What is the men’s 100 metres world record, in seconds?

How to get close to this number

Everyone knows this one is just under ten seconds, so the question is how far under. Records at this distance move in hundredths, and the barrier of ten was broken in the 1960s — so sixty years of incremental progress from ten puts the answer in the mid-to-high nines rather than lower.

The margin is what makes this record unusual. Taking over a tenth off in a single race is enormous at a level where records normally fall by a hundredth, and the explanation adds that nobody else has ever run under 9.7. The record is not the top of a cluster; it is an outlier standing clear of everyone.

That is why it has lasted over fifteen years. A record set by incremental improvement gets broken by the next incremental improvement; a record set by a discontinuity requires another one. The high jump question on this site shows the same pattern — an outlier performance produces a record that stops behaving like a record.