Every moment already exists

September 1908, a lecture hall in Cologne. The mathematician Hermann Minkowski tells a room of scientists that from now on space by itself and time by itself are doomed to fade into shadows, and only a union of the two will keep any independent reality. He had taken Einstein's special relativity, three years old at the time, and seen what the equations were actually saying. Einstein had been his student and at first called the geometric version superfluous learnedness. Within a few years he had built general relativity on top of it.

What the math says

Plainest version. Relativity shows that two people moving relative to each other will disagree about which far away events are happening at the same time. For you, standing still, something on Mars is happening right now. For someone passing at speed, that same Martian event is still in the future, or already done. Neither of you is wrong. There is no master clock to appeal to.

But if there is no fact about which distant events are happening now, there is no privileged now at all, and if there is no privileged now, nothing is special about the present. Every moment, the Battle of Hastings and your breakfast and your great grandkids' funerals, is a location in a four dimensional block, as real as every other. We experience the block one slice at a time, the way a needle experiences a record, and we call the slice now. The record does not know about the needle.

Philosophers call this eternalism, or the block universe. Hilary Putnam gave it a formal shove in 1967 and it is still the default reading of relativity among physicists, with a loud minority dissenting. Einstein took it personally. Writing to the family of his oldest friend a few weeks after the friend died, and a month before his own death, he said that for people like them who believed in physics, the distinction between past, present and future had only the meaning of a stubbornly persistent illusion.

Why it is on this shelf

The oldest claim in this library is that the sky at your birth has something to do with you. Every serious critic since Cicero has made the same move: that moment is gone, so how can it act on anything? The block universe does not answer that. It deletes the premise. The moment is not gone. It is a few decades back along your world line, exactly as real as the one you are sitting in, and the arrangement of planets at that moment is a permanent feature of the block, like the shape of a mountain.

That does not make astrology true. Nothing in the geometry says the shape of that mountain means anything. What it does is take away the cheapest objection, the one from vanished time, and leave the real one standing: is there a connection between that arrangement and this life, or only a coincidence people have been dressing up for twenty five centuries? That is Jung's question and physics just handed it back without opening it.

What is still open

Not everyone buys the block. Some physicists argue the flow of time is real and relativity simply cannot see it. Some think quantum mechanics, where the future looks genuinely undecided until measured, breaks the block into a growing one: past fixed, future not yet there. Carlo Rovelli argues time as we feel it is a product of our ignorance, a thermodynamic blur, and the fundamental equations do not contain it at all.

Honest status: the best theory of space and time we have strongly suggests all moments are equally real, nobody has squared that with how time feels, and anyone certain either way is ahead of the evidence. For this site's question, that is plenty. The order of the cosmos, in the modern picture, is not a sequence that passes. It is a shape that stands. Pythagoras would have nodded.