Thirty Days From Now This Will Look Identical

Just took the first baseline photograph and the scale finally makes sense.

Forty microns per month. That’s what 0.5 millimetres per year actually means when you convert it down to human timescales. A single human hair is 70 microns across. The black prothallus line I’m trying to measure — the growth boundary of this Xanthoria elegans colony living on the north-facing granite I brought in from the ravine — will move less than the width of a human hair every single month.

The photography rig from spore print work almost works but not quite. Contact printing with cyanotypes gave me micron-level resolution for static specimens, but this needs repeatable positioning across months. Same angle. Same distance. Same lighting. The colony can’t move (crustose lichens bond to rock at the molecular level — they’re permanent), but everything else has to return to exactly the same place every time I shoot.

Ended up using three reference pins drilled into the granite, visible in frame. The camera mounts to a machined aluminum bracket that keys to those pins. Repeatability better than 50 microns, confirmed by overlaying two test shots taken an hour apart in Photoshop. The prothallus edge shows as a single pixel-width line. That’s the limit of what I can measure.

Got six specimens. Three foliose (Xanthoria elegans, orange and fast-ish at maybe 2mm/year), two fruticose (Cladonia rangiferina, the reindeer lichen, branching and theoretically 5mm/year), one crustose (Rhizocarpon geographicum, map lichen, the gold standard for lichenometry but impossible to transplant so I’m working with in-situ rock).

The Rhizocarpon is the problem child. It’s the species Roland Beschel used in 1950 to date Alpine moraines — growth rate calibrated over decades, used by archaeologists to date rockfalls and glacial retreat. But it grows 0.5mm/year when young, slowing to 0.1mm/year as it ages. The colony I found might be 20 years old or 200. Can’t tell without measurement history.

Which means I’m not just measuring growth. I’m generating the dataset that will tell me where this colony sits on its nonlinear growth curve. Three to five years of monthly photography before the measurements mean anything.

The terrarium taught me patience for closed-loop systems that take weeks to stabilize. Phototropic sculpture stretched that to 48-hour exposures watching fern fronds move through their arc. This stretches it to years. Plural.

Lichenometry exists because radiocarbon dating has error bars wider than 500 years. If you need to know when a rockslide happened in 1847 versus 1792, radiocarbon gives you “sometime between 1600 and 2000, probably.” Lichen growth rates — if calibrated locally — get you within a decade.

But only if you wait long enough to prove the calibration curve is real.

First measurement interval: 30 days. Mark it: June 7th, 2026. Check back in a month to see if anything happened. Spoiler: it won’t look different. That’s the entire point.