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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leejo

Well, remember that mathematics is the language of science. Often in physics we're talking about a vector - energy and a direction. You express a vector with a coordinate for each dimension. A vector with size 3 heading directly to the right and not moving up or down at all on a 2-dimensional Cartesian chart would be expressed (3,0). You can perform mathematical functions on vectors to add them together, move them around, change the angle, etc. You can solve for a vector. You can build matrices of vectors that become arrays and perform functions on them, and you can solve for an array.

In pure mathematics, I can have as many dimensions in a vector or an array as I please. Each column is a dimension.

When a serious physicist talks about other dimensions, he or she is really talking about how some of the rabbit holes that the mathematics that describe the theory lead one down can be more easily solved if one adds some number of columns to a vector or an array. Instead of a vector with three dimensions like this (1,2,3) it may appear that a 7 dimension vector would work better (1,2,3,4,5,6,7), for example. From this many conclude that sometimes energy is acting in "other" directions.

We know nothing about the properties of such dimensions, we just know that equations seem to suggest they may exist.

IMO since these dimensions are generated because of a problem with the mathematics and not some experimental discovery, extra dimensions are a sign that there's a problem with the theory or the math (not the math's execution but the underlying theories being used).

This is all probably clear as mud. Sorry.

Tarenth

In a practical sense then you could explain dimensions as the process which we precieve something. Without delving into pure physical and pure mathematical models it is easy to understand 4 dimensions.

1 - Exsistance. It is because it is there (X)
2 - Linear movement. (X,Y)
3 - Spatial movement. (X,Y,Z)
4 - Temporal movement. (X,Y,Z,?)

However broken down to the basic meaning you can see that all 4 are once more the subject of pure math and physics because they are constructs that help us understand our environment. To be more precise, they are labels for constructs that we create. We precieve something to be there because we believe it is there. We precieve it to move because we believe it to move. We precieve time to change because we believe it to change. We see so we believe and we believe because we see.

As science and our understanding evolve we'll probably add more to what we know and rewrite the theories of the past to incorporate the new (its why we have very few 'laws'). Perhaps one day we will find out that reality as we know is planar and that what we precieve as spatial (X,Y,Z) is just movement along a relatively linear (X,Y) plane and we can then pass upwards or dowards through it in order to by pass spatial distances with an extra dimensional movement beyond planes. Afterall, that's the basis of a lot of sci-fi right there.

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My sanity is not in question...
It was a confirmed casualty some time ago.

sordavie

???

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mentholated

Yeah when I said dimensions, I literally meant a distinct plane of existence with physical laws which are not properties of the one in which we currently reside. Not mathematical dimensions (although the mathematical calculations originally let us know that these extra dimensions actually exist, we can't really interact with them other than on extremely small scales (see particle generators/colliders).

..Well, that is, unless you work for an aerospace manufacturer like boeing, lockheed, northrop, etc. etc.

..On projects that do not exist.

Gambit7

Let's not get into defining what the term "dimension" means now.. hehe

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ScratchMonkey

In one of Heinlein's short stories he explained the temporal dimension in a graphic way: Imagine that you rotate the 4-D universe (X/Y/Z/T) so that you swap one of the space dimensions for the time dimension. A man appears to be a long, pink snake. At the tail is a fetus in the womb. At the head is the man being lowered into his grave. Slices of the snake would be photographs of the man at some point in his life.

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Sig