On New Year's morning I did the thing I do every year now, walked out early into the emptied city, and this year I brought Einstein's strangest idea along for company.

There is no morning like it. Athens, exhaled and holy, streets swept clean of people, last night's confetti in the gutters, the light coming up gold over balconies still holding their strings of lamps. A city the morning after its biggest exhale. I walked for two hours and met a street cleaner, three cats, and one man carrying flowers somewhere with great purpose. Καλή χρονιά, we told each other, strangers, beaming. Good year.

The idea I brought walking is called the block universe, and it follows, mathematicians insist, from the relativity we already trust to run our GPS. It goes like this. Since observers moving differently genuinely disagree about which events are simultaneous, and all of them are right, there can be no universal now sweeping through the cosmos like a cursor, deleting the past behind it. And if no universal now does the deleting, then the past is not deleted. All of spacetime simply exists, complete, the way all of Greece exists at once even though you can only stand in one village at a time. Nineteen twenty-six is not gone, on this view. It is elsewhere. Last summer is not gone. It is up the road, behind you, the way Delphi is behind you on the drive home, entirely real, just not your current coordinates.

Physicists argue about this picture, honorably, and I hold it lightly. But walking the empty streets on the morning we celebrate deleting a year and starting fresh, I found I did not want to delete anything, and the block universe gave me the language for why.

Because here is what the idea does to a life, if you let it. If the past is a place and not a verdict, then the good hours are safe. The August balcony nights, the taverna with the honey moon, my friend's confession on the mountain road, the hour that vanished at the piano, all of last year's entries in this notebook, they are not used up, burnt, receding into nothing. They are installed. Permanent addresses in the block, as real at this moment as this street corner, unreachable only in the way that a beloved village is unreachable from here, which is to say: still there, holding its light, indifferent to my distance.

And the hard hours are also just places. Not stains spreading forward through everything, not debts the new year must pay. Locations. Visited, survived, mapped, and now behind me on the road, at fixed coordinates they can never leave to chase anyone.

The man with the flowers turned up a side street. The cats supervised. I bought bread from the one bakery awake and ate the horn of it walking, which is the law.

A year does not end, I decided, somewhere around Exarcheia. A year is built, hour by hour, and on the first of January you do not erase the building, you top out one floor and start the next. The confetti in the gutters agreed, glittering like the Milky Way we drove out to see in November, which is also, come to think of it, old light from fixed places, still arriving, still shining.

Καλή χρονιά. Build a good floor.