"A particle with rest mass..."
Does a photon have a rest mass?
"...as described by the unreduced form of Einstein's famous equation: E^2 = m^2c^4 + p^2c^2, where p is momentum"
Dimensional analysis shows that p in that equation will be mass x velocity. If you like p = mc.
"Inertia and momentum aren't the same thing". You are correct, they are not. Although I never said they were.
"An aside: why do FQXi members never step in to correct this nonsense? They're SUPPOSED to be the experts."
Nice idea. Perhaps for fear that standing in the dock and being cross-examined may reveal what is supposed to be hidden. I understand their reluctance. You don't want to stake your grants, etc because Tom said so.
"Maybe this non-mathematical explanation will help."
Very helpful indeed. In particular, momentum is a conserved quantity and this is predicated on mass also being a conserved quantity, hence the use of 'invariant' mass in relativity discussions.
I saw this and thought it useful and help you too. Let's help one another :). Although the paper is not free to read:
[link:scitation.aip.org/content/aapt/journal/ajp/77/9/10.1119/1.3160671]This paper explores the evolution of Einstein's understanding of mass and energy. Early on, Einstein embraced the idea of a speed-dependent mass but changed his mind in 1906 and thereafter carefully avoided that notion entirely. He shunned, and explicitly rejected, what later came to be known as "relativistic mass." Nonetheless many textbooks and articles credit him with the relation E=mc2, where E is the total energy,m is the relativistic mass, and c is the vacuum speed of light. Einstein never derived this relation, at least not with that understanding of the meaning of its terms. He consistently related the "rest energy" of a system to its invariant inertial mass.[/link]
Please digest and if you can afford the paper tell us what is inside. Is it true that Einstein changed his mind in 1906?
I also saw this on Wikipedia, although as you have mentioned elsewhere and I agree that source is not to be fully trusted but only for guidance and references contained (see under 'Relativistic mass':
[link:website address]This mass, i.e. relativistic mass is the ratio of momentum to velocity, and it is also the relativistic energy divided by c2 (it is not Lorentz-invariant, in contrast to mo).[/link]
This will disappoint those clinging tenaciously to Lorentz invariance principle.
relativistic mass, mrel is related to rest mass, mo by
mrel = mo{в€љ(1- v2/c2)-1}
It follows from mathematics that when mo = 0, mrel = 0
It also follows that if "The equation E = mrelc2 holds for moving objects", E = 0.
So Tom, if I have to beg of you to answer directly, does a photon have inertia?. Yes or No, will do before I ask a follow up question.
Regards,
Akinbo