The Block Universe hypothesis suggests that time is a frozen block, and we experience change and the illusion of free will as we move from cross-section to cross-section. It’s the leading geometric model for how physicists treat time. Some days, I’m cool with that. Most days, I’m not. Today, I’m not. I’m not cool with the philosophical ramifications of the future being decided for us. Let the math be glorious. I don’t care. The vibes are off.
Does a vibe check sound less than serious to you? As a reason for exploring new paths, it’s perfectly reasonable. After all, that’s how Einstein’s discovery of General Relativity began.
There’s a theory in quantum mechanics called superdeterminism that suggests that everything was determined from the beginning. Entangled particles don’t have to communicate instantaneously across great distances because their states were chosen from the foundation of time. Physicists hate it.
If it seems odd that two fundamentally similar theories, the Block Universe and superdeterminism, should have had vastly different receptions, the difference is the intended audience. The Block Universe flows naturally from General Relativity, and those who work math on such cosmic scales aren’t really concerned with the philosophical difficulties. If it works, go with it. Meanwhile, superdeterminism neuters the quantum physicist by eliminating measurement independence and turning probability into a shell game.
There’s another attempt to explain away “spooky action at a distance” known as the theory of retrocausality. It states that when an entangled particle determines its spin, that causes its entangled mate to choose the opposite spin in the past. Physicists hate it too.
On the other hand, within string theory, black hole physics, and quantum gravity, physicists are fans of an idea called the ER = EPR conjecture. When there’s no observational proof, physicists stick to what produces the best math. Right now, ER = EPR isn’t something they can test, but it’s a useful mathematical analogy. As for the vibe check, this one’s a winner, and when I think of how spacetime is constructed, this is the model I use.
It’s called a conjecture. I’d assumed that was something weaker than a hypothesis, but the opposite is true. A hypothesis starts as an idea, and it can be called a hypothesis before you ever test it or gather evidence. This is called a conjecture because it’s backed by strong theoretical clues but lacks a logical proof.
The name stands for Einstein-Rosen bridges = Einstein-Podolsky-Rosen, or in other words, wormholes equal quantum entanglement. According to the conjecture, when quantum particles are entangled, they’re connected by a microscopic, non-traversable wormhole.
Now, if that’s all it was, I wouldn’t care much, but it’s much more than an idea for how entangled particles communicate. It suggests that the geometry of spacetime is entirely made of entangled particles and the tiny wormholes that connect them. That’s exciting, because when we say that mass curves the geometry of space, what does that even mean? No theory suggests there’s a pre-existing grid onto which spacetime secures itself. General Relativity tells us that spacetime is that grid. It’s not laid out on top of anything. With ER = EPR, we have actual nodes and lines that shape an emergent geometry of space and which are logically impacted by mass and energy. It’s beautiful.
I need to clarify my point on “nodes and lines” as I’m not suggesting the wormholes form a grid as we visualize it. Outside of gravitational pull, the underlying structure of spacetime is most likely frothy, more akin to the drool of a rabid dog than the iron pillars we use to construct a building. It’s also simply messy to refer to the wormholes as lines which, however you twist them, still sounds like a a filament through space. The wormholes are space, and they aren’t stable filaments but shifting probabilities of connection between the entangles pairs.
Vastly important for this particular discussion, because ER = EPR sees space and time as emergent properties, the present can be seen as the current configuration of the quantum network. Space and time are macroscopic illusions. If we view time this way, it’s generally labeled under the philosophical concept of presentism, but that term has baggage. The complexity of wormholes work like the rings of a tree, revealing their age. Philosophical presentism would ask why the present would carry a history of the past if only the “now” is real, but that’s nonsense. Whether through fossils or baryon acoustic oscillations, the past leaves its mark on the present. The past and the future simply do not exist in a higher dimensional expression of our reality.
Variations of presentism are also challenged by General Relativity. If the present is local and relative, which “now” are we referring to if only the “now” exists? If the ER = EPR conjecture is right, spacetime is fluid. Our issues with simultaneity stem from an attempt to conform a fluid reality to a rigid graph.
There’s no need for quantum particles to travel back in time or for all of existence to be predetermined. Space and time are illusory, but wasn’t that always the case? What’s given a chance to be substantial is what it means to be human. That’s not an illusion.
The conjecture does create problems, however.
When physicists say that the present, past, and future all exist at the same time, they’re referring to that Block Universe hypothesis. This coordinate plane of time seems necessary for gravity to be a result of mass bending spacetime, a core principle of General Relativity.
Hopefully, in future essays, we’ll deal with the proper theories that attempt to resolve this. For now, allow me to share my thoughts. First, the problem I described is with presentism, and I’ve said that has baggage. It seems very different to me to suggest that the future and past do not coexist with the present than it is to suggest the present is all there is. That difference is exemplified in presentism’s confusion over the present containing a record of the past.
In what I’ve described above, the past isn’t a physical space, but it used to be. It’s a chain of prior quantum configurations, what we experience as a memory-chain of lived moments. The future isn’t the next fixed coordinate but a multitude of probabilities.
What I called a “memory-chain” isn’t dependent on us as conscious observers. Quantum Darwinism is a theory of time where the environment stands witness to quantum states. It’s a redundancy of recorded history that allows multiple observers to agree on an objective past without ever having observed the quantum states directly. It’s a memory-chain created not only in our subjective mental recall but across the universe in the evidence it’s left behind. We’re used to this on a macro scale. The striations of the earth stand witness to past floods and geological violence. Fossilization captures a record of past species. BAO are the remnants of ripples through the early universe. On a micro scale, scattered photons are an example, bearing witness to a former quantum state.
Lose all the baggage. The “now” is not universal. Relativity is real, and in a universe built on superposition and entanglement, we don’t need to imagine a frozen construct of time to make relativity work. That’s always been a convenient simplification.
Time is bent by the process of mass slowing it down. If we’re stuck imagining time as a physical thing that exists and which contains essential measurements, then clocks ticking differently and the warping of spacetime become puzzles that require philosophical assumptions to solve. If time is an emergent property of a universe structured through entanglement, I see gravity working exactly as Einstein said, but with mass changing the rate of information processing in the local quantum network. We saw a little of that in the first essay when we discussed the Entropic Gravity hypothesis.
ER = EPR was proposed by Juan Maldacena and Lennard Susskind in 2013. Quantum complexity was proposed by Leonard Susskind, Adam Brown, and Bran Swingle in 2014. Quantum Darwinism was first proposed by Wojciech H. Zurek in 2003. Presentism was first conceptualized by Aristotle around 350 BCE.
I don’t meant to call Aristotle’s ideas nonsense. What frustrates me is the lumping of an attempted exploration of reality with a predefined framework and then discounting that exploration because of the faults found in the framework. It’s a logical fallacy and an example of either a Straw Man Argument or Guilt by Association.
As one final point, the Block Universe is also known as eternalism, and I want to reiterate that it is the leading hypothesis. While I see it as a mathematical convenience, someone once said eternalism was proven by gravity waves. This is not the case because gravitational ripples require four-dimensional spacetime but not a future that currently exists elsewhere. I believe the logical leap comes from assuming four-dimensional spacetime necessitates a block universe, and so, if he were really saying gravitational waves prove four-dimensional spacetime, I agree. Physicists may talk about the about the Block Universe as if it were established fact without actually using those words, but that’s different. They’re not required to hedge everything they say, and while it may blur the line between popular theories and established fact, it’s less confusing and provokes the imagination with possibilities, hopefully inspiring a new generation of physicists.
— Thaddeus Thomas
P.S. All corrections welcome.
Find all my essays on physics here.
COMING SOON: In physics, the exploration of ER = EPR will continue for two more weeks with postings each Thursday morning. In writing-about-writing, now that I’m back in town, I’ll start posting chapters of my book on the art of prose. However, that doesn’t meant I have a start date or a schedule. My plan is to edit chapter one and post early next week, but that’s not a promise. In fiction, I’m encouraged to return to my short story WIP and hope to start publishing fiction again soon.