By Eric Vandenbroeck and co-workers

The disputes about Quantum Mechanics

On November 18-19, 2021 the major ICQPQM: International Conference on Quantum Probability and Quantum Mechanics will take place in Singapore.

As the title suggests it bring together leading academic scientists, researchers, and research scholars to exchange and share their experiences and research results on all aspects of Quantum Probability and Quantum Mechanics. But as Nassim Nicholas Taleb recently wrote "survivorship bias implies that the highest performing realization will be the most visible." I fact as we shall see this also very much applies to Quantum Mechanics.

Erwin Schrödinger (1887–1961) was born in Vienna, the only child of a botanist and a mother who was half English.1 As a consequence, he could speak perfect English, as well as German, French, and Spanish. He was an excellent student and was also able to translate Ancient Greek and Medieval German. After college, he worked as a teacher and, in 1914, was called up as a commissioned officer in the Austrian Army and served at an artillery post in Italy.                      

Once the war ended, he became a professor in Zurich. In 1922, he developed severe respiratory problems, which were diagnosed as tuberculosis. He retreated for nine months to a Swiss mountain village near Davos to take the “cure.” At that time, high altitude and lack of oxygen were thought to stimulate the body to produce more red blood cells to fight infection. (In fact, the bacteria that causes tuberculosis depends upon oxygen to spread, so high altitude does combat the disease, although for different reasons than doctors at the time believed.) Schrödinger would return to the mountains during most summers throughout the 1920s. It was on one of these retreats, over New Year’s Eve of 1926, when he conceived his greatest contribution to science.

The Schrödinger equation has been called “one of the most important achievements of the twentieth century and created a revolution in most areas of quantum mechanics.”2 The Schrödinger equation allows us to model the behavior of small particles, which was a challenge for classical mechanics. It is widely used today as originally formulated. He received a Nobel Prize for his work in 1933, and the formula is inscribed on his tombstone in Vienna. 

 

Bust of Schrödinger, in the courtyard arcade of the main building, University of Vienna, Austria:

The success of the Schrödinger equation made it possible for Schrödinger to move to Berlin in 1927 and succeed Max Planck at Friedrich Wilhelm University. However, Schrödinger disliked the Nazis and left Germany in 1933 for Oxford. When he resigned, Hitler wrote him a letter thanking him for his services to the nation. But the farewell missive also suggested that Schrödinger’s departure was not unwelcome. 

He arrived in Oxford with his wife and his mistress, who was pregnant with their child. After the child was born, the two women looked after the baby together. The Oxford dons were not pleased. They had been unaware of Schrödinger’s living arrangements prior to offering him an academic post. They made their displeasure known. (Throughout his life, Schrödinger traveled and lived with two or more women at the same time. Schrödinger loved the company of women, and they seemed to feel the same.) Around the time the Oxford dons began voicing their disapproval of Schrödinger, Princeton University approached him, and he accepted an interview. However, when the Princeton University president learned that Schrödinger’s wife, mistress, and illegitimate child would accompany him to campus, it was decided other candidates were more qualified. 

So, in 1936 Schrödinger decided to return to Austria and accepted a position at the University of Graz. Years later, he described his action as “unprecedented stupidity.”3 Graz was a hotbed of Nazism and Austrians who favored unification with Germany. Furthermore, Schrödinger’s departure from Germany in 1933, after winning the Nobel Prize, had not been forgotten by Hitler. Schrödinger was advised that if he wished to retain his position at the university, he needed to write a penitent letter, which he did. In the letter, he called upon his fellow Austrians to embrace Hitler and his goals and stated that he had “misjudged up to the last the true will and true destiny of my country. I make this confession willingly and joyfully.”4 The Nazis published the letter widely in German and Austrian newspapers. 

Soon, however, Schrödinger became uneasy about events in Germany. He was not a Nazi party member and, as a consequence, was dismissed from his post at the Prussian Academy in 1938. But his widely publicized letter foreclosed a position at an English or American university. When Schrödinger was approached about a professorship in Ireland, he arranged to travel to Dublin for an interview. But the German foreign minister, Joachim von Ribbentrop, informed Schrödinger he would not be allowed to travel to the United Kingdom. 

Now doubly concerned, Schrödinger and his wife, leaving his mistress and child behind, arranged to travel to Rome under the pretense of visiting Fermi. The couple then traveled to Geneva, crossed over the border to France, and went on to Dublin. Once settled, he sent for his mistress and child, and the four of them lived in a house in Dublin for the next seventeen years. Schrödinger fathered at least two more daughters by two different mothers in Ireland and supported his extended family by lecturing at University College. He returned to Vienna in 1956 and died of tuberculosis in 1961, aged seventy-three.

 

“But how can it be like that?”

Schrödinger is considered one of the fathers of quantum mechanics, which describes how matter and energy behave at a microscopic level. It is the counterpoint to classical mechanics, which models the macroscopic world. Not surprisingly, classical mechanics is intuitive to most, as we interact with the macroscopic world all day long. But most of us have little or no experience with the microscopic world, and hence quantum mechanics can seem quite strange.

The physicist Richard Feynman has stated: 

I think I can safely say that nobody understands quantum mechanics . . . Do not keep saying to yourself, if you can possibly avoid it, “But how can it be like that?” because you will get down the drain, into a blind alley from which nobody has yet escaped.5

Nevertheless, the predictions of quantum mechanics have proven remarkably accurate in the microscopic world. We depend upon quantum mechanics to design everything from microchips to MRIs.

Classical and quantum mechanics are fundamentally different ways in which to view the world around us. How we think about electrons is an example. 

In the world of classical mechanics, an electron circles the nucleus of the atom-like Earth orbits the sun. In the world of quantum mechanics, an electron is an energy wave. This energy wave is described by a formula (Schrödinger’s equation) that predicts the probability of an electron’s location but offers no certainty on where an electron will be at any particular time. Although not all places are possible, some places are more likely than others.

This is counterintuitive. Suppose an electron is like a ball on the top of a hill. A ball at the top of the hill exists at the top of the hill. We don’t see a series of balls spread out on all sides of the hill in various probabilities of existence. 

Quantum mechanics also says that electrons exist around the nucleus of an atom as energy waves at only a limited number of energy levels. Between any two of these energy levels, electrons cannot exist. Scientists know this because if electrons moved in an unbroken arc when transitioning between levels, then the energy in the form of light would radiate over a continuous spectrum. It does not. Electrons “jump down” into a lower energy level by releasing energy at only specific wavelengths. 

This is also counterintuitive. In the analogy of a ball at the top of a hill, the ball does not progress down a hill in a series of sudden surges. Rather, it smoothly tumbles end over end in a continuous motion as it dissipates energy. 

But these are not the strongest parts of quantum mechanics. 

 

The Copenhagen Interpretation.

Many interpretations, including the Copenhagen interpretation presented by Niels Bohr and Werner Heisenberg and in particular von Neumann-Wigner's interpretation, state that the consciousness of the person conducting the test affects its result.

Thus after discovering quantum mechanics, Schrödinger and others peered down into their high-powered microscopes at electrons, and what they saw was a bunch of particles. Several of the scientists, such as Schrödinger, had been awarded Nobel Prizes for inventing formulas that proved electrons were waves, so this required some explaining. The explanation some of them came up with was that electrons are waves, except when we look at them. Some decided the best way to explain why the Nobels should not be returned was to say the effect of observing an energy wave “collapses” it into a particle. Until observed, an electron is an energy wave, lacking physical form. The theory that we collapse energy waves by observing them is known as the Copenhagen interpretation (CI) of quantum mechanics, which was put forth by Danish physicist Niels Bohr and others. 

The CI view of the world is another way in which quantum mechanics is completely different from classical mechanics, in which the observer is independent of what is observed. In classical mechanics, a tree that falls in the woods still makes a sound, even if no one hears it. Not so according to the CI. Without the presence of an observer, the energy wave of the tree exists in a “superposition” of multiple possible states. If you believe in the CI, then the world around us is just energy waves waiting to be watched so they can become physical objects. As one physicist wrote: “We are faced with the prospect of waves that somehow magically sense that they are being observed and so decide to become particles instead.”6 

Schrödinger and his friend Einstein really did not like the CI. In particular, Einstein preferred to think visually, often working through a particularly perplexing puzzle in physics with a thought experiment involving everyday objects, and his thought experiments concerning the CI yielded contradictory outcomes.

In one instance, Einstein shared with Schrödinger a thought experiment involving two closed boxes and a single ball, “which can be found in one or the other of the two boxes when an observation is made.”7 Einstein was probing what he saw as a problem with the CI, which claimed the ball did not exist until an observer peered inside one of the boxes. Einstein argued that surely the ball was in one of the boxes before either of the boxes was opened. Along the same lines of thought, Einstein once asked a proponent of the CI whether he believed the moon existed only when he looked at it.8

Also, Einstein and Schrödinger did not like the idea of “non-locality,” or the notion that two objects at a distance can interact with each other instantaneously. Under the CI, a wave of energy collapses into a physical object upon observation. In the case of Einstein’s thought experiment, if the observer opens one of the boxes, looks inside, and sees a ball, then that causes the other box to become empty. But Einstein’s theory of special relativity precluded anything from moving faster than the speed of light. If the boxes were a hundred light-years apart, then Einstein thought the act of observing the box with the ball could not at the same moment empty the other box. Einstein called this “spooky action at a distance.”9

 

Schrödinger’s Cat experiment and the conundrum that rules modern physics

 

In 1935, Schrödinger cast Einstein’s thought experiment into a thought experiment of his own, which has become known as Schrödinger’s cat.10 In this variation on Einstein’s original thought experiment, a cat is penned into a steel chamber along with a Geiger counter that during the course of an hour either emits a radioactive substance or emits no substance at all. The odds of the Geiger counter emitting a radioactive substance are on average 50/50, and the emissions occur randomly. When the radioactive substance is emitted, a relay releases a hammer that shatters a flask of hydrocyanic acid within the steel chamber. The cat inhales the toxic fumes and then dies. (Schrödinger’s daughter years later said he did not like cats.) 

Schrödinger is illustrating that the CI claims the cat is neither alive nor dead until an observer opens the lid of the steel chamber to peer inside. But Schrödinger believed this was a “ridiculous case.”11 He believed that the cat was either dead or alive, killed or not killed by the hydrocyanic acid before the observer collapsed the cat wave function by gazing into the steel box. 

Einstein liked Schrödinger’s version of his thought experiment. He wrote to Schrödinger: 

Your cat shows we are in complete agreement concerning our assessment of the character of the current theory. A function that contains the living, as well as the dead cat just, cannot be taken as a description of the real state of affairs.12

Schrödinger himself never got comfortable with the CI. Near the end of his life, he wrote: “It is patently absurd to let the wave function be controlled in two entirely different ways, at times by the wave function, but occasionally by direct interference of the observer, not controlled by the wave equation.”13

Einstein expressed similar sentiments in his later years, writing that the CI “reminds me a little of a system of delusions of an exceptionally intelligent paranoiac.”14

Over the years, others have raised more questions about the CI. One set of questions relates to what is called the measurement problem. In other words, what constitutes an observer? Does it have to be an intelligent being, such as a human? If an insect peered into the steel chamber, would the effect of an observation by the bug collapse the cat energy wave? If the insect was napping when the lid was opened, then would the cat energy wave still collapse? 

If a napping insect is sufficient, then what about a sleeping germ? But a germ (as far as I can tell) is not really conscious even when fully awake. Does that mean any physical object, such as the Geiger counter next to the cat, will collapse the cat energy wave, and, if so, why is an observer required at all?

Many physicists today continue to adhere to the CI. While readily acknowledging the apparent contradictions pointed out by Einstein and Schrödinger, they argue that what ultimately matters is that the equations of quantum mechanics accurately model the outcomes of experiments. 

Hence, the CI has sometimes been labeled the “shut up and calculate” school of physics. 

Most of those who adhere to the CI don’t love this interpretation of quantum mechanics as much as they hate the other one. And this is where survivor bias comes in. 

 

The Many-Worlds Interpretation

The idea that the universe splits into multiple realities with every measurement has become an increasingly popular proposed solution to the mysteries of quantum mechanics. But this “many-worlds interpretation” is incoherent, Philip Ball argues in this adapted excerpt from his new book Beyond Weird.

The many-worlds interpretation, or MWI, was formally proposed in 1957 by physicist Hugh Everett. The MWI claims that individual wave functions do not collapse but simply branch into two or more parallel worlds. This interpretation resolves the paradoxes about the role of observers by removing observers from a central role. 

In the example of Schrödinger’s cat, there is a branch of the universe in which the cat lives and another one in which the cat dies. Upon opening the lid to the steel chamber and seeing a dead cat, the observer has branched off into the parallel world in which the cat dies. Under the MWI, the cat is either really alive or really dead before the observer peers into the box. The first quantum event is the emission, or lack thereof, of a radioactive substance by the Geiger counter. The second quantum event is the cat either dies, or doesn’t, and the third quantum event is when the observer opens the lid. At each quantum event, the “old” world branches into two “new” parallel worlds. 

Under the MWI, once the branches split, there is no more interaction between them. In the case of Schrödinger’s cat, if the observer branches off into the dead cat world, there is sadly no way to go back to the alive cat world. Nor does the observer realize the alive cat world even exists, unless they are well versed in the MWI of quantum mechanics. The current version of themselves exists only in the branch of the dead cat world. There is another version of themselves who lives on in the branch of the alive cat world, but that is scant consolation. (In a related example of survivor bias, the alive cat may be inclined to believe in the MWI, and the dead cat will have no opinion.) 

The MWI answers many of the objections to the CI. In the MWI version of quantum mechanics, the cat is really alive, or really dead, just in two different but equally real parallel worlds. The MWI also resolves the problem of the world not existing without an observer. Every branch of the world caused by a quantum event is independent of whether an observer is there or not. The cat lives in one parallel world and dies in the other based on the action of the Geiger counter, independent of the observer. 

However, the MWI raises other issues. One implication of the MWI is the counterintuitive notion that there is an almost infinite number of parallel worlds, and different versions of you and I exist in many of them. In some number of parallel worlds, a version of you is reading this book in a slightly different way. (Or you have given up reading this chapter several pages ago in another parallel world for perfectly understandable reasons.) In any case, the proponents of the MWI argue that at least there is nothing contradictory about this version of the world, unlike the CI, in which cats are neither dead nor alive until we look at them. 

Admittedly, we can’t prove the other branches of the universe exist since we have already split off from them. And this is what the opponents of the MWI say is a problem with this version of quantum mechanics: A theory that cannot be falsified is not a scientific theory. Opponents argue that if the MWI cannot be proven or disproven, it is not worth talking about at all. Even some who believe in the MWI will admit there is no way to prove this particular implication of the MWI. By definition, parallel worlds that could be reached from our world are not parallel. 

But not all the implications of a theory have to be subject to falsification for the theory to be believed. Imagine a theory that predicted 100 specific outcomes, and 99 of those outcomes could be proven or disproven through traditional scientific methods. Tests are conducted on the 99 outcomes, and the results of every single one of those 99 tests prove the theory. Despite the fact that one outcome could not be tested, most would readily accept the theory as a valid scientific theory. 

Both the CI and MWI make the same predictions about the outcomes of experiments in the lab. The proponents of the MWI argue that just because one prediction of the MWI theory, parallel worlds, can not be tested does not mean we should cast the entire theory aside as unscientific. Except for the existence of parallel worlds, all the other implications of the MWI are the same as the CI and therefore equally valid. Furthermore, the MWI is free of the contradictions that riddle the CI. 

Regardless, it is safe to say that physicists, in both the CI and MWI camps, wish they had intuitive answers to the questions posed by Schrödinger’s thought experiment about a cat. 

 

“When I hear of Schrödinger’s cat, I reach for my gun.”

Stephen Hawking, the leading physicist of the latter half of the twentieth century, reluctantly admitted while he was still alive that he was in the MWI camp. But Hawking also said: “When I hear of Schrödinger’s cat, I reach for my gun.”15 

The MWI implies that the world in which you are reading this book is the product of a series of quantum events leading up to this moment. At each of those quantum events in the past, the “old” world branched into “new” worlds and so on to arrive at the present day. Today’s world is one of the ancestors of all those other worlds, and this version of ourselves is part of that lineage. You may not realize it, but you are a branching survivor. 

However, a past version of you probably did not survive every quantum event. Perhaps an unfortunate accident befell you. Suppose in the past you were strolling down a city street and unknowingly walked directly beneath a piano that was in the process of being hoisted by a crane twenty stories above. In one world, the piano slipped its straps, and in another world, it didn’t. Due to survivor bias, you don’t realize how risky hoisting pianos can be. 

Similarly, nothing in quantum mechanics nor the MWI mandates that the next universe you branch into will support human life. It could be that branching is quite a risky business, and after most quantum events we instantly perish, launched into a universe adverse to biological organisms. In fact, there are two camps of believers on the type of parallel universes that are possible: those who adhere to the strong anthropic principle (SAP) and those who support the weak anthropic principle (WAP).16

The adherents to the SAP claim there are a set of fundamental physical laws that constrain all that exists to “Goldilocks” universes, defined as worlds with characteristics agreeable to living organisms in general and for humans in particular. Of course, many Goldilocks universes may be lifeless, or at least devoid of intelligent beings. (Recall from Fermi’s paradox we don’t know the odds intelligence life will eventually evolve on Earth-like planets.) Proponents of the SAP simply claim the universe of possible universes includes only those with characteristics that are the same as ours, worlds that can potentially support intelligent life. 

By contrast, the believers in the WAP say that there may be a set of fundamental physical laws that determine what universes are possible, but those laws allow for worlds quite different from our own, and Goldilocks universes are quite rare. They point to the fact that there are about twenty constants in the basic formulas of particle physics and another ten in cosmology.17 If any of these thirty or more constants differed by even 1 percent from their known values, our universe would be unfit for life.18 For example, a variation in the strength of the constant for gravity by one part in ten to the fortieth power would prevent the formation of stars.19 Additionally, universes could exist with fewer than three dimensions. In a universe with one or two dimensions, complex structures, such as human brains, could not form, as the number of connections between the individual parts would be limited.20 In a one- or two-dimensional universe, the potential for intelligent life as we know it is foreclosed. In short, the argument is that there are more ways things can go wrong than right: There are many possible states for a scrambled egg but only one that can yield a chicken. 

Under the MWI, the universe is constantly evolving, continually splitting into new universes. But Goldilocks universes have a specific set of characteristics, such as three or more dimensions and dozens of physical laws that each obey a formula with constants that are “just right” for life. Those who believe in the WAP contend that Goldilocks universes are the exception, the stars literally all have to align. 

Einstein stated the differences between the WAP and the SAP in terms of a Creator: “What I am really interested in is whether God could have made the world in a different way; that is, whether the necessity of logical simplicity leaves any freedom at all.”21 

Some religious philosophers picked up on Einstein’s comment to claim he thought God created Goldilocks universes for us to live in. They contended that Einstein believed a divine hand-fashioned our world because of the infinitesimally small odds that Goldilocks universes randomly emerge. Given an infinite number of sterile non-Goldilocks worlds and only a few that are not, Goldilocks universes must have been purposefully selected among all possible universes by some Being existing before and outside these universes. Basically, the argument is that it is more likely God exists than humans got lucky.

But this argument fails to account for survivor bias. The big bang and at least one line of branches had to be all Goldilocks universes, or we wouldn’t be here to suffer headaches from thinking about quantum mechanics. 

As we have seen, only a small change is required in any of the particular physical laws and features of our universe to destroy all life. And if non-Goldilocks universes occur regularly during branching, then this is not encouraging for this particular version of ourselves, survival-wise. By contrast, adherents of the SAP have a much more optimistic take on our future, as they are convinced it’s Goldilocks universes as far as the eye can see.

 

Trapping Schrödinger’s Cat

Fortunately, even believers in the WAP, have cause for hope. One implication of the MWI is that all possible outcomes are realized in at least one parallel world. So, at every quantum event, there should be at least one jump to a Goldilocks universe, and therefore at least one version of ourselves will live on.

An analogy is to a game of Russian roulette: A gun with six chambers is loaded with one bullet, the barrel is spun, and the players take turns pointing the gun at their head and pulling the trigger. After each pull, the world branches into two new worlds: The gun fired or it didn’t. After dozens of rounds, all the players will likely be dead. However, in at least one parallel universe all the players survive, as it is always possible for the gun not to fire. Under the MWI, a game of Russian roulette will continue in at least one parallel world until the players die of something else. 

If the MWI is true, then different versions of ourselves live on in some number of parallel worlds, and in others, we don’t. In theory, there is always a version of ourselves who finds they have fortuitously landed in a Goldilocks universe. The ratio of the worlds in which we survive versus those in which we perish we cannot know for certain. 

 

But history can be a guide.

Stanislav Petrov was assigned to bunker at Serpukhov-15 at most two nights a month. That suggests in most parallel worlds a global nuclear war began on September 7, 1983. Vasily Arkhipov was rarely assigned to Soviet submarine B-59. That would indicate in most parallel worlds our species didn’t survive the Cuban Missile Crisis. Perhaps in most other universes, we triggered a runaway greenhouse effect years ago. 

Pictured below Vasili Arkhipov was awarded the new ‘Future of Life’ prize:

According to the MWI, there is at least one world in which all the players in a game of Russian roulette survive. That could very well be the equivalent of the world in which we live today. 

If the MWI of quantum mechanics is true, then the branching that occurs distorts our view of the past. In the analogy of the Greek ships observed by Diagoras, some sailors branched into the “returned safely to port” parallel world, and others did not. Those who branched into the returned-to-port parallel world are misled by survivor bias into concluding that seafaring is not a risky business. Today’s world is simply the one in which we survived an almost infinite number of quantum events and subsequent branching. In other parallel worlds, we may have been targeted (again) by a space rock, defeated by the Neanderthals, or eaten by aliens. In other parallel worlds, we did not survive the acquisition of advanced technologies, such as nuclear weapons and the burning of fossil fuels. We sometimes argue about how our world came to be or why the world is the way it is, based on religious or philosophical beliefs. If the MWI is true, then the answer is our world is just the one in which this version of ourselves survived. In that sense, the MWI of quantum mechanics is the ultimate example of survivor bias.

 

1. For a good biography see John Gribbin, Erwin Schrödinger, and the Quantum Equation. John Wiley & Sons. Hoboken, NJ., 2013.

2.​ New World Encyclopedia contributors “Erwin Schrödinger” (2021), s.v. Middle years. 

3. ​Gribbin (2013), p. 187. 

4. ​Gribbin (2013), p. 193.

5. ​Peter Byrne, The Many Worlds of Hugh Everett III. 2010. Oxford University Press. Oxford, UK, 2010. p. 144. 

6. ​Ball, Robert. (2003). The Fundamentals of Aircraft Combat Survivability Analysis and Design. American Institute of Aeronautics and Astronautics. Reston, VA, p. 72. 

7. ​Gribbin (2013), p. 180. 

8. ​Ball (2018), p. 99. 

9. ​Becker, Adam,  What Is Real? Hachette Books. New York. (2018), p. 56. 

10. ​Becker (2018), p. 181 for a translation of the actual words Schrödinger used. 

11.​ Gribbin (2013), p. 181. 

12.​ Gribbin, John, Erwin Schrödinger and the Quantum Equation. John Wiley & Sons. Hoboken, NJ. (2013), p. 182. 

13.​ Gribbin (2013), p. 221. 

14.​ Becker (2018), p. 14. 

15. ​Ferris, Timothy. (1997). The Whole Shebang: A State of the Universe Report. Simon & Schuster, New York, p. 276. 

16. ​The arguments over Goldilocks universes are usually related to a discussion about the multiverse and the big bang. However, there is no reason that the same speculations could not apply to the MWI. 

17. ​Davies, Gavyn, “How a Statistical Formula Won the War.” The Guardian. July 19, 2006. (2006), p. 146. 

18. ​Davies (2006), p. 146. 

19. ​Harris, Errol, Cosmos and Anthropos. Humanities Press International. London. (1991), p. 51.

20. ​Barrow, John et al., The Anthropic Cosmological Principle. Oxford University Press. Oxford, UK.(2009), p. 266. 

21. ​Thomas, Andrew, Hidden in Plain Sight 7. Self-published. Tillman, Barrett. (2014). Forgotten Fifteenth. Regnery History. Washington, DC.(2017), p. 83.

 

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