Four years ago today I wrote the first entry of this notebook, and this evening, with the first cool wind of September coming through the balcony door, I poured a coffee and reread the whole thing, start to finish.

It is a strange and wonderful thing to do, and I recommend the practice to anyone who keeps any kind of record: letters, journals, even photo rolls. Rereading your own trail is the closest thing we have to that block universe walk I took one New Year, visiting your past selves at their fixed addresses, finding them all still there, mid-sentence, holding their light.

The man who wrote entry one is the one I stayed with longest. I remember being him, and rereading, I can finally see what he could not: how much he already knew without knowing he knew it. He wrote that he wanted to take the world apart to see how it works, and he thought he was announcing an astronomy hobby. He was actually, it is obvious now, beginning to renovate his entire life, with a screwdriver, politely, from the outside in. The universe was the approachable end of a very personal thread. It usually is, I suspect. Show me what someone is helplessly curious about and I will show you, at some remove, what they are healing.

Some accounting, four years in, because I am still an engineer and engineers count.

The notebook taught me that starlight is old and arrives anyway, and so do feelings. That both clocks are right, always, which has retired the word behind from my vocabulary. That a flat sea is waves in agreement, that a howling room wants its frequency found and not fought, that the sun spends a hundred thousand years bumping through the dark and calls it a career. That entropy is possibilities, that the moon is falling and missing and that this is called flying. That trauma is training data and training runs in both directions. That meaning is geography and the map can move. That gravity does not pull, and neither, in the end, do most of the things I spent years bracing against. Geometry all the way down, and geometry can be regraded.

And underneath all the physics, one repeated discovery wearing forty costumes: everything that can rest, wants to. Including, it turns out, me.

What did it cost? Ten minutes most mornings. Some petrol to Delphi and the dark parts of the Peloponnese. A great deal of coffee. What did it pay? A nervous system with updated statistics, tomatoes of legendary quality, a small city of rooms built for joy, two free books, one balcony fully decoded, and this, the trail itself, which several thousand of you now walk with me, which entry-one man would simply not have believed.

To him, and to whoever is tonight where he was then, one coffee into an idea, wondering if it is worth writing down: it is. Write entry one. Not well, not for anyone. Four years is just fourteen hundred tomorrows, and the trail builds itself out of ordinary evenings, and somewhere up the road, a version of you is already rereading it with the September wind coming through the door, grateful to the point of tears that you began.

The coffee has gone cold, the city is glittering, year five starts tomorrow.

I still need to know how things work. Fortunately, the supply of things is excellent.