The Station That Only Says the Time

One job, forever

In Fort Collins, Colorado, station wwv has broadcast the time continuously since 1945 — and, from other sites, since 1920. A tick every second. A tone on the minute. A voice announcing the hour and minute in Coordinated Universal Time. It never says anything else. Sister stations do the same job elsewhere: wwvh in Hawaii, DCF77 in Germany, msf in the UK, bpm in China.

Anyone with a receiver can set a clock by it, anywhere within reach of the signal, without asking permission or paying anyone.

What an atomic clock actually is

The tick is generated from a caesium standard. A caesium-133 atom will absorb microwave radiation at one precise frequency — the transition between two hyperfine energy levels of its ground state. That frequency is not a measurement of anything; since 1967 it is the *definition* of the second: 9,192,631,770 cycles. Build an oscillator, tune it until the caesium absorbs maximally, and you have a clock that neither drifts nor needs calibration, because the atom is identical everywhere in the universe.

Modern optical-lattice clocks do far better — they would lose less than a second over the age of the universe.

Why anyone cares

Precise time is infrastructure. gps is a timing system before it is a positioning one: your receiver computes distance from the delay of each satellite's signal, and one microsecond of error is 300 metres of position. Electricity grids synchronise phase across continents. Financial exchanges timestamp trades to the microsecond. Mobile networks hand a call between towers on shared timing. Radio telescopes on different continents combine into one instrument by timestamping their data against a common clock.

All of it is downstream of a signal that says nothing but the time.

Delay is unavoidable

A time signal is always late by however long it took to arrive — up to about 30 milliseconds by shortwave, depending on how many hops it took. Serious users correct for the path. That built-in expectation is exactly what the story in Enspinors exploits: if you know precisely when a tick *should* arrive, then a tick arriving early or late is information.