Home Forums Deep Time Journey Forum Matter, Carbon, Mystery and Wonder, a Salon Reply To: Matter, Carbon, Mystery and Wonder, a Salon

#2862
Karen Chaffee
Participant

Salon Two was ‘quantum weirdness”.
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In a way, we went off topic from our theme ‘the carbon atom’, but people wanted to do it and I was interested to learn about the topic.
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First, we reviewed some concepts from our first salon. To emphasize that the protons and neutrons form the nucleus, we played a game to learn about the STRONG NUCLEAR FORCE.
A good discussion is found in the book “Atom” by Isaac Azimov; I’ll excerpt: “We can imagine protons and neutrons constantly exchanging (mesons). The positive charge transfers (carried by meson) from (proton to neutron) in exceedingly rapid alternation. No proton can feel repulsion, because before it has time to react it is a neutron.
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I imagined a game of ‘hot potato’ with my guests. (Azimov had the same analogy.) We all stood. Some of us had a green balloon—a meson—and that made us a proton. If we were next to another ‘Green Balloon Carrier’, we had to give our balloon away quickly so that we didn’t repel each other and explode the nucleus. In this way, supposedly, the actual nucleus stays together. (Azimov and other authors go on to add some further ideas to this picture.)
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HOWEVER, my guests felt confused by the science and asked multiple questions. This made it hard to proceed to the next game I envisioned, beta decay. I had envisioned us tossing out a little spongy toy that lights up, while at the same time, changing a neutron to a proton (adding a green balloon), thus demonstrating WEAK NEUCLEAR FORCE. I meant to have us count our protons (balloons) and discover what new element we had made. I also meant to demonstrate positron emission. We DID do these games, but extremely rapidly; too fast to make sense, I’m afraid. Clearly, these games and activities with the nucleus would have to another salon—and a really good one, too, probably. Over fifteen (!!!) minutes had passed; I had to move on.
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To remind us of spin, a guest (Darcy) turned around twice while balancing a glass on her palm. I tried to demonstrate conservation of angular momentum with guest holding glitter arrows and me with a mirror; and THAT has to be its own salon.
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Now we had to go to our main event.
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A. Spooky Action at a Distance.
We placed right- and left-handed (paper) gloves in separate envelopes. I had two people turn away from each other; one guest opened her envelope. (Glove was left-handed.) I sad: “We know that the other envelope contains the right-handed glove even if we were a millions miles away, correct?” Yes, correct, but not so spooky. But wait.
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B. Next, I had to reemphasize wave particle duality. I did a terrible job, I think. But basically, people had to understand that small particles are waves and can create interference patterns if they go through two slits. If we try to examine them, the waves turn into particles, and go through one slit or the other, and the interference pattern disappears. Remembering Dewy, I played a lot of confusing games to help us discover this on our own; I think next time, I would just say it. Sometimes, it’s just better to tell people something.
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(From a book I am reading now, “Particle at the End of the Universe” by Sean Carrol: An on-line contest to describe quantum weirdness in five words produced this winner: ‘Don’t look: wave. Look: particle.’)
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C. Weird Effects: I used as my model a book: “Where Did All the Weirdness Go?” by David Lindsey. Here’s my outline, which I hope is basically correct, I am doing my best to interpret the book and this isn’t my field. I will recommend the book to readers here.
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I. Two Slit Experiments
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Send the particles one at a time (even years apart!). They hit so as to make an interference pattern. Interferes with ‘itself’. Each particle is a part of a wave function. It isn’t really a particle. It has information for all the other particles contained in the wave function
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We think that when they come together they ‘interact’ with each other to form the pattern. But they don’t. They behave as a wave function, a single quantum entity. No matter how we word it: each particle (or the particle’s wave function) is aware of the second slit while it ‘goes through the first’.
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BUT: If you cover one slit, and then another, and send them one at a time, they do not make a pattern.
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II. Now install behind one slit, a detector. The interference pattern vanishes. The particle has been ‘caught’ (i.e. we ‘looked’), the wave function collapses. _Before_ we collapsed the wave function–somehow particles are affected by both slits. After detection—the particle has gone through one and not the other.
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II. Delayed choice experiment: Beam splitter
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Does same thing as two slit experiment—creates interference by bouncing particles off mirrors and reconverging them.
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BUT NOW, we can put the detector a long way after the slit—the particle has to have decided what to do BEFOREHAND.
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The particle going through doesn’t know what kind of experiment it will be: a ‘look’ / ‘where is the particle’ experiment or a ‘don’t look’ / ‘create an interference pattern’ experiment.

We can imagine the path is long enough that someone can toss a coin and decide randomly—YET somehow the particle still knows what kind of experiment it will be—before the coin is even tossed.

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III. “A vs. B” and “Light vs. Dark”
This is tough and complicated in any book I read; I will refer you to this excellent article by Timothy Ferris1, where he calls it “Sweet Sour Hard Soft”. Basically, it describes how the structure of the world changes itself to keep you from making a measurement that absolutely you have cleverly set up to BE ABLE TO MAKE! (But the universe is one step ahead.)
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IV. Spooky Action at a Distance, revisited.
A neutral pion (a type of particle) decomposes into two electrons; one must be spin up and the other spin down (because total spin of the universe is conserved) and now they travel far, far apart.
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We measure spin of these electrons with a magnetic field. If one is up the other is down. BUT, if we turn our field sideways, one is left, the other is right—they can be millions of miles apart and it would work.
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It is as if the quantum world had never heard of space–as if, in some strange way, it thinks of itself as still being in one place at one time. Such behavior is called nonlocal.
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Three explanations for “Quantum Weirdness”, called “interpretations,” have emerged. 1
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a. The first, the Copenhagen interpretation, (Neils Bohr) asserts that we should simply accept that we cannot know the state of a quantum system until it is measured, and so we should stop worrying about it. It is pointless to speculate about whether the missing information “exists.”
b. The second, or many worlds interpretation, says the entire universe splits, with each act of measurement, into two universes. (Hugh Everett) Before measurement, both outcomes coexist. After measurement, the other result carries on in a separate universe. An infinity of other universes are born.
c. hidden-variables interpretation. (David Bohm) He calls the weirdness quantum potential, a gently acting field. Quantum potential would seem to violate special relativity– sending signals that travel at faster-than-light speed.
‘We humans, having come along when the universe was already billions of years old and are big creatures, able to see stars in the sky but not atoms in an apple, but the universe was not always big and classical. Once it was small and quantum, and possibly it has not lost the memory of those times. It may well turn out that
effects are woven through the universe in something like the way that a chef folds a cream into a sauce.’1
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Here is a clue to how it might work: Photons do not “experience” time.
Particles that have mass must travel ‘distance’ slowly. Photons travel distance at the speed of light—they do not travel in time. So a photon “traveling” from point A to point B does so, from its point of view, in zero time, meaning that, in the photon’s sense, the two points aren’t separate! Bohm and others have likened the implicate (i.e., folded in) universe to a hologram. Shatter a hologram, put one of its fragments in the laser beam, and what you see is not a piece of the original image but all of it.

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I would like to say that next, Jeff Buechner gave an excellent talk about logic and quantum weirdness, apparently giving us his original, unpublished thoughts (so I won’t ‘publish’ them here xz.) This was the part of the salon got truly neat. We ended there, and agreed to meet again.
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To debrief this salon, and to encapsulate my guests comments: Once again, I tried to do too much. Clearer, simpler, please!! Less is more! Also—I forget that my guests might have forgotten something, thus I should hang posters showing what we learned last time, so they can look at them. Still, they had fun, got the ‘gist’ of it, and are willing to come back!
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My next salon will be back to the main theme: How the sequence of the big bang affected the carbon atom and matter and life as we know it. I am reading a lot to prepare. We will discuss the Higgs field, breaking symmetry, the particle zoo, inflation, the forces, and we will try ‘to not do too much’.
#1. http://www.stanford.edu/dept/HPS/writingscience/Ferris.htm from The Whole Shebang: A State-of-the-Universe(s) Report (1997).