Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: varsigma on 29/04/2022 10:00:40
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This idea is being promoted at another site. I can't make much sense of it.
But I'm wondering if it's true does that mean there's a proof? Isn't it relatively straightforward to prove a number exists?
Or is there a way to prove mass isn't a number? Or do you just accept mass occupies a volume, the same volume some matter is in and forget about proving it?
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Or is there a way to prove mass isn't a number?
Which number?
Is my mass 71 or 156.5?
Depends if you are talking kilos or pounds.
So, no, mass is plainly not a number.
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Most physical quantities require Units (there are a few exceptions, like the fine-structure constant, and some percentages and ratios)
- It turns out that mass is one quantity that has units, and they are the kilogram in the metric system
- In contrast, the original UK pound was a measure of weight, which has different units
So when you specify a Mass or a Weight, you need a number and the units.
- Eg 71 Kg or 156.5 lb
On a periodic table, you will see an Atomic Mass number written without units
- Partly because the periodic table is already pretty crowded
- If you look up a textbook or Wikipedia, you will find that the units are:
The Dalton or unified atomic mass unit (symbols: Da or u) is a unit of mass widely used in physics and chemistry. It is defined as 1⁄12 of the mass of an unbound neutral atom of carbon-12
So it is a ratio of the mass of a particular atom when compared as a ratio to the mass of a Carbon-12 atom; as a ratio of two numbers with the same units, it is legitimate to say that the atomic mass unit is dimensionless, and can be specified as just a number.
- You had better make it very clear from the context what this number represents, so it is clear that it is Daltons, and not a count of atoms, kg, moles, micrograms, or the number of days before Christmas
- However, if you want it in absolute terms, 1 u = 1 Da = 1.66053906660×10−27 kg
https://en.wikipedia.org/wiki/Dalton_(unit) (https://en.wikipedia.org/wiki/Dalton_(unit))
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Hi all,
OK varsigma,
If I understand your request correctly regarding is mass a number rather than a physical thing.
Its based on empirically proven physical constants, to allow precise replication.
So the unit of mass is the Kg Kilogram in the system of international units, which was originally simply the mass of a litre of water, which is actually accurate to 30 parts per million.
However in 1799, it was replaced by an all-platinum kilogram prototype that was fabricated with the objective that it would equal, as close as was scientifically feasible for the day, the mass of one cubic decimetre of water at 4 °C. It was called the Kilogramme des Archives as it was stored in the Archives Nationales in Paris.
This remained the SI standard till 2019.
https://en.wikipedia.org/wiki/International_System_of_Units
The kilogram was the last of the SI units to be defined by a physical artifact, although precision kilogram masses remain in use as secondary standards for ordinary purposes.
https://en.wikipedia.org/wiki/Kilogram#Redefinition_based_on_fundamental_constants
The requirement to produce replicas caused the mass of these to vary by amounts approximately 50 micro grams.
Therefore,
The International Committee for Weights and Measures (CIPM) approved a redefinition of the SI base units in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.62607015×10−34 kg⋅m2⋅s−1, effectively defining the kilogram in terms of the SI base units "second" and the "metre".
Therefore, dimensions of energy times time, (mass × length^2 / time) together with other physical constants
This was done so that the standard can be independently reproduced in different laboratories by following a written specification, from empirically proven physical constants.
And the units were coherent to mass length and time.
https://en.wikipedia.org/wiki/Kilogram#Acceptance_of_the_Giorgi_system,_leading_to_the_MKSA_system_and_the_SI
To summarize, the ultimate reason that the kilogram was chosen over the gram as the base unit of mass was, in one word, the volt-ampere. Namely, the combination of the meter and the kilogram was the only choice of base units of length and mass such that 1. the volt-ampere—which is also called the watt and which is the unit of power in the practical system of electrical units—is coherent, 2. the base units of length and mass are decimal multiples or submultiples of the meter and the gram, and 3. the base units of length and mass have convenient sizes.
It would appear the Kibble balance is the dominate apparatus in this regard.
https://en.wikipedia.org/wiki/Kibble_balance
which hopefully the design/engineering explains to you how mass is not just a number but a based on combination of physical constants allows a very accurate replication of fixed amount of Mass.
A conducting wire of length L that carries an electric current I perpendicular to a magnetic field of strength B experiences a Lorentz force equal to the product of these variables. In the Kibble balance, the current is varied so that this force counteracts the weight w of a mass m to be measured. This principle is derived from the ampere balance. w is given by the mass m multiplied by the local gravitational acceleration g
weight = mg = BLI
https://en.wikipedia.org/wiki/Lorentz_force
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Thanks for the replies.
The "mass is a number" argument is ongoing.
I don't know how to argue against it. My understanding of what it is is that it's physical and all matter "has" mass.
If it was just a number why do we give it units of kg? Why is 1 kg a number? What does the "mass is a number" principle tell us about physics?
Why bother trying to argue its validity or usefulness, or prove it isn't true?
This is the latest version of this person's thinking:Objects have inertia because they are made out of matter, not because they "have mass". Mass is a property that quantifies inertia, but it doesn't cause inertia. How could a concept cause something physical?
Nah . . . that just isn't right is it? It seems this person is confused about what physical means. I should just give up trying to understand them, right?
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Why is 1 kg a number?
It isn't.
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Mass is a property that quantifies inertia
Mass has two quite different impacts:
- It is related to inertia through Newton's F=ma (Force = Mass x Acceleration; inertia is the amount of Force you need to get something moving)
- It is related to gravity through F=mg (Force = Mass x "Gravity"; A greater Mass has a greater gravitational attraction, all other things being equal.)
- It was a bit of a mystery why these two different methods should come up with exactly the same number of kg, regardless of what material you were measuring
Einstein, in his General Theory of Relativity, created the Equivalence Principle that says that inertial and gravitational mass are always the same.
- As usual, you need to be a bit more careful when you come to massless particles like photons
See: https://en.wikipedia.org/wiki/Equivalence_principle
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Mass is the quantity of stuff in an object, so for any object it is a number multiplied by a unit of quantity.
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This thinking, at what used to be a science site but is now I don't know what exactly, is extended to the electron like this:
Electrons are real particles, but their mass is a concept, invented by humans. The electron's charge is a concept and so is the spin.
Yeah, really.
There's a thing called realism, in physics, which asserts that a real universe exists whether or not observers exist, who then construct theories to explain their observations. I don't need to look at the moon to make it exist.
But I don't know how a theory that says it's all conceptual, actually fits in there. I don't think it does, because an experiment involves measurements; ultimately wouldn't that mean you have to define distances as conceptual--a metre of distance is also a concept? It seems a bit woolly.
Nobody else is challenging this person at this site; I've given up.
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Electrons are real particles, but their mass is a concept, invented by humans.
Mass was conserved before humans evolved.
The electron's charge is
If the electron didn't have a charge chemistry wouldn't happen (nor would lots of other things but...)
And without chemistry, there's no biology.
So we know that electrons had charge before humans had any concepts at all.
Even if you want to make the slightly insane leap that mas iis a concept then you still have to recognise that it's a different category of concept from a number.
So they can't be the same thing.
Nobody else is challenging this person at this site; I've given up.
The person getting challenged is you- because you keep saying things that are wrong.
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The person getting challenged is you- because you keep saying things that are wrong.
What things am I saying that are wrong? Please explain.
I haven't said mass is a number; I haven't said mass is a concept. I haven't said charge and spin are concepts. I haven't said a field is a concept. That's what someone else is saying.
I'm not saying it. So what am I saying that's wrong?
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That is the principle of realism, and the only way it can be true is if one accepts superluminal causality. Physics isn't so classical as you'd like it to be.
Well, sorry, but that doesn't say much about whether observers are needed so that "reality" exists.
It doesn't say much either, about measuring a real distance, or a real interval of time. These are both fundamental physical quantities, I challenge anyone to devise an experiment which doesn't measure both of these in some direct way.
Usually you don't need to learn about time or distance when you study physics, you assume, like everyone else, that they can be measured and that's sufficient.
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That's what someone else is saying.
I'm not saying it.
Oops.
But you can make the same comments where they are saying it.
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Like, man, it's all energy waves interacting with your karma.
Or physics.
You choose.
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Most physical quantities require Units......mass is one quantity that has units
as a ratio of two numbers with the same units....the atomic mass unit is dimensionless
But by that argument a mass in kg or pounds or anything else is dimensionless too, as it's also the ratio of a mass to that of a standard. The point about dimensions is that they specify which standard you're using as the denominator in your 'dimensionless' ratio.
75kg is just shorthand for "if the reference is the kilogram, the mass is 75", or "the mass is 75 times that of the kilogram".
Then just to confuse the issue, there are units like the radian and the bel......
;D
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No. The mass is 75 kg, not 75 yards or bananas. The reference must be stated as part of the quantity.
75kg is indeed (or should be) 75 times the mass of the ISK prototype but it's also 165.35 times the mass of the imperial standard pound, which is a perfectly legal, scientific, trade, maritime and aeronautical measure in countries that are not fully signed up to the metric system.
Now in my book, 75 ≠ 165.35, but it's the same person.
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No. The mass is 75 kg, not 75 yards or bananas. The reference must be stated as part of the quantity.
75kg is indeed (or should be) 75 times the mass of the ISK prototype but it's also 165.35 times the mass of the imperial standard pound, which is a perfectly legal, scientific, trade, maritime and aeronautical measure in countries that are not fully signed up to the metric system.
Now in my book, 75 ≠ 165.35, but it's the same person.
Who are you replying to, you seem to be trying to contradict me with my own argument.