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Author Topic: How does mass increase at higher speeds?  (Read 45737 times)

Offline yor_on

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Re: How does mass increase at higher speeds?
« Reply #150 on: 29/01/2013 17:43:57 »
Because if you consider it from observer dependencies it seem to me that you either have to assume 'something' unchanging, being the platform from where observer dependencies are created, or else make a assumption that all observers have a own 'universe'. And that, it its turn, comes from the fact that we use repeatable experiments to define 'reality'. That's the way we set it up physically. And if that thinking is correct, that your experiments will tell you what is true and what is wrong. Then the universe I see, and experimentally verify as me having a certain distance to some other body for example, will differ from yours according to relativity.
==

Locally I would say that we all have a equivalent arrow, as proved when being in a same frame of reference with what you measure. From a point of locality we're all 'equal' :) regarding the arrow. The same goes for distances. From that point of view the universe consist of one unchanging base, same for us all, observer dependencies created through 'c' (combined with energy/mass/'motion'). But the fact is that your reality is defined through your experiment, so finding someone else's watch to go slower than yours relativistically and experimentally must be true to/for you.

So locality is where we're all equal as I see it. And where all arrows are equivalent.
And one more thing, accelerations.

The weirdest example, and proof, of a 'change' that I know. Everything that exist seems to me to somehow (be able too?) accelerate? What is a virtual particle? If it is not there, but then is, can you see that as a 'acceleration' from a probability into a 'outcome' ('real' particle) ?
« Last Edit: 29/01/2013 19:03:03 by yor_on »
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #151 on: 29/01/2013 23:53:20 »
Quote from: JP
I wasn't the one telling posters that proper mass has little or nothing to do with the definition of mass!
Inertial Mass - Defines momentum. Quantifies resistance to changes in momentum.
Passive Gravitational Mass - The property on which gravity acts
Active Gravitational Mass - That which generates a gravitational field.

Those are what characterizes mass, by definition. How does invariant mass simply fit in there? We all know that it does, but in what direct manner?
 

Offline JP

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Re: How does mass increase at higher speeds?
« Reply #152 on: 30/01/2013 05:01:14 »
Mass is the length of the energy-momentum four vector, no matter how fast you're going.  This satisfies F=ma and p=mv (with some problems with photons, I believe), and reduces beautifully to classical mass in the relativistic limit when three of the vector's components become negligible.  There's something to be said for the elegance of this concept.

The last two of your points have to do with general relativity, so I'd add that relativistic quantum mechanics uses invariant mass, in the place of where mass would enter in the non-relativistic equations, mostly because of the simplicity with which it enters the equations in place of non-relativistic mass when promoting 3-vectors to 4-vectors.  This isn't as elegant or long-standing as "it generates gravity," but that's because we happened to be born into a world where we experience gravity daily, and not because it's any less fundamental.  If we were born as quantum objects, we'd find it very fundamental indeed!
 

Offline waytogo

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Re: How does mass increase at higher speeds?
« Reply #153 on: 30/01/2013 09:38:10 »
I'm sorry if this is a dumb question but physics is not really my area. I've been listening to the CBC Massey lectures by physicist Neil Turok, which I quite like. Anyway, when he talks about mass increasing at higher speeds, how does that happen? Is there actually an increase in the amount of matter or atoms or particles? Or does it just take more force to accelerate it? I had always thought that mass and matter were the same thing.

Hi there, Its NOT a dumb question, I still have no answer of that. Anyway, you have to consider that its just a ancient theory and new ones should be replaced in next decades.
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #154 on: 30/01/2013 18:51:51 »
Mass is the length of the energy-momentum four ..
That is merely an equality relating inertial energy, momentum and proper mass. It's not a definition of mass, at least it shouldn't be. The onlyway you can arrive at that relationship is by relating inertial mass to velocity of an isolated system. It doesn't work in general by the way. It only works for competely isolated systems. It wouf fail for a drop of water in an electric field. The definitions are as I gave them above. They are what characterize mass.
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #155 on: 30/01/2013 18:53:01 »
I'm sorry if this is a dumb question but physics is not really my area. I've been listening to the CBC Massey lectures by physicist Neil Turok, which I quite like. Anyway, when he talks about mass increasing at higher speeds, how does that happen? Is there actually an increase in the amount of matter or atoms or particles? Or does it just take more force to accelerate it? I had always thought that mass and matter were the same thing.

Hi there, Its NOT a dumb question, I still have no answer of that. Anyway, you have to consider that its just a ancient theory and new ones should be replaced in next decades.
Its hardly ancient since its found in even the most recently published textbooks.
 

Offline JP

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Re: How does mass increase at higher speeds?
« Reply #156 on: 30/01/2013 19:17:09 »
The definitions are as I gave them above. They are what characterize mass.

Ah, the old "I chose to characterize mass by these definitions, therefore they characterize mass" argument.  That works for the definition I gave, too.  :) 

I thought up another interesting question about invariant vs. inertial mass, though.  I don't understand the Higgs mechanism enough to give a definite answer, but from the descriptions I've heard of it by scientists, it explains inertial mass in terms of a field, and the strength of a particle's inertial mass by the coupling to that field.  That could mean a coupling constant would probably be the best definition of inertial mass, which seems like invariant mass.  The Higgs mechanism could provide a means to explain inertial mass in terms of a single constant plus a field of nature.  If that's true, invariant mass is presumably more fundamental than inertial mass, which is another good reason to consider it a definition of mass.  This is speculation, so take it with a large grain of salt unless a Higgs specialist on the forum wants to confirm or refute it.  :p

This horse, however, has been beaten to a fine paste at this point.  Arguing our opinions on the internet doesn't change the fact that all these definitions  are valid extensions of the concept of classical mass, and all find widespread use, albeit in different fields of study.  I guess we'll keep on arguing until someone figures out quantum gravity and ties all the concepts of mass into one fundamental definition.
« Last Edit: 30/01/2013 19:21:57 by JP »
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #157 on: 31/01/2013 22:22:42 »
Quote from: JP
Ah, the old "I chose to characterize mass by these definitions, therefore they characterize mass" argument.  That works for the definition I gave, too.  :) 
Not really. It was never I who chose them. They've been around long before I was born, and still are.
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #158 on: 02/02/2013 00:13:07 »
Quote from: JP
I wasn't the one telling posters that proper mass has little or nothing to do with the definition of mass!
I just realized that you misquoted me here. I never said that. What I said was that proper mass has little or nothing to do with the defining characteristics of mass.

I would never say that it had nothing to do with mass, never! The reason being, that itís simply not true. Did you miss that part or were you confused? [we all have our days :) ] I think you mistook me for saying that proper mass has nothing to do with the definition of mass. Thatís now what I said simply because I don't believe it to be. The  defining characteristics being the whole point I was making.

If you'll notice, I do my best to avoid getting into discussions about the definition of mass. There's just way too much to the concept than can be gotten to in a discussion in a discussion forum. In fact it was for just that reason that wrote that article on the subject. Everything I believe regarding the concept of mass is in the paper at http://arxiv.org/abs/0709.0687

I recommend that you read it. Iíd enjoy your feedback and any comments or constructive criticism that you might have on it.

I can pretty much guarantee that every aspect about mass that you could come up with are tell me about mass is contained in that paper, including the most obvious notion that the ďmassĒ of a particle is the magnitude of the particleís 4-momentum. If you read the paper youíll find what I consider to be a much better definition of proper mass, i.e. as the quantity m such that the quantity P = mU (where P = 4-momentum and U = 4-velocity) for a system of particles which interact only by contact forces, is conserved.


Note: What's with this stupid editor? Everytime I try editing in this window it keeps popping up to the top so I have to keep scrolling down to see what I'm editing!
« Last Edit: 02/02/2013 01:11:55 by Pmb »
 

Offline JP

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Re: How does mass increase at higher speeds?
« Reply #159 on: 02/02/2013 16:43:55 »
Ah true, I did misquote you.  Sorry for that.

My point still stands in roughly the same form.  If you list a bunch of defining characteristics of mass that preclude another definition of mass, then of course it has little or nothing to do with those characteristics.  Though I would argue that the use of invariant mass does meet the kinematical characteristics of mass, since classically, inertial mass in Newton's second law, F=ma, can be replaced in the four-vector version with invariant mass, and it's particularly elegant to view the transition to special relativity geometrically in terms of 4-vectors. 

The horse is still very dead, though.  We all agree (I hope!) on the physics involved, and that describing it requires 4-vectors and/or tensors.  In the end, we're arguing about a single scalar value pulled out of these equations, so of course there's multiple ways to do that!  Similar debates come up a lot in physics, where one has vectors/tensors and tries to use a single scalar to describe the physics.  It's always insufficient and very often just as contentious (look up degree of entanglement in quantum mechanics for a similar debate), and obscures the fact that everyone involved agrees on the physics.  I imagine this argument over mass will go on unless, some day, a unified theory comes along that does involve a single scalar value in the place of mass (for example, a coupling constant to some field describing inertial and gravitational masses) from which all other definitions follow.

I'll check out your paper when I have a chance.  I've got a backlog of reading to do at the moment.  :(
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #160 on: 02/02/2013 18:36:17 »
Quote from: JP
Ah true, I did misquote you.  Sorry for that.

My point still stands in roughly the same form.  If you list a bunch of defining characteristics of mass that preclude another definition of mass, then of course it has little or nothing to do with those characteristics.  Though I would argue that the use of invariant mass does meet the kinematical characteristics of mass, since classically, inertial mass in Newton's second law, F=ma, can be replaced in the four-vector version with invariant mass, and it's particularly elegant to view the transition to special relativity geometrically in terms of 4-vectors. 
Yup. And all of that is stated in my paper. :)

This is related to a new idea that I came up with. I call it the principle of controlled igorance. It states that physicists write with given assumptions that are agreed among their peers. E.g. what one person uses as the definition of the term momentum might be different that what someone else uses. Someone who works in classical mechanics will define momentum, when unqualified by anything, as p = mv. But another person working in quantum mechanics will define it as being identical to canonical momentum.

Quote from: JP
I'll check out your paper when I have a chance.  I've got a backlog of reading to do at the moment.  :(
Very cool. Thanks!
 

Offline Pmb

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Re: How does mass increase at higher speeds?
« Reply #161 on: 02/02/2013 18:49:56 »
Iíd like to add one thing. And thatís the importance of know what all these terms mean. If you donít know what it means then you certainly canít follow a discussion about how to measure these things. E.g. by hypothesis we assume that a bodies inertial mass is proportional to its passive gravitation mass. But we have to measure these things in order to verify the theory.

Clifford M. Will wrote a wonderful article called The Confrontation between General Relativity and Experiment
Itís online at http://arxiv.org/abs/gr-qc/0510072
 

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Re: How does mass increase at higher speeds?
« Reply #161 on: 02/02/2013 18:49:56 »

 

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