In my first months as a physics journalist nearly a decade ago, I kept running into an inscrutable string of characters: Ad S/CFT. Thoroughly intimidated, I decided to just ignore it. But I soon learned that those characters are shorthand for a surprising connection between the seemingly inharmonious worlds of gravity and quantum mechanics. This broader idea is known as the holographic principle, and it now strikes me as the most profound proposal in theoretical physics in the last 30 years. Theoretical physicists tend to vote with their feet, and Ad S/CFT sparked a stampede. The three foundational papers on the topic in the late 1990s have garnered tens of thousands of citations, making them by far the most highly cited theoretical physics works of the digital era.

In my interviews with physicists who study holography, they often seem genuinely stunned, and reach for words like “magical” and “miraculous” to describe it. And it doesn’t hurt that holography led to a widely accepted answer to the most famous puzzle in physics: Contrary to what Stephen Hawking argued, black holes are not inescapable prisons. But even after covering numerous developments in holography, I still felt confused. I had heard that holography suggested that gravity and quantum mechanics are one and the same, and that space might be an illusion.

The holographic principle asserts that no matter what’s going on inside a box of space — from gas molecules to black holes colliding — you can decipher the entire contents just by repeatedly measuring points on the surface. It asks us to erase the categorical difference between square meters and cubic meters. Bartek Czech, a theorist at Tsinghua University in China, highlights the power of the principle by comparing it to a CT scan of the brain: holography implies that you can reconstruct every fold, vessel, and neuron without actually looking inside. Why would anyone entertain such a far-fetched notion? It appears to trace back to one force: “a miracle of gravity,” Czech said.