A physicist, a computer scientist, and a banker walk into a bar. They cannot agree on who got there first.

This is not a joke. This is a central problem of physics, computer science, and economics.

The physicist points out that simultaneity is relative — who was there "first" depends on the observer’s velocity. The computer scientist notes that their phones’ clocks differ by milliseconds, enough to corrupt a database. Who knows which clock is accurate? The banker shrugs and says it doesn’t matter who got there first; what matters is who pays first.

They are all concerned with the same problem: What we call "first" is not the result of the flow of some river of time that carries us forward, washing us up on its banks. Time itself is a cost — the price we pay when two otherwise isolated systems must agree on what happened.

Whether you are collapsing a quantum wavefunction, synchronizing a distributed database, or clearing a wire transfer, the mechanism is identical. To understand how, we have to let go of our intuitions about time and reexamine its machinery.

The Illusion of a Universal Clock

Our intuitions about time go back to Isaac Newton. He imagined time that "flows equably without relation to anything external" at the same rate for everyone, everywhere. On this view, the universe is a synchronous computer, every atom updating its state on the exact same clock cycle.

Einstein broke this clock. He showed us that time is relative to velocity with light setting the absolute speed limit. Then quantum mechanics revealed to us that at a small enough scale, even properties like "position" and "momentum" cannot be known until measured. This left us with a startling question: if there is no universal clock, then how does the universe keep its story straight? How does a photon know to hit the detector after the laser fired?

The Physicist’s View: Time is Entropy

In 1993, Carlo Rovelli proposed a radical idea: time is not a fundamental variable of the universe. At the microscopic level — individual atoms interacting — there is no "past" and no "future." There is only a network of correlations. Rovelli has showed that what we perceive as "time" is actually a measure of our ignorance.

Consider a perfectly isolated system — a single photon bouncing between two perfect mirrors. As long as it remains isolated, no information leaks out. The system is reversible. It generates no heat. In a very real sense, time is not passing for that photon. It exists in a "lossless limit," a suspended state of unitary evolution where past and future are symmetric.

Time begins when the photon hits a detector.[1]

How? Because the detector clicked. To click, the detector had to change its state irreversibly. It generated heat. It increases the entropy of the room. This dissipation left its mark on the universe — a thermodynamic record.

This leads us to a profound truth: we pay for reality to unfold with entropy. The reason we can say "Event A happened before Event B" is because we turned energy into entropy in recording it. The flow of time is the thermodynamic cost of verifying the universe’s status.

The Computer Scientist’s View: Time as Messaging

Over a decade before Rovelli began dismantling time in physics, the computer scientist Leslie Lamport was doing the same thing in computer science.

In 1978, Lamport published one of the most important papers in computer science history. He was solving a practical problem: how do you get a cluster of computers to agree on which transaction happened first? If Computer A is in New York and Computer B is in Tokyo, the speed of light guarantees a delay between them. If both update a database at roughly the same moment, who "wins"?

Lamport realized that in a distributed system, physical timestamps are useless. You cannot trust the clock on the wall because synchronization is never perfect.

Instead, he defined time as a partial ordering of events. We can only say "Event A happened before Event B" if there is a causal link — a message — sent from A to B. If I write a letter and you receive it, my writing happened before your reading. If I eat breakfast and you eat breakfast and we never communicate, our breakfasts are concurrent. There is no fact about which happened first.

This is the same answer given us by quantum mechanics. In the absence of an interaction (a message), systems are concurrent — superposed. They share no timeline.

Time, for Lamport, is not a background variable. It is a directed graph of messages. Time is what happens when we communicate.

The Banker’s View: Money is Memory

This brings us to the banker’s view of markets and money.

If the universe is a distributed system without a global clock, then the economy should be a complete disaster. Billions of human "nodes" — buyers and sellers — operate concurrently, each with private desires, private assets, private histories. How do we synchronize our activity? How do we prevent the double-spend problem, where I trade my only chicken for your shoes, then trade the same chicken for a neighbor’s bread?

In a primitive barter economy, synchronization required a handshake — a direct interaction between two people. This is a private reality. If I promise to pay you later, that debt exists only in our shared memory, a "relative fact" in Rovelli’s language. But as the economy scales, we need a way to make private facts public. We need a global clock. We call that clock money.

In 1998, the economist Narayana Kocherlakota showed that if we had a perfect, magical distributed database everyone could access instantly — a universal ledger recording every favor and debt in history — we would not need money. If I wanted your shoes, I wouldn’t hand you a green piece of paper. I would take the shoes, and the Great Database would update my status to "Owes Society Value" and yours to "Owed Value." We use money because we lack that magic database. To put it in the physicist’s terms: we have high observational entropy about each other.

Observational entropy measures what remains hidden given the coarseness of our measurement — and when I meet you on the street, my "measurement apparatus" for evaluating your history is crude. I cannot access your past transactions, your reputation, your debts. You are, to me, a superposition of trustworthy and untrustworthy until I have some way to collapse that uncertainty.

Money mediates that collapse. Instead of verifying your entire past (computationally expensive), I verify your token. If you have the dollar, I assume you earned it. The dollar is a physical proof-of-work, a compressed artifact of your history that substitutes for the fine-grained knowledge I cannot access.

The Synchronization Tax

When you swipe your credit card, you witness the collision of these three worlds.

First, concurrency: you and the merchant are two systems with undefined relative states. You want the coffee; he wants the value.

Second, interaction: you tap the terminal. A message is sent. You are attempting to establish a "happened before" relationship—payment, then coffee.

Third, collapse: the banking system acts as observer. It checks the ledger. It dissipates energy (servers running, fees charged). It forces the universe to decide: did this transaction happen?

Once the bank approves, uncertainty collapses. The money moves. The coffee is yours. Private desire has become public fact.

There is a non-trivial sense in which banks, lawyers, and stock exchanges all exist for this reason. They are the decoherence machinery of society, the "classical limit" that prevents the economy from remaining in an unresolved superposition of fraud and promises.[2]

But this coherence costs us something. In physics, we pay with entropy. In finance, we pay with fees. Every transaction fee, every spread, every billable hour is a synchronization tax — the energy required to force two asynchronous human beings to agree on a shared reality.

The Luxury of the Present

We resent these costs. We hate the fees. We hate waiting for wires to clear. We hate the feeling that time is running out. But perhaps we should understand all of these experiences in a different way. That we share a "now" at all is a miracle of engineering.

In the lossless limit — in the deep silence of an isolated quantum state — there is no time, there is no reality, only a lonely possibility of what might be. To have a reality — a coffee, a conversation, a career — we must interact. We must pay the entropy tax to synchronize our lives with those around us.

Time is not a river that carries us. Time is a bridge we build, transaction by transaction, over the void.

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Things get more complicated when the photon is entangled with another system. Remarkably, it is possible to detect the presence of an object — even a bomb — without the probe photon ever being absorbed by it. See Kwiat, P. G., White, A. G., Mitchell, J. R., Nairz, O., Weihs, G., Weinfurter, H., & Zeilinger, A. (1999). High-efficiency quantum interrogation measurements via the quantum Zeno effect. Physical Review Letters, 83(23), 4725–4728. Available at https://arxiv.org/abs/quant-ph/9909083 ↩︎ 1.

The Coase Theorem describes the lossless limit in which every transaction is reversible. Oliver Williamson’s asset specificity describes entanglements, in which the separation of firm and asset generates entropy. Firms, on this view, represent a coherent domain in which people share a common clock: the rules, norms, and hierarchy that manifests in culture. The synchronization tax is reduced through shared context. ↩︎