Physics blackboards are where ideas first take shape — before they turn into theories, papers, or Nobel prizes. The sound of chalk scratching against the board is not just noise; it’s the heartbeat of thinking. Alejandro Guijarro understood this better than most. For three years, he traveled through the world’s best quantum physics institutions — Cambridge, Stanford, MIT, Oxford, CERN — photographing the blackboards right after lectures ended. No professors, no students, no explanations. Just the silent remains of thought, still hanging in the air, waiting to fade into dust.
At first, these photos look messy. Erased equations, overlapping symbols, fingerprints, and chalk dust everywhere. But if you look carefully, you see they are traces of thought. A line begins somewhere, then a small symbol changes its meaning. Some equations stop halfway, as if the physicist gave up or moved on. But that is the real face of science — unfinished, always erased and rewritten.
Quantum mechanics is a strange world. A particle can be here and there at the same time. A cat can be both alive and dead. Feynman once said, “Nobody understands quantum mechanics,” and he meant it. Guijarro’s boards are the visual version of that confusion. The more you try to understand them, the more you get lost. But there’s beauty in that chaos because every mark shows a search for meaning. Even if you don’t get it, you can still feel the effort.
A blackboard is like an MRI of a scientist’s brain. You can see the mind working. For mathematicians, the board is not a tool, it’s an extension of thought. The pressure of the chalk, the rhythm of the writing — it all carries emotion. Somewhere you can see anger, somewhere an “aha!” moment. A small finger swipe might show the exact second someone changed their mind.
Somewhere in those photos, you can almost smell the chalk. And not just any chalk — the legendary Hagoromo. The one mathematicians talk about as if it were holy. Smooth, dense, perfectly balanced between friction and flow. It doesn’t crumble like the cheap ones; it glides. People say a line drawn with Hagoromo feels like silk. When Guijarro photographed those blackboards, chances are most of the equations were written with it. There’s something poetic about that — the finest ideas of modern physics, drawn with the world’s most elegant piece of calcium carbonate. Even the dust it leaves behind has a kind of dignity.
Erasing is the most fascinating part. Wiping a board is not forgetting — it’s making space for a new idea. Every layer stays underneath. Guijarro’s photos show these layers stacked together like memories. The ghosts of old thoughts are still there. Some boards are so dark it feels like years of thinking have soaked in. Maybe quantum itself is like that — everything overlapping, nothing completely gone.
What Guijarro does is simple: he looks. Those equations, once removed from their classrooms, stop being about science and start being about form. The lines, the waves, the chalk marks — they have rhythm. The boards start to look like galaxies, clouds, or landscapes. These are not science photos anymore; they are about the beauty of thinking.
Jessica Wynne thought along similar lines when she created Do Not Erase: A Beautiful Collection of Mathematicians’ Blackboards. Her book isn’t about art either — it’s about the strange intimacy between a mathematician and the surface they think on. The boards in her photos are full of unfinished equations, scribbles, notes to self, and little drawings, just like Guijarro’s. They feel alive. Wynne once said that mathematicians treat their blackboards the way writers treat their notebooks — personal, messy, irreplaceable. When you see those layers of chalk, you realize that the blackboard isn’t just a tool. It’s a diary of thought.
Sometimes, the marks weren’t even made by scientists but by janitors cleaning after lectures. A simple act of wiping becomes art. The movement of the eraser, the balance of the surface — it all tells a story about how knowledge is made: write, erase, fix, rewrite. Nobody really knows what the final result will be.
Guijarro’s Momentum series reminds me that knowledge isn’t clean or perfect. It’s messy, smudged, rewritten, full of mistakes. Even the famous “eureka” moments are built on hundreds of erased lines. You can’t capture those moments — but you can see their traces.
That’s what these photos really are: not science, but the anatomy of thought. The blackboard becomes a mirror of the human mind. Each equation is a shadow of an idea, and each eraser mark is its rebirth.
In the end, all that remains on these physics blackboards is chalk dust — the quiet residue of human thought. It settles, drifts, and clings to the surface like memory. But it never truly disappears. Maybe knowledge itself is like that — a cloud of unfinished ideas floating above physics blackboards everywhere, waiting for the next mind to pick up the chalk and continue the story.
