Posts tagged ‘physics’


Mach’s Principle

I wrote my 750 words again! (Answers to even-numbered exercises are in the back of the book.)

The blinking light on the side of your laptop computer actually represents the average heartbeat of every human on Earth who is within one mile of a monitoring node.

Which is approximately 45% of the population of the planet.

Most of the time it is rock-steady, as any excitement in one heart, or in one group of hearts, is exactly balanced through the vast mushy laws of large numbers, by the ebbing of excitement in the same number of hearts elsewhere.

And vice-versa.

But on some days, if you are watching the blinking light as I often do, you will notice it slowly subtly down, or speeding suddenly up, as somewhere there is a large anomaly, a sudden gasping, a thrill, an excitement, in the entire population of a small city in Rawanda, or every Girl Scout in the USA; or somewhere else an entire continent goes to bed, and on the other side of the world, due to an international holiday, their usual counterbalancers are sleeping in.

Because, vast and sprawling and numerous though we are, humanity is still finite. There are only so many left-handed people, only so many people about to open a soda can, only so many Lutherans. The number of religious sects is large, but smaller than the number of grains of sand on the beach, which is smaller than the number of atoms in one grain of sand, which is smaller than the number of possible Sudoku grids, which is itself still finite, and so smaller than nearly all of the positive integers.

Looking down Platform 29, across all those people waiting patiently, or impatiently, for the 6:45 to arrive, and thinking that each of them has a history, and a set of beliefs, a complicated web of preferences and fears, we are already far beyond the vastness that any one of us can comprehend (one, two, three, seven, many), but if all of those people were to vanish suddenly, spirited off by aliens or vaporized by more mundane means, the size of the world as a whole would be reduced by only an imperceptible fraction.

So your laptop’s light blinks, almost always, at the same steady pace, as all of our hearts (or the hearts of all of us within one mile of a monitoring node), average out into a signal with just one bit of content (“still the same, still the same, still the same”); all the complexity nicely smoothing out, a hill here balanced by a valley there, a hundred orgasms in one set of college dorms nicely making up for a hundred hearts drifting off to sleep in another set one time zone away.

Take a breath. Feel yourself breathing, and what it feels like to breathe. Feel yourself thinking, and what it feels like to think. If you are worried, feel what it feels like to worry. Feel your own heartbeat slowing. Look at the reflection of the blinking light on the Ethernet connector, or the shiny tabletop, or your fingernail. As your heart slows down, imagine that you can see the light slowing down, by the smallest imaginable amount.

Imagine that you can feel, somewhere deep in your gut or your inner ear, the Earth turning under you, and the stars whirling around.

It the Earth turning, or the stars? We know, these days, that motion in a straight line is relative; that jogger is the one who is moving, and I on the park bench here with my peanuts am the one sitting still, only because the math is simpler that way; but either one might be true. It’s not so simple for rotation, though, for things spinning around. Ernst Mach thought, at least if we listen to Einstein (and we might as well, since we listened to him on that whole “motion in a straight line” thing), that the universe has a large-scale structure (large as large, larger than anything), that determines what counts as spinning and what doesn’t; but I hear down at the corner pub that this is not true in all solutions to the field equations.

Feel your breath, and what it is like to breathe. Feel your heart beating, and what it is like to have a heart, beating. Watch the blinking light, and feel your heart beating with all of the other hearts (the ones within a mile of a monitoring node). Feel the Earth turning under you, and the stars whirling around you (with or without closed timelike curves). Be still.


Quantum Physics and (not really) Free Will

TWIN SPIN FINIt turns out that there is a well-known thing in quantum physics called “The Free Will Theorem”, developed by smart persons John Conway and Simon Kochen.

(I haven’t heard of this before, which I suspect means that, like L. Ron Hubbard’s science fiction, it didn’t exist in my original birth universe; I wonder if that means I’ve switched again recently. Always hard to tell.)

Anyway, the Free Will Theorem, which is described in two papers that are both quite readable really, is not actually about Free Will to speak of, at least not if you are a sensible compatibilist like we are, and I want to write down my thoughts here as to why and how that is.

What the Theorem actually shows is that, if some generally but not universally accepted parts of quantum physics and relativity are true, then if there is some behavior of some humans that can’t be predicted, even in principle if you knew every fact about the universe up to that point, then there is also some behavior of some elementary particles (as evidenced by the behavior of some macroscopic detection apparatus) that can’t be predicted, even in principle if you knew every fact about the universe up to that point.

Which is not a big surprise really; it’s hard to imagine a universe in which all elementary particle behavior was predictable but human behavior was somehow not, humans being made of elementary particles and all. But this Theorem puts a solid example under that intuition (as well as bringing up some other issues in physics that I won’t talk about more here).

Conway admits somewhere in the coverage of this that he chose the name, the Free Will Theorem, intentionally to get attention. But he’s also responded to criticism of the name by saying things worth noting.

The most obvious criticism is that being unpredictable even in principle isn’t the same as having free will (and if you’re a compatibilist it’s not even a necessary condition). Conway has said a couple of things about this.

First, he’s said informally that humans and particles are the same in this way, and since we say that humans have free will we should say that about particles too:

“That’s why I insisted on using this evocative language,” Conway says. “Many people thought I should say the particle’s behaviour is indeterminate. But it would be really rude if I told you that you were indeterminate! It’s the same property and I don’t see why we should be required to speak of it as if it were a different property. Our theorem says that if humans have it, then so do particles.”

But that’s sort of silly. The fact that humans and particles share some property X, and humans have free will, doesn’t imply that particles therefore have free will; it’s just a non-sequitur.

He’s also responded to the “randomness isn’t enough for free will” argument by claiming that the indeterminacy they’ve proved for particles isn’t just randomness. From that same link above:

and which action the particle does is free in this sense, it is not a predetermined function of the past. And that’s not the same as randomness, oh dear me no!”

Exclamatory cuteness aside, if “not determined by anything that’s come before, and not predictable even in principle” isn’t the same as randomness, I don’t know what is.

What Conway apparently has in mind here is that the randomness is weird and quantumly nonlocal: when the behavior goes from undetermined to determined, it does it at two places at once, and the places can be sufficiently far apart that no signal can get between them in time. That doesn’t mean it’s not random, it just means that as well as being random it’s also bizarre in the usual QM way; the Free Will Theorem doesn’t tell us anything particularly new about the weirdness, it’s just one of the three assumptions that it starts from.

Conway gets all sort of Penrose-like and speculates that while all the little “free decisions” made by particles usually sort of cancel out, our brains somehow avoid this canceling out, and that through some as yet unknown process our human-level free will pops out as a result. This, he says, makes the whole Compatibilism thing a moot point; since the universe isn’t deterministic, it just doesn’t matter whether free will is compatible with determinism. Compatibilism, the second of the papers says, is just “a now unnecessary attempt to allow for human free will in a deterministic world”.

Which is not quite right. :) Compatibilism is the recognition that indeterminicity is neither necessary nor sufficient for free will. Free will has to do with the freedom to express one’s preferences and goals in the world, not necessarily the ability to escape prediction by a hypothetical omniscient seer. Free will is possible with or without random or undetermined bits of fundamental physics (and those people who told Conway he ought to just say the particle behaviors are undetermined were right).

In fact free will requires that various of our actions are in fact influenced by, reflective of, if not determined by, past facts about the universe, those facts being the preferences, plans, and goals of the person acting with free will.

Hope that clears that up. :)


Friday, October 21, 2011

So I don’t understand this kind of spam:


My name is Franco Cavalier am sending you this email regarding in Purchasing Product from your company,I will like to know if you can ship directly to France , I also want you to know my mode of payment for this order is via CC . Get back to me if you can ship to that destination and also if you accept the payment type I indicated

Kindly return this email with your price list of your products..


201, rue de Grenelle

FR – 75357 PARIS


Slightly even more puzzling because it was sent to my work address (in ibm dot com), and it was sent from an email address of “dummy” at somewhere in France (with a reply-to at a gmail dot com address).

What value does anyone get by spamming out a request for lists of goods that can be paid for by credit card and shipped to France?

I suppose he might just be gathering email addresses in general, to spam or to sell? But surely if you want to test to see if a vast number of email addresses are valid, you’d want to maximize the chance that the person will write back, and in that case asking for lists of products that can be bought via credit card and shipped to France doesn’t do that.

They could just be validating a big list of email addresses by sending any old junk to them and seeing what bounces, but (1) email agents don’t send “no such user” replies anymore, as I recall, for exactly this reason, and (2) this is an awfully weird “any old junk”. I’d hate to think that some spammer address-collector had this nice a sense of the absurd.

Ah, mysteries, mysteries…

I just got The Physics Book from Amazon (I think I’d pre-ordered it or something), and it’s lovely. Bigger and fancier than I’d expected, a nice weighty hardcover with lots of short entries about interesting physics things, and great pictures.

You should get it, too! And not just because the author’s office is more or less across the hall from mine or anything. :)

I’ve just started reading it (the introduction and then a few completely random pages), but I think I will enjoy it greatly; it’s nice and bite-sized (a box of intellectual chocolates!), which fits my current (tiny) attention span nicely.

I’m also enjoying The Quantum Thief quite a bit, in the digital edition, despite having sort of forgotten about it for long enough that starting out again I didn’t quite remember just who everyone was, or what had happened to whom previously. But it’s the kind of book in which you’re enjoying trying to figure out what’s going on anyway, so that hasn’t been a big problem. And the tech and the world and the culture(s) and all are interesting while one is trying to work it all out.

It occurs to me that I could just sort of leave this entry, with the date at the top, open in WordPress all day, and hit Publish in the evening or whenever I felt like I wasn’t going to write anything elsemore to speak of.

Maybe I’ll do that. Although I might forget. And it’s also nice to Publish shortly after writing, and get that sense of Accomplishment.

So for NaNoWriMo this year, assuming I convince myself that I have time, I’m thinking about a nonlinear hyperlinked novel. Say, 100 interlinked pages at 500 words per page? Or 500 100-word pages, or anything on that curve. Something like The Forked Stick, only I would “finish” it in a month, and not leave it hanging forever like I did with that. :)

Water Street runs close by the river, into the Dun Quarter, which is quiet but far from silent in this moony night, breathing with the sharp stillness of the river and the easy aches of poverty and long practice.

To one side is the pier, and across the street is an old building where a sign shows a cup and a hen. Far down at the other end of the street, the Long Temple broods in a feverish silent sleep.

(I am still quite proud of the Tic Tac Toe game embedded in The Forked Stick. Wow, that was some time ago!)

Didn’t you mean to say you assassinate your enemies
Didn’t you mean to say you kill journalists and artists
Didn’t you mean to say you give orders for the murder
Didn’t you mean to say you sell drugs to make your fortune
Holly Near, “Edge”

I don’t actually recall how Edge got onto the iPad here, but I’m enjoying it very much. Energy, novelty.

Also enjoying The Dresden Dolls:

and you can tell
from the smoke at the stake
that the current state is critical
well it is the little things, for instance:
in the time it takes to break it she can make up ten excuses:
please excuse her for the day, its just the way the medication makes her…
girl anachronism

What else should one mention in one’s weblog? I’m sure there are other things that will occur to me later in the day. But at the moment the desire to see it published and In The Can seems sort of strongish. So I will probably push Publish sometime in the next minute or so, assuming the universe and its laws continue more or less unchanged (something that it’s not clear how justified we are in assuming, or whether it matters whether we are).

Yep, here we go!

See you on the other side! :)