leejo

I believe a photon is a massless particle and everything I see when I do a search about it confirms that. I don't think that the Bose-Einstein condensate effect has anything to do with photons acquiring mass.

leejo

It has been a long time, but I majored in mathematics and minored in physics and philosophy, and basically studied quantum mechanics for 4 years. I know plenty about physics and I can play the philosophical mind games that physics presents just fine. I can't speak for anyone else, but if I don't throw terms around that 3 people here understand it's a sign of respect to the audience not a sign of ignorance.

Gambit7

Rest mass = mass measured at absolute zero?
Is not all measured mass inherently "relative" also? seeing as how it was measured.

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sordavie

Nope.

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ScratchMonkey

Are these different kinds of mass treated as unique symbols in equations? Or are they all "m"? I recall that it was surprising that inertial mass and gravitational mass were the same property, that the two went up and down together.

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Sig

sordavie

Since you are aware that General Relativity treats inertial and gravitational mass as strongly equivalent (that is fundamentally the same property), you probably recognize the weak equivalence principle:

a = g * (M / m).

The convention is that 'M' stands for gravitational mass and 'm' stands for inertial. In this case they have unique symbols.

An object's inertial mass can be calculated given its rest mass and its velocity by the following equation:

m = m0 / (sqrt (1 - (v^2 / c^2))).

Here, 'm' and 'm0' stand for inertial mass and rest mass respectively.

However, it's not like the conventions are set in stone and characters aren't necessarily reserved for a single unique concept.

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leejo

Nobody really talks about relativistic (inertial) mass any more. It's the same thing as energy. "Mass" is invariant mass. Other masses are mass * some vector if I remember correctly.

PanzerHans

This thread has turned into a gem. I have learned a lot more about mass than I would have expected from the thread title.

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sordavie

Who do you mean by "nobody?" A quick search of my school's physics journals database for the phrase "inertial mass" shows numerous 2007 articles (25+ I didn't bother to look at all the other hits) which contain the phrase. A search for the phrase "relativistic mass" also nets me numerous recent hits. Where are you remembering this from?

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Gambit7

Just because there are many papers on something doesnt mean it's a term widely embraced by Science. As physics gets more refined you'll see more and more of this. I caution anyone reading/writing threads like this to be aware that Science is an extremely volatile place right now. Terminoligies and theories are popping in and out of existence like vacuum fluctuations. This is why I tend not to bytch at more generalistic terms. It's almost a warm an fuzzy feeling being a bit ambiguous and open-minded.

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leejo

I didn't mean "nobody", I meant that in modern physics mass is generally understood to mean invariant mass. Any other form of mass is really invariant mass times some energy vector. If I'm trying to solve some problem and I know the relativistic mass but not the proper mass then yes I may have to clarify.

But that's not what happened. We were sitting here b.s.ing and you laughed at us because we weren't specifying which mass we were talking about. I'm telling you that when physicists sit around talking about mass, they're talking about invariant mass and they certainly don't snicker to themselves or leap to their feet and shout "j'accuse!" if one of them says "mass".

It doesn't surprise me that academic textbooks or some specialized papers occasionally discuss relativistic mass, but once the concept is learned, and unless there's a need, mass means mass.

sordavie

What I was laughing at was that some of you were having a debate over whether some particles have mass or not and whether they gain mass in certain circumstances. At the heart of this debate, it seemed to me, was that you guys were just using different concepts of mass--and thus talking past one another.

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INSUNABULA

Nice to see at least something is becoming less dense.

And speaking for the "more dense" portion of the audience who has no training or education in Physics or Mathematics but is interested none-the-less:

I thought all objects (particles, matter, etc...) had a "weight" bound to them otherwise how else to they interact and effect other particles/matter?

(please use small words in your explanation - I fully admit to not understanding all this)

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leejo

Force-carrying particles don't have any mass. The force-carrying particles are gluons, which carry the strong force, vector bosons, which carry the weak force, gravitons, which carry gravity, and photons, which carry the electromagnetic force. The strong and weak force acts over subatomic distances and so does not come up in conversation very often. The strong force holds nuclei together and the weak force induces a type of subatomic decay. Gravitons are predicted by theory but have not been observed.

These massless particles interact with other particles by delivering the force they carry.

Everything else has mass.

INSUNABULA

So where do the extra dimensions fit in? (and this is a serious question - as long as extra dimensions exist)

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