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What's the difference between matter and antimatter?





anarhistu
Does anybody know what is the difference between the two?
Bikerman
Yes,
antimatter is made up of antiparticles. Normal particles - electrons and protons - have a mass, electrical charge (and a few other properties). Anti-matter particles have the same mass (and other properties) BUT they have the opposite charge.
An electron, for example, has a negative electrical charge. An anti-electron (called a positron) is exactly the same, but with a positive charge.
Likewise a proton has a positive charge. An antiproton is the same, but with a negative charge.

A group of anti-particles is what we call anti-matter. When anti-matter particles meet up with their equivalent matter particles (for example, an electron colliding with a positron), they annihilate each other in a 'puff' of energy.
anarhistu
Thanks, Bikerman, but...
Considering that there appear to be an asymmetry between matter and antimatter, there are speculations (as I've read) that there may be places in univers that are almost entirely antimatter. Do you have informations about this? I mean if this would be true, it would be like we would have a splitted univers: one part would be almost entirely matter, with small volume of antimatter; and the other part would be almost entirely antimatter with small volume of matter. In this situation... can there exist parts of the univers where is almost entirely antimatter and a little part of matter? And another question: How can small valumes of one of them coexist with big volumes of the other? What stops them from interacting?
Bikerman
anarhistu wrote:
Thanks, Bikerman, but...
Considering that there appear to be an asymmetry between matter and antimatter, there are speculations (as I've read) that there may be places in univers that are almost entirely antimatter. Do you have informations about this? I mean if this would be true, it would be like we would have a splitted univers: one part would be almost entirely matter, with small volume of antimatter; and the other part would be almost entirely antimatter with small volume of matter. In this situation... can there exist parts of the univers where is almost entirely antimatter and a little part of matter? And another question: How can small valumes of one of them coexist with big volumes of the other? What stops them from interacting?
Most physicists do not think that there are 'islands' of antimatter in the universe.
There are a few astrophysicists who believe there may be some remnants of antimatter in distant galaxies...for example:
http://www.astromart.com/news/news.asp?news_id=877

The mainstream theory is that the BB produced equal amounts of matter and antimatter. Due to a slight asymmetry some of the antimatter immediately decayed into photons, leaving a tiny amount more matter than antimatter (about 0.0000001%). When the matter and anti-matter annihilated there was still some matter left over - that is what we observe as the universe.
anarhistu
I haven't checked the link you provided yet, but I will check it soon. But, what I understand from your explanation, is that there is only matter left in the univers. ok. But how is it possible then that they are saying they found antimatter? Not really found, but found the evidence for the antimatter..
You said: Due to a slight asymmetry some of the antimatter immediately decayed into photons.
Is the photon antimatter or something like that? I do not want to seam stupid ( at lease not more than I already am...), but if photons are not antimatter, how can antimatter decayed into them? And what is that "decayed" related to? What exactly does it mean? Transformed? Or is the photon something like a 3rd phase? Matter, antimatter and photons?
Thank you very much for explanations.
Bikerman
Well, it gets complicated - it involves a basic asymmetry in nature called the CP violation. Basically, symmetry laws tell us that the laws of physics should work exactly the same if a particle (say an electron) is swapped for its antiparticle (the positron). CP violation says that this doesn't work - there is a very slight imbalance.
Now, when positrons and electrons meet you get electromagnetic 'energy' (photons) and nothing else (the same happens when protons and anti-protons meet).
anarhistu
So, if I understand correctly, when matter and antimatter "merge", they rezult in some form of energy force. Correct? If that's correct, if by combining matter and antimatter we get energy, it would mean that in the first moments after BB, the resultant of the big "explosion" was energy (without taking in discussion the space and the time). And then, somehow, the energy splitted into matter and antimatter. Correct? Regarding your explanation, I understand something like that:

first, there was an equal mass of matter and antimatter, that we shall name A (mass of matter) and B (mass of antimatter). Part of B decayed into photons. That means the final status of the B mass will be (B-q) where I name q for the part of antimatter that decayed into photons. Then, The total mass of (B-q) antimatter combined with the same mass from the A matter mass. That would result something like (q+B-q) mass of photons and (A-B+q) mass of matter.
Bikerman
That's pretty much it, yes.
The process is known as baryogenesis and you can read up in more depth using the wiki article
http://en.wikipedia.org/wiki/Baryogenesis

PS - the photons don't have 'mass' they simply have energy so you would need to consider using the formula E^2 = m^2.c^4 + p^2.c^2 (but that is another story)....
TrueFact
Modified as it is a repeated post. TrueFact
TrueFact
Well, after reading all this about anti-matter, i can think it is much similar to white holes. The same concept applies I mean. White holes, as what I've read, are the very opposite of black holes. White holes has a flipped field of force and push everything away including energy.

There are theories that say white holes are the far end of black holes. In other words, what black holes draw is sent somewhere else in the vast space which produces the white hole.

So is there any better information about it or a more detailed information? I've been searching the web and got a whole punch of contradictory information.
_AVG_
Building on that ... considering that there is a gravitational attractive force which is the main essence of a black hole, the main force associated with a white hole would be repulsive ... something like Anti-Gravity or something? Is that possible?
Indi
TrueFact wrote:
Well, after reading all this about anti-matter, i can think it is much similar to white holes. The same concept applies I mean. White holes, as what I've read, are the very opposite of black holes. White holes has a flipped field of force and push everything away including energy.

There are theories that say white holes are the far end of black holes. In other words, what black holes draw is sent somewhere else in the vast space which produces the white hole.

So is there any better information about it or a more detailed information? I've been searching the web and got a whole punch of contradictory information.

That is not correct. That definition of white holes is a common science fiction definition, but complete nonsense in real science. White holes (if they exist) do attract matter... they just don't suck it in.

If you can picture it, think of a "bubble", which is the event horizon, with a bunch of mass on the inside. In a black hole, that bubble is constantly growing as more matter gets sucked in. In a white hole, the matter inside is being spewed out as the bubble shrinks at the speed of light (so nothing can possibly get in). It's not pushing anything away. It's just pulling it less and less quickly as it collapses.

And no, the idea that black holes suck matter in and white holes spit it out somewhere else is impossible. It would require a wormhole to form with one end inside a black hole... but if that happened, the "tube" would be choked off by the extreme gravity of the black hole. You would end up with a wormhole no longer, just two singularities - one inside the black hole (where it doesn't matter any more because it is no longer part of our universe), and one outside which will collapse immediately.

For more detailed information on white holes i'm not sure where to point you. They are not exactly simple... to understand what is going on you need a fair bit of really in depth physics... and there is so much misinformation out there (usually science fiction being passed off as science, sometimes by people who honestly think it is correct) that i hesitate to just say google it.

_AVG_ wrote:
Building on that ... considering that there is a gravitational attractive force which is the main essence of a black hole, the main force associated with a white hole would be repulsive ... something like Anti-Gravity or something? Is that possible?

No, gravity acts only one way: attractively. There is no "antigravity". An anti-graviton is a graviton... they are one and the same. As i mentioned, the force associated with a white hole is still attractive.

But in theory? Well, in the case of electromagnetism, like charges repel, right? So two positive charges repel, while a positive and negative attract. But in the case of gravity, like masses attract: two positive masses attract each other. So our "common sense" breaks down: would two negative masses attract or repel? would a positive and negative mass repel? We just don't know. In modern science (the Standard Model - the current state of the art in physics), there are no particles with negative mass, and we are not even sure of what would happen if there were.
myviny
So we cant store anti matter in a container made of matter?? Sad

Interestingly, I read that we can produce anti matter in laboratory. In fact it has been already produced.

One question : why do we have a predominance of matter over antimatter.
_AVG_
Yes. I believe CERN have successfully produced Antihydrogen if I'm not wrong ... it costs some trillion dollars per gram ! Idea Rolling Eyes
Indi
myviny wrote:
So we cant store anti matter in a container made of matter?? Sad

Interestingly, I read that we can produce anti matter in laboratory. In fact it has been already produced.

As _AVG_ says, you're right.

We can't store them yet (as far as i know), but as for how they could store it, they could use magnetic fields and/or electric fields to hold the antiparticles in suspension. The problem is that the antiparticles we can produce are so energetic that they can't be held still enough in a magnetic field - they dance around so much they hit the sides of the container and annihilate. There are some ideas of how to solve this problem, like using lasers to slow down the positrons and antiprotons, but i don't know if they've managed to get it done yet.

The problem will only get worse as we try to create antiatoms like antihydrogen, antideuterium, antihelium and eventually bigger antiatoms. Fusion tends to require high energy collisions... resulting in high energy particles after collision.

myviny wrote:
One question : why do we have a predominance of matter over antimatter.

That's a trillion dollar question. ^_^ If you figure out the answer to it, then call Stockholm. Your Nobel Prize will be waiting for you.

This is one of the biggest unanswered questions in physics. We don't even know yet if it is a real problem though: it may be that there isn't a predominance of matter... it's just that we happen to live in a galactic cluster where matter outnumbered antimatter. In another galactic cluster, maybe it worked the other way around and there are whole antimatter galaxies, and even people, out there.

Or, maybe the universe is mostly matter... but then why? No one knows!
anarhistu
Indi wrote:
myviny wrote:
So we cant store anti matter in a container made of matter?? Sad

Interestingly, I read that we can produce anti matter in laboratory. In fact it has been already produced.

As _AVG_ says, you're right.

We can't store them yet (as far as i know), but as for how they could store it, they could use magnetic fields and/or electric fields to hold the antiparticles in suspension. The problem is that the antiparticles we can produce are so energetic that they can't be held still enough in a magnetic field - they dance around so much they hit the sides of the container and annihilate. There are some ideas of how to solve this problem, like using lasers to slow down the positrons and antiprotons, but i don't know if they've managed to get it done yet.

The problem will only get worse as we try to create antiatoms like antihydrogen, antideuterium, antihelium and eventually bigger antiatoms. Fusion tends to require high energy collisions... resulting in high energy particles after collision.

myviny wrote:
One question : why do we have a predominance of matter over antimatter.

That's a trillion dollar question. ^_^ If you figure out the answer to it, then call Stockholm. Your Nobel Prize will be waiting for you.

This is one of the biggest unanswered questions in physics. We don't even know yet if it is a real problem though: it may be that there isn't a predominance of matter... it's just that we happen to live in a galactic cluster where matter outnumbered antimatter. In another galactic cluster, maybe it worked the other way around and there are whole antimatter galaxies, and even people, out there.

Or, maybe the universe is mostly matter... but then why? No one knows!


Indi, I have some doubts about the idea that we may live in a galactic cluster where matter outnumbered antimatter and that there may be other galactic cluster(s) made up by antimatter. I mean doesn't seam logical to me. If we were living into a "matter" cluster and out there, somewhere, would exist a "antimatter" cluster... isn't it true that when matter meets antimatter they react themselves to energy? If the possibility of having in the same universe huge mass of matter and huge mass of antimatter would be true, there would need a very huge "force to keep them from interacting. Right? At least that's how I see the facts... maybe I am wrong!
About the predominance of matter, I believe there are at least one theory for that, in the BB Theory (if I am not mistaking very badly), presenting how there was a plus in the matter part and the antimatter combined with the similar "mass" of matter becoming the cosmic background (if I am not mistaking again) and he little rest of matter created the universe that we have around us...
Indi
anarhistu wrote:
Indi, I have some doubts about the idea that we may live in a galactic cluster where matter outnumbered antimatter and that there may be other galactic cluster(s) made up by antimatter. I mean doesn't seam logical to me. If we were living into a "matter" cluster and out there, somewhere, would exist a "antimatter" cluster... isn't it true that when matter meets antimatter they react themselves to energy? If the possibility of having in the same universe huge mass of matter and huge mass of antimatter would be true, there would need a very huge "force to keep them from interacting. Right? At least that's how I see the facts... maybe I am wrong!

It is true that matter and antimatter annihilate each other when they meet... however you are missing one very obvious implication of this. This annihilation can only happen when matter and antimatter meet! ^_^; You don't need any huge force. All you need is spacetime - distance. If matter and antimatter never meet, they never annihilate.

During the formation of the universe, it is possible that matter and antimatter may have been created at equal rates. But in all the seething and turmoil, it clumped up unevenly into pockets of matter and pockets of antimatter. This is no big stretch - we already know that some clumping happened... which is why we have galaxies and galactic clusters and big areas of almost empty space.

As the universe cooled and stretched, these separate clumps of matter and antimatter got further and further apart, making interaction less and less likely. Until now, today - the galaxies are so far apart that it is highly unlikely that any appreciable amount of matter from one galaxy ever reaches another.

Andromeda could be all antimatter... we would never know.

anarhistu wrote:
About the predominance of matter, I believe there are at least one theory for that, in the BB Theory (if I am not mistaking very badly), presenting how there was a plus in the matter part and the antimatter combined with the similar "mass" of matter becoming the cosmic background (if I am not mistaking again) and he little rest of matter created the universe that we have around us...

We don't actually know that there is a predominance of matter. We assume there is, but we don't actually know. There may be an exactly equal amount of matter and antimatter in the universe. Right now hundreds of experiments are underway around the world to measure the contents of the particles streaming past Earth. In fact, the biggest one ever was planned to go up to the International Space Station... but is now stuck without a ride because the shuttle fleet is retiring.

What all of these experiments involve are particle detectors in the upper atmosphere (or orbit) to check for the existence of larger anti-atoms. They pick up antiparticles all the time, but so far no anti-deuterium or anti-helium or anything larger. The chances of anti-helium forming in a matter galaxy are absurdly small, so if they detect any anti-helium, it would have had to have come from an antimatter galaxy. But even then, the anti-atom would have had to escape the gravity of its own galaxy (no small feat!), travel interstellar space, and then make it through our own galaxy to Earth without annihilating. If they find even one anti-helium atom, it will pretty much toss the idea of matter dominance right out the window.

In the meantime we are working on the assumption that matter does dominate... and we don't have any theory currently to explain why. All we have is a list of things that must be true if that happened. These are called the Sakharov conditions. Of the four conditions, we have only observed 2. The remaining two violate what we know of physics, but may have been true at the Big Bang.

We have been able to show that under certain conditions more matter is created than antimatter, but at nowhere near the rates required. But this was at low energy conditions - at high energy conditions things may be different... but we have no theory to even begin to explain how or even if this might happen.

It's all a big mystery at this point. We don't have any idea of what the solution for the problem may be... and we don't even have any idea if the problem even exists.
Bikerman
I'm going with the current 'standard theory' which posits that CP violations are responsible for the decay of some antimatter in the very early universe. The remaining antimatter then annihilates with matter to leave a bit of matter left over - the observable universe...

Here's a link to a sciencedaily article which might be of interest
http://www.sciencedaily.com/releases/2004/08/040803094110.htm
anarhistu
Thanks Indi for explaining those and Bikerman for the support link. But I am still a little unsure about everything. I agree with what you said, Indi, that there are huge distances between galaxies and that they might actually be dominated by matter, but also by antimatter. The thing that I do not understand is the following:
We consider, let's say, that we have our galaxy, A, dominated by matter (true fact, as we know - if I am not mistaking again) and another galaxy, B, dominated by antimatter, at approximately 20 million light years distance. We know that between the two galaxies there is a density very small. We may consider that the antimatter from galaxy B will never reach the matter from galaxy A? If what you said is true, if there may be galaxies dominated by antimatter and galaxies dominated by antimatter, we must also consider the radiations emitted by both of them. That would mean that, in case that the antimatter galaxy is somewhere between us and another matter dominated galaxy, we will never receive any evidence about that matter dominated galaxy, because it's radiations will be eliminated by the antimatter. Or am I wrong? Are there any kind of radiation that may be emitted by matter or antimatter and not interact with the other form? If I am right, and so were you and there are also matter galaxies or galaxy clusters, same as matter galaxies and clusters, that would mean that, in some directions, the universe would seam "smaller because we could not receive all the radiations sent by matter. And that we would only "see" the universe until the last form of matter before the antimatter formations.
Can you guys please tell if I am wrong here, where am I wrong and why?
Thanks!
Bogdan
Bikerman
No, the basic error is to assume that 'normal' em radiation would be affected by anti-matter. That is, that a photon has an 'anti-pair' that is distinguishable. Since a photon carries no charge then I don't see how you would distinguish a photon from an anti-photon....
Indi
Bikerman wrote:
I'm going with the current 'standard theory' which posits that CP violations are responsible for the decay of some antimatter in the very early universe.

i think responsible is stretching it - certainly CP violations are required, but they are not sufficient according to the current standard theory. CP violations are one of the Sakharov conditions (and along with charge violations, one of the the only ones we have actually observed).

The problem is that the rate of CP violations we have observed is way too small to explain the baryon asymmetry. There are only two possibilities for CP violations in the standard model, and the only other possibility gives theoretical a rate way too big. So we're stuck - the standard model offers two kinds of CP violations, one (actually observed) is way too small, the other (only theoretical) is way too big.

It's possible that at high energies the rates change to something more reasonable... but nothing in the standard model either suggests that they will change at all, let alone in the right direction. This is the ultraviolet catastrophe for the standard model - in order to explain the baryon asymmetry, we're going to have to go off the reservation and turn to next generation physics, although i honestly have no clue what string theory has to say about this, and even less clue about QLG.

anarhistu wrote:
We consider, let's say, that we have our galaxy, A, dominated by matter (true fact, as we know - if I am not mistaking again) and another galaxy, B, dominated by antimatter, at approximately 20 million light years distance. We know that between the two galaxies there is a density very small. We may consider that the antimatter from galaxy B will never reach the matter from galaxy A? If what you said is true, if there may be galaxies dominated by antimatter and galaxies dominated by antimatter, we must also consider the radiations emitted by both of them. That would mean that, in case that the antimatter galaxy is somewhere between us and another matter dominated galaxy, we will never receive any evidence about that matter dominated galaxy, because it's radiations will be eliminated by the antimatter. Or am I wrong? Are there any kind of radiation that may be emitted by matter or antimatter and not interact with the other form? If I am right, and so were you and there are also matter galaxies or galaxy clusters, same as matter galaxies and clusters, that would mean that, in some directions, the universe would seam "smaller because we could not receive all the radiations sent by matter. And that we would only "see" the universe until the last form of matter before the antimatter formations.
Can you guys please tell if I am wrong here, where am I wrong and why?

Actually, your thinking is absolutely correct, and in fact that was quite a brilliant leap in thinking.

You are absolutely right that matter galaxies will emit and absorb "matter radiation" and antimatter galaxies will emit and absorb "antimatter radiation". And actually that's exactly what we are looking for to suggest the existence of antimatter galaxies: we are looking for antimatter radiation. We are looking for antimatter radiation that cannot reasonably be created in a matter galaxy (like our own), which would suggest it had to come from an antimatter galaxy.

The thing is, that most of the radiation we can receive from distant galaxies tends to be either light/EM radiation (photons) or gravity (gravitons). This is for two reasons. First, these move at the speed of light, so they get here a lot quicker than, say, beta radiation or neutrinos. But more importantly, the antiparticles of photons and gravitons are... photons and gravitons. As Bikerman said, the photon's anti-partner is indistinguishable. So gravity and light interact with antimatter galaxies in exactly the same way as matter galaxies. To light and gravity, it doesn't matter if you're matter or antimatter.

So, to answer your questions one by one:

"That would mean that, in case that the antimatter galaxy is somewhere between us and another matter dominated galaxy, we will never receive any evidence about that matter dominated galaxy, because it's radiations will be eliminated by the antimatter. Or am I wrong?"
Half-right, half-wrong. ^_^ Some radiation will be eliminated (alpha, beta), some will not care whether the galaxy is matter or antimatter (em, gravity)... and some we're not quite sure about yet (neutrino). So we will not receive alpha particle radiation from a matter galaxy behind an antimatter galaxy, but we will receive em radiation, and neutrinos we're not sure yet.

"Are there any kind of radiation that may be emitted by matter or antimatter and not interact with the other form?"
Several! Alpha, beta, neutron radiation... all of these will be emitted and absorbed by matter, but will annihilate with antimatter (and antimatter will emit and absorb "anti-alpha", "anti-beta" and antineutron radiation that will annihilate with matter). But EM and gravity radiation will be absorbed and emitted by both matter and antimatter.

"If I am right, and so were you and there are also matter galaxies or galaxy clusters, same as matter galaxies and clusters, that would mean that, in some directions, the universe would seam "smaller because we could not receive all the radiations sent by matter."
Not necessarily - suppose there were two matter galaxies (A and B) close to each other, but far away from us, and between one of those galaxies (A) and us was an antimatter galaxy (C). Even if the antimatter galaxy (C) were "blocking" the matter galaxy (A) completely, we would still know it is there... because we could see the other galaxy (B) being affected by the first galaxy's (A's) gravity.

Code:
A ---------------- C ------------------ us
|
B

(can't see A, but can see B, and can tell that there is something massive close to B)


But what happens in reality is that we can see "around" galaxies anyway because the path of light is bent by their massive gravity. The phenomenon is called "gravitation lensing". So even if there were a matter galaxy behind an antimatter galaxy, we would still see it.

"And that we would only "see" the universe until the last form of matter before the antimatter formations."
That would be true if matter or antimatter galaxies really did "block" each other. But as i mentioned, they don't really, and even if they did, gravitational lensing would still let us see around them.
Xrave
well, what's an antimatter engine? is it the process of using antimatter to annihilate matter to create energy that is used to power an engine? but how's that going to help space flight?
Indi
Xrave wrote:
well, what's an antimatter engine? is it the process of using antimatter to annihilate matter to create energy that is used to power an engine? but how's that going to help space flight?

These are complicated questions, and they involve a lot of speculative physics.

The most basic idea of an antimatter engine is that it's basically just a steam engine or piston engine that gets its energy from antimatter annihilation rather than burning coal or gasoline. Of course, this won't help space flight much, because the problem with a "space drive" is not power, it's reaction. In space, there's nothing to push against.

One solution is based on the idea that when matter and antimatter combine, they release energy in the form of photons and mesons. These can be directed backwards, like rocket thrust, to push the spaceship forwards. Or they can be directed from the rear of the ship toward the back of the ship to push it from behind (for example, a light sail that is not transparent to gamma rays).

Or you can use a hybrid solution: use antimatter annihilation energy to heat up a standard reactant (like liquid oxygen) and blow that out the rear like a regular rocket.

There are also more speculative ideas based on the possibility that antimatter may have negative mass - and hence, negative gravity.

If you're thinking of something like Star Trek, i don't know how they're supposed to work, but from the technobabble i've caught, i gather that what they do is use antimatter annihilation to power an "electrical" generator, than then does some magic to "warp" (sub)space, creating thrust. So the Star Trek engine is just a standard nuclear submarine in space... except the nuclear reactor is replaced with an antimatter reactor, and the drive screws are replaced by nacelles that magically "warp" (sub)space.
RanVijay
contrary to popular belief, anti-matter is very real. when matter is made with particles, anti-matter is made of anti-particles. the difference between a particle and anti-particle is that certain quantum numbers are exactly opposite for a particle and its anti-particle. the mass and spin always remains the same.

have you heard about PET scan in large hospitals? this uses positron which is the anti-particle for electron. this is also the first anti-particle discovered by humans.
myviny
I think there have been a detection of antimatter from Supernovae. There was some report I read about some a neutrino and an anti-neutrino emission from a Supernova (my guess is on the one observed in 1987...seems to be a reasonable guess)

I also believe some nuclear processes result in the emission of a particle and the ani-particle but I guess the transience of its life makes it impossible to positively identify. Will have to look that up though.
classicevony
Quote:
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles. For example, an antielectron (a positron, an electron with a positive charge) and an antiproton (a proton with a negative charge) could form an antihydrogen atom in the same way that an electron and a proton form a normal matter hydrogen atom. Furthermore, mixing matter and antimatter would lead to the annihilation of both in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particle–antiparticle pairs.

There is considerable speculation as to why the observable universe is apparently almost entirely matter, whether there exist other places that are almost entirely antimatter instead, and what might be possible if antimatter could be harnessed, but at this time the apparent asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems in physics. The process by which this asymmetry between particles and antiparticles developed is called baryogenesis.

Source - http://en.wikipedia.org/wiki/Antimatter
[MOD - quote tags and source added - Bikerman]
_AVG_
A bit off-topic here:

Is the physical depiction of Antimatter in Angels and Demons somewhat true?

If it were released in the atmosphere would it cause such a catastrophic explosion?
welshsteve
Bikerman wrote:
Yes,
antimatter is made up of antiparticles. Normal particles - electrons and protons - have a mass, electrical charge (and a few other properties). Anti-matter particles have the same mass (and other properties) BUT they have the opposite charge.
An electron, for example, has a negative electrical charge. An anti-electron (called a positron) is exactly the same, but with a positive charge.
Likewise a proton has a positive charge. An antiproton is the same, but with a negative charge.

A group of anti-particles is what we call anti-matter. When anti-matter particles meet up with their equivalent matter particles (for example, an electron colliding with a positron), they annihilate each other in a 'puff' of energy.


Great explanation Smile

_AVG_ wrote:
A bit off-topic here:

Is the physical depiction of Antimatter in Angels and Demons somewhat true?

If it were released in the atmosphere would it cause such a catastrophic explosion?


Depends how much of it there is I guess.
Indi
_AVG_ wrote:
A bit off-topic here:

Is the physical depiction of Antimatter in Angels and Demons somewhat true?

If it were released in the atmosphere would it cause such a catastrophic explosion?

i don't have the script on hand so i don't know how much antimatter Obi Wan was carrying around, but i do recall reading several science writers commenting that the numbers were right. Meaning that whatever quantity of antimatter Obi Wan released in the atmosphere, it would produce a comparable explosion to what was shown, and the rhetoric about how much destruction would be wrought on Vatican City should it be released within the city was probably correct. In fact, i recall some people pointing out that Dan Brown (and/or Ron Howard) underestimated the destructive power.

Where Angels & Demons strayed well into fantasy (in my opinion), was that such an amount is absurd. They were walking around with a pea-sized lump of the stuff! Good freaking grief! We can only produce tiny fractions of a microgram of the stuff every year, and we can't really store it all that well.

If you have a copy of the movie or the book, crunch the numbers yourself: find out the mass of antimatter stolen, multiply by 2 to take into account the regular matter that gets annihilated along with the antimatter, plug that value into Einstein's equation and you'll get the energy of the explosion. You might want to convert that to tonnes of TNT (multiply the result in Joules by 2.3900574 × 10⁻¹⁰) to compare it to explosive weapon yields:

MOAB (largest non-nuclear bomb): 11 T (tonnes of TNT)
Hiroshima (Little Boy): 15 kT
Nagasaki (Fat Man): 21 kT
Hydrogen bombs: 10 MT+
7of9
Reading through this forum im seeing alot of people saying that using an antimatter to produce energy is impossible and for now i would totally agree although you have to remember that this is a new technology to us but at the rate that the human race is technologically evolving i wouldnt be surprised if we found a way. Theoretically speaking if we can produce an antimatter explosion and find a way to contain in then it would only be a matter of time before we found a way to harness the energies released by said explosion. The possabilities for antimatter use are endless if we can progress in our understanding of what we are doing.
Bluedoll
Quote:
there are a lot of interesting things one can do with low energy antiprotons, and low energy (low speed) is definitely the only way to directly test the presumed symmetry between matter and antimatter.
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html

Well I notice in these kinds of threads a lot is theoretical. One has to be careful to treat fact and theory differently. Take for instance, the actually existence of antimatter. Are we talking about 6 or 7 little things? That is not much and can they do what they are suppose to? Or do we actually know for sure that in space such things even exist?
Quote:
Scientists claim antimatter is the costliest material to make.[27] In 2006, Gerald Smith estimated $250 million could produce 10 milligrams of positrons[28] (equivalent to $25 billion per gram); and in 1999 NASA gave a figure of $62.5 trillion per gram of antihydrogen
http://en.wikipedia.org/wiki/Antimatter#Cost

To talk about anti anything is temperature dependent ? All this time and money spent on something when all the time Canadian’s already knew how to make anti – freeze. Just, steal her long underwear!
Bikerman
Bluedoll wrote:
Quote:
there are a lot of interesting things one can do with low energy antiprotons, and low energy (low speed) is definitely the only way to directly test the presumed symmetry between matter and antimatter.
http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html

Well I notice in these kinds of threads a lot is theoretical. One has to be careful to treat fact and theory differently. Take for instance, the actually existence of antimatter. Are we talking about 6 or 7 little things? That is not much and can they do what they are suppose to? Or do we actually know for sure that in space such things even exist?
Actually one has to be careful to understand what theory means. In the scientific usage it is not incompatible with 'fact' and doesn't need to be treated differently at all.
I don't know what '6 or 7 little things' is supposed to mean. Particles have anti-particles associated with them. We can manufacture some of these in the lab. We do not see anti-particles in nature for the obvious reason that they would immediately annihilate by interacting with the associated particles.
7of9
To state that Anti-Particles do not exist in nature in truth is only assumption theres no evidence to say that they dont, we dont know enough about the universe to say for sure whether anti-particles exist in a natural form, please try to remember that the universe is infinately expanding and we have barely even scratched the surface when we talk about space and whats out there all we are trully doing is speculating and until we can get out there and explore it in a physical sense that is all we will be doing.
Indi
7of9 wrote:
To state that Anti-Particles do not exist in nature in truth is only assumption theres no evidence to say that they dont, we dont know enough about the universe to say for sure whether anti-particles exist in a natural form, please try to remember that the universe is infinately expanding and we have barely even scratched the surface when we talk about space and whats out there all we are trully doing is speculating and until we can get out there and explore it in a physical sense that is all we will be doing.

No, that's not true. We know that anti-particles exist in nature - we see them all the time. We don't know if antimatter galaxies exist, but we certainly see natural anti-particles all the time.
Bikerman
Yes, I should have been more specific. We don't see anti-particles in quantities/conditions which make it possible to 'grab' them. One example of routine use of anti-particles is the PET scanner. It effectively utilises anti-electrons (positrons) to image the body.
gphoenix
Woh!

The fact is that i get a serious head ache when i read these stuff..

never knew about animatter !!
kelseymh
(Just found this topic; Bikerman already answered the original question just fine.)

7of9 wrote:
Reading through this forum im seeing alot of people saying that using an antimatter to produce energy is impossible and for now i would totally agree although you have to remember that this is a new technology to us but at the rate that the human race is technologically evolving i wouldnt be surprised if we found a way. Theoretically speaking if we can produce an antimatter explosion and find a way to contain in then it would only be a matter of time before we found a way to harness the energies released by said explosion. The possabilities for antimatter use are endless if we can progress in our understanding of what we are doing.


Using antimatter on Earth to "produce energy" is impossible. Now and forever. The reason is simple and based entirely in logic, not in technology. Such a device will require far more energy as input than you can possibly get out of it, even assuming 100% efficiency.

You have to make the antimatter before you can use it.

To make antimatter, you need energy, a whole heaping lot of it. Remember those 1.12 gigawatts from Back to the Future? That's negligible compared to the energy needed to produce mass quantities of antimatter.

To make antimatter (and this is something I do for a living, as a particle physicist at SLAC), you need some form of highly concentrated energy density, high enough that it will (occasionally!) spontaneously produce particle-antiparticle pairs, either electrons and positrons, or protons and antiprotons. The physical processes involved (this isn't technology, it's physics) are about 50% efficient for positrons (bremsstrahlung with an electron beam on target followed by pair-production by the cascade photons), but only a few parts per million efficient for antiprotons (proton-nucleus collisions producing p-pbar pairs in the fragmentation). Basically you need to accelerate millions of protons to very high energy, in order to get just one or two antiprotons out.

Once you produce your supply of antimatter, you need to store it. You can't store it in matter, so you have to use electric and magnetic fields inside a vacuum chamber. It takes energy to produce and maintain the electric currents which produce those fields. If you use superconductors to maintain the currents, you still need energy to run the refrigerators. You also need energy to run the vacuum pumps. So you're burning more energy to store the antimatter before you put it into your generator.

When you do finally annihilate the matter and antimatter, in the form of very dilute gases, this part of the process can be 100% efficient. All the antimatter can be turned back into energy, which you can harvest with appropriate devices and distribute.

But the total energy used in the process is far greater than the little bit you get trickling out at the end. It doesn't matter what technology you use for each stage of the process. The efficiencies I quoted are the maximum possible, based on the underly physics. The real energy cost (for example, at SLAC, Fermilab and CERN) today is much greater still.
therimalaya
I don't know much about it, but i'm wondering about the antiparticle of gravity.. If would have exit we can fly out of anywhere using it. (I assume that is is repelled with graviton)
kelseymh
therimalaya wrote:
I don't know much about it


Or anything else of the dozen posts you made in the past hour...

Quote:
but i'm wondering about the antiparticle of gravity.. If would have exit we can fly out of anywhere using it. (I assume that is is repelled with graviton)


There isn't one. The (hypothesized) graviton is a spin-2 neutral boson which is its own antiparticle.

And before you come up with yet another unwarranted and ignorant "assumption," the field equations operate on the stress-energy tensor. Since "anti-particles" have positive mass and energy (we know this because we use energy to create them trillions of times per second at SLAC, Fermilab, CERN, and elsewhere), they are necessarily affected by gravity the same way particles of "matter" are affected.
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