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Author Topic: Antimatter  (Read 4324 times)

Offline Laith

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Antimatter
« on: 23/04/2006 02:53:34 »
Is there an easy way to explain to a non-scientist what antimatter is?


Laith


 

Offline Laith

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Re: Antimatter
« Reply #1 on: 23/04/2006 02:55:46 »
or maybe a "not very complicated"  way :)

Laith
 

another_someone

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Re: Antimatter
« Reply #2 on: 23/04/2006 13:58:00 »
I'll give it a go.

All the major primitive particles in the universe (electrons, protons, etc. - but not photons) have an exact opposite type, and this opposite type is known as anti-matter.

The first type of anti-particle that was discovered was the anti-electron, which is more commonly known as the positron (it is known as a positron because it looks just like an electron as all anti-matter carries exactly the same mass as the mass of its opposite particle but it had the opposite electrical charge, so while an electron is negatively charged, the positron is positively charged).

The thing about matter and anti-matter, apart from the fact that they have opposite charge, is that when they come in contact with each other, they destroy each other, and create a small explosion of gamma rays (if you had a lump of anti-matter, and an equal lump of ordinary matter, you could make a bomb many times more powerful than any atom bomb ever invented ofcourse, if you had a lump of anti-matter, you'd have to think carefully how you store it, because it you put it in an ordinary container of matter, it would just destroy its container).

One of the problems physicists have had to face up to is why there is more matter in the universe than anti-matter; because, if in the early universe, an equal amount of matter and anti-matter were to have been created, then each would have destroyed the other, and there would have been no universe as we know it.

Since matter behaves so much like anti-matter (apart from being oppositely charged), then it should have been as easy for the early universe to create anti-matter as to create matter.

One theory is that there is in fact an asymmetry in the way particles were created that means that it is slightly easier to create matter than anti-matter; so that in the early universe, a very slight amount of extra matter was created.  All of the anti-matter that was created was then destroyed by meeting up with an equal amount of matter, but the very small extra bit of matter survived because not enough anti-matter was created to destroy it.

The other theory is that maybe there is just as much anti-matter and matter in the universe, but somehow they have been separated into different regions of the universe.  Since normal matter and anti-matter look so much alike, one cannot easily tell at a distance whether something is matter or anti-matter.  Some people have theorised (though I must stress that this is not the most commonly accepted view at present) that there might be whole galaxies made up only of anti-matter; and so long as they do not come into contact with a galaxy made up of ordinary matter, then no-one can know whether they are made up of matter or anti-matter.

Sometimes, in high energy events, a small amount of anti-matter is created, even within our own area of the universe; but it is so small that it does not do a great deal of damage.

As I said above, the first type of anti-matter that was discovered was a positron, and this is sometimes created in some types of nuclear decay, when a proton in an unstable atomic isotope converts to a neutron, then it emits a positron in order to get rid of its electrical charge.

PET scanners use positrons (hence the name positron emission tomography) emitted by radioactive isotopes of carbon, nitrogen, or some other element that might be used within the body.  The positrons emitted are then detected when they collide with an electron, and give a small explosion of gamma rays.



George
« Last Edit: 23/04/2006 14:25:28 by another_someone »
 

Offline Laith

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Re: Antimatter
« Reply #3 on: 23/04/2006 15:43:43 »
Thank you George,
another question, is antimatter associated with any Time theories?


Laith
 

Offline Laith

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Re: Antimatter
« Reply #4 on: 23/04/2006 15:46:05 »
quote:
Originally posted by maz

wow. your so clever. can you explane what matter is?

thanks

Science does not know its debt to imagination




It sounds like muaz, he has the same name on his profile.

Laith
 

another_someone

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Re: Antimatter
« Reply #5 on: 23/04/2006 17:16:40 »
quote:
Originally posted by Laith

Thank you George,
another question, is antimatter associated with any Time theories?

Laith



Had you any particular time theory in mind?

I am not aware of anything, but then I am not a physicist, so there is much that I am not aware of.

If you can give me a hint as to what you thing might be the interrelation between anti-matter and time, then maybe I might either know, or know where to look it up (or maybe someone else might know)?

There seems to be some debate as to whether anti-matter might have some anti-gravity effects in the environment of matter (i.e. matter attracts matter, anti-matter attracts anti-matter, but matter and anti-matter repel each other).  The dominant theory I believe is that this is unlikely to be true, but it has not been either proven or disproven whether this is the case.  Certainly, if this was true, it might allow that there might be regions of anti-matter in the universe that would repel regions of matter, and so never run the risk of collision and mutual annihilation.



George
 

another_someone

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Re: Antimatter
« Reply #6 on: 23/04/2006 17:46:17 »
quote:
Originally posted by maz
can you explane what matter is?




This is both a trivially easy question to answer, and an impossibly difficult question to answer.

At the trivially easy level, matter is all the stuff that is around us, the keyboard upon which I type, the clothes that I wear, the very substance of my body, is all matter.

The more difficult question is why is matter the way it is; why does it behave as it does; what is it composed of that makes it behave so.  These are the sorts of questions that millions of scientists have been seeking to answer for as far back as there has been science.

In some ways, one might even argue that anti-matter is a form of matter (which is why I often contrasted it with normal matter, rather than contrasting it with matter as such).

Another term that has sometimes been used to describe anti-matter is contra-terrene matter to indicate that it is really also matter, but it is matter that is not of this Earth.

The more difficult relationship is that between matter and energy.  In ordinary life, what we regard as matter is something that is separate from energy; but what Einstein showed is that that which we think of as matter can be converted to that which we think of as energy (and visa versa), and so really the two are one and the same thing.



George
 

Offline Laith

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Re: Antimatter
« Reply #7 on: 24/04/2006 02:02:52 »
quote:
Originally posted by another_someone


Had you any particular time theory in mind?



Not really

I saw this on a science forum before i posted the question, maybe i got it wrong! could you explain?
 
quote:
Antimatter is often described as normal matter traveling backwards in time. What this means is simply that whatever normal matter does, antimatter does in a backwards manner so that if you take a motion picture of normal matter and run it backwards, it looks like antimatter.

One result is that the annihilation of matter and antimatter also looks a bit like normal matter turning around and traveling backwards in time in a different direction after emitting the energy of a photon.

In string theory all the particles can be described as the vibrational modes of strings in a ten dimensional space times so the vibrational mode of a particular antiparticle would look like the vibrational mode produced by playing a film of the vibrational mode of the corresponding particle, backwards.

http://www.thescienceforum.com/viewtopic.php?t=1804&highlight=antimatter
But The Naked Scientists forum is better :D

Laith
« Last Edit: 24/04/2006 02:35:22 by Laith »
 

another_someone

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Re: Antimatter
« Reply #8 on: 24/04/2006 04:15:18 »
quote:
Originally posted by Laith

I saw this on a science forum before i posted the question, maybe i got it wrong! could you explain?
 
quote:
Antimatter is often described as normal matter traveling backwards in time. What this means is simply that whatever normal matter does, antimatter does in a backwards manner so that if you take a motion picture of normal matter and run it backwards, it looks like antimatter.

One result is that the annihilation of matter and antimatter also looks a bit like normal matter turning around and traveling backwards in time in a different direction after emitting the energy of a photon.

In string theory all the particles can be described as the vibrational modes of strings in a ten dimensional space times so the vibrational mode of a particular antiparticle would look like the vibrational mode produced by playing a film of the vibrational mode of the corresponding particle, backwards.




Yes and no.

String theory is a highly complex theory that no-one has proven to work yet.  A lot of people say it looks nice on paper, but there is absolutely no experimental proof that it is a valid theory.

Intuitively, the idea that anti-matter might be matter with its time direction reversed does seem appealing.  As a nave non-physicist, looking at the idea would lead me to believe that if anti-matter is just matter moving backwards in time, then it should in fact have the property of anti-gravity (which, as I suggested earlier, is a theory that is also not yet proven or disproven).  It might also explain why the only particle (as far as I am aware) that does not have an anti-particle is the photon, since photons travel at the speed of light, where time stands still, and so can go neither forward nor backward (again, the original prediction of the existence of anti-matter was made by Paul Dirac when he was mixing quantum physics with relativity, and so he probably came up with a good mathematical reason within that why photons were excluded from this symmetry).

I am not exactly sure what is meant by playing a vibration backward, since to my nave mind, a vibration looks the same whether played forward or backward but as I said, I know nothing about string theory.

In simple terms, I am way out of my depth.


Actually, the more I think about this, the more interesting the implications of it seem to be.

I must say that I have not seen anything of this theory to explain anti-matter anywhere else, so I cannot say how accepted the idea is (remembering that string theory itself is not totally accepted everywhere).

If a particle and anti-particle annihilating each other can be viewed as a particle coming to a stop, and then being reflected backwards in time, it seems to me that pair production (where particle and anti-particle are spontaneously created from a large amount of energy) might be viewed as anti-matter that is moving backwards in time, coming to a dead stop, and then being reflected forward in time as an ordinary particle.  This would imply that matter and anti-matter are doing some sort of zig-zag in time, being reflected backwards and forwards.  This still doesn't seem to explain why there is more matter than anti-matter (if they are both the same thing, only one reflected from the other, then why are there not equal amounts of it); nor would it seem to explain how something like a proton can decay into a neutron and a positron without reflecting an electron (although, maybe one can view it as a pair production, where an electron and positron are both produced, but the electron is then captured by the proton in order to form the neutron).

As I say, I really don't know what I am talking about, but it does seem like an interesting idea.

quote:

http://www.thescienceforum.com/viewtopic.php?t=1804&highlight=antimatter
But The Naked Scientists forum is better :D

Laith



That's nice to know :D



George
« Last Edit: 24/04/2006 05:39:33 by another_someone »
 

Offline Laith

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Re: Antimatter
« Reply #9 on: 29/04/2006 06:40:10 »
thanks george, you've always been helpful with your answers

Laith
 

The Naked Scientists Forum

Re: Antimatter
« Reply #9 on: 29/04/2006 06:40:10 »

 

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