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Deep_Eye
2003-Sep-19, 01:28 AM
Ok, atomic structure is something that I find very interesting. I did an internet search to learn more about quarks, but I ended up with more questions than answers! I learned that a quark is a small unit of matter that makes up electrons, neutrons, and protons. In the material it named some others. I'll just list my questions to make it easier to read.
1) What are mesons?
2) What are photons?
3) What are neutrinos?
4) What is the smallest particle yet observed?

Tinaa
2003-Sep-20, 06:02 PM
I have read several books about subatomic particles. So much is conjecture because we cannot see these particles. I cannot really explain much because this is pretty heady stuff. I have found a web site that may help. I found this one in my own quest to understand these tiny bits of matter. I think the site is set up for students, but even at forty, I find there is oh so much to learn and so little time!

http://particleadventure.org/particleadven...rtstandard.html (http://particleadventure.org/particleadventure/frameless/startstandard.html)

imported_buckminster
2003-Sep-20, 10:18 PM
Tinaa spoketh thus:


So much is conjecture because we cannot see these particles.

People doing science must often make educated guesses about things we can't see or measure directly. Scientist are pretty good at figuring the properties of these invisible objects by looking at the "tracks" that they leave , just like a hunter reads the tracks of the animals. The standard model has been fleshed out pretty well over the last three decades.



I cannot really explain much because this is pretty heady stuff.

You are not alone. Some of the smartest folks that ever walked on this planet feel the same way about this subject. Like most things that are valuable to know, you just gotta keep trying to figure this stuff out. Keep at it!!




"The universe is not only queerer than we suppose,
it is queerer than we CAN suppose." - J.B.S. Haldane



best regards,

buck

Deep_Eye
2003-Sep-21, 05:33 PM
OK, thanks both, I'll check out the web page.

SOMSOC
2003-Oct-14, 09:27 PM
A quark I believe

kashi
2003-Oct-14, 09:49 PM
I'm pretty sure current theorists believe there are particles smaller than quarks. It's been a while since I've read that stuff so I should brush up on the details. There's a chapter in A Brief History of Time called "elementary particles and the forces of nature" which gives a good explanation of all this. Hawking's latest book "The Universe in a Nutshell" is very good for this too, and it's more up to date.

zephyr46
2003-Oct-15, 01:41 AM
I find it strange how staring out out cosmic distances draws us back to the smallest unveiwable ideas, U o York (http://www.hep.yorku.ca/yhep/main.html), this is a rough website (http://perso.club-internet.fr/molaire1/e_plan.html) that I found most easily introduced this heady subject.

You might like this site too (http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html)

Matthew
2003-Oct-15, 09:55 AM
I think the smallest fundamental partical is a quark. But if superstrings exist then they would be the smallest. If you draw a superstring (representation) about 3-6 cm then an elementary particles would be bigger than the solar system.

zephyr46
2003-Oct-23, 05:26 AM
Grava site links to String theory (http://www.grava-space.net/links_references.htm) :)

alexmann
2009-Nov-08, 05:26 PM
the smallest is a glueon:lol::lol::surprised:surprised:shifty::whist le::hand::doh:

Strange
2009-Nov-08, 06:39 PM
1) What are mesons?

There are lots of ways that particles can be categorized which can make it quite confusing. Mesons are a largish group of particles. They are made up of a pair of quarks (a quark and an antiquark).

Particles made up of quarks are called hadrons.

Apart from mesons, the other group of hardrons are the baryons, which are made up of three quarks. The most important baryons are the protons and neutrons that make up the nucleus of atoms.



2) What are photons?

Photons are the particles which "carry" elecotromognetism. They are fundamental particles (not made up of anything smaller).



3) What are neutrinos?

Neutrinos are very light particles. There are three types of neutrino. They are fundamental particles in the lepton family which also includes electrons (as well as muons and taouns).



4) What is the smallest particle yet observed?

Not sure that size is very meaningful for all of these. I think, if "smallest" refers to mass, then the answer would be one of the neutrinos.

This page has a reasonably simple overview:
http://en.wikipedia.org/wiki/List_of_particles
http://en.wikipedia.org/wiki/File:Particle_overview.svg

hhEb09'1
2009-Nov-08, 06:49 PM
Welcome to BAUT, alexmann. This is a very old thread, so don't expect the original participants to respond much.
I learned that a quark is a small unit of matter that makes up electrons, neutrons, and protons. I don't think electrons are made of quarks, in the standard model, are they?

WayneFrancis
2009-Nov-09, 12:54 AM
Ah drive by necromancy. Could there be some filter that holds a newbie's revival of a very old post to be held for moderator approval?

Electrons are fundamental particles themselves, so no...no quarks in an electron.

Jens
2009-Nov-09, 02:54 AM
Sorry if I'm contributing to a drive-by necromancy, but I have a kind of simple question that might not be that simple. Is there a reason that we can assume that quarks themselves are not made up of something even more fundamental?

Jeff Root
2009-Nov-09, 03:32 AM
Jens,

I read a rather attractive article many years ago in Scientific American
outlining how quarks might be composed of other particles which the authors
called preons. I haven't heard anything of it since then, though, so it seems
not to have gained any significant support.

Degraded Red Spot,

Another Scientific American Article ('A Unified Theory of Elementary Particles
and Forces' by Howard Georgi, April 1981) tells how electrons may be related
to quarks.

-- Jeff, in Minneapolis

trinitree88
2009-Nov-09, 04:39 PM
Sorry if I'm contributing to a drive-by necromancy, but I have a kind of simple question that might not be that simple. Is there a reason that we can assume that quarks themselves are not made up of something even more fundamental?

Jens. The first attempt to probe matter, at the atomic level led Rutherford to conclude that atoms had a hard spot....a nucleus that was massive but tiny. Scattering experiments can infer tiny structures. SEE:http://commons.wikimedia.org/wiki/File:Rutherford_gold_foil_experiment_results.svg
To study quarks you would need to isolate them, which has proven impossible to do. The energy they used to try to separate out the quarks from a nucleon created more of them instead....as mesons.
As near as physics can tell, quarks, electrons are pointlike with no size or substructure as of this week. We'll see if the LHC modifies this. pete.

SEE also:http://en.wikipedia.org/wiki/Point_particle

bebe7
2009-Nov-11, 04:03 PM
Whats that other name for the Higgs Boson....?

Grey
2009-Nov-11, 05:54 PM
Sorry if I'm contributing to a drive-by necromancy, but I have a kind of simple question that might not be that simple. Is there a reason that we can assume that quarks themselves are not made up of something even more fundamental?There is no particular reason to assume that they are, but there is equally no reason to assume that they could not be. Same with the leptons and all the other "fundamental" particles. At the moment, as far as we can tell they have no internal structure, but if we step up to a higher energy scale we might discover that they do.

Jens
2009-Nov-12, 05:46 AM
There is no particular reason to assume that they are, but there is equally no reason to assume that they could not be. Same with the leptons and all the other "fundamental" particles. At the moment, as far as we can tell they have no internal structure, but if we step up to a higher energy scale we might discover that they do.

I think, but I'm not sure, that it would be nice if they were not, because then you can avoid the problem of having infinities in the calculations. My very basic understanding is that point particles present a problem because gravity rises to infinity at the point. But if there are no fundamental particles, i.e. if it's just more turtles all the way down, then the problem gets resolved.

Grey
2009-Nov-12, 06:03 AM
I think, but I'm not sure, that it would be nice if they were not, because then you can avoid the problem of having infinities in the calculations. My very basic understanding is that point particles present a problem because gravity rises to infinity at the point. But if there are no fundamental particles, i.e. if it's just more turtles all the way down, then the problem gets resolved.Sure, but there are other ways of resolving that. String theory is just such a option (we've yet to see if it will really work, of course), and there may be other ways to resolve that issue. Maybe the way gravity is modeled would need to be changed. But it's certainly possible that we never find a bottom layer of truly fundamental particles, and that would indeed solve that particular problem. It would also make sure that physicists always have a job. ;)

Jeff Root
2009-Nov-12, 09:15 AM
Maybe the way gravity is modeled would need to be changed.
This question is off-topic for the thread, but the thread is on a
heart/lung machine anyway...

What do you mean by a gravity model? I'm asking a fairly general
question, not specific to the situation you were commenting on.
Actually a sufficient answer might be as little as a sentence, but I
don't know how to express the question in a way that will definitely
make it that easy for you.

I guess I'll explain why I ask. I'm one of those who has a little
knowledge... about gravity. So naturally I have an ATM speculation
about it. My speculation suggests that general relativity is fine, but
the model of gravity that ... um ... accompanies GR would need to
change in a way that might seem rather radical to some people.
You've read my posts about it. My question is as much about the
terminology as it is about the physics and derivation of models.

-- Jeff, in Minneapolis

Grey
2009-Nov-12, 03:39 PM
What do you mean by a gravity model? I'm asking a fairly general
question, not specific to the situation you were commenting on.
Actually a sufficient answer might be as little as a sentence, but I
don't know how to express the question in a way that will definitely
make it that easy for you.I just meant that the reason gravity blows up for a point particle is that distance shows up in the denominator, so a whole bunch of values blow up as you get infinitely close. But (to suggest a silly change) what if you replaced every appearance of r in the equations with r + 0.0000000001? Now you never get that zero value, and your results will be big but finite. Now, that particular substitution probably won't work. But maybe there's some other tweak to the equations that we use to describe gravity that still looks just like general relativity for any reasonable distances (it has to, because we know that general relativity works really well for those distances), but is a little bit different when you get down to quantum level distances. Well, maybe then you'd have a quantum theory of gravity that doesn't blow up with point particles. Nobody has such a theory, or even knows if it's possible, but it would be one solution to the problem.

Other potential solutions include Jens' suggestion (no matter how small a scale we look at, we'll never find point particles because they all have some internal structure), string theory (the fundamental particles are not points after all, but have some spatial extent, perhaps in multiple dimensions), maybe some kind of quantization of space (there's no such thing as a meaningful distance smaller than, say, the Planck length, so any place where you're thinking you should put in zero for a physical distance, you should instead use the Planck length). There are probably a bunch of other potential resolutions to the problem. I have no idea which (if any) of those ideas is the closest to the truth. :)

Jens
2009-Nov-13, 06:25 AM
Other potential solutions include Jens' suggestion (no matter how small a scale we look at, we'll never find point particles because they all have some internal structure), string theory (the fundamental particles are not points after all, but have some spatial extent, perhaps in multiple dimensions), maybe some kind of quantization of space (there's no such thing as a meaningful distance smaller than, say, the Planck length, so any place where you're thinking you should put in zero for a physical distance, you should instead use the Planck length).

The thing I like about my suggestion is that we have seen it before, whereas we haven't seen things shaped like strings emerge. So a sort of Occam's razor approach seems in a way to favor smaller particles. On the other hand, there are the results of particle experiments, which don't seem particularly encouraging for my suggestion. :)