Talk:Mass/Archive 1

message: A convention should be adopted as to how wikipedia uses the word mass. It is modern convention for mass to mean *rest mass* - and I think this should be noted on this page. Discussion needed. Fresheneesz 06:48, 22 November 2005 (UTC)
thread_title: Relativistic mass VS rest mass

message: The following is from the article on Standard_model:
"Mass is really a coupling between a left handed fermion and a right handed fermion. For example, the mass of an electron is really a coupling between a left handed electron and a right handed electron, which is the antiparticle of a left handed positron. Also neutrinos show large mixings in their mass coupling, so it's not accurate to talk about neutrino masses in the flavor basis or to suggest a left handed electron neutrino and a right handed electron neutrino have the same mass as this table seems to suggest."
Does that make sense? If so, is there a way to expand on it in some way that would make sense to non-experts? JWSchmidt 21:52, 25 Mar 2004 (UTC)
thread_title: Question about the origin of mass

message: : The demostration of equivalance of the time of falling object was carried out before the "Apollo 15 Moon walk". It was carried out a lots of times (it even was a classical laboratory experiment) in a vacum tube. I have not a precise date for the first experiment (I suppose it was in XVII or XVIII century since the vacum technique was enougth good at the time for this experiment). The demostration on the Moon is obviously a very spectacural one, but it is not hte first. Even more also the experiments in the vacum were very spectacular centuries ago, when people was not used to vacum technique. AnyFile 19:23, 26 Oct 2004 (UTC)
thread_title:  Demostration on the Moon 

message: I'm not sure what they do in commerce, but I'm pretty sure that the typical measure of body weight in humans via a bathroom scale, for example, is weight, not mass.  If you take the same scale to the moon, and put the same person in it, the scale will read a smaller number.  They are essentially springs measuring the force.  They measure weight, not mass.
Also, why do you say "an object will exert more force" in a stronger gravitational field?  This is true, but rather irrelevant.  Weight is the force that your planet exerts on you.  and that's what the scale measures.  
Finally, what's with the clause "the quantity the weight we use in commerce"?  I can't quite convince myself that this clause is grammatical.  Can you parse it for me? Lethe | Talk 18:24, Feb 4, 2005 (UTC)
:Have you ever turned back a paycheck because you do so little work, Lethe?  How about you, CYD?  I'd bet that the jargon usage there doesn't cause either of you any difficulty.  Why, then, do you have such great problems understanding similar ambiguities in the word weight?
:If you are pretty sure about the issue of human weight, then you obviously haven't put much thought into it at all.
:*What happens when you get serious about your weight, and go weigh yourself on one of those beam balances at the doctor's office or the gym?  Isn't that a better indication of what you want to measure, than some substitute we put up with in our homes because it is cheap?  
:*What happens in your little thought experiment about taking these scales to the moon?  Those balances are mass-measuring devices, not force measuring devices. Those cheap bathroom scales (which didn't even exist until 1937) are no more accurate in measuring force than thay are in measuring mass on Earth.  If you hop on your mother's bathroom scale, and it reads 5 lb or even 5 kg less than your bathroom scale at home, you don't automatically credit it to success of your weight-loss diet, do you?
:*Of course, those pounds and kilograms, units of mass, are what people use when they weigh themselves, all around the world.  Or stones, and while there are kilograms-force and pounds-force, I've never heard of any stone-force.
:Even in the United States, many hospitals measure body weight in kilograms.  Often, they can even measure this weight in either pounds or kilograms.  But hospitals like to be more accurate, not having variations between the scales in different departments, or if a patient is transferred to a different hospital.
:*So how do you think those hospitals calibrate their scales?  They place a test weight (an object of known mass, exerting an unknown and irrelevant amount of force due to gravity) on the scale and compare its known mass to the scale's reading.  Nobody ever calibrates these scales differently for measuring pounds than they do for measuring kilograms, either.  In fact, it is often the same scale that can measure both—either by flipping the bar on those old balance beams, to get a different set of detents for the weights, or by a constant conversion factor (the same anywhere in the world) programmed into modern electronic-readout scales.
:*NASA doctors use the same terminology their counterparts with Earth-bound patients use, when they study "weight loss" of astronauts in space, etc.
:Then, of course, there is our Body Mass Index; weight in kilograms, divided by the square of height in meters.  Or, as the article puts it "(This is 703.07 times the weight in pounds, divided by the square of the height in inches.)"  Once again, note the constant conversion factor.  If the kilograms and pounds were measures of different things, we'd need a variable there.
:Here are some of standards organizations on this point.  American Society for Testing and Materials, Standard for Metric Practice, E 380-79, ASTM 1979:
:*    3.4.1.2 Considerable confusion exists in the use of the term weight as a quantity to mean either force or mass.  In commercial and everyday use, the term weight nearly always means mass; thus, when one speaks of a person's weight, the quantity referred to is mass.
:NIST Guide for the Use of the International System of Units (SI), section 8.3
:*Thus the SI unit of the quantity weight used in this sense is the kilogram (kg) and the verb "to weigh" means "to determine the mass of" or "to have a mass of."
::Examples:   the child's weight is 23 kg 
:I'll fix the typos in the language you didn't understand this time around.  Gene Nygaard 22:53, 4 Feb 2005 (UTC)
thread_title:  mass vs weight 

message: I do not understand this (end of the first section): 
:if one were to treat inertial mass mi, passive gravitational mass mp, and active gravitational mass ma distinctly, Newton's law of universal gravitation would take the form m_ia=\frac{Gm_pm_a}{r^2}. 
Are there implicitely two bodies? What is r? It seems misleading to me and if you agree, I would like to remove it. --Philipum 13:41, 27 May 2005 (UTC)
replies: text: Yes, there are two bodies.  Newton's Law of Universal Gravitation states that the gravitational force between two bodies is inversely proportional to the square of the distance between them.  That explains the r2.  You haven't said what is misleading about this statement, only that it is unclear.  Why do you want it removed? -Lethe | Talk 17:39, May 27, 2005 (UTC)
I suppose I find it misleading because it gives the impression to be a bizarre way to define the different mass concepts of inertial mass, passive gravitational mass, and active gravitational mass. I also react against the asymmetry of the expression: it gives the impression that we have a mass that creates the field and a mass that feels it, but in reality both masses play both roles. Removing it would not make any harm since the laws of gravitation are explained in more details later in the article. --Philipum 06:35, 30 May 2005 (UTC)

text: But that's the whole point of the formula: there are three different places where what we call mass enters into the equations, therefore three different operational ways to measure mass.  The fact that they should all be equal is not a priori obvious, is subject to experimental verification, and is the basis of several theoretical foundations.  It's hard to make an experimental verification if you do not recognize the formula to follow. -lethe talk 22:50, 5 December 2005 (UTC)

text: I clarified it.--Patrick 02:06, 6 December 2005 (UTC)

text: OK, that's fine. --Philipum 08:49, 6 December 2005 (UTC)
replies: text: Its still not fine, noone defined what a is. What is it? None of these types of mass make sense to me, one of them doesn't even look like mass, its a force. Active gravitational mass looks like a force (later note: i'm sorry, not force, gravitational field - which is still not mass). Someone needs to define a at the very least. Fresheneesz 05:41, 9 December 2005 (UTC)
thread_title:  Misleading? 

message: Not having had much success before, I will ask again, in its own section:
# Why do we refer to "mass" as a "concept" and not a quantity?
# How can a "concept" have units?
Brian Jason Drake 08:28, 22 September 2009 (UTC)
replies: text: I've gone ahead and rewritten the introduction with some operational definitions of mass. It's far from perfect but it's a start. Strad (talk) 23:25, 22 September 2009 (UTC)
thread_title:  Concept? 

message: The discussion in the Mass#Weight_and_amount section is partly irrelevant to this section.
The fact that the two sides of a balance scale are subject to the same gravity force because they are so near is such a tiny detail that needs certainly not be mentioned in this section. So, all the part about gravity being almost equal on the Earth is scarcely relevant and would be better separated in a section immediately preceding Mass#Weight_and_amount, called Mass#Weight_and_mass.--Pot (talk) 09:02, 26 September 2009 (UTC)
replies: text: I think it would be better to completely rewrite that section as something concerning "Measurement of mass". Much of the current speculation about atomic weights and the atomic mass unit is quite simply wrong, for example! On the other hand, I think it is fair to mention that masses in the everyday range of around one kilogram are usually measured by comparing weights in a constant gravitational field. Physchim62 (talk) 12:08, 26 September 2009 (UTC)
replies: text:  If we are speaking about the second paragraph of the Mass#Weight_and_amount section I agree completely.  But, for a start, it would be better to split it and put it into a new section that precedes the current one. Once this is done, it will be easy to rewrite it. As it stays now, the second paragraph has tone and content which are quite extraneous to the rest of the section. --Pot (talk) 12:14, 27 September 2009 (UTC)
thread_title:  Weight and amount section partly irrelevant 

message: "In physics, mass (from Ancient Greek: μᾶζα) commonly refers to any of four properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass."
It says "four properties", then lists only three. Facts707 (talk) 07:31, 17 January 2010 (UTC)
replies: text: Fixed. Strad (talk) 15:53, 17 January 2010 (UTC)
thread_title:  Lead sentence is inconsistent within itself 

message: "Special relativity provides a relationship between the mass of a body and its energy (E = mc2). As a consequence of this relationship, the total mass of a collection of particles may be greater or less than the sum of the masses of the individual particles."
The statement only makes sense with reference to sub-atomic particles, yet this important distinction has not been made; rendering the statement misleading to anyone not already in posession of a detailed understanding of the subject matter. A better way to introduce the subject, would be to simply say that: According to The Theory of Special Relativity mass and energy are equivalent, and related by the formula... This equivalence is apparent in fission and fusion reactions, whereby mass is converted to energy, by th process of splitting or fusing atoms.
Airophile (talk) 06:52, 29 October 2009 (UTC)
replies: text: The problem is that mass is NOT "converted" to energy. This is popular misconception (one of the most pervasive in science) and it's just wrong. Those of us who know better have to deal endlessly with people who think they know what E = mc^2 means. It MEANS that mass and energy are the same thing, and neither one appears without the other. Both are separately conserved (for a given observer) over time. The only way either one increases or decreases is if you're looking at a sealed system and you let some escape. Then both mass and energy go out together, however, the total (including what escaped) remains the same. This article would be much simpler if it said "Mass is a conserved quantity (it can neither be created or destroyed), and special relativity did not change this understanding. However, relativity did add the fact that all types of energy have a mass, and this mass is added to systems when the energy is added, and the mass is subtracted when the energy leaves." SBHarris 03:46, 27 January 2010 (UTC)
thread_title:  Confusing and clumsy reference to mass/energy equivalence 

message: In the section about equivalence of inertial and gravitational masses, the paragraph detailing galileo's experiments has at least two full sentences written by Stephen hawking in his book "a briefer history of time" .  More plagiarism may be present but I have not investigated beyond that point  —Preceding unsigned comment added by Ahuramazda8 (talk • contribs) 20:58, 8 November 2010 (UTC)
thread_title:  Blatant plagarism 

message: This is what Wikipedia tells in the first chapter. I can't understand neither am able to improve. Please discuss. --193.56.241.75 (talk) 12:21, 12 October 2011 (UTC)
replies: text: Thanks for spotting that error.  I've restored the missing information.  I hope it makes sense now.  I'm surprised that this (accidental?) deletion was not spotted and corrected earlier.  Dbfirs 08:12, 19 November 2011 (UTC)
thread_title:  The gram (g) is electronvolt is common in particle physics. 

message: Last lines in "Unit of mass" section include "...identified with its inverse Compton wavelength (1 cm−1 ≈ 3.52×10−41 kg)". I guess it should be just "1 cm" instead of 1 cm−1. Am I missing something? manya (talk) 11:25, 30 September 2011 (UTC)
thread_title:  Mass as length 

message: I'm not maven but to me, the current definition is not felicitous therefore I devise the following with the help of theories of gravity.
Since gravity or changing curvature of spacetime is the innate property of matter therefore 
1- A mass of an object may be defined as "a quantitative might of its prime acceleration [gravitational]"  - A prima facie might of its prime acceleration"
2- A mass of an object may be defined as "a qualitative appraise of its distortion of spacetime"68.147.52.247 (talk) 05:01, 11 January 2012 (UTC)
replies: text: Go look at mass in general relativity. The devil is in the details of how you "quantitate." SBHarris 05:53, 11 January 2012 (UTC)
thread_title:  An idea if not inane 

message: There is some (modern) history of gravitational mass with Kepler etc. Very much less so with inertial mass. If history is no part of this article, shouldn’t there be at least a reference to the pages about inertia, about impetus?  — Preceding unsigned comment added by DominiqueM (talk • contribs) 14:57, 29 July 2012 (UTC)
thread_title: History of inertial mass

message: I basically reverted a recent edit about the rate of time passing on the Earth, compared to outer space. There is a common confusion of words about "fast" and "slow", re time. In a heavy gravitational field, time travels more slowly (e.g. at the event horizon of a black hole, time doesn't pass at all, and events are frozen). A clock at the earth's surface will tick more slowly than a similar clock in outer space. The confusion arises from thinking that this slowness "expands" the time, but when you think about it, the fact that the clock ticks more slowly means that less time is registered on the clock, compared to a similar clock in outer space.77Mike77 (talk) 00:50, 22 March 2013 (UTC)
thread_title:  Re "faster" and "slower" as vocabulary re Time. 

message: The distinction between mass and weight is a recent aspect as scientific concept.--86.120.44.145 (talk) 18:56, 15 July 2013 (UTC)
thread_title:  Distinction between mass and weight 

message: Discussion started in Talk:Mass#Basic disagreement about the lead section of this article but that section got unwieldy in length.
Steve, I agree that amount of "matter" is not fundamental to the modern understanding of mass, and the lead should reflect that. 
On the other hand, we shouldn't bury a notable viewpoint, just because we (as editors) don't agree with it or even can disprove it by some argument.  Especially if that viewpoint may (whether intentionally or not) represent a [flawed] attempt to capture some valid aspects of the article's subject.  
For example, "amount of matter" (or "quantity of matter") may suggest intuitively that we can choose to talk about mass as "stuff" (whether material or not), beyond being "merely" a property of a system.  When you transfer "stuff" from one system to another, you expect one system to now have less of it and the other system to have more of it, by the same amount unless some transformation or conversion of the "stuff" also occurs.  E.g. "I transferred 1 kg of mass".  You wouldn't say "I transferred 3 kg/m^3 of density" from one system to another -- there's no reason the second system's density would increase in general by the same amount by which the first system's density decreased.  This may correspond to mass being an extensive quantity (or additive) while density is an intensive property.    If a system comprised two identical (but isolated/non-interacting) subsystems, then, for any extensive property like mass (or volume, moles of hydrogen, electric charge, or of course any form of energy for example), the system would have twice the amount of it as either subsystem has. 
Amount or quantity may also allude to it being a ratio scale, meaning it has a non-arbitrary "zero" and that it is possible to say one system has "twice as much" or twice the magnitude compared to that of another system, as is the case with all the extensive and intensive examples above as well as absolute temperature(an intensive ratio scale), but unlike an interval or location scale such as degrees Celsius, or today's date (say Julian day), or electric potential, or my latitude or longitude, all of which have a zero value as merely a reference point which could just as well have been chosen differently. 
As for the first sentence of lead starting with "mass can be described as an associated measure of the total quantity of energy in an object", this is true but it doesn't directly tell us very much about the nature of mass, until we find out something about the nature of that measure being alluded to, and put it all together.  
If this were an article about mass as merely a physical quantity, then we could simply define it as E/c^2 and refer the reader to Energy article for E, and to Mass-energy equivalence for the formula itself.  Otherwise, this article should be about the concept of mass (especially the modern one but also eventually the historical ones), which can't be separated from inertia/gravitation, because these are the particular characteristic measures/manifestations/phenomena/consequences/effects/behaviors of energy that characterize the concept of mass. 
When we say light bends as it passes by massive bodies "because it has mass", we mean that it exhibits those inertial/gravitational phenomena that collectively characterize mass (relativistic mass in this case).  When we say a body gets "heavier" as it accelerates towards the speed of light, we don't simply mean "it has more energy, of which, as usual mass is simply one measure", but that it has more inertia. 
That's why I (and now Steve) favor a first sentence involving something like:
:Mass is a property of a physical system or body, observable and measurable as a resistance to acceleration or in the strength of its mutual gravitational attraction with other bodies.
This captures this nature of mass in the simplest possible terms, and it captures the aspect of it that held in the 19th century as well as today.  It doesn't mention energy, but that could be in the second sentence, or maybe worked into that 1st sentence.
DavRosen (talk) 19:07, 11 July 2013 (UTC)
replies: text: Your idea to start with inertia and gravitation-source/sink as the definition, is a good one, and I approve. Feel free to move it around. Then (if you like) you can add that we also know that the "stuff" we're talking about as mass is ALSO always a property of all kinds of energy (the ability to do work = force X distance), as though it was the universe's bookkeeping agent to "remember" how much energy has been stored or deposited, as a never-changing-quanity in the universal "bank." Or perhaps the total does change as the universe expands, like some currency inflation (pun). Energy is a very squirelly thing, and it's not at all obvious how the different types of energy are like each other-- the frequency of a wave, the velocity of a particle, the storing of potential in a field. But they all leave behind this calling card of increased inertia and gravitation/space-time bending that we call "mass."  To me the oddest thing is that this "mass" sometimes has no location, anymore than the energy associated with it does. Where (for example) is the mass of the kinetic energy of two particles A and B relative to each other? From the viewpoint of A, the extra kinetic mass-energy is all located at B, and from the view of B, it is all located at A. From an observer in the COM frame, it is divided between the two. So where IS it? Hard to say. It's stored in the structure of space-time somehow, as a RELATIONSHIP between the two particles, that has no specific THERE or SPOT. They could be light years away from each other and the universe still keeps track of the balance, which is somewhere associated with the two, but no place in particular, anywhere in the universe inside their light cone. The reminds me of nothing so much as quantum entanglement. Kinetic energy must be stored as entanglements, otherwise it makes no sense at all. The same with the energy of photons, which individually do not HAVE an energy, since it can be anything you like (pick your observer). Only when we get to photon pairs are we forced to stop that game, and now (again) behold, it's all in relationships. Long distance relationships if you must, but relationships it is. Grav waves and EM waves have points where the fields are zero, and energy/volume is zero. So where is the energy carried by the wave? Spread out over a volume; one part of space doing something different relative to ANOTHER. It's always like that. Nothing is pinned down.  Finally, I'm sorry to be longwinded, but your idea that we use the horrid word "matter" as a stand-in for the "stuff" that we transfer from here to there as "mass" and that has "energy", I think it's a bad idea. The "stuff" we're talking about is mass-energy. It is mass (which always has energy), or energy (which always has mass). Only when pinned down as nice stopped particles with a rest mass is all this pretty and looks like "stuff." Otherwise, it's not stuff!! It looks like kinetic energy, which doesn't look like stuff, and has no location. It looks like EM radiation, which isn't any stuff you can hold in your hand ("How do you hold a moonbeam in your hand...?"). It is E or B fields, which aren't stuff, but force fields. Other force fields as well-- virtual pions, or weakons or gluons or whatever. This is not what anyone ever meant by matter, which originally was a word that differentiated things from the realm of pure energy. But pure energy has mass! Most of the mass of ordinary things is not particles with rest mass. Calling that stuff "matter" is cheating. If that's "matter" then the only thing that isn't "matter," is field-free vacuum. And perhaps vacuum with static gravitation fields in it. SBHarris 00:39, 12 July 2013 (UTC)
replies: text: Dave, I already altered the lead with your opening statements, and follow up sentences. Then I added Mr. Sbharris' contributions after that. So, I would think that the opening of this discussion is a step or two behind the editing of the article; except I see that Dave and Sbharris have already done some deft copy editing. Maybe I am in a time warp or time loop after discussions of photons, light, relativity, and energy. Anyway, the lead is really good, especially after the copy editing. I am really glad we have been discussing this. ---- Steve Quinn (talk) 01:04, 12 July 2013 (UTC)
replies: text: Sbharris, I appreciate the statement you made in the edit history: "Your mass is mostly gluons and glueballs, and who is to say if these are 'matter'??". I think this is a really good point, and one that I didn't think about before this. I think this would be a good point to add in the lead paragraph. We know it is gluons, "glueballs???", and quarks, but are we really referring to matter? Also, I see some really good points being made in the three paragraphs of your previous entry. Such concepts and possible conclusions are certainly mind blowing. Yes, where is the kinetic energy located? Also, why not use the following from your first above paragraph: "But they all leave behind this calling card of increased inertia and gravitation/space-time bending that we call "mass."" We can give a background explanation, as you did in the first paragraph. That is really clear to me what you are saying. Based on energy is conserved (in a closed system?) and mass is conserved, where the heck does it really go? Anyway, I say, let's use everything we can from these three paragraphs ----Steve Quinn (talk) 01:45, 12 July 2013 (UTC)
thread_title:  Lead section: continuing discussion 

message: Ok comments coming from an novice.
We know mass curves space time right.  We have learnt that from lensing of light around stars / galaxies etc.
Shouldn't mass be represented as a fundamental forumla for the curvature of space time then?
Is this formula already out there? 
I'm just thinking the curvature exists well outside the volume that is matter, i.e. by light curving around the galaxy, so the mass formula should decrease at some function of the distance.
E=MC^2 has always bothered me as a fundamental law, its seems to much of an oversimplication using a scalar value taken from matter. It seems like mass should be expanded to properly account for space time.  In other words, energy / mass is what the universe is and trying to describe it in a fundamental formula that does not acknowledge the dimesion it is framed in seems odd.
Also a single curvature for say the sun is a massive simification isnt it? In reality wouldn't space time be more of a cumulative craterfield from each mass from a fundamental particle.
Are people getting me here?
Cheers
Clayton Fairs— Preceding unsigned comment added by 202.58.224.16 (talk) 06:53, 23 September 2011 (UTC)
replies: text: I guess I think I know what you mean: you figure that the "E=MC^2" sprinkled with some hand-waving about "curvature" you were fed by the media is a "massive simplification". You are spot on, it is a massive simplification. The problem is, the full description is right there, only, it is fiendishly difficult to solve, so even sharper minds than either of ours are reduced to assuming massive simplifications, simply because if you don't simplify, you are not going to get any result. --dab (𒁳) 20:44, 13 December 2011 (UTC)
thread_title:  Question - Mass and curvature of spacetime 

message: The article goes into some detail about Kepler's modeling of the planets' motions. But Kepler used geometric and proportional reasoning, and this was not tied to mass at all. From the article: "Johannes Kepler was the first to give an accurate description of the orbits of the planets, and by doing so; he was the first to describe gravitational mass." This doesn't follow at all. The motion of the planets is governed by their masses,(in the modern understanding) but Kepler believed that they were governed by the proportions of platonic solids and the music of the spheres. Galileo's experiments and Newton's laws are obviously relevant, but I think Kepler doesn't deserve a whole section here. Forbes72 (talk) 02:57, 6 December 2013 (UTC)
thread_title: Kepler doesn't belong here

message: My general impression of this article is that it is a mess. Its a mash-up of distinct meanings for the term "mass" and badly fails to spearate meanings from their repsective contexts of use.  Worse, the most used meme is wrong...or rather obsolete. Velocity does not impart mass to an object or system.
I am watching Leonard Susskind's video lectures The Theoretical Minimum, specifically Special Relativity and Electrodynamics (2012), Lecture 3. (http://theoreticalminimum.com/courses/special-relativity-and-classical-field-theory/2012/spring/lecture-1). At 1 hour 00 minutes 30 seconds he states that the concept used in most of THIS article, that mass is variable, is NOT used by any physicists he knows of, and is an anachronism, only being used in physics (undergraduate) textbooks. Since there seems to be general agreement here, in this case, that Wikipedia should go with the textbooks rather than with modern Scientific usage (ie with the teachers, rather than with the professionals), I'm probably sneezing into a strong wind, but I felt I should at least point out that the consensus here is not shared by at least one eminent Physicist, and moreover he states it is shared by virtually none. He specifically states that mass is what was previously called rest mass, that it IS invariant (since it is defined as the mass at rest) and that photons DO NOT HAVE any.  He also states that the mass of a system of bound particles is less than the mass of the individual particles (due to the energy used in bonding, by implication by (some of) the potential energy of the system) and has NO contributions from velocity.
At the least this viewpoint (the modern view) should be given prominent position.  The different meanings (including the obsolete one) should be separated and then the theory should be developed for each separately.
I suspect that Classical Physics, Special Relativity, General Relativity, the Standard Model (particles), and possibly even the Λ-CDM model have distinctly different definitions for the term.  Keep in mind that the same term can be used for an "atomic" particle as well as for systems of particles in some (or all?) of these domains.
::
Here are two other things I think are wrong:
:::
First:
The lede states that mass is difficult to "directly" measure.  I don't know what that means.  I think mass is EASY to measure.  I can do it gravitationally or inertially quite easily (depending on precision). The symmetry breaking (LOL) between weight and mass only occurs when the gravitational curvature is substantially different from "standard".  (A recent paper in Science magazine described a technique to differentiate the difference in gravity equivalent to a couple of inches of altitude at sea level. Not easy.) It is just factually not true that mass is difficult to measure. This point of view seems to be confused about what measurement is, or perhaps the author thinks he has some clear idea of what constitutes a direct (compared to an indirect) measurement. Comparisions are direct (1-to-1 correspondance is the most fundamental mathematical operation).  I can compare two masses EASILY.  
:::
Second:
Quote:"From a fundamental physics perspective, mass is the number describing under which the representation of the little group of the Poincaré group a particle transforms." Unquote. This monstrosity from section "Weight vs. Mass". Need I say more?
::
Needs a rewrite.  Needs clarity.  And definitely needs more on Higgs Boson and the conceptual difference between say claiming that the mass of a proton (as a particle) is X and that the mass of a proton (as a system of particles and fields) is mostly "energy".173.189.72.14 (talk) 22:30, 12 February 2014 (UTC)
thread_title:  Lede discussion - continued. 

message: "The kilogram is 1000 grams (g), which were first defined in 1795 as one cubic decimeter of water at the melting point of ice." 
This is still awkward, because it wasn't 1000 little grams that WERE defined as a cubic decimeter of water; rather, a kilogram WAS defined as that. Hard to correct...maybe this: "The kilogram is 1000 grams (g), and was first defined in 1795 as one cubic decimeter of water at the melting point of ice."77Mike77 (talk) 23:52, 11 March 2014 (UTC)
thread_title:  Re recent correction 

message: I performed a small edit the other day that seemed to have polished away the last remnants of a quote from Robert Hooke (in the section about Newtonian mass). I was interested to see what the actual quote was/is, and whether anything had been lost. Here I've transcribed it verbatim (from p.27-28 of the reference) with typography preserved:
I realize it's quite lengthy, but I'd like some or all of it to be (re)integrated into the article. The current paragraph as I've left it simply tells the reader in a rather drab way the bare facts about gravitation that they probably already know, rather than use the opportunity to present them with some poetic, scientific, hiſtorical quote that they've probably never read. It's more interesting to tell the reader what Hooke actually said than what he meant, right? nagualdesign 04:38, 28 September 2014 (UTC)
replies: text: Okay, I've reformatted the quote (blockquote → Quote box) so that it might be more suitable for inclusion in the article. Anyone care to comment..? nagualdesign 20:34, 5 October 2014 (UTC)
thread_title:  Robert Hooke quote 

message: I've been confused for a long time by the fact that this article doesn't mention at all quantum mechanics. For instance, we have lots of QM articles that discuss the (hypothetical) role of the Higgs in giving mass to particles (which would imply it's responsible for everything that we perceive to have mass). However, the word Higgs doesn't appear anywhere in this article, nor as far as I can tell does anything related to quantum mechanics. How so? bogdanb (talk) 14:04, 19 January 2010 (UTC)
thread_title:  Quantum mechanics / Higgs boson 

message: The headline sentence is currently "In physics, mass is a quantity which describes the capacity for a physical body to absorb and store energy." That seems to be somewhat misleading, surely that is more like a definition of thermal capacity? A free electron in space can't absorb energy but that doesn't mean it has zero mass for example.
Relativity and QM give different definitions, in QM via the Higgs mechanism and in relativity from energy and momentum. Can I offer two alternatives based on the relativistic understanding, first "Mass is a measure of the energy bound in an object." or better "Mass is a measure of the amount by which the energy of an object exceeds its momentum: m2 = (E/c2) - (p/c)2 where E is the total energy and p is the magnitude of the momentum."
The latter is a bit more technical but is the most accurate and is directly comparable with the energy-momentum relation on this existing Wikipedia page. It has the advantages that it works for all particles, it gives a value which is Lorentz invariant (i.e. it does not depend on speed so avoids the anachronistic concept of "relativistic mass") and it is also valid for system of particles, so for example it gives zero mass for a single photon but a non-zero value for a pair of photons (or more). The combined value is also invariant even though individual photon energies and momenta will vary with the frame.
It could also be noted that taking energy and the three momentum vector components as a 4-vector results in mass being defined as the magnitude of that vector which is then obviously invariant under a Lorentz Boost but that would be more suitable for the body of the article than a headline and could connect to this section.
George Dishman (talk) 09:41, 7 March 2015 (UTC)
thread_title:  Misleading headline 

message: I check pages listed in :Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of :Mass's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.
Reference named "Sen":
From Tachyon: A. Sen, "Rolling tachyon,"
  JHEP 0204, 048 (2002).  Cited 720 times as of 2/2012.
From Tachyonic field: 
Reference named "Feinberg67":
From Tachyon: 
 See also Feinberg's later paper: Phys. Rev. D 17, 1651 (1978)
From Tachyonic field: 
Reference named "Kutasov":
From Tachyon: 
From Tachyonic field: 
I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT⚡ 00:37, 23 June 2015 (UTC)
thread_title:  Orphaned references in [[:Mass]] 

message: The article currently says: Hooke conjectures that gravitational forces might decrease according to the double of the distance between the two bodies.(click)   What does that mean? Is it equivalent to "inversely proportional to the square of the distance"? Ceinturion (talk) 16:06, 28 March 2016 (UTC)
thread_title:  Decrease according to the double of the distance? 

message: This article is sorely missing a section on measuring mass. The article Proposed redefinition of SI base units sort-of gets into this.  This article could/should provide a section explaining *why* the measurement of mass is related to planck's constant, etc. 67.198.37.16 (talk) 17:25, 10 April 2016 (UTC)
thread_title:  Measuring mass 

message: The article says
:\frac{m_X}{m_Y}=-\frac{\boldsymbol{a_Y}}{\boldsymbol{a_X}}\!.
which is probably wrong (or at least an abuse of mathematical notation), as aY and aX are supposed to be elements in a vector space and vector division is not defined there. Suggest taking norms before performing division. Thanks. JacobRodrigues (talk) 13:34, 27 December 2013 (UTC)
replies: text: The notation was certainly incorrect. Anyone familiar with the subject would know what was meant, but the mistake was lazy. Additionally, using X and Y to denote the objects instead of Cartesian coördinates seems confusing. I have changed it to objects 1 and 2 instead. Forbes72 (talk) 02:43, 21 January 2014 (UTC)
replies: text: The above is Mach's definition of mass. The accelerations are not vectors but scalars pointing along the line separating the two masses.  However, this definition is wrong for two reasons.  First, it is impossible to measure instantaneous acceleration; this was pointed out by Poincare as an "insurmountable problem" in Mach's definition.  Second, Mach's definition is wrong because it fails to take into account the energy needed to bring the two objects together; that energy (potential energy) alters the mass of the system as a whole by P.E./c^2. So, for example, the mass of a proton in deuterium is *less* than the mass of a proton in free space.  See for example:  "There Is No Really Good Definition of Mass" - Eugene Hecht. 67.198.37.16 (talk) 18:31, 10 April 2016 (UTC)
thread_title:  Inertial mass 

message: A  recent edit by Ggonzalm states "The difficulties in obtaining a single definition of mass are probably caused by the lack of a unified theory of physics. For this reason Einstein, Schrödinger and others pursued a geometric unified theory. It was clear to them that... "
IMO, this either requires references or might be considered  original research.
WikiDMc (talk) 15:50, 8 March 2011 (UTC)
replies: text: Its not OR, its the truth!  Max Jammer has a book on this, Frank Wilczek has a recent paper:  http://arxiv.org/abs/1206.7114 67.198.37.16 (talk) 18:34, 10 April 2016 (UTC)
thread_title:  Recent edit - WP:OR? 

message: What tool is used to measure the mass of a hydrogen molecule?
What tool is used to measure the mass of the planet Mercury?
This article mentions a few tools that can be used to measure masses of a few milligrams to a few metric tons. However, my understanding is that balance scales, spring scales, the oscillating massmeter, Dumas method of molecular weight determination, etc. are all impractical for measuring the above objects.
My understanding is that in practice, a series of different tools are used to measure the mass of much smaller and much larger objects -- similar to the way the distance ladder uses a series of different tools that each measure distances in some range.
What are those different tools for measuring the mass of an object?
Is there some other article that lists all of those tools (with links to the individual article on each tool)?
Should those tools be listed in this mass article or perhaps the orders of magnitude (mass) article?
--DavidCary (talk) 00:32, 29 April 2016 (UTC)
thread_title:  How to measure mass 

message: I added a "too technical" tag to the article. This is supported by the following discussion sections (and probably others): 
# #Who are the readers of this article?
# #Definition of "mass"?
# #This article is a tad too high level
"Mass" is such a common and fundamental quantity that an article on it in a general encyclopedia should be accessible by everyone (or at least there should be a clear distinction between the common meanings and the advanced physics ones). Brian Jason Drake 08:19, 22 September 2009 (UTC)
replies: text: I really liked the intro.  I found it geared nicely to the novice.  And I think an encyclopedia article can get as technical as it likes, as long as the intro is written for the novice and the subject is built from there.  Unfortunately, the most common error I've found in Wiki is intros written by  experts for experts, unfathomable to the novice. Pb8bije6a7b6a3w (talk) 01:53, 31 May 2016 (UTC)
thread_title:  Article is too technical 

message: Does this distinction need to be made in the initial definition? The average person isn't interested in arcane distinctions that are meaningless outside of General Relativity and advanced field theory. The average person deals with the common-sense world of Newtonian gravity, in which the distinction is meaningless. If two objects have the same mass, they interact gravitationally according to the formula, and it is impossible to say which is "active" and which us "passive". This seems to have been introduced into physics teaching several decades ago, for some reason. It is of no value to people who are not taking a PhD in physics.
Newton would have done it this way: take a known mass M, an unkown mass m, at distance r (between centres of mass), and measure the force pulling them together. Use the formula to calculate the unknown, m, which is THE gravitational mass. (You could make the larger mass, M, the unknown instead, and measure THE gravitational mass the same way). There is no meaning to the words "active" and "passive" in this Newtonian picture.
Later in the article, if, say, the behaviour of a lepton near the event horizon of a black hole is being discussed, the words "active" and "passive" could be introduced. It is of no value to someone buying a pound of butter.
This link gives an idea of where this distinction arose  http://www.edition-open-access.de/sources/5/chapter_21.html
It is quite out of place in the basic layman's definition of mass that should begin a wikipedia article.
77Mike77 (talk) 21:53, 11 February 2013 (UTC)
replies: text: I don't know why it is being said that this is an advanced topic. Consider the test proposed by Galileo to drop two masses from the tower of Pisa. Since the mass of the Earth dominates and the gravitational effect is therefore effectively the same for both test objects, what is tested is their passive gravitational mass. The Earth is the mass generating the 1g field at the surface hence that field is G times its active gravitational mass. That is quite simple even in the Newtonian view. George Dishman (talk) 19:33, 7 July 2014 (UTC)
thread_title:  Active versus passive gravitational mass 

message: Just to clarify, the lead section of this article says that, "Mass....is the measure of an object's resistance to acceleration (a change in its state of motion) when a net force is applied." Is that not a property of an object, arising from its mass, called inertia? isn't mass the measure of the amount of mass in a substance? reply soon please.
P.S: i'm new to this editing stuff, so if this is a dumb question or something, cut me some slack.--RainbowsAndPonies (talk) 16:05, 19 January 2017 (UTC)
replies: text: Don't be discouraged, but...  mass is a (quantitative) physical property of an object (more generally, a system), as is energy, temperature, etc.  Inertia is a concept and a phenomenon that is (one of) the manifestations(s) of the physical property called mass. You might get (or find) a more complete answer to your question on Quora.com . DavRosen (talk) 13:43, 20 January 2017 (UTC)
thread_title:  Just to clarify 

message: There was a edit that replaced 1st sentence with this good-faith attempt to "correct" it to:
:In physics, mass is a property of a physical body. It is the measure of the quantity of matter an object contains. 
There are several problems with it:
# It does not correctly summarize the body of the article; please read the article again
# That's an old conception of mass and not the one that is accepted today
# Simply copying a definition from a dictionary (a tertiary source) is not adequate for wikipedia which is based on secondary sources from experts in the field (physics in this case)
# even when it was used as a common definition of mass, it was not a usable definition in practice since it provides no way to know, even in principle, whether "its mass is 1.2 kg" is a correct statement about a particular object; it is a non-falsifiable definition
# It defines a fundamental concept mass in terms of the less fundamental and less uniquely-defined concept of matter (pls. read that article too)
I'm undoing it back to what it had been:
:In physics, mass is a property of a physical body. It is the measure of an object's resistance to acceleration (a change in its state of motion) when a net force is applied.http://dictionary.reference.com/browse/mass
DavRosen (talk) 13:34, 20 January 2017 (UTC)
replies: text: Right. I'm new to this editing stuff, so guess I gotta learn.--RainbowsAndPonies (talk) 18:09, 20 January 2017 (UTC)
thread_title:  Undoing this good-faith new definition in 1st sentence: '''mass''' is a [[physical property|property]] of a [[physical body]]. It is the [[measure (mathematics)|measure]] of the quantity of matter an object contains. 

message: Of course we aren't required to match the articles in other languages, and these certainly aren't cite-able references, but I just thought it was interesting to see what 10 other groups of editors, perhaps much like ourselves, used for a "definition" of mass.  Of course some of these may have originated as translations from one of the other languages, but presumably most have been edited since then.
This was a couple of years ago. I used Google translate (automatically via Chrome browser), and then I edited results so they seemed to make sense to me in English (may not be an accurate translation) and just included as much as I thought was most relevant to how to define mass.  
The slashes separate some possible alternative translations (according to me as much as google) for some seemingly-ambiguous words.
;German
The mass is a property of matter and a basic physical parameter. It is given in the SI unit of kilogram. The symbol is usually m. Mass is an extensive quantity.
The gravity of a body is proportional to its mass. At the same time its mass determines the inertia with which it moves in reaction to forces. This dual role of mass belongs to the equivalence principle. Moreover, the mass of a body is equivalent to its energy in its rest frame, i.e. the two quantities differ only by the constant factor c2.
;Czech
Mass is a property of matter, which reflects the degree of inertial effects of matter, or measures the gravitational effects of matter. The equivalence of inertial and gravitational force effects is postulated by the general theory of relativity, and experimentally verified  with great precision[1].
Mass is similar to other characteristics of matter such as energy, electric charge, etc.
;Ukranian
Mass  - a physical quantity, which is one of the main characteristics of matter that determines its inertia, energy, and gravitational properties. Mass is usually denoted by Latin letter m .
Historical Review
...
In fact, Newton uses mass in only two ways: as a measure of inertia and as a source of gravity. Its interpretation as a measure of "quantity of matter" is nothing more than a visual illustration, and it was criticized in the 19th century as unphysical and meaningless.
;Finnish
Mass (Ancient μάζα, identification m) is the basic physics variable that describes, on the one hand, a body's inertia when a force acts on it, and, on the other hand, a body's ability to feel and cause gravitational forces.[1]
;Italian
The mass (from the Greek μᾶζα, "barley cake, lump (of dough)") is a physical quantity, that is a property of material bodies, which determines their dynamic behavior when subjected to the influence of outside forces.
In the course of the history of physics, particularly in classical physics, the mass was considered an intrinsic property of matter, represented by a scalar value (independent of direction), and which is preserved in time and space, while remaining constant within an isolated system. Furthermore, the term mass has been used to indicate two potentially distinct quantities: the interaction of matter with the gravitational field, and the relation linking the force applied to a body with the acceleration induced on it (see below paragraphs inertial mass and gravitational mass). However, the equivalence of the two masses was verified in numerous experiments (since the first ones which performed by Galileo Galilei)[1].
...
The intuitive pre-physical concepts of quantity of matter (not to be confused with the amount of substance, measured in moles ) are too vague for an operational definition
....  distinct from Newton's earlier theory (Newtonian dynamics) that introduces the mass in quantitative terms.
;Russian
Mass  (from the Greek μάζα) - a scalar physical quantity, one of the most important values ​​in physics. Initially (17th - 19th centuries), it characterized the amount of substance in the physical object, which, according to the ideas of the time, affected the ability of an object to resist applied force (inertia), and gravitational properties - weight.
In modern physics, the concept of amount of substance has a different meaning, and the mass is closely related to the concepts of energy and momentum (according to modern concepts - the mass is equivalent to the rest energy).  Mass is manifested in nature in several ways:
*Passive gravitational mass shows the force with which the body interacts with the external gravitational fields - in fact, this mass is a basis for measuring the mass by weighing in modern metrology .
*Active gravitational mass shows how the gravitational field is created by this very body - the gravitational mass appear in the law of universal gravitation .
*The inertial mass characterizes the inertia of the body and appears in one of the formulations of the second law of Newton. If an arbitrary force in the inertial frame of reference equally accelerates initially-motionless bodies, then these bodies are assigned the same inertial mass.
The gravitational and inertial masses are equal to each other (with high accuracy - about 10−13 - experimentally [1] [2], and in most physical theories - including certainly all experimentally-confirmed theories), ...
;Swedish
Mass is a physical quantity/property/indication of a material object. Mass exerts gravity, thereby affecting other surrounding lots and electromagnetic radiation (causing a change in the local space-time). Mass also means inertia, the property to exercise a movement resistance with respect to an actuation force, and determines the acceleration the force causes. These two properties of the material are sometimes called the weight mass and the inertial mass. Already Galileo is said to have demonstrated that they have the same value for a given body. A large mass under the influence of Earth's gravity falls to the ground as fast as a smaller mass. The larger mass both feels a greater attraction from the earth and causes a greater resistance to acceleration, and these differences will exactly offset each other. This is also called the equivalence between the inertial and weight mass.
Mass is measured in kilograms, according to the SI system (mass units).
;Polish
Mass - one of the fundamental physical quantities determining the inertia (inertial mass) and gravitational interaction (gravitational mass) of physical objects. Is a scalar. Commonly understood as a measure of the quantity of matter a physical object[In fact, you can only talk about the amount of substance (particles).]. In special relativity, associated with the amount of energy contained in a physical object. Most often marked with the letter m.
;Hungarian
In physics, the mass is a property of a body measuring the amount of matter and energy.  Unlike the weight, the mass always remains the same, wherever you are in the field. The invariant mass also does not depend on the reference system with which we look at the body.  The mass plays a central role in classical mechanics and related areas. The reference frame in relation to the inertia is called inertial. The mass appears in many forms of relativistic mechanics.
;Dutch
Mass is a physical quantity/parameter/variable/scale that indicates a property of matter. That property, which can be described as the amount of matter, manifests itself in two ways. On the one hand, matter is 'heavy', which means it is subject to gravity, and on the other hand, matter is 'sluggish', meaning that it resists change in motion. In the first case, we speak of gravitational mass; in the second case, of inertial mass. The SI unit of mass is the kilogram.  On earth, the mass of an object is usually determined by measuring its weight or by comparison with the weight of known masses.
DavRosen (talk) 22:33, 20 January 2017 (UTC)
thread_title:  Survey of [[mass]] in some other language wikipedii from a couple of years ago, just FYI 

message: It's easy to say that the units of mass are kilogram, slug or pound but how did  physicists determine / calculate the mass of an object first in such units while formulating F = ma = mg?2001:56A:7399:1200:1C6E:259D:5630:25AE (talk) 04:45, 5 February 2017 (UTC)
replies: text: For questions about the subject you can go to the wp:Reference desk/Science. Here we can only discuss the article—see wp:Talk page guidelines. Good luck. - DVdm (talk) 15:47, 5 February 2017 (UTC)
thread_title:  Units of Mass 

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thread_title:  External links modified