The line that has outlived both of them sits near the end. Now he has departed from this strange world a little ahead of me. That means nothing. For us believing physicists, the distinction between past, present, and future is only a stubbornly persistent illusion.
He died four weeks later.
Did he believe what he wrote, or did he need to? Maybe both. Maybe there is no honest version of the sentence in which the two can be separated.
The physics behind the line is real. Special relativity does something strange to time. What I call "now" and what someone moving past me calls "now" can include different events. There is no universal present. This is not theoretical. Your phone's GPS works because the satellites overhead are corrected for relativity. Their clocks tick a little slower than yours, and the math knows it.
The strange part is not that clocks can disagree. It is that if two honest observers can disagree about what is happening right now, then right now is not something fundamental. It is a vantage point.
Hermann Minkowski, Einstein's teacher, said in 1908 that space and time were doomed to fade into mere shadows of a single thing. Hermann Weyl put it more plainly: the objective world simply is, it does not happen. Fifteen centuries earlier, a Roman philosopher named Boethius, writing in a cell while awaiting execution, said that God did not foreknow anything. God simply heard the entire symphony at once, the way a composer hears the whole piece when reading the score. The musicians performing it can only hear the bar they are in. The universe appears to have only so many shapes. We keep finding them.
This is what physicists call the block universe. Not that the universe unfolds, but that spacetime exists as a whole, with us moving through it from the inside. Imagine your whole life not as a movie being watched but as the film itself. Every frame is there. The child you were. The parent you are now. The old person you have not yet become. Consciousness is the light moving through the reel.
In this view, the universe is a four-dimensional object. Every moment of your life, and every moment of the lives of everyone you have ever loved, is a fixed coordinate in that object. The past has not gone anywhere. The future has not arrived from somewhere else. They are simply elsewhere in the same structure you are in.
My kids are ten and seven.
At breakfast this morning Avery was asking me a question I half-answered while pouring milk, and Ford was making a face I have seen a hundred times and will eventually forget. There was a small argument about whose turn it was for something. The light was at the angle it only has for a few minutes a day. They were moving through the room with the careless immortality of children who do not yet know they are vanishing.
Tomorrow they will be almost the same, but not exactly. A little older. A little farther from the versions who sat there today. By next year I will not be able to remember how Avery was holding a fork this morning, or what Ford's hair looked like before it had been brushed. Those children are already partly gone. The next ones will arrive in their place, and I will love them too, and I will lose them too, and I will not notice the transitions while they are happening.
If the block universe is right, the children at the table this morning are not erased by tomorrow. They remain at that table, in that light, with those faces. Every age my children will ever be is there too. Their old age. Mine. Not waiting somewhere. Already there, in places we cannot reach from here. We do not get to go back. That is the wound. But the place itself is not destroyed. That is the mercy.
My grandparents remain in the kitchen I visited as a child. The boy I was at twelve is still pedaling home down a Sussex County road in the summer dusk, somewhere I cannot reach. The morning is still coming through the window of a home I have not lived in for over twenty years. These are not memories. They are still there. They are located.
When you look up at a star tonight, the light entering your eye may have been traveling for years, for centuries, for longer. You are not seeing the star as it is now. There is no clean universal now to appeal to. You are receiving an old signal that has only just become present to you. Everything you have ever loved in a version you cannot get back to is in the same condition as that star. Still emitting. Still there. Just outside the moment you are in.
I hold this idea the way you hold any big idea: lightly, but unable to set it down.
The hardest part is what it means for choice. If every moment of my life is already a fixed coordinate, then the decision I will make tomorrow is, in some sense, already there. My experience of weighing it, hesitating, and choosing is real, but real in the way a musician's experience of playing is real. The score exists in its entirety. The playing is only how it feels from inside it.
I notice I do not like this. I notice I want my deliberation to actually be deliberating something. I do not know whether my discomfort is information about reality or only information about my preference.
The honest position is that the math does not decide. Some physicists hold the block view. Others believe time genuinely flows. The experiments have not chosen between them. It is at least possible that determinism and free will are not the opposites we have been told they are. The path could already be laid down in the structure and the walking could still be ours, in a way our language for ours is not yet good enough to describe. Maybe freedom is just what choosing feels like from within the only structure we ever inhabit.
Sometimes I try this on the people I love most.
I have tried, at the breakfast table, to actually see it. To look at the two of them, Avery half-listening to me, Ford making the face, and hold the thought that this room is being laid down permanently into something. That the morning is not a thing that will be over. That it is a place.
I cannot hold it for long. Maybe four or five seconds. Then the dishwasher needs unloading, or someone spills, or I am already mentally somewhere else in the day. The stubbornly persistent illusion is exactly that. It does not yield to argument. It does not yield to physics. It barely yields to four seconds of deliberate looking.
But for those four seconds, something happens. The two of them go from people I am going to lose to people I am, right now, recording into something that does not contain the word over. The room thickens. The faces become exact. I am not paying more attention; if anything I am paying a different kind of attention, the way you look at a painting you have decided to memorize. Then it ends. Someone asks for more milk. I get up. The illusion comes back.
I do not know whether what I touched in those seconds was reality or whether it was just a story about reality that briefly held. But I know I will keep trying.
So what was Einstein doing in that letter?
Two things at once, and I do not think they can be cleanly separated. He was telling a grieving family the most rigorous consolation his physics could offer, that the husband and father they had lost was not nothing, not gone, was located elsewhere in a structure that did not contain a category called vanished. And he was telling himself. He had spent fifty years convinced of a picture of reality in which the most painful thing humans do, losing each other, was an artifact of perspective.
The phrase he chose is precise in a way I admire. A stubbornly persistent illusion. Not just an illusion. Stubborn. Persistent. Not the kind you can argue yourself out of. The kind that holds, and keeps holding, no matter how much physics you know. Time feels like flow. People feel like they leave. We walk forward and the rooms behind us feel empty. The illusion, if it is one, is industrial-grade.
Try it, the next time you sit across from someone you cannot bear to lose. Try thinking they are coordinates. That this breakfast, this conversation, this ordinary morning, is being laid down into a structure that does not contain the word over. That the room you are in right now is already permanent, in a place you will not be able to get back to but which will not stop being there.
Maybe the universe is an object and nothing is ever lost. Maybe time genuinely flows and the people we have loved are gone. Maybe the answer is something neither side has imagined. I find I keep returning to the first, the way you return to anything you cannot quite stop wanting to be true.
When I look up at a star whose light is older than my country, I let myself believe, for as long as the looking lasts, that this is what looking at anyone I have ever loved would be. Reach across the structure. Receive an old signal. Refuse, for a few seconds, to be moved by the part of me that is sure the structure is not there.
I keep looking up. As if every kitchen I have ever lived in is still lit from inside. As if my children, ten and seven, are still at that breakfast table. As if Avery is still half-listening, Ford still making the face, the light still at its few-minutes angle. As if love has coordinates.