On Uncommon Descent, Barry Arrington asks:
Let’s clear up this law of noncontradiction issue between StephenB and eigenstate once and for all. StephenB asks eigenstate: “Can the planet Jupiter exist and not exist at the same time in the same sense? That’s a “yes or no” question eigenstate. How do you answer it?
For some reason, Eigenstate’s response has gone astray, so here it is, as cross-posted elsewhere:
Theoretically, yes. In practice, the probabilities are so vanishingly small it’s indistinguishable from no.
Scale matters; superposition is fragile with respect to other elements in the system that force a classical resolution. Recent experiments have provided experimental verification that macroscale objects can be put in superposition (see here):
But although the rules of quantum mechanics seem to apply at small scales, nobody has seen evidence of them on a large scale, where outside influences can more easily destroy fragile quantum states. “No one has shown to date that if you take a big object, with trillions of atoms in it, that quantum mechanics applies to its motion,” Cleland says.
The “paddle” object in this experiment was just 30 micrometers long. But that’s freaking HUGE compared to the Planck length. Jupiter is just so many orders of magnitude bigger than that, that the prospects for superposition in that case become ONLY theoretical. Too many resolving influences make it statistically impossible.
The linked article describing the experimental evidence for QM weirdness “scaling up” includes this comment from a physicist at the U of Oregon:
“It’s wonderful,” says Hailin Wang, a physicist at the University of Oregon in Eugene who has been working on a rival technique for putting an oscillator into the ground state. The work shows that the laws of quantum mechanics hold up as expected on a large scale. “It’s good for physics for sure,” Wang says.
So if trillions of atoms can be put into a quantum state, why don’t we see double-decker buses simultaneously stopping and going? Cleland says he believes size does matter: the larger an object, the easier it is for outside forces to disrupt its quantum state.
Those wacky physicists, I tell ya.
On an LNC-related note, this from the same article:
Next, the researchers put the quantum circuit into a superposition of ‘push’ and ‘don’t push’, and connected it to the paddle. Through a series of careful measurements, they were able to show that the paddle was both vibrating and not vibrating simultaneously.
Sound familiar, StephenB (and Barry, if you’ve been reading our exchange)? I will note here that champignon’s comment on this being best viewed as a Law of the Excluded Middle issue is a point well taken. But that notwithstanding, you have QM weirdness in the real world ostensibly misbehaving against our propositional logic. “Vibrating” and “Not Vibrating” in the same sense, for the same object at the same time.
Here’s another example from a similar experiment (link), where Dr. Anthony Leggett of U of Illinois, Champaign, Urbana weighs in on a solar system body — not Jupiter but the moon (the moon was the example Einstein initiated these questions with: “does the moon exist if no one is looking at it?” :
For Dr. Leggett, quantum mechanics at the macroscopic level is still uncertain — and troubling. “It may bother me even more now,” Dr. Leggett said. “I’m interested in the possibility that quantum mechanics, at some stage, may be wrong.”
A few physicists have devised so-called macrorealistic theories to resolve the ambiguities of quantum mechanics. “What you get in quantum mechanics is not what you see,” said Dr. Philip Pearle, a professor of physics at Hamilton College in Clinton, N.Y. “Schrödinger felt this acutely. He himself felt something with quantum mechanics was wrong.”
Dr. Pearle and colleagues in Italy propose to add a term to Schrödinger’s equation that, in effect, constantly jiggles the fabric of the universe. Atomic-scale objects only jiggle a little and thus remain a blur, which preserves the predictions of quantum mechanics. Larger objects, like people or the Moon, jiggle more and quickly fall into a definite here and there, which corresponds to everyday experience.
Barry, if you’ve read my earlier responses to StephenB on this, you will recognize the same ideas quoted here in my answers. Jupiter has a virtually zero statistical basis for avoiding decoherence, hence it will ALWAYS be there in the full, classical (non-superposition) sense.
Lastly, this, regarding the LNC-problematic nature of this second expirement:
The experiment combines two possibilities, known as a quantum superposition, for the direction of the flow of electric current: clockwise around the loop or counterclockwise.
The researchers measured an energy difference between the two states of the loop, a sign the current was a quantum superposition and not simply flipping directions.
Just as the cat is neither alive nor dead but a ghostly mix of the two possibilities, the current flows neither clockwise nor counterclockwise, but is a mix of the two possibilities.
Note that per superposition, this is not simply a matter of a “bi-directional current”. This is two otherwise exclusive one-way directions happening at the same time, exclusive states superimposed:
A measurement always gives one of the two possible answers, clockwise or counterclockwise, never a zero cancellation.
Glad to have the opportunity to settle this once and for all! Statistically, it will never happen for Jupiter, but it remains a theoretical possibility. It’s the same as wondering if I could fairly shuffle and deal a 52 card deck and deal the cards out, producing the same exact card order as the first shuffle a billion times in row. In theory, it cannot be eliminated as a possibility. As a practical matter, the odds are insdistinguishable from zero.