Proton's personal language crusade--shall we all agree to change how we talk?

[proton]

I was under the impression that electromagnetic waves are usually refered to as massless. Was I wrong?

Nah! Since you meant "rest mass" your statement was basically correct.

 

I used the term "basically" because I assume you had something very specific in mind when you said it, e.g. that the proper mass of a photon is zero. There are instances where one could say that "light" (as in multiple photons) has non-zero rest mass.

 

For example: when a physicist says that light has zero “rest mass” they are referring to the fact that since the energy of light is related to its momentum by the expression E = pc the norm of the photon's 4-momentum equal to zero. However if you had an ideal gas of photons, e.g. the cosmic microwave background radiation, then it can be said that proper mass density of such a gas is non-zero. If the amount of photons was finite and one were to integrate over all the photons then the proper mass of such a system is non-zero. This comes from the fact that for such a gas there is a frame of reference in which the momentum density of the radiation is zero but the energy density is non-zero. I know of at least one place that this is done in the physics literature, i.e. in Gravitation and Spacetime - Second Edition, by Ohanian and Ruffini, W.W. Norton & Company, (1994), pages 587 and 589. This is the chapter on the early universe. At that epoch the universe was said to be radiation dominated.

 

 

 

For example: if you have two photons which have the same energy, E, but are moving in opposite directions then the total momentum of the two photon system is zero. The proper mass of the two photon system (also known as the invariant mass) is not zero but has the value m = 2E/c²

 

Regarding the two definitions of the term "mass". A similar problem (i.e. the overloading of the term "mass") exists with the term "lifetime." When a particle physicist says that the lifetime of a free neutron is 15 minutes he is referring to the proper lifetime[/b], i.e. the lifetime as measured from a frame of reference in which the neutron is at rest. Some relativists use the term "lifetime" to refer to the lifetime of the neutron as measured from a particular frame of reference. As defined this way the lifetime is a function of the speed of the particle. So if a person were to say that the lifetime of a neutron is independent of the particle's speed then to determine whether or not he is correct one must determine what the person means by the term.

Is this directed towards me?

I had cperkinson in mind when I wrote that. . My apologies if there was any confusion over this. Edited June 20, 2009 by proton

[proton]

In the last 10 years or so, and even longer ago in alot of cases, the concept of relativistic mass has been removed.

That is widely held misconception among both physicists and laymen alike. For this reason, Don Koks, the physicist who maintains the Relativity FAQ, updated the FAQ on relativistic mass to reflect the actual usage. The (updated) FAQ is at

http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html

 

Another physicist, namely Gary Oas of the “Education Program for Gifted Youth” at Stanford University, wrote an article on the use of relativistic mass. The article is called

 

On the abuse and use of relativistic mass. It is online at http://arxiv.org/abs/physics/0504110

 

If you feel the need to post an objection to each instance of the use of relativistic mass as it arises then may I suggest that it would be more prudent to simply list those two URLs and let the reader decide for themselves rather than create a new post claiming that it is the "prefered" term?

 

By the way. People have preferences, not discussion forums. What you said might be valid if everyone that posts here both now and in the future, prefers rest mass in all instances. But that is not the case.

 

I'm pretty sure that nobody wants a debate to be sparked every time someone uses or mentions relativistic mass. Not only would it derail a thread but it would be irritating to the person who uses it. All that merely because we have a different opinion. That would be unfortunate, wouldn't you agree? Also, suggesting that people only use rest mass is not a good idea. They may never have the occasion to hear about or learn about things like the inertia of stress or the fact pressure is a source of gravity or that these two phenomena are related and plays an important role in modern cosmology.

 

You argue that It is more common to consider just one mass.. It's certainly more common for the particle physicists to use it but that is not the case for cosmologists. A perfect example is the concept of Dark Energy and its role in both inflation and the accelerating expansion of the universe. The term Dark Energy is defined in the glossary of Schutz's text Gravity from the Ground Up (a textg which relies heavily on the concept of relativistic mass).

dark energy - Observations suggest that the expansion of the Universe is presently accelerating, and theories of inflation also require a period of rapidly accelerating expansion. To produce the acceleration one needs a physical field that has negative pressure, large enough to make the active gravitational mass negative and produce an anti-gravity effect. Fields that have positive energy but large negative pressure are called dark energy.

Peebles also uses the term active gravitational mass as well as passive gravitational mass in his (as does Schutz) his cosmology text. Schutz also uses the term passive gravitational mass.

 

Cameron - I mentioned what I did because the concept is both still used and very important. Since I don't know you I am unfamiliar with your level of understanding of physics and don't know what you may or may not be interested in. I assume that you'd find it interesting that inertia has stress, right? I guess that because I myself find it fascinating as do most people when they first learn about it.

 

 

Relativity textbooks and journal articles, some of the texts being dvanced, by some well-known and respected physicists, have been published within the last ten years that utilize relativsitc mass. I myself find it to be the most logical, if not the only logical way, to define mass. In recent years there have been some very interesting papers in the American Journal of Physics on the more complex issues regarding the concept of mass. I found the following articles quite interesting

 

The mass of a gas of massless photons, H. Kolbenstvedt, Am. J. Phys. 63(1), January 1995

Using minimal formalism, we demonstrate that the massless photons, constituting the radiation in a cavity, contribute to the mass of the mass of the cavity in agreement with Einstein's mass-energy formula. We assume that a photon has energy and momentum related to frequency by E = hv, p = hv/c. Restricting velocities to nonrelativeistic values, we impart a uniform acceleration to the cavity. Reflection from a moving mirror produces a Doppler shift, and thus the momentum delivered to the front and rear walls can easily be calculated in the laboratory frame. A simple application of F = ma leads to the usual conclusion that the mass of a gas of total energy U is U/c2. An alternative argument based on calculations.

Let me ask you this - Before I explained that a gas of photons has rest mass would you have thought it to be true?

 

The inertia of stress, Rodrigo Medina, Am. J. Phys. 74(11), November 2006

We present a simple example in which the importance of the inertial effects is evident. The system is an insulating solid narrow disk whose faces are uniformly charged with equal charges of equal magnitude and opposite signs. The motion of the system in two different directions is considered. It is shown how the contribution of energy and momentum of the stress that develops inside the solid to balance the electromagnetic forces have to be added to the electromagnetic contributions to obtain the results predicted by the relativistic equivalence of mass and energy.

 

Apparatus to measure relativistic mass increase, John W. Luetzelschwab, Am. J. Phys. 71(9), September 2003

An apparatus that uses readily available material to measure the relativistic mass increase of beta particles from 204T1 source is described. Although the most accurate analysis uses curve fitting or a Kurie plot, students may just use the raw data and a simple calculation to verify the relativistic mass increase.

Simply saying that every occurance of the term "mass", that you will encounter in your studies in physics, means "rest mass" is quite misleading, wouldn't you agree?

 

Also note that what I said also pertains to both active gravitational mass and passive gravitational mass.

Edited June 22, 2009 by proton

[Martin]

Hi proton.

 

Trying to reform people's language is not science, but it can be very interesting. I like you because you are smart and articulate, but it is inefficient if we start meaning different things by basic words.

 

We have been thru this before and settled on mass = rest mass.

 

We should not change until we have all discussed this and decided.

 

You want us to use "mass" to mean E/c^2. We should not change to that without a vote by the science mods or a decision by people like Swansont and Klaynos etc. Or some kind of deliberate decision process.

 

If we decide not to change our common usage of the word, then you have to abide by that.

 

================

 

I noticed in cosmology just now you were talking like an authority but saying something that struck me as nonsense. You are new. Don't assume you know everything and can instruct newcomers. Wait, take it easy.

You are bright and articulate and impressive but you also seem to be green, like an undergraduate. That would be my guess. It doesn't matter. 50 years old guys can still be naive and promote non-standard cosmology.

=================

 

From time to time we get these fervent reformers, missionary types. They have a cause they are battling for. The Milne universe, relativistic mass, whatever.

It's a cheap way to feel important. Take on a minority cause, like about word usage, and learn all the arguments. And then whereever you go you feel everybody else is wrong and you need to preach the true religion to them.

 

The problem is when you mess with basic language you disrupt other people's communication and confuse newcomers. Here it is important for us to all talk more or less the same, with the same basic dictionary.

We can't have two or three kinds of mass, butterscotch mass, chocolate-relativistic mass, transverse mass, longitudinal mass whatever. We have to have one mass concept.

 

Your reform zeal may be right! That guy Koks, who is essentially a nobody with a PhD who has written one book, since he got his PhD in Australia in 1996, that guy Koks might be right. It is not physics. It is just a crusade to make us talk different for our own good. But maybe it is right.

Maybe nobody should smoke or drink alcohol and it would be "convenient" for them. You are arguing that it would be more convenient if we said mass to mean E/c^2.

 

OK I grant it. It might be. But before we all change we have to decide we like to talk different, and make the switchover coherently.

 

So I am being as nice about this as I can. Here is a forum where you can argue for relativistic mass. Do not promote semantic reform in the real science forums. Make your case here. We can all discuss it and decide what course we want to take. Any way is fine with me personally. It just means speaking a different language.

 

The issue is not physics, its our choice of words to describe and explain physics. I find the discussion of this more boring each time we go thru, but I think you are a bright young person so please make with the rhetoric about your semantic mission.

[JohnB]

"chocolate-relativistic mass"??

 

The faster I go, the more chocolate I have?

 

I like physics!

[J.C.MacSwell]

"chocolate-relativistic mass"??

 

The faster I go, the more chocolate I have?

 

I like physics!

 

The more chocolate I eat, the relatively fatter I get.

 

I hate biology!

[proton]

Hi proton.

 

Trying to reform people's language is not science, but it can be very interesting. I like you because you are smart and articulate, but it is inefficient if we start meaning different things by basic words.

 

We have been thru this before and settled on mass = rest mass.

I have no desire to change what terms people use. I only object to when people try to change mine because its fashionable. You won't be confusing newcommers because they don't know what you've chosen for them yet. Sinced I choose not let people choose how I explain things it's best I leave. Thanks.

[iNow]

Just in case you're using your own special definition of "leave" which differs from that used by the rest of us, can you explain what you mean by that so as to avoid any confusion?

[swansont]

I have no desire to change what terms people use. I only object to when people try to change mine because its fashionable. You won't be confusing newcommers because they don't know what you've chosen for them yet. Sinced I choose not let people choose how I explain things it's best I leave. Thanks.

 

It's not your choice to make, really, if you want to communicate effectively. If what I mean by mass is different from what you mean by mass (or whatever term you wish to choose), then the discussion grinds to a halt right there. Common terminology is like the "handshaking" the fax machine (or any other communication protocol) does at the beginning of the transmission. Without it you are lost. You are Humpty Dumpty, saying, "When I use a term, it means whatever I choose it to mean — "nothing more, and nothing less," and then it's impossible to discern what was actually said, because none of the words are meaningful to anyone else.

 

And you'll run into the problem wherever you go.

[proton]

If what I mean by mass is different from what you mean by mass (or whatever term you wish to choose), then the discussion grinds to a halt right there.

You misunderstood my comments. Perhaps Martin did as well. If so then perhaps I won't need to leave. In the mean time I challenge you to find a post I wrote in which I was not 100% clear as to what I meant by “mass.” Recall what I said to cameron.

You must be referring to rest mass. ...

Note: Some people refer to this m = E/c² as relativistic mass. Other people refer to it as inertial mass.

One simply could not have misunderstood what I meant. I do not, nor have I suggested that I will, use "mass" unqualified to mean "relativistic mass." I was quite clear as to what I said. I merely find it to be pain in the butt to keep writing relativistic mass everytime I refer to it. I feel that its easier to write mass and simply note what I mean by it. That's the reason particle physicists use the term mass unqualified to refer to proper mass, i.e. it's simply too unwieldy to keep using the "proper" qualifier.

 

Let's be clear on what I said. I made the following points

 

1) The notion that concept of relativistic mass has been removed from physics is a widely held misconception among both physicists and laymen alike.

 

2) If someone objects to someone using relativistic mass then they shouldn’t start a debate about it but merely post the two URLs and suggest they read them.

 

3) It is not uncommon to see mass used in other contexts such as active/passive gravitational mass. This seems to be a widely used term in cosmology. Even in Schutz’s GR text he states that mass and energy are the same thing. This is the essence of relativistic mass. Also the concept of the inertia of stress is becomming more visible in the relativity literature. This is not refected in the simply use of "rest mass" to refer to a property of point particles.

 

4) I mentioned instances where authors refer to radiation having "mass" so that newbies won’t be confused about it if/when they encounter it.

 

Martin seemed to think that I was attempting to “reform” people’s language in physics. That is the furthest thing from the truth and there is zero justification for such an accusation based on what I posted. Perhaps his mistake in that respect confused you. I simply don’t care what people mean by “mass” since its always clear from the context what they mean. Newcomer’s should have the maximum amount of information at their disposal to prepare them for what they might encounter in the future. Schutz’s GR text is one of the most highly used, respected, and recommended texts in GR today and Schutz does say that energy and mass are the same thing and he doesn’t use the term relativistic mass. Ohanian refers to the mass density of radiation. I was making these points clear for Cameron. We have no idea what Cameron wants to learn. If/when he tells me that he doesn't want to know anything beyond rest mass then I will never mention it to him again.

You want us to use "mass" to mean E/c^2.

You made many claims in your last post which are quite far from the truth. I never suggested that I want people to use that.

I noticed in cosmology just now you were talking like an authority but saying something that struck me as nonsense. You are new. Don't assume you know everything and can instruct newcomers.

I'm a bit dismayed that you feel the need to get personal here. What you claim is not true. I may be new in this forum but I'm far from being new to physics or to discussion forums. I don’t claim to be an authority of anything either. You read something into my responses that was never there. I know many physicists' date=' a few of which are authorities in their field either. But most physicists I know would never make such a claim.

 

For example; what field are [i']you[/i] an authority in?

 

Being educated and knowledgeble in a field does not make one an authority and I've made no such inferences or claims. I’ve been a physicist for 20 years. I've chosen my field o study/research to be relativity almost 20 years ago. I’ve been discussing relativity on the Internet for a good 13 years too so I know when newbies get confused.

You are bright and articulate and impressive but you also seem to be green' date=' like an undergraduate.

[/quote']

Far from it. I graduated undergrad 20 years ago. I did some graduate work after that. I’m far from being green in any sense of the term. What is it that led you to that false conclusion?

 

You comments on Dr. Koks are a bit unfair. You claim that he's a nobody". What makes a person a "nobody" in your opinion? Is swansont a nobody? How many physicists are there in the world? How many of them do you recognize by name? Did you refer to Koks as a nobody merely because he's written only one book? How many books have been written by the physicists who post here? I know of few famous physicists who have never written any book. Don maintains the physics FAQ. I assume he was chosen for this task because he's good at what he does. Having communicated with him in e-mail its my opinion that he's quite bright.

 

I'm also curious as to why you only mentioned Don and none of the other authors I mentioned?

From time to time we get these fervent reformers' date=' missionary types. They have a cause they are battling for.

[/quote']

You misrepresented me once again. I have zero desire to change the way people use terminology. I never have and I never will. Sure, I may argue that one way is more logical than another but that's about it. Different people think differently and they should use whatever makes them more creative. Trying to convice people to change their word usage is always a waste of time. However if you want to see people try to force others to use what they do you can find a lot of that in the physics journals. You don’t need me for it.

 

Also, when I responded to Klaynos I never suggested that people use what I use or use "mass" to mean relativistic mass" and not be clear about it. In fact I never wrote anything which even hinted that I want people to use rel-mass.

but I think you are a bright young person so please make with the rhetoric about your semantic mission.

Young? Gee! Thanks. But I’m almost 50 yo. And please stop making false accusations like this. I have no mission. Just because I don't want people to force their views on be does not mean I want to force mine on others.

Common terminology is like the "handshaking" the fax machine (or any other communication protocol) does at the beginning of the transmission. Without it you are lost. You are Humpty Dumpty' date=' saying, "When I use a term, it means whatever I choose it to mean — "nothing more, and nothing less," and then it's impossible to discern what was actually said, because none of the words are meaningful to anyone else.

[/quote']

Again, you seem to have misunderstood what I wrote. I never said I’d use “mass” to mean relativistic mass and not say so. I said that physicists use other concepts than rest mass and if I’m prohibited from speaking of any concept besides rest mass then I wouldn’t want to keep posting here. How did you come to that conclude otherwise?

 

There's one last point I'd like to make and that has to do with multipole meanings of other terms. If I asked you to post the definition of momentum, would you all give the same definition? For the sake of argument let's give that a try. In our daily lives people use the same word to mean different things. E.g. I find the use of the term organic to be irritating. A chemist uses the term to refer to carbon hydrocarbon compounds. But in the supermarket it refers to food which has been produced according to certain standards.

 

If I seemed testy in my responses above then I humbly appologize. It's just that people totally misread what I wrote and have made some very wrong assumptions about me and I very much dislike it when people get personal.

Edited June 28, 2009 by proton

[GutZ]

When it comes to arrive at the same conclusion, there is a point where the sake of being correct is less effective than acceptance.

[J.C.MacSwell]

Just a question: (I think we have discussed this before somewhat differently)

 

Say you had a "black box" or better yet "black sphere", in space, and you cannot look inside.

 

Assuming it is at rest, how do you measure the mass of it?

 

 

Would you consider your answer to be the mass of the sphere, or the "rest mass" of the sphere, or the sum of the "relativistic mass" components of the sphere?

Edited June 29, 2009 by J.C.MacSwell

[proton]

When it comes to arrive at the same conclusion, there is a point where the sake of being correct is less effective than acceptance.

I don't understand your point. Can you clarify please.

---

Merged post follows:

Consecutive posts merged

Just a question: (I think we have discussed this before somewhat differently)

 

Say you had a "black box" or better yet "black sphere", in space, and you cannot look inside.

 

Assuming it is at rest, how do you measure the mass of it?

That depends on a few things. It most of all depends on how you define mass. Then it depends on what aspect of mass you're referring to. It also depends on the particular object. For example; you wouldn't measure the mass of a black hole the same way you'd measure the mass of an electron. The relativistic mass also depends on the orientation of the body relative to its velocity since the rel-mass is a function of the stresses that its under. Typically the idea of mass is its measurement of its resistance to changes in momentum. This is what's known as Weyl's definition of mass. I.e. its the m in p = mv. This is close to being how Newton defined mass too.

Would you consider your answer to be the mass of the sphere, or the "rest mass" of the sphere, or the sum of the "relativistic mass" components of the sphere?

It depends on the definition of mass. For example; if you're interested in the active gravitational mass of the body, i.e. the mass as the source of gravity, then you're measuring how the body generates a gravitational field and how it affects the geodesics of bodies moving in its field. The gravitational field of a body is a function of its velocity so the faster it's going the stronger its gravitational field. It's a bit more complex than that though. There was an article on this subject in the American Journal of Physics. The article is called

 

Measuring the active gravitational mass of a moving object, D.W. Olson and R.C. Guarino, Am. J. Phys. 53(7), July 1985. The abstract reads

If a heavy object with rest mass M moves past you with a velocity comparable to the speed of light, you will be attracted gravitationally towards its path as though it had an increased mass. If the relativistic in active gravitational mass is measured by the transverse (and longitudinal) velocities which such a moving mass induces in test particles initially at rest near its path, then we find, with this definition, that M_rel = [math]\gamma[/math](1 + [math]\beta[/math])M. Therefore, in the ultrarelativistic limit, the active gravitational mass of a moving body, measured in this way, is not

[math]\gamma[/math]M but is 2[math]\gamma[/math]M .

All I'm saying here is that I don't want to be in a position where I'm prohibited from mentioning/discussing articles like this. If the forum bans all mention of the concept of rel-mass then it is that which I object to. I also think that if its okay to discuss rel-mass when someone is interested in it then it would be a bit irritating to see someone start in with a debate everytime it comes up. I understand that people can be fanatical about getting rid of all mention of rel-mass so its for that reason I mentioned those two URLs.

 

I really dislike arguing about semantics. All i want to know is whether I'll be prohibited from discussing concepts of mass other than rest mass.

Edited June 29, 2009 by proton
Consecutive posts merged.

[iNow]

You won't be "prohibited," but you'll be noted to be outside of the mainstream, since practically no physicist worth his salt refers to "relativistic mass" any more.

[proton]

You won't be "prohibited," but you'll be noted to be outside of the mainstream, since practically no physicist worth his salt refers to "relativistic mass" any more.

Frankly I'm not interested in such an opionions since it's dead wrong. Read the article I linked to which did a study on its usage in the modern physics literature.

 

I assume that you used the term practically so that you wouldn't be accused of claiming that Bernard Schutz and Wolfgang Rindler are not worth their salt?

 

By the way, for a suggestion to have any worth one should know the source. Are you a physicist? Have you ever done a study to determine what percentage of physicists use relativistic mass?

 

Please folks. Let's not get personal. Please stick to the subject matter. Discuss the subject and not me. It's very distasteful to get so personal.

Edited June 29, 2009 by proton

[J.C.MacSwell]

You won't be "prohibited," but you'll be noted to be outside of the mainstream, since practically no physicist worth his salt refers to "relativistic mass" any more.

 

What term would you use? Or do you not find the concept useful at all?

[iNow]

Frankly I'm not interested in such an opionions since it's dead wrong. Read the article I linked to which did a study on its usage in the modern physics literature.

 

I assume that you used the term practically so that you wouldn't be accused of claiming that Bernard Schutz and Wolfgang Rindler are not worth their salt?

 

By the way, for a suggestion to have any worth one should know the source.

The concept on which we should focus is whether or not it's useful. In response to that, I will say, yes, sometimes relativistic mass is useful. However, the majority refer to "rest mass" when they use the word mass in their description.

 

 

Here's a good discussion about the issue:

 

http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html

While rest mass is routinely used in many areas of physics, relativistic mass is mainly restricted to the dynamics of special relativity. Because of this, a body's rest mass tends to be called simply its "mass".

 

<...>

 

While relativistic mass is useful in the context of special relativity, it is rest mass that appears most often in the modern language of relativity, which centres on "invariant quantities" to build a geometrical description of relativity. Geometrical objects are useful for unifying scenarios that can be described in different coordinate systems. Because there are multiple ways of describing scenarios in relativity depending on which frame we are in, it is useful to focus on whatever invariances we can find. This is, for example, one reason why vectors (i.e. arrows) are so useful in maths and physics; everyone can use the same arrow to express e.g. a velocity, even though they might each quantify the arrow using different components because each observer is using different coordinates. So the reason rest mass, rest length, and proper time find their way into the tensor language of relativity is that all observers agree on their values. (These invariants then join with other quantities in relativity: thus, for example, the four-force acting on a body equals its rest mass times its four-acceleration.) This is one reason why some physicists prefer to say that rest mass is the only way in which mass should be understood.

 

<...>

 

In the final analysis, the history of relativity, with its quotations from those in favour of relativistic mass and those against, has no real bearing on whether the idea itself has value. The question to ask is not whether relativistic mass is fashionable or not, or who likes the idea and who doesn't; rather, as in any area of physics notation and language, we should always ask "Is it useful?"

 

The article offers good reasons for and against its use, and argues quite well that there are good times to use relativistic mass. Where I personally land on this issue is with a preference for rest mass, since it is the same in all reference frames. If you disagree, then so beit. Just recognize that... if you say mass... and you wish to refer to relativistic mass when you do... that you must clarify that it is "relativistic mass" to which you are referring, since the word "mass" is used to describe "rest mass" in the vast majority of cases when written in the literature (again, unless otherwise noted).

 

 

 

Discuss the subject and not me. It's very distasteful to get so personal.

Would you please use the quote feature to indicate where precisely it was you think I was "disgraceful" and where I made the subject "about you" and "personal?" I don't recall ever doing any such thing, in which case you'd be guilty of a strawman.

Edited June 29, 2009 by iNow

[proton]

The concept on which we should focus is whether or not it's useful.

That is subject to opinion.

 

You didn't answer my question. Are you a physicist?

[iNow]

That is subject to opinion.

 

You didn't answer my question. Are you a physicist?

 

Aren't you the one asking to avoid making things personal? I find your question completely irrelevant, and shows a degree of hypocrisy/double standard.

[proton]

Aren't you the one asking to avoid making things personal? I find your question completely irrelevant, and shows a degree of hypocrisy/double standard.

I asked people not to get personal. I don't get personal and I expect others not to. Address the physics and not who is posting the physics.

 

But that has nothing to do with qualifications. Ad hominem attacks are a completely different subject that qualifications. I asked you if you were a physicist because I wanted to know what makes you qualified to make such a claim. Simply reading other people's claims on forums like this cannot inform anyone as to what is actually used by physicists. My question is quite relevant since if you're not a physicist then I have no reason to take anything you say on such claims seriously. Someone who is a physicist has the minimum qualifications to know whether physicists use a concept or not or what is found in various physics journals.

 

So fine. You're not a physicist. It's clear from your responses anyway, i.e. all ad hominems and nno physics content. Frankly I find your insulting attitude rather disturbing. It's a shame that such a poor attitude is tolerated.

Edited June 29, 2009 by proton

[iNow]

i.e. all ad hominems and nno physics content. Frankly I find your insulting attitude rather disturbing. It's a shame that such a poor attitude is tolerated.

Erm... where exactly did I ad hom or insult you? Are you sure you're reading MY posts?

[Martin]

I don't want to get into an argument, but I would like to introduce something to think about.

 

Of course historically it could have gone either way. The original Newton idea of mass was inertia which is how many units of force you have to apply to get a unit of acceleration (like "one meter per second per second")

It is very like the idea of resistance in basic electric wiring, how many volt units do you have to apply to get one unit of current ("one coulomb of charge flowing by per second")

 

This idea of inertia is very simple and useful. And then there's Newton G which if you multiply an inertia by it tells the gravitational attractiveness of the thing.

 

Anyway if you study mass in equations you see that the unit is always equivalent to a unit inertia (like "one newton of force per each (meter per second per second) unit of accel")

 

We at SFN have liked to keep it simple and have just one concept of mass, and we go the way the perceived majority physics community goes, which is to keep mass being Newton's idea of inertia.

 

However in the early 20th certain physicists thought would be nice to get rid of that idea and have the mass scale be just a rescale of energy, mass would be E/c^2. But this would no longer correspond to inertia except in certain special cases. Mostly it would just be another way of quantifying the total energy. Which is fine and dandy. It could have gone that way.

We could be happy speaking French, or speaking Italian. "Ciao bella! C'est magnifique!"

 

Only some people think they would be more happy to have two separate meanings of mass (and everyday have to explain the difference to some poor soule) or they think they would be happier if everybody meant E/c^2 instead of inertia.

 

The central point, the catch (and I hope Swansont will correct me if I am wrong) is that a moving object does not have a welldefined directionless inertia.

 

If an object is at rest then it does not matter which direction you shove. You always get the same "resistance", the same cost of units of force per unit of acceleration.

 

But if an object is moving then this turns out not to be true. You get more or less acceleration depending on whether you shove along the direction it's going, or you shove crossways. If you shove in exactly the right direction then indeed the inertia will turn out to be E/c^2, which Pete liked to be the mass, and which Proton also liked to be it.

If you don't shove in the right direction then it is not E/c^2.

 

In fact, in the majority language, the popularized equation E = mc^2 is only true for objects at rest. There is a slightly more complicated equation for when it's moving.

And in the majority language, the mass of an object is defined to be it's inertia at rest.

Maybe this could become an informative discussion and not some personal theater hero action movie martyr-for-a-cause episode with hand-to-hand duels and bickering and whining or whatever. I can't remember how it played out when we did this before. But I would like it more impersonal and informative.

And if I'm wrong about the directionality of inertia, for moving objects, please correct me.

==============================

 

There's actually some non-trivial content here, I think. Not just controversy soap-opera. It has to do with measurement and standards.

there is a branch called metrology. How do you measure voltage? Length? force? time? current? the NIST hires a lot of metrologists It is a very interesting professional line of work. Well a nice thing about inertia is that it is basic and observable.

There is a clear operational definition. You shove and you watch and gauge the acceleration.

 

But fundamentally no one knows what energy is. Feynman gave his famous "Dennis the Menace" talk about this. We keep finding new types of energy.

So there is no operational definition for that minority mass concept E/c^2. Because at a very primitive basic caveman level you cannot say what E is. But inertia is an operational primitive idea. So if you are going to construct a system of physical quantities this kind of simple defined primitivity might be a consideration.

Ugh! Will hit with club! See how fast move!

Edited June 29, 2009 by Martin

[proton]

We at SFN have liked to keep it simple and have just one concept of mass, ..

Bad idea.

...and we go the way the perceived majority physics community goes, which is to keep mass being Newton's idea of inertia.

So because 60% of modern texts don't use rel-mass you want to force 100% of the people here not to? Unwise.

 

I asked a very clear question and have not yet gotten an answer; are you going to prevent people from talking about other concepts of mass.

 

Do you understand why I mention what I do? It's for one single reason - to prepare people for what they will read in the physics literature and for no other reason. I mentioned to cameron what I did about mass of light because he might want to learn GR or cosmology one day and that's what he'll encounter. I don't wish to post at a forum where people are banned from talking about certain articles that appear in the American Journal of Physics or various physics texts (even advanced modern ones) because people here are ingorant of such usage.

Edited June 30, 2009 by proton

[mooeypoo]

Bad idea.

It is? Okay, let me demonstrate something, proton. I will your next sentence and use my own terms in it:

 

Original:

So because 60% of modern texts don't use rel-mass you want to force 100% of the people here not to? Unwise.

 

Mine:

So because 60% of mayan books don't use rel-mass you want to mother 100% of the people here not to? Unwise.

I consider the mayan culture pretty modern for its time, so I don't see a problem using "mayan" instead of what you consider "modern". Texts are also more specifically defined as books, so I will be using books instead. The term 'force' is used in F=ma, and 'ma' sounds like the abbreviation to "mom" so I will be using "Mother" instead.

 

Now. Can you talk to me, understand what I'm saying, and respond properly if I do any of the above, specifically if I would've done it *without* putting up the index of what I changed and to what after?

 

 

I asked a very clear question and have not yet gotten an answer; are you going to prevent people from talking about other concepts of mass.

The entire point of this thread is that your question was NOT clear.

We have no problems letting people discuss other concept of mass, but you will need to define them first, so we can all understand what you're talking about. Otherwise we will assume (naturally) that when you say "mass" you mean what everyone *agrees* mass to be, and not what you want it to be.

 

Redefine the term, or use a different one, either way, if you want a mutual discussion you will need to cooperate with the "mutual" part of it; the language.

 

 

Definitions exist so we can know what we're talking about. To be quite honest, proton, you don't "choose" to use them or not, you have to use them otherwise no one understands what you're talking about. If you want to use "mass" in a different definition than the one that is accepted, you have 2 options:

(1) Define, at the top of your post/paper that every time someone sees the word "mass" they should actually consider it as rest mass (or relative mass, or whatever is), so people can understand you.

(2) Switch to a subject that is dealing with pseudoterms and definitions, like philosophy.

 

Otherwise, you're going to have to stick to the norm, or no one with understand you.

[proton]

That was a very poor counter example mooeypoo. I will not get dragged into a debate. I asked one question and am awaiting a response from the moderators. What you personally choose to do is your buisness.

The entire point of this thread is that your question was NOT clear.

What don't you understand?

We have no problems letting people discuss other concept of mass, but you will need to define them first, so we can all understand what you're talking about.

Nothing I've ever posted was anything but 100% clear about what I was talking about. In those instances where I used m to mean relativistic mass I stated so explicitly. I always have and I always will. I've already stated that above. Did you not read it?

 

As far as definitions go, what does the term momentum mean? I asked this above and got no response.

Edited June 30, 2009 by proton

[mooeypoo]

But if you're using mock language and refusing to explain yourself, we don't understand your question.

 

If it was all clear, this thread wouldn't have been open. You talk your own language instead of the conformed language of physics.

 

Good luck with that?