[HN Gopher] Measurement of the W boson mass reveals 7s deviation...
___________________________________________________________________
Measurement of the W boson mass reveals 7s deviation from
calculations
Author : nvalis
Score : 324 points
Date : 2022-04-08 09:32 UTC (13 hours ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| fallingfrog wrote:
| I would guess that unless some other team replicates this result,
| it's probably a measurement error somewhere. Physics can be very
| delicate and tricky, and it's easy to make mistakes. But, even
| the mistakes are opportunities for learning, so it's not a waste.
| chris_overseas wrote:
| Discussed here: https://news.ycombinator.com/item?id=30948260
| andyjohnson0 wrote:
| Thanks. As a general reader, I found that article much more
| accessible than the Science article.
| bejelentkezni wrote:
| The duality of man[0].
|
| https://news.ycombinator.com/item?id=30952583
| codezero wrote:
| How is it that several other measurements have error bars that
| don't even overlap with this one?
| Kinrany wrote:
| Reminded me of the recent
| https://slimemoldtimemold.com/2022/01/11/reality-is-very-wei...
| CrazyStat wrote:
| Error bars account for the known and quantifiable sources of
| uncertainty. They don't (can't) account for unknown or
| unquantifiable sources of uncertainty, such as aspects of the
| experimental design that were not properly accounted for or
| unpredicted/unmodeled interactions with other particles or
| forces.
|
| Known unknowns and unknown unknowns, as Rumsfeld would put it.
|
| About a decade ago I saw a very nice figure of estimates of the
| speed of light over time showing this effect. Unfortunately I
| haven't been able to find it since.
| brummm wrote:
| Just a small comment about the speed of light. The way we now
| define the speed of light, measuring it doesn't really make
| sense anymore. The speed of light is now DEFINED as 299792458
| m/s and the meter definition is based on the speed of light.
| So in principle, one can only measure the meter and not the
| speed of light anymore.
| rightbyte wrote:
| In vacuum.
| enchiridion wrote:
| Would it be the same in a hypothetical completely
| homogeneous gas?
|
| My assumption is that turbulent changes in pressure cause
| diffraction, causing the light to not take a perfectly
| straight path. I don't know enough about physics to know
| if that's right.
| liminvorous wrote:
| Materials seem to have different refractive indices for
| some sort of complicated quantum reason that only relies
| on the inhomogenity because of materials being made up of
| atoms containing electrons, not an sort of macroscopic
| inhomogenity.
|
| https://www.physicsforums.com/threads/how-does-
| refraction-wo... is the thread I'm basing this on
| CodesInChaos wrote:
| The speed of light in a medium is the inverse of the
| refractive index of that medium. It's caused by the
| interaction between the electrons in matter (bound to
| atoms) and electromagnetic fields. It does not require
| inhomogenities larger than the atomic structure.
|
| https://en.wikipedia.org/wiki/Refractive_index
| codezero wrote:
| Thanks for the reminder, this makes sense.
| aspenmayer wrote:
| I found something similar on page 19 of this presentation. No
| errors bars, but they do provide some info about the errors
| of various experiments.
|
| https://www.nhn.ou.edu/~johnson/Education/Juniorlab/C_Speed/.
| ..
|
| Edit: here's some error bars!
|
| https://www.researchgate.net/figure/Uncertainties-in-
| Reporte...
| derbOac wrote:
| I love that second paper!
| CrazyStat wrote:
| Thank you! That's not the exact figure I remember seeing,
| but it's probably the same data.
| XorNot wrote:
| If this result turns out to be right, at least part of that
| confirmation will involve producing a theory which reduces
| down to explaining other results - either from previously
| unknown systematic error or interactions.
| CodesInChaos wrote:
| Even if you only consider statistical errors, there is no
| guarantee that the actual value is in the confidence interval.
| The graphs in this article seem to use 1s bars which have a 68%
| chance of containing the result, assuming a normal
| distribution.
| imtemplain wrote:
| [deleted]
| mc4ndr3 wrote:
| If my calculations were off by seven standard devs I'd quit
| science and go skip rocks. wth
| beefield wrote:
| Talking about particle/quantum physics, is there a book/youtube
| channel/whatnot that would describe (some/main) experiments and
| results that have convinced physicists that classical physics
| does not work when you go small. I mean, I know about double slit
| experiment, but I guess it is a long journey from that to the
| Standard Model.
|
| So instead of the heavy theory, I'd like to see the stuff that
| made people scratch their heads in the first place.
| simonh wrote:
| This is a bit old, but still excellent.
| https://www.youtube.com/watch?v=XYcw8nV_GTs
|
| This is more up to date and specifically on challenges to the
| SM. Where is physics going? | Sabine Hossenfelder, Bjorn
| Ekeberg and Sam Henry
| https://www.youtube.com/watch?v=b8npmtsfsTU&t=2306s
| mr_mitm wrote:
| The first real head scratchers were the black body spectrum [0]
| and the fact that atoms are stable.
|
| Rutherford [1] showed that atoms consist of a tiny, positively
| charged nucleus and rather large negatively charged shell. It
| was hypothesized that electrons are flying around the nucleus
| like planets around the sun. But we already knew at that point
| that moving charges emit radiation, which causes the electron
| to lose energy and move closer to the nucleus. So it should
| pretty much immediately collapse into a point. Bohr then showed
| that if you assume that only certain orbits were allowed, it
| works out pretty nicely. Nowadays we now that there is such a
| thing as a ground state, meaning the lowest amount of energy
| the electron can possibly have around a nucleus is enough to
| keep it moving.
|
| The idea for quantizing things came from observing the black
| body spectrum. If you sum up all contributions classically, you
| get infinity. Planck tried to see what happens if you assume
| that energy comes in little packets instead of a continuous
| spectrum. He didn't have any justification for it, but it
| matched the observations pretty well.
|
| [0] https://en.wikipedia.org/wiki/Black-body_radiation
|
| [1] https://en.wikipedia.org/wiki/Rutherford_model
| Splendor wrote:
| Maybe not exactly what you're looking for but these two videos
| discuss the results of a Fermilab experiment that hints at a
| crack in the standard model.
|
| https://www.youtube.com/watch?v=kBzn4o4z5Bk
|
| https://www.youtube.com/watch?v=O4Ko7NW2yQo
| jrpt wrote:
| Quantum physics is a separate (but related) branch from
| particle physics so using the slash "quantum/particle" is
| mixing up two different things - which one do you really want?
|
| Theoretical Concepts in Physics by Malcolm Longair is a mix of
| history and physics, by explaining how physicists came to
| discover their theories. I actually don't think it says much
| about modern particle physics though. It includes quantum
| mechanics.
|
| Introduction to Elementary Particles by David Griffiths if you
| just want particle physics. Griffiths also has an intro book on
| quantum mechanics.
| nyc111 wrote:
| Do we actually know how physicists define "mass" in this context?
| Because, in physics many words have technical meanings that only
| physicists can know. For instance, as a layman when I see the
| word "particle" I imagine a spherical thing with an extension in
| space. But a physicist would laugh at me because in physics a
| particle is not a particle, it can be a statistical bump in data,
| it can be a field, it can be a wave, anything but a spherical
| particle. But a physicist would call a wave a particle and see
| nothing wrong with it. The same goes for mass, what physicists
| call mass can be voltage for instance. So does anyone know what
| "mass" means in this context?
| neals wrote:
| What is a sigma?
| EVa5I7bHFq9mnYK wrote:
| It's just a way to say something has probability of
| 0.0000000002% while looking smart.
| WanderPanda wrote:
| It actually is smart to compress this on an exponential scale
| instead of writing a large number like this :p
| cshimmin wrote:
| I work in this field (different experiment); despite the
| downvotes this is a reasonable question. Reposting my comment
| from above, since there is confusion here (the other sibling
| comments are incorrect).
|
| In particle physics, sigma denotes "significance", not standard
| deviation. Technically what we're quoting as "sigmas" are
| "z-values", where z=Phi^{-1}(1 - p), where Phi^{-1} is the
| inverse CDF of the Normal distribution and p is the p-value of
| the experimental result. So, 7 sigma is defined to be the level
| of significance (for an arbitrary distribution) corresponding
| to the same quantile as 7 standard deviations out in a Normal
| distribution.
| yccs27 wrote:
| This is the correct answer.
|
| In other words, "z sigma" means: That a result like this
| occurs as a statistical fluke, is just as likely as a
| standard-normal distributed variable giving a value above z.
| sgregnt wrote:
| I would add: If the null hypothesis is true, then "the
| result like this... (in this case the null hypothesis is of
| cause that the standard model is true)
| mike_ivanov wrote:
| If the null hypothesis were true, _and the experiment
| were repeated infinite number of times with a different
| sample each time_ then "the result like this _or more
| extreme_ ...
| spekcular wrote:
| I agree with adding the "more extreme" part, but I'm not
| so sure about the infinite number of times part.
| Certainly, the p-value is (roughly speaking) the
| probability of seeing a result at least as extreme as the
| observed result, under the null hypothesis. But one
| doesn't really need to introduce hypothetical infinite
| sequences of replications to make sense of that
| definition.
| maybelsyrup wrote:
| Isn't the bit about repeating the study over and over
| again the whole basis of frequentist statistics, though?
| (Indeed isn't that why it's called frequentism?)
| spekcular wrote:
| Sort of. You don't need identical replications of the
| same experiment, just long run probabilities for any
| application of the method. See example two here:
| https://normaldeviate.wordpress.com/2012/11/17/what-is-
| bayes...
|
| (The author is a stats professor at CMU.)
|
| Quoting: "The plot shows the first 50 simulations. In the
| first simulation I picked some distribution {F_1}. Let
| {\theta_1} be the median of {F_1}. I generated {n=100}
| observations from {F_1} and then constructed the
| interval. The confidence interval is the first vertical
| line. The true value is the dot. For the second
| simulation, I chose a different distribution {F_2}. Then
| I generated the data and constructed the interval. I did
| this many times, each time using a different distribution
| with a different true median. The blue interval shows the
| one time that the confidence interval did not trap the
| median. I did this 10,000 times (only 50 are shown). The
| interval covered the true value 94.33 % of the time. I
| wanted to show this plot because, when some texts show
| confidence interval simulations like this they use the
| same distribution for each trial. This is unnecessary and
| it gives the false impression that you need to repeat the
| same experiment in order to discuss coverage."
| maybelsyrup wrote:
| Yeah, that's what I remember from grad school. Thanks for
| the link!
| Filligree wrote:
| What's that in Bayesian terms?
| hedora wrote:
| The probability of N(1,1) emitting >= 7. (So, one minus
| the CDF of the normal distribution at 7)
| a1369209993 wrote:
| > sigma denotes "significance", not standard deviation.
|
| Nitpick: this is still a standard deviation in _some_
| (potentially very contrived and nonlinear) coordinate system.
| (As a simple example, a _log-_ normal distribution might have
| a mean of 1 and a standard deviation effectively of
| multiplying or dividing by 2. Edit: also, multidimensional
| stuff might have to be shoehorned into a polar coordinate
| system.) But in practice you'd never bother to construct such
| a coordinate system, so that's more a mathematical artifact
| than anything useful.
| cshimmin wrote:
| No, there is no coordinate system. This is referring to the
| distribution of a test statistic for hypothesis testing.
| It's a 1-d real scalar, and coordinate transforms don't
| have any meaningful statistical representation. Of course
| there are much higher-dimensional distributions, in all
| sorts of coordinate systems, involved in sampling the test
| statistic, but at the end of the day this is all you are
| left with. If you change the underlying distributions of
| the model, then of course you will change the test
| statistic distribution, but that's meaningless, since the
| whole point of the test statistic is to quantify an
| observation in the context of a given model.
|
| Anyway, as I mentioned elsewhere, the motivation for
| calling it sigma is that, by construction, it maps onto the
| quantiles of the standard Normal distribution. So an
| N-sigma result will have the same p-value as N standard
| deviations in a Normal distribution. So you can associate
| "sigmas" with "standard deviations of the Normal
| distribution". Perhaps this is what you are trying to say,
| but it does not make sigma a standard deviation in any
| statistical sense, i.e. it is not necessarily related to
| the variance of the relevant distribution.
| jxm262 wrote:
| oh wow, thanks for pointing this out :)
| cshimmin wrote:
| For what it's worth, sigma is chosen for this purpose
| specifically to evoke the notion of "standard deviations".
| But quoting the std dev. directly is useless, since the
| distribution is unspecified. So we "convert" the
| statistical significance to the corresponding number of
| standard deviations of the Normal distribution, since that
| is a familiar distribution. If you like, it's another way
| of stating p-values, which physicists prefer because ours
| can have lots of zeros :)
| omginternets wrote:
| A standard deviation.
| jstx1 wrote:
| 1 sigma = 1 standard deviation
| throw0101a wrote:
| A unit used in statistics:
|
| > In statistics, the standard deviation is a measure of the
| amount of variation or dispersion of a set of values.[1]
|
| * https://en.wikipedia.org/wiki/Standard_deviation
| tempay wrote:
| This page is likely more approachable:
|
| https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rul.
| ..
| sundarurfriend wrote:
| I thought you were going to link to
| https://simple.wikipedia.org/wiki/Standard_deviation
|
| The "Simple English Wikipedia" is a really underrated
| resource for understanding jargon outside your field.
| RosanaAnaDana wrote:
| A measurement of uncertainty.
| londons_explore wrote:
| Does it make sense to even discuss the sigma of any deviation?
|
| When you add in the "10% chance that some scientist messed up the
| maths or something in the experiment", then it's impossible to
| ever reach 7 sigma...
| davrosthedalek wrote:
| Yes. The meaning of 7 sigma is: It's very very unlikely that
| this is a statistical fluke, it must have a different reason
| (new physics, systematic error, ...)
| bawolff wrote:
| Then it would never make sense, because someone messing up
| somewhere is always a possibility.
|
| I would assume that the implication is that its 7 sigma
| assuming the measurements were done correctly.
| TheRealDunkirk wrote:
| Yeah, my thought from reading the headline was, "That's a funny
| way of saying we were completely wrong."
| morelandjs wrote:
| Known unknowns, and unknown unknowns. Still useful to quantify
| the known unknowns and compare significance of various events
| according to them.
| amelius wrote:
| If a quantity cannot be negative (such as a mass), then
| standard deviation isn't the best choice.
|
| EDIT: Yes, because the Gaussian distribution extends to +/-
| infinity; davrosthedalek explains it best, below.
| bigbillheck wrote:
| The predicted value is so incredibly far from zero that you
| can pretend it's a truncated Gaussian and not see any actual
| difference in the results.
|
| Alternate reply: Gaussian approximation to the binomial is
| perfectly valid in all sorts of cases.
| hhmc wrote:
| A fair dice roll can only have positive values {1,2,3,4,5,6}
| but it has a clearly defined std deviation: sqrt(105/36) --
| there's no clear reason this isn't the 'best choice' that's
| just a case of application.
| mhh__ wrote:
| The point about applications is mostly valid even if
| theoretically unsatisfying, but I think the thing about
| dice rolls is basically spurious.
| gus_massa wrote:
| You can calculate the mean m and the standard deviation s
| of a dice roll. You get m=3.5, s=sqrt(105/36)~=1.707... .
| It's not very similar to a Gaussian, but sometimes these
| numbers are useful anyway.
|
| It's more interesting if you calculate the distribution
| of the sum of rolling 100 dices. It's easy to calculate,
| becuase m=100*3.5=35, s=sqrt(100*105/36)~=17.07... But
| now the distribution is very similar to a Gaussian with
| m=100*3.5=35 and s=sqrt(100*105/36)~=17.07...
| https://en.wikipedia.org/wiki/Central_limit_theorem They
| are not equal because the sum of the roll of 100 dices is
| bounded between 100 and 600 and the Gaussian is not
| bounded. For most applications, you can just use the
| Gaussian instead of the exact distribution.
| cedilla wrote:
| What would be a better choice?
| FabHK wrote:
| GP is probably referring to the coefficient of variation,
| sigma/mu (standard deviation divided by mean), which
| normalises out for example the unit of measurement.
|
| However, the 7 here is basically (x - mu)/sigma, so it is
| normalised (in that sense), anyway.
| davrosthedalek wrote:
| No, I think the problem (in principle) is that "standard
| deviation" has a special meaning for Gaussian
| distributions, which extend to infinity in both
| directions. A quantity that has a fixed range has most
| likely an asymmetric distribution, so one would expect an
| asymmetric error bar as well. But for a sigma<<the value,
| it's often not a big concern.
|
| A good example is efficiency measurements. I can't count
| how often I have seen students say something like: Our
| detector is 99%+-3% efficient. Obviously a detector can't
| be 102% efficient.
| spekcular wrote:
| What's wrong with saying "Our detector is 99%+-3%
| efficient," if they are giving the output of some
| procedure that constructs valid confidence intervals? The
| confidence intervals will trap the true value 95% of time
| (or whatever the confidence level is). If it does what it
| promises to do, I don't see the problem.
| davrosthedalek wrote:
| Because a 99+3=102 is not a valid upper interval bound.
| You cannot have >100% efficiency for a detector. Also,
| your expected value cannot be centered. So maybe 99+1-3
| is a valid range (but I would be very suspicious if the
| bound includes 100%)
| spekcular wrote:
| I agree 102% is not a possible value for the efficiency
| of the detector. But if the confidence interval traps the
| true value of the efficiency 95% of the time upon
| repeated sampling, what's the problem? That's all that's
| required for a confidence interval to be valid. Some CI
| constructions do in general give intervals that include
| impossible parameter values, but if they contain the true
| value 95% of the time, there's no issue. The coverage
| guarantee is all that matters.
|
| (One should not confuse a CI with a range of plausible
| values, in other words.)
| davrosthedalek wrote:
| Ok, true, in that sense, it's fine. However, in 100% of
| cases I have observed so far (and they were far too
| many), it means that the person who gives such a result
| used sqrt(counts) as the error estimate, and that's not
| correct -- not only for the upper bound, also for the
| lower bound.
| [deleted]
| bigbillheck wrote:
| > "standard deviation" has a special meaning for Gaussian
| distributions,
|
| I have a master's degree in statistics and this is the
| first I'm hearing about it.
|
| > Our detector is 99%+-3% efficient. Obviously a detector
| can't be 102% efficient.
|
| In the absence of any other context I'd guess that
| they're using an approximation to a confidence interval
| that might be perfectly fine if the estimated value was
| nearer the center of the allowable range.
| davrosthedalek wrote:
| Well, special in two senses: First, in the canonical
| formula for Gaussians, sigma appears directly. For the
| case at hand, the confidence limits associated with 1
| sigma, 2 sigma etc. in physics match exactly the area
| under the curve for a Gaussian integrated +- said sigma
| around the mean. That's were that connection actually
| comes from, and a physicist will always think: Within 1
| sigma? That's 67%.
|
| Hearing 99+-3% is a very strong indication that the
| person used an incorrect way to determine the
| uncertainty, most likely by taking the square-root of
| counts. But you are right, if the efficiency would be
| around 50%, that approximation is not so bad.
| FabHK wrote:
| When you look at the graph at the bottom, several independent
| measurements have non-overlapping error bars, and are even on
| opposite sides of the Standard Model prediction. So, yeah,
| somewhere along the line there've been bad measurement
| errors...
| davrosthedalek wrote:
| Since error bars are typically +-1 sigma, you expect about
| 1/3 of all measurements to be further away from the true
| value than the error bar, if all error estimates are correct,
| and uncorrelated. That's actually a check a lot of doctored
| data fails.
| mhh__ wrote:
| This is why these measures have to be taken with a grain of
| salt (but are still useful).
|
| Probability is subjective, in this case because it's dependant
| on the design of the experiment / quality of the analysis of
| that experiment to determine a p-value of a given result.
|
| The book "Bayesian analysis in high energy physics" is a short
| and sweet introduction. If I got the title wrong I'll update it
| later.
| freemint wrote:
| 7 sigma is actually less than one thinks because these
| distributions are not normal distributions.
| bawolff wrote:
| Why aren't they normal? I know very little about this topic,
| but i would generally assume that measuring most natural
| phenomenon would be normal.
| krona wrote:
| Also not knowing anything about this topic, I'd assume it
| _wasn 't_ normal because we're talking about mass close to
| zero, and mass must be greater than zero.
| gus_massa wrote:
| The mass in their result is 80433.5+-9.4 MeV/c^2. The
| result of the experiment is a Gaussian like distribution.
| If you consider a Gaussian distribution with m=80433.5 and
| s=9.4, the probability to get a result that is less than 0
| is 4E-15899105.
|
| I filled this widget https://www.wolframalpha.com/widgets/v
| iew.jsp?id=53fa34c5c66...
|
| And got this result https://www.wolframalpha.com/input?i=me
| an%3D%5B%2F%2Fnumber%...
|
| Note in the graphic that s is 10000 smaller than m so the
| probability to get a negative result is almost zero and you
| can just ignore it.
| rich_sasha wrote:
| Especially since, isn't this an average / error of a mean
| estimate? So even if individual observations are non-normal,
| this would be a perfect place for Central Limit Theorem.
|
| I know nothing about Quantum though, only maths.
| freemint wrote:
| Because it's a non-linear world? And the graphs seem very
| obviously skewed? And it's kurtosis also seems to differ
| from three?
| rich_sasha wrote:
| None of those things matter to the central limit theorem.
|
| If I have IID observations with finite 2nd moment
| (variance), then their average will pretty quickly
| converge to a Gaussian distribution. And I can relax a
| lot of this and still recover a variant of CLT.
|
| Of course maybe the calculation is different, eg it's not
| like there are N independent observations, but rather
| some other complex condition solved for the mean
| estimate.
| cshimmin wrote:
| Basically, the result of an experiment has to be boiled down
| to a single numerical value, called the test-statistic.
| Typically the test-statistic is a (log) likelihood ratio. It
| is the distribution of the t.s. that must be considered when
| determining the significance of a measurement. Obviously the
| measurement itself only gives you a single value of the t.s.,
| so you need to know the distribution to ask "does this result
| seem significant?". This is done by considering all the
| factors of random variation (statistical and systematic) that
| could have an effect on the t.s. Often, the distributions of
| these individual random factors are assumed to be Normal, but
| the resulting distribution considering all of their
| conspiring effects is very seldom normal distribution. Even
| in the central limit theorem, I think the distribution of the
| LLR ends up being something like a noncentral chi^2
| distribution.
| ivad wrote:
| A measurement being 7 sigma out would still be Chebyshev
| bounded by 1/7^2 [?] 0.02 I.e. the probability of it being >=7
| sigma out is interestingly at most 0.02.
| freemint wrote:
| Neat i didn't think about that. But that is less improbable
| then 1 in 12450197393 which is what you might get with normal
| distribution.
| lupire wrote:
| That's just because Chevyshev bounds is a very weak general
| statement about _all_ distributions.
|
| High Energy Physics sigma is calibrated to match normal
| distribution quantiles.
| lupire wrote:
| That is not so interesting because it could be far _less_.
| cshimmin wrote:
| I work in this field (different experiment); that's not really
| true. In particle physics, sigma denotes "significance", not
| standard deviation. Technically what we're quoting as "sigmas"
| are "z-values", where z=Phi^{-1}(1 - p), where Phi^{-1} is the
| inverse CDF of the Normal distribution and p is the p-value of
| the experimental result. So, 7 sigma is _defined_ to be the
| level of significance (for an arbitrary distribution)
| corresponding to the same quantile as 7 standard deviations out
| in a Normal distribution.
| habitue wrote:
| > Surprisingly, the researchers found that the mass of the
| boson was significantly higher than the SM predicts, with a
| discrepancy of 7 standard deviations. --JS
|
| This is from the editor's comment at the top of the article,
| I'm guessing it was a mistake, but that might be why people
| are getting thrown off by it
| Aachen wrote:
| I'm one of those dumb people that didn't have much math or
| greek in school, so this weird-looking o in the title was
| quite literally Chinese to me. Now it turns out that people
| in the know also misunderstood its intended meaning because
| it's in a different field.
|
| For years I've argued foreign symbols and single-letter
| variable names mainly seem to serve to keep a walled garden
| around the sciences, and this was cemented when I eventually
| went for a master's degree and I was expected to do this as
| well in compsci to get a better grade even if there is no
| advantage. If we could just write what we mean, I suspect
| people would find that more useful even if it makes it look
| less cultivated and more mainstream.
|
| (To be clear, this is not criticism on the person I'm
| replying to, but split between the author of this specific
| title and most of the sciences as a whole because it's a
| universally supported barrier (if only ever implicitly),
| aside from a few science communicators.)
|
| Edit: scrolled further in the thread. Looks like I'm not the
| only one, though this person at least knew to name the sigma:
| https://news.ycombinator.com/item?id=30955621
| bigbillheck wrote:
| When you see a symbol you don't recognize, like 's', you
| can just paste it into google and it'll tell you.
|
| I personally don't see why greek letters are such a big
| sticking point, there's only 24 of them, and unlike Greek
| children you don't have to learn them all in one go.
| cshimmin wrote:
| It is just a convention, specifically for interpreting and
| presenting experimental results. We also use sigma to
| represent standard deviation in other contexts, of course.
| Sometimes it represents Pauli spinor matrices. Sometimes
| it's an index for spacetime tensors.
|
| Life would be hell for any practitioner without single-
| letter abbreviations. In fact, we like them so much, that's
| why we adopted the greek letters (we ran out of alphabet).
| And, for better or for worse, convention runs deep in
| scientific literature. In practice it reduces a lot of
| redundancy, makes it more efficient for researchers to skim
| and understand results. But the cost is a years-long
| learning curve to break into any scientific field's
| literature.
|
| FWIW, the linked article is from the journal Science, which
| is a technical publication. Often "sigma" is omitted in
| sci-comm articles, or at least is translated for the
| reader. They will say something like "there is a one in X
| million chance this is a fluke".
| indymike wrote:
| Looking up from my screen filled with sanity saving
| conveniences like having to type /sigma to get a really
| smart looking lower case greek character to display so
| the masses can't make sense of my math.
| jacquesm wrote:
| Those APL people may have been on to something after all!
| LudwigNagasena wrote:
| Notation is the easiest (and a very helpful) part of
| physics, statistics and probably all other scientific
| areas. That just sounds like an excuse.
| Aachen wrote:
| I've heard my complaint be called an excuse before, but
| consider that it's also the first barrier. Not a big one
| when you already decided to take a course, when you're
| seriously interested, when you just look them up and soon
| enough you know the conventions in the field. That's
| different from casual reading on HN, though. And tell me,
| are scientists not a class that is looked up to where you
| live? The common Joe might not explicitly say so, but if
| someone is a "scientist" then you don't expect them to be
| stupid or muck out stalls; they do have some real status.
| This doesn't come from doing things that seem like any
| common Joe can do it, yet a lot of the work is just that.
| Once you start paying attention to how often "new
| research" in the news amounted to a big survey and very
| basic statistics, or playing around with a Kinect in a
| train station to learn about walking patterns, it doesn't
| seem so different from what regular HN readers do for a
| living. If you take the paper behind such a survey, it'll
| turn out to be full of complexity that is a lot harder to
| get through than necessary. It could be a lot more
| accessible, but then they would lose status.
|
| It seems to me that brevity is the real excuse here.
| Moreover, if it were just about symbols but papers were
| otherwise accessibly written (to reasonable extents,
| obviously), that would be different still. This is not
| the case.
|
| Appearances are probably also important for funding. I'd
| bet that if you submitted same proposal twice, once
| phrased in a convoluted way and once phrased in a "we're
| gonna blow up some material multiple times and see how
| far the shards fly" style, a number of times to
| independent funding committees, there would be a
| statistically significant correlation with which proposal
| gets funded.
| LudwigNagasena wrote:
| Why does opaque bad research form psychology, social
| sciences or paleoclimatology constantly gets media
| attention and support? I absolutely do not believe it has
| _anything_ to do with notation.
|
| And let's be real. If you couldn't understand sigma
| notation in school, the chances that you would comprehend
| complex science are very low no matter what kind of
| verbiage or, as it often would be more apt to say, verbal
| garbage it is wrapped in.
|
| I absolutely agree with you that oftentimes bad research
| is disguised with ten dollar words. And oftentimes it is
| disguised with convenient agenda (no matter how true or
| good this agenda is by itself). But I don't believe it
| has anything to do with Greek letters.
| nine_k wrote:
| Much of these formulae used to be handwritten, and still
| are handwritten at a blackboard / whiteboard in physics
| classes.
|
| It's much easier to draw a fancy symbol by hand than write
| several simple letters quickly and legibly, and it also
| takes much less space.
|
| We've been having the privilege to write using computers
| for last 20-25 years, when PCs became widespread,
| relatively cheap, and running good enough software. And
| this is outside the lecture hall settings anyway.
| Aachen wrote:
| > Much of these formulae used to be handwritten, and
| still are handwritten at a blackboard / whiteboard in
| physics classes.
|
| That is honestly the best argument I've ever heard
| (you're the first I see mention it). With as much as I
| hate writing rather than typing, I can see the point
| there actually. Maybe this practice is not as wholly
| stemming from elitism as it first seemed.
| doliveira wrote:
| Do you want to go back to writing equations with words?
| Aachen wrote:
| Just like I code in a programming language, I'm not
| proposing to turn everything into English prose. Rather,
| using (abbreviated) names for variables and perhaps a bit
| more common language in papers (but that's maybe a
| separate topic).
|
| Also I'm not sure what you mean by "back", is it
| referring to what we iirc called story exercises in Dutch
| primary school ("Jan goes to the store and buys seven
| ladders, then sells three..." etc.) or was this a thing a
| few hundred years ago or so?
| pm90 wrote:
| It's funny; when I was reading the HN comment I was just
| saying to myself "it would be so nice if the person had
| used the symbol for phi (ph) rather than spelling it
| out". So my reaction was the opposite to yours since my
| brain comprehends that notation more easily than words.
|
| Using symbols reduces the amount of text your brain has
| to parse. It makes it much easier to reach consensus on a
| shared understanding of things. The price to pay is to
| learn this new notation or language.
| doliveira wrote:
| Yeah, don't we have the mantra "less code is better code"
| or something like that? Too many verbosity and our brain
| turns off. I did type it out the Psi because I couldn't
| be bothered to type it in mobile, but yeah, it's so
| weird.
|
| Chinese people learn dozens of thousands of ideograms, I
| am pretty sure the problem with understanding the science
| has nothing to do with a few Greek symbols.
| Aachen wrote:
| We've all already paid that price for English, though.
| Why make everyone pay extra?
| pm90 wrote:
| The price that was paid for learning the language of math
| is something that everyone who needs to work with these
| things are happy to pay. If the notation doesn't make
| sense, it's discarded for ones that does.
|
| It may not make sense for layperson but that's not really
| the audience.
| mhh__ wrote:
| Writing formal mathematics as programming languages is
| basically what automated theorem provers do. The proofs
| are mostly unreadable.
|
| Mathematical notation really isn't that hard as long as
| you treat it as its own thing and learn it properly
| rather than trying to use a likely imperative model of
| computing programming as a reference point.
| doliveira wrote:
| Yeah, imagine making a calculation or transforming a
| complex formula with words and full sentences. Algebraic
| notation was a pretty big invention for a reason. For
| instance, the reason why we use single letters and
| indexes is so it's not confused with products. Try to
| write and manipulate the Schrodinger equation with words.
| Imagine solving the hydrogen atom, it already takes like
| 50 pages with algebraic notation...
|
| And I don't really understand the "I didn't do math and
| Greek in School". I barely had a foreign language, but if
| you're actually learning the concept you memorize the
| letter as well. You can't understand what a wave function
| is and then not remember that its symbol is Psi. And if
| you don't know what a wave function is, it won't help to
| write derivate_2nd_order(waveFunction, time).
|
| EDIT: obviously we're not talking about stories to teach
| newcomers, you're talking about writing equations in
| scientific articles and books with words.
| oscargrouch wrote:
| I guess its all coming down to mnemonics, aiding our
| memories and communicating.
|
| Sure this is the "state of the art", but despite the fact
| that pure language notations might be even worse, i cant
| help to think that people thinking like the parent might
| find something even better.
|
| Maybe something inspired by braille notation or something
| that is invented while trying to understand how our brain
| works (just speculating here) will be even more
| expressive.
|
| I actually like seeing an adult be bothered by the fact
| that the same symbols that turn science more expressive
| are also the reason that there's a big ladder for
| newcomers to understand whats being expressed given its
| all very arbitrary (someone in the XVI century choose a
| random greek letter to represent X).
|
| Imagine how much science would improve with more "brain
| power" being also able to try to solve some problems
| given there are less arbitrarity..
| Aachen wrote:
| > imagine making a calculation or transforming a complex
| formula with words and full sentences
|
| ... that's why I said "I'm not proposing to turn
| everything into English prose. Rather, using
| (abbreviated) names for variables"
| doliveira wrote:
| Anything other than a single letter variable with at most
| subindexes, bold, upper/lower case simply doesn't work in
| maths and science. And because we only have 26 letters,
| you do have to go to Greek.
|
| Actually, that might be a good exercise: try doing some
| moderately abstract equations with variable names such as
| you'd write in a programming language and you'll find
| yourself shortening them pretty quickly. We literally do
| it sometimes when modeling an equation for a new domain:
| we start by writing words and at the end of the
| blackboard they already became a symbol.
| enchiridion wrote:
| I disagree with the parent post about the use of Greek
| letters, but it seems like a valid point worth of
| discussion. Certainly in the spirit of HN.
|
| I've seen an increasingly worrying trend of using downvotes
| to voice disagreement, rather than as the intended purpose
| as a kind of crowd-based moderation. And before anyone
| lambasts me for complaining about downvotes, I'm
| complaining about the trend, where the above comment is
| just a exemplar.
| ajkjk wrote:
| Don't agree with this, it took a few weeks of physics
| classes to get used to using greek letters as variables,
| and without them you'd drown in re-used letters.
| Aachen wrote:
| > it took a few weeks of physics classes to get used to
| using greek letters as variables
|
| That's a very small price if you're actually involved
| with physics regularly, but HN is a relatively mainstream
| place.
|
| I had physics for 4 years in school but this wasn't part
| of the curriculum. At some point I asked why we were told
| (seemingly-to-me falsely) that there were only 3 phases
| of matter when on google videos I had seen something
| about superfluidity. The teacher made a joke about my
| stumbling over that word and then the buzzer went so...
| that's the kind of physics we had.
|
| And that's for someone who went to school in one of the
| richest (GDP per capita) and most-developed (HDI)
| countries in the world. I don't know what it's like for
| anyone tuning in from a less well-off place, or for
| someone who had physics decades ago without refreshers
| (for me it's only a bit more than one decade now).
|
| Something tells me I should have looked for a statistics
| paper that replaced GDP and HDI with some random symbol
| and used that instead. That's the kind of thing you're
| promoting and I just don't see why. TLAs aren't
| everything but they're better than single letters.
|
| > without them you'd down in re-used letters
|
| eh, literally the opposite? Using (abbreviated) names
| you'd _not_ drown in re-used letters.
| ajkjk wrote:
| well the abbreviated names include the letters, you can
| get in trouble when questions tend to have many symbols
| appended together.
|
| I should clarify, though, that I was thinking of college
| physics classes, which are definitely more mature, both
| about exploring new knowledge instead of memorizing
| facts, and about learning to actually speak in the
| experts' language.
|
| Using symbols for common concepts without defining them
| is, however, absurd. (Not counting a few -- c, e, hbar,
| m, maybe q?)
| _moof wrote:
| If you don't know what the Greek letter sigma means, you
| aren't going to know what the phrase "standard deviation"
| means, either. The notation isn't the issue. The issue is
| you can't fit stats 101 into a headline, and there's no
| getting around that.
| [deleted]
| sdfgdf wrote:
| junon wrote:
| Can someone explain this in laymen's terms?
| SpeakMouthWords wrote:
| Someone has run an experiment, and in this experiment they
| created a large amount of evidence that seems to say that quite
| an important particle in particle physics weighs something
| slightly different from what we thought it should.
|
| This is important because the weight of that particle was
| predicted by our generally-accepted theory of how the universe
| works. If the weight is different, it means the theory hasn't
| taken into account everything that it should.
| junon wrote:
| Thank you :)
| a-dub wrote:
| how much tearing apart of everything and quintuple checking goes
| on before publishing a result like this?
|
| do they stand by the result or is it more of a call for "hey,
| come have a look at this. we can't explain it."
|
| it's got to be anxiety inducing! (and exciting, of course)
| graderjs wrote:
| Scccoooopped! :P :) xx ;p
| https://news.ycombinator.com/item?id=30952630
| [deleted]
| rybosworld wrote:
| This could be an alien race interfering with our measurements.
| [deleted]
| sbelskie wrote:
| I feel like I've read that book before but can't recall what it
| was.
| sylens wrote:
| Three Body Problem
| jkhloiujlknmk wrote:
| or The Gods Themselves.
|
| Neither is great, actually. With all due respect for
| Asimov, who I love.
| aaaaaaaaaaab wrote:
| Oh no! Time to tweak the parameters of the standard model again!
| imtemplain wrote:
| Pet_Ant wrote:
| How do +-6.4 and +-6.9 combine to +-9.4 and not +-13.3 ?
| alephxyz wrote:
| The variances are additive but not the std dev. Sqrt(6.4^2 +
| 6.9^2) = 9.4
| [deleted]
| pif wrote:
| https://physics.nist.gov/cuu/Uncertainty/combination.html
| fulvioterzapi wrote:
| Errors do not sum like regular numbers. You want to take the
| square root of the sum of the squares of the errors.
|
| sqrt(6.4^2 + 6.9^2) [?] 9.4
|
| You can have a look here: http://ipl.physics.harvard.edu/wp-
| uploads/2013/03/PS3_Error_...
| stocknoob wrote:
| That PDF is great, thanks for sharing.
| [deleted]
| was_a_dev wrote:
| Can anyone explain the difference between light and heavy
| supersymmetry? Particle physics isn't quite my field
| [deleted]
| nvalis wrote:
| Some comments from an ATLAS physicist doing W mass measurements
| at the LHC:
|
| https://non-trivial-solution.blogspot.com/2022/04/do-we-have...
| slibhb wrote:
| > We observed for quite some time some features in the our
| data, which we could not explain. Once one of my PhD students
| came into my office and told that he finally figured out this
| feature: the protons in the ATLAS detector do not collide
| heads-on but under a very small angle, allowing the not
| interacting protons to continue their travel through the LHC on
| the other side of the experiment. Indeed he was right - we have
| not been considering this effect in our simulations, however -
| after some calculations and speaking to the machine experts -
| it turned out that this effect induces a feature in our data,
| which is opposite in sign that we observe; so we have been left
| with an effect that was twice as large and unexplained. In the
| end it turned out to be caused by the deformation of the ATLAS
| detector by its own weight of more than 7000 tons over time.
|
| I know these people are incredibly smart and conscientious. And
| the standard model is extremely successful and well confirmed.
| But that's a lot of degrees of freedom.
| beezle wrote:
| Waiting to see if Tammaso puts something up about it, IIRC he
| was a CDF member
|
| https://www.science20.com/quantum_diaries_survivor
| cshimmin wrote:
| As another ATLAS physicist, I can say that this is an excellent
| article from Prof. Schott. He is very politely arguing that
| "someone messed up". I'm not sure I agree so much with the
| point of combining the LEP experiments, which do have some
| tension with each other. Unless the combination is specifically
| taking into account correlations between uncertainties at the
| different experiments on the same collider (which exist, but
| it's really hard to handle).
|
| Another take many people in the field are expressing is that
| it's simply infeasible to reliably interpret statistical models
| at that level (especially one that is dominated by systematic
| uncertainty), since they are based on approximations and
| assumptions e.g. that certain nuisance parameters are "nicely"
| distributed and uncorrelated. See e.g. comments from Prof.
| Cranmer [1] who is one of the folks who developed the standard
| statistical formalism and methods used in modern particle
| physics experiments.
|
| [1]
| https://twitter.com/kylecranmer/status/1512222463094140937?s...
| spekcular wrote:
| Why don't people use nonparametric methods to get around the
| problem of assuming certain parameters are "nicely"
| distributed? (Not a physicist, but curious - this seems like
| the "obvious" solution.)
| nabla9 wrote:
| Nonparametric methods are often used when the assumptions
| of parametric tests don't hold.
|
| In physics experiments they want to fix the structure of
| the model and know the assumptions. They want to know the
| distribution and parameters to hold. If assumptions don't
| hold, they must find out why, find better assumptions and
| fix the model.
|
| To say it differently: physicists are not trying to
| discover statistical laws. They are trying to discover
| physical laws trough statistics.
| spekcular wrote:
| It sounds like they know certain assumptions regarding
| parameters that are not of interest are wrong. So why
| explicitly model those, if we don't care about their
| distribution? We (apparently) only care about an accurate
| estimate of W boson mass.
| nabla9 wrote:
| That works if the thing is something you can remove from
| the experiment and model separately, then put it back. In
| CERN many variables are tied to this one huge machine
| that is one of its kind.
| spekcular wrote:
| I admit I'm not familiar with the model used to aggregate
| the boson data. But there's an entire community of
| nonparametric/semiparametric statisticians that works on
| problems just like this. It seems crazy to me that that
| millions of dollars are spent to build the machines to
| collect this data, yet the papers are written using
| statistical models with distributional/independence
| assumptions known to be false. (The tweet linked above
| seems to be saying something similar.)
|
| Is there a concrete reason we can't be naive and just
| bootstrap confidence intervals for example? Of course I
| defer to the physicists here - but I'm curious whether
| there's some simple high-level reason the usual tricks
| don't work.
| lazide wrote:
| Because it's all interrelated and too many variables make
| it impossible to nail down anything with certainty if you
| don't assume some invariants somewhere?
| Certhas wrote:
| "I do not think, we have to discuss which new physics could
| explain the discrepancy between CDF and the Standard Model - we
| first have to understand, why the CDF measurement is in strong
| tension with all others."
|
| That's... cute. I doubt it will stop the theorists from
| flooding the arxiv with explanaitions in the coming days/weeks.
| Recall what happened when there was a barely 3 sigma (local)
| statistical fluctuation in LHC data:
|
| https://resonaances.blogspot.com/2016/06/game-of-thrones-750...
|
| Edit: Thank you for posting the excellent article!
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