In 1912, an enterprising hobbyist with a copper wire antenna strung across his attic could pull the correct time — accurate to a fraction of a second — out of thin air, courtesy of the most famous iron lattice in Paris. Dr. Pierre Corret's slim pamphlet, extracted from the science weekly Cosmos, opens with this matter-of-fact astonishment:

On sait que la station radiotélégraphique de la tour Eiffel émet deux fois par jour, à 10h45m du matin et à 11h45m du soir, des signaux horaires, suivis, le matin seulement, de télégrammes météorologiques. La portée de ces signaux, qui dépasse actuellement 5 000 kilomètres, sera prochainement plus grande encore.

Translated: the Eiffel Tower broadcast time signals twice daily, followed each morning by weather telegrams, with a range already exceeding 5,000 kilometers and growing. "On sait" — "as is known" — is the giveaway. To Corret's 1912 readership, this was unremarkable plumbing of modern life. To us, it is a vanished public utility.

Corret was a physician-turned-radio-evangelist who wrote a string of popular manuals teaching middle-class Parisians to build receivers at their dining tables. This pamphlet, already in its "douzième mille" (twelfth thousand printed) by 1912, was a how-to: erect an antenna, ground it properly, tune in, and let the Tower set your pocket watch and tell you whether to expect rain over Brittany.

The forgotten part is not that the Eiffel Tower broadcast signals — radio historians remember this — but the scale and intimacy of the use case. Consider what was actually happening:

• A national time standard, broadcast wirelessly, decades before WWV (1923) or the German DCF77 (1959), and three-quarters of a century before GPS made nanosecond time ubiquitous.
• Weather forecasts pushed to citizens at home, with no telephone, no newspaper, no intermediary — a true broadcast service before "broadcasting" existed as a word for entertainment.
• Range over 5,000 km from a single transmitter, meaning a ship's captain in the mid-Atlantic and a farmer in Algeria received the same tick at (almost) the same instant.

The science was sound. Gustave Ferrié had militarized the Tower for radio in 1903 precisely to save it from demolition, and by 1910 the Bureau des Longitudes was using its signals to coordinate astronomical observatories across continents — the first practical demonstration that radio could synchronize clocks better than any pendulum or telegraph wire. The 1912 service Corret describes was, in effect, the world's first consumer time-sync API.

What modern readers will recognize: every smartphone you own runs a descendant of this idea. The NTP packet arriving at your laptop, the GPS fix in your car, the cesium-disciplined oscillator humming in a cell tower — all are the great-grandchildren of those 10h45 dots and dashes rippling out of the Champ de Mars. The Tower stopped transmitting time signals in 1971. The service Corret evangelized to amateurs simply dissolved into the invisible infrastructure we now take for granted.