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Eliezer_Yudkowsky comments on Open Thread: November 2009 - Less Wrong
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I'll go ahead and predict here that the Higgs boson will not be showing up. As best I can put the reason into words: I don't think the modern field of physics has its act sufficiently together to predict that a hitherto undetected quantum field is responsible for mass. They are welcome to prove me wrong.
(I'll also predict that the LHC will never actually run, but that prediction is (almost entirely) a joke, whereas the first prediction is not.)
Anyone challenging me to bet on the above is welcome to offer odds.
Semi-OT: It's discussions like these that remind me: Whenever physicists remark about how the laws of nature are wonderfully simple, they mean simple to physicists or compared to most computer programs. For most people, just looking at the list of elementary particles is enough to make their heads blow up.
Heck, it nearly does that for me!
Seriously? Dude, it's a list of names. It should no more make your head asplode than the table of the elements does, and nobody thinks that memorising those is a great feat of intellect. Are you sure you're not allowing modesty-signalling to overcome your actual ability?
Now, if you want to get into the math of the actual Lagrangians that describe the interactions, I'll admit that this is a teeny bit difficult. But come on, a list of particles?
"Antimony, arsenic, aluminum, selenium, and hydrogen and oxygen and nitrogen and rhenium..."
I have a metaphorical near-head-explosion for different reasons than the average person that I was referring to. For me, it's mainly a matter of the properties shown on the chart being more abstract and not knowing what observations they would map to (as wedrifid noted in his signaling analysis...).
Compared to the Periodic Table, elementary particle chart also has significantly less order. With the PT, I may not know each atomic mass number, but I know in which direction it increases, and I know the significance of its arrangement into rows and columns. The values in the EPC seem more random.
Granted, but there are also nowhere near as many of them. Besides, fermion mass increases to the right, same as in the PT; charge depends only on the row; and spin is 1/2 for all fermions and 1 for all bosons. This is not very complicated.
I would also suggest that the seeming randomness is a sign you're getting closer to the genuinely fundamental stuff: The order in the periodic table is due to (using loose language) repeated interactions of only a few underlying rules - basically just combinations of up and down quarks, with electrons, and electromagnetic interactions only.
Nu, mass and charge are hardly abstract for someone who has done basic physics; that leaves spin, which just maps to the observation that a beam of electrons in a magnetic field will split into two. (Although admittedly things then get a bit counter-intuitive if you put one of the split beams through a further magnetic field at a different angle, but that's more the usual QM confusion.)
Alright! Point taken! The chart is less daunting than I thought. You mind loosening your grip on my, um, neck? ;-)
An especially good point -- maximally compressed data looks like random noise, so at the fundamental level, there should be no regularity left that allows one entry to tell you something about another.
Oh, a bit off topic, but mind clarifying something for me? My QFT knowledge is very limited at the moment, and I'm certainly not (yet) up to the task of actually trying to really grasp the Standard Model, but...
Is it correct to say that in a sense the force carriers are, in a sense, illusory? That is, the gauge bosons are kind of an illusion in the same sense that the "force of gravity" is? From what little I managed to pick up, the idea is that instead one starts without them, but assigns certain special kinds of symmetries to the configuration space. These local (aka) gauge symmetries allow interference effects that basically amount to the forces of interaction. One can then "rephrase" those effects in a way that more looks like another quantum field interacting with, well, whatever it's interacting with?
ie, can the electromagnetic, strong, and weak forces (as forces) be made to go away and turn into symmetries in configuration space in the same sense that in GR, the force of gravity goes away and all that's left is geometry of spacetime?
Or have I rolled a critical fail with regards to attempting to comprehending the notion of gauge fields/bosons?
Thanks. Again, I know it's a slight tangent, but since the subject of the Standard Model came up anyways...
Ok, I'm not touching the ECE thing; as noted, I'm not a theorist. I just measure stuff. I've taken classes in formal QFT, but I don't use it day-to-day, so it's a weak point for me. However, it seems a bit odd to describe things that can be produced in collisions and (at least in principle) fired at your enemies to kill them by radiation poisoning as 'illusory'. If you bang two electrons together, measuring the cross-section as a function of the center-of-mass energy, you will observe a classic 1/s decline interrupted by equally classic resonance bumps. That is, at certain energies the electrons are much more likely to interact with each other; that's because those are the energies that are just right for producing other particles. Increase the CM energy through 80 GeV or so, and you'll find a Breit-Wigner shape like any other particle; that's the W, and if it weren't so short-lived you could make a beam of them to kill your enemies. (With asymmetric electron energies you can produce a relativistic-speed W and get arbitrarily long lifetimes in the lab frame, but that gets on for being difficult engineering. In fact, just colliding two electrons at these energies is difficult, they're too light; that's why CERN used an electron and a proton in LEP.)
Now, returning to the math, my memory of this is that particles appear as creation and annihilation operators when field theories with particular gauge symmetries are quantized. If you want to call the virtual particles that appear in Feynmann diagrams illusory, I won't necessarily argue with you; they are just a convenient way of expressing a huge path integral. But the math doesn't spring fully-formed from Feynmann's brow; the particular gauge symmetry that is quantised is chosen such that it describes particles or forces already known to exist. (Historically, forces, since the theory ran ahead of the experiments in the sixties - we saw beta decay long before we saw actual W bosons.) If the forces were different, the theorists would have chosen a different gauge symmetry and got out a different set of particles.
I'm not sure if I'm answering your question, here? My basic approach to QFT has always been "shut up and calculate", not because of QM confusion but because I find it very confusing when someone says that a particular mathematical operation is "causing" something. I prefer to think of the causality as flowing from the observations, so that the sequence is thus:
I wasn't bringing up the ECE thing.
I meant illusory in the same sense that "sure, the force of gravity can cause me to fall down and get ouchies... but by a bit of a coordinate change and so on, we can see that there really is no 'force', but instead that it's all just geometry and curvature and such. Gravity is real, but the 'force' of gravity is an illusion. There's a deeper physical principle that gives rise to the effect, and the regular 'force' more or less amounts to summing up all the curvature between here and there."
My understanding was that gauge bosons are similar "we observe this forces/fields/etc... but actually, we don't need to explicitly postulate those fields as existing. Instead, we can simply state that these other fields obey these symmetries, and that produces the same results. Obviously, to figure out which symmetries are the ones that actually are valid, we have to look at how the universe actually behaves"
ie, my understanding is that if you deleted from your mind the knowledge of the electromagnetic and nuclear forces and instead just knew about the quark and lepton fields and the symmetries they obeyed, then the forces of interaction would automatically "pop out". One would then see behaviors that looks like photons, gluons, etc, but the total behavior can be described without explicitly adding them to the theory, but simply taking all the symmetries of the other stuff into account when doing the calculations.
That's what I was asking about. Is this notion correct, or did I manage to critically fail to comprehend something?
And thanks for taking the time to explain this, btw. :) (I'm just trying to figure out if I've got a serious misconception here, and if so, to clear it up)
I guess you can think of it that way, but I don't quite see what it gains you. Ultimately the math is the only description that matters. Whether you think of gravity as being a force or a curvature is just words. When you say "there is no force, falling is caused by the curvature of space-time" you haven't explained either falling or forces, you've substituted different passwords, suitable for a more advanced classroom. The math doesn't explain anything either, but at least it describes accurately. At some point - and in physics you can reach that point surprisingly fast - you're going to have to press Ignore (being careful to avoid Worship, thanks), at least for the time being, and concentrate on description rather than explanation.
Well, my question could be viewed as about the math. ie: "does the math of the standard model have the property that if you removed any explicit mention of electromagnetism, strong force, or weak force and just kept the quark and lepton fields + the math of the symmetries for those, would that be sufficient for it to effectively already contain EM, strong, and weak forces?"
And as far as gravity being force or geometry, uh... there's plenty of math associated with that. I mean, how would one even begin to talk about the meaning of the Einstein field equation without interpreting it in terms of geometry?
Perhaps there is a deeper underlying principle that gives rise to it, but the Einstein field equation is an equation about how matter shapes the geometry of spacetime. There's no way really (that I know of) to reasonably interpret it as a force equation, although one can effectively solve it and eventually get behaviors that Newtonian gravity approximates (at low energies/etc...)
(EDIT: to clarify, I'm trying to figure out how to semivisualize this. ie, with gravity and curvature, I can sorta "see" and get the idea of everything's just moving in geodesics and the behavior of stuff is due to how matter affects the geometry. (though I still can only semi "grasp" what precisely G is. I get the idea of curvature (the R tensor), I get the idea of metric, but the I currently only have a semigrasp on what G actually means. (Although I think I now have a bit of a better notion than I used to). Anyways, loosely similar, am trying to understand if the fundamental forces arise similarly, rather than being "forces", they're more an effect of what sorts of symmetries there are, what bits of configuration space count as equivalent to other bits, etc...)
What is the difference between saying gravity is a force and saying it's a curvature of spacetime?
What is your definition of "a force" that makes it inapplicable to gravity? Is electromagnetism a force, or is it a curvature in the universe's phase space?
I don't know much about physics, please enlighten me...
To say that gravity is a curvature of spacetime means that gravity "falls out of" the geometry of spacetime. To say that gravity is something else (e.g., a force) means that, even after you have a complete description of the geometry of spacetime, you can't yet explain the behavior of gravity.
I followed the link Silas provided. Rather than seeing a list to be memorised my brain started throwing up all sorts of related facts. The pieces of physics I have acquired from various sources over the years reasserted themselves and I tried to piece together just how charm antiquarks fit into things. And try to remember just why it was that if I finally meet my intergalactic hominid pen pal and she tries to shake hands with her left hand I can be sure that shaking would be a cataclysmic-ally bad idea. I seem to recall being able to test symmetry with cobalt or something. But I think it's about time I listened to Feynman again.
Point is, being able to find the list of elementary particles more overwhelming than, say, a list of the world's countries requires a certain amount of knowledge and a desire for a complete intuitive grasp. That's not modesty-signalling in my book.
Everyone knows what a country is. Few people know what the term "elementary particle" means. (It's not a billiard ball.)
It's not a billiard balls from the movie they showed? Then surely 'elementary particles' must refer to those things on the Table of the Elements that was on the wall!
Okay, so I guess I'll be the first person to ask how you've updated your beliefs after today's news.
Physicists have their act together better than I thought. Not sure how much I should update on other scientific fields dissimilar to physics (e.g. "dietary science") or on the state of academia or humanity as a whole. Probably "some but not much" for dietary science, with larger updates for fields more like physics.
Just curious, given that physicists have their act together better than you thought, then, conditioning on that fact and the fact that physicists don't, as a whole, consider MWI to be slam dunk (though, afaik, many at least consider it a reasonable possibility), does that lead to any update re your view that MWI is all that slam dunk?
Nope. That's nailed down way more solidly than anything I know about mere matters of culture and society, so any tension between it and another proposition would move the other, less certain one. It would cause me to update in the direction of believing that more physicists probably see MWI as slam-dunk. :)
Fair enough. (Well, technically both should move at least a little bit , of course, but I know what you mean.)
Hee hee. :)
What exactly is it that you claim to know here? It's not a particular quantitative many-worlds theory that makes predictions, or you wouldn't be asking where the Born probabilities come from. It's not a particular qualitative model of many worlds, or else you wouldn't talk about Robin's mangled worlds in one post, and Barbour's timeless physics in another. What does it boil down to? "I know that quantum mechanics has something to do with parallel worlds"?
Every genius is entitled to some eccentricity, and the MWI is EY's. It might be important to remind the regulars why MWI is not required for rationality, but it is pointless to argue about it with EY.
For all the dilettantes out there who learned about quantum physics from Eliezer's posts and think that they understand it, despite the clear evidence that understanding a serious scientific topic in depth requires years of study, you know where the karma sink is.
No, merely by.
EY's level of support for cryonics (to the point of saying that people who don't sign their children up for cryo are lousy parents) sound waaaay more eccentric to me than acceptance of the MWI.
Is that just because it has human-level consequences?
Belief in MWI doesn't tell you what to do.
No, it's because MWI has broad support among physicists as at least being a very plausible candidate interpretation. Support for cryonics among biologists and neuroscientists is much more limited.
No. Jack apparently read my mind.
Cryonics is a last-ditch long-shot attempt to cheat death, so I can relate quite easily.
-- Woody Allen
I think it comes down to:
(1) The wavefunction is what there is; and
(2) it doesn't collapse.
Well said, this has seemed to be what Eliezer has tried to argue for in his posts. He even went out of his way to avoid putting the "MWI" label on it a lot the time.
That's because physicists, though they clearly enjoy speculating very much, tend to withhold judgment until there is some experimental evidence one way or the other. In that sense they are more instrumentalists than EY. Experimental physicists much more so.
“A physicist answers all questions with ‘I don't know, but I'll find out.’”
-- Nicola Cabibbo (IIRC), as quoted by a professor of mine.
(As for “experimental evidence”, in the past couple of years people have managed to put bigger and bigger systems -- some visible with the naked eye -- into quantum superpositions, which is evidence against objective collapse theories.)
Speaking as someone with an academic background in physics, I don't think the group as a whole as anti-MWI as you seem to imply. It was taught at my university as part of the standard quantum sequence, and many of my professors were many-worlders... What isn't taught and what should be taught is how MWI is in fact the simpler theory, requiring fewer assumptions, and not just an interesting-to-consider alternative interpretation. But yes, as others have mentioned physicists as a whole are waiting until we have the technology to test which theory is correct. We're a very empirical bunch.
I don't think I was implying physicists to be anti-MWI, but merely not as a whole considering it to be slam dunk already settled.
Interesting. What technology lets you test that?
We have discussed it here. A reading list is here.
I notice that in your prediction you welcomed bets, but you did not offer odds, nor gave a confidence interval. I’m not sure (haven’t actually checked), but I have an impression that you usually do at least give a number.
Since the prediction was in 2009 it might just be that you recently formed the habit. If that’s not the case, not giving odds (even when welcoming offers) might be an indicator that you don’t believe something as much as you think you do. (The last two "you" are meant both as generic people references and to you in particular.) Does that seem plausible on a quick introspection?
I did make a bet and pay it.
Yes, I know. But those were even odds. When someone makes a prediction unprompted, it suggests more confidence than that. (Well, unless they’re just testing what odds other people offer, but I don’t think that was the case here.) That is, it is possible that your inner censor for “don’t predict things that might prove wrong” didn’t trigger (maybe because you’ve trained yourself to ignore embarrassment about people’s opinion of you), but the censor for “don’t bet when you might be wrong” triggered without you noticing it.
In other words, it might be an indication of a difference between what you believe and what you think you believe, or even what you want to appear to believe :-)
(It might also be that you actualy thought the odds were 50:50, and anticipated others to offer much higher odds. How likely did you think it was at the time, anyway?)
You seem to be conceding that this is in fact the Higgs boson. In fairness I have to point out that, although it is now very certain that there is a particle at 125 GeV, it may not be the predicted Higgs boson. With this in mind, would you like to keep our bet running a while longer while CERN nails down the properties? Or do you prefer to update all at once, and pay me the 25 dollars?
I'd rather pay the $25 now. (Paypal data?) My understanding is that besides the mass, there's also supposed to be other characteristics of the particle data that match the predicted Higgs, otherwise I would've waited before fully updating. If the story is retracted I might counter-update and ask for the money back, but my understanding is that this is not supposed to happen.
What other features (apart from being a particle at 125 GeV) do you consider a necessary part of the specification "Higgs Boson" for the purpose of this bet?
I will take up the bet on the Higgs field, with a couple of caveats:
You use the phrase "the Higgs boson", when several theories predict more than one. If more than one are found, I want that to count as a win for me.
If the LHC doesn't run, the bet is off.
Time limit: I suggest that if observation of the Higgs does not appear in the 2014 edition of "Review of Particle Physics", I've lost. "Observation" should be a five-sigma signal, as is standard, either in one channel or smaller observations in several channels.
25 dollars, even odds.
As a side note, this is more of a hedge position than a belief in the Higgs: I'm a particle physicist, and if we don't find the Higgs that will be very interesting and well worth the trivial pain of 25 dollars and even the not-so-trivial pain of losing a public bet. (I'm not a theorist, so strictly speaking it's not my theory on the chopping block.) While if we do find it, I will (assuming Eliezer takes up this offer) have the consolation of having demonstrated the superior understanding and status of my field against outsiders. (It's one thing for me to say "Death to theorists" and laugh at their heads-in-the-clouds attitude and incomprehensible math. It's quite another for one who has not done the apprenticeship to do so.) And 25 dollars, of course.
Update: a 5-sigma signal for a new boson has showed up.
I've added this bet to PredictionBook at http://predictionbook.com/predictions/1566 based on http://wiki.lesswrong.com/wiki/Bets_registry
I've just learned that Stephen Hawking has bet against the Higgs showing up.
Here's my argument against Higgs boson(s) showing up:
The Higgs boson was just the first good idea we had about how to generate mass. Theory does not say anything about how massive the Higgs itself it is, just that there is an upper bound. The years have passed, it hasn't shown up, and the LHC will finally take us into the last remaining region of parameter space. So Higgs believers say "hallelujah, the Higgs will finally show up". But a Higgs skeptic just says this is the end of the line. It's just one idea, it hasn't been confirmed so far, why would we expect it to be confirmed at the last possible chance?
Two years ago:
I wrote to him at the time expressing interest in the bet, but asking for more details. (No reply.) The rather bold statement that QM itself implies a Higgs "or something like it" I think must be a reference to the breakdown in unitarity of the Standard Model that should occur at 1 TeV - which implies that the Standard Model is incomplete, so something will show up. But does it have to be a new scalar boson? There are Higgsless models of mass generation in string theory.
This all leads me to think anew about what's going to happen. The LHC will collide protons and detectors will pick up some of the shrapnel. I think no-one expects new types of particle to be detected directly. They are expected to be heavy and to decay quickly into known particles; the evidence of their existence will be in the shrapnel.
The Standard Model makes predictions about the distribution of shrapnel, but breaks down at 1 TeV. So one may predict that what will be observed is a deviation in shrapnel distributions from SM predictions and that is all. Can we infer from this, and from the existing range of physics models, what the likely developments in theory are going to be, even before the experiment is performed?
Although I said that totally new particles will not be observed directly, my understanding is that the next best thing is certainly possible, namely a very sharp and unanticipated change in the distribution of decay products at a specific energy. That would mean that you had a new particle at that energy.
The alternative would seem to be a sort of gentle deviation of decay statistics away from SM predictions. Unfortunately I don't know enough about the theoretical options to really predict how this might be interpreted. However, the Higgsless models involve extra dimensions. So if we have the dull outcome, it will probably be interpreted by some as our first evidence of extra dimensions.
Also, particle physics is very complex and there are many possible mechanisms of interaction. I think that, if no Higgs shows up, many theorists will go back to their theorems and question the assumptions which tell us that this is the last chance for a Higgs to show up.
My prediction, then, is that if we get the dull outcome - no unambiguous signal of a new particle - we will see both even more interest in extra dimensions, and a new generation of "heavy Higgs" models which explain why we can, after all, have a heavier-than-1-TeV Higgs without screwing up observed low-energy physics.
I was hoping to make some more money on this :) in a shorter time and hence greater implied interest rate :) but sure, it's a bet.
Sorry, graduate students can't afford to be flinging around the big bucks. :) If I get the postdoc I'm hoping for, we can up the stakes, if you like.
This is a side issue but I'm curious as to what people's reactions are: I'm kind-of hoping that dark matter turns out to be massive neutrinos. Of the various candidates, it seems like the most familiar and comforting. We've even seen neutrinos interact in particle detectors, which is way more than you can say for most of the other alternatives... Compared to axions or supersymmetric particles, or WIMPs, massive neutrinos have have more of the comfort of home. Anyone feel similarly?
As I understand it, there is a known upper bound on neutrino mass that is large enough to allow them to account for some of the dark matter, but too small to allow them to account for all or most of it.
That is correct as far as the known neutrinos go. If there is a fourth generation of matter, however, all bets are off. (I'm too lazy to look up the limits on that search at the moment.) On the other hand, since neutrinos oscillate and the sun flux is one-third what we expect rather than one-fourth, you need some mechanism to explain why this fourth generation doesn't show up in the oscillations. A large mass is probably helpful for that, though, if I remember correctly.
Point of order! A massive neutrino is a WIMP. "Weakly Interacting" - that's neutrino to you - "Massive Particle".
Well, but “massive” in WIMP usually means very massive (i.e. non-relativistic at T = 2.7 K). As far as gravitational effects, particles with non-zero mass but ultrarelativistic speeds behave very much like photons AFAIK.
Thanks, point taken - I'd been thinking of more exotic WIMPs
I guess hardly anybody here knows even what the question means, exactly, so all a bead jar guess.
Intrade has market for Higgs boson.
Too thinly traded, deadline too soon, rules for what counts as "confirmation" too narrow given the deadline.
The market, unfortunately, is only through the end of next year; does anybody know whether all the relevant experiments are slated to be performed by then?
I'd like to unwind P(Find Higgs|LHC runs and does the tests) down to just P(Find Higgs) or some approximation thereof.
There are markets for further years, but have almost no activity, so I didn't link to them.
Well, the Standard Model hasn't been wrong yet. If you want to bet against it, I'll take you up on it.
I assert that the LHC will not establish the non-existence of the Higgs boson. Will you wager $20 at even odds on against that proposition?
I'll bet that the LHC will not establish existence. It's not clear to me what would count as establishing non-existence.
There are papers that establish upper bounds on the energy of the higgs boson,
http://arxiv.org/abs/hep-ph/9212305
If the LHC can make particles up to those energy bounds (I don't know and don't have the time to figure it out), and it can be run for sufficient time to make it very unlikely that one wouldn't be created. Then you could establish probable non-existence.