All eras end, be they political, cultural or sporting, but it is not always obvious at the time. The stars of the silent movies must have realised retirement beckoned when the talkies arrived, but the purveyors of prog rock would not have watched the Sex Pistols torment interviewer Bill Grundy on television and thought: "That's it for the synthesizer." Similarly few in 1945, as they celebrated victory, realised the sun was about to set on the British Empire.
In sport, even team sport, dominance tends to be bound up with individuals. Leeds United's decline after Don Revie joined England in 1974 was no surprise, even if they still had it in them to reach a European Cup final. Likewise Huddersfield Town waned after Herbert Chapman moved on to Arsenal in 1925. Liverpool, however, went from triumph to triumph after Bill Shankly gave way to Bob Paisley in 1974.
Which leads us to the fin de siècle atmosphere at Highbury on Tuesday night. With Chelsea cruising to a second successive title the annual showdown was a sideshow. Both Sir Alex Ferguson and Arsène Wenger admit Chelsea are out of reach. Being competitive to their core, they add riders. Ferguson criticises Chelsea's lack of style in their "grinding out 1-0 wins". Wenger talks disparagingly of "financial doping". But football has never been a level playing field. At Monaco the principality's favourable tax regime helped Wenger attract players. United have long benefited from being one of the game's wealthiest clubs - they have broken the English transfer record five times under Ferguson. Hard as it is, both men have to accept the new reality and rise to the challenge.
Each talks confidently of rebuilding, of investing in youth. "Eventually we hope to reach Chelsea's level," said Ferguson. "We have a young team who will get better. You can see what is going to happen to us over the next two or three years and in the mean time we just keep going." Wenger added: "Chelsea have a mature team. All their players are between 25 and 30. They have power and a lot of self-belief. We have a young team."
For these old rivals, Wayne Rooney and Cristiano Ronaldo, Cesc Fabregas and Robin van Persie are the future, followed by Giuseppe Rossi and Arturo Lupoli, once team-mates in Parma's youth set-up, now the standard bearers for the next generation to emerge from the academies at Carrington and London Colney.
But their maturity is some way off. Time presses. Wenger is secure in his post, Ferguson less so, but both need immediate evidence of progress, not regress. They can take heart from the knowledge that both teams remain a force. United had taken 32 points from 36 prior to Tuesday night, while Arsenal were one of the first teams to reach the Champions' League knock-out stages. A composite XI would be some team.
But a composite squad would barely match Chelsea's and it shows. United are out of the Champions' League and 13 points adrift in the Premiership. Arsenal are fifth in the Premiership, out of the Champions' League qualifying places, and a staggering 24 points behind Chelsea. The absence of Roy Keane and Patrick Vieira, and the presence of Pascal Cygan and John O'Shea, illustrated a lack of individual leadership and squad depth.
"They miss me," said Vieira, unhelpfully, on the eve of the game. He then returned to Turin, where Juventus are disappearing over the Serie A horizon, eight points clear of Internazionale and nine ahead of Milan.
So are Milan regarded as a team in crisis? Obviously they are in the Italian media but the crisis is temporary. Juventus are the form club but Milan can match them financially. The dominance is cyclical, not terminal.
Chelsea's fiscal might means it is different in England. Pre-Abramovich, United would now be engaged in a titanic duel for the title with Liverpool. Indeed, they have seven more points now than they did at this stage in 2002-03, the last time they won the title. Instead they are scrabbling for baubles, such as the Carling Cup and an automatic qualifying place in the Champions' League. The concern for Ferguson is whether this will be enough to satisfy the Glazers.
Arsenal still have Europe to play for this season and while they are not among the favourites, neither were Liverpool last year. If Thierry Henry is in the mood, Sol Campbell fully fit and Jens Lehmann clear-headed they are capable of beating anyone. Though Henry was quiet on Tuesday, some of his finest performances have come on foreign fields, notably in Rome and Milan.
Arsenal's worry is that next season all his performances will be on foreign fields, mostly Spanish. Wenger must prove to Henry that the immediate future is bright, as well as the long-term one, otherwise Arsenal's revival will be significantly put back.
Yet Chelsea will not dominate for ever. History shows that. Even Dynamo Berlin stopped winning the East German championship eventually, though only after the fall of the Berlin wall and collapse of the Stasi, the secret police who backed the club.
In Chelsea's case Jose Mourinho may get bored and go off to test himself in the revolving dug-out of Real Madrid, surely the ultimate challenge for such an egotist. Or Frank Lampard and his Catalan wife might be lured to Barcelona, where the sun shines and the football glitters.
Or, and this would be catastrophic for Chelsea, Roman Abramovich could find other interests - or worse. A previous benefactor died prematurely in a helicopter crash and Matthew Harding had no need of bodyguards. One would not wish tragedy on anyone, but the possibility underlines the vulnerability of Chelsea's empire. Even if his heirs did not ask for their money back, without Abramovich's largesse they would be saddled with an unmanageable wage bill.
There is too great a weight of history, too large a body of achievement, too much cash being generated, for Manchester United and Arsenal to fade from contention, but their immediate destiny depends not on events at Old Trafford or Tampa, Highbury or Ashburton Grove, but at Stamford Bridge.
Decline and fall of English footballing empires
All good things come to an end Are United and Arsenal declining like the giants of the past?
Leeds United 1968-1974
What they achieved Twice champions (three times runners-up), once FA Cup winners in a six-season period.
Then what Did not finish in the top three until 1992 when they won last First Division title before creation of the Premiership.
What they achieved 10-times champions (four times runners-up); twice FA Cup winners and European champions on four occasions (1977, 1978, 1981 and 1984) in 15-year period.
Then what Have not won a championship since 1990, twice FA Cup winners.
What they achieved Twice champions (once runners-up) and once FA Cup winners in four-year period. Also won the European Cup-Winners' Cup.
Then what Have not finished in top three since. One FA Cup win over 10 years ago.
Manchester United 1992-2003
What they achieved Eight times champions (and twice runners-up), three times FA Cup winners and European champions once (1999).
Then what Finished third in the last two seasons, won FA Cup in 2004.
What they achieved Three times champions (and four times runners-up) and three times FA Cup winners over a seven-year period.
Then finished second and won FA Cup.Reuse content