I was just thinking.
Not about anything in particular at first. Just about how much we know. Physics can predict the position of a particle to ten decimal places. We built machines that split atoms. We detected a ripple in spacetime from two black holes colliding a billion years ago. We know an almost absurd amount about how reality works.
And then the thought that stopped me: knowing how something works is not the same as knowing what it is.
I kept coming back to this image. A perfect railway. Runs everywhere, never fails, you can predict every arrival time, you can write the entire manual. But you have no idea who built it, why it exists, or what is underneath the tracks. You just ride it.
That is basically physics right now. The Standard Model — the best theory we have — describes every particle and force in the universe with extraordinary accuracy. And it cannot tell us why the fundamental constants have the values they do. It cannot incorporate gravity. It does not explain 95% of the universe, which is dark matter and dark energy we cannot see or touch. The manual is complete. The builder is unknown.
What made this weirder to me is that physics does not have one railway. It has two. And they are incompatible.
General Relativity — Einstein's theory — handles the large. Planets, galaxies, black holes, the shape of spacetime itself. It says gravity is not a force, it is a curve. Confirmed by everything we have ever tested it against, including gravitational waves detected in 2015, exactly as Einstein predicted in 1916.
Quantum Mechanics handles the small. Particles, atoms, the behavior of matter at the deepest level. It says nothing has a definite position until you look at it. Reality between measurements is a blur of probabilities. Also confirmed by everything we have ever tested it against. The phone in your pocket works because quantum mechanics is true.
Both perfect. Both right. Mathematically incompatible with each other. After a hundred years, nobody has resolved this.
Everyone knows Einstein hated quantum mechanics. His line about God not playing dice is usually presented as a great man being stubborn. I do not think that is the right reading.
Quantum mechanics — specifically the Copenhagen Interpretation that became standard — basically says: stop asking what is really happening. Just calculate probabilities and predict measurements. The physicist N. David Mermin coined the phrase "shut up and calculate" in a 1989 Physics Today article as a sharp summary of that attitude — a characterisation so apt it has since become the phrase physicists reach for, even though it originated as a critique from outside the tradition rather than a slogan from within it.
Einstein's problem was not that he was old. His problem was that he thought science was supposed to tell you what is actually real, not just predict numbers. He spent thirty years looking for something underneath. He failed. But the question he was asking still has no answer. We can predict everything. We can explain almost nothing. He was probably wrong about the solution. He was arguably right that something is missing.
Here is where my thinking got strange and I only later found out it was not original.
A circle is perfect in two dimensions. A sphere is perfect in three. But a circle is also just the shadow of a sphere — what a sphere looks like to a creature that cannot perceive depth. The circle looks complete. It does not know it is a shadow.
What if our four dimensions work the same way? What if General Relativity and Quantum Mechanics only look incompatible because we are the creature looking at the shadow?
I thought this was just a thought. Then I found out that Theodor Kaluza first proposed exactly this in 1919 — sending his manuscript to Einstein, who praised it but held back from endorsing publication for two years. The paper finally appeared in 1921. He had added one extra spatial dimension to Einstein's equations and gravity and electromagnetism unified automatically. No extra assumptions. Just fell out of the math. Einstein was so taken with it he worked on it himself for years. The extra dimension was too small to detect, but the idea was too elegant to dismiss. String theory later extended this to ten or eleven dimensions. The holographic principle goes further and suggests our entire three-dimensional reality might be a projection from a two-dimensional surface.
Plato said something like this around 380 BC — prisoners in a cave seeing only shadows on a wall, mistaking the shadows for reality. The oldest version of this exact idea.
I do not know if any of this is right. Neither does anyone else.
John Wheeler — the physicist who popularised the term "black holes," giving it scientific authority and wide currency from the late 1960s onward (the term itself had appeared in print as early as 1964; Wheeler later credited an unnamed audience member with first suggesting it to him) — spent his last years on an idea he called It from Bit. He wrote it up in a 1989 paper. The idea is that everything physical — every particle, every force, spacetime itself — is at the most fundamental level not matter or energy but information. Yes or no answers. Binary choices. Reality as code.
If that is true, then the railway is not made of steel. It is made of code. Which raises the question: who wrote it.
DNA is the closest thing I can point at. A four-letter molecular code that builds eyes, kidneys, a nervous system capable of wondering about itself. The body never reads the code. It just runs. If information is the foundation of everything, we are all just living inside something that runs without reading its own source.
As far as I can tell there are three possible answers to who built the railway.
The first is nobody — it is random. An infinite number of universes exist with different rules, and we are in one that happened to permit stars and chemistry and people asking questions. Hugh Everett proposed the branching universe idea in 1957. The modern multiverse concept grows from that.
The second is that the constants are too precise to be random. Fred Hoyle noticed in 1953 that carbon exists abundantly in the universe, which meant there had to be a previously unknown nuclear energy resonance in carbon-12 at just the right level — and he predicted that resonance before it had been measured. He was right; it was confirmed experimentally within months. The prediction was a genuine feat of reasoning. Later writers, particularly after the anthropic principle gained currency in the 1980s, have retrospectively framed this as evidence that the physical constants are arranged for life — though whether that framing is warranted remains contested. Nobody has explained why the constants are what they are. They just are, and if they were slightly different, nothing would exist.
The third is that code has a coder. Nick Bostrom argued in 2003 that if future civilizations can run detailed simulations, the simulated minds would eventually outnumber real ones by so much that being in a simulation is statistically probable. This is not science fiction. It was published in a philosophy journal and taken seriously.
Physics can describe the railway in extraordinary detail. Physics cannot tell us which of these three is true. That is not a failure — it is just the honest edge of what we currently know.
I am not a physicist. I followed these questions without knowing where they would go and ended up somewhere that turned out to have names and papers and serious people who have been sitting with the same uncertainty for decades.
I do not have a conclusion. I do not think there is one yet.
The railway runs. I ride it every day. I still do not know who built it.