In the second edition of Where is Everybody? I discuss what Gerard Foschini calls the canonical artefact (TCA) — a flag for the presence of an advanced intelligent life-form.
I don’t propose to discuss the details of TCA in this post — you can read the book if you’re interested — but I do want to provide an update. I was fairly sure that no-one had constructed an example of TCA, but yesterday Foschini emailed me a photo of it: he built it out of coin stacks with black rubber test tube stoppers as separators. Below, shown with gratitude, is Foschini’s TCA.