The Origin of Mass (2003) [pdf] | Hacker News Reader

The Origin of Mass (2003) [pdf]

web.mit.edu

87 pointslainon28 comments

> it derives m=E/c², not E=mc². Einstein was thinking about fundamental physics, not bombs.

Although I know the E=mc² formulation makes more sense from an "E²=(pc)²+(mc²)²" point of view, the author had a kind of striking way to put their point. It's as if the war managed to intertwine itself in culture so strongly it twisted the perception of the entire general public on issues of fundamental physics!

F=ma was originally a=F/m. Although the former seemed more useful at the time the latter nowadays is more intuitive.

The bomb shaped culture and physics, sure, but rewriting equations into more useful and intuitive forms isn't a new or uncommon phenomenon.

Yeah, I think it's inherently more striking to think about mass "becoming" energy, or the "energy content" of mass, than about the converse. Imagining energy "condensing" into mass is wild, but we spend a lot more time around mass qua mass than around pure energy.

> Finally, the most basic feature of mass in classical mechanics is that it is conserved. For example, when you bring together two bodies, the total mass is just the sum of the individual masses. This assumption is so deeply ingrained that it was not even explicitly formulated as a law. (Though I teach it as Newton’s Zeroth Law.)

The author may wish to check [1] for historical reference.

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

The author is a Nobel laureate in Physics.

So what's wrong with Lavoisier being credited with the Law of Conservation of Mass? He is famous enough for it that I, having no formal training in physics, am aware of him discovering it independently.

The author may be right (or wrong) but he is not right or wrong due to whatever epaulletes he is wearing on his uniform. It does signal he is likely right, but in that case we should point to the reason and not just point to at the epaulettes.

Nothing, other than the fact the author is not talking about Lavoisier's law and that it's more than a little presumptuous to be telling someone who teaches physics at MIT, beside collecting a Nobel prize, that they might wish to check Wikipedia (ceremoniously [1]-footnoting it, in two lines of text) for the historical perspective they might lack.

Yes of course the author can be wrong about something - the comment isn't pointing out anything wrong, just sententiously insinuating he is uninformed.

Then you can enlighten us because as far as we can tell what we think you are saying is the author's discussion of conservation of mass has nothing to do with the Law of Conservation of Mass (as opposed to some mystic qualities of matter believed prior to the discovery of this law of nature--in classical physics). Don't just point to the epaulettes and tell him to be respectful--it's ok to question authority (granted it was done a little bit presumptiously, you are right there, but I'd recommend letting it go--be the bigger person and be the teacher).

I'm not 'pointing to epaulettes. I am pointing out the silly and unwarranted assumption Frank Wilczek is unaware of the basic, Wikipedia-page-level history of the science in question. I think it's obvious and a given that he is. If you don't think that's the case, fair enough but it's up to you to find some concrete way to support that rather odd view - it's not for me to refute it from first principles.

We're not asking you to defend this physicist. There's an obviously confusing bit about conservation of mass here, which lead to the user citing the Law of Conservation of Mass, that I already asked about, and which you are now ignoring. That's the thing to focus on, not on Frank Wilczek. We already know the poster (unwittingly) was a bit presumptious, but in my opinion I think it would be better to focus on the ideas and let the presumptiousness just slide.

What's the confusing bit?

What's remarkable about conservation of mass in the author's example that's not already formulized in the Law of Conservation of Mass?

Which law? You mentioned Lavoisier and I think someone else already covered this well. It's hard to figure out what your question is from your strident defense of 'someone is being an ass on messageboards'.

I think you're taking taking it personally, and beginning to use inflammatory language.

I think you are thinking emotionally about this and that is why you are misinterpreting my thoughts.

Wiczek himself thinks it's an unintuitive notion to question such an assumpion.

Yes the poster didn't pose it as a question. We already agree that is presumptious, and a mistake. Where we disagree is the bigger mistake is in not explaining the poster's confusion.

I don't think you or anyone is being an "ass." Let's take a cooling off period from this so we don't get upset over some small disagreement on the value of deferring to faith in authority.

What is the thing you found confusing that you wanted to ask about. I'm not in the slightest bit upset to think someone is being an ass. Or, as in your case, a condescending twit. I'm just curious about this supposed question.

You don't need to use offensive language, or call me a condescending twit. That's out of order.

The question is stated more than once in this thread and has already been adressed by others--this much you have even said yourself.

Calm down.

I tend to give the benefit of the doubt to experts in such situations. While I too thought of the Law of Conservation of Mass and wondered why the author didn't think of it I also know this means that most likely it is I who is lacking knowledge in this case. It is highly unlikely that I know something about mass that an expert doesn't know. Rather than linking to Wikipedia the question ought to have been asked, "what does he mean when he writes this?" Instead amelius says he should read Wikipedia.

Let's not pretend that our superficial understanding matches the expert's understanding or that we can teach him something new by citing Wikipedia. If we can think of a point that the author seemingly misses it is almost surely because we are the ones not understanding something.

We actually don't disagree here; at least not on the points you listed. It appears you are misunderstanding what I'm trying to say.

While we both agree it is reasonable to give the benefit of the doubt to experts, and it wasn't good to be a bit presumptiois either, the issue is that we should still never answer by just pointing to the epaulettes of the expert--especially in this case where there is an obvious confusion.

I don't believe this physicist would be offended by Amelius' post, and if an authority was offended by such a minor transgression and first unwilling to provide an explanation--as was the case here--and sought to assert authority instead of through explanation and through epaulettes, we should further question that authority, always.

We could next time just say: 'here is why you are confused, and you should have wondered why if you happened to notice the writer's accomplishment.'

The poster never said they were confused. They implied the author was confused. You seem really keen on berating others about 'epaulettes' while taking it on faith the poster was actually asking a question, rather than being a butthead.

There is no evidence of that whatsoever. How on earth is anyone supposed to figure out what question is being asked in the in the intricate disguise of being a butthead?

Judging by language used, no one is berating anyone but you.

We agree the poster was presumptious, but you ignore the other point where we disagree (other than that the poster should be scolded) and keep focusing on a point we already agree on.

Where we disagree: I just dont think one should point and say 'they're the expert, not you' when you can say 'you are misunderstanding for this reason.'

I think it's a very valid criticism.

Your method has the ingredients necessary for why people followed mystics and religious leaders before The Enlightenment and Age of Reason.

When Feynman defined science, he famously said: "it doesn't matter what you're name is."

The key words are "in classical mechanics." Nobody wondered whether the mass of two stacked bricks was equal to the sum of the masses of the individual bricks. On the other hand, burning cloth seems to "leave behind" a lot less than you started with. Lavoisier's contribution was to demonstrate that even in chemical reactions, with shocking changes in color, state of matter, etc, mass was conserved.

Wilczek is discussing the ingrained assumption about the bricks.

We're familiar with Lavoisier's Law.

So when you are suggesting CM, many of us probably know that Lavoisier's Law would show small errors at high energy states in CM... But then your explanation offers some perspective on Lavoisier's Law... So what are you suggesting with your key word?

In the context of chemistry, conservation of mass is not at all obvious which is why it is a big deal that Lavoisier proved it to be the case. To determine that burning wood into ash (for instance) doesn't change the total mass of the system requires precise measurement and an intuitive leap on what constitute the boundaries of the system.

In mechanics there is historically no such law precisely because no-one would ever have thought that it wasn't obviously true.

Yes I am aware. The issue is that in our current understanding we now know in chemistry we are adding element1+element2=element1+element2... (classically at least).

So while Lavoisier led us to the above, the author is pointing to the fact that e1+e2=e1+e2 but to the reader this can be confusing because Lavoisier's Law also states the same... Though once you understand that you are just rearranging chemical bonds b/w elements there's nothing different about it.

I don't have any intuition about how you would theoretically prove the assumption in Lavoisier's Law--Newton's 0th Law. It seems if Lavoisier's Law is true it implies Newton's 0 must also, at least intuitively...

It's a reasonable source of confusion and I think it's ok the above poster was misguided about it as everyone agrees from the start on this: almost no one questioned such an assumption.

That is the superposition principle for scalars.

That was a very understandable outline of the basic concepts... well written and almost convinces me that I could step off the end of the Theoretical Minimum math and into further QM.

Oh my.

Interesting that he doesn't mention the Higgs.

Should add [2003] to the title.

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