Wednesday, February 24, 2016

Heisenberg and Me

            In 1959 C.P. Snow wrote about the difficulty of communication between scientists and the rest of us.

A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is the scientific equivalent of: Have you read a work of Shakespeare’s?

I now believe that if I had asked an even simpler question — such as, What do you mean by mass, or acceleration, which is the scientific equivalent of saying, Can you read? — not more than one in ten of the highly educated would have felt that I was speaking the same language. So the great edifice of modern physics goes up, and the majority of the cleverest people in the western world have about as much insight into it as their neolithic ancestors would have had.

            My friend Bill challenged me to write a blog post about quantum physics. I prepared a draft that I sent to my Amherst classmate, Phil, a recently retired professor of physics. With his permission, I am posting my draft with his comments in red, then blue.

Heisenberg and Me

            When I was a high school kid in the late 50s I had a pretty secure Newtonian sense of how the world worked. It was a mechanistic system based on f=ma. One implication that I toyed with was that if we knew all the variables, then we could predict the future. The fact that there were so many variables as to make accurate prediction impossible was indeed a problem, but not to the overall sense of determinism. We were in a giant pinball machine with no “free will” flippers on the side to alter our fates. Our only saving grace was that our ignorance gave us the illusion of freedom. Genetics was no help – just more determinism.
            But then toward the end of my freshman year at Amherst, my universe exploded. A physics professor introduced me to Heisenberg’s Uncertainty Principle, which states, in an inadequate [actually pretty adequate] summary, that it’s impossible to know both the location and the path of an electron as it moves through space. I read a simple-minded analogy about the impossibility of measuring the temperature of a bucket of water because the temperature of the thermometer changes the temperature of the water you are measuring. That’s like the way the anthropologist who observes a village changes the behavior of the villagers just by being there.
            But the more I looked into the Uncertainty Principle and quantum physics, unburdened by an education in science, the more I realized that the issue is more difficult than that – and a lot more fun. [Yes.] The 2004 film What the Bleep Do We Know?!, which I have now seen half a dozen times, deepened the adventure, especially when watching it with family and friends. An electron, one physicist said, must be regarded as being “at once everywhere and nowhere.” Tiny particles blink in and out of existence, jumping from one place to another in a “quantum leap,” without actually moving through the space between them. Paired particles, at a distance, instantly “know” what the other is doing. Change the spin of one, and the other one instantly mirrors the change. Yes, instantly, with no communication even at the speed of light. [Apparently a lot of physicists do believe this.  It is Einstein’s “spooky action at a distance.”  Einstein felt it proved the inadequacy of quantum theory.  My own attitude is much more pedestrian, and allows me to accept quantum mechanics but not believe that “Paired particles, at a distance, instantly “know” what the other is doing.”  See my comments at the end.] The fun is in imagining this kind of subatomic behavior going on in my everyday life. I’ve tried spinning when Kim is in the next room, but instead of spinning, all she does is shoot me a tolerant smile.
            “Reality,” at this subatomic level, is only a construct that our minds seem to require. Perception, therefore, is a creative act, and the so-called “objective reality” is just a convenient illusion. By “convenient” I mean that when driving my car I had better believe in the objective reality of the other cars speeding along the highway, and I want the dentist working on my teeth to have a fairly precise confidence in where he is drilling. But still – the observer is inextricably bound to the “reality” he or she is observing. As Yeats asked, “How can we know the dancer from the dance?”  [I do like your way of describing this.]
            The strangeness appeals to me as an English major. It’s not that I am ignorant, which I am, and uncertain (ditto). It’s the fault of the universe, not me and my clumsy thermometers. One writer said that the Heisenberg’s German is better translated as “indeterminacy,” which properly locates the mystery outside of my uncertain mind.
            What a liberating [and dangerous] realization! Who cares that this uncertainty, or indeterminacy, only occurs at the subatomic level? It also occurs on my desk, currently piled with old receipts, a recipe for a bourbon cocktail we like (available on request), an unused microfiber cloth for cleaning my camera lens, scraps of paper listing birds we observed for the Backyard Bird Count, and three-days’ worth of to-do lists.
            (What may be at play on my desktop is not the Uncertainty Principle, though I am routinely uncertain about where my stuff is and what I wanted to do with it. No, it may be the Second Law of Thermodynamics, which another Amherst professor summarized as, “You can’t kick shit up a cow’s ass and expect it to spit hay.” Entropy rules my desktop, though occasionally Kim will overrule it.) [True physics.]
            Though it’s obviously a mistake to apply quantum physics to our everyday life, the uncertainty, and the accompanying sense that the universe is, at the deepest level, a mysterious place, yield an exhilarating sense of freedom. In a sense you choose the reality you live in. I know this is only true if you are looking at subatomic particles, and I know it is questionable whether you can apply quantum physics to psychology, but still . . .. Learning from a physicist in “What the Bleep,” I have made it a habit to consciously “create my day” when I awaken in the morning. I choose to arrange the electrons of my day the way I want them. So, there! Probability replaces certainty, and I find the humility of uncertainty more appealing than the tyranny of certainty.  [Again, I like this.] And Kim arranges her day’s electrons by saying, “EFFM,” which stands for something like “Enjoy every minute.”
            Physicist Neils Bohr reportedly said that a person who wasn’t outraged on first hearing about quantum theory didn’t understand what had been said. He was probably commenting on a person like me, whose lack of outrage is commensurate with my lack of understanding.

Niels Bohr and me

            Good, David.  It may not have been Bohr, but someone said, “Anyone who thinks they understand quantum mechanics must have bricks for brains.”

            Senior year at Amherst was my first serious exposure to quantum theory.  I have used it ever since.  One of the reasons why physics is fun is that even the most successful theories can be odd, and allow debate over a glass of beer.  The second law of thermodynamics isn’t especially controversial.  However, when it is applied at the atomic level to a few atoms, it can only be correct in a probabilistic sense.  Too much curiosity about this can cause hangovers.

            Radioactive decay was a huge enigma for many years after Becquerel discovered it in 1896.  Einstein helped explain the mysterious energy of the decay.  Rutherford did many important experiments.  He discovered the “half -life.”  Here’s an example.  Quoting from Wikipedia, “Francium is the most unstable of the naturally occurring elements: its most stable isotope, francium-223, has a half-life of only 22 minutes.”  Some of my colleagues make francium-223 in accelerators, in order to study its properties. Francium sits­ in the first column of the periodic table, beneath lithium, sodium, potassium, rubidium, and cesium.  All of these have isotopes that apparently live forever, unlike francium.  Suppose my colleagues make a million francium-223 atoms.  After 22 minutes, they will have only half a million left (along with some messy “decay products”).  Actually, that’s not true; they will probably have somewhere between 499 thousand and 501 thousand.  No one can predict exactly how many.  If you do the experiment many times, and then plot the distribution, you get a bell-shaped curve centered at a half million, and with a mean deviation of about a thousand.  This reminds me of human mortality and human actuarial curves.  But the differences are dramatic.  If half of humans die before age 75, we don’t call this a half-life.  75 years is a pretty good life, but the end is in sight.  But the half million 22-minute-survivor francium-223 atoms haven’t aged a bit!  After another 22 minutes, half of them (250,000 plus or minus maybe 500) will still be around, perfectly healthy.  After 10 times 22 minutes, the surviving population of francium-223 will be 1000 plus or minus 30.  After 20 times 22 minutes, there will probably be 1 plus or minus 1 francium atom left.  The one last survivor hasn’t aged at all, and has a life expectancy of another 22 minutes.

            This is an example of atoms behaving “probabilistically.”  Probability is fundamental to quantum mechanics.  Einstein did not like it.  “God does not play dice.”  Maybe if we really knew exactly what was going on inside francium-223, we could give each a physical exam, and predict with some accuracy when each would decay.  However, sophisticated experiments have now convinced physicists that predictions at the atomic level are necessarily probabilistic.  We will never be able to predict when a particular francium-223 atoms will decay.

            Now here’s my attempt to puncture some of David’s fun.  An electron, one physicist said, must be regarded as being “at once everywhere and nowhere.” Tiny particles blink in and out of existence, jumping from one place to another in a ”quantum leap,” without actually moving through the space between them. Paired particles, at a distance, instantly “know” what the other is doing. 
            Why would anyone believe that?  Here’s the reason.  The laws of quantum mechanics tell us how to compute a “wave function.”  This is a mathematical object that evolves deterministically, governed by Schroedinger’s wave equation.  It’s a theory that works beautifully to describe and predict atomic behavior probabilistically.  But the wave function itself “behaves” deterministically.  Which is real, the deterministic wave function, or the probabilistic atoms that can be “seen” (somewhat indirectly) with sophisticated apparatus?  Or, both?  I am not sure.

            Bohr’s view of quantum mechanics continues to dominate.  It is called “the Copenhagen interpretation.”  It allows me to believe that the wave function is not a real thing.  It is just a tool for predicting (correctly) the probability of any kind of future behavior of atoms.  The wave function evolves in time like a wave.  Its behavior is pretty weird.  If it passes through a plate with two openings, the part of the wave that went through one opening “interferes with” the part of the wave that went through the other, very much like water waves or light waves.  But, if I were more technically competent, I could do an experiment to see where the particle actually is at a moment I choose.  The wave function does not predict exactly where, just the probability of being where I find it.  If I do a measurement that tells which opening a particle goes through, then the particle with known position is temporarily not wave-like, and there are no longer parts of the wave function going through the other opening.  There is no interference.  The wave function has “collapsed.”   This is upsetting.  Why is there such a beautiful wave description, if the wave collapses when it is measured?  If I decide that the wave function isn’t a real thing, it is less upsetting.

            There are tough questions (for example, how does quantum theory describe observation) that the Copenhagen view doesn’t try to answer.  In the future, when quantum theory is better understood, there will surely be a better way to picture and describe the strange microscopic world of particles.  In the mean time, I am happy that I have learned some tools that enable me to predict things.  Now that I have retired from teaching, I hope to continue doing this.  I will not waste too much time worrying about reconciliation between the weird and perhaps unreal waves, and the definitely real signals from the measuring apparatus. 

C. P. Snow might conclude that scientists and non-scientists still have a ways to go, but we are trying.

Meanwhile, the uncertainty that leads to both outrage and a sense of mystery is something that humanists find more comfortable. Think of people you know. Is it possible to know their identity and their path? Do people have a single core identity? Is our human unpredictability, other than by calculations of probability, not just due to the ignorance of those attempting to predict but rather the same kind of unknowableness in human nature that we find in subatomic nature described by quantum physics?

Speaking of unpredictability, I think I’ll try spinning Kim again. I’ll let you know how it works.

Jere Northrup commented:

Dave and Phil, great post. I love it.
 So let me chime in with my understanding, or non understanding, of what you are saying, or at least talking about, if not saying or understanding.
 You said  “Though it’s obviously a mistake to apply quantum physics to our everyday life,…”  I say True, unless perhaps you want to call someone on a cell phone.  However, you can feel much better about it all if, instead of applying quantum physics to your everyday life, you apply your everyday life to an understanding of quantum physics.  Just look at all those electrons, and photons, and whatever, as if they are alive and conscious.  They remember, make decisions, have good days and bad days.  They are as probabilistic and weird as individual teenagers and some of us old fools. But in aggregate and over time it all seems to work out. The universe is still a beautiful place.
 As I remember, the three laws of thermodynamics are: You can’t win; You can’t break even; and, You have to play.  Knowing you can’t break even, the Second Law of Thermodynamics, is then pretty comforting. We are all in the same boat or mud puddle (your choice), and I do believe that “In a sense you choose the reality you live in”  is valid, and that it is as valid for us as for our understanding of subatomic particles.
 As for that entanglement thing between you and Kim, I am still not sure who is spinning whom.  Maybe we should ask George McDougall.

John Perkins commented:


What a great rabbit you found down that rabbit hole!  (And Phil Allen's annotations were very helpful, too.)  And English major though you may have been, it looks like the physics you took made a difference in your life.  For the better, I hope.

One comment on C. P. Snow: I didn't read him at Amherst, but I finally picked up his little 1959 book, because I thought "I should."  What surprised me was the context in which he put the gap between scientists and non-scientists: I had expected it just to be about the so-called "educated man."  Wasn't it something like the "whole man" at Amherst in our time?

Snow did write about the gap, but my surprise was to find that his context was the Cold War.  The USA and UK, he said, had better become better at seeing the importance of science and technology, because if they didn't the USSR would better help the poor world than the USA and UK.  And Snow certainly thought the USA and UK should win against the USSR!  It seems now he overestimated the Soviets, but I was fascinated that the gap was important to him, because it would prevent a USA - UK victory.  Maybe he wanted the English majors to lend a useful hand?  (If my observation is correct, I still can't hook it to uncertainty or determinism, but that's for another day.)

Anyhow, thanks to you (and Phil) for the good read.


And from Dr. Roger Mills:

Dr. Elmore Leonard learns statistics...

So, I was in the office a few weeks ago and Frankie comes in for a check up.

I say, "How ya doin', Frankie?"

He says, "Doin' good, doc, doin' good. I'm 38 minutes old, and feelin' fine."

So I do a physical and some lab tests, and sit down to talk with him.

"Frankie, based on your age, weight, and mass, I'm think your're a francium molecule."

"Sure, doc. I know that. One of Phil Allen's buddies made me."

And then I try to convince him to stop smoking. I tell him how bad it is for him, how it could screw up his electrons, or even loosen his Higgs boson.

He looks at me and says, "Doc, you don't understand probability. What's the chance of heads or tails on one flip of a fair coin?"


"No, Doc. Probability don't apply to single events. You flip the coin once, it's either heads or tails. No probability. Us francium molecules, we learn that early. We ain't healthy, we're francium. Make enough of us, one could last a hundred years. But if you're just one molecule, you might as well smoke and enjoy it, cause when your time comes, it ..."

Then he decayed, right there in the office. I had to get the room decontaminated. 

1 comment:

  1. Reading your blog made me think about sailing on the ocean and watching all the wave action and how the currents and wind change the direction of the waves and their formations. Now, as I'm watching the snow fall, I can think about Quantum Physics and how these particles are moving through space, or are they moving?