Olympic results are recorded to different levels of precision depending on the sport. The limit is set by the physical venue and the detection method rather than by the electronics.
What the clock is actually measuring
Timing begins with an electronic signal from the starting device, not with a human hand. That signal is what removes the reaction delay that manual timing introduces.
The finish is where sports diverge. Some measure the moment a body crosses a plane, and others measure contact with a physical sensor at the end of a lane.
Precision depends on which of those is used. A plane can be sampled extremely finely; a physical touch cannot be resolved beyond the tolerance of the surface being touched.
Line-scan cameras on the track
Sprint finishes are judged by a camera that images a single vertical slice at the finish line, thousands of times per second, building a continuous picture of everything passing through it.
Because the image is of the line itself rather than a wide view, an official can read exactly when a torso reached the plane. Limbs and the head do not count.
The system resolves far finer than the hundredth of a second in which results are published. Athletics rounds times up to hundredths as a matter of rule, not capability.
Why swimming does not split further
Swimming times are taken from touchpads at the wall, triggered by pressure from the swimmer's hand. The pad responds quickly but the wall it is mounted on is a built structure.
Pool construction tolerances mean lane lengths can differ by a margin larger than the distance a swimmer covers in a thousandth of a second. Splitting finer would measure the building.
The sport therefore stops at hundredths and accepts shared placings. Two swimmers with identical times are both awarded the position, and both receive a medal.
Reaction time and the false start
Starting blocks in athletics contain force sensors that record pressure against the footplate. A start is judged false when force is applied within a threshold period after the gun.
The threshold reflects an assumption about human reaction rather than a measurement of intent. Movement faster than that is treated as anticipation.
Because the rule is a threshold, it produces occasional disputes about athletes with unusually quick responses. The system trades individual fairness for consistency and repeatability.
What precision changes about the sport
Finer timing has made dead heats rare in sports that can support it and common in sports that cannot. That difference is invisible to spectators but shapes how records are held.
It also affects qualification, where places are decided by fractions and reallocated when times tie. Rules for breaking those ties have to be written in advance.
The underlying principle is consistent across sports. Timing is published only to the precision the venue can defend, and the remainder is discarded rather than reported.
