Alan is the British comedian now best known for being the foil and patsy for the traps host Stephen Fry lays for the panelists of the intellectual BBC quiz program Qi. Alan almost always comes in last place at the end of the show since the answers he gives are often not only wrong but obviously so.
"How many moons does the Earth have?" Stephen once asked. "The Earth has one moon," Alan responded, "which is made of cheese." That - the answer "one" - set off the klaxons and flashing backgrounds signaling an answer that was not only wrong, but obviously so. With a show of much regret, Stephen said, there were two. There is the Moon, was we call it, and another smaller moon called Cruithne.
There was quite a bit of skepticism from the panel. "But it does have one," said Alan. "It's called 'the Moon'." "'Blue Moon'," said another panelist Jeremy Hardy. "'I saw you standing alone'. Not 'with a small friend.'" American Rich Hall wondered "So why is there not one romantic song with the word 'Cruithne' in it? 'Blue Cruithne of Kentucky' or 'Cruithne River'?" "Because," Stephen replied with some exasperation, "It was discovered in nineteen-ninety [bleep]ing four!" Nine years, said Rich (the show was aired in 2003), was plenty of time to write a song.
However, Alan and the others had justification for their complaints. First, Cruithne - pronounced "Croo-ee-nyuh" in its proper Gaelic - was discovered in nineteen-eighty [bleep]ing six. Next it isn't really bound gravitationally to the earth. In fact at some times it is nearly diametrically opposite from the earth in the solar system. So it's not a true moon.
Cruithne, then, is simply an asteroid circling the Sun. But because it has a periodicity of 364 days - one day shorter than the earth's, its orbit is in "resonance" with the Earth's. Also Cruithne's orbit crosses the path of the Earth, and it's orbital incline is significantly out of the plane of the solar system. Such peculiarities give Cruithne a curious kidney shaped path in relationship to the Earth, and this can make it look as though its orbit is more influenced by the earth than it really is. On the other hand, Cruithne's orbit is unstable and it does pass close (in astronomical terms) to the Earth. So perhaps in about 5000 years it may go into a true orbit around the earth. It would be a moon then. But it isn't now.
Alan admits it took about four episodes for him to realize he was being targeted as the fall guy. Then he began just to sit in cross armed silence whenever Stephen asked a question. John Lloyd, the creator of Qi, took Alan aside and told him that it took intelligence to get the answers spontaneously wrong. So Alan went back to giving his intuitive guesses. But you can still see in the later episodes he was more careful.
Alan is also quick to point out that, no, Stephen does not really know all that stuff. For one thing he has a script which is rehearsed using stand-ins for the actual panelists. Next, he has both a computer screen in the desk and an earphone both of which can feed him information. Finally, like all television presenters (to use the UK patois) Stephen uses a teleprompter where the script is rolled before his eyes, and he simply reads off the lines. Once when the wording was a bit obscure, Stephen stumbled over the words. The prompter was rolled back, and he tried again. He still flubbed the lines. Alan then pointed out that if the wording wasn't grammatically correct, Stephen actually couldn't read the sentence.
"Cruithne was briefly called earth's second moon", http://earthsky.org/space/cruithne. A good explanation of what Cruithne is and what it does.