I see one world built in levels, from particles to minds, as The Ouroboros lays out. Space has always looked like the floor under those levels. Physics now hints that space may be a level too, and I find that fascinating.
The first clue came from black holes. In ordinary matter, the information a region can hold grows with its volume. In the 1970s, Jacob Bekenstein and Stephen Hawking found that a black hole’s entropy grows with its surface area instead. Entropy here measures how much information the black hole hides. The holographic principle turns that result into a proposal for any region of space. Everything inside could be described by information on its boundary, the way a flat hologram stores a three-dimensional image.
The strongest evidence is mathematical. In the late 1990s, three papers proposed that two model worlds describe the same physics. One is a universe with gravity inside anti-de Sitter space, a curved space whose infinite expanse can be pictured inside a snow globe. The other is a quantum theory with no gravity, living on the surface of that globe. Quanta Magazine calls this correspondence nearly a mathematical fact.
Our universe is not that snow globe. Its expansion is speeding up, which makes it closer to de Sitter space, with no obvious surface to hold the information. Physicists have tried for decades to stretch the correspondence to fit it, with limited success. So for our universe, holography stays a maybe.
If it holds, space may not be the stage the levels stand on. Space may be one of the levels, built from qubits, the basic units of quantum information. Sean Carroll and two colleagues sketched how ordinary space could emerge that way. In their model, strongly entangled parts sit close together, and unentangled parts sit far apart. Carroll calls the work “extremely preliminary and conjectural.” The idea fits the one world I see.
Put simply, space may be what quantum information looks like when you zoom out. Zooming out is also how I read emergence: each level is what the one below looks like from farther away. If space works that way too, even the floor is a level.