Quantum Enigma part 3 (review)- What constitutes an observation, and Schrödinger’s controversial cat

Now that we have dove deep into the abyss of the quantum enigma through discussing the details of the theory-neutral experiments performed in which the enigma came about, we will now discuss what those experiments encountered- the observer.

Niels Bohr recognized that physics had encountered the observer and came up with the “Copenhagen interpretation” at his institute in Copenhagen. There is no “official” interpretation, but each version asserts that an observation produces the property observed.

What is meant by observation? Think of an observation taking place whenever a macroscopic object interacts with a microscopic object. Example- when a piece of photographic film is hit by a photon and records where the photon landed, the film “observes” the photon. Considering the fact that we never deal directly with microscopic objects such as atoms, it is only necessary to consider the response they have on our macroscopic objects to be real, since this is the only behavior we report.

The Copenhagen interpretation rests on three ideas- The Three Pillars of Copenhagen.

The probability interpretation of the wavefunction- the probability interpretation of waviness- probability of an object being found in certain region, is central to the Copenhagen interpretation. Quantum mechanics displays nature’s intrinsic randomness (on the atomic level). Probability in quantum mechanics implies more than randomness. Quantum probability is not where the atom is. It is the objective probability of where you, or anybody who looks, will find it. The atom wasn’t someplace until someone observed it to be there. “Observations not only disturb what is to be measured, they produce it.” – Pascual Jordan. So, only the observed properties of microscopic objects exist. “No microscopic property is a property until it is an observed property.” – John Wheeler. In other words, the microscopic objects are not themselves real. They are just possibilities, they are abstract, not physical. So how do we account for big things that are made up of the small things? Basically, the small things that are not dealt with don’t actually exist. So they are just used to describe the bigger things. The idea here is not to figure out how nature is, but what we can say about nature. How we can explain the actual world.

The Heisenberg Uncertainty Principle: Heisenberg was Bohr’s colleague who is known for his contributions in explaining the quantum enigma in his belief that everything is quantum mechanical and therefore subject to the enigma. Basically, with this principle- “The more accurately you measure an object’s position, the more uncertain you will be about it’s speed. And the more accurately you measure an objects speed, the more uncertain you will be about it’s position.” This principle can be derived directly from the Schrödinger equation. “In fact, the observation of any property makes a ‘complementary’ quantity uncertain.” Example- position and speed are complimentary quantities, same for energy and time, etc. So basically, observation of any property disturbs what will be observed, preventing refutation of quantum theory’s assertion that observation creates the property observed.

Complementarity: This is the third pillar of the Copenhagen interpretation and it is what disturbed Einstein the most, not randomness- it is the hard one to accept). Think back to our box-pairs experiment. When opening one box at a time, you find an atom to be wholly in the first or second box opened. Supposed you do this with 1,000 box-pairs. You throw out the half in which you saw, and therefore, disturbed the atom. You are left with 500 box-pairs whose atoms are not physically disturbed. But for these boxes you know which box each atom is in; the box you did not look in (the 500 boxes you still have). Suppose you do an interference experiment with these boxes and the supposedly undisturbed atoms do not produce an interference pattern. Although these atoms were not physically disturbed, you determined which box the atoms were in. “Apparently, your acquisition of that knowledge was sufficient enough to concentrate each atom totally within a single box.” Bohr asserts that the two aspects of a microscopic object, it’s particle aspect, and it’s wave aspect are “complimentary.”

“Altough physicists talk of atoms and other microscopic entities as if they were actual physical things, microscopic things are only concepts we use to describe the behavior of our measuring instruments.”

As I was talking about this book with a coworker, he stated the exact words that this book points out all of us will likely think- “But I could have chosen to do the opposite, therefore I have free will” and we usually leave it at that. We could have done the opposite and produced the opposite outcome. However, the Copenhagen interpretation would suggest not to think about experiments that you might have done but did not in fact do. It is our perception that we could have chosen to do the opposite that give rise to the quantum enigma. “Not done experiments have no results!” Although we have the knowledge that one experiment produces an outcome that is different to the other experiment, we cannot actually display a logical contradiction using the same boxes, and the same atoms. This assumption- that we could have done other than what we actually did is called “counterfactual definiteness.” One example- believing that if you did not eat lunch, you’d be hungry is counterfactual definiteness. Denying counterfactual definiteness, the copenhagen interpretation would seem to deny free will. So is free will an illusion?

Psychology analogy on behavior– “The physical behavior itself presents no paradox. The person’s physical movements make sense in that they accord with Newton’s law of motion. A person’s motives, however, are theories that should explain the person’s behavior. But the motives themselves need not, and often do not, make sense. We pragmatically accept this stance in dealing with people. The Copenhagen interpretation asks us to accept this stance in dealing with microscopic physical phenomena- that the microscopic objects should explain that behavior of our macroscopic objects, but the microscopic objects themselves need not ‘make sense’.”

Although quantum mechanics doesn’t completely make sense (to anyone- including scientists), not a single prediction has ever been proven wrong. It works perfectly. Observation-creation reality suggests that the small things are only real when they are being observed, this may seem absurd. But, the small things are only models, they do not need to make sense, they just need to work. Large things are real enough, so everything is fine. For all practical purposes, big things are always being looked at, so you never see any craziness with them. “Science provides no meanings. Science just tells us what will happen. It just predicts what will be observed… Science can reveal no real world beyond what is observed. Anything else is merely philosophy.”

Schrödinger’s Controversial Cat– After realizing how absurd quantum theory seemed, Schrödinger took back his claim and came up with a story to prove why quantum theory couldn’t work. This story involved a cat being placed in a box with a radioactive atom that had a 50% probability of decaying and firing a Geiger counter to pop the cork and open a bottle of cyanide, killing the cat, so when you opened the box, you would find that cat dead or alive. However, it is emphasized by Rosenblum and Kuttner that whether the cat is seen as dead or alive is completely random, and cannot be influenced by the observer (or anything else). This example explicitly displays that quantum theory not only has observation creating the reality observed, but the appropriate history to go with it. Example- suppose you wait 8 hours to look into the box and see whether the cat is dead or alive. If you find the cat alive, you assume the cat is hungry since it has gone 8 hours without eating. If you find the cat dead, an examination by a veterinary forensic pathologist would determine that the cat died eight hours ago. – “Your observation not only creates a current reality, it also creates the history appropriate to that reality.”

“Somewhere something incredible is waiting to happen….” John Wheeler

This post is part of a series, for links to other topics click here!

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