What is antimatter?

[SpaceXray]

I recently found Dan Brown's book "Angels and Demons".

I've seen the movie before(which is pretty good, don't understand the hate), and antimatter was featured in both. The book claims that it is basically "opposite" matter, whose atoms' electrons are charged oppositely. Also it claims that antimatter, when coming in contact with matter, neutralizes and release photons. The same was said by a teacher at my science camp. Although, in the book(and movie) they say that it also neutralizes matter around. Also how exactly do you use it to get electricity? Say you get the photons during neutralization, but how do you convert them into electric current?

How exactly does antimatter work? Has anyone ever succeeded in getting it? Is it possible?

[SargeRho]

Antimatter is simply Matter with opposite charge. Anti-Electrons (Positrons) are positively charged, and anti-protons are negatively charged. When Matter and Antimatter come into contact, all of the energy contained within them is released in a process called Annihilation. Only particles and their antiparticles annihilate, so a positron and a proton won't annihilate, neither will and electron with an anti-proton. When Positrons and Electrons annihilate, it produces pure gamma rays. Protons and their antiparticles produce gamma rays as well as a myriad of particles.

There are multiple ways to produce antimatter. You can smack really heavy nuclei together, you can smack really heavy nuclei into really heavy stuff (like gold or lead), you can use lasers to produce electron-positron pairs, and there are some radioactive isotopes that naturally produce positrons. PET scans use the gamma rays resulting from the annihilation of the positrons produced by a radionuclide.

A universe made of antimatter would look exactly like ours.

[dbmorpher]

NONONONONONONONONONONONONONONONONONONOOOOOOOO!!!!!!

BURN THAT BOOK

Sorry I'm Catholic and all those stupid conspiracy theories make everyone think bad of me and my fellow papist friends.

Anyways scientifically antimatter is the opposite, electric charge wise, from normal matter. The thing is antimatter does vaporize when in contact to normal matter. This "vaporization" is actually all of the mass of the two particles (The antiparticle and particle) in energy form. This energy is in the form of gamma radiation, gamma rays are notorious for destroying things but don't "neutralize" that's just bad technobabble.

For your last question, yes it is possible to generate antimatter but only in the strongest of particle accelerators and only in microscopic amounts.

If you really want to learn about antimatter I'd read Wikipedia.

http://en.wikipedia.org/wiki/Antimatter

[Streetwind]

NONONONONONONONONONONONONONONONONONONOOOOOOOO!!!!!!

BURN THAT BOOK

Sorry I'm Catholic and all those stupid conspiracy theories make everyone think bad of me and my fellow papist friends.

The book actually addresses this in a fairly self-ironic way. The main villain questions the current state of the church in the public eye and the notion of a moral decline among people due to apathy towards faith and morals. He then poses the question whether or not it could be beneficial for society as a whole if the church could bring itself back into the forefront of people's hearts and minds, even if such a revival would come on the back of a series of high profile murders. The self-irony comes from the fact that while ostensibly it refers to the events in the book, it can just as well be applied to the book itself on a meta-level. What if a book that doesn't necessarily show the church in a completely positive way nevertheless ends up motivating a large number of previously apathetic people to, for the first time in their lives, actually develop an interest in it?

I found that fairly interesting from a philosophic standpoint. More so, surprisingly, than the science fiction aspect, which despite defining part of the book's genre doesn't end up being played to its strengths.

[Kryten]

Also how exactly do you use it to get electricity?

You don't. It's only ever been used for pure research, as production of it is incredibly inefficient, and trapping it even more so; only a few thousand atoms of antimatter have been stored at a time.

[Streetwind]

Well, assuming you had suitable amounts (which for antimatter doesn't have to be large at all), then generating electricity from it would follow along the lines of the usual ways to generate electricity. Antimatter annihilation is merely an energy source - mostly in the form of gamma rays and charged particles, as mentioned before. That energy needs to be converted into electricity, and doing so is a surprisingly mundane process.

You could for example encase the annihilation reaction in a material that's a highly capable gamma ray absorber. The material would heat up from the large energy intake, and then the heat could be transformed into electric energy directly via thermocouples, or indirectly via heating water to drive a steam turbine. After all, steam turbines are how 98% of all powerplants in the world do it today, including all nuclear and even most solar ones.

Another way could be ion beam harvesting. The concentrated gamma rays could ionize suitable gas molecules and these ions, possibly together with the charged particles from the annihilation, could be guided and shaped by magnetic fields to be fed into a device that extracts the electric charge while returning the gas to its neutral state. For example, they are currently looking into this technology for use in fusion reactors, where high numbers of charged particles are produced and the magnetic fields are already present.

[christok]

Antimatter isn't just normal matter with the electric charge reversed. It has the opposite charge in every respect. Except (probably but this is difficult to measure accurately) mass, which is it's own opposite. For example, an antineutron is perfectly well defined (and can be created) although it is electrically neutral. This is because its other quantum numbers (e.g. baryon number) are the opposite of the neutron's.

Antimatter was proposed by Dirac and is best understood in terms of the motivation behind the proposal.

The Dirac equation permits corresponding negative solutions for all positibve energy solutions (E^2 = p^2c^2 + m^2c^4), which would lead the state of any system go deeper and deeper into the negatives, since lower energy states are preferred. Dirac proposed that all of the negative energy states are already filled, by an infinite vacuum sea of particles (e.g. electrons) which exerts no net force on anything because it is uniform. The Pauli exclusion principle prevents "normal" electrons from lowering themselves to the negative-energy states of the vacuum electrons. Whenever one of the particles in the sea was knocked into a positive-energy state, the Pauli exclusion principle would no longer prevent a positive-energy electron from falling into the so created "hole", which would mutually annihilate with the electron when they encounter one another. (The electron lowers itself to the now-available negative energy state by radiating energy. The system is then in the vanilla vacuum state.)

The modern interpretation of this theory is the Feynman-Stuckelberg formulation, which reinterprets the negative-energy holes as positive-energy "antiparticles".

I used some details from D. Grifiths' Introduction to elementary particles, 2nd ed. 2008. Wiley. ISBN 978-3-527-40601-2. p. 21.

Edited July 7, 2014 by christok
Oops, should have been c^4.

[Seret]

You don't. It's only ever been used for pure research, as production of it is incredibly inefficient, and trapping it even more so; only a few thousand atoms of antimatter have been stored at a time.

Having said that, getting electricity from photons isn't difficult. It seems the same principles for working with less frisky photons (eg: photoelectric effect) work with gamma rays. Probably better ways of doing it, but I imagine it's one of those problems that would stress materials people more than physicists.

Edited July 7, 2014 by Seret

[dbmorpher]

Ok I see where you are coming from I just don't like when people write about blowing up the vatican

[theend3r]

Ok I see where you are coming from I just don't like when people write about blowing up the vatican

Yeah, no one should blow up Vatican before they return what they stole from all over the world. I've been to Vatican and they have more egyptian artifacts than in the national museum of Egypt in Cairo. Actually they have so much things there that they can't even display most of them and they rot in warehouses , I saw it all.

Plus the architecture is a sight to behold (although, again, the materials used to build the buildings and monuments, like marble, were taken from demolishing even more ancient buildings, which is quite sad).

Pantheon was still better though.

[Brenok]

Yeah, no one should blow up Vatican before they return what they stole from all over the world. I've been to Vatican and they have more egyptian artifacts than in the national museum of Egypt in Cairo. Actually they have so much things there that they can't even display most of them and they rot in warehouses , I saw it all.

Are you sure you're not talking about the British Museum?

[theend3r]

Are you sure you're not talking about the British Museum?

The second sentence wasn't referring to egyptian artifacts but artifacts as a whole, mostly roman statues/busts.

[lajoswinkler]

Ok I see where you are coming from I just don't like when people write about blowing up the vatican

Defending one's right to believe in something supernatural is one thing, but defending a crooked religious organization that survived on fear? Not a very smart idea.

[theend3r]

Defending one's right to believe in something supernatural is one thing, but defending a crooked religious organization that survived on fear? Not a very smart idea.

Eh, let's not go into that territory as much as I agree with you this will only lead to this thread being closed and damage the great, friendly atmosphere of this forum.

Btw when did they disable html elements in posts? I remember playing around with the <marquee> a bit, then my post got deleted and now I can't even set the size of the font . Bring it back, mods, I promise I won't abuse it anymore.

Edited July 7, 2014 by theend3r

[K^2]

Antimatter isn't just normal matter with the electric charge reversed. It has the opposite charge in every respect. Except (probably but this is difficult to measure accurately) mass, which is it's own opposite.

Rest mass is just the norm of the four-momentum vector. It's not one of the conserved charges, so it doesn't have to have opposite sign. But in a lot of contexts, you can, actually, treat antiparticle's mass as negative, since it only enters relevant equations as m².

It's a little difficult to generalize which quantum numbers do and do not have to be opposite. But any conserved charge absolutely has to be. This is part of how you end up with "negative" energy, for example.

The modern interpretation of this theory is the Feynman-Stuckelberg formulation, which reinterprets the negative-energy holes as positive-energy "antiparticles".

The important part about Feynman's interpretation is that antiparticles are just particles propagating backwards in time. Which is why they have a negative energy component of the four-momentum, but still behave as if they had positive energy and mass.

But all of this is getting rather technical.

[SpaceXray]

One more question: what is the proportion of the annihilation? If it is 1:1, then o way could 0,25 grams of antimatter neutralize something as massive as Vatican+ the ground underneath it+ the surrounding air, making the book/movie very inaccurate.

[K^2]

One more question: what is the proportion of the annihilation? If it is 1:1, then o way could 0,25 grams of antimatter neutralize something as massive as Vatican+ the ground underneath it+ the surrounding air, making the book/movie very inaccurate.

Annihilation is, indeed, 1:1, but you need to keep in mind the amount of energy released. 0.25 grams of antimatter is equivalent to a 10kT explosion. That's a small tactical nuke. About a 2/3 or half of the yield that leveled Hiroshima and Nagasaki respectively. It wouldn't be enough to destroy all of Vatican, but it'd be enough to make it a lifeless ruin.

[phoenix_ca]

Yeah, no one should blow up Vatican before they return what they stole from all over the world. I've been to Vatican and they have more egyptian artifacts than in the national museum of Egypt in Cairo. Actually they have so much things there that they can't even display most of them and they rot in warehouses , I saw it all.

Plus the architecture is a sight to behold (although, again, the materials used to build the buildings and monuments, like marble, were taken from demolishing even more ancient buildings, which is quite sad).

Pantheon was still better though.

I especially loved how they screwed-up St. Peter's Square. The Romans could've done better. You know, by actually making a circle.

Seriously though, that damn place has gold trim floors for goodness' sake. I wouldn't be surprised if the toilets had gold plating.

Also...Dan Brown? I wouldn't say burn the book, as nothing good comes from destroying ideas, but seriously, this guy's ideas are often...very wrong.

[Roastduck]

Annihilation is, indeed, 1:1, but you need to keep in mind the amount of energy released. 0.25 grams of antimatter is equivalent to a 10kT explosion. That's a small tactical nuke. About a 2/3 or half of the yield that leveled Hiroshima and Nagasaki respectively. It wouldn't be enough to destroy all of Vatican, but it'd be enough to make it a lifeless ruin.

what kind of radiation would be left behind, if any? Better wording of the question: what types of energy (is that even a thing?) are released during antimatter annihilation?

[K^2]

what kind of radiation would be left behind, if any? Better wording of the question: what types of energy (is that even a thing?) are released during antimatter annihilation?

Primary is gamma. But you'll get all sorts of secondary simply due to the energies involved. I want to say that it's going to be cleaner than a tactical nuke of the same yield, but I can't guarantee it. Energy released frmo annihilation of a single proton-antiproton pair is sufficient to blast apart any nucleus that gets in the way. Which means you'll get quite a bit of secondary neutron radiation due to atomic nuclei near explosion's enter literally getting evaporated. And neutron radiation is the stuff that's responsible for radioactive fallout.

[Seret]

I remember playing around with the <marquee> a bit, then my post got deleted and now I can't even set the size of the font . Bring it back, mods, I promise I won't abuse it anymore.

Marquee? I would have hit you with a permaban

[dbmorpher]

In defense of nice churches because he says it much better than I could.

[Everten P.]

NONONONONONONONONONONONONONONONONONONOOOOOOOO!!!!!!

BURN THAT BOOK

Sorry I'm Catholic and all those stupid conspiracy theories make everyone think bad of me and my fellow papist friends.

Anyways scientifically antimatter is the opposite, electric charge wise, from normal matter. The thing is antimatter does vaporize when in contact to normal matter. This "vaporization" is actually all of the mass of the two particles (The antiparticle and particle) in energy form. This energy is in the form of gamma radiation, gamma rays are notorious for destroying things but don't "neutralize" that's just bad technobabble.

For your last question, yes it is possible to generate antimatter but only in the strongest of particle acceleKrators and only in microscopic amounts.

If you really want to learn about antimatter I'd read Wikipedia.

http://en.wikipedia.org/wiki/Antimatter

I am Lutheran, I don't think bad of you but if you call the conspiracy theorists stupid I would assume that they would think the same. But, if you are going to be so religious here my only question asks why you are in a place where theoretical stuff is the core, seeds, apple, blossoms, and the whole frickin apple tree (well most of the time).

[SpaceXray]

Thanks for the answers. I only ask none of you start yelling at Brown for his book. Just because he wrote something doesn't mean he is implying that. All of the ideas in the book are just part of the imaginary universe in his book. I don't find the book or movie offensive in any way. I suggest you don't too. Maybe I saw the wrong movie but in my opinion it was done really well. I saw it in Russian and the Italian and Italian accents were very well done. I think a director deserves some credit for getting real Italians or Swiss into the movie.