I've come to learn that there's a great deal of misinformation floating around the Internet regarding what some people call

**relativistic mass** in modern relativity and relativistic cosmology. The misinformation is that it's an outdated concept that

*nobody* uses anymore. This thread gives solid proof that this claim is invlaid and that relativistic mass is alive and well in the wonderful world of Einstein's world of relativity.

If anyone wants to verify what I said as being true the all you need to do is follow the URLs given below so that they can see it for themselves. I have many recently published SR and GR texts on my book shelf which use the concept and so their claim is just plain wrong.

Let's start off with a perfect example.

**Alan Guth**, a particle physicist/cosmologist at MIT. He's a perfect example of somone who uses relativistic mass (which he simply refers to as "mass"). He uses it in his lecture notes for his

**Early Universe** course that he teaches at MIT. I placed a sample page online so that you can see it for yourself. It's at

http://home.comcast.net/~peter.m.brown/guth.jpg There is a large percentage of modern relativity and relativistic cosmology textbooks out there right now which proves such a claim is bogus. There are simply no facts out in the physics world that is consistent with the claim that its outdated other than the mere claim that it's outdated. Particle physicist often make this mistake so if one tells you that the only mass that's used in relativity is rest mass, don't believe them because it's a false statement. Particle physicists simply aren't relativists. They're merely people who use relativity as a tool in their work. They don't study relativity as a field in itself. Such physicists rarely, if ever, use the concept of mass outside the area of application of particle physics. They simply don't know the limitations of the way they chose to define "mass." And the fact that those limits don’t occur in their work makes it irrelevant for them.

Counter examples are given in my article on the subject. I wrote an entire paper giving all the reasons why what I'm stating is true. There's just far too much to place in as single thread or post. The paper is called

**On the concept of relativistic mass** and is located at

http://arxiv.org/abs/0709.0687 for those with the skill set to understand it. For those who don't please just ask. A perfect counter example to the claim that nobody uses relativistic mass in "particle physics/accelerator physics" is given in a web page under CERN's website at

http://teachers.web.cern.ch/teachers/archiv/HST2002/Bubblech/mbitu/energymomentum_4vector.htm Notice that this page is to

**teach** so please read what CERN wants you to learn.

The claim that it hasn't been used for over 20 years is demonstratably false as anybody who wants to look in a book can learn for themselves. I've provided a list to such textbooks and a link to where you can read it online if it's available. Here's how this problem got

*re*-started back in the late 80's with an article by Lev Okun. And yes. I did say

*re*-started because contrary to popular belief Lev Okun didn't originate this spiel about mass. Lev Okun made an attempt to ban the concept from all of physics but failed miserably. A lot of amateurs and non-relativists claim that its not used tool. Relativistic mass

**widely** used in relativity and cosmology textbooks

There were two notable articles to counter Okun's tirade. They are

**In defense of relativistic mass** by T.R. Sandin,

*Am. J. Phys.*, 59(11), Nov. (1991)

b]Putting to Rest Mass Misconceptions[/b] by Wolfgang Rindler,

*Physics Today*, May (1990)

The USENET Physics FAQ had it wrong for a while until I explained these facts to Don Koks, the physicist who maintains those FAQs.

See

http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html The following are books that use relativistic mass

**Concepts of Mass in Contemporary Physics and Philosophy** by Max Jammer,

*Princeton University Press*, (1999).

Download Available:

http://bookos-z1.org/book/872005/406a03 **A first course in general relativity** by Bernard F. Schutz,

*Cambridge University Press*, (2009), from page 88

Download Available:

http://bookos-z1.org/book/573635/b31618

Thus, *n* is a scalar. In the same way that 'rest mass' is a scalar, even though energy and 'inertial mass' are frame dependant …

This demonstrates a clear example of the use of relativistic mass as another term for inertial mass. It also shows an example of the fact that some people mean

*relativistic mass*when they use the term

*mass* unqualified.

**Gravity from the ground up** by Bernard F. Schutz,

*Cambridge University *

Press, (2003). See page 241

Download Available:

http://bookos-z1.org/book/507531/96158f

Immediately we see a problem: "mass" has no unique meaning in relativity.

**Relativity: Special, General and Cosmological**, Rindler,

*Oxford Univ., Press*,

(2006).

Download Available at:

http://bookos-z1.org/book/931043/b4e4bd **Introducing Einstein's Relativity**, Ray D'Inverno,

*Oxford Univ. Press, * (1992).

Download Available:

http://bookos-z1.org/book/1024503/b16828 **General Relativity: An Introduction for Physicists** by M.P. Hobson, G. Efstathiou and A.N. Lasenby,

*Cambridge University Press*, (2006)

Download Available:

http://bookos-z1.org/book/929425/315169 **Relativity; An Introduction to Special and General Relativity** by Hans Stephani,

*Cambridge University Press*, (2004).

Download Available:

http://bookos-z1.org/book/1249890/ad351e **Cosmological Physics** by John A. Peacock,

*Cambridge University Press*, (1999).

Download Available:

http://bookos-z1.org/book/451793/b5bb91 **Basic Relativity** by Richard A. Mould,

*Springer*, (1994).

**Einstein's General Theory of Relativity: With Modern Applications in Cosmology** by Grøn, Øyvind (2013)

Download Available:

http://bookos-z1.org/book/884554/09b625