Quantum Disentanglement – Part 1

When we come down from our speculations about what’s happening “out there” in the far reaches of the universe, we find ourselves not thinking about what we think we know, here in the zone of middle dimensions, but about what we really don’t yet know but have always wondered about. How did it all begin? We ask about those things that, 2000 years ago, Lucretius called “first beginnings,” those elemental things that everything around us must have resulted from. For nearly 1500 of those years we were stuck in another belief, that the sun moved around the earth. It was obvious, wasn’t it? Every morning the sun comes up, traverses the heavens and sets in the west. We’re now stuck on something else. That something else comes from a direct experience like the one those early astronomers had, something we notice every day.

We have been stuck on “particles” ever since some Persian or Greek sat on a beach and let the sand flow through his fingers and thought, “What if everything came from something like this?” How did we get stuck with this notion? The simple fact is that it’s something that  common sense tells us. We live in a matter-centric universe. We see objects that must be made up of things that are ultimately hard and impenetrable. It’s hard to grasp otherwise, even though from high school physics on we’ve been told how much space there is between our constituent atoms and how “cosmic rays” and other stuff go right through us all the time. But in today’s subject, quantum theory, it seems that everything is made up of tiny invisible particles that sometimes behave like what we’re sure they must be, hard little impenetrable substances, and sometimes like something we can’t see, like waves. And unfortunately, when we get down to the details, there’s a lot of evidence that doesn’t quite fit.

The ancients (and some not so ancient) saw that sometimes a planet seemed to move backward in its orbit around us. Explaining that observation without moving the earth out of its central place in our model required a change in the model; and because we couldn’t (for a lot of reasons we think are crazy now) throw out the idea that the earth was in the center, astronomers invented epicycles, little loops in the orbits of several of the planets. It seemed counterintuitive, but it explained, somehow, the apparent backward motion, and it stuck around for a long time.

We ran into a similar quandary 80 years or so ago in trying to reconcile the idea than sometimes matter at its tiniest scale seemed to behave one way, like little hard specks,  and sometimes another, like the waves in a pond. We couldn’t give up on the idea of particles, so it seems that we may have invented our own epicycles, this time in the form of quantum mechanics, to explain the apparent contradictions in the wave-particle observations. But this fix of the model brought along its own counterintuitive , even contradictory, baggage.

Let’s back up a little. More than to anyone else, modern physics owes an enormous debt to Isaac Newton, who gave us insight into most things we have tested and feel we can rely on here in the zone. But one thing he gave us that came into dispute was the nature of that phenomenon we know as light. Newton thought that light was made up of tiny corpuscles of something he didn’t yet know what to call but that would become known as energy. His notion was generally accepted until an interesting set of experiments by a young doctor named Andrew Young, in about 1800, who wondered if light might be more like the waves on a pond and might travel in the same way.

In what is known to this day as “Young’s Experiment,” he appeared to prove that the transmission of light, in fact. had much more the characteristics of waves than of corpuscles. Along with this discovery, of course, came a strengthening of the belief in another of Newton’s concepts, that of a “lumeniferous ether” a medium through which light was propagated, a medium like water which carried it’s waves.

Almost another hundred years passed before Michelson and Morley carried out a sophisticated experiment that appeared to prove that that Newton’s ether did not exist (leaving open the possibility that some other kind of ether, one that did not resist or slow down the passage of light, might actually be out there). A few years later, along came Albert Einstein, almost as great as Newton in his contributions to our knowledge of the world, who, with others, showed us that maybe light was more like what Newton thought it was, made up of little packets of energy, now to be called quanta.

As Darwin said in the conclusion of “The Origin of Species”, “From these simple beginnings……”, arose what we now know as Quantum Theory” (or more recently, as quantum mechanics)

One of the core principals of quantum theory can be expressed like this:

1.”Everything is made up of tiny things that sometimes behave as if they were particles and sometimes behave as if they were waves, and you can never tell, only speculate, using the laws of probability, which it will be.”

The short name for this principle is “wave-particle duality.” This seems to be the common understanding of the quantum mechanics faithful.

Now, along with this statement came a few paradoxes, that is, some apparently contradictory observations that are hard to explain. Like, “How is it that a particle can behave like a wave?, or vice-versa?, How can two particles seem to occupy the same space at the same time? Why does a particle change its appearance when it passes through a slit? How can two particles seem to be tightly tied together even at a distance” These arise from some observed behaviors we don’t quite understand when we search the experiments and some from the math we use to describe them. To get at these contradictions, we should, perhaps, be clear about the characteristics of those things we call particles and those things we call waves. Here are two simple definitions that we can start with, drawn from a paper on the concept of wave-particle duality by lgsims 96, (a user name, I would like to identify):

 Attributes of particles

A particle has mass, it is localized in space. Two or more particles cannot occupy the same space at the same time. A particle can have any relative velocity from 0 to almost c (the speed of light).

 Attributes of waves

An electromagnetic (EM) wave has no mass. It is not localized; it spreads out over a large volume of space. Many waves can occupy the same space at the same time. These waves have only one relative velocity c. They have attributes of wavelength, frequency, intensity and amplitude of the disturbance (electric charge).

Now, all the experimental evidence shows that quanta, of light and other forms of energy, sometimes behave as if they were particles and sometimes behave as if they were waves. and we can’t always be sure how they will turn up. In new repetitions of Young’s Experiment, it appears that even a single quantum of light behaves the same and gives equivalent results to those Young observed , much like the waves in a pond, just as they did over a hundred years ago. Does the particle change its nature and become a wave? And can it change back?  It seems, what we think of  as particles sometimes can occupy the same space, a phenomenon called superposition, something particles should not be able to do. And certain kinds of particles give the distinct impression that they can affect the behavior of other particles, sometimes at a great distance, s phenomenon the quantum physics faithful call entanglement.

The history of quantum mechanics involves many of the most interesting characters in the scientific world. They agreed on some things and disagreed on others. Niels Bohr, Werner Heisenberg, Gerhard Schroder, even Albert Einstein were involved. And some of those things were about what was real and what was not. Einstein and Bohr in fact carried on a mostly gentle debate on the subject for many years. Part of this resulted in the famous comment by Einstein, that he didn’t believe that God played dice with the universe. Finally, however, a group got together and discussed the whole thing and came up with what is now called “the Copenhagen Interpretation”, which is mostly what we’ll be talking about in Part 2. But you have to remember, not all of them were in agreement in Copenhagen, even though it didn’t descend to “something’s rotten in Denmark.”

Stay with me, more is coming.

About Charles Scurlock

Charles is a recently retired architect/planner and generalist problem-solver with a lifelong interest in science, physics, and cosmology, and the workings of the human mind. He has started this blog in the interest of sharing his ideas with others of like-(or not so like) minds.
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2 Responses to Quantum Disentanglement – Part 1

  1. Phil Allsopp says:

    Was Einstein referring to playing Dice with the universe?

  2. Thanks, Phil, for the correction. I think you’re right. I’ll fix it.

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