Why Quantum Mechanics Tells Us That Nothing Exists By Itself
If you leave a chair in a room and step outside, does the chair still exist? Many people would probably respond, "What's wrong with you? Of course, it does! I'm not an infant failing an object permanence test." And how about the proverbial tree in a forest? If it falls, and no one is around, does it make a sound?
Such a question might have been once used as a thought prompt, but the actual answer is: no, it doesn't. Sound, like all sensory information, is a byproduct of the interaction between the body and the environment. It's an emergent property, much like consciousness itself. A tree falls, and the collision emits a waveform captured by the ear. It really is the case that sound, sight, smell, touch, and taste do not exist outside your own neurochemistry and skull.
This is the kind of thinking that can prime your mind for dealing with discussions of quantum physics and its ever-increasingly ambiguous nature of reality. Long before movies started chucking out "quantum" as a sci-fi buzzword (per YouTube), or IBM started constructing "superconducting transmon qubits" to build quantum computers (dive in on the IBM website), traditions such as Daoism and Zen Buddhism have described the universe as an indivisible, whole entity, while empiricists like Aristotle, Hume, and Locke taught us that observable reality constitutes ultimate truth.
And now? Such philosophies, modern neuroscience, and quantum physics are all coming together to arrive at the same conclusion: everything does (and doesn't) exist.
To be or not to be? Yes
So would you like a pizza or a sandwich? The most logical answer is: yes. (English doesn't have an inclusive "or" conjunction, as this discussion on Linguistics describes.)
This is a linguistics version of the old Schrödinger's cat puzzle, which is usually most folks' jumping on point for learning about quantum physics. Austrian physicist Erwin Schrödinger first postulated the puzzle back in 1935 to poke fun of existing physics set forth by Einstein, Bohr, Heisenberg, and more (per Science Direct). Like any good story, Schrödinger's quip (as it maybe ought to be called) has revealed truths about our physical reality that not only seemingly violate rules of classic physics, but also some of that good, old "empirical" common sense that leads us to think, "Sure, that chair is still there when I leave."
The problem is this: classic physics is deterministic. That is to say, built on predictions. See this ball? If I throw it over there, it will land on the ground. See that ball on the ground? It's there because I threw it there. Nice and tidy. The only problem is, classic physics doesn't apply to subatomic particles. We can't know both the location and velocity of an electron, and per quantum physics, its direction isn't known until measured: it's either in an "up" superposition, or "down." And like Schrödinger's cat in a box exposed to radiation: it's either dead or alive until the box is opened.
Wigner and his friend don't see eye to eye
If that statement sounds ridiculous, well, Einstein and company thought so, too. Per the Conversation, Einstein said, "Do you really believe the moon exists only when you look at it?" In other words, of course the cat is dead or alive unto itself before I open the box. The observed, like a tree falling in a forest, doesn't require an observer to be or do.
But this isn't actually true, at least sub-atomically. Particles can exhibit states of "entanglement" — both "up" and "down" at the same time, meaning, a) reality is non-deterministic, even random, or, b) reality is non-local, meaning it changes depending on the location of its measurement device, as physicist John Bell said in 1964 (per the International Weekly Journal of Science). Or in linguistics' terms: Is the cat dead or alive until seen? Yes. So bravo to the Daoists and neuroscientists: It turns out reality really doesn't exist unto itself any more than I exist without you. We're all one consciousness, as Bill Hicks said in his "positive LSD" joke (watchable on YouTube), experiencing itself subjectively.
All of this was verified as recently as 2018, per MIT Technology Review, when researchers confirmed the "Wigner's friend" thought experiment put forth in 1961 by Nobel Prize-winning physicist Eugene Wigner. Researchers observed six "entangled" (unmeasured) photons from two different locations, and bam: two seemingly contradictory sets of results. Reality was different. How this impacts chairs in rooms, though, remains yet untangled.