The 2022 Nobel Prize in Physics was recently given to three physicists for proving in various ways that the universe is not “locally real.” Some of you reading this will know what this means, but for those of you who do not, what you need to know for this essay is that a series of experiments over the last decades have shown pretty conclusively that:
- “Locally” – (Extremely tiny) objects can cha nge their physical state in response to causes that are too far away to be able to communicate the cause. This is what Einstein referred to as “spooky action at a distance” – IE object A changes its state and this causes a change in the state of object B…except object B is too far away to receive information about the change in object A before object B actually changes
- “Real” – (Extremely tiny) objects have properties that exist independent of anyone perceiving those properties. IE an (imaginary and extremely tiny) apple is ripe whether or not anyone bites into it and discovers it is ripe.
It’s been almost 100 years since Einstein, Podolsky, and Rosen wrote a paper saying the idea that the universe was not locally real had to be nonsense. But in the intervening period, we keep proving over and over again that it appears NOT to be nonsense…yet it’s still a mind-blowing concept.
One major caveat which helps me sleep at night is the solid theory and evidence that this only applies to extremely tiny, completely isolated objects. In spite of all the popular science reporting on the Nobel this year saying things like, “The moon isn’t there until you look at it,” many physicists believe in something called “decoherence” which boils down to the fact that as soon as particles interact with each other, they become locally real. And since even the smallest particles are constantly interacting with other particles all the time, this would mean that something as enormous as an atom (let alone an ant, or a person, or the moon) is, in fact, locally real.
However, we can’t ignore the apparent fact that for extremely tiny, extremely isolated objects (IE the most fundamental building blocks of the universe), it does appear to be true that they are not “locally real.”
Which brings us to Wigner’s Friend. Again, this is probably familiar to readers who know their physics, but for those who don’t, here is a simple version.
You have probably heard of Schrödinger’s Cat. This is a thought experiment whereby a cat is placed in a box which also contains a device that will poison the cat if it is hit by a particle emitted from some decaying radioactive material inside the device. Since the emission of particles from decaying radioactive material is probabilistic (IE at any given moment there is only a chance the material may or may not emit a particle), until you open the box, the cat is simultaneously alive and dead.
This thought experiment is supposed to model what it is like measuring elementary particles. Until they are measured, they exist in multiple states at once. Once they are measured, they “choose” one of the states.
This is where the “real” part comes in: until you look at the cat/particle/moon, it is alive and dead, up and down, full and new.
The consequence of this has been a century of debate about whether or not consciousness is somehow “special” and somehow interacts with the physical universe.
All of this continues to be mind-blowing and anti-intuitive, but also continues to be proven repeatedly in a variety of increasingly complex and accurate experiments.
One of the more recent ones of these involves Wigner’s Friend. Wigner’s Friend is an extension of Schrödinger’s Cat wherein the person putting the cat in a box is, herself, inside a closed room with a friend standing outside the room. Wigner asked: if the person inside the room opens the box and sees the state of the cat, but their friend outside the room does not open the door to ask their friend inside what she observed, does the room itself now enter its own state of uncertainty that does not become “real” until the friend outside opens the door and asks what state the cat is in?
Unfortunately for our sanity, some scientists in Australia showed in 2020 that this does appear to be the case (again, for super tiny, super isolated objects)
That is to say that, on an even more complex level, “reality” does not appear to take shape until a conscious entity observes it. But the extra layer of weirdness in Wigner’s Friend is: whose consciousness? The scientist in the room with the box? Or her friend outside the room observing her friend? What about a third person outside that room? And so on… Whose consciousness determines the “realism” of the universe?
There are several competing theories of how to explain this. The classic one which is so popular in the press and which we are focusing on here is that somehow conscious awareness makes the universe real. A second is the Spider-Verse theory: every time even the smallest particle has a “decision” to make, new universes are created where every “decision” plays out (OK, it’s called the “many worlds” view, but still…) Another is called “superdeterminism” which says that the future state of every particle in the universe has already been determined by the initial conditions set at the start of the universe. A fourth says that the future can influence the past. A fifth, called QBism, says that the behavior of super small, isolated particles tells us nothing about the nature of reality. A sixth says there are as many realities as there are conscious frames of reference (IE the scientist in the room and her friend each cause their own reality “frame” to be “real” – see a good interview with Carlo Rovelli for this concept). And a seventh says we’re doing something wrong.
You can pick your poison and it took a while to get here, but today I read a paper from last week called, “Consciousness as Memory System” which is speculative but really fun…and next week we’ll dive into that and then mash some thought experiments together!