LONDON, July 31 (Reuters) - When Thomas Burke clocked 12 seconds in the first modern Olympic 100 metres final in Athens in 1896, few could have dreamed how much faster sprinters would become.
More than a century later, Usain Bolt has brought the world record down to 9.58 seconds but mathematicians and sports scientists are sure the limit of human speed has yet to be reached.
A little like the top sprinters Bolt, Yohan Blake, Tyson Gay and others all jostling for position in the record books, theoretical experts too are vying to place their best predictions for how fast the ultimate 100 metre sprint could be.
At Stanford University in the United States, scientist Mark Denny has calculated that Bolt or one of his competitors could take another 0.1 seconds off the current record to get it down to 9.48.
"That's an estimate based on history and analysis - and of course I'd love to see someone go below that," Denny said in a telephone interview.
"But there have to be limits to human speed - even if people don't like to accept that idea."
John Barrow, a professor of mathematical sciences at Britain's Cambridge University, has a more ambitious estimate of 9.4 seconds, a prediction matched by Reza Noubary of Bloomsburg University in Pennsylvania.
"We're not going to be reaching the limits of human speed anytime soon," Barrow told Reuters.
"And there's no reason to assume Bolt is going to be just shaving fractions of hundredths of seconds off each time. There's scope for some quite big improvements."
Noubary admits Bolt's stunning performances so far have "changed our perception of human capabilities".
"He has become the premier runner in the world," he wrote in a paper analysing Bolt's achievements. And, he added, "Bolt is not done yet".
The man himself agrees. The flamboyant Jamaican, who was beaten by his younger compatriot and friend Blake in both the 100m and 200m at this year's Jamaican trials, has said he reckons the world 100 record will stop at 9.4 seconds.
His current record of 9.58 seconds was set at the 2009 Berlin world championships.
Having analysed Bolt's reaction times to the starting gun - which are generally slower than other top sprinters and often much slower than the 0.1 seconds allowed - Barrow says that is where the most obvious progress could be made
"The time that people record in the 100 metre sprint is the sum of two parts - one is the reaction time to the starting gun and the other is the actual running time," he says.
"So if Bolt could get his reaction time down to say 0.13 seconds, which is good but not exceptional, he'd make some improvement... It may only be few hundredths of a second, but it's certainly room for improvement."
Weather too, has the potential to help or hinder.
Experts point out that when Bolt won gold at the Beijing Games in 2008, he did so in warm and relatively still conditions. Similar weather in Berlin in 2009 might well have helped him clock his 9.58 seconds world record.
The maximum wind speed allowed within athletics rules for the ratification of records is two metres per second, so if London were to be basking in a warm breeze on the evening of Aug. 5, the mark could be broken.
"Everything's got to be perfect," said Denny. "If you get a warm night with a slight tailwind and you're in good shape, then you have to take advantage of that.
"Of course I'd love to see Bolt break the world record - but I'm not holding my breath." (Editing by Alison Wildey)