Talk:Mass

Redefinition of 1 kg

Hey guys, the redefinition of 1 kilogram has been done and Wikipedia has an article for this. Kindly update the page as it says that the redefinition is expected on may 20, 2019. Thanks. clickheretogototheuserpageofAggarwala2727 (talk) 07:16, 21 September 2019 (UTC)

IPK is listed as cast iron.

In the units section. It's made of a Pt alloy.— Preceding unsigned comment added by InviteToQuiet (talk • contribs) 14:10, 21 November 2019 (UTC)

Mass as an extensive property describing quantity of matter

My edit was reverted, again... 1) Mass is a property which measures the quantity of matter [of a physical body]. I cannot understand why the introduction should just say "Mass is both a property of a physical body [and]". "[p]roperty of a physical body" is too vague, isn't it? Which kind of property? I think it should be said that this specific "property" is the quantity of matter of a physical body. 2) Furthermore, the extensive and intensive categorizations of all units of measure is explained by the IUPACand there's an article of Wikipedia which can tell newbies what Intensive and extensive properties are. Many college textbooks use those two English words; if I'm requested to I can provide citations of these widely used terms in textbooks. I'm interested to hearing what other editors have to say about it. Thanks for your time Fabio Maria De Francesco (talk) 10:49, 19 January 2020 (UTC)

I have undone (, ) the addition, as the categorizations extensive and intensive are nowhere mentioned in the article, so they do not belong in the wp:LEAD, let alone in the wp:FIRSTSENTENCE. - DVdm (talk) 11:02, 19 January 2020 (UTC)

Ok, I understand that. But mass can be measured, therefore it needs a unit of measure and all UM's have "extensive" or "intensive" properties. This article is not about UM's. Any explanation of the categorization of all the UM's, the kilogram in this specific context, would be out of the scope of the article itself. That's why there's no need to mention it again elsewhere within the article.

For what regards the "measure of the amount of matter", please check the section of the article where it is stated that "Although inertial mass, passive gravitational mass and active gravitational mass are conceptually distinct, no experiment has ever unambiguously demonstrated any difference between them". Therefore the mass as a measure of the amount of matter (rest mass, inertial's, gravitational's, and so on) holds in every case. Fabio Maria De Francesco (talk) 11:40, 19 January 2020 (UTC)

Please have a look at wp:no original research and specifically at wp:SYNTHESIS. - DVdm (talk) 12:39, 19 January 2020 (UTC)

1) Please have a look at the IUPAC document cited above and in the edit you undid. The following sentence is pasted from page 6: "A quantity that is additive for independent, non interacting subsystems, is called extensive; examples are mass m, volume V, Gibbs energy G". Where's the original research? Please remind that the source was cited in my edit.

2) In your first reply in this thread you said you undid my edit only because of the term "extensive ". If so, I mean if you didn't notice other issues, why did you remove the words "quantity of matter [of a physical body]"?

I'm pretty sure we're misunderstanding each other due to the fact that English is not my native language. Please reconsider that revert. Now it's up to you, because I'd like to not go further in discussions about this issue. Thanks again for your time Fabio Maria De Francesco (talk) 15:13, 19 January 2020 (UTC)

I'm afraid that, unless I would repeat myself, I have not much to add to my previous replies. - DVdm (talk) 15:28, 19 January 2020 (UTC)

References

In energy-mass equivalence definition suggest adding example of proton's mass being mostly gluon energy

New to this semi-protected articles so I hope I'm doing this correctly

I was hoping to add an illustrative example to the definitions section on energy-mass equivalence.

Original paragraph:

Energy also has mass according to the principle of mass–energy equivalence. This equivalence is exemplified in a large number of physical processes including pair production, nuclear fusion, and the gravitational bending of light. Pair production and nuclear fusion are processes in which measurable amounts of mass are converted to energy, or vice versa. In the gravitational bending of light, photons of pure energy are shown to exhibit a behavior similar to passive gravitational mass.

Suggested change in context:

Energy also has mass according to the principle of mass–energy equivalence. This equivalence is exemplified in a large number of physical processes including pair production, nuclear fusion, and the gravitational bending of light. Pair production and nuclear fusion are processes in which measurable amounts of mass are converted to energy, or vice versa. In the gravitational bending of light, photons of pure energy are shown to exhibit a behavior similar to passive gravitational mass. The majority of the mass of a proton is from constituent quark, not simply the mass of its quarks.

Relevant Wikipedia article about nucleon masses being mostly gluons

Another link explaining this principal

Thanks! TerranIV (talk) 16:26, 21 December 2020 (UTC)

Appears to be potential WP:CIRCULAR. Please provide an actual reliable source. Melmann 11:29, 22 December 2020 (UTC)

References

Definitions :: number of 'physical notions'

The first sentence in this section states: "In physical science, one may distinguish conceptually between at least seven different aspects of mass, or seven physical notions that involve the concept of mass.", which brings the expectation of 7 physical notations, while the following bullet points ("number of ways mass can be measured or operationally defined") are only 6 (six). Either these two topics of "physical notions" and "ways of measurement / operational definition" are different from each other, or there is an unintentional distraction caused. If they are different, shouldn't those 7 physical notions be listed as well to avoid confusion? Can someone clarify it? --Mojtaba Mohammadi (talk) 11:58, 20 January 2022 (UTC)

Mass is NOT the quantity of matter of a body

I have edited the first paragraph of the article, providing a more scientifically accepted definition of mass.

The previous definition of mass as "the quantity of matter of a body" is a wrong and misleading pseudo-scientific conception. It also lacked references: the provided dictionary definitions https://www.dictionary.com/browse/mass, do not corroborate the definition of mass as "quantity of matter". It should be noted, still, that the proper definition should come from a standard, serious, widely accepted university-level physics textbook and not from a dictionary.

I foresee that someone might be able to provide a textbook reference supporting the "mass as a quantity of matter" claim. This is because centuries ago it was indeed believed by some mainstream physicists (such as Newton) that mass was "quantity of matter". Likewise with phlogiston, this once somewhat mainstream belief was discarded experimentally with the advent of particle physics. Because of that, some school textbooks still present the erroneous notion of mass as "quantity of matter", which is wrong and misleading for children. But no university-level, serious physics textbook, written in the past century by a high caliber physicist would use that definition, since it has been ruled out as a scientific hypothesis over 100 years ago.

Elementary particles, which all have the same "quantity of matter" (i.e., 1), have widely different masses. More than that: systems composed of massless particles have positive mass, when the massless particles interact and form bounded states. If you bring together two particles, the mass of the system is greater than the sum of the mass of the particles. Two bodies orbiting one another have more mass than the sum of the masses of the individual bodies. The same body, if it heated and increases it's temperature, also increases it's mass.

So it is as misleading to say that mass is "quantity of matter" as it is to say that electric charge is "quantity of electrons". Or even more, since, while massive macroscopic bodies in everyday live are composed of only one particle which causes electric displacement (the electron), they are composed of three different particles (protons, electrons and neutrons) which cause measurable mass, and the difference between the mass of the proton and the neutron is easily measurable: matter formed by atoms which differ only in that one proton is replaced by a neutron (thus conserving the "amount of matter") in each atom have noticeable difference in mass.

Probably the most proper experimental definition of mass is via inertia, and relativistically then mass is the internal energy of a system (meaning the total energy of that system in a frame of reference where the system has 0 total momentum), apart from the unit of measurement. The experimental and the relativistic definition are equivalent as long as relativity holds. So, as far as science goes, the relativistic is the correct explanation for mass, and it is also corroborated experimentally. For example, this definition correctly explains the mass of a proton (which is greater than the masses of the composing quarks) or the mass of a nucleus (which is greater than the sum of the masses of the protons and neutrons composing it). It is the definition every working physicist uses in order to calculate the mass of a body. Not "quantity of matter".

The sources for that definition are the same that you find in the page https://en.wikipedia.org/wiki/Invariant_mass. I think it is interesting that all the proper definitions and sources are listed on that page, while here you have kind of a completely different physics.

To be clear, it is incorrect to state that the relativistic explanation would be the "concept of mass in special relativity", as implied by this link: https://en.wikipedia.org/wiki/Mass_in_special_relativity. This would be like saying that the concept of heat as caused by microscopic movement (instead of phlogiston) is just the "thermodynamic concept of heat", while the main wikipedia article for "heat" still accepted the old phlogiston explanation. The relativity theory was the first (and only) theory to explain mass, just as the thermodynamic theory was the first to correctly explain heat. The other theories (such as the "quantity of matter" theory) have been experimentally discarded, while the relativistic theory is the only one that correctly calculates the masses of physical systems.

Notice also that this is NOT a situation where the old theory is an approximation of the modern one, like Newton's theory is an approximation of relativity which is still valid for practical purposes. This is not the case. Macroscopic bodies which have the same amount of atoms have widely different masses, depending on the mass of the atoms. Now someone might say: "but these atoms have more mass because they have more particles in it", and, as explained before, that would be wrong: atoms with the same amount of particles often have measurably different masses.

This is NOT original research as it is the standard understanding among physicists. I hope people can help me with sources that might discuss this more directly. — Preceding unsigned comment added by Jocryptowiki (talk • contribs) 22:18, 5 December 2022 (UTC)

Please undo totally incorrect edit

Please undo this edit:

• https://en.wikipedia.org/w/index.php?title=Mass&diff=prev&oldid=1164494690

The user who made it has severe language competence issues and, it seems, physics competence issues as well. 62.121.132.130 (talk) 08:44, 10 July 2023 (UTC)

Undone; thanks for spotting this. Certes (talk) 12:14, 10 July 2023 (UTC)

Hi. The 62.121.132.130 IP is a long-term abuser referred as by WP:BKFIP. Please, refer to admins. Thanks. AXONOV (talk) ⚑ 11:05, 11 July 2023 (UTC)

Hello,

I mentioned this value of 1.346x 1027kg/m for the first time in my article. Please specify the source. Mandresaazx (talk) 20:35, 25 September 2023 (UTC)

Mass is an intrinsic property of a body in three-dimensional space

Mass is an intrinsic property of a body in three-dimensional space Antypearl (talk) 11:05, 27 September 2023 (UTC)

Change to Short Description

Request to change the short description as the average person uses it as their foundation for understanding mass.

Request to change it to: A measure of a body's resistance to acceleration. Wikilus (talk) 13:57, 1 February 2026 (UTC)

I don't think that's true of the 'average person' - only those who have some elementary education in physics. 'Amount of matter' is more natural. MichaelMaggs (talk) 14:53, 1 February 2026 (UTC)

@MichaelMaggs Unfortunately, 'amount of matter' is inaccurate. Wikilus (talk) 14:59, 1 February 2026 (UTC)

The problem is that all of the (equivalent) precise definitions are somewhat technical, and are liable to fail WP:SDJARGON. "Measure of a body's resistance to acceleration' would indeed be more accurate, as would "Measure of a body's intrinsic inertia". Those would indeed be better for readers who have some knowledge of physics beyond an elementary level. I won't object to either if others feel the same way. MichaelMaggs (talk) 15:24, 1 February 2026 (UTC)

One list of non-SI units is all we need.

We have two lists of non-SI units for mass. The first one starts with a pointless historical claim:

• "Non-SI-units previously accepted for use with the SI include:"

The significance of this trivial bit of history is not sourced and explained. Both lists are non-SI units, both lists contain items that are not sourced. These are all just other units of mass now.

@NebY and I agree that these should appear in one list. @Tercer has reverted both of us. I ask that the two lists be merged into one. Johnjbarton (talk) 16:14, 15 June 2026 (UTC)

We shouldn't have a separate list for units "previously accepted for use" without any source whatsoever for that defining list characteristic. Even if that were to be sourced, it's not an important historical point. More sensible would be either to include everything within a single list, or to have separate lists for metric and non-metric units. MichaelMaggs (talk) 17:29, 15 June 2026 (UTC)

We do have a source, the new SI brochure still lists them, they are just described as "important to recall" instead of "accepted" now.

The broader point is that there is a big distinction between reporting mass in tonnes, which will make nobody raise an eyebrow, and reporting mass in slugs or inverse Compton wavelengths, which only make sense in very specific contexts. We shouldn't erase this important distinction. That the SI still makes! Tercer (talk) 17:47, 15 June 2026 (UTC)

I don't agree on importance (it depends on context in every case), but at the very least a citation is required. MichaelMaggs (talk) 17:49, 15 June 2026 (UTC)

Reporting mass in tonnes would certainly raise eyebrows if it was a mass previously reported in electronvolts or Daltons - they too "only make sense in very specific contexts". The SI does not still distinguish a group of units as accepted, and i don't think it's for Wikipedia to create a category of "previously accepted". NebY (talk) 18:08, 15 June 2026 (UTC)

As the electronvolt was not described as a unit of mass in the 8th or prior 9th editions of the SI Brochure, it would be wrong to describe it as "previously accepted" as a unit of mass now. NebY (talk) 18:24, 15 June 2026 (UTC)

The SI sources claims these are "widely used" and says the list is not exhaustive. I added a source and changed the content to match, leaving the two list. Johnjbarton (talk) 20:10, 15 June 2026 (UTC)

We might source "previously accepted" to editions of the SI Brochure. They're described as accepted in versions of the 8th and 9th editions prior to this year's v4.01, which drops the term, so perhaps we'd cite both the 8th and the current 9th to show that they were accepted but that was previously. Or is that WP:SYNTH? (The minutes of the 2004 CIPM suggest there was some sort of significant shift from the 7th edition regarding this description but I don't have that edition on file.) NebY (talk) 17:58, 15 June 2026 (UTC)

The 7th edition has "accepted", describing it as a term introduced by the 1996 CIPM. NebY (talk) 18:53, 15 June 2026 (UTC)