A lot of ideas you think up have already been thought of and patented long before you were born. So a few minutes after I had this idea, I went looking for people who had already done it. Not surprisingly, I found a couple almost immediately.

One is a project right here on HaD, the "Gammaclock" from 2018. This is almost exactly what I wanted to build. This one had an interesting idea for adjusting the rate of the clock: the radioactive source was to be mounted on a screw, so it could be adjusted closer or further from the geiger counter. Unfortunately, the author seemed to abandon the project after just a few days, and there hasn't been an update on it in several years.

The next source I found was from a guy writing a book about clocks., which contains quite a collection of ones that use radioactive decay. One is currently inside a Japanese time capsule, designed to move a dial as a tiny metal accordion is filled with the helium decay products from a tiny pellet of plutonium, a process which will take 5,000 years.

Also included were several patent listings, filed a bit before quartz wristwatches broke onto the scene. Perhaps in an alternate timeline, the cheap watch prize in your cereal box could have had technetium-99 inside.

Probably the best historical precedent for a clock that works like this one is which was once installed in the (then brand new) New York Chase Manhattan Bank building in 1959, counting pulses of cesium-137. Little description remains of this device online, except for the memories of one of the old executives, who said it was widely inaccurate and removed for repairs often, until one day it simply disappeared. How it earned the name “atomic clock” is anyone’s guess, since the first atomic clocks as we normally call them had already been invented by this time.

As of writing this (July 2025), someone has just published this one, no doubt another entry for the 1 Hz challenge: Lord Vetinari’s Clock with Radiation. The author of this one is trying to use radiation directly to drive their clock, varying the distance between their source and detector to get that magic tick rate of once/second on average. They are somewhat helped by using a pair of detectors in order to narrow down the specific energy and direction of the radiation to tell their source apart from background radiation.

The geiger counters I'll be using won't have that luxury, they detect radiation of all energies in whatever direction the particles happen to hit them from. I'll attempt to drown out the natural background radiation by using a "hot" sample that makes the counters click fast enough that the background is insignificant. Also, I'm not going to build any sort of adjustment into mine, it's going to be a matter of carefully calibrating what rate the final assembly ends up as, and scaling that number to the correct time accordingly. Since mine will click many times per second, I'm hoping this will help drive a similar clock mechanism with reasonably regular length seconds, not the mind-melting uneven ticking of a proper Vetinari Clock.