This is interesting - normally AMP is great and I'm (generally) a fan of it. But somehow they messed up AMP here - I've not seen that before. The AMP page is really poor (third party blocking, time to paint, even JANK is here - shift after load).
The non AMP page is 1.4MB and 45 requests, the AMP page is 400KB and 16 requests - normally this means AMP just blows everything out of the water (despite HN hate). Something is messed up here that AMP is so poor, initial server response is terrible.
Jeebus, another frustrating air-filled article to up the word count.
Meat:
> The LHCb produces sub-atomic particles called "beauty quarks", which are not usually found in nature but are produced at the LHC. Sub-atomic particles undergo a process known as decay, where one particle transforms into several, less massive ones.
According to the Standard Model, beauty quarks should decay into equal numbers of electron and muon particles. Instead, the process yields more electrons than muons.
One possible explanation is that an as-yet undiscovered particle known as a leptoquark was involved in the decay process and made it easier to produce electrons.
Looks like some people didn't like you putting the concept in more accessible terms. "Three sigma" has a real interpretation, it's not just a little score where you pull out LaTeX when it reaches 6.
Of course, to perform any valid statistical reasoning, you need to consider the prior. The standard model has held up very well, and we do a lot of experiments-- any of which has a small chance of popping out a result that looks highly significant by chance. There's a reason why 6 sigma is the line to take things super seriously (in fundamental physics).
You are joking, right? The experiments around the LHC have produced a handful of three-sigma "non-standard-model" results already. So far they have all gone away.
This is not a bad thing, by the way - just an inevitable consequence of doing many searches.
Yes but he brings up a good point. They are more likely to talk about a 3 sigma result that challenges the standard model than one that doesn’t yield anything special. So given you know a 3 sigma result is being discussed, the probability that it’s a false result at higher sigma is more than 1/1000.
The result was past three sigma, not exactly at three sigma. But good point, because if it was exactly at three sigma I would have snookered myself. :)
The model indicates 1000:1, but it may not capture all aspects (i.e. correlations) in the system. So what seems like excessive sigmas is also margin for those unknown-unknowns.
Plenty of 3 sigma results have come and gone, (there's obviously an xkcd for this about doing a whole lot of experiments). It's certainly something to watch and I would personally be stoked for some new physics.
I only posted because it was the first thing I wanted to know, and I had to dig around in the article for a bit before I found it at the end.
My mentor once said "3 sigma effects happen in physics a lot more often than they should." I've since come to realize that we should do a multiple-hypothesis testing correction on all such results, where the number of hypotheses tested is approximately equal to the number of Ph.D.s granted in particle physics.
As someone with a background in Physics I get a very strong Gell-Man Amnesia vibe any time Physics is discussed on HN. The takes are nearly always bad and generally not even wrong, it makes me seriously question all discussion on HN.
> which ultimately could allow us to unravel any number of established mysteries. These include the nature of the invisible dark matter that fills the universe, or the nature of the Higgs boson. It could even help theorists unify the fundamental particles and forces...
To this non-physicist, it's not clear at all how this potential discovery might do any of that. From here, it looks like a mininally consequential addendum to the standard model, almost like a single epicycle to a geocentric cosmology. The effect only shifts by a few percent the chance of some obscure and rare interaction. Is it really plausible that it could have such grand implications?
The problem in modern physics is that the epicycles work too well. There are some big obvious mysteries and an incredibly-successful epicycle-based theory. Essentially everyone expects that the epicycles are not the truly fundamental theory of things.
So, physicists keep comparing the predictions of the "epicycle-theory" with reality in new ways, ways where a deviation from the prediction would be an unambiguous signpost pointing a direction toward which one might be able to address a big mystery. As those tests become established, they are then performed with higher and higher precision.
The signal potentially seen with LHCb is, if it persists, important. In a nutshell, electrons are, in this particular way, predicted to act exactly like muons. No ifs, ands, or buts. What they see is that electrons and muons might be acting slightly differently. If so, some new physics (or a major error in our understanding of the epicycles -- I'm looking at you, loops) must be at work. If this result persists, it is guaranteed that we will learn something.
Too convoluted? Here is a different analogy:
You're pretty sure someone is embezzling from your company.
You look at your bank account, and you have ~95% less money than you thought you should. Really. Oh, no.
You check the summary budgets, they're balanced. So you do this for all the company's divisions. Yep. Still balanced. You get paranoid. You do this for decades -- the books balance, but at the end of the day? 5%.
Then an employee runs up to you and says, "Shmageggy! We're not sure yet, but it looks like one of our most-trusted partners, whom the firm has worked with since 1936, transferred thirty-seven cents to an account in the Cayman Islands!"
Until we find the embezzler, that's what every one of these precision physics tests that makes the news is all about.
Thanks for the well thought out reply. So IIUC it's (probably) not that this result is the One True Answer in itself, but rather a potential chink in the armor that tells us where to pry.
There are well-known places where we think the armor might be weak and we're trying all of them roughly equally. The moment someone finds an actual hole in the armor, a lot of people will jump in and hammer on that one in particular.
The key properties of the weak points are:
a) We have to be able to hit it there in a meaningful way
b) Anywhere that we expend millions of dollars and oodles of people-years of work to look for holes, we have to be capable of verifying that a possible-hole is an actual-hole.
This particular anomaly scores pretty well on b). If they have a clean signal there, then it is a pretty big deal.
The implication is that there is something beyond the Standard Model which has been essentially completely bulletproof for the last 50 years. Nothing outside truly unknown phenomena, dark matter, dark energy, etc. has ever invalidated it. We know theoretically there has to be more physics but have had no experimental inkling that was really the case.
The paper mentions leptoquarks (particles that interact with leptons and quarks with potentially different coupling strengths for different leptons therefore breaking lepton universality) or some unknown heavy (didn't look into it any further but I guess the heavy requirement is there because otherwise we would already have observed its effects, I don't think it's necessary for this particular observation) neutral boson that would for example allow flavor changing of leptons ("flavor" means whether it is an electron, muon our tau lepton).
The current standard model is slowly getting messier and messier. At some point we will make a discovery that adds some degree of elegance into our understanding of these interactions.
This really grinds my gears, we purposefully moved away from "beauty quark" as it was a bit too whimsical (at the expense of descriptiveness), now science communicators keep using it as it seems to capture the imagination of non-sci readers. So please, as an informed individual, replace "beauty quark" with "bottom quark" every time you see it in this piece.
I'm a physicist who spent seven years working at the LHC and I've never heard of a "purposeful" move away from the term beauty quark. It just fell out of favor but some, including myself, still like to use that name on occasion, personally I like it much better.
The particle does not have a name in the official (PDG) listing, only a symbol "b". The "bottom" quantum number is universally called as such so one talks of "bottom hadrons" and so on. On the other hand the general area of research is called "b-physics" or "beauty physics", LHCb is the LHC-beauty experiment and so on. It makes perfect sense that this article uses "beauty" throughout for consistency.
At the end of the day its just a name and this particle happens to have more than one (as does the J/psi and others) and neither is more whimsical than the other. Physicists tend to be quite whimsical anyway, particle physicists perhaps especially so.
I was given the impression by my professors that it was a purposeful move, maybe it was just in teaching and not research. I'll defer to you, the actual particle physicist.
I’d also heard something like this during my physics education - you’re not alone apparently. One name was apparently more ‘respectable’ than the other. Lol
heh there's a deep irony here, in a story about "how science communicators [supposedly] ditched the term favoured for capturing the public imagination, in order to instead favour a more descriptive factual term"...
...of which the story itself is an overly neat simplification that has spread by better capturing the imagination of descriptive-minded physics students, in the teachers' own science communicating :)
Make no mistake, I think they should teach the b-quark as "bottom quark" to the general public and students. What particle physicist actually choose to use should be done at their own whimsy. I appreciate your diagnosis though, always feel I could be a bit more introspective.
I kind of don't believe there is such a thing as "just a name". People persistently confuse names with the thing named. If you want to communicate truthfully, you have to take into account the psychology of your audience. So "it's just a name" is not a good reason for misleading names.
I realize this isn't a big deal for quarks, but it's been on my mind a lot. The application to politics is left as an exercise for the reader.
What do you do now? Is there a demand for CS skills at the LHC, and was it a fulfilling place to work in general? Presumably you lived in the UK that whole time?
The LHC is in Switzerland (not the UK) and in fact I'm still here. I was a data scientist for while. These days I'm back in research, but in a different field.
There is a huge demand for CS skills of all kinds. CERN has one of the largest SCADA installations in the world, runs its own internet exchange point, operates a network of computing centers with a million cpu and hundreds of PB of data, and maintains many many millions of lines of code of specialized software, just to give you an idea.
It is a fantastic place to work, the level of expertise and dedication among the people there (scientists and engineers alike) is very very high.
They have also shown an impressive 1000-machine kubernetes cluster running on GCP for analyzing data (they did a live demo at KubeCon in 2018 I believe where they ran the Higgs boson data analysis during a panel).
In any case, which authority told /u/reedf1 that studying the universe should be barred from being whimsical? Alan Watts would be laughing. So would the Joker. The universe is not meant to be taken so seriously. It is whimsical. And that is part of its beauty ;-)
I have absolutely no problem with it being whimsical.
Actually I would like it to be as whimsical as possible, while still being easy and consistent to learn that is.
The official name of the LHCb experiment is the "Large Hadron Collider beauty" experiment, as named by the scientists themselves. So "beauty quark" is more correct in this context.
I would actually say that beauty is more scientifically clear.
The various quantum numbers of the quarks are real physical quantities, but not ones for which we have a good way of conceptualizing in classical, macroscopic life. The up and down quarks aren't actually spinning, but they do kind of behave as if they were spinning, so their names make sense, but for the others there isn't even an analogue. Luckily no one expects to be able to visualize strangeness, and likewise charm and beauty convey quite well that the naming is arbitrary. Top and bottom on the other hand sound like they could refer to a "real" property, or perhaps represent two ends of a spectrum. While I've seen no evidence that confusion is rampant, it would be easy to see how confusion could arise. If anything, the Top quark should be renamed to something more whimsical, or both should be renamed to something more clearly arbitrary like heads and tails.
I'd guess this is a dig at biology's naming tradition, for the purpose of showing that scientists as a whole aren't great at naming either. Or maybe people in general -- check out the wikipedia page for Mohammadabad: looks like there are hundreds of places with that name in Iran
Svante Pääbo's human genetics lab (who discovered Denisovans and sequenced the first Neanderthals) has a policy of not using Latin names for anything, because he thinks they're pretentious but also they don't think any of their discoveries are different species.
On the other hand, everyone else who discovers a hominin still gives it a new species name.
Well because you can encode intuition in names. e.g. Quarks come in pairs, and each pair has one quark with +2/3e charge and one with -1/3e. The names can give you intuition for their charge, i.e. Up quark is +2/3e Down quark is -1/3e. And if you give names that give you intuition for the charge it is considerably easier to remember (as a former undergrad physicist trust me you need assistance here). The name name "top" allows you to immediately think "up" and +2/3e and "bottom" allows you to immediately think "down" and -1/3e.
What you are describing is association, not intuition. It is not the responsibility of scientific laborers to name and structure things in order to create convenient associations for cramming physics undergrads. Intuition involves a deep understanding of the objects and processes, a lot more harrowing than memorizing charges..
What is intuitive about the up quark and down quark charges?
The fact that "up" is associated with positivity is totally arbitrary, and even the fact that positive charges are called positive is totally arbitrary.
Maybe because it misleads people into an inaccurate anthropomorphic impression of what these cute little nippers are up to, undermining this-is-serious science. See also: Sea Monkeys.
Yes, "Truth quark". Because they don't exist naturally it lead my physics prof to say "There is no truth in the universe".
Also, Some physicists call the fourth, fifth, and sixth derivative of position, "snap, crackle, and pop" respectively. Physicists are a fun lot aren't they?
Not just quadrotor motion control, it applies to precision machinery as well. Eg. it's used in those big ASML wafer stepper machines that help power Moores Law for example, but also 3D printers etc. Low values for these derivatives help reduce vibrations in the machines IIRC.
Snap is that feeling you get when a train is braking and comes to a halt. The breaking force suddenly falls of, which is noticeable.
In general, snap shows how smoothly the acceleration occurs. This allows anything that flexes (like flesh) to slowly take-up the slack.
I've also heard this is important for self-driving convoys. You want the cars in the convoy to all accelerate and brake smoothly rather than jostle all the things inside them.
'Strange' predates the quark/parton model, and was a placeholder name for a particular unexplained phenomenon; similar to how the prefix 'dark' gets used.
In particular, collider experiments were giving rise to a 'particle zoo' of pions, kaons, lambdas, etc. all of which were assumed to be fundamental. Some of these lasted much longer than expected, and were called "strange".
It turned out that these could be modelled by giving fundamental particles a new property, which got the name "strangeness". Similar to how particles can have "charge", which is zero for neutral particles; non-strange particles have zero strangeness. Their long lifetime was explained due to the strong force conserving strangeness: collisions between non-strange particles can make pairs of particles with positive/negative strangeness (as long as it sums to zero); but once those individual particles have separated they can no longer decay via the strong force; they have to wait for the weak force, which gives them a longer half-life.
It was only later, once the quark model became more accepted, that these particles were no longer considered fundamental, and "strangeness" could be explained as "containing strange quarks".
On the other hand charm, beauty/bottom and truth/top seem to all be built on the quark model from the start; which makes the whimsy in their names more deliberate.
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FYI the BBC's Horizon did an episode in the 60s called "Strangeness Minus Three" ( https://www.bbc.co.uk/programmes/p01z4p1j ) which is interesting to watch in hindsight, now that we have quarks and the standard model; and makes a nice comparison to the more recent search for the Higgs boson.
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Tangentially this idea, of a new property whose conservation prevents massive particles from decaying, also arises in supersymmetric models of dark matter. There, supersymmetric particles have a different "R parity" to normal particles, which prevents them decaying even if they're very massive; such particles are a candidate for dark matter.
The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance that the measurement is a statistical coincidence.
No, that’s not what this means. But this is about one in 1,000 BBC Science articles that have repeated this confusion.
Edited to add:
What this actually means is that, conditional on the null hypothesis (that there is nothing there to find), there is a one out of 1,000 chance of seeing an observation such as this by chance.
But the BBC article has inverted this. Rather than giving you the probability of the data given the hypothesis, they're purporting to give you the probability of the hypothesis given the data (which in general cannot be objectively stated; this is a standard difficulty in the philosophy of science and statistics): "there is roughly a one in 1,000 chance that the measurement is a statistical coincidence [i.e. the null hypothesis is true and there's nothing to see here]". They make it sound like the scientists are virtually certain that they've found something here, when in reality this is probably nothing (although that's a matter of opinion).
I believe you that isn't what it means, but for those (like myself) who have limited familiarity with this topic, could you please explain what it actually means.
I’m thinking it would be more accurate (by being less precise) for BBC to describe the 1:1000 possibility as just coincidence rather than “statistical” coincidence.
This article seems to agree that 3 sigma simply means "1 in 1000 possibility the result is a coincidence". I'm not sure what difference removing the word "statistical" makes here or why the BBC explanation is wrong.
> Chances are, you heard this month about the discovery of a tiny fundamental physics particle that may be the long-sought Higgs boson. The phrase five-sigma was tossed about by scientists to describe the strength of the discovery. So, what does five-sigma mean?
> In short, five-sigma corresponds to a p-value, or probability, of 3x10-7, or about 1 in 3.5 million. This is not the probability that the Higgs boson does or doesn't exist; rather, it is the probability that if the particle does not exist, the data that CERN scientists collected in Geneva, Switzerland, would be at least as extreme as what they observed. "The reason that it's so annoying is that people want to hear declarative statements, like 'The probability that there's a Higgs is 99.9 percent,' but the real statement has an 'if' in there. There's a conditional. There's no way to remove the conditional," says Kyle Cranmer, a physicist at New York University and member of the ATLAS team, one of the two groups that announced the new particle results in Geneva on July 4.
Thanks - I think that does explain some of the potential area of confusion. However, I don't agree that the BBC's explanation differs from what the true meaning is according to this Scientific American article says.
The BBC article says:
> The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance that the measurement is a statistical coincidence
My interpretation of this is "If there was no new physics, then there is a 1/1000 chance the same result could be measured by coincidence."
I understand why some people may interpret this as "There is a 1/1000 chance that there is no new physics" though.
>"There is a one in 1,000 chance that the measurement is a statistical coincidence", grammatically, presumes the measurement which did in fact occur and says something about the chance that a statistical coincidence did, in fact, happen. It's P(hypothesis | data). This is a classic no-no in science writing.
>"There is a one in 1,000 chance that the measurement would arise by statistical coincidence" uses the subjunctive, (implicitly) presuming a hypothesis and saying something about the chance that, under that hypothesis, such a measurement as occurred would occur. It's P(data | hypothesis).
I now see your criticism and I agree the subjunctive is much clearer. I guess my brain just converts the other wording into yours whenever I read text like that.
Your point still stands, but technically that's not the subjunctive, it's the conditional.
Actual subjunctives are only rarely used in English and often sound clunky. If you did use it it would be "There is a one in a 1,000 chance that the measurement arise by statistical coincidence". Note that it must be "arise", not "arises".
Again, both of those examples you have given are the conditional, not the subjunctive. If the clause uses "would" with its main verb, it's not the subjunctive mood.
Also note that I'm specifically referring to the plain subjunctive. There is also something sometimes referred to as the "past/imperfect subjunctive" which is something different entirely.
I think "subjunctive" is used loosely. I think that I'm right in terms of descriptive diction; anything irrealis and non-imperative is often (typically?) called subjunctive in English, since we only use distinct verbs for indicative, imperative, and subjunctive moods.
I think, however, that I prefer your rigorous distinctions. Moods seem to be important to human language, even if they're atrophied in English. So keeping the gate on the subjunctive vs conditional distinction points people toward a deeper understanding of how language works.
My brain does too, but I fear the average layperson won't know to do this and will come away from the article thinking there's been a real discovery here.
"There is a one in 1,000 chance that the measurement is a statistical coincidence", grammatically, presumes the measurement which did in fact occur and says something about the chance that a statistical coincidence did, in fact, happen. It's P(hypothesis | data). This is a classic no-no in science writing.
"There is a one in 1,000 chance that the measurement would arise by statistical coincidence" uses the conditional, (implicitly) presuming a hypothesis and saying something about the chance that, under that hypothesis, such a measurement as occurred would occur. It's P(data | hypothesis).
I agree, I understand the difference between the conditionals, but was trying to get what the OP was criticising. I think this is much more a interpretation of language issue than a correct/incorrect in the formal sense issue.
Yeah, I’m not exactly getting why BBC is wrong either.
Re “statistical”, to me, it sort of implies all sources of error or variability were provably not present (prove a negative) and the only reason for a coincidental result was a statistical anomaly. What’s got to be far more likely is some unaccounted-for variable produced the coincidental result.
The probability of winning the lottery if you're a cheater is high, but the probability of being a cheater if you win the lottery is low. More generally, the probability of A conditional on B is not the same as the probability of B conditional on A. Sometimes they're similar, but it depends on the pre-existing odds of A and B.
The p-value of a physics experiment isn't the probability of the result coming from thin air but rather than the probability of a result as or more extreme under the assumption of the null hypothesis (i.e. the effect we are looking for doesn't exist). The rub is that the design of the experiment and thus the hypothesis test is all dependent on various subjective factors, especially the people designing the experiment themselves.
I'm not statistician however so presumably I'm just as wrong
In case it helps, following that logic, green jelly beans could cause acne and there would be "roughly a 5% chance that the measurement is a statistical coincidence": https://xkcd.com/882/
I don't see how the BBC's statement can translate into P(hypothesis|data). To me it's P(data|H0).
Consider this simpler example: "Scientists always assumed their coin was fair. Well, they flipped it 10 times, and it came up heads every time. This is a 3-sigmal result. There's a 1 in 1024 chance of this measurement being a statistical coincidence."
The reader would take this "1 in 1024 chance of coincidence" to mean "if the coin was fair, they'd have a 1 in 1024 chance of seeing this event occur". That's P(data|fair) = P(10 heads|fair) = 1/1024.
I don't see how you read that and translate it into P(fair|10 heads).
If I say: "there's a 25% chance that Pat is from North Dakota", I'm taking as a given that there is a person named Pat, and I'm talking about the chance that Pat, whom we know to exist, is from North Dakota.
In this case, grammatically, they're talking about the chance that the measurement (data) is a statistical coincidence, as opposed to not being a statistical coincidence. They're not talking about the chance that the data exists, as opposed to not existing.
> If I say: "there's a 25% chance that Pat is from North Dakota", I'm taking as a given that there is a person named Pat, and I'm talking about the chance that Pat, whom we know to exist, is from North Dakota.
Yes, and if I say "there's a 0.001% chance that these coin flip observations were coincidental", I'm taking it as a given that there were coin flips observed (indeed, there were!) I'm talking about the chance that the observations, which we (indeed) know to exist, were coincidental.
> In this case, grammatically, they're talking about the chance that the measurement (data) is a statistical coincidence, as opposed to not being a statistical coincidence. They're not talking about the chance that the data exists, as opposed to not existing.
Which is... perfectly fine. The data clearly does exist (as would the coin flips in my example), so the chance of the data existing is 100%... there's nothing interesting to talk about there. But the chance of it having been coincidental is 0.001%.
There's been a misunderstanding between us. To clarify, I'm not saying we know some data exists (that's of course true, since an experiment was done). I'm saying we know this data exists. Grammatically, they've worded it so that the question is whether this particular data that we have seen (as opposed to other data we could have seen) was in fact produced by chance or not.
The difference between the data being a statistical coincidence and the data not being a statistical coincidence is precisely the difference between the null hypothesis being true and the null hypothesis not being true. So they're making a claim about the probability of a hypothesis.
> There's been a misunderstanding between us. To clarify, I'm not saying we know some data exists (that's of course true, since an experiment was done). I'm saying we know this data exists.
But that's exactly what I'm saying too? When I flip 10 coins and see 10 heads, that is the data, and it very much exists. Nobody is talking about any data except that one. Not me, not you, not BBC.
> Grammatically, they've worded it so that the question is whether this particular data that we have seen (as opposed to other data we could have seen) was in fact produced by chance or not.
Yes, and as I see it this is 100% correct. Like in my example where I saw 10 heads (that is the one and only dataset we know exists), and I'm wondering if they were produced by chance or not. That is precisely P(10 heads | fair coin) = P(observations | H0).
> The difference between the data being a statistical coincidence and the data not being a statistical coincidence is precisely the difference between the null hypothesis being true and the null hypothesis not being true.
Maybe your English analogy is the source of the confusion here? I don't know what rigorous definition you might have for "the difference" here(?), but whatever it is, "10 heads have a 0.001% chance with a fair coin" doesn't imply "10 heads have a 99.999% chance under an unfair coin"... right? Even though the former assumes H0 and the latter assumes !H0.
Or to put it another way, just because H0 is true in one statement and false in another, that doesn't mean we're talking about the probability of H0 being true in one statement and the probability of H0 being false in another.
The original wording is: "there is roughly a one in 1,000 chance that the measurement is a statistical coincidence".
By definition, "the measurement is a statistical coincidence" means the same thing as "the null hypothesis is true". That's literally just how we define "statistical coincidence".
So the sentence might as well be worded: "there is roughly a one in 1,000 chance that the null hypothesis is true".
> By definition, "the measurement is a statistical coincidence" means the same thing as "the null hypothesis is true".
OK, now I see what you're saying. I'm not sure that's how people interpret it in plain English though. I feel like people would interpret "is a coincidence" to mean "occurred coincidentally", aka "occurred naturally [by chance]". It might be kind of like arguing that "ladies and gentlemen" refers to their intersection rather than union. Mathematically it does, but English is another matter...
Maybe the only way to settle this is to actually go do an experiment on people. I could be wrong, but I feel like if you go up to people and say "I think these 2 dice are fair, and I got two 6's when I tossed them; what are the chances this is a coincidence?" you'd get back "1/36" from most people. (Assuming they remember basic probability at all. You can filter against that by first asking them something more obvious, like maybe "what are the chances of getting 2 heads in a row with a fair coin" and making sure they tell you 1/4 before you proceed.)
I consider “occurred coincidentally”, “is a coincidence”, and “occurred by chance” interchangeable. They are all equivalent to the null hypothesis.
If my dice are loaded then the two 6’s weren’t a coincidence. They were guaranteed. So to say they happened by coincidence is to say the dice are fair (the null hypothesis is true).
Consider a typical English sentence: “was it just a coincidence that I saw Frank in town, or was he following me?” They are two alternative hypotheses to explain the same observation: In the first scenario, we assume that Frank was going about his business and just happened by chance to be in the same place as I. In the second, we assume Frank was following me and that’s why he was in the same place. The question is about the hypothesis invoked to explain the observation. “Coincidence” is a (null) hypothesis.
Again, the chance that the ten heads occurred "by chance", "occurred coincidentally" or "is a coincidence" is not 1/1000. IF they occurred by chance, the probability for such a thing to occur (again) is 1/1000.
1/36 is the wrong answer for the question "what are chances this is a coincidence?". That probability is unknown, because it depends on whether the dice are actually fair, and what other dice are there. For example, if you have to discriminate between fair dice and unfair dice with only 2s on them, a 12 would indicate that with 100%, it was a coincidence.
You might ask differently though: "What WAS the probability to throw a 12 with two fair dice?". But that probability collapsed to 100% when you actually throw them and got the result.
Again, I'm saying I think people would interpret "what are the chances this is a coincidence" as "what are the chances of this occurring coincidentally (i.e. by chance, naturally, not influenced by an outside force)", to which they would answer 1/36.
The point is that, from the measurement alone, you cannot make a statement of whether the null hypothesis is true. You can only make a statement how likely the observed outcome was /if/ the null hypothesis is true.
(edit: I realize that you mean this. I just wanted to make it clearer. The article should have said:
It's a 1/1000 chance that a measured difference of this or larger magnitude occurs as a statistical fluctuation assuming the SM)
It's like this:
The chance to get 10 heads with a fair coin is <1/1000. I.e., if you use the same coin many-many times, <1/1000 of these 10-throw runs will have all heads, on average.
This does not mean that, if you get 10 heads, it's a fair coin with 1/1000 probability. In the strongest sense, without further information, one can not make any statement about that probability.
Yeah. My point is this "There's a 1 in 1024 chance of this measurement being a statistical coincidence." I understand this as "There is a 1:1024 chance that a statistical coincidence is the cause of this result".
But that's wrong, the statement must be: If it is a statistical coincidence, it had a probability of 1:1024 of occurring. But then the probability that it was cause by a statistical fluctuation is 100% -- It's assumed to be true.
I did not even see this at first. But they did really write that the chance of "no new physics" is 1:1000, right? So they gave "there is new physics" interpretation a huge probability.
Seriously, I completely glanced over this. Slightly embarrassing.
In any case, if the LHC runs thousands of such experiments, we do expect such signals, right?
Even after you explain it, I can barely grasp the significance. Given the expected level of understanding of someone reading a BBC article about this topic, I don't think they are wrong at all in explaining it that way - that is, I don't think their intended audience would take the message differently to any extent whatsoever if they had explained the way you do.
To be more specific, to the average BBC reader, the phrases
The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance that the measurement is a statistical coincidence.
and
The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance to have seen this data even if the particle doesn't exist.
convey the exact same message, the first one just uses fewer words.
Look, that may be so, but if it is, then they should either omit such a line entirely so as not to mislead their readers, select better language so that we don't collapse concepts which are fundamentally, completely, different from each other, or they could try to educate the public on a distinction which is fundamental to science.
I mean, we might as well say that the BBC should just use the words "million" and "billion" interchangeably because most readers have no sense of scale.
Bottom line: thanks to this line, the reader is likely to think that new physics has very likely been discovered, when the opposite is the case.
I don't agree. The whole paragraph makes that clear - 1 in 1000 is actually pretty good odds that this is just a coincidence, and most people should know this intuitively.
> The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance that the measurement is a statistical coincidence. So people should not get carried away by these findings, according to team leader Prof Chris Parkes, from the University of Manchester.
The problem with it is that layman people believe that both of these statements are equal to "it's a 999/1000 chance that it was something else". Which is not true.
The difference in these two formulations is that for b) it's explicit wrong, for a) this is arguably what the article says (which is not what the scientists say)
The article can be read as "there is a 999/1000 chance that this is not a coincidence". This is strictly speaking correct, because it doesn't specify what the coincidence would be.
The correct interpretation is "there is a 999/1000 chance that you wouldn't see this data if the particle didn't exist" / "there is a 1/1000 chance that you would see this data if the particle didn't exist".
The wrong interpretation that still agrees with the statement is "there is a 999/1000 chance that the particle exists given that we have seen this data" / "there is a 1/1000 chance that the particle doesn't exist given that we have seen this data".
P(data | no particle) = P (no particle | data) * P (data) / P (no particle). As a layman, I have no idea what P(data) is, and I think no one can give a convincing estimate for P(no particle).
Since P(data | no particle) and P(no particle | data) are in fact proportional, the only thing I should really care about as a layman is the value of any one of them. I any way can't evaluate myself what would be a convincing probability, since I don't have any proper priors.
No, not quite. The probability that this is not a coincidence is unknown. The probability that you SAW the data if the particle didn't exist is 100%. The probability that you will not see it /again/ is 999/1000.
The probabilities 1/1000 (or 999/1000) are only meaningul probabilites for something in the world where in fact it was a coincidence. In any other world, they are not. So saying "there is a 999/1000 chance that this is not a coincidence" isn't true, as the calculation of 999/1000 must assume that it fact it IS a coincidence.
How many iterations that could create this result do they run? 1 in 1000 sounds unlikely, but for all I know they have run this experiment 50,000 times.
Not sure I entirely understand your question but I'll try to explain a bit anyway:
they're using a dataset of 9fb^-1. That means it includes 9 events for a crosssection of 1fb (femtobarn). Now the paper doesn't seem to include what crosssection their events have but if we assume something of the order of magnitude of 1pb then the dataset would contain around 9000 events of interest.
Now all that doesn't really matter as this is already factored into the standard deviation of their result. They have enough data to say it's a 3 sigma (being the standard deviation) deviation from the standard model. Now this "1 in 1000" really just means that the null hypothesis (the Standard Model) says there's a 0.1% chance for that result to happen. Of course it could also be that they forgot to factor in some uncertainty of their measurements and their sigma is actually much bigger. But it surely won't be the size of their dataset as this is quite obvious and easy to take into account.
I would guess there are many more than thousands of such experiments that have been run, testing all the various permutations of dozens (or more) of different beyond Standard Model physical theories.
Testing different models is done in the analysis of the data, not in running the experiment differently.
The "experiment" (colliding protons together) has been repeated quadrillions of times at the LHC. But there are only a few parameters you can change about it, namely the energy and how focused the beams are. Altering the detectors to change/improve how data is collected is an expensive and slow process.
Fair enough; what I meant is "multiple testing" in the context of a single overarching experiment, which is I believe what the comment I was replying to was getting at as well.
In any case, you have a point. Whether multiple analysis, multiple channels or multiple experiments, you have a look-elsewhere effect, and that can easily knock off one or two sigmas. If you look at a 10000 possibilities, you will a couple with 3 sigma difference, just by chance.
LHC looks at MANY possibilities. For a while, they tried to keep track to quantify the look-elsewhere effect. I think they have given up on that.
It'll be in operations for years if not decades to come still. They're working on an upgrade to increase the 'luminosity' (dunno what that means yet) by a factor 10 as we speak, slated to be finished in 2027 (see https://en.wikipedia.org/wiki/High_Luminosity_Large_Hadron_C...)
Luminosity is the number of particles (in the LHC's case, protons) flowing per unit area and unit time.
Additionally, integrated luminosity is luminosity integrated over time, and is just the number of events produced per unit area. It is the main metric used when CERN releases data and shares just how many events are in a given data set; this is done such that you can take the cross section of a given event (like Higgs production), multiply it by this value, and get how many events of that type happen (how many Higgs were produced).
It’s very common for BBC headlines to change 3-5 times after being posted. I don’t know whether they are A-B testing or just twitchy, but it’s annoying for sharing new articles
> I don’t know whether they are A-B testing or just twitchy
Have worked in the dark basements for a news company, it's A-Z testing for some online pieces to see what gets more fish on the hook. They'll use wildly different headlines without changing a single word in the article.
FTR, OP here. I didn’t change the title. Perhaps HN will comment. In my experience their reasoning is typically solid.
When I posted, I believe it was “LHC machine finds tantalising hints of new physics”. I remember that seemed oddly redundant, like an “ATM machine”. Current title for the article is showing as “Machine finds tantalising hints of new physics”, but a search is also coming up “LHC machine challenges leading theory of physics”.
A mod changed it, I assume on the grounds that the article title was baity. That's in keeping with the site guidelines: "Please use the original title, unless it is misleading or linkbait; don't editorialize."
3 sigma is termed "evidence" in particle physcis (while "discovery" is reserved for 5 sigma) and is often enough to get people interested. Keep in mind that these are just numbers and must be interpreted in context. There have been tensions in various heavy flavour measurements for a looong time and across multiple experiments. It is very plausible that this is where we'll finally see new physics at the LHC. So it is worth serious consideration.
The super-luminous neutrinos had 6 sigma significance and still no one took it seriously because it was simply such a ridiculous claim. Obviously the number of zeros in your p-value don't mean a damn if you haven't plugged in your equipment correctly!
Unlike that 750 GeV lump, there are other observables in this case which build a consistent picture. Some fits to Wilson coefficients in b->sll were at almost 7σ even before this new result.
I don't know much about physics (I am trying to learn more), but does anyone else find the idea that the universe is made of "little balls" fundamentally wrong? It just feels like it will never end. First, we thought that atom is fundamental. Then electrons, protons and neutrons were discovered. Then, we discovered that there are smaller particles. Are we ever going to discover a fundamental particle that cannot be broken up? What would it be made of? How much space would it take up? Just some armchair philosophy.
Do not think about "little balls". It's a fundamentally broken mental image that everyone was taught in high school chemistry. Already at atomic level things are adequedly expressed only as wave functions. Matter is not little balls made up of even tinier balls, but something altogether stranger - recall that matter and energy are interchangeable. I like to imagine the subatomic particles (like neutrons and protons) as beautiful rays of energy only temporarily trapped in particle form as ugly matter.
As far as we know, leptons are not composite. They might be able to decay, but a muon or electron is fundamental. It's not made up from something else. Quarks seem to be fundamental too. Same for photons.
We are pretty confident of this, because the theory describing them is so precise -- QED is the best tested theory of all, to about 14 digits IIRC. In fact, a big factor in the discovery that a proton is a composite system was that it could not be described by QED, it has a anomalous magnetic moment.
I know nothing of physics, but I'm just curious - could you explain in layman's terms how one could say an electron is fundamental without infinitely precise measurement tools?
100% sure is not possible, but there is some good circumstantial reasons.
Let's use the bad model that an electron is a small ball made of some magic material. And that the material inside it is even, there are not more dense parts. Also the charge is distributed evenly, it's not concentrated in some parts.
The electron is spinning, so you imagine that the ball is spinning. So you can calculate the angular momentum of the electron, assuming it's an even ball of a magical material. The angular momentum can be measured experimentally, so you can calculate how fast the electron is spinning, assuming it's an even ball of a magical material.
It has charge, and the charge is moving, so it is like a small magnet. You have calculated how fast it is spinning, and you can calculate the magnetic moment of the electron, assuming it's an even ball of a magical material.
Now you go to the lab and measure the real magnetic moment of the electron and it is twice the value of the number you got assuming it's an even ball of a magical material. This number is called g, so for an electron g=2 (actually almost 2).
You can repeat the same calculation for protons, and the g of the proton is g~=1.410606...
For an elementary particle, there are theoretical reasons to be sure that g=2. So the conclusion is that the electron is an elementary particle and the proton is a composite particle.
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Bonus: Actually, you can get a perfectly isolated electron alone, because there are nasty virtual particles floating around. You can't see the virtual particles, but they cause small corrections in the experiments with high energy particles. In particular, the g of the electron is not exactly 2 because these virtual particles cause a small correction. The value is approximately g=2.00231930436182(52) https://en.wikipedia.org/wiki/Electron_magnetic_moment
If it smell to much hand waving, don't worry. There are very good models for all the nasty virtual particles, and you can make a long calculation of the effect of them, and calculate these correction. You can make the theoretical calculation and the experimental measure and they agree with 10 significant figures. They prefer to publish a=(g-2)/2 and
You can't. It's a universal philosophical limitation on science. One humorous way to phrase it would be, "there could always be a gnome hiding behind the camera."
You have got to see the implicit, unspoken qualifiers that are on all statements like that. "It would be counter to all known patterns if...", "it would have to be extraordinarily small, beyond unimaginable sensitivities, if..." and "we can't imagine any practical distinction between what it seems like and what it might be," are all reasonable interpretations of the statement "it isn't." The only unreasonable interpretation would be the literal one.
(P.S. It is not actually fundamental, it is made up of right-electrons and left-electrons, coupled together.)
https://theconversation.com/amp/evidence-of-brand-new-physic...