Every hero's aura fades, every grand trophy room fills with dust, every glittering team's mystique dents. We know this and still it always confounds us.
Belgium is ranked higher than Brazil in football. Roger Federer is not in tennis' Top Two, Terrific Three, Fab Four or Fantastic Five. And now Manchester United are sitting five places below Hull in the league table and one behind Cardiff. For some reason a lot of football people are grinning.
The league is only six games old, 32 are left, and this is only a slip and not yet a slump. But it is also Manchester United. This happens to other clubs, you see, not them. They were always - if you lived in the time of Fergie - the unmerciful, the chosen, the club that scored the 92nd-minute winner with an arrogant nonchalance that said: We were always going to win, we were just teasing you.
Now, even the smug from United will agree, they are temporarily lousy. Of course, it is all David Moyes' fault and it will remain so till he wins a trophy. But spare a fleeting kind thought for a fellow who has time-travelled to another football planet. Everton, his previous club, live in a modest world. This is United, and they win: it is what they stand for and they will not stand for anything else.
As with Liverpool once, United are said to own a winning culture, as if excellence swirls down their corridors and coats every blade of grass. As if they're conditioned to win. As if the sight of Fergie's statue, Bobby Charlton in a suit and a treasure of trophies is enough to win matches. History does intimidate, but clubs have to keep making history to keep intimidating.
This was Alex Ferguson's genius and it was formidable. He was such a consistent alchemist, turning any team into gold, that he made us believe winning can be hardwired into the DNA of a club. He made us think this culture was so hardy it would last forever. But it is an illusion.