Relativistic Momentum: Mass, Time & Distance

[bernhard.rothenstein]

a relativity story. What is its moral?

1. Why do we have to assume mass doesn't change? And always use m_0?
2. OK, let's assume we always use m_0. Then why is momentum is defined as \frac{mv}{\sqrt{1-\frac{v^2}{c^2}}}. If measuring in object's frame of reference, shouldn't we use his distance and time, where they are \frac{x_0}{\gamma(v)} and t_0 \gamma(v), and v would be \frac{x_0}{t_0 \gamma(v)^2}. It seems that we're using x_0 either t_0 and not both, nor none. Isn't this inconsistent?

Your thread gave me the ideea of the following possible scenario. A teacher of physics did avoid in his lectures the concept of relativistic mass. One day one of his students, tought that way, comes to him with a paper by Bucherer or by Kaufman (190?) showing the formula
m=m(N)g(V) (m(N) Newton mass) and asking for what stands m for.
Would you start by explaining the concept of relativistic mass? Should we blame the two brave physicits for the fact that they did not guess what long and fierce debates did they start.
My question is: What is the moral of that possible happening?

 

[pmb_phy]

And if we want to be consistent it seems to me that for instance frame fields are not mainstream either. But that does not mean that they are not useful. Would you argue to treat those the same way?

I would hazzard to guess that they would. Another example is Brehme diagrams. They are another kind of spacetime diagrams as is the Minkowski and the Loedel spacetime diagrams. The overwhelming majority of people use Minkowski diagrams. Should we ban any discussion of Brehme diagrams?

Pete

 

[Gokul43201]

I think that is a rather restricted and dogmatic approach to teaching.
As long as what is shown is not wrong and instead is just another perspective on the theory of relativity it would be in the interest of pedagogy IMHO rather than counter to it.

It would be in the interest of pedagogy to discuss such treatment among sufficiently well-versed peers not with any and every student of the subject; and it would only be harmful to the students learning the subject for the first time.

What I posted came from "Gravitation," by Misner, Thorne and Wheeler as well as "A first course in general relativity," by Bernard F. Schutz.

In that case, you could have pointed the OP to the relevant parts of MTW or Schutz.

Your article disagrees with the majority position that a particular definition is, in general, the more useful one of the two possibilities. That makes it unsuitable to a Forum that aims to help students learn mainstream concepts, particularly when used in the form of a citation.

If you make your point directly in the thread (as you did in post#5), it becomes possible for others to refute a particular argument that they might find faulty. But if you use a citation (to an unrefereed article) in support of an argument you or someone else makes on a thread (as in bernhard's post #3 and your post #13), then it becomes impossible to make specific refutations without turning the thread into a discussion of that article. That is not allowed in this subforum - articles not published in peer reviewed journals or taken from standard texts are not up for discussion.

For instance, there's the possibility that this thread might have gotten diverted from helping gulsen to discussing various articles written by participating members.

You wouldn't want that to happen, would you?

PS: Let's be clear about one thing: we're not talking about forbidding discussion of the usefulness of alternative pedagogical approaches, only the citation of unrefereed articles that utilize them.

 

[pmb_phy]

In that case, you could have pointed the OP to the relevant parts of MTW or Schutcrz.

This coming after a year of me posting that comment? Why so late? In any case "mainstream" is being used in an incorrect manner by yourself and others. The true definition of the term "mainstream" means

mainstream; a prevailing current or direction of activity or influence

It doesn't mean "That which every participant of a particular group means by a term." To that end there is nothing to speak of regarding your speculations on what is and isn't "mainstream." The term as I use it and which it should be taken to mean is that as used in the relativity literature which includes modern textbooks on the subject.

Your article disagrees with the majority position that a particular definition is, in general, the more useful one of the two possibilities.

So what? It doesn't matter what the crowd things. In physics one does not vote on the validity of a concept and in each place I read something against the concept of inertial mass was written by a person which only a basic understanding of the term. [nonsense snipped]

If you make your point directly in the thread (as you did in post#5), it becomes possible for others to refute a particular argument that they might find faulty.

I was responding this year, the year in which the person addressed my paper and as such it was my paper which became the subject matter.

Would you like to know why I post here? To helo people who don't understand relativity and physics. I'm not here to listen to people who wish to engage in unplesant conversation. The rest of your post is justr of that nature. You are neglecting what I'm saying and whining about where I said it.

Sorry but I don't think we could ever carry on a peaceful conversation again. If you believe that yoour attitude has changed then please feel to e-mail me about it and I might unblock you. You can also e-mail me about other things so long as you are not being unpleasant.

Best wishes

Pete

 

[pmb_phy]

One personal note though, I could live without endless identical arguments in each topic that contains the word mass, that certainly does not serve any good.

I could learn to live without all of them. I've grown sick and tired of the subject. That's the reason I picked up a new text and am refreshing a subject which I haven't picked up for years.

Best wishes

Pete

 

[Gokul43201]

This coming after a year of me posting that comment?

What comment? I'm talking about posts in this thread, all of which have happened over this past week.

The true definition of the term "mainstream" means:

mainstream; a prevailing current or direction of activity or influence

Yes, that's a reasonable definition.

So what? It doesn't matter what the crowd things.

By your definition above, it is the "crowd" (or the prevailing current) that determines what is mainstream. If you disagree with the crowd, you are disagreeing with a mainstream idea.

I was responding this year, the year in which the person addressed my paper and as such it was my paper which became the subject matter.

Again, I have no idea what you mean by all this. In this thread, it was you that brought up your article, not someone else.