The various standard kilograms held by the national bodies, and the prototype standard kilogram in paris, were measured very precisely over the past hundred years, and their weights did seem to diverge mysteriously.

What made them mysterious? Aren't there always some fraction of atoms or molecules with sufficiently high energy to escape the object?

The fact that you, a random internet guy, knows this makes me believe that the world's top experts on measuring this exact thing probably thought of it, and if there is a mysterious divergence this probably doesn't account for it.

I figure as much, but that's kinda why I'm asking what made it mysterious. I actually hadn't heard of it being seen as mysterious until today - that comment is the first time I've seen that. Until today I thought it had been was unsurprising for scientists.

> I figure as much, but that's kinda why I'm asking what made it mysterious.

You expect simple explanations to VERY complex problems from random internet commenters. I think you expect too much.

Not on HN sometimes some gems of comments are made by experts

Sometimes: when you least expect them. Not expecting them is a good strategy here.

I think the real question is: where is the evidence that scientists find it mysterious? That doesn't need any sort of explanation, just a reference for a claim made by a commenter. As with the other commenter, I've heard about the mass divergence before, but never that anyone found it surprising.

As has even been discussed on HN over the years (!), the cause is unknown.* This is one of the motivations to replace the official kilogram with a definition based on measurable natural quantities, as had been done with the second and the meter. It took until 2018 to do so: https://www.nist.gov/si-redefinition/kilogram-introduction

* it’s not like there aren’t good theories but you can’t experiment directly on “the” kg because you can’t risk changing it!

I'm neither seeing the cause being mentioned as unknown in that link, nor would the cause being unknown imply anything being mysterious?

Like if you find that your car has broken down after 200k miles, you might not be able to determine the cause, but it wouldn't exactly be some kind of mysterious physical phenomenon that would puzzle scientists. Obviously, something wore out. Why/how is this any different?

Did you click on the other kilogram links (or other metric links which are also interesting?)

A useful paragraph is the following: "The trend during the past century had been for most of BIPM's official copies to gain mass relative to the IPK, although by somewhat different amounts, averaging around 50 micrograms (millionths of a gram) over 100 years. But an alternative explanation is that the IPK was losing mass relative to its copies. Even more likely, it was a combination of both."

Those pages are for the lay audience but you can do your own web search (probably even an algolia search of HN) to know more.

In general, it's often easy to come up with an explanation of some new phenomenon, but to answer the question you still have to do science...which often simply confirms intuition but not always. My comment was less on the reason and more on the difficulty of doing experiments on what was literally the kg, no matter how it fluctuated.

My theory: People are treating them with different degrees of reverence. They are careful to polish anything off the IPK, causing it to lose weight gradually through abrasion. The others gain wait through random adhesions, perhaps oils picked up by gloves used to handle them.

I'm just some random guy on the internet, I know. It's fun to have theories!

I don't disagree with you, but on the other hand: if people claim something in a discussion thread we need to be able to ask them to back those claims up. Otherwise anyone can just assert anything.

Sure, the explanation might not fit in the margins here, but then a link to a source that does attempt to explain it would be fine too.

One reason why questions like this are important is because it gives the audience around the asker an opportunity to learn something new. Isn't it important to be able to express curiosity, especially for the benefit of others?

50 ug over 130 years is way too fast

> The reason for this drift has eluded physicists who have dedicated their careers to the SI unit of mass. No plausible mechanism has been proposed to explain either a steady decrease in the mass of the IPK, or an increase in that of its replicas dispersed throughout the world

https://en.m.wikipedia.org/wiki/International_Prototype_of_t...

I find that it saves time to just start by assuming the experts haven't thought of X because of how many times I've seen assuming that they _have_ thought of X turn out to be a poor assumption, across many domains.

That’s incredibly specious reasoning.

Probably gets a better result than the alternative though. ;)

Can you give any examples of times you’ve easily anticipated X when a whole field of subject matter experts have demonstrably overlooked it?

Can't speak for OP, but I've had more than a few similar experiences (from both sides of the fence FWIW).

I can think of one example in software deployment frequency. The observation (many years ago), was that it's painful and risky (therefore, expensive) to deploy software, so we should do it as infrequently as the market will allow.

Many companies used to be on annual release schedules, some even longer. Many organizations still resist deploying software more than every couple/few weeks.

~15 years ago, I was working alongside the other (obviously ignorant) people who believed that when something is painful, slow and repetitive, it should be automated. We believed that software deployment should happen continuously as a total non-event.

I've had to debate this subject with "experts" over and over and over again, and I've never met a single person who, once migrated, wanted to go back to the nightmare of slow, periodic software deployments.

I don't see why a slow deployment cadence is a nightmare. When I've worked in that setting, it mostly didn't matter to me when something got deployed. When it did (e.g. because something was broken), we had a process in place to deploy only high priority fixes between normal releases.

Computers mostly just continue to work when you don't change anything, so that meant after the first week or so after a release, the chance of getting paged dropped dramatically for 3 months.

Good question. The nightmare was mostly organizational.

The amount of politicking was incredible when it came to which features would be in the next push and which features would slip. The planning meetings, the arguments, the capability slashing, the instability that came from all these political decisions. It was not great and this enormous amount of churn literally disappeared when they moved to daily pushes.

That's more "the experts had a (wrong) opinion on something" than "the experts overlooked something obvious". They didn't overlook it, they thought about it and came to a conclusion.

And if by "many years ago" you refer to a period where software deployment was mostly offline and through physical media, then it was indeed painful and risky (and therefore expensive). The experts weren't wrong back then.

Great points, I agree with you.

I don't really agree with the OP, but I do think there is at least one, possibly two such examples. The pretty clear one is nutrition: the vast majority of studies and recommendations made over the years are pure bullshit, and quite transparently so. They either study a handful of people in detail, or a huge swathe of population in aggregate, and get so many confounding variables that there is 0 explanatory power in any of them. This is quite obvious to anyone, but the field keeps churning out papers and making official recommendations as if they know anything more about nutrition than "missing certain key nutrients can cause certain disease, like scurvy for missing vitamin C".

Is that an example of "the experts didn't actually think of [simple explanation]" though?

Nutrition in particular is a scenario where major corporations willfully hid research about sugar and things for years and years and funded research attacking fat content instead, which turns out is actually pretty benign. Perfect example.

This isn't to agree with the parent comment, but wouldn't this situation itself be an answer to your question (assuming the claim is true)? Laymen like me easily anticipated mass divergence, but purportedly scientists have been surprised by it.

The procedure of multiple weights being calibrated against a single standard is _predicated_ on anticipated mass divergence.

The mystery being discussed is that, even after the obvious sources of error are allowed for, there is still a discrepancy, and it's not easy to determine how much of that discrepancy is with the weights being recalibrated vs the test standard they're being calibrated to. None of which is shocking to anyone involved, just puzzling.

This comment chain is getting circular. We can't use this as an example for itself by assuming that it is true.

I think that they do not have an exact reason and measured it and seen it happen is the surprising bit. Anything else is a good guess. Of those, people have plenty.

* [insert every example of "15 year old unknown vulnerability in X found" here]

* have to be a bit vague here, but while working as a research scientist for the US Department of Defense I regularly witnessed and occasionally took part in scenarios where a radical idea turned "expert advice" on its head, or some applied thing completely contradicted established theoretical models in a novel or interesting way. Consistently, the barrier to such advancements was always "experts" telling you that your thing should not / could not work, blocking your efforts, withholding funding, etc., only to be proven wrong. Far too many experts care more about maintaining the status quo than actually advancing the field, and a concerning number are actually on the payroll of various corporations or private interests to actively prevent such advancements.

* over the last 30 years in the AI field, there have been a few major inflection points, Yann LeCun's convolutional neural networks and his more general idea that ANNs stood to gain something by loosely mimicking the complexity of the human brain, for which he was originally ridiculed and largely ignored by the scientific community until convolution revolutionized computer vision; and the rise of large language models, which came out of a whole branch of AI research that had been disregarded for decades and was definitely not seen as a thing that might ever come close to something like AGI, natural language processing.

* going back further in history there are plenty of examples, like quantum mechanics turning the relativistic model on its head, Galileo, etc etc. The common theme is a bunch of conservative, self-described experts scoffing at something that ends up completely redefining their field and making them ultimately look pretty silly and petty. This happens so frequently in history that I think it should just be assumed at all times in all fields, as this dynamic is one of the few true constants throughout history. No one is an expert, no one has perfect knowledge of everything, and the next big advancement will be something that contradicts conventional wisdom.

Admittedly, I derived these beliefs from some of the Socratic teachings I received very early in life, around 6th grade or so back in the late 90s, but they have continually borne fruit for me. Question everything. When debugging, question your most basic assumptions first., "is it plugged in?" etc, etc

It's sort of at a point these days where if you want to find a fruitful research idea, probably best to just browse through conventional wisdom on your topic and question the most fundamental assumptions until you find something fishy.

I missed this comment first time around, but I really appreciate this write-up.

I apologize for being a bit snide in my original challenge, I'm fairly sensitive to the "why don't you just" attitude, but I agree with pretty much everything you have to say here.

I have a very similar approach around enumerating and testing assumptions when the going gets tough, and similarly have found that has enabled me to solve a handful of problems previously claimed impossible.

I think the tautological issue with our initial framing is that if you're able to easily identify these problems you probably are a subject matter expert. In many ways it's the outsider art of analytical problem solving - established wisdom should not be sacred.

I've heard of an appeal to authority, but an appeal to ignorance is new.

OPs question is not ridiculous, nor does he suggest it to counter the "mysterious" claims

Not new, Efficient Markets Hypothesis is like this. "I haven't heard of a way to make money from trading so there isn't one" is my caricature of it.

Isn't it more like: "exploitation of a market inefficiency renders the market efficient over time", or something to that effect? Or rather, (others) making money from trading is what makes it hard (for you) to make money from trading.

Sure, depends on how you encounter it. Most often on forums someone will show up wanting to hear about how to write a strategy, and they are rebuffed with "nobody would ever publish that".

I love encountering nay-sayers because it means either:

1. I am wrong and could learn something new.

2. They are wrong and their opposition fills me with defiant determination.

The difficulty comes when you view something as case 2 but it is actually case 1 and you embarrass yourself. I do this all the time.

They're not being arrogant, as it seems like the parent is genuinely curious as to why such weights diverged, as am I. It is still a good question to ask, since I also have not heard a good answer to that question.

Right -- and they're not even asking for the answer, they're just asking what the interesting mysterious phenomenon is.

Did you ever pause to think "is this comment worth posting"? Maybe you should.

Can they perform the calculations to estimate the fluctuations? Can they write an informal explanation about what happens to the gluons? I think the experience of seeing a factoid on the internet is being given too much weight here.

> Aren't there always some fraction of atoms or molecules with sufficiently high energy to escape the object?

Can someone help me understand this? I thought that things were supposed to be stable given the elements used for le grand k. That they don't decay on their own and it would have to be another mechanism to explain the divergence?

[0] https://en.wikipedia.org/wiki/International_Prototype_of_the...

In a system of particles, due to random Brownian motion and the nature of Gaussian energy distributions, a small number of particles occasionally gain significantly higher energy than average through statistical fluctuations. Maybe enough to escape the binding energy of le grand k. However I would think this is a very very small effect in platinum.

Sure, radioactivity.

But, Le grand K is made of naturally occurring platinum of which most of the isotopes are observationally stable[0] and the one isotope that isn't has a half-life of 6.5×10^11 and only makes up 0.012% [1].

So yeah I don't buy the unstable explanation to even begin to show the divergence, let alone "weight gain".

[0] https://en.wikipedia.org/wiki/Stable_nuclide#Still-unobserve...

[1] https://en.wikipedia.org/wiki/Isotopes_of_platinum

[Edit] Wait are you describing evaporation?

Yes, he's describing evaporation. Here's a thread about it, basically the answer is "we don't know" https://physics.stackexchange.com/questions/77130/why-does-p...

Thank you, that link (particularly [1]) is basically the kind of explanation I was looking for in my initial comment.

[1] https://physics.stackexchange.com/a/784886

There's so many variables there! What kind of purity could 1889 achieve? What kind of uniformity between the N samples? How do they know the different cleaning procedures (!) are not adding mass by leaving something behind? If the samples are known to be oxidizing, why leave them in air? Why are there multiple elbows in that graph around 1950 -- surely another procedural change but again not uniformly applied?

Maybe these aren't the best sources of historic mass data.

Edit: yes

Perhaps you mean Boltzmann distributions?

If it were simply a matter of losing particles, I'd expect that one of the many very capable metrology labs around the world would've devised an appropriate experiment, e.g. storing two exact same masses at slightly different temperatures near absolute zero and characterizing the difference in mass (since presumably the higher temperature sample would lose slightly more mass if it were down to high energy particles).

A test for this theory would have to involve a means of accounting for these kinds of fluctuations.

I mean I just gave one example of how it might lose mass. There are other obvious ways (like when they're picked up etc.). My point wasn't to present a hypothesis for people like myself here to rebut. I can do that just fine myself. I was trying to understand what about this has been confusing for scientists.

> like when they're picked up etc.

Wouldn’t just moving an object change its mass? Any change in potential energy would mean a change in mass from good old e=mc^2

Make sure to store them very deep underground down a mineshaft, so random cosmic rays don't ever knock a few atoms loose.

Look for material condensed on the inside of the jar.

It's well known that they tend to gain weight, not lose it.

And yeah, the mystery is just what mechanism exactly affected each one. (AKA, not much of a mystery.) The possibilities are very well understood.

> And yeah, the mystery is just what mechanism exactly affected each one. (AKA, not much of a mystery.) The possibilities are very well understood.

Ahh, that makes more sense. Thanks!

If the object is evaporating, look for material condensed on the inside of the jar.

I'm sure that if they suspected that variance in mass could support their theory, they would have investigated that possibility instead of proposing a new test.

If I understand correctly this theory would manifest itself as variation in measuring the same standard kilogram over and over (to a precision beyond what we are currently capable of), whereas divergence between different standard kilograms could have other unrelated causes.

(We detached this subthread from https://news.ycombinator.com/item?id=38527238.)

Yeah, since untestable proposals for this kind of theory are basically the norm, the fact that they have a proposed test made me think it was worth sharing.

It's good that it's testable. This is one of those ideas which either wins a Nobel Prize or is totally bogus. So what does it take to test it?

Bogus usually implies something meant as a fake or counterfeit, I think a better way to describe it would be "incorrect", I don't think these scientists are trying to fake anything.

Untestable theories are not theories - I mean, for what purpose and why care?

The other big theories aren't completely untestable, the issue is basically that the models have a lot of parameters which can often be tuned in a way that leaves a possibility for the general theory to still work, and testing them to the point that any corrections seem too unreasonable is even more difficult and expensive.

Path finding

Not reflecting to this particular theory, but in general history is full of theories which were not testable at their birth, but both engineering and the evolution of the theory eventually found a way to do so, even if it took a century.

Black holes, Higgs bozon and neutrinos are a few popular examples.

Some theories are only untestable for practical reasons, like needing a particle accelerator the size of the solar system. That doesn't make them unscientific or "not theories". That is not the kind of falsifiability that Karl Popper had in mind.

Yes, it does. The word "theory" has a specific meaning. What this article is about is really a hypothesis, not a theory. I saw no evidence or data to back up what they think might be happening, thus not a theory.

"In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data."

Most people in this thread, as well as the writers of the article seem to be confused about the meaning of the word theory.

Maybe that should give you a hint that professional working scientists don't care much for definitions from wordbooks.

Besides, I was commenting on the topic of falsifiability. To be a scientific hypothesis or theory it must be falsifiable - in principle, not practically. At least that's my claim in the context of Popper. Evidence didn't even enter the discussion.

Do you have any examples? I‘d to read up!

This guy is exploring ultra large colliders:

https://arxiv.org/abs/2106.02048

> The CCM will be an important stepping stone toward an ultimate Planck- scale collider, with a centre-of-mass energy of ∼10^16 TeV, that would require a minimum size equal to a tenth of the distance from Earth to Sun.

Yeah they are, they just cannot be verified - or cannot be verified yet.

The higgs boson theory was theorised in 1964 and it was untestable at the time, but that theory got the funding together to create one of the largest and most expensive scientific instruments built to prove the theory.

Nuclear fusion was theorised in 1915, again untestable at the time, and look how far we've come.

The above comment is an anti-science comment if I've ever seen one.

Usually when people say something is untestable they don't mean like the Higgs Boson. It was testable, they just needed the proper tools. This was always known and was being actively worked towards. An untestable theory is one that cannot be tested regardless of the tools due to the nature of the theory. Multiverse is an example of an untestable theory. There is no way we know of to actually prove or disprove it. And its fair to question their legitimacy as theories. As testing a hypothesis is the core action of the scientific method, it logically follows that anything untestable is fundamentally not science and therefore not a theory.

Isn't the term for this "unfalsifiable"?

A theory can be untestable but also falsifiable. For example, while the multiverse theory/interpretation may be untestable, it could be immediately falsified if QM were falsified.

Popper's falsifiability criterion was more aimed at theories like Marxism, where it seemed that within the theory there was always something available to account for an exception or challenge.

In this case I think multiverse is both. Testability and falsifiability are closely related. But its possible to make a testable statement that can't be falsified in most examples I can think of the test can't be exhaustive.

> it's really nice to see the proponents proposing a test.

Is it feasible though? I wonder whether that test is not just outside of what can be technically realized today, but Heisenberg's uncertainty principle gets in the way.

Well,... measuring gravity waves was outside of the technically realisable for a long time, but a couple of decades of trial and refinement and it got realised.

Love that there is a test.

Some of the theories like gravity waves and Higgs boson took almost half a century to be confirmed by experimentation.

The hard part about this is building tools that can precisely measure mass fluctuations with extremely low error bars at picosecond timescales.

Because we need to both validate the theory and that the device is correctly measuring.

So much of science became only possible because of better instruments. Be it microscopes to see the tiniest phenomena or telescopes to observe the furthest phenomena.

I’m not a physicist much less an astrophysicist and so take what I’m about to say with a hefty grain of salt. But I wonder if this new approach can also explain observations of distant galaxies. Distant galaxies either redshift because they’re moving away faster over time due to dark energy or redshift because their mass is changing. Can this new theory help explain why older galaxies might lose increasing mass over time?

>redshift because their mass is changing.

Why would that cause red shift?

Losing energy shifts the frequency of your emissions towards red.

Basically, cooling down is the same thing as moving farther away from an inertial reference point.

Are you thinking of thermal radiation? And what does losing mass have to do with cooling down?

We observe redshift in the spectrum. Hydrogen emits radiation in very specific frequencies, which are redshifted. This cannot be explained by losing mass, heat or energy.

I thougt the red shift is due to Doppler effect and the universe expansion (planets are running away from any observer in the universe)

> So much of science became only possible because of better instruments.

I would argue a stronger claim: experimental confirmation of theories and better measurements must always bootstrap each other. The history of temperature has many examples [1].

[1] https://psychology.okstate.edu/faculty/jgrice/psyc4333/Therm...

Surely someone has at some point come up with a theory that was testable with then-current equipment.