JOHN MEANEY

25.9.07


BOOTSTRAPPING THE MODEL

Chicken or egg, which came first?
Where do you check the spelling of a word? Where do you check its meaning? Being transatlantically bilingual, or aspiring to that state, I'll check the OED or Webster's, depending on context. But did you realize that every single English word is defined in terms of other English words?

Well of course you did. As a kid, sensory referents (perceived real objects) became attached to referential indices (words) in your mental model of the world, as you began to learn your first language. Something outside the dictionary kickstarted your language acquisition.
Have you ever tried to make sense of physics as a logical system, without applying intuition to any of its concepts? Honestly, you can't. There's no fundamental axiom from which the other relationships (equations) and concepts are constructed. Distance, time and mass are referential indices to proprioreceptive, kinaesthetic and visual sensations of real-world referents. They're concepts that we learn from outside formal physics; without them, the full richness of our model of the universe cannot come into existence.
If that doesn't translate into specific examples, think of simple relationships like force = mass x acceleration, work = force x distance, power = work/time. Now see if you can derive a meaning for any of the fundamental concepts from the whole collection of equations. Good luck, and you can't!
And yet, even though physics requires the basic concepts to exist a priori, our understanding of force, distance and time are very different now than a hundred years ago, before Einstein twisted our minds.
So while your unconscious mind processes that, here's my recent news. I handed in Dark Blood, the final draft, on time. That was a big rewrite draft, followed by some polishing up. In the last few days of the rewrite, I was working on it 24 hours a day, near enough. At least, every dream seemed to be part of the book.
Of course I took out a little time to exercise. On Sunday Yvonne and I ran a 10K race which was hilly. I was slow, but then again I'd run late on Saturday and very late on Friday, and the cat ate my homework. After the race, my legs gave way (as illustrated).

Now about that chicken. I'm thinking of the usual species, gallus gallus. According to wikipedia, there are several ways of hypnotising chickens. Trained in powerful hypnotherapeutic techniques though I am, entrancing chickens is beyond my experience.

And finally, the answer to the question of which came first. Obviously every chicken grows from an egg, so my answer is -- the first chicken appeared on Earth before the first chicken-egg.

Why do you think that is? And what do you think I mean by 'chicken-egg'?

8 Comments:

Blogger Simon said...

Hello John --

It's a terrific puzzle, and something that (when I'm not working in cosmology, my day job) I ponder.

You can phrase the problem in the language of Bayesian statistics, which we use all the time -- the choice of prior requires intuition. You can of course take a step further back in the chain and use a previous experiment to set the prior, but it can't be "turtles all the way down."

In the end it comes down to the difference between inductive and deductive logic. The question is not as trivial in mathematics, for obvious but interesting reasons.

That said, I have to disagree with your anchoring of physics in the language of "medium sized dry goods" (as the philosophers say.) While it can help you get a handle on things, it's not necessary. In fact, when you get to thinks like general relativity, it can be a positive harm. I think you are in danger of falling into the naturalistic fallacy if you claim too much significance for the experiential.

To a certain extent, progress in physics has been driven by a shearing off of lots of the "basic concepts" and the development of things like the notion of an "event" (in relativity) or a scattering process (in field theory) has been very helpful. The less the proprioceptive sticks its hand in, the better you can grasp what's really going on.

Yours,

Simon DeDeo

PS: very much enjoyed Context. Clever things in there!

September 26, 2007 at 5:24 PM  
Blogger Simon said...

Oh, and a quick note. I found your little capsule history of big bang cosmology and dark energy in Context very amusing! But I would add a correction.

You make the remark that the big conceptual leap was to determine the need for "something" for the universe to "expand into". Actually, to a certain extent the history of the big bang theory has been aided by dumping this notion.

One of the original big bang "models", the Milne Universe, had everything expand into (asymptotically) flat space. i.e., no extra dimensions. The realization that you didn't need this was one of the success of the Friedman cosmology. IMO, and more generally, dumping the "what it expands into" is a success of Occam's razor.

Now that we have all these extra dimensions and braneworlds to play with, we do recover some strange notion of "expanding into". But it's not something people consider a "bonus" at all -- in fact, it's a bit of a joke people tell, as in "finally, string theory does something useful -- it gives an easy answer to our family members who ask what things expand into."

September 26, 2007 at 5:32 PM  
Blogger John said...

Hi Simon! And I'm glad you like Context...

And you're right, as models evolve we successively disengage from the early learnings. I wonder whether it's a case of "neoteny recapitulates phylogeny" (or as the bumper that my brother gave me says: "the first cup of coffee recapitulates phylogeny")because doesn't every one of us begin by experiencing a "force" as something you have to keep applying in order to keep things moving?

I shouldn't have forgotten this, because I produced a software model for handling values in dimensioned units, allowing for primitives (mapping to basic concepts likes mass) and derived dimensions. When I submitted the paper, I made some tongue-in-cheek comment about the model being extensible for new primitive as well as derived dimensions, just in case someone came up with a GUT. My supervisor correctly pointed out that a GUT might well involve removing primitives, not adding them!

I don't know whether you agree, but I suspect that you have to anchor the concepts in real-world perceptions before disengaging them. I remember learning relativity as a first-year student, and being able to spot the ones who didn't read SF, as they said: "Impossible. It can't be like that."

The rest of us had actually read about one twin going off on an interstellar journey and coming back younger than his stay-at-home twin. (Although the name of the Heinlein book has just dropped out of my head... speaking of mental deletion!)

If I remember my philosophical buzzwords correctly, most theories are derived from an operational viewpoint. So even if the separation between events is harder to imagine than the distance between points, we verify the theory by sending clocks on voyages and comparing them with the ones left at home... and experimentally, if time dilation hadn't been seen then the theory would've been wrong.

That said, I glanced at an illustration in The Labyrinth of Time by Lockwood (looks good, haven't read it yet), which shows a 3-4-5 right-angled triangle where the hyptoneneuse is a worldline (of a spaceship) and the vertical axis is time while the horizontal is distance from Earth. And my stomach lurched (kinaesthetic reaction!) as I noticed the hyptoneuse was 3 units long, while it was the time interval that was 5.

Of course, what he really meant was that the time interval was 5i, which rescues Pythagoras... Still, my automatic instincts don't really cope with general relativity. (And that's despite the fact that when I was younger I could swear that I could visualize a hypercube as having four orthogonal dimensions.)

Simon, this is really interesting... And I wonder whether, even though physics has advanced by disengaging from the naturally learned concepts, this strategy is useful in the current, er, context. I mean, maybe it's time to add something back in? Or it could be that string theory has just chosen the wrong assumptions to jettison.

As for mu-space, I confess that came from the fiction more than science. It was a question of "if there's a hyperspace, what would it be like?" and then playing with the thoughts that arose.

So, yes, that was a bit tongue in cheek, that potted history of cosmological theory! In fact I'm a bit mortified that it makes cosmic expansion easier to understand because of a mental picture (of the space outside) that might be fallacious.

The popular science books I read about big bang models when I was younger normally mentioned Doppler shift, and it took me a long time to realize that while it was mathematically the same, the physics was different, since it's not a question of stars moving away but of new vacuum growing in the gap. Which is still a pretty stupendous concept.

So while mu-space is just a fun concept, my thoughts on cosmic expansion and possible contraction were a little more serious. In particular, I'm captivated by the notion of symmetry. That probably goes back to seeing my maths teacher show the tortuous expected solution to an exam question (finding an unknown force in some part of a static bridge-like structure) and then his version, which consisted of one line of maths -- simply writing the result -- plus the proof, consisting of 2 words: 'by symmetry'.

By the way, even as I completely agree with your sentence "The less the proprioceptive sticks its hand in, the better you can grasp what's really going on," I note how kinaesthetic the language is! :)

I love this stuff... and all kudos to you for actually working on the problem of what the universe is really like. Respect!

September 28, 2007 at 8:32 PM  
Blogger Simon said...

Hello John --

Just came across your response! Best to drop me a line "backchannel" at simon[at]kicp.uchicago.edu to follow up to my comment below -- that way I'll be sure to see it.

The "operational" viewpoint -- yes. Just recently I was thinking of a problem and made a lot of progress by stepping back and saying "well, if the needle on the dial does this..." (The problem itself is interesting -- all known equations are second-order in the time derivative, but new theories pop up that are higher order. I'm looking at ways in which a true theory can be second order but appear in approximation as higher order.)

People still argue about what is the "best" way to talk about cosmic expansion (I was looking for an interesting recent pedagogical example I remembered, but couldn't find it -- http://arxiv.org/abs/0704.3579 seems interesting though!) Definitely the "velocity doppler shift" is highly problematic and misleading -- and irritating because if you say this to someone clever but non-physicist, you will probably have left the room by the time she says --

but wait, if v = H*d, what if d is greater than c/H!

and that poor soul will probably wander off into mu prime space, where everything is wrong.

Not sure about kudos! The money's not good but the work is fantastic. Probably the same as being an SF writer!

PS: have you come across something called the Pioneer anomaly? Really interesting stuff there, it's definitely not a kook thing. Could be a fun thing to stick in your next book!

October 6, 2007 at 8:57 PM  
Blogger Simon said...

PPS: cosmic contraction is very interesting. We know form observation that the curvature is very low -- very close to flat. I think this is unassailable at this point.

Now the curvature could be very slightly closed (spherical.) However, we are getting to the point where we know the curvature is closed to almost the level of the matter fluctuations. The former is known to 10^-2, the latter are of amplitude 10^-5.

So it is getting harder to attribute something "deep" to the question of universe recollapse as Stephen Hawking famously suggested in that stuff on the arrow of time. We might just happen to be in a patch where the fluctuations are large enough to turn an open universe closed, or vice versa. At smaller scales, of course we know it happens -- galaxies are formed by chunks of the universe collapsing!

A colleague (Sean Carroll) has some interesting things to say about this age-old problem --

http://arxiv.org/abs/gr-qc/0505037

October 6, 2007 at 9:02 PM  
Anonymous Joao said...

Hello John. I donĀ“t have access to your books, but I could read little parts at amazon.com. What is a "logosophically trained aristocracy"?

Thank you

October 23, 2007 at 11:20 PM  
Blogger John said...

Hey Joao . . .

Excuse the late reply. Thanks for being interested! Are you in Portugal or Brazil, perhaps?

One reviewer (who happens to be a good friend) described the aristocrats' culture as one where "philosophy has become hard science", which is a nice way of describing it. I was thinking of "logos" in the sense of words-reflecting-ideas, along with the overtones of unitary governing principle in the universe.

This means that the aristos are trained in ways that combine rhetoric and neurolinguistic disciplines with physics and art. Some of them are good people, some are bad, and in the books their culture has a blindspot: it allows slavery, as did the ancient Greeks.

To the extent that the books are political satire (which is a small part of what they're about) they do attack aristocratic class structure, something which is known in Britain but less so elsewhere. The members of the upper house in Parliament, the equivalent of the US Senate, are not elected to office. They inherit the roles or are granted them by some process that is invisible to public scrutiny. Still, they do serve as checks and balances, an idea originating with Enlightenment philosophers that seems like a good one.

I find it curious that SF/F books often portray simplified cultures on homogeneous worlds. One of the features of Nulapeiron is that its ten billion subterranean inhabitants speak hundreds of different languages, and no aspect of its culture is truly global.

And one of the books explains the reasons, derived from complexity theory, that the world's founders wanted that diversity, to ensure future viability. It's all part of the way that flexible systems are more robust.

The books are primarily stories, and my US editor described them as "Dune, if Dune had been written by a physicist". Nice of him to say so!

November 18, 2007 at 8:07 PM  
Anonymous chick'n'egg said...

why can't it be turtles all the way round?

the buddhists get the credit for 'beginninglessness'

the world is stranger than sci fi, and since this is sci fi why not allow that every moment we are in is some kind of 'resonance', a superposition if you please, of chickens and eggs. chick'n'egg.

looks like a spinning thing. nothing wrong with circular logic, that's called 'self consistency'. all it needs is the slightest breeze, or quantum noise...

my chick-n-egg joke: "Which came first, the chicken or the egg?"

The rooster!

September 11, 2011 at 2:53 PM  

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