10 May 09
From the Wikipedia page on positrons:
Today, positrons, created through the decay of a radioactive tracer, are detected in positron emission tomography (PET) scanners used in hospitals and in accelerator physics laboratories used in electron-positron collider experiments. In the case of PET scanners, positrons provide a mechanism to show areas of activity within the human brain. In addition to the two above-mentioned applications of positrons in medicine and fundamental physics, an experimental tool called positron annihilation spectroscopy (sometimes referred to as PAS) is used in materials research.
New research has dramatically increased the quantity of positrons that experimentalists can produce. Physicists at the Lawrence Livemore National Laboratory in California have used a short, ultra-intense laser to irradiate a millimetre-thick gold target and produce more than 100 billion positrons.[4][5]
12 May 09
Originally posted by utherpendragonAntimatter is unstable in this solar system due to it's immediate combination with matter, a process called anihilation.
is there a way to harness antimatter? if so please explain,or if not.
Keep in mind though, for all the matter on the earth and other planets, there is exactly the same amount of antimatter out there somewhere.
12 May 09
Originally posted by mlpriorAntimatter is just as stable as regular matter, but precisely because you are wrong with your second point (there is in fact more matter than antimatter, at least as far as we can measure) it usually doesn't exist for very long.
Antimatter is unstable in this solar system due to it's immediate combination with matter, a process called anihilation.
Keep in mind though, for all the matter on the earth and other planets, there is exactly the same amount of antimatter out there somewhere.
12 May 09
Originally posted by mlpriori heard something like that. how does that fit in w/the other example being used in hospital equipment and such.is this the same stuff we r talking about?
Antimatter is unstable in this solar system due to it's immediate combination with matter, a process called anihilation.
Keep in mind though, for all the matter on the earth and other planets, there is exactly the same amount of antimatter out there somewhere.
12 May 09
Originally posted by AThousandYoungYes, charged antimatter can be contained in storage rings using magnetic fields.
Antimatter can be held away from ordinary matter via magnetic fields I believe. Using this sort of technology, antimatter might be usable as a source of energy in the future.
As a source of energy antimatter is useless, since there is no way to "harvest" antimatter without first using some energy source to produce it. There are natural sources of antimatter (particularly positrons, but also positive muons and pions - pions consist of a combination of matter and antimatter), but none that can be used for energy generation in a sensible way.
13 May 09
Originally posted by KazetNagorraDepends on if you have dilithium crystals or not. It´s worth mentioning that it is quite easy to create positrons and anti-protons and so forth, but the quantities they can be created in are tiny. The packets they send round accelerators contain around of the order of a few hundred thousand particles per packet(*). PET scans do not use this. They use artificially created radio-active isotopes of oxygen which decay by positron emission and the detector sees the 500 keV gamma rays emitted by annihilation events. There is no feasible way of producing anti-matter as energy storage as a way of providing electricity - and as you say there is still the problem of producing the energy in the first place.
Yes, charged antimatter can be contained in storage rings using magnetic fields.
As a source of energy antimatter is useless, since there is no way to "harvest" antimatter without first using some energy source to produce it. There are natural sources of antimatter (particularly positrons, but also positive muons and pions - pions consist of a combin ...[text shortened]... of matter and antimatter), but none that can be used for energy generation in a sensible way.
(*) This is from memory, I could easily be wrong by 6 orders of magnitude in either direction.
13 May 09
Originally posted by KazetNagorraAntimatter is unstable in our world, as I said, because everything is made up of matter.
Antimatter is just as stable as regular matter, but precisely because you are wrong with your second point (there is in fact more matter than antimatter, at least as far as we can measure) it usually doesn't exist for very long.
There is more matter in our world, because our planet and solar system are made up of matter.
In theory, there is the exact same amount of antimatter existing in space somewhere. This is because for every amount of matter that is created, the equal and opposite antimatter is created. This has been proven already. So if our solar system is completely made up of matter, there is another solar system out there with the same amount of antimatter.
13 May 09
Originally posted by mlpriorso ,in this opposite solar system of anti- matter,there could be life? like anti- matter aliens?
Antimatter is unstable in our world, as I said, because everything is made up of matter.
There is more matter in our world, because our planet and solar system are made up of matter.
In theory, there is the exact same amount of antimatter existing in space somewhere. This is because for every amount of matter that is created, the equal and opposite ...[text shortened]... y made up of matter, there is another solar system out there with the same amount of antimatter.
13 May 09
Originally posted by mlpriorThere is something called baryon asymmetry. Meaning that this is not the case: There are *not* as much anti-matter than ordinary matter.
In theory, there is the exact same amount of antimatter existing in space somewhere. This is because for every amount of matter that is created, the equal and opposite antimatter is created. This has been proven already.
If there is as much antimatter as there is ordinary matter, then they have to be out of touch from eachother to avoid total inhilation. Therefore one region (or more) of universe might be antimatter dominated, and another region (or more) of universe might be matter dominated. (We live, by definition, in the matter dominated region, of course.) These regions must be separated from eachother in a vast emptiness in order to avoid eachother. However, in an early universe with a smaller universe and consequently higher density they have to be in touch of eachother. However, this must be observationable in the background radiation. It isn't. So the explanation of baryon asymmetry is very probable.
The theory says that in the early universe, right after teh BigBang, it produced about one extra matter particle per billion matter-antimatter particle pairs. Every pair of matter anti-matter particle was destroid in radiation. The on remaining matter particle was enough to form the universe that we see today.
About antimatter as an energy source:
Yes, antimatter has very much energy, wen released conveting it's mass to pure energy as the E=mc2 dictates. However, to produce antimatter need a lot more energy that it contains later. Dan Brown in his book "Angels & Demons" was completely wrong.
However, if you want to store maximum of energy per mass unit, used as a fuel, and are willing to pay for it, it's of course possible. One application can be space travels propelled by anti-matter.
13 May 09
Originally posted by mlpriorAntimatter is unstable in our world, as I said, because everything is made up of matter.
Antimatter is unstable in our world, as I said, because everything is made up of matter.
There is more matter in our world, because our planet and solar system are made up of matter.
In theory, there is the exact same amount of antimatter existing in space somewhere. This is because for every amount of matter that is created, the equal and opposite ...[text shortened]... y made up of matter, there is another solar system out there with the same amount of antimatter.
No. In fact, there's a whole bunch of antimatter in your body right now. Positrons from radioactive decay, pions holding the nuclei together, antineutrinos passing through your body, ...
This has been proven already.
May I see this proof?
13 May 09
Originally posted by mlpriorNo it hasn't been proven. What has been proven is that waht we call matter is much more prevalent than anti-matter in our Universe.
In theory, there is the exact same amount of antimatter existing in space somewhere. This is because for every amount of matter that is created, the equal and opposite antimatter is created. This has been proven already.
And your definition of unstable isn't a good one. Because when anti-matter ceases to exist due to contact with normal matter, this normal matter also ceases to exist. Yes, since ordinary matter is much more prevalent in our neck of the woods I get what you mean by anti-matter being unstable, but strictly speaking it is incorrect.
14 May 09
Originally posted by KazetNagorraYes, in fact antimatter is unstable in a world made up of matter because it immediately combines and anhililates. I did not say that it does not exist and it does for a very small time. I said that it is unstable.
[b]Antimatter is unstable in our world, as I said, because everything is made up of matter.
No. In fact, there's a whole bunch of antimatter in your body right now. Positrons from radioactive decay, pions holding the nuclei together, antineutrinos passing through your body, ...
This has been proven already.
May I see this proof?[/b]
http://conferences.fnal.gov/lp2003/forthepublic/matter/