Interested in particle physics, having trouble understanding.

[Lexadrik]

Hello everyone.
After some time of using the internet for entertainment purposes, I decided it would be good to actually learn from it. I saw Sagan's Cosmos for the first time, and got very hooked up with Particle Physics.

I'm trying to understand but I'm having trouble getting the hang of the whole picture. I hope you can give me a hand.

I know that atoms are made up of protons neutrons and electrons. electrons are much more abundant and smaller than neutrons and electrons, etc.

also, that protons and neutrons are made up of quarks, while electrons are part of another group called leptons, along with neutrinos.

confusion begins when i read about antiquarks, mesons, and how all these things "spin" and "decay" and how nuclear forces act on them.

I have a hard time imagining how it all fits together.

Would someone explain to me how it all works? Wikipedia answered 10 questions but brought 100 more up.

If I need to read through other topics I will do so, I'd just like to be pointed in the right direction.

Thanks!

 

[khemist]

An electron IS a lepton (Taken from wiki: A lepton is an elementary particle and a fundamental constituent of matter). From what we know, it is an elementary particle (meaning it has no smaller "bits," unlike a proton which is made of quarks).

What do you mean that you "have a hard time imagining how it all fits together"?

 

[Lexadrik]

I mean for example;
I can imagine quarks bouncing around inside a proton,
I can imagine electrons rotating around the protons and neutrons,
I can imagine atoms grouping together to create the elements which in turn create molecules, etc etc.

but where can mesons be found, where do antiparticles come from? or when? also, how do weak nuclear force act on them? is it like with neutrons which make them able to overcome a proton's repelling force on each other inside the atom?

 

[khemist]

Well...

Quarks don't really "bounce" inside the proton, nor are electrons "rotating" around the nucleus.

I know electrons position is given by a wave functions, which you can square to get a probability, so it is more like a "probability cloud." I am not sure about quarks, but I think there is a force (strong nuclear force?) that is mediated by gluons. Antiparticles are just regular particles, but the sign is flipped. So a positron has the same mass, but opposite charge as an electron. I don't know too much about the weak nuclear force or mesons, but I am sure wikipedia would be a start. I just looked at the meson page. It is a lot of information, but unfortunately these kind of things don't have a very simple explanation.

 

[Vorde]

You're obviously interested in the subject, which is always a great thing. I think its great that more people are being exposed to Modern Physics, however the biggest problem is that people come in expecting that they will be told things, they will think about it, and they will make sense. This doesn't happen. Quantum Physics (And Relativistic physics, but in a different way) completely redefines what 'makes sense', and it requires a lot of thought and the acknowledgment that things work differently 'down there' for it to make sense.

For instance, you said you can imagine quarks bouncing around inside a proton, they don't actually do that. Each quark has a probability field, and they overlap to form a combination we call a proton or a neutron. Even the electrons don't actually orbit the nucleus of an atom, but rather exist all around in specific shells, everywhere in that shell at a given time.

Some of your questions can be answered easily: A meson is a combination of a quark and it's antiquark, they only live for a short time before they decay and they exist completely separately of atomic nuclei.

However the more and more you probe into particle physics the less and less satisfied you are going to be with you answers. This is something I am running into right now, I've always been more interested in Astronomy and Astrophysics (indeed, it's what I plan on pursuing as a career), but I also enjoy learning about particle physics. I can understand why a electron orbits in a shell and not as a defined particle, but then I ask something like 'how do photons mediate the electromagnetic force', I'm given an answer in unintelligible (to me) math.

Here is my advice, decide whether or not you are really interested in the subject. If you are, pick up some light books on the subject. Start with completely non-mathematical ones, and as you get more and more comfortable with the ideas, you can advance to more complex books. However be prepared that you are eventually going to hit the math barrier, where you won't be able to understand anything deeper without knowing all the complex math, but don't let that stop you, it's quite a while down the road.

 

[Lexadrik]

Thanks for your answers!

I was almost sure that if i didn't understand how things worked by just reading a wiki article; a forum post wouldn't change things a whole lot.

And yeah i was right, but that doesn't bother me, this is centuries of science in the works : P
the only remaining question is then; where do the rules of everything start to change as you said "down there", do i go look for particle physics? or is there another kind of physics that could serve as an introduction for it?

 

[Vorde]

Assuming you're not interested in the math of it (at least not yet!), you can pretty much jump in. However you should be careful not to jump in too fast, or else you'll be swamped by things you won't be able to understand. For starting books, I really don't know any good ones, the first book I read on the subject was QED by Richard Feynman, which is an amazing book, but it was a bit technical and I wouldn't immediately recommend it.

If I think of any good books, I'll add them.