Is Light Matter?

[ynot]

Tell him! I'm still waiting for my own, personal fatwa!

Good luck with that!

 

[Cuddles]

The only time you responded to me in this thread (other than above) was to misquote, and attempt to ridicule me.
“Atoms are indivisible? That will come as a bit of a surprise to, well, everybody.”

An atom is the smallest indivisible unit of matter.

Do you deny you said atoms are indivisible? Whether they are the smallest unit of matter is a different matter, although see below for how wrong that claim is. Whether smaller things are matter or not, atoms are divisible. Your claim was wrong.

In any case, even by your definition, this statement is completely wrong. You say you define matter as something that occupies space, by which I assume you mean it has finite size. Are nucleii not matter? Are protons and neutrons not matter? Are quarks not matter? They all have measureable size and follow all the other rules you have made up, yet you claim that they are not matter.

 

[Jimbo07]

Are nucleii not matter? Are protons and neutrons not matter?

Hah! My definition (matter is composed of elementary particles) still holds! Atoms, plasmas, nucleii... I rock!

Are quarks not matter? They all have measureable size and follow all the other rules you have made up, yet you claim that they are not matter.

hmmm...

 

[Cuddles]

Hah! My definition (matter is composed of elementary particles) still holds! Atoms, plasmas, nucleii... I rock!

Yeah, that one works, I just don't think it is particularly useful. I assumed that was what Ynot was going for as well, until he decided the discussion was getting too sensible and threw out some more nonsense about indivisible atoms and things like plasmas and nucleii not being matter.

hmmm...

To be fair, quarks are a debatable case. However, quarks are generally thought to have a finite size rather than being point-like particles. They are usually treated as points because it is much simpler and doesn't really affect anything we can do at them moment, rather like the way we use Newtonian mechanics to get to the Moon, even though relativity has replaced it. This paper, for example, estimates the radius of a quark. Very small, but not actually zero. A popular view is that quarks are actually not fundamental particles, they are made out of smaller ones in the same way protons are made out of quarks. There is some evidence for this, but it is far from conclusive because it is almost impossible to measure anything as small as a quark, let alone something even smaller.

 

[RecoveringYuppy]

Do you deny you said atoms are indivisible? Whether they are the smallest unit of matter is a different matter, although see below for how wrong that claim is. Whether smaller things are matter or not, atoms are divisible. Your claim was wrong.

He definitely did not claim that. It was post 63 that you misinterpreted. He even named some a sub components of an atom in that post. What he said was that atoms where the smallest unit of matter. It's simply a definition and it could even be a useful definition in many contexts.

Pointing out that there are inconistencies in the other parts of his definition is valid though. Nuclei certainly occupy space in the same way that an atom does.

 

[ben m]

To be fair, quarks are a debatable case. However, quarks are generally thought to have a finite size rather than being point-like particles. They are usually treated as points because it is much simpler and doesn't really affect anything we can do at them moment,

I think you're misinterpreting the paper; it's reporting the size of a "constituent quark", which is an effective size used in a popular approximation of hadron structure. The best analogy I can come up with is the following: Event planners often use the quantity "area per person" to solve crowd control problems; I think that close-packed, stationary crowds are expected to fit one person per 2 square feet, crowded walkways can fit one person per ten square feet, etc. This paper is saying the equivalent of "We find that measurements of actual crowds are best fit by a 1.95-square-feet-per-person model"---that's very different than saying "persons are 1.95-square-foot objects"

The underlying quarks of the Standard Model are indeed pointlike, just like electrons; any "size" associated with them is actually the size of their attached cloud of photons, gluons, q-q pairs, etc.

The "quarks are made of yet smaller, tightly bound things" model is called the preon model; there is no evidence for it so far, and I don't think it is a very popular model any more.

 

[Jimbo07]

Yeah, that one works, I just don't think it is particularly useful.

Oh, I wasn't aware that we were also being forced to comment on its applicability!

The word "matter," sounds like something you'd hear at the beginning of a junior chemistry class, as in, "All matter is made up of elementary particles, and in chemistry our concern is with the electron... etc."

 

[Cuddles]

He definitely did not claim that. It was post 63 that you misinterpreted. He even named some a sub components of an atom in that post. What he said was that atoms where the smallest unit of matter. It's simply a definition and it could even be a useful definition in many contexts.

No. He said atoms were indivisible. I quoted his exact words. "The smallest indivisible unit of matter". As I said, whether you claim atoms are the smallest unit of matter or not is irrelevant, atoms are not indivisble, end of story. Using the word "indivisible" in the same sentence as the word "atom" without also including the words "are not" is simply wrong. The fact that this is also inconsistent with his claim of what matter actually is just adds to the wrongness.

The underlying quarks of the Standard Model are indeed pointlike, just like electrons; any "size" associated with them is actually the size of their attached cloud of photons, gluons, q-q pairs, etc.

The "quarks are made of yet smaller, tightly bound things" model is called the preon model; there is no evidence for it so far, and I don't think it is a very popular model any more.

Fair enough, I didn't really read the abstract properly so I got the wrong idea. As I said, the question of quark size is a matter for debate. It was certainly quite popular a couple of years ago, but I don't have much contact with the high energy physics field any more so it could have gone out of favour. I'm fairly sure there was some evidence, but it was more suggestive that further research might show something rather than anything really solid.

 

[ponderingturtle]

No. He said atoms were indivisible. I quoted his exact words. "The smallest indivisible unit of matter". As I said, whether you claim atoms are the smallest unit of matter or not is irrelevant, atoms are not indivisble, end of story. Using the word "indivisible" in the same sentence as the word "atom" without also including the words "are not" is simply wrong. The fact that this is also inconsistent with his claim of what matter actually is just adds to the wrongness.

But is it right to think of protons as divisible? Sure they are made up of quarks but quarks can never exist on their own in an unbound fashion. The strong force is too strong for that.

So can something be thought of as indivisible if its constituents can not exist by them selves?

The one thing everyone seems to agree on is that matter is not a very useful term in particle physics as the individual type of particle is more useful.

 

[Cuddles]

But is it right to think of protons as divisible? Sure they are made up of quarks but quarks can never exist on their own in an unbound fashion. The strong force is too strong for that.

So can something be thought of as indivisible if its constituents can not exist by them selves?

Well firstly he was talking about atoms, not protons. Since the constituents of atoms can exist by themselves this doesn't really matter. As for quarks, they can't exist on their own at normal temperatures and pressures, but they can do so under more extreme conditions. At least, they way not exist strictly on their own, but they can certainly exist outside of protons and neutrons. I would certainly say that something that can be smashed apart is not indivisible, even if the parts rapidly combine into something else.

The one thing everyone seems to agree on is that matter is not a very useful term in particle physics as the individual type of particle is more useful.

Pretty much. To go back to the life analogy, discussing life in general is fine philosophically, but from a scientific point of view you will never talk about life in general, only about specific types of life. If you're working with viruses, it really doesn't matter if you call them life or not, all that matters are the actual properties of the things you're working with. Same with physics. Electrons behave like electrons whether you call them matter or not.

 

[RecoveringYuppy]

No. He said atoms were indivisible. I quoted his exact words. "The smallest indivisible unit of matter".

But those exact words don't say that atoms are indivisible. Those words leave open the possibility that atoms can be divided but that the resulting parts are no longer matter. And it's clear from the rest of his post and subsequents posts that this is exactly what he meant.

 

[ponderingturtle]

Well firstly he was talking about atoms, not protons. Since the constituents of atoms can exist by themselves this doesn't really matter. As for quarks, they can't exist on their own at normal temperatures and pressures, but they can do so under more extreme conditions. At least, they way not exist strictly on their own, but they can certainly exist outside of protons and neutrons. I would certainly say that something that can be smashed apart is not indivisible, even if the parts rapidly combine into something else.

I don't believe I claimed that they couldn't form other things, just that they can not exist on their own. I have not heard of any suggestions(but then I admit a weak formal background in particle physics) that they could. My understanding was that when they get sufficiently far from the other quarks that they are bonded to, the strong force breaks and forms new particles at the ends of both.

 

[ynot]

But those exact words don't say that atoms are indivisible. Those words leave open the possibility that atoms can be divided but that the resulting parts are no longer matter. And it's clear from the rest of his post and subsequents posts that this is exactly what he meant.

Thanks - Glad someone can read in context. I think Cuddles can, but for some reason, doesn't want to. I'm travelling at present so don't have time to reply further. Will do so in a few days.

 

[Cuddles]

But those exact words don't say that atoms are indivisible. Those words leave open the possibility that atoms can be divided but that the resulting parts are no longer matter. And it's clear from the rest of his post and subsequents posts that this is exactly what he meant.

Which is why I also pointed out that this is completely inconsistent with his claimed definition of matter. Protons, neutrons, plasmas and so on have size, mass, obey Pauli and all the rest. A reasonable argument could be made for defining matter as things made out of pointlike particles, but not the pointliks particles itself. There is no possible way to defend the view that only atoms are matter. It's not at all clear what he meant, because the meaning keeps changing every time someone points out the nonsense.

I don't believe I claimed that they couldn't form other things, just that they can not exist on their own. I have not heard of any suggestions(but then I admit a weak formal background in particle physics) that they could. My understanding was that when they get sufficiently far from the other quarks that they are bonded to, the strong force breaks and forms new particles at the ends of both.

I know you didn't claim that, I never said you did. However, you did suggest that protons could be considered indivisible because their components can't exist independently. I simply countered this by pointing out that they can be broken apart and form other things, therefore they are not indivisible.

 

[ponderingturtle]

I know you didn't claim that, I never said you did. However, you did suggest that protons could be considered indivisible because their components can't exist independently. I simply countered this by pointing out that they can be broken apart and form other things, therefore they are not indivisible.

But because you can destroy them and result in other short lived things in the aftermath, I am not sure that counts as indivisible.

Indivisible might also not be very well defined in this sort of discussion.

Is a photon indivisible? You can get one to produce other particles in pair production, so photons are also not indivisible.

Sure they are not made up of these particles but neither are the protons made of the particles you are talking about.

 

[This is The End]

Surely this topic isn't on page three and no one has mentioned the famous double slit experiment. It probably was as I tend to miss things. Or perhaps we're ignoring it as obvious for being first year physics.

From fear of being tasered for posting a link while having so few posts let me just say wiki/Double-slit_experiment

 

[Cuddles]

But because you can destroy them and result in other short lived things in the aftermath, I am not sure that counts as indivisible.

Indivisible might also not be very well defined in this sort of discussion.

Is a photon indivisible? You can get one to produce other particles in pair production, so photons are also not indivisible.

Sure they are not made up of these particles but neither are the protons made of the particles you are talking about.

Yes they are. I'm not talking about particles decaying. Protons are made of quarks. You can break up the proton and form the quarks into a different particle. This probably can't be done for a single proton, but if you take a quark-gluon plasma you can make all sorts of particles out of the quarks as it cools down and condenses. This is probably exactly what happened in the early universe. Also, if being able to break something into smaller pieces doesn't mean it's certainly not indivisible then you must be using a very different definition from the one I am.

Break a human up and you get cells, not lots of little humans. Break a cell up and you get weird, complex molecules, not lots of little cells. Break a complex molecule up and you get atoms, not little complex molecules. Break an atom up and you get protons and neutrons, not lots of little atoms. Break a proton up and you get quarks, not lots of little protons. Break a quark up and you might get lots of little thingies, depending on which theory you look at. Why decide to call atoms or protons indivisible when they can be divided into smaller things?

In any case, once again, Ynot was not talking about protons, he was talking about atoms.

Surely this topic isn't on page three and no one has mentioned the famous double slit experiment. It probably was as I tend to miss things. Or perhaps we're ignoring it as obvious for being first year physics.

From fear of being tasered for posting a link while having so few posts let me just say wiki/Double-slit_experiment

The double slit applies to all particles, so it doesn't really help to find a definition of matter. OK people, break out the tazers.

Edit: And welcome by the way.

 

[ponderingturtle]

Yes they are. I'm not talking about particles decaying. Protons are made of quarks. You can break up the proton and form the quarks into a different particle. This probably can't be done for a single proton, but if you take a quark-gluon plasma you can make all sorts of particles out of the quarks as it cools down and condenses. This is probably exactly what happened in the early universe. Also, if being able to break something into smaller pieces doesn't mean it's certainly not indivisible then you must be using a very different definition from the one I am.

I am questioning what indivisible means in context. You did not say if you consider a photon indivisible or not, and how that related to pair production.

Break a human up and you get cells, not lots of little humans. Break a cell up and you get weird, complex molecules, not lots of little cells. Break a complex molecule up and you get atoms, not little complex molecules. Break an atom up and you get protons and neutrons, not lots of little atoms. Break a proton up and you get quarks, not lots of little protons. Break a quark up and you might get lots of little thingies, depending on which theory you look at. Why decide to call atoms or protons indivisible when they can be divided into smaller things?

The thing is that you can't ever break up something and get quarks. You get other things made of quarks. You can isolate the smaller things in all of those other stages. So it would be like breaking up a bunch of humans and getting a rat, a tree and a dog. They are made up of cells as well, but not being able to get the cells themselves.

I am not saying quarks don't exist, it is just that they can never exist by themselves and not as a part of some larger particle.

In any case, once again, Ynot was not talking about protons, he was talking about atoms.

And I really don't care about Ynot. I was just wondering what you can consider a indivisible particle, and what traits it can or can not have.

 

[ponderingturtle]

Surely this topic isn't on page three and no one has mentioned the famous double slit experiment. It probably was as I tend to miss things. Or perhaps we're ignoring it as obvious for being first year physics.

From fear of being tasered for posting a link while having so few posts let me just say wiki/Double-slit_experiment

Welcome, but as most people in the thread accept particle wave duality, I am not at all sure what a demonstration of diffraction interference is supposed to show.

And everyone knows all the cool physicists use crystals for their diffraction grating anyway.

 

[This is The End]

Resisting posting the wiki link in full:

When the double-slit experiment is performed one photon* at a time with sensitive apparatus the same interference pattern emerges that would be seen if multiple electrons were fired simultaneously.....

(or electron, proton, or something else existing on what is considered a "quantum" scale)



This threads' particle wave duality 'consensus' aside, I tend to lean towards this being evidence that these types of particles are energy and not matter; waves can easily be in two places at once, matter cannot. I'm also leaning towards - matter takes up space; energy travels through space in waves. I think that just because energy can compose matter, doesn't mean matter can compose energy (compose implying assembly not conversion). I also don't see why being able to fire one unit of energy at a time implies in any way that it is matter.

To me it is unfortunate but quite telling that quantum physics doesn't allow us to see the position of these waves over time, nothing magical about it. Something along the lines of since we use 'energy' to precisely detect 'matter', we can't use 'energy' to precisely detect 'energy'. If blindfolded in a dark room it would be easy to detect the walls but nearly impossible to detect a young gnat or fruit fly in the air. Likewise if instead of using your arms/hands you tried to detect holding a gnat sized grain of sand between your fingers, you wouldn't have any more or less luck finding the gnat or not finding the wall. One shouldn't expect to be able to precisely detect that which is the method used in the detecting.