KEY POINTS:
Tiger Woods and Roger Federer are operating in a higher zone than any of their peers, to the point that they've ended up in their own space race.
The moon in this case is a number. Or two numbers to be precise, the ones which represent the pinnacle
in their sports. Woods is hunting down the 18 golf majors which Jack Nicklaus snared, and has 12 already. Federer is four shy of the 14 Grand Slam singles titles nailed by fellow tennis ace Pete Sampras.
Not that Federer, aged 25, appears overly interested in this duel, or as intensely dedicated to overhauling Sampras the way Woods, 30, has set about charging past Nicklaus.
These are two men who have come to their greatness via very different thinking.
Woods' golf clubs appear as weapons of Jack destruction. In contrast, you can almost imagine Federer tossing his rackets in a bag on some mornings, thinking better of it, and catching a movie instead.
Woods has, until now, set after his prey in battle dress. By comparison, the image is of Federer strolling after Sampras in loafers.
Woods was about half the size of a golf bag when he first appeared on television, swinging a club. It's easy to imagine that a young Woods studied the layout of Augusta for homework. He sees winning majors, and beating THE major number, as his destiny.
Federer, though, still can't work out how he keeps winning the big tournaments, and only started doing so at the ripe old tennis age of 22.
The pair have, on occasions, turned up to support each other. According to Federer, his buddy Woods tells him that he will get to the Nicklaus mark before Federer overhauls Sampras. Federer responds by wishing Woods the best of luck. Really.
The last great sports race to grab international attention was between baseball sluggers Mark McGwire and Sammy Sosa. McGwire was altering his body with dodgy substances, while Sosa did likewise to his bat. At least it was great fun at the time.
Maybe the Woods-Federer joust will fall flat in the end - the timing could be off in a battle that may also be decided on different continents.
But there's a good chance that it could come down to the wire, and despite Woods' confidence, it is the tennis player who has the edge.
For a start, he is closer to the mark. Woods may miss this year's British Open if it clashes with his wife, Elin, giving birth to their first child. "That's the most important thing, not another golf tournament," Woods was reported as saying, although his dismissal of a major as simply "another golf tournament" is surely a misquote.
And yet, Woods says a new family life means his priorities are changing. Woods also knows he can have a rebirth in a sport where the great Nicklaus won a major at the age of 46. Federer knows it is now or never, that the next five years or so are all he has in top tennis.
Doubting anything that Tiger has set his mind on is a dangerous business. Yet despite Woods' amazing run of victories on the PGA tour, Federer still shapes as the more unbeatable in majors. Even though, like many former champions, he has been unable to win on the French Open clay, Federer has such a range to his game that winning in Paris is not the impossibility that it was for a player like Sampras.
Federer is so far ahead of his peers in three of the big tournaments that they have trouble even relieving him of a set. He has far more control of his destiny than the remarkable Woods, who must still bow at times to the vagaries of golf courses and weather.
Woods is vulnerable to another man's superb form in a sport where combatants do not go face-to-face. As good as another player might be, Federer can always disarm him, as he invariably does although his winning ways fade if an opponent can take him to five sets.
More than anything, though, this is a battle between the two great closers in the history of sport. Woods is a shoo-in if he leads on the final day. Even if he is only breathing down someone's neck, they tend to lose their head.
Federer has lost only one Grand Slam final, and that was on clay.
The best men will win, whatever the case. At a time when sports such as athletics and cycling are lying in the gutter, when an English footballer moans about being offered £55,000 instead of £60,000 a week, Woods and Federer have brought enormous honour as well as skill to their sports.
In this side-bet space race, it's hard to know who to barrack for.