Hand timing makes the old record book unreadable

Sprint records set on stopwatches are not comparable with electronic marks, and the sport handles the gap with a fudge.

A human being holding a stopwatch starts it on the sight of the smoke or the flash and stops it on the sight of a chest crossing a line. The starting reaction is systematically quicker than the stopping reaction, because you can anticipate a gun and you cannot anticipate a finish. The result is a time that is reliably too fast, by something in the region of a quarter of a second over a short sprint.

That is not a rounding error. In the hundred metres it is the difference between an era and a myth.

Athletics deals with this by applying a conversion when comparing hand times to automatic ones, adding roughly a quarter of a second for sprints up to two hundred metres and a smaller correction for longer races. It is a sensible convention and it is also an admission that two centuries of the record book are estimates. Timekeepers in the same stand would routinely differ from each other by a tenth or more. Officials took the middle value, or the fastest, or an average, depending on the meeting and the year and how badly a national record was wanted.

Fully automatic timing, triggered by the gun and read from a photo finish image, ends the argument by removing the human from both ends. Athletics made it compulsory for records in the late 1970s. Everything before that is a different measurement system wearing the same units.

This matters more than nostalgia because arguments about progress lean on the comparison constantly. Someone will point out that a sprinter from the 1960s ran a time that would still make a final today. On a stopwatch, on a cinder surface, in shoes with no plate, hand-timed by three men in blazers.

I am not saying the old athletes were slower than they looked. Several were remarkable and some would be excellent now. I am saying we do not know within a quarter of a second, and a quarter of a second is the entire span of a modern sprint final from first to last.

The record book reads as one continuous list. It is at least two lists, and the join is invisible unless you know where to look.