an analogy for particles with spin one-half

This may seem like an odd diversion, but John asked about it just this morning so I thought I’d share with the rest of the class.

Electrons, in their secret life as wibbly-wobbly quantum particle-wavey things, have a property called spin. To quote a handy article I just ran across:

One of the things that was clear from experiments was that electron have spin. A first naive picture of an electron – this is not an accurate picture but it’s a start – is as a tiny ball with electric charge – which is what flows when a current flows in a wire. If you spin a ball of electric charge, the electric charge goes around in a circle. You effectively have a tiny current going around, and when you have a current like that you have a magnetic field – the electron becomes a tiny magnet. The presence of that magnetic effect is pictured as the electric charge spinning around. If the electron was still, it wouldn’t have this magnetic effect.

It gets better:

Among the many counterintuitive properties of the electron is the fact that it has spin one-half. This is the mathematical way of saying that if you rotate an electron through 360 degrees, it doesn’t look like it did before you started! There is no parallel for this in our everyday world – we are accustomed to being able to turn objects through 360 degrees and get them back to where they started.

Oh, but there is a parallel in the everyday world, or at least in my slightly-twisted mind. Think of it like so:

  1. Imagine a reel-to-reel film projector. Running a short length of film through end-to-end works like you think it would.
  2. Tape one end of the film to the other; now you have a continuous loop of film that repeats itself. This would correspond to a spin of 1, because it looks the same after one loop.
  3. Now tape one end of the film to the other backwards, to make a Möbius strip. The film still loops, but now it does one loop with the frames reversed left-to-right. It doesn’t repeat itself exactly until the film has looped through twice, corresponding to a spin of 1/2.

Does this mean that electrons are actually tiny loops of film? No. It only provides an analogy for this one property, and even then it might not go very far. Still, as soon as someone says “there is no X”, I have to find a counterexample. :)

the rule of telling children anything

I had to post this in response to the flurry of rumors around NASA’s announcement that this Thursday they will “discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life.”

The rule is simple: When you tell a child anything, they will ignore most of it and leave only the words that benefit them.

Toddler version:

No, don’t run into the street.

Blah blah run into the street.

Young child version:

We’ll go to the zoo if there’s time after the store and lunch.

We’ll go to the zoo blah blah blah.

Older child version:

If you clean your room, you can borrow the car on Saturday afternoon.

Blah blah you can borrow the car blah blah.

Journalist version:

NASA will hold a news conference to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life.

NASA will blah blah discuss blah finding blah evidence of extraterrestrial life.

…and there you go. Good luck on Thursday, guys.

assumptions and their ills

Yesterday I did something dumb, and I only realized it today because I don’t trust an easy success. Let’s see if you can spot the flaw in my reasoning:

Background:

  • A process (X) is run on a series of items in a queue.
  • Items are added to the queue continuously, about 500 per hour.
  • A processor (Z) is started once an hour. It performs X on all the items in the queue, then quits once the queue is empty.
  • If there are any errors, the processor emails them to me after it quits.

The problem:

  1. I noticed 100 random failures in process X each hour.
  2. I hypothesized that X is failing due to intermittent system unavailability.
  3. I checked the hypothesis by looking for clusters of X failures at times of high load. (There were.)
  4. I “fixed” it by pausing the Z processor for 60 seconds whenever there’s a failure (to let system resources recover).
  5. 12 hours after the fix, I got no failure emails and declared victory.
  6. Not so fast: Not only did I not fix the problem, I caused something worse.

Can you figure out what I did wrong? Continue reading

a cat… standing up!

These gentlemen are from the future.

These gentlemen are from the future.

You may have noticed how quiet Global Spin has become, yet again. With the rise of Twitter and Reader and Tumblr and other such thing-share-ers, our little community no longer has much reason to post their thoughts to a group blog.

In response, I’m quitting!

checks notes Oh wait, that’s not it… shuffles papers One sec, it was right here…

Right! In response, I’m going to keep posting the same old things on Global Spin as always. (In a word: monkeys.) I won’t even promise to post more often, because we’ve all seen through that little shadow play. Or something.

For those of you looking for a little more regularity and a little less depth, I give you a cat… standing up! (Oh, and I might also share some other things over there, because it’s what all the kids are doing these days.)

That is all.

the 42nd monkey

Lee shared a thoughtful and entertaining Cracked article* by David Wong about the Monkeysphere. In short, the idea is that we can maintain less than 150 relationships (our monkeys**), so there’s no way for us to care about everyone.

Lee also shared a Derek Sivers article that hits right in the gut. As Lee pointed out, reading the two together makes it obvious that the abuses Derek talked about came from people working outside their Monkeysphere. They ended up shouting at their email, not realizing there was a person on the other end.

After reading them both, I had to ask myself: Why do I think I’m different? I do try to treat people with respect, even when “people” are an abstraction so far removed from my life that I need complex software*** to remind me how to treat them well. I also interact with lots of people over the course of the day, far more than the ~150 my Monkeysphere would allow me to care about.

First I thought there might be some notable difference between in-Monkeysphere people and out-of-Monkeysphere people. Maybe I just follow a set of rules about interacting with people (see also: enlightened self-interest), without really feeling it on the inside. Then I read a tweet from Dave Masten:

“My dad’s leukemia just took a turn for the worse. Sad.”

That hit me in the gut, too. And then I figured it out. They *are* in my Monkeysphere. All of them. Sara and Valerie are in there. Dave’s in there. You’re in there, dear reader, even if I don’t know you at all. They’re the 42nd monkey.

Here’s how it seems to work, based on whole minutes of self-examination: one of my monkeys**** is an abstract monkey. Programmers might call it a variable, mathematicians might call it an equivalence class, and politicians might call it a constituent.  When I interact with someone who isn’t in my Monkeysphere, that person becomes the 42nd Monkey for that interaction, even if it’s only a few seconds. When the time comes to deal with someone else, they become the 42nd Monkey instead.

The 42nd Monkey suffered a loss. The 42nd Monkey is working toward a deadline. She slept badly last night, and she’s just trying to wake up. He’s glad it’s Friday. She doesn’t have a lot of time, but she’s willing to talk. He wonders if all this trouble is worth it. She hopes she’ll meet someone nice tonight. He’s awkward at parties. The 42nd Monkey, in short, is a real human being.

The 42nd Monkey isn’t so different from the other monkeys in my sphere, so I try to treat him with the same respect. More importantly, I realize I’m probably outside of the 42nd Monkey’s monkeysphere, so I give her the benefit of the doubt. She’s not yelling at me to make me feel bad; it’s because her child is crying. He’s honking at my car, not its driver.

Why does this matter? Because I don’t agree with David Wong’s conclusion that “it’s also impossible for them to care about you.” (Emphasis his.) I can be your 42nd Monkey just as you are mine. It might only be for 5 seconds, but if that’s the time you’re spending with me then that’s all it takes.

* I know! Can you believe it? Not a phrase I’d ever imagine writing.
** Yes, humans aren’t monkeys, and most of the images in the Cracked article aren’t monkeys either. Step back and embrace the wider point here.
*** A digression, but here’s an example from right now: My phone is told by my calendar application to remind me when someone I’ve never met is scheduled to call, so I’ll know not to send that call to voicemail, which I ordinarily would do because their caller ID isn’t in my address book.
**** There’s probably more than one monkey, but for now let’s assume it’s one monkey. (In a vacuum[4].) That way I can name it, instead of saying “Monkeys 42 through 42 + n, where n < 108″ each time.