Measuring Time
- What are timestamps and timescales?
A timestamp is a count, and a count means nothing until you say what you counted and from when. That is a timescale: tick length, origin, and count — and anything with all three qualifies, including some absurd ones.
- How big is a nanosecond?
A nanosecond is about a foot. Once the units are physical rather than numerical, most timing arguments get easier to have.
- How big is a degree?
Each decimal place of latitude and longitude buys a factor of ten. Knowing where the useful digits stop saves arguing about the ones that cannot mean anything.
- Why do you want precise time?
Precise time is seldom the goal. It is the price of admission for something else — which is why the requirement usually arrives from outside engineering.
- Accurately measuring elapsed time
A clock so bad the internet refuses to talk to it still measures a microsecond-scale interval to about a nanosecond. Short durations forgive both ways a clock can be wrong, and knowing when you are measuring one saves real money.
- Visualizing precision, trueness, and accuracy
The most-drawn diagram in metrology, with the axis everyone mislabels put right. Trueness and precision are the two axes; accuracy is the corner where you have both, not a third thing.
- Measurement resolution and accuracy
Coarse resolution does not merely limit precision — it counterfeits it. A grid too coarse to show scatter returns the same confident number every time, and stops being able to warn you.
- The limits of averaging
Averaging buys you improvement that stops. What is left when it stops is bias — and the same story plays out in position, in time, and in frequency.
- Do timestamp errors average out?
No. The archer gets ten arrows and can average them; a network packet is timestamped once. That difference decides which errors you can tolerate — and it moves all the work to before the event.
- Should I prioritize clock agreement or accuracy to UTC?
Usually a false choice. The two are not opposed, most improvements buy both, and the real tradeoff only appears at the very last nanoseconds — where it is a genuine engineering preference rather than a confession of low standards.
- Is my clock right?
Timing failures are usually quiet, and nothing inside a wrong clock knows it is wrong. The only detector is a second clock — and the boundary between what the two share and where they are independent decides what you can learn by comparing them.
- Comparing distant clocks
You cannot run a cable, and neither clock can be the source for the other. So you both watch a third clock in the sky — which drags its error into your answer. Every technique here is a different way of removing it.