Place to discuss the Theory of Relativity

[Aer]

Don't your teachers deserve any credit for the fact that you can smart out almost anybody in this forum?

Being able to out smart anyone on these forums is quite a leap considering I've participated in only a handful of discussions.

As for physics in HS, I did have a very good teacher though I don't recall relativity being covered, perhaps it was briefly.

 

[EnumaElish]

And relativistic mass was never included in your curricula? Or was it?

 

[Aer]

And relativistic mass was never included in your curricula? Or was it?

Luckily I still have many of my physics notes. Most of my knowledge of special relativity is self learned though. I never took a class in college devoted solely to special relativity, but my physics classes at least covered the topic. (I have an engineering degree, not a physics degree). One of the best professors I had in college was one of my physics professors and here are his equations:

$$p = \gamma m v$$

$$E = m c^{2} + K = \gamma m c^{2}$$

$$E^{2} = (p c)^{2} + (m c^{2})^{2}$$

As you can see, there is no mention of "relativistic mass" as that equation would be:
$$E = m_r c^{2}$$
where m_r is relativistic mass. Also I checked the index of my physics book which contains no reference to relativistic mass.

Edit: Can someone (I am talking to you management, put a link to latex reference on the main page? OR if it is there, please make it more noticable)

 

[EnumaElish]

One of the best professors I had in college was one of my physics professors and here are his equations:

$$p = \gamma m v$$

$$E = m c^{2} + K = \gamma m c^{2}$$

$$E^{2} = (p c)^{2} + (m c^{2})^{2}$$

As you can see, there is no mention of "relativistic mass" as that equation would be:
$$E = m_r c^{2}$$
where m_r is relativistic mass.

What is K? And what is $\gamma$? What I am wondering is whether m_r is not part of these equations implicitly, or whether it can be derived from them, e.g. m_r = m/b, for a suitably defined b.

 

[Aer]

What is K? And what is $\gamma$? What I am wondering is whether m_r is not part of these equations implicitly, or whether it can be derived from them, e.g. m_r = m/b, for a suitably defined b.

K is kinetic energy and $\gamma$ is the relativity gamma factor (i.e. ${1}/{\sqrt{1-({v}/{c})^{2}}}$)

 

[EnumaElish]

If $m_r$ is defined as $= \gamma m$, then $E = \gamma m c^2= m_r c^2$, so relativistic mass is implicitly in your notes.

 

[Aer]

If $m_r$ is defined as $= \gamma m$, then $E = \gamma m c^2= m_r c^2$, so relativistic mass is implicitly in your notes.

I made $m_r$ up, it is not in my notes. As I said, that is just a definition and a meaningless definition at that. I could also define a "relativistic velocity" as $v_r = \gamma v$, does this velocity have any physical meaning? No it doesn't, athough the two terms $\gamma v$ come up in some equations, it doesn't make any sense to think of it as a "relativisitic velocity" to explain anything.

 

[EnumaElish]

From now on, whenever I use the expression "relativistic mass" (or the notation m_r) I will remember that it was not mentioned in your notes. Or that it is difficult to interpret as a physical entity (because it mixes the two frames, so to speak).

 

[Daminc]

Try the excellent General Relativity from A to B by Robert Geroch, which details different views spacetime from Aristotle to Galileo to Einstein.

Regards,
George

This book has finally arrived. Let's see how I get on