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Comment by pdonis | Hacker News Reader

Unfortunately, this sort of linkbait headline has become typical for Scientific American (which is one of the reasons I haven't subscribed for years). As has already been pointed out in these comments, the Standard Model is already believed to be incomplete by particle physicists, and discovering a new particle in this general energy regime is exactly what everyone has been hoping for for a couple of decades now. Yes, such a new particle is not included in the Standard Model--because there hasn't been any experimental evidence for one. If this discovery pans out, particle physicists will finally be able to start model building again the way it was done when the SM itself was built: based on good experimental data.

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I don't understand what's wrong with the article headline. For years, the theorists were ahead of the experimentalists and were just waiting for the Higgs to be confirmed while they simply speculated about what might be next.

This, for the first time in a long time, would put experimentalists ahead of theorists. That could easily 'crack wide open' a new set of theories to explain the possible particle. Hardly click-bait here, IMO - the content is sufficiently exciting relative to the headline.

> I don't understand what's wrong with the article headline.

"Crack Wide Open" implies, to me, that this discovery somehow shows that particle physics is on a wrong track and needs to drastically change course. (In other comments I've pointed out statements in the article itself that give the same impression.) That's not the case at all. Particle physics has been stalled because of the lack of new experimental data to help theorists extend their models. This discovery, if it pans out, will help particle physics to start up again, exactly as particle physicists have wanted to do for quite some time.

"Crack Wide Open" does not imply that at all. It implies a difficult problem that suddenly yields. When the police officer on the murder drama says this clue will "crack the case wide open", he doesn't mean they've been doing their police work wrong.

> "Crack Wide Open" does not imply that at all.

In isolation, it might not. Taken by itself the phrase is open to multiple interpretations. But in the context of the article as a whole, I think it does.

I agree with jessriedel. I don't think the implication is there.

I also think it's generally bad for discussion to do what you are doing, which is to latch on to a very specific interpretation of a single phrase, and pushing to get everyone else accept that interpretation, instead of taking other comments as additional information about how the words can be interpreted and allowing for those different interpretations to coexist.

Personally, I think that what is bad for discussion is to do what Scientific American did, which is to talk about a scientific discovery in terms that make it seem much more radical than it really is, for no reason that I can see beyond trying to attract readers. The headline is only one aspect of that, as my other comments in this discussion (not just this subthread) should make clear.

Yes, particle physics has been stalled for some time, and suddenly a new piece of evidence is going to supply long awaited traction in creating a better explanation. In other words, it's going to crack wide open.

You've never heard this phrase in the context of, say, a fictional detective talking about an unsolved murder? "I'm about to crack this case wide open!"

Sounds to me like you just never quite understood what people meant by Crack Wide Open. It doesn't mean the theory is going to crack under pressure, forcing us to completely abandon it. It means deeper science, previously stuck inside a 'tough nut to crack', is finally going to be revealed.

EDIT: wow, looks like somebody else had the same exact comment to make. At least it corroborates the point..

> I don't understand what's wrong with the article headline.

The issue to me with clickbait headlines in general is that they have zero information content. Think about how a decent scientific paper is structured - the title gives the broadest possible overview of the content, then the abstract gives a summary of the content, then the paper itself gives the details.

To me, the ridiculously overstated nature of most clickbait headlines is the lesser problem.

Only if theorists can come up with good ideas for what it is.

This is not the first known violation of the standard theory. The standard theory did not predict neutrino mass, and did not predict neutrino oscillation.

"New particle is not included in the Standard Model--because there hasn't been any experimental evidence for one.."

What?! That statement is absurd - reminds me the story of how geocentric model was "adjusted" when new measurements came along. That just leads to overfitting a model. The property of a sound theory is that it can predict future data; it does not just rationalize on data already acquired.

> That just leads to overfitting a model.

My phrasing evidently did not make my point clear. The SM has been known to be an approximation (the usual term is "effective field theory") for several decades; and furthermore, there are well-understood reasons why that particular model is a good approximation up to a certain point. None of that changes if and when we discover experimental evidence of new particles not included in the SM (as we might now have done); in particular, the structure of the SM itself will not change. What changes is that now we have (hopefully) some evidence to help us build the theory at the next level down, the theory to which the SM is an approximation.

That process will not consist of adding parameters to the existing SM (which would be "overfitting"). It will consist of building a new model and then showing how the current SM arises as an approximation in the new model. If we had had this evidence several decades ago, what we now call the "Standard Model" would be that new model instead of the one we currently call the "Standard Model"; we could have jumped to the next level then instead of having to wait.

You didn't really say anything the article didn't say.

I also didn't say some things that the article did say (and which I think are unjustified). For example:

"This could mean nothing less than the fall of the Standard Model of particle physics (SM)"

No, it means that the SM is an approximation to a deeper theory, which everybody already believes anyway and has for several decades. Models don't "fall" just because they turn out to be approximations.

"The SM describes what the building blocks of the universe are and how they work, and from there, at least in principle, explains every other phenomenon in nature."

No, it doesn't. The SM doesn't include gravity. It also has twenty-six free parameters that have to be determined from experiments; it doesn't explain why those parameters take the values they do. So it's obviously incomplete, and everybody has known that for several decades.

(Yes, the article does go on to talk about the SM being incomplete. But that just means it contradicts itself.)

In short: the article talks like this discovery is somehow a huge change in how everybody views the SM. In fact it's business as usual: we built experiments to try to discover new physics to help us extend a model we knew was incomplete, and now those experiments are bearing fruit. This is normal science. It is not some huge rift in particle physics.

Oh, and here's another howler from the article:

"Originally theorists thought that the SM would be an approximation of a more fundamental theory that would be quickly discovered. This is what has always happened in the past."

No, what has always happened in the past is that it's taken a long time for the next more fundamental theory to arise. The article gives Newton's theory of gravity as an example. Newton published the Principia in 1687 (and discovered the key elements of the theory a couple of decades before that). Einstein published General Relativity in 1915. That's not a "quick" discovery of the next more fundamental theory.

As another example, Maxwell's Equations were published in the early 1860s. Quantum electrodynamics, the next more fundamental theory, was published in the late 1940s. Also not a "quick" discovery.

> In short: the article talks like this discovery is somehow a huge change in how everybody views the SM. In fact it's business as usual: we built experiments to try to discover new physics to help us extend a model we knew was incomplete, and now those experiments are bearing fruit. This is normal science. It is not some huge rift in particle physics.

and

>The SM doesn't include gravity. It also has twenty-six free parameters that have to be determined from experiments; it doesn't explain why those parameters take the values they do.

26 free parameters. Yikes.

At what point does the addition of parameters and particles break through from "yet another particle we expected" to "this is completely unexpected and we need to seriously modify our understanding". Obviously with geocentric vs heliocentric it took a major shift in understanding before epicycles crumbled. Same with newton to einstein -- a major shift in understanding before minor errors were explained.

Aside from the SA hyperbole, do you think there is any evidence that particle physics is reaching critical mass in terms of convoluted explanations?

Of course, it could be the case that nature is just damn complex at the particle level.

> At what point does the addition of parameters and particles break through from "yet another particle we expected" to "this is completely unexpected and we need to seriously modify our understanding".

I don't think a shift like this is precipitated by exceeding some limit on free parameters. It's precipitated by a new discovery not fitting with current models. When the Higgs was discovered, it was just a confirmation of what the SM already predicted; it filled in another free parameter in the SM (the Higgs mass, which had only been roughly estimated before), but it didn't point the way to any new, more fundamental model. This new evidence, if it pans out, does point the way to some new, hopefully more fundamental model, because it's something that isn't included in our current models. That is true even if it has no effect at all on the number of free parameters in our theories.

(Btw, the 26 free parameters in the SM sounds like a lot, but since it includes all of the fundamental interactions except gravity, those 26 are really just a collection of all the free parameters from previous theories of those same interactions. For example, the mass and charge of the electron were already free parameters in electrodynamics, so the SM didn't add them on out of nowhere.)

Also, as I've commented already, the SM has been understood to be incomplete for several decades. Everybody already expects that there will have to be a significant shift in our understanding when we go to the next level down. We just don't know what that shift will be, because up to now we've had no experimental data on the question. Now we might finally be getting some.

I am not a theorist, but if anything I think the 26 free parameters is a pretty significant understatement in terms of predictive physics. Experimentalists have measured orders of magnitude more than 26 measurements which are incorporated into our understanding of physics.

The number of free parameters is not the same as the number of experimental measurements; you are correct that there are orders of magnitude more than 26 of those. The point is that the equations of the theory can correctly model all of those experimental measurements only if 26 parameters are included whose values cannot be predicted by the theory; their values can only be obtained by analyzing all of those experimental results and finding the combination of 26 values that best matches the data, given the equations of the theory. It is hoped that a more fundamental theory, to which our current SM would be an approximation, would reduce the number of free parameters required, i.e., would allow the equations of the theory to match all of the data with fewer numbers included whose values the theory cannot predict.

Like you said the SM is an approximation, so even with 26 free parameters there is a lot of physics that is left unexplained. In my experience it seems like far more than 26 free parameters which go into MC simulations, for instance with something like Madgraph. Perturbative QCD predictions also seem to rely heavily on experimental measurements. I'm not sure things like half-lifes can be predicted accurately from 1st principals either. So I don't think it is correct to say that from 26 parameters and first principals we can predict all experimental results. Even if we could do this in theory, in practice we do not have the computational power to do it, so we rely on approximations which are implicitly guided by experimental results.

I agree that the number of parameters needed is less than the number of experimental measurements though, I confused that.

> Even if we could do this in theory, in practice we do not have the computational power to do it, so we rely on approximations which are implicitly guided by experimental results.

This is true, in practice we can't do all of the derivations from first principles. But AFAIK this is an issue of, as you say, computational power; it is not an issue of theoretical insufficiency (at least within the domain that the SM covers, i.e., the non-gravitational interactions in flat spacetime with gravity being negligible). We know what equations we would have to solve; we just can't solve them analytically and we don't have the computing power to solve them numerically in all cases.

Musn't SM be either incomplete or inconsistent, per Gödel's results?

Can SM not represent integers?

> Musn't SM be either incomplete or inconsistent, per Gödel's results?

No. The point of physical models is not to be able to answer all possible questions that you can ask about the models, that as you point out, is not possible.

However, the point of a physical model is to simulate reality. This does not entail being able to answer arbitrary questions (in finite time) about it.

Consider building something like a Nintendo Emulator. As a first pass, you might simply say "I just need to specify the registers and assembly instructions." You might miss out some assembly instructions, and when you pass in a program that uses them, your emulator would crash. You then add that in, and might find out that in order to do faithful reproduction, you need to model instruction execution time and so forth.

In short, your building an emulator requires you to figure out

1) What the state of the Nintendo system needs to be (this may include a time variable).

2) How to correctly handle state transitions.

However, even after you get a complete model of the Nintendo, this obviously doesn't let you answer questions like "If I were to pass in an arbitrary program to my emulator, would it halt on arbitrary inputs?"

Physics is the same. We want to figure out how to specify the "state" of the system, and how that state evolves with time. When we say that a model is incomplete, it means that we're missing some assembler instructions, a register, or something else that doesn't allow us to faithfully simulate reality.

Discovering a new particle is like discovering that there are a bunch of new registers and associated instructions that we need to account for.

(Minor nitpick. Presburger arithmetic can represent integers and is decidable: https://en.wikipedia.org/wiki/Presburger_arithmetic You were probably looking for Peano arithmetic.)

Does that page say Presburger arithmetic requires infinitely many axioms ? How do you make an actual decision when you need to take into account an infinite number of axioms?

What does that even mean?

Gödel showed that any system meeting a certain level of arithmetical complexity will have the property of either being incomplete or inconsistent.

The person I responded to said that SM was incomplete, but that must be the case, unless the model is self-contradictory (assuming it's not, as it would not qualify as a scientific theory if it were), or, the model must not have enough arithmetical complexity to fall under Gödel's rubric.

It's the kind of headline that makes me skim the comments first :)

If you want a good read on this topic that isn't pop-sci crap, (and also not months late) I suggest: https://profmattstrassler.com/2016/03/18/the-diphoton-excess...

Your reply seems to indicate that this is a yawn, but while the article is a bit hyperbolic, it seems to me that experimental evidence of a new, hitherto unforseen particle is about as disruptive of an event one can expect in particle physics, no?

> Your reply seems to indicate that this is a yawn

No, just that it's not the kind of event the article is trying to portray it as.

> it seems to me that experimental evidence of a new, hitherto unforseen particle is about as disruptive of an event one can expect in particle physics, no?

No, it's not disruptive. What has been disruptive has been the several decades without any new experimental results that could help particle physicists to extend their models. Now we might finally be back to the way science is supposed to be done: building theoretical models using experimental data as a guide. This is what particle physicists have been hoping for; it's not a disruption at all.

Uh, isn't a situation where something that has been going on for several decades suddenly changes the very definition of 'disruptive'? :)

> isn't a situation where something that has been going on for several decades suddenly changes the very definition of 'disruptive'?

Not if the sudden change is exactly the one that everyone in the field has been working for and hoping for.

We replaced the baity title with the less baity subtitle.

This is appreciated; unfortunately, we have no way of getting Scientific American to do the same.

Nor anyone else. But at least we can keep sweeping our little corner of the internet.

Note: the headline here on HN is no longer linkbait as the moderators have toned it down. But the Scientific American one still is.

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