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    Quantum Corner: Introduction

    I'm hoping to start a fairly regular set of postings on Quantum Mechanics and/or other weird science that fascinates me. However, if there's no interest (after all, it's outside the normal scope of all things dagblog), I'll drop it. With that in mind, I thought I'd start with an overview of Quantum Mechanics, talk about how it's really weird, and give my interpretation of it, all without delving into math or jargon. Well, I'll try to at least save any such delving for the comments section.

    For those who find QM confusing, I offer up these quotes:

    Those who are not shocked when they first come across quantum theory cannot possibly have understood it. - Niels Bohr

    If you are not completely confused by quantum mechanics, you do not understand it. - John Wheeler

    It is safe to say that nobody understands quantum mechanics. - Richard Feynman

    Quantum mechanics makes absolutely no sense. - Roger Penrose

    Now, for the two-cent tour of one of the simplest experiments that demonstrate the weirdness of quantum mechanics, the double slit experiment:

    The experimental setup is quite simple. There's a light (or other particle) source, a card with two slits in it, and a detector. If you cover up one of the slits, you find that the majority of photons (or other particles) lands along the line connecting the source and the slit, with a predictable fall off the further you get from the intersection of that line and the detector. Do that with the other slit, and you find the same, simple, pattern, but moved as one would expect relative to that slit's location. So far, so good. Now, if you uncover both slits, you get what's known as an interference pattern. That is, you get a series of ripples (far more than just two), with alterations between a higher probability of finding a particle and a lower probability of finding a particle. As it stands so far, if we're just talking about light, this is not a new experiment. It's what led to the understanding (before Einstein's photoelectric effect experiment suggested otherwise) that light is a wave. If you've ever watched two sets of waves interact, you get this same sort of interference, so that's a nice, simple explanation. The only problem is, the explanation is wrong (or at least incomplete).

    Let's switch the discussion from light (photons) to electrons. You get the same results. Now, the simplest explanation (and one that was posited) is that electrons passing through one slit are somehow interacting with electrons going through the other slit, and that interaction is responsible for the interference pattern. However, it's possible to send one electron through at a time. An electron can only go through one slit or the other, right? Well, you'd think so. However, if you do this experiment, one electron at a time, you still get that same interference pattern.

    Bizarre, right? Well, how can we explain it?

    That's where QM comes into play. It posits that these electrons have probability waves that describe their probable locations, and that these waves can interact with each other, even when they're describing a single particle. So, there's a probability the electron went through one slit, and a probability that it went through the other slit, and these probablities actually interact with each other!

    But... What if we get creative and try to determine which slit the electron actually went through? Several ingenious experiments have been set up to do just that. Here's the catch, however: any experiment that reveals which slit the electron actually traveled through destroys the interference pattern on the detector end. In jargon (OK, so there's a little bit), we say it collapses the electron's probability wave. (Schrödinger's cat, see also.)

    Now we're going to stray a bit from the world of physics into the world of metaphysics, because we're going to ask "what really happens"? Here's where there's a lot of disagreement (most of it amicable, however). For a sample of what I mean, check out this Wikipedia article. Personally, I'm keen on the many worlds interpretation, or maybe the many minds interpretation. Why? Well, essentially, this collapsing I just mentioned is caused by so-called "conscious observers" making an observation (or measurement). However, I'm not keen on putting consciousness in a special box with a pretty bow around it (as if the rest of quantum mechanics makes any sense!), so I've struggled with how it is that consciousness has the effect it does. I then considered the anthropic principle, which states that the universe is the way it is because otherwise we wouldn't be here to observe it. Let's put that another way: if you flip a fair coin 100 times, you're going to get a particular sequence of heads and tails. The odds of getting that particular sequence is 1:2^100, or (very) approximately 1:1,000,000,000,000,000,000,000,000,000,000. Yet, that's the sequence you got! Amazing, right? OK, not really, because any other sequence would've had the same odds, and you had to get one of them. Anyways, that's kinda-sorta the idea behind the anthropic principle. How does that relate to conscious observers collapsing probability waves? Well, it turns out that maybe we're not collapsing them, but we're uncollapsing ourselves (or, more technically, we're coupling our future experiences with that electron). I.e., when we make an observation of an electron, the self that might have had the electron going through slit A is decoupled from the self that might have had the electron going through slit B. Confused? Reread those quotes again.

    I strongly welcome any comments, whether it's about what I've written, how I've written it, or how some other interpretation is even better.



    Giddy up. I love this stuff. But...I think that you need to slow it way down for the less quantumly inclined. I even had trouble following in places, and I've performed the double-slit experiment and studied the philosophy of physics.

    My suggestion would be to break this post into multiple articles. First, lay out the basic idea of a quantum state with reference to the double slit experiment, an ambitious undertaking in and of itself. Second, help us understand just how weird quantum states are, e.g. Schrodinger's cat. Next, introduce the metaphysical explanations one at a time in separate posts so that we can digest them and attempt to make fractionally intelligent comments.

    If you want to do a series, I can create an item in the dropdown menu for it. Lemme know.

    For my own part, the bit that has always weirded me out is the role of Plank's constant in the indeterminacy equation. I can wrap my head around the idea that in practice quantum observations change the conditions of the experiment and that it's physically impossible to measure the velocity and position of an electron at the same time. But I cannot make sense of the idea that there is a fixed degree of precision below which it's not only impractical but a violation of metaphysical principles to measure the velocity and position of a particle. It seems so arbitrary.

    PS Here's a friendly cartoon version for readers who didn't make it past the second paragraph:

    Wow, that's an excellent cartoon. There's no way I could come close to explaining the double slit experiment as well as it did. So, you've already "written" the first article for me! :)

    By the way, if you're into this kind of stuff, and you like cartoons, I strongly recommend Gonnick & Huffman's Cartoon Guide to Physics.

    If I get a second vote of interest, I will start a series. I haven't thought too hard about the origins of ħ, but if I do start a series, I'll be sure to include a discussion on it as well.

    Yeah, go for it, Nebton. Dagblog readers can handle this stuff. And even if some of us zone out, there's no shame in trying and failing. To the end of his life, Dr. Einstein couldn't quite wrap his prodigious brain around the quantum universe. And I'm told he was otherwise fairly smart.

    In passing, my condolences to Professor Schrodinger. He could hardly have predicted that sealing his old, sickly cat in an airtight, soundproof, foodproof box would so negatively affect its health.

    The Dr. Quantum cartoon was a good find, Genghis.

    So, OK, Genghis, go ahead and create the category, and make this the seminal entry in that category, if you would.

    OK, give me a name for the series.

    I like "Quantum Corner".

    Btw, when's the next installment of "The Heretic's Bible"? :)

    I would have picked, "Quarks Gone Wild!" :)

    Done. Alas, Heretic's Bible is simmering on the backburner along with other stuff that I haven't had time for. It was supposed to be a book, but when David Plotz of Salon published a similar book, I abandoned it and published what I'd completed at dag. What I'd really like to get back to is News From the Future.

    I thought I missed News from the Future, but then I interacted with the future and found I didn't feel like I missed it anymore. It was weird.

    Perhaps the greatest irony in Einstein's life is that he is partly responsible for ushering in Quantum Mechanics with his work on the photoelectric effect. In fact, many people don't realize it, but that's what he got his Nobel Prize in Physics for, not special or general relativity.

    By 1918, Einstein was pretty confident he'd win a Nobel; he just wasn't sure for what. So he offered his first wife, whom he'd been trying to divorce, the money that came with the award (perhaps half a million in today's dollars) in exchange for her agreement. She thought about it for a few days, then concluded it was a pretty good bet. Four years later, she collected in full.

    Though a radical thinker, Einstein's instincts were all about simplifying and unifying. He tried mightily to mesh quantum mechanics with relativity, but never could pull it off. I'm sure if we all put our minds to it, we here at dagblog will succeed where he failed. We'll cut a few corners if we have to.

    Neb, I love this stuff too and I have absolutely no idea what you're talking about. A few years ago on Science Friday on NPR, they were talking about companion atoms--the idea that every atom has a twin somewhere in the universe and when a force is exercised on one, the other one feels the same force, no matter how close (right next to each other) or how far (one in your kitchen and the other hanging around somewhere in the neighborhood of Jupiter) the distance. I found that idea so incredibly cool and at the same time almost impossible to believe. 

    I've been mulling around writing a post about the energy in group dynamics, which I suspect (with zero scientific training and even less evidence) is somehow related to metaphysics. Maybe I'll get around to it eventually.

    That companion atoms thing sounds like something dreamed up by string theorists (as I understand it, in one of the M-brane versions of string theory, very large distances and very small distances can be interchanged, as long as you're also willing to do a few sign inversions, etc., to the laws of physics). Eventually, I'll get around to talking about string theory, as well. I only wish I could find a good book on string theory that was written for scientists, but not for string theorists. I'm not sure if I've even found one written for string theorists, but I've found several written for lay people. Those books are OK, but I'm wanting more than they can give me.

    It almost sounds like O is describing quantum entanglement.

    Yeah, you're probably right.

    Yep. I was. I just wanted to see if anybody was smart enough to follow my brilliance. Good job.

    I'm of the mind that the dust-up over interpretations doesn't matter much.  To paraphrase Alan Watts, asking "Why this universe?" makes as much sense as asking "Where is this universe?"  What matters is that the theory accurately describes the universe in which we live.

    Spoken like a true scientist, or even more so, an engineer.

    The philsopher in me isn't satisified, however.

    On a related note, what do you think happened before time began?

    I have no idea and no way of knowing.  The technology required to obtain this knowledge certainly doesn't exist and might not even be possible.

    Maybe there is no "before time began".  There could be a Big Crush counterpart to the Big Bang and the whole show might be cyclical.  Or we might be totally wrong about what time is and how it works.  There's some very interesting theoretical work going on along these lines.

    But philosophically, I'm just okay with not knowing.  Self-awareness is central to my philosophical outlook.  Part of that self-awareness is trying to recognize limitations.  One of those limitations is knowledge.  Simply put, I can't know it all.  No one can.

    So, I tend to agree with Feynman about not knowing.  I'm really okay with it.  It's alright to know that I don't know.  It's alright to wonder.  Knowing everything would make life a lot less fun I think.

    It was really meant more as a zen question, such as what is north of the north pole…

    I'm also OK with not knowing, but I'm not OK with not trying to know. :)

    Since you posed the question, Neb, maybe what existed before time began was/is more time -- just running in the opposite direction.

    The Big Bang couldn't help but produce equal amounts of matter and antimatter. Yet our visible universe is predominantly matter. Doesn't make sense. I know most of the newly created particles mutually annihilated each other within a split-second after the Bang (fueling our universe's spatial expansion) , but what's left should be 50-50. To my mind, there has to be a "place" where the missing antimatter went.

    There's only one candidate: the other "side" of the Big Bang. As the time clock began running, as much excess antimatter was caught on one side as excess matter was on "ours." So at this very moment (although 28 billion years ago in a straight line) there exists a demi-universe that looks virtually identical to ours: The same physical laws will have produced billions of antimatter galaxies, solar systems and planets, with billions of antimatter people and animals strolling around on them. I sometimes muse that there's an antimatter version of me right now typing up his contribution to golbgad.

    Another possible answer is the same answer to what happens if you keep going north after you reach the north pole. I.e., Stephen Hawking posits that the big bang was a time-space singularity such that "before" and "after" are interchangable at that instant of "time". I'm not sure that he's right, but it's an interesting way to think about it.

    Frankly, I found Hawking's Brief History of Time a letdown. He tells a compelling story, then goes all vague and fuzzy at the end. In any case, "before" and "after" are interchangeable in my scenario as well. The antimatter demi-universe would be every bit as real as the one we see every day; in it, just like here, time would seem to have begun with the Big Bang.

    I'm with you on his book not being complete enough.

    I was lucky enough to hear him "speak" in person at the Atlanta Civic Center. Although I enjoyed it, I also wished he had gone into more detail then. After all, it was the American Physical Society. It's not like he had to treat us the same way he would a lay audience.

    Last summer, I attended a panel discussion on cosmology in which everyone was kinda freaked because there was too much dark matter that couldn't be explained by current theory. It felt to me like the pervasive dissatisfaction preceding a paradigm shift that Thomas Kuhn described in The Structure of Scientific Revolutions--when scientists keep trying to tweak existing theory to account for inconsistent data, and then someone comes along with a much simpler alternative that blows away the old ideas.

    Kuhn is a really fascinating thinker.  The whole debate between Kuhn and Popper is worthy food for thought.

    For those of you who love Kuhn, I also recommend Tenner's Why Things Bite Back. I found several similarities with The Structure of Scientific Revolutions.

    Also, it's worth pointing out that Kuhn was not a Kuhnian.

    Perhaps you could be more specific here.  The only reference to Kuhn not being a "Kuhnian" was a quote attributed to Freeman Dyson.  The context given would seem to imply that Kuhn perhaps didn't agree with the way that his work was interpreted by some, but the literal interpretation of your assertion, which would seem to be that Kuhn didn't really believe what he said he believed, seems questionable to me.

    Although the Wikipedia article only attributes it to Dyson, I'm fairly certain I've seen this from multiple sources. My assertion was not meant to be taken as suggesting that Kuhn didn't really believe what he said he believed. In fact, your interpretation of the context is correct: Kuhn was really interested in distancing himself from those who proclaimed themselves as Kuhnian. There used to be an article on Wikipedia about Kuhnians, which has since been removed for some reason, that explained that these people ran with Kuhn's ideas and became convinced that scientific knowledge is subjective. Some Kuhnians will go so far as to say a witch doctor's practices are no more or less legitimate than "civilized" doctor's practices. I doubt they'd really feel that way if they had a serious illness and were given a choice as to which doctor to go to, though.

    Just to be crystal clear: I deeply respect Kuhn. I have little respect for Kuhnians, however.

    Thanks for elaborating.  I had guessed that this was your intended meaning, but I also figured that you'd be perfectly capable of explaining it.  In that case, why guess?

    I think the debate between Popper and Kuhn is incredibly fascinating.  Popper's principle of falsification is incredibly important (like Kuhn, Popper's thesis has also been misconstrued), but Kuhn's narrative of revolutions is compelling.  Or maybe we should say Polanyi's narrative? ;)

    I tend to view Kuhn's theories as a form of punctuated equilibrium (a concept that came out after his work), so that it's merely built on top of Popper's evolutionary framework and is not a challenge to it per se.

    I see this was written in 2009 but hope you are still considering this because it sounds cool.  I would love to see you create more on this.  I have been trying unsuccessfully for years to start a String Theory book club so I would be interested in hearing your thoughts.

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