misskitty
I've heard about anti-protons and anti-electrons. The particles of the same mass but opposite charges. When they combine they create energy because their charges cancel them out. I can understand that. However, when I was talking with a physicist who goes to weekly home groups with my mother-in-law...he said something about anti-neutrons! How is this even possible? If a neutron is a particle with no net charge then how can there be an anti-neutron? I think he was trying to get a rise out of me. What purpose would it serve? Let me know your thoughts

~Kitty

Staff Emeritus
misskitty said:
I've heard about anti-protons and anti-electrons. The particles of the same mass but opposite charges. When they combine they create energy because their charges cancel them out. I can understand that. However, when I was talking with a physicist who goes to weekly home groups with my mother-in-law...he said something about anti-neutrons! How is this even possible? If a neutron is a particle with no net charge then how can there be an anti-neutron? I think he was trying to get a rise out of me. What purpose would it serve? Let me know your thoughts

~Kitty

An antiparticle need NOT be the property of charge particles only. A neutrino has an antineutrino. Yet, it is a neutral particle. This means that having an opposite charge is only but one of the possible properties of particles and antiparticles. Suffice to say that for every elementary particle that we have, there's an antiparticle counterpart, be it charged or not.

As for a neutron, all you need to know is that it is composed of three quarks, udd (up, down, down). If you instead have anti-quarks for those three, you have an antineutron. Voila! It isn't that mysterious.

Zz.

wolverine
Hi

Differences between particles and antiparticles are not only the electrical charge but all kind of "charges". Basically, if a proton got a baryonic charge of +1, the antiproton will get a baryonic charge B of -1.
For instance, in beta decay, there is conservation of the letponic charge L:
n -> p + e- + (anti)v
L 0 0 +1 -1
B +1 +1 0 0

The positron e+ get a leptonic charge of -1 and an electric charge of +1 (all these quantities are the oposite of the particle's one).

Hope it was clear.

misskitty
So what can you do with anti-particles?

~Kitty

Staff Emeritus
misskitty said:
So what can you do with anti-particles?

~Kitty
Well, for one, understand them, as they relate to the corresponding 'normal' matter.

For another, use them in experiments which are used to develop and understanding of matter and the fundamental forces of nature.

Yet another - anti-matter could be used (not practical at the present time) as an energy storage medium. Combining matter and antimatter has been envisioned as an possible means for spacecraft propulsion. However, the production of anti-matter is not very efficient, nor is the production rate very significant, and storing quantities of antimatter is still problematic.

We are still trying to find collections of antimatter elsewhere in the universe.

One question from the origin of the universe is - "Were equal amounts of matter and anti-matter created?"

WhiteWolf
But since it matter converts its antimatter counterparts into 100% energy, which is absolutely astronomical, if antimatter were found, like there are those that believe that they have seen concentrations of such in space, then it would only take a very small amount to provide vast amounts of power.

Is it possible to control virtual particles?

Staff Emeritus
Some cosmologists have speculated that could be regions in the universe made entirely of anti-matter. However, those regions could be several billion light years away, and somewhat isolated from what we call normal matter. Again, this is speculation, and I am not up to date on where that hypothesis.

Yes, if anti-matter could be obtained in substantial quantities, it would provide enormous amounts of energy.

As for virtual particles, by their very nature, I don't think they can be 'controlled', as in stored. Particles like baryonic resonances, pions and muons decay with extremely short life-times.

misskitty
Astronuc, if there are said places in the universe where such quantities of anti-matter exist why are they all clumped together instead of dispersed more freely around the universe? What might cause them to group together in a mass quantity like that?

Could there be a force that would cause the anti-particles to form anti-atoms? I'm not sure what I typed makes sense, but if the anti-particles are the counterparts for particles then would it not be reasonable to think they might form atoms with anti-electrons orbiting their nuclei? Would it be correct to assume the laws of physics would apply to anti-matter as well causing it to be affected the same way as matter? I'm not sure if I am making sense. This could become a very in-depth discussion...nothing wrong with that by any means though.

I got lost on the virtual particle portion so I will have to go chek out Marlon's thread.

~Kitty

Norman
Misskitty,

The reason that there are regions of this anti-particles, rather why there might be regions, is that if they were dispersed throughout the universe it would combine with regular particles and annihilate. They will theoretically combine to form atoms, in fact I have heard it said there might be whole stars made of anti-particles...
The reason they would group together is the same reason we have groups of mass around us- gravity. And yes, the laws of physics apply equally well to antiparticles as they do to regular particles.

hope this helps.
Cheers.

misskitty
It does. Thanks Norman.

If the anti-particles can theoretically combine to create atoms wouldn't it be easier to detect those than it would the particles themselves? Working on that theory there could be an entire perodic table of anti-elements so to speak.

Is there a way to test for such atoms?

~Kitty

Norman
I believe there would be a whole new periodic table of elements, but the likely hood of the actual anti-particle star is very small I think. But, that doesn't mean it is impossible. An astronomer might be able to say something about the possibility of observing a part of the galaxy that is predominantly anti-particles. I believe one way would be to observe a flux of anti-neutrinos from a star. Since neutrinos are released in nuclear fusion (see http://fusedweb.pppl.gov/CPEP/Chart_Pages/2.TwoFusionReactions.html [Broken] if you are unfamiliar with fusion processes), if an anti-particle star existed, I think it would release anti-neutrinos. Since neutrinos and anti-neutrinos are so weakly interacting, they have a chance of traveling astronomical distances without interacting. Thus allowing us to observe the presence of a possible anti-particle star. That is just one idea... detecting neutrinos is very difficult anyways, and the probability of an anti-neutrino reaching us would, I believe, be very small.

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Zelos
the reason main why neutron have a anti parter is that its not really a "particle" its made up by smaller particles called quarks. believe it or not but a quark don't have integer charges like electron, positron or protons. i think it were up quark that have +2/3 and down that have -1/3. and a proton is made up by 2 up and 1 down (simple written as uud, up up down) which would give a net charge of:
2/3+2/3-1/3=(2+2-1)/3=3/3=+1
while the neutron is made up by ddu quarks, so the charge become:
2/3-1/3-1/3=(2-1-1)/3=0/3=0
so it becomes neutral. but with the anti particles of the quarks it still become neutral. So a neutron do have particles or anti particles in it but it doesn't matter what it have iot will allways be neutral. unlike proton and electron.

Symbreak
There has been some debate over where the anti-particles of the Universe are located, with a suggestion that they are 'clumped up' at particular parts of the Universe. However, this goes against the principle that the Universe is homogeneous and isotropic on the largescale. Moreover, at its origin particles and antipartilces were created together so must be distributed equally.

But another alternative is to say the antiparticles have simply not formed into atomic nuclei. Would it be possible for the antiparticle action (the negative charge and parity) to be in a field, which is uniform but exists so that particles cannot annihilate because the field is not localised? Perhaps Dirac's antimatter field might be a pointer in the right direction?

Staff Emeritus
misskitty said:
If the anti-particles can theoretically combine to create atoms wouldn't it be easier to detect those than it would the particles themselves? Working on that theory there could be an entire perodic table of anti-elements so to speak.

Is there a way to test for such atoms?

~Kitty
The only way we can 'see' what's far out in space, is by virtue of electromagetic radiation (infrared, visible, UV, X-ray, gamma-ray) and neutrinos/anti-neutrinos traveling to us.

Photons are their own anti-particles, so we cannot distinguish between matter and anti-matter by photons alone.

AFAIK, anti-hydrogen atom radiates the same photons as a 'normal' H atom, and similarly for other anti-matter elements, if they exist.

Anti-particles are difficult to store, and more difficult to bring together to form larger atoms and molecules. Anti-neutrons have no charge so they can only slow by collision, and the only practical medium for that would be anti-hydrogen - which would produce anti-deuterium or anti-tritium (if an anti-d absorbed an anti-neutron), which would decay into anti-He3.

Possibly trying to build neutrino/anti-neutrino coincidence detectors, but neutrinos have such a low interaction rate with matter that it may not be detectable.

Zelos
one way to detect huge amount of antimatter is to detect huge amount of gamma radiation from the annilathion between antimatter and matter. the universe favor the matters existens cause nuclear processes at high energy create more matter than anti matter. about 1 million and one matter atoms per million antimatter atoms. If there would beentire galaxies of antimatter creation of galaxies according to the hierical model wouldn't be possible, imagen a galaxy and anti-galaxy bieng dragged to each other by gravity and begin having contact. the annilatoin would be enourmus and create huge amount of gamma radition. Wouldnt surprice me if it were possible to detect it at the other side of the unvierse if it happened.

misskitty
Zelos said:
the reason main why neutron have a anti parter is that its not really a "particle" its made up by smaller particles called quarks. believe it or not but a quark don't have integer charges like electron, positron or protons. i think it were up quark that have +2/3 and down that have -1/3. and a proton is made up by 2 up and 1 down (simple written as uud, up up down) which would give a net charge of:
2/3+2/3-1/3=(2+2-1)/3=3/3=+1
while the neutron is made up by ddu quarks, so the charge become:
2/3-1/3-1/3=(2-1-1)/3=0/3=0
so it becomes neutral. but with the anti particles of the quarks it still become neutral. So a neutron do have particles or anti particles in it but it doesn't matter what it have iot will allways be neutral. unlike proton and electron.

I was reading about this yesterday. Its really interesting. I was wondering why quarks only have a fractional charge. The way they combine to create a whole number charge makes sense, but why only fractional? The other question I had was since only part of the mass of a particle comes from the mass of the quarks (which is extremely small) where does the rest of the mass come from? I though it might be the binding energy which holds the quarks together, but that is too much mass for the binding energy to create that much of a mass defect.

~Kitty

misskitty
Astronuc said:
The only way we can 'see' what's far out in space, is by virtue of electromagetic radiation (infrared, visible, UV, X-ray, gamma-ray) and neutrinos/anti-neutrinos traveling to us.

Photons are their own anti-particles, so we cannot distinguish between matter and anti-matter by photons alone.

AFAIK, anti-hydrogen atom radiates the same photons as a 'normal' H atom, and similarly for other anti-matter elements, if they exist.

Anti-particles are difficult to store, and more difficult to bring together to form larger atoms and molecules. Anti-neutrons have no charge so they can only slow by collision, and the only practical medium for that would be anti-hydrogen - which would produce anti-deuterium or anti-tritium (if an anti-d absorbed an anti-neutron), which would decay into anti-He3.

Possibly trying to build neutrino/anti-neutrino coincidence detectors, but neutrinos have such a low interaction rate with matter that it may not be detectable.

I can see your point. I think. I've had a long few days . Anyway, the anti-d would difficult to store, but how would you even go about that? It would have to be some kind of container, but how would you know the contents of the container won't react with the container itself? Thus defeating the whole point. Do we have anything in use at this time using EM radiation to dectect anti-matter? BTW, does 'AFAIK' stand for anything?

~Kitty

misskitty
Zelos, the statistic of matter to anti-matter is so disproportioned! I know there is much more matter than anti-matter, but that is the first actual figure I have heard (or in this case read). Where did you come up with that particular figure?

Has anyone begun to speculate why there is so much more matter than anti-matter?

~Kitty

Antiphon
misskitty said:
BTW, does 'AFAIK' stand for anything?

As far as I know, it stands for As Far As I Know.

misskitty
Never heard of that akcronym (sp?) before. I'll have to remember that one.

~Kitty

kiru
As for a neutron, all you need to know is that it is composed of three quarks, udd (up, down, down)..

Is the existence of quarks experimentally verified?

Norman
kiru said:
Is the existence of quarks experimentally verified?

Yes. I believe the first was done at SLAC which suggested that the neutron, which is electrically neutral, had electrically charged constiuents that they called partons.
Take a look at these:
http://www.nikhef.nl/pub/experiments/zeus/theses/wouter_verkerke/latex2html/node3.html
http://intranet1.sutcol.ac.uk:888/NEC/MATERIAL/PDFS/PHYSICS/ASPHYS/14U1_T7.PDF [Broken]

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