 hours, 20 minutes.
2. Since it was seen from the window from which the Moon was invisible, while both were approaching, it must be in retrogade motion, which would be worth remarking. Verne doesn't mention this.
3. In any case, the satellite would be in eclipse and thus be invisible. The projectile doesn't leave the Earth's shadow until much later.

Dr. R.S. Richardson of Mount Wilson Observatory tried in 1952 to make the figures fit by assuming an eccentric orbit of this moon: a perigee of 5,010 kilometers (3,113 miles), an apogee of 7,480 kilometers (4,648 miles), and an eccentricity of 0.1784.

Nevertheless, Jules Verne made Petit's second moon known all over the world. Amateur astronomers jumped to the conclusion that here was an opportunity for fame -- anybody discovering this second moon would have his name inscribed in the annals of science. No major observatory ever checked the problem of the Earth's second moon, or if they did they kept quiet. German amateurs were chasing what they called Kleinchen ("little bit"). Of course they never found Kleinchen.