Talk:Antimatter/Archive 1

Archive 1

Archive 2

Medical Uses

Haven't any of you heard of antimatter therapy (used to combat cancer)? It was a multi-page article in Popular Science. I'm not sure which issue it was, though. -mtmerrick —Preceding unsigned comment added by Mtmerrick (talk • contribs) 01:25, 15 August 2008 (UTC)

Antiuniverse

Is this page really the right place for a description of the Antiuniverse theory? I <3 Wikipedia With the recent reports from ATHENA and ATRAP it is looking less and less likely that an Antiuniverse is plausible. I agree that there should be some mention of it, but I sincerly believe it should have a seperate article and (that article) should be referenced in the 'see also' section.--Lynch82 08:18, 3 March 2006 (UTC)

"probably wrong" isn't good enough reason to get rid of content. The fact that it's considered unlikely is mentioned right in the page. i kan reed 19:04, 2 October 2006 (UTC)

If the antiuniverse theory seems unlikely to ATHENA and ATRAP, then does it seem unlikely to have negative x and y coordinates on a coordinate plane? Only in this case, it would be negative x, y, and z coordinates.—The preceding unsigned comment was added by 67.183.159.89 (talk • contribs) on 04:51, 20 April 2007.

Ok, but should this universe be full of matter, should it not have the opposite in relativity!!! Could the universe that we live in, and is slowly expanding, could it not be expanding into the antiuniverse. It stands to reason that what we know is not the be all and end all of life and the likes. The existance of antimatter has been proven, therefor the universe must have its opposite, wheather it is in this or an alternate one. So I say could the universe that we live in, could it not be expanding into the antiunivers. Thus giving off the gamma rays that flood our scopes and graphs with no answer??? This is but a speculation and a theroy. Pastry!!!! 11.11.06

Am I right in saying that an Anti Universe should exist? I forgot who, but someone stated that everything has an oppisite, and antimatter is matters oppisite, so why shouldn't the universe have one (an oppisite)? It seems possible, but even if there was, we would have to leave it alone, due to the fact that if regular matter (including air) touched it, it would anniohlate. ---- Anonymous

Assuming that there is an Anti-universe and assuming it is similar to our, What would happen if an Anti-Black hole formed and collided with a black hole? Would it result in something similar to a big bang? I mean two incredibly masses of matter and antimatter would result in an incredibly big annihilation. 172.201.118.171 12:37, 31 May 2007 (UTC)

There is no such thing as a anti-black hole. There is no diffrence between a black hole made of regular matter and a black hole made of anti-matter. have a peek on section "Antimatter Black Holes" further down...Dauto 01:58, 6 June 2007 (UTC).

There is a theory that when the Big Bang happened. Matter and antimatter appeared to the universe as ratio like 101:100. So there were little more matter than antimatter and when antimatter and matter annihilated the only thing what was left was the matter: That's because there were more matter than Antimatter. This is only one theory. But in my opinion the theory is wrong. I think that at the Big Bang appeared the same amount of matter and antimatter and there is the same amount of antimatter galaxies as the matter galaxies. And theyy don't get touch with each others because the blast wave of the Big Bang is retaining the galaxies from each other and between the galaxies there is somje black matter and energy. But these are only theories and none of us can be sure. Sorry if my english was too bad. I haven't written about physics very much in english. But hope you did understand :D -Potus55 88.193.42.201 18:59, 12 November 2007 (UTC)

One detail from this section nags at me: the claim that because a matter-antimatter boundary hasn't been detected that there are no antimatter regions in the universe. The problem is that the universe has expanded far beyond the distance that light can travel, so if such boundaries were truly global in scale (for example half of the universe matter and the other half antimatter) we most likely would never see them... right? Wnt (talk) 08:26, 2 January 2008 (UTC)

Just Wondering...

Whilst I understand that, an antiparticle and a Particle will Annilelate in contact, What would happen if an Antimatter Counterpart, of, lets say, Uranium(Antiuranium?), would come in Contact with an atom of Hydrogen?, Would there be Anihilation?, Thank you for you'r time.-Maurizio Dikdan

What would happen is that the electron in the hydrogen atom would annihilate with one of the positrons orbiting the anti-uranium nucleus, and the proton in the hydrogen atom would annihilate with either one of the antiprotons or one of the antineutrons in the anti-uranium nucleus. This would cause a particle shower of the type described above, which would dump enough heat into the anti-uranium nucleus to boil it into its constituent components, resulting in a shower of antineutrons and anti-helium nuclei (antimatter alpha particles).

FUNBold text

Interestingly, the opposite reaction (dropping an antiproton into a uranium atom) has been proposed as one means of initiating fission in a nuclear-pulse-propulsion rocket (a variant of the AIMStar design, if I recall correctly). The idea is that the pulse of high-energy neutrons from one atom's disintegration would cause fissioning in many other nearby uranium atoms, releasing far more energy than the antiproton annihilation alone gave. This in turn would be used to ignite a fusion reaction in a pellet of frozen deuterium, and the resulting plasma fireball would be contained by a magnetic field and directed out the end of the rocket. Nobody's sure if this would work as intended, but it's an approach towards building an interstellar drive that would be far less massive than a Orion-style nuclear drive or a Project Daedalus-style laser-initiated fusion drive, while requiring far less antimatter than a beamed-core antimatter drive. It's described in more detail at antimatter catalyzed nuclear pulse propulsion. --Christopher Thomas 05:11, 28 April 2006 (UTC)

Well mr. iusebigwords, i am entertaining myself whist i wait here in this theoligical complex of literature.

Quantities

    No more than a handful of atoms have ever been made.

Hm. A "handful of atoms" is a lot of atoms. It's also a lot of energy, if we're talking antimatter atoms!

Hey, I'm slow, but I think a handful of blah, means five. I would assume they have made more than five and less than the zillions that make up a hand. So how many (at least an order of magnitude) have they made?

Hey, I'm slow, but I think a handful of blah, means five. That's precisely the problem. In this context the colliqualism doesn't really make sense, so it shouldn't be used. It's like saying that something "sparked a wave of controversy"--sure those are both commonly used colliqualisms, but you still can't spark a wave.

A silly question: Is there a form of "positive electricity" (positricity? Proticity?) ?--68.49.39.32 04:42, 14 Jan 2005 (UTC)

Electricity isn't the result of electrons specifically, its the result of the flow of charge. Protons, electrons, positrons, even charged atoms can create electricity. If you are significantly charged, you would be creating significant electricity simply by moving. Fresheneesz 09:09, 5 April 2006 (UTC)

For the past 40 years, the World has produced about a microgram of antimatter, but in 1999, NASA announced that they successfully made 9 antihydrogon atoms. If we were to build maybe, 1000 AM facilities in the future (possibly on the Moon), we will be able to make a millionth of a gram a YEAR. But, it would would make better sense to use this large amount for research purposes, instead of fuel and weapons, if we were to use it for that purpose it would be a waste of energy, because were using a large amount of energy to make an equal amount of energy equivalent to the antimatter made, so you would be wasting a perfectly large amount of energy.

The exhaunge rate is 500,000 matter subatomic particles to make 1 anti subatomic particle. —This unsigned comment was added by 70.249.162.69 (talk • contribs) on 23:12, 23 March 2006.

Annihilation burst

"Annihilation burst gives electromagnetic radiation" is correct for electron-positron annihilation (at least at low energies). It is incorrect for cases like proton-antiproton annihiliation, where you mainly get pions and some kaons. I put in a more general description. -- Thomas

Backwards in time?

I'm very far from a chemist or physicist or something, but somehow I have doubts about this, "Antiparticles can be considered as normal particles moving backwards in time". I'm assuming it's roughly accepted as truth, seeing as how it's still part of the page... But just double checking. Jimbobbob 02:57, 2004 Oct 27 (UTC)

• Pending confirmation by an expert, I have removed this sentence. I also highly doubt its truth. - Mike Rosoft 11:10, 16 Nov 2004 (UTC)
  • All right, I have re-added it. (It is mentioned in the article on antiparticles.) But I'd still like to see a confirmation from a physicist. - Mike Rosoft 11:55, 16 Nov 2004 (UTC)
    • Yes, this is the standard interpretation of antiparticles in quantum field theory. For example, if we take an interaction between particles and somehow revert the arrow of time, each incoming particle transforms into the outgoing antiparticle, etc. --Itinerant 04:27, 16 Mar 2005 (UTC)
      • This is called the Stückelberg-Feynman interpretation of antimatter, and is essential to how feynman diagrams are drawn. Intangir 00:32, 4 May 2005 (UTC)

Antimatter has nothing to do with time and Feynman diagrams.Is just a solution of Dirac equation of relative electron.The quantum field theory is universal and the arrow of time is described only in thermodynamics.$E=+_{p}2c2+m2c4$ —The preceding unsigned comment was added by 194.63.235.164 (talk • contribs) .

why are u ppl so against traveling back in time? its only possible for small things anyway, not us big things, so no worry of someone killing your parents :) —The preceding unsigned comment was added by Protecter (talk • contribs) .

That's what you say, 194.63.235.164, but I say they're going backwards in time. The "arrow of time" in thermodynamics has nothing to do with this, because when you reverse the flow of time all particles change into their antiparticles but everything still works the same. —Keenan Pepper 12:28, 8 May 2006 (UTC)

What a shame. I used to imagine that if I changed my office to antimatter, it would become more organized automatically ... -- Stiip 00:31, 11 October 2006 (UTC)

Antimatter as fuel

The article says: "... possible to attain antimatter for $25 billion per gram (roughly 1,000 times more costly than current space shuttle propellants)". This has to be checked and clarified. What exactly is meant by "1,000 times more costly"? Surely it doesn't mean that current space shuttle propellants cost $25 billion per kilogram? Are we comparing antimatter vs. space shuttle fuel in terms of cost per unit of produced energy?

I wrote some stuff about production of macroscopic quantities of antimatter in the article about antimatter weapons. Now I think that it probably belongs in the same place as the information about antimatter as fuel from this article. If someone wants to move or edit it, be my guest. --Itinerant 04:27, 16 Mar 2005 (UTC)

Antimatter has nothing to do with time and Feynman diagrams.Is just a solution of Dirac equation of relative electron.

why does anti-matter have to be so annoyingly stubborn? why can't it just be nice to matter? MAKE TEA NOT WAR. Bartimaeus 16:56, 22 November 2006 (UTC)

Because it's ANTI-matter, silly. Anti means opposite. So it's obviously not going to get along with matter. --Das654 07:27, 6 May 2007 (UTC)

Efficiency

The "Antimatter as fuel" section states: 'Counterbalancing this, when antimatter annihilates with ordinary matter, energy equal to twice the mass of the antimatter is liberated—so energy storage in the form of antimatter could (in theory) be 100% efficient.'

I don't know enough physics to be sure, but I read (on Antimatter weapon and somewhere else I don't recall) that about 60% of the energy is released as neutrinos. Since those almost don't interact with matter, I don't see how the efficiency could be 100%.

It's been proven by scientists at C.E.R.N, http://livefromcern.web.cern.ch/livefromcern/antimatter --Dansanman 06:33, 3 February 2006 (UTC)}

Your link does not appear to contain information about the question of annihilation products. My understanding of what actually happens is that proton/antiproton annihilation (the reaction producing most of the energy in an antimatter drive or bomb) produces one quark/antiquark annihilation, expelling the remaining quarks bound as pions. The initial annihilation produces gamma rays, mostly (as it would be a quark annihilating with its antimatter counterpart, just as with the decay of a $\pi ^{0}$ meson). The expelled pions are either two $\pi ^{0}$ mesons, which almost immediately decay into gamma rays, or a $\pi ^{+}$ and $\pi ^{-}$ meson, which decay into antimuons or muons (respectively) after a few metres of travel, which in turn decay after travelling hundreds of metres. During this time, $\pi ^{+}$, $\pi ^{-}$, $\mu ^{-}$, and $\mu ^{+}$ can be deflected to provide thrust for a space drive, or can interact with electrons and nuclei in matter to provide heat for power or a different type of space drive. The main mode of energy loss if I understand correctly is with gamma ray emission during the first annihilation and for $\pi ^{0}$ annihilations (as the gamma rays carry away most of their energy or dump it as difficult-to-use heat in reactor shielding). Neutrinos carry away some of the energy when charged pions decay into muons, but quite a bit of it stays with the muons. I don't have exact efficiency numbers, but an upper limit for a space drive would be about 450 MeV of kinetic energy in two charged pions of mass 135 MeV/C^2, from a proton/antiproton pair with a mass of about 1880 MeV/C^2, for an efficiency of around 50%. Actual efficiency will be less due to neutral pion production. Efficiency of a power plant would be much less, because your final stage is a heat engine with a maximum efficiency of around 30%-50%. --Christopher Thomas 03:08, 13 February 2006 (UTC)

I'm not suggesting a violation of conservation of energy, but wouldn't it be 200%? 100% being the conversion of 1 partial into energy, but both particles are converted. (Note: Not counting neutrinos/Actual efficiency)--Zerothis (talk) 23:49, 28 August 2008 (UTC)

The Article is right about the fuel energy (i think)

The article said: "The reaction of 1 kg of antimatter with 1 kg of matter would produce 1.8×10²¹ J of energy (by the equation E=mc²)." Based on my calculations, 1 kg × (300000 km/s)² = 1.8×10¹⁷ J. Several other websites also say 10¹⁷, no one said 10²¹. - Wilfried Klaebe, 2004-12-24 14:50 +0100

The last person that posted saying that the quantity of energy is wrong, if he used the equation he described, he commited several mistakes. First, it's 2kg of matter being turned into energy, and second , if you analyze the units, he should have transformed the speed of light into meters por second and not leave it in kilometers (remember a joule equals kilogram times meter square over second square), that is why he is getting a different result.

1.8*10¹⁷ is indeed the correct amount. Speed of light is 300000 km/s = 3*10⁸ m/s, 2mc^2 = 2*9*10¹⁶ J = 1.8*10¹⁷ J. --Itinerant 04:27, 16 Mar 2005 (UTC)

No,1 kg corresponds to 25,000,000,000 kWh of energy, here, http://livefromcern.web.cern.ch/livefromcern/antimatter/academy/AM-travel01.html --Dansanman 06:38, 3 February 2006 (UTC)}

1 kilowatt-hour = (1000 J/s)(60*60 s) = 3,600,000 J. Different units; both calculations are correct. CERN did the calculation for 1kg of matter, but we're interested in 1kg antimatter annihilating with 1kg matter, so we used 2kg. - mako 22:31, 3 February 2006 (UTC)

Gravitational Repulsion of Antimatter?

I have often wondered why we so quickly assume that the weight (not mass) of anti-matter is positive. If a hole in a silicon lattice is a good analogy of a positron in free space, then it is natural to think that positrons are repulsed by the gravitational force of a normal matter, since holes are. This could also help explain other problems. First, where is all the anti-matter? Perhaps in super-clusters of galaxy clusters. Why is the expansion of the universe accelerating? Imagine only two stars exist, one normal and one anti matter. They not only repel each other, they accelerate as they separate. The same may be true for large groups of super galaxy clusters mixed with anti super galaxy clusters. How do we know the weight of anti-matter? - Bill Cox; Feb 4, 2005; bill@viasic.com

• If antimatter had negative mass, it would have negative mass-energy (e=mc^2) and so a particle-antiparticle collision would result in the two disappearing, and the leftover kinetic energy being used to create products. However, the observed enery totals after annihiations have far higher mass-energy than could be accounted for if only the kinetic energy was left to create products. -9/4/2005 smangham@hotmail.com: Badly expressed my objection origonally, reworded it to make more sense

• • Actually, the full equation is more like e^2=m^2c^4+p^2c^2, where p is momentum. Assuming no momentum gives us e^2=m^2c^4 . It doesn't seem obvious from there that it should have negative energy. Intangir 00:47, 4 May 2005 (UTC)

• For the moment, the discussion about the possible gravitational repulsion of antimatter is on the negative mass page. Intangir 00:38, 4 May 2005 (UTC)

Do black holes not give off gamma radiation?????? So does it not stand to reason that this could be the universes natural antimatter lab?????? This therefor could explain the absense of antimatter in our known universe. The gravitational pull of a said black hole draws even the smallest particals and the fastest into its centre. Could it be that the centre is just a compounded sphere of antimatter rotating at such a high speed that none are relesed and the matter that is drawn in is crushed and colide with the antimatter giving off gamma radiation in the process. One chefs view. Pastry 11.11.06

Quantities needed?

Scientists in 1995 succeeded in producing anti-atoms of hydrogen, and also anti-deuteron nuclei, made out of an antiproton and an antineutron, but not yet more complex antimatter. In principle, sufficiently large quantities of antimatter could produce anti-nuclei of other elements, which would have exactly the same properties as their positive-matter counterparts. However, such a "periodic table of anti-elements" is thought to be, at best, highly unlikely, as the quantities of antimatter required would be, quite literally, astronomical.

I'm far from knowledgable about antimatter, but why would it take "astronomical quantities" of antimatter to produce a more complex element than hydrogen? For a single atom of anti-helium, you'd need two positrons, two anti-protons, and two neutrons, no? jdb ❋ (talk) 06:03, 26 Feb 2005 (UTC)

Probably the chance that the reaction work occur...Joe Normal

I'm surprised they produced antideuterium at all. Protons can be produced at high energy and slowed down, but neutrons can't be trapped, so you'd have to either try to produce a bound antineutron/antiproton pair out of thin air (good luck), or try to get antiproton/antiproton fusion happening (could be done, but would take a very long time, due to the small interaction cross-section; this is why fusion of light hydrogen for power isn't feasible). Making anything heavier would involve producing large quantities of antideuterium and fusing that, which would be horrifically expensive and time-consuming. --Christopher Thomas 03:13, 13 February 2006 (UTC)

odd wording

I just removed a rather odd sentence in the body of the article: "Just imagine if humanity used it as a weapon" since it dosent seem to fit in with a factual article 61.68.242.104 06:05, 24 Mar 2005 (UTC)

Unfair comparison

The reaction of 1 kg of antimatter with 1 kg of matter would produce 1.8×1017 J of energy (by the equation E=mc²). In contrast, burning a kilogram of gasoline produces 4.2×107 J, and nuclear fusion of a kilogram of hydrogen would produce 2.6×1015 J.

Surely that's comparing 2kg of antimatter/matter fuel with 1kg of other types of fuel. That seems a little unfair.--Malcohol 12:37, 31 August 2005 (UTC)

Well, in the case of the gasoline there's also a substantial quantity of oxygen involved in the combustion (dunno exactly how much, I haven't done any chem in over a decade) not accounted for in that comparison either. It's an illustrative comparison. Look at the orders of magnitude involved; the factor of 2 in the mass is dwarfed by the factor of about 70 between the energy in the fusion and matter/antimatter reactions.--Robert Merkel 14:17, 31 August 2005 (UTC)

Robert's right about the gasoline, just doing a quick calculation using octane- C8H18 (nothing to do with the octane rating) nearly 4 kg of oxygen is needed to combust 1 kg of octane. I may be wrong so here is the equation I used- C8H18 + 12.5 O2 = 8 CO2 + 9 H2O Afn 16:31, 1 September 2005 (UTC)

These are interesting observations. Perhaps it would be useful if, somewhere on the wiki, there was a table of 1k-of-total-mass-of-certain-materials produces this-many-joules. This is just a thought, as I don't have the know-how myself. --Malcohol 08:55, 7 September 2005 (UTC)

Antideuterium / Antimatter production

Scientists in 1995 succeeded in producing antiatoms of hydrogen, and also antideuteron nuclei, made out of an 
antiproton and an antineutron, but no antiatom more complex than _antideuterium_ has been created yet.

Is this statement a little bit wrong? Because the Antideuteron article clearly states that no antiatom even _as_ complex as antideuterium has been created to this day.

Antideuteron has been created, therefore the statement is correct.

Yes, but not antideuterium. Read the whole sentence before you answer will you?

What does antimatter look like?

I've always wondered, if you had enough antimatter to be visible with the naked eye, what would it look like? Would it look any different from normal matter, or would it be visible at all? — JIP | Talk 05:14, 19 September 2005 (UTC)

It should look just like normal matter, as the energy levels for positron orbitals would be the same. It should also act the same chemically (with itself, that is).--Christopher Thomas 03:15, 13 February 2006 (UTC)

Ok call me stupid but i was thinking that if antimatter is onthe opposite of matter, as in rotation and i think gravitation, or could it be magnatism. Could it not be that antimatter and dark matter or dark energy is of the same idea. Both are unknown and both have some very similar qualities that lead me to think that they could be one in the same. Just a thought. Try me here!!!!!!!! Pastry 11.11.06

Can you be certain that antimatter can be seen if you were able to produce enough of it??? Would light be absorbed or would other particals be attracted to it??

As far as I know, photons (which light is made out of) are much more elementary particles than protons, neutrons, or even electrons. As far as I know, there are no "anti-photons". Therefore I think photons should react with antimatter exactly the same way as with matter. JIP | Talk 18:02, 4 October 2007 (UTC)

Who is this Mr. Beutel?

... "Mr. Beutel's class info here", eh? Someone got it before I had a chance to, anyway..

Template:Antimatter

I found this template and it looks to me it's not used anywhere? Would it be appropriate to add it on this page? Skydiver 17:09, 7 December 2005 (UTC)

I've added the template since no-one objected. Skydiver 09:47, 9 December 2005 (UTC)

I am adding it to any articles linked to the template. Chad 08:16, 6 February 2006 (UTC)

Inconsistency of Price

Uh, yeah...on this page, it lists antimatter as costing $25 million per gram, but the page for antimatter weapons appears to list it as $25 billion. I don't know which is correct, but someone who knows should do something about it. Nick 02:33, 19 December 2005 (UTC)

I'd go with the $25 billion per gram value. A back of the envelope estimate can be obtained by assuming $0.05 per kWh (3.6 MJ), C^2 J/kg, and an efficiency of at best 1 part in 10^4 (for a facility optimized for antiproton bulk production; current facilities are about 1 part in 10^-6). This gives about $1.2 billion per gram at 1 part in 10^4 efficiency (not currently obtained). Positrons are much easier to produce, but aren't very useful (you can't make neutral antimatter atoms to trap and store without antiprotons). --Christopher Thomas 07:54, 12 February 2006 (UTC)

Uh.. you can't "trap and store" neutral atoms anyway. Why would you want antimatter atoms? Fresheneesz 03:40, 6 April 2006 (UTC)

Sure you can. This is done all the time for producing Bose-Einstein condensates. You cool them and use photon pressure and a strong magnetic field. As for _why_ you'd want to do it, most thought-experiments along these lines that involve large amounts of antimatter have been for the construction of an interstellar probe powered by antimatter-catalyzed fission or fusion. On a laboratory scale, you'd do it so that you could probe antihydrogen's properties in detail to see if it matches predictions. The missing link for lab-scale experiments is a means of cooling antihydrogen from temperatures on the order of eV (what you get in the "cooled" antiproton traps) to temperatures on the order of micro-eV or lower (what you need for laser cooling and long-term neutral atom confinement). --Christopher Thomas 04:19, 6 April 2006 (UTC)

Also check out the ATHENA experiment for 'why'. - mako 08:28, 6 April 2006 (UTC)

Hmm, allright, my mistake. But how does a large magnetic field help confine a neutral body? Fresheneesz 08:43, 7 April 2006 (UTC)

Many atoms, including hydrogen, have a substantial magnetic moment, and so are influenced by magnetic fields. --Christopher Thomas 15:58, 7 April 2006 (UTC)

Gravitational interaction of antimatter

I added a see also link to the fringe science article on the Gravitational interaction of antimatter. -- Intangir 05:08, 21 December 2005 (UTC)

"Interrogation"?

"(...)confine the antiatoms in an inhomogenous magnetic field (...) and interrogate them with lasers."

This seems to be a usage of "interrogate" with which I am not familiar. Can someone expand on this? DS 13:47, 17 January 2006 (UTC)

Yes, it means to investigate or probe them, as you can understand through context. I'm convinced that this is proper use of the word. FFLaguna

Bulk production of antimatter

The article states that "There is, however, no known practical or theoretical method by which antielements could ever be produced in bulk quantities.". While I don't know of any method of production that would be _practical_, you could in principle produce large amounts of antimatter by dumping matter into a small black hole and separating particles and antiparticles out of the polar jets using a magnetic field (charge-to-mass ratio has the opposite sign for particles and their antimatter counterparts). Good luck finding paper references for using that as an industrial process, though. --Christopher Thomas 05:55, 15 February 2006 (UTC)

Gravitaional forces???? Ouch it hurts, sorry. Would you not be drawn in and crushed also. This is not a fesable idea! Pastry 11.11.06

If someone invented a very practical means of bulk production of antimatter, they should be ethically bound to cover up the invention. Given humanity's track record for violence, this technology would make nuclear weapons proliferation look like child's play. Publication of such a technology would be the death sentence for humanity. Dalebert 9/6/07 —Preceding unsigned comment added by 192.158.61.142 (talk) 20:11, 6 September 2007 (UTC)

Negative Mass?

The positron emission article says that "a proton is converted to a neutron...and a beta plus particle (a positron)...are emitted." A neutron has more mass than a proton, so this logically means a positron has negative mass. So if a large quantity of antimatter were placed on Earth, it would it move up because of "antigravity"?

Positron emission can't happen without an external source of energy, which is converted into the positive mass of the positron. See Gravitational interaction of antimatter. —Keenan Pepper 03:20, 15 March 2006 (UTC)

Geometric?

"Antimatter production is currently very limited, but has been growing at a nearly geometric rate since the discovery of the first antiproton in 1955."

I'm just curious as to what a "geometric" increase actually means? It increases by circles and squares?

Circles, no; squares, sorta. It's probably alluding to the geometric progression. - mako 08:37, 10 April 2006 (UTC)

The area of a circle is proportional to the radius squared too. —Keenan Pepper 12:01, 10 April 2006 (UTC)

lol -NOOBLET

Why collision into energy?

Why do a particle and its anti-particle convert into energy upon collision? What is the mechanism for this interaction, and should it be included in this article? FFLaguna

"Convert into energy" is a poor description, as "energy" is a bookkeeping number, not a tangible "thing". When a particle and antiparticle (or indeed, any other two particles) interact, the result of the interaction can be any other configuration of particles with the same energy, momentum, and other conserved values ("quantum numbers") that the original system had.

For ordinary, stable particles like protons or electrons bumping into each other at low energies, what you normally get out is the same particles that came in, with an exchange of energy and momentum, because these are the only allowed states within the energy limits. In high-energy collisions, you can get more exotic particles created, or particle/antiparticle pairs, as long as the total system energy (including rest energy of the new particles) remains the same, and all other values are conserved.

A particle/antiparticle collision is special, because all of the conserved values (quantum numbers) besides energy and momentum cancel out. That's actually one way of describing what antimatter is (matter with reversed charge, parity, baryon/lepton number, strangeness, etc). Because these values sum to zero, the outcome can be any other particle/antiparticle pair, or a pair of photons, or a combination of the above, or odder variations. What usually happens is that you get a shower of light-weight particles (like electron/positron pairs and mesons) and high-energy gamma rays resulting. Not all of the energy has to go into the rest mass of particles, so when particles are created, they'll typically have quite a bit of kinetic energy as well, representing the difference between the rest mass of the products and the original particle/antiparticle pair's energy.

For specific examples, a low-energy interaction between an electron and positron (mass of about 500 keV) will give you two 500 keV gamma rays going in opposite directions, and the annihilation of a proton and antiproton will generally give you gamma rays in the hundreds-of-keV range and pi mesons, though other combinations are possible (you can think of this one as resulting from one quark from the proton and one antiquark from the antiproton annihilating, but that's not strictly correct). High-energy collisions typically produce "jets" of particles, which represent heavy, unstable particles that are created and then immediately decay into showers of secondary products going in the directions of the originally-created particles. As long as the kinetic energy supplied is large, the interacting particles can be just about anything (not necessarily particle/antiparticle pairs, though they're often used).

The "particle/antiparticles annihilate to produce energy" line, as far as I can tell, comes from a bad habit popular literature has of confusing light with energy. It _has_ energy, but the light is composed of particles (photons).

I hope this answer is useful to you. --Christopher Thomas 03:37, 24 April 2006 (UTC)

And much later, I realize that should have read "hundreds of MeV" instead of "hundreds of keV" for proton/antiproton annihilation. --Christopher Thomas 01:20, 25 May 2006 (UTC)

Yeah, that answered my question! A little belated of a response on my part, but I was very pleased to read that. I now have a final question that likely has no follow-up questions. I've been looking all over, and cannot find an answer to this: What determines what the outcome will be in a high-energy interaction, such as matter/antimatter annihilation? With a high enough energy that has several possible outcomes, how does one get chosen over the others? Is it random? Is there a statistic probability? If the Heisenberg Uncertainty Principle did not exist, would the process be predictable, or is this part of the question pointless to ask? I think that should do it.

Anybody is welcome to answer, by all means. :) FFLaguna 08:04, 13 November 2007 (UTC)

question

ppl, are antimatter just matter traveling backwards in time? so ive heard... lol like in this diagram

|     |                                           
|W-   |
|\    |
| \-ne|
| |\\ |<----------thats an arrow there 
|   \ |W+ from now on                              
|    \|
|     |
|e-   |e+
|     |

time go up (i cant draw the arrow it screws up)

i cant make it look good uve have to do ur best

actually its best for u not to look at the diagram

cant u say a ne (ele neutrino) was emitted by e- then go backwards in time and getting eaten by W+ then it changes to e+?

btw i think this interaction is impossible im just giving an example forgot other 1s —The preceding unsigned comment was added by Protecter (talk • contribs) on 14:23, 1 May 2006.

Our current understanding is that the laws of the universe obey CPT symmetry, which means that if you looked at the universe with time reversed, matter would look like antimatter (reversed charge and parity). From this point of view, you could argue that in some sense antimatter seems to be matter moving backwards in time, but in practice you can't explain all antimatter-related interactions that way. For example, beta decay and inverse beta decay causes production and consumption of an electron without a positron being involved, and positron emission likewise produces a positron without an electron emitted at the same time. --Christopher Thomas 21:47, 2 May 2006 (UTC)

Added a few things

I've found that several online role-playing communities have used anti-matter in the past. It's not massively common, but it's apparently done enough for some of them to have conversations about it. So, I did a little research, and found two message boards that have entries into wikipedia, and have used anti-matter in the past, with some sort of explaination.

~ Rhysis 08:53, 31 May 2006 (UTC)

You do realize that "negatron" means "electron", not "antiproton" as you've assumed in your edits, right? --Christopher Thomas 13:33, 31 May 2006 (UTC)

These edits are factually incorrect. Now reverted. -- Xerxes 14:44, 31 May 2006 (UTC)

Neutrinos and black hole reference

I have two concerns regarding this edit, which was otherwise good:

• Neutrinos have nonzero spin. This would prevent them from being their own antiparticles in the conventional sense, though I understand that neutrinos and antineutrinos are considered different manifestations of one particle in some Grand Unified Theory candidates, making this statement not completely incorrect (just misleading).
• I dispute the removal of the black hole reference, as near a black hole's event horizon is one of three places you'll find temperatures sufficient for pair production (the other two being the primordial universe, and the shock front where a relativistic jet encounters the interstellar medium). How is this not relevant in a paragraph about pair production in very hot environments?

--Christopher Thomas 20:12, 12 June 2006 (UTC)

The neutrino may be its own antiparticle if it has a Majorana-type mass (as opposed to a standard Dirac-type mass). There are searches currently underway to detect neutrinoless double beta decay, which can only occur if this is the case.

Black hole jets are certainly one place to find antimatter. This is not what was said in the article, which went on about black hole horizons and Hawking radiation. While Hawking radiation certainly might include antimatter, antimatter is not particularly important to the effect, which merely includes all possible particles. Further, there is no observation of Hawking radiation, much less antimatter in any such radiation. I would certainly support the addition of a sentence about antimatter from black hole jets, or particularly something about the positronic "fountain" of the Milky Way. -- Xerxes 20:35, 12 June 2006 (UTC)

I already referred to the Majorana mass interpretation of the neutrino. I think that this is sufficiently removed from conventional (Dirac) notions of "particle" and "antiparticle" that it should be flagged as such.

Regarding black holes, in my previous response, I list "near an event horizon" and "relativistic jet" separately for a reason, as these are completely different phenomena. If the horizon is described in terms of the Unruh effect, pair production in a high temperature environment is the _mechanism_ by which antimatter is produced, making it an extremely relevant part of any description of Hawking radiation that takes this form. If you're claiming that Hawking radiation shouldn't be an example because it hasn't been observed, that's one thing, but claiming that pair production isn't a significant part of a description of Hawking radiation if it _does_ exist is quite another. Which argument are you using for the removal? --Christopher Thomas 21:46, 12 June 2006 (UTC)

Both. If Hawking radiation exists (which has not been shown) and if microscopic black holes exist (which observational evidence is against), then antimatter makes up less than half the resulting radiation. Given the number of caveats necessary to link this to antimatter, I just don't see how it's relevant enough to include when so many other real-life antimatter sources are being left out. -- Xerxes 03:12, 13 June 2006 (UTC)

Comment mistakenly added to article

I also read something alluding to the fact that is very very hard to countain a large quantity of antimatter due to the repulsion between antiparticles (if someone could expend on this). In other words antimatter fuel belongs to science fiction. —The preceding unsigned comment was added by 70.81.162.66 (talk • contribs) .

Antiprotons repel each other, just like protons, but neutral atoms of antimatter attract each other, just like atoms of matter. —Keenan Pepper 21:41, 2 August 2006 (UTC)

Nonsense

I removed this comment from the medical uses section: "Also, cultured hamster tissues have been tested with antimatter to determine whether or not antimatter is effective at killing sausage." Some people have a weird sense of humour... --Cfslattery1 23:35 (GMT), 22 August, 2006

Yeah, that's not even WP:BJAODN-worthy. —Keenan Pepper 01:42, 23 August 2006 (UTC)

That was the result of a botched revert. The original text read "...at killing cancer cells". I rolled back further to repair this and other damage. I can see enough arguments for using a positron or antiproton source for radiation treatment to believe someone's tried it, though a citation would be nice. --Christopher Thomas 03:15, 23 August 2006 (UTC)

Oh. That makes much more sense. =P —Keenan Pepper 03:26, 23 August 2006 (UTC)

Question!

Ok, the "antimatter universe" section answered one question, but created a couple more. My original question was going to be "can antiparticles join together as sub units to create antiatoms and then to molecules." Well, obviously, if there were enough, then yes, due to the theory of antigalaxies and such. However, what about the little known dark matter. I'm not entirely sure what it is but seeing as how is seems to be classified as matter, and seems to be causing the universe to accelerate(or at least that is one theory as to why we are not deccelerating) that it must be numerous. Well, first question that comes to mind: "Is there anti-dark matter?" second question: "what if the normal dark matter comes into contact with what would have to be the anti-dark matter around an "anti-matter galaxy?" I know, this is all extraneous speculation, but, if you have an answer(or even, any idea) then please respond. —The preceding unsigned comment was added by Ahnung (talk • contribs) .

Dark energy makes the universe expand, not dark matter. Dark matter has normal gravity, so it tends to pull things together. Dark energy has some weird negative gravity that pushes things apart. Also, there's no reason to assume dark matter even has antiparticles, and even if it does, there's no reason they would interact with matter any differently. So basically, no one knows. —Keenan Pepper 14:09, 11 September 2006 (UTC)

Has anyone ever noticed that when scientists can't explain something, they come up with a new "dark" thing that we can't detect so no one can prove them wrong? Conveniet eh?Skeletor 0 (talk) 17:39, 17 April 2008 (UTC)

Antimatter Black Holes?

Forgive me if I'm unable to articulate this adequately but I was wondering... If matter in the Universe obtains sufficient mass you can get a black hole (I know that's rather a simplistic explanation) but what about Antimatter? Does the same apply or would different rules produce an altogether different effect? RawPhoenix 00:01, 23 September 2006 (UTC)

You can't tell the difference between a black hole made of matter, a black hole made of antimatter, and a black hole made of pure energy. The no hair theorem says black holes only have three properties: mass, angular momentum, and electric charge. Baryon number isn't one of those. —Keenan Pepper 00:45, 23 September 2006 (UTC)

Black holes, White holes and outer-universe

What is the affect of matter and antimatter on the above headline?? Should either, all or just one be made of or start from antimatter?? I have no history in there areas but do have some extensive self knolage of this. Please excuss the typing. If you have any input on this i would be very interested. Thank you, and keep it simple thank you. Pastry 11.11.06

A black hole made of antimatter would act exactly the same as a black hole made of normal matter. The no hair theorem says only mass, angular momentum, and electric charge make a difference. Baryon number is not one of those, so black holes with positive baryon number (normal matter), negative baryon number (antimatter), and zero baryon number (pure energy) would act exactly the same. White holes probably don't exist, but if they did, the situtation would probably be the same as for black holes. —Keenan Pepper 21:11, 11 November 2006 (UTC)

Thank you Keenan! Pastry 17.11.06

As the universe that we live in is made of matter, could the outer of our universe be antimatter?? or is it that the centre of our universe be made of antimatter and the matter that is attracted causes the expantion of ours to what it is now?? Pastry 17.11.06

Production

A couple of production statistics for Fermilab, if someone wants to work them into the article. [1] gives a total storage record of 246 x 10^10 antiprotons, and a current production rate of 20x10^10 per hour. (The total energy the storage record represents, incidentally, appears to be "enough energy to boil a cold Batavia raindrop". [2]) Shimgray | talk | 23:38, 10 December 2006 (UTC)

Does Antimatter give off a gravitational force?

Ok. I know that according to Newton's Universal Law of Gravitation that all matter gives off a gravitational field. But if the antimatter universes exsist, would they have a gravitational force, or maybe, would they repel gravity? —The preceding unsigned comment was added by Realtexan (talk • contribs) 20:14, 21 December 2006 (UTC).

Negative atomic number

All antielements have negative atomic numbers because they have negatively charged protons. Cosmium 23:20, 24 February 2007 (UTC)

It is likely that the mass number would be a positive value due to the positive mass that an antiparticle has (See my discussion in Gravitational interaction of antimatter). However, the element itself would likely be marked with a bar above the symbol, also known as a macron. For example, antioxygen would be denoted as Ō rather than O -- Xander T. 04:46, 18 March 2007 (UTC)

Positive mass number

Antielements have positive mass numbers like ordinary elements because they have positive mass, unless if it has negative mass. Cosmium 23:20, 24 February 2007 (UTC)

CERN/Dan Brown FAQ

I mistakenly put in a somewhat snide comment about the FAQ link from CERN. Had I scrolled down, I would have seen that there is actually quite a bit of useful antimatter-related information mixed in there. On the other hand, the page as a whole seems to be aimed more at CERN-related BS in Dan Brown's Angels and Demons in general. This is why I find the original (and reverted) label somewhat misleading. I'm not going to try boldly to change it this time, having already screwed this one up once, but some mention that the page is a specific response to A&D, or at least that the good stuff is further down amidst the other A&D-related stuff like "we don't generally wear lab coats and run around carrying files", and "Tim B-L didn't invent the whole internet", would be good. —The preceding unsigned comment was added by 63.86.210.252 (talk) 16:43, 16 April 2007 (UTC).

Done. --Christopher Thomas 20:20, 16 April 2007 (UTC)

Looks good, thanks -63.86.210.252 21:25, 16 April 2007 (UTC)

Maybe weve got it all wrong

Is it possible that our universe is actually antimatter, and what we think of as antimatter is actually normal matter? Diabl0658 20:24, 25 April 2007 (UTC)

Since there is a symmetry between matter and antimatter, your question doesn`t make sense. We chose to call, by definition, the one that`s common around us "matter', and the other one (less common) "antimatter". You could call them the other way around, but wouldn`t change a thing. You could even deceide to call electrons antimatter and positrons matter, while, at the same time, still keep calling protons matter and antiprotons antimatter (That way having our universe being made partially of matter and partially of antimatter). There would be nothing wrong with it. It would simply be weird. Dauto 05:25, 26 April 2007 (UTC).

Does anti-matter even EXIST though? There's no proof. When matter and anti-matter come into collision, there's a huge energy release, which means big BADA-BOOM! Therefore, anti-matter cannot stay in the world for long. So, no proof. QED. --Das654 07:29, 6 May 2007 (UTC)

Das654, Antimatter has been directly observed in laboratories for more then 70 years now. Your pseudo-proof amounts to nothing more then a complete missunderstanding of what a scientific proof is supposed to look like. You really need to do some reading about the subject. 201.9.25.128 16:44, 6 May 2007 (UTC).

I didn`t realise I wasn`t logged in when I signed the comment aboveDauto 16:47, 6 May 2007 (UTC).

It's an interesting philosophical question, similar to asking: what if the northern hemisphere is really meant to be the southern hemisphere and vice-versa? What if we are looking at everything upside-down, and all our maps are wrong? Essentially it doesn't affect the outcome of any scientific conclusions, so really whichever way you look at it doesn't matter. And yes, I do realise the irony of saying it doesn't matter. Glooper 07:14, 8 July 2007 (UTC)

Futurama

I removed a reference in the Popular Culture section to the main character's ship being powered by antimatter, as the Planet Express Ship is actually powered by Dark Matter -Jcwilder 20:51, 9 May 2007 (UTC)

Cost clarifaction

I removed a 'clarification' that several hundred Swiss francs is actually quite costly. It seems unnecessary and doesn't fit with the tone of the article - cannywizard (talk) 23:28, 27 December 2007 (UTC).

Article heading.

Hello. This is my first time actually making a change to something on Wikipedia, so I decided it would be best to start in a talk page. Is there any particular reason why the article starts by saying: "For any of you out there about to read this stop and think about whether or not you really care. Trust me this will make you brain hurt for hours. Just try to stay sane." It made me laugh a bit, sure, and I do appreciate the humor behind it. But is it really needed? Cheers. —Preceding unsigned comment added by 68.203.75.7 (talk) 06:23, 18 January 2008 (UTC)

"Vandalism" is fairly common on Wikipedia, though I really haven't seen it very often when actually looking up an article. If you're interested you can look up WP:VAND, WP:WikiProject Vandalism studies etc. As a newbie you'll usually find that by the time you're ready to fix a case of vandalism someone's already done it. 70.15.116.59 (talk) 19:27, 24 January 2008 (UTC)

Antiuniverse error

ESA’s gamma-ray satellite named Integral detected a lopsided shaped antimatter cloud in the Milky Way galaxy. The 511 Kev energy of the gamma-ray is a signature of positron-electron annihilation. Georg Weidenspointner at the Max Planck Institute for Extraterrestrial Physics and an international team of astronomers made the discovery using four-years-worth of data from Integral.

Dsmith7707 (talk) 16:14, 21 January 2008 (UTC)

I've expounded on that a bit more under "naturally occurring sources". As I understand the usage this is hardly an "antiuniverse" - it's merely a diffuse cloud of positrons floating around in space, not a central zone of the galaxy with planets made out of antimatter. 70.15.116.59 (talk) 19:22, 24 January 2008 (UTC)

A question

Semantics aside, antimatter travels back in time, right? So couldn't the question "where's all the anti-matter" be answered, "on the other side of the big bang, going backwards through time?" If our direction in time has a "bias" towards matter, the other direction would have the bias towards anti-matter. What are the problems with my model? File:The other side of the big bang.jpg

While that would explain antimatter-matter asymmetry, there isn't any experiment that I know of that can prove, or has proven the time direction of particles. Due to the boundary limitations of time direction, I don't even know if such a thing is hypothetically even possible. That postulate may be similar to the unprovability of the Many Worlds Theory, which would require us to be able to escape our reality and return to a pre-existing one in order to prove that parallel universes do exist.--Sparkygravity (talk) 10:55, 21 March 2008 (UTC)

By considering the propagation of the negative energy modes of the electron field backward in time, Richard Feynman reached a pictorial understanding of the fact that the particle and antiparticle have equal mass m and spin J but opposite charges q. This allowed him to rewrite perturbation theory precisely in the form of diagrams, called Feynman diagrams, of particles propagating back and forth in time. This picture was independently developed by Ernst Stueckelberg, and has been called the Feynman-Stueckelberg interpretation of antiparticles. This technique now is the most widespread method of computing amplitudes in quantum field theory. According to Einstein's theory of special relativity, any travel that is faster-than-light will be seen as traveling backwards in time in some other, equally valid, frames of reference. The answer to the question "Where is all the anti-matter?" appears to be "In the future." --RagnarCeline (talk) 22:34, 23 March 2008 (UTC)

I don't know if I would make that leap, since what the computation of amplitudes relies on is a frame work of dimensions, so there isn't an expertment that can confirm that it's in the future, or going backwards in time, or whether or not it's in a state of continual quantum tunneling or whether it has slipped dimensions according to M-theory... the Many Worlds theory. For quantifying quantum fields it works, definitely but scientists can't confirm where it goes, or where it is.--Sparkygravity (talk) 12:08, 25 March 2008 (UTC)

I don't think there should be much mention of this in the article. Even if its true (which is looking unlikly) we can't confirm it and I think it would be a very confusing point to bring up in a wiki article. All that aside, it is very unlikly that there was any antimatter present in the big bang. If there had been it would have reacted before forming a singlarity with normal matter.Skeletor 0 (talk) 17:31, 17 April 2008 (UTC)

Antimatter links

I'm busy but it just so happens that the work I'm currently doing on Kardashev scale coincides with Antimatter. So I'll let anyone interested on expanding the article look at these links

• http://deepblue.lib.umich.edu/bitstream/2027.42/42928/1/10751_2006_Article_BF02316703.pdf - Important conclusion the universe may be charged having large areas of antimatter. There may be as much antimatter in the universe as matter.
• http://arxiv.org/abs/hep-ph/0106030v1 - same guy, same conclusion
• http://www.physorg.com/news122294882.html - Talks about the Bs Meson switching
• http://www.physorg.com/news78410254.html - Normal Barons have the potential to switch, meaning that matter becomes antimatter for a short period of time during Bs Meson decay.
• http://www.physorg.com/news111861487.html - The European Space Administration finds large antimatter cloud near galactic center.

• Schultz, James (2001-01-11). "Antimatter Makers Chase Ultimate Energy Source" (web). Space.com. Retrieved 2008-02-19. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help) - talks about how our ability to produce antimatter is increasing. And states that a Antimatter pulse drive may be feasible with in the next few decades.
• Weidenspointner, Georg (2008-01-08). "An asymmetric distribution of positrons in the Galactic disk revealed by big gamma-rays" (Journal). Nature. doi:10.1038/nature06490. Retrieved 2008-02-19. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help) - You don't need to produce antimatter, if it simply exists in large quantities. New study points to asymmetric distribution of positrons.
• Bickford, James (2000-03-29). "Extraction of Antiparticles Concentrated in Planetary Magnetic Fields" (pdf). NIAC. Retrieved 2008-02-19. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help) - It might be that any civilization needs to be near galactic center in order to collect antimatter cheaply. This small abstract explains that collection might be possible with any planetary magnetic field. Thus humanly possible, if not currently feasible.--Sparkygravity (talk) 13:52, 20 February 2008 (UTC)

Antihydrogen should be moved into section "production".

I would move Antihydrogen into section "production". How to do it best: should it be sub-sub-section? dima (talk) 00:18, 8 May 2008 (UTC)

Asimov writing about positronic brains?

There is a Although Asimov wrote a lot of stuff about "positronic brains" there is nothing in his works to suggest that these were actually driven by positron's. I even read somewhere that he just thought it was a good name for a robot brain. This doesn't belong here. If there are no objections I will delete the mention of it. —Preceding unsigned comment added by Marcusyoder (talk • contribs) 17:11, 13 June 2008 (UTC)

Trivia sections are discouraged by Wikipedia (as the template says) and there is nothing of benefit to the article in that section, so quite frankly, tbe whole section should go. Personally, I would sooner see "The Man from UNCLE" go before Asimov who is a favourite of mine. At the time Asimov cane up with positronic brains, the positron had only just been discovered, making it the first known antimatter. By calling his technology positronic Asimov made it sound bang up-to-date, however, he was always quite obscure about how it actually worked. SpinningSpark 19:46, 13 June 2008 (UTC)

Introductory Paragraph Needs Work

Here is the end of the first paragraph:

The particles resulting from matter-antimatter annihilation are endowed with energy equal to the difference between the rest mass of the products of the annihilation and the rest mass of the original matter-antimatter pair, which is 50% anti-matter (Other 50% are Neutrinos) to energy efficient. Which means that for instance if you had 500 grams of anti-matter and 500 grams of matter it would perfectly make the energy of E=MC2(mass in kilograms equaling 1 in this situation).

The writing is so poor that I'm not sure what is meant, and the tone is conversational. Furthermore, does this level of detail belong in an introductory paragraph? If nobody objects, I suggest either removing these sentences entirely (my preference), or replacing them with just: "The particles resulting from matter-antimatter annihilation are endowed with energy equal to the difference between the rest mass of the original matter-antimatter pair and the rest mass of the products of the annihilation."

DRE (talk) 23:24, 11 July 2008 (UTC)

just wondering...

I am far from a physicist and so I may sound naive, however I am curious about what was meant about antimatter theoretically moving backwards in time. From my understanding antimatter is virtually the same as matter in most aspects except that the charges are reversed for each case? If this is so, and the kind of spin etc. is all the same, then how could it be moving backwards in time? Also, if this hypothetical antimaterial universe exists, then from our understanding is it plausable to assume that it would virtually be a mirror image of our own, except that the charges of all particles invloved are reversed? Or if not then what would be different about it? I realise it is a question more for science fiction than science, but can anyone tell me what could possibly be expected from such a universe? thanks alot, Rachel McMenamin. —Preceding unsigned comment added by Rjmcmenamin (talk • contribs) 12:47, 15 July 2008 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Antimatter/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Antimatter is a very important topic within physics, and one of the major discoveries of the 20th century, so I think it deserves a "top" importance designation. The article itself has lots of good information on physics, history, and speculation, as well as links to a number of other articles. I think it could use a bit of editing for readability and, there are a few broken links and other problems that could benefit from some cleaning up. Wesino 17:58, 30 November 2006 (UTC)

Last edited at 17:58, 30 November 2006 (UTC). Substituted at 20:10, 2 May 2016 (UTC)

Uses - hypothetical weapons

I feel the hypothetical possibility of weapons should be included. This is my suggested wording, others can probably improve it:

Less positively, antimatter has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities. However, the U.S. Air Force funded studies of the physics of antimatter in the Cold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. Switchcraft (talk) 10:33, 26 February 2013 (UTC)

That wording would way overstate the plausibility of the idea. Currently, making a single atom of antimatter (as opposed to isolated particles) is a major achievement. Putting together enough to make a weapon is nowhere on the horizon, and even then you would have the problem of safely confining it. Looie496 (talk) 16:34, 26 February 2013 (UTC)

I included it but with "there is no evidence that it will ever be feasible" (I hope). Switchcraft (talk) 10:34, 9 March 2013 (UTC)

References

Standard model

I think the words standard model need to be in here someplace. Student7 (talk) 22:57, 28 March 2013 (UTC)

Gravity Experiments at Cern

Are current experiments with antihydrogen at Cern to determine the effect of gravity on antimatter worth a mention here? News outlets are reporting on "antigravity" experiments on the off-chance antimatter responds negatively to the Earth's pull, which is rather silly, but even a modest gravity asymmetry could be a potential part of a solution to the baryogenesis problem (hard to rule out since we really have no idea why non-anti particles have the random-ass gravity charges they do). TricksterWolf (talk) 19:09, 30 April 2013 (UTC)

Something sourced (preferably from a scientific source) could certainly go in. SpinningSpark 20:15, 30 April 2013 (UTC)

The problem, if the BBC story I read can be relied on, is that the results thus far are so weak that they hardly say anything at all. If the experiment yielded any meaningful information it would be worth discussing, but so far there doesn't seem to be any. Looie496 (talk) 22:51, 30 April 2013 (UTC)

The fact that they are looking is the thing worthy of note here. After all, we have a wide selection of articles on grand unified theories, string theories and supersymmetry without any experimental evidence at all that any of these things even exist. SpinningSpark 23:53, 30 April 2013 (UTC)

To say nothing of Dark matter and dark energy which they are "pretty sure" exist, but have no basis in exact particle analysis just yet. Anyway, they are spending billions of euros on the project. That alone should count for something!  :) Student7 (talk) 17:54, 5 May 2013 (UTC)

Terrible and misleading

This article goes out of its way to talk about the properties of (atomic) antimatter as if more than a couple of atoms have been observed, ever. This is wrong headed and misleading. 99.999% of the references in the Scientific literature to antimatter are to the elementary particles. Only in the popular press and especially science fiction is antimatter meant to be atomic antimatter. This has not been made clear here, instead the article goes out of its way to confuse the two types of antimatter. This is pragmatically harmless, since atomic antimatter is almost a null set, but confuses the difference between the two at a higher level of abstraction. I recommend a rewrite to depreciate atomic antimatter, and to clearly differentiate between the antimatter we use everyday (positrons, for example) and the antimatter that just a couple of atoms have been confirmed ever to have existed, and those only for a fraction of a second.173.189.75.67 (talk) 22:00, 7 May 2013 (UTC)

If you can see specifically how to improve the article in this respect, I encourage you to take a shot at it. Regards, Looie496 (talk) 22:42, 7 May 2013 (UTC)

Alkahest?

The article does speak of the difficulty of containing anti-matter. I think this difficulty should be "repeated" or reworded for the subsection which contains "fuel" and "weapons." There is an uncomfortable alchemy feel for suggesting that a container might be readily available for what is, essentially, an alkahest, once (or if) the production of anti-matter becomes possible. Student7 (talk) 20:15, 19 July 2013 (UTC)

Add a Footnote

In the section Origin where it reads as follows:

Almost all matter observable from the Earth seems to be made of matter rather than antimatter. If antimatter-dominated regions of space existed, the gamma rays produced in annihilation reactions along the boundary between matter and antimatter regions would be detectable.[9]

It should be changed to read as follows:

Almost all matter observable from the Earth seems to be made of matter rather than antimatter. If antimatter-dominated regions of space existed, the gamma rays produced in annihilation reactions along the boundary between matter and antimatter regions would be detectable.[9] A minority view holds that gamma ray bursts do reflect such annihilation between such boundaries. Footnote

There with this Footnote D.L. Mamas (2011) An explanation for quasars and gamma ray bursts. Physics Essays: December 2011, Vol. 24, No. 4, pp. 475-476. http://physicsessays.org/browse-journal-2/product/199-3-pdf-dean-l-mamas-an-explanation-for-quasars-and-gamma-ray-bursts.html.

— Preceding unsigned comment added by 96.228.244.95 (talk) 02:29, 18 June 2014 (UTC)

Semi-protected edit request on 1 July 2014

Hertzian radiation studies cast serious doubt on the antimatter theory. In the hertzian radiation mechanism, the antiparticle is nothing else than an electron flowing back in the opposite direction to the one it was initially injected from. The radio-electric transduction mechanism is fully consistent with Prof. John Archibald Wheeler's own intuition as aknowledged by Richard Feynman in his Nobel lecture. Moreover, evidence shows that the law of conservation of energy holds true, while leaves no room for keeping on theorizing about the positrone and the antimatter.

194.242.230.21 (talk) 07:17, 1 July 2014 (UTC)

That seems to me to be a) original research, b) not a reliable source, and c) a fringe theory. To say nothing of the serious cleanup needed for grammar, spelling and style issues. SpinningSpark 07:50, 1 July 2014 (UTC)

Agreed  Not done - Arjayay (talk) 08:23, 1 July 2014 (UTC)

Antimatter

We all know E=mc² therefore c=±sq root(E/m). Is the -sq root(E/m) a physical property/value from antimatter?197.245.92.84 (talk) 19:49, 19 September 2014 (UTC)SF Chang 19 Sep 2014

No, it just means that light can travel forwards or backwards along any given path. SpinningSpark 20:17, 19 September 2014 (UTC)

Jun 2015

I have made several edits that I feel are constructive to this page that have been reverted by user:Epigogue. I am a professional scientist in this field and a native English speaker, so I am confident when I say that many of this user's additions make the article less accessible. Can a third party take a look? cannywizard (talk) 12:40, 16 June 2015 (UTC).

The edits made by cannywizard were incorrect in terms of macroeconomics and nuclear physics. This interjection into my original words was undone on that basis.

Cannywizard's reversion to describing the rate of inflation as a change in price makes the article less accessible to people with backgrounds in economics or finance.

A simple explanation of why you are right and presentation of sources backing that up would be far more productive than making comments about the user who has challenged you. By the way, we don't require that editors should "add original clauses" in their contributions. Copyediting others is a perfectly acceptable activity. SpinningSpark 17:35, 16 June 2015 (UTC)

The main issue is that Cannywizard is factually wrong, as dollars cannot have prices in legal or economic terms. Here is the quote about inflation-"Eventually, the Manhattan Project employed more than 130,000 people and cost nearly US$ 2 billion (equivalent to US$ 23 billion in 2007 dollars)." Clearly, it does not reference the price of goods, which is a different measurement in economics. Copyediting is not appropriate when the copyeditor introduces an error by failing to read the reference.Epigogue (talk) 19:55, 16 June 2015 (UTC)

If I have understood cannywizard's issue correctly, he thought that the date (2007) should be stated after you had removed it, rather than disputing the nature of the figures. I agree with that, if the date is not stated the article will eventually go out of date and be inaccurate. I'm pretty sure it says exactly that in the guidelines somewhere but can't be bothered to look it up. However, since your latest edit has retained the date everyone should now be happy, no? SpinningSpark 20:10, 16 June 2015 (UTC)

The current figure should be about 27 billion adjusted for inflation over the past 8 years. It is not an accurate estimate, anyway; Since the demand for raw materials used in the Manhattan Project has risen faster than the rate of inflation. I would have been happy from the start if cannywizard had simply added the date, because the word 'prices' implicates a much more inaccurate estimate- the metals used in the project are pricier by a factor of 40. It would cost about 100 billion to re-do the Manhattan Project.Epigogue (talk) 00:58, 17 June 2015 (UTC)

If Epigogue trying to extrapolate the costs to present day, then we're entering the realm of original research. It's factual to stick with the dollar value in 2007 prices as in the article. cannywizard (talk) 08:57, 17 June 2015 (UTC)

It is not factual to do so because the article is estimating by gross inflation, not budgetary costs; so the estimate is not in terms of any 'prices'Epigogue (talk) 10:29, 17 June 2015 (UTC)

Spinningspark has interpreted my issue with this edit, correctly, but I also have issues with other edits of mine that have been reverted - https://en.wikipedia.org/w/index.php?title=Antimatter&oldid=666030550 and https://en.wikipedia.org/w/index.php?title=Antimatter&oldid=667161869. Both add over-technical, near-impenetrable language to the article. Neither "ionically unstable" nor "cyclic processes" nor a long description of neutron star processes helps the article in any way. I'm a professional particle physicist, and I don't understand what it means. To the averaged wikipedia reader it's not going to add anything. cannywizard (talk) 08:57, 17 June 2015 (UTC)

I do not know if Cannywizard can fathom physical chemistry, but there is a spectrum of readers between that user and the average; and at least some of them get it. As a scientist, if one does not understand something, then one should always ask a question. If anyone disagrees with me on the basis of fact, then I welcome the argument.Epigogue (talk) 10:29, 17 June 2015 (UTC)

The majority of readers of this article are not scientists (and I would be horrified if nuclear scientists were coming here to get their information). Encyclopaedia articles should be written primarily with the general reader in mind. It's fine to use technical terms in an article, but readers should be given some hope of understanding what the terms mean. Wikilinking, in-article explanantion, or footnote glossing are all acceptable means of achieving this. SpinningSpark 19:02, 17 June 2015 (UTC)

Feynman interpretation and Canetti

I still have doubts about the New Journal of Physics, but a minority view on the gravitational properties of antimatter should be noted as such. According to my understanding, and our article on the gravitational properties of antimatter, the predominant view is that the inertial mass is equal to the gravitational mass, and is positive. The last paragraph (which I'll copy when I get home) seems to have the opposite POV. (If it's "open access", there should be a URL for the article.) — Arthur Rubin (talk) 23:36, 1 July 2015 (UTC)

Not quite sure what you're talking about with the minority view of the gravitational properties of matter. The FS interpretation certainly says no such thing, and from a cursory glance at http://iopscience.iop.org/1367-2630/14/9/095012/pdf/1367-2630_14_9_095012.pdf, I can't find anything in there (on in our article) which supports that inertial != gravitational, or that mass is negative. Headbomb {talk / contribs / physics / books} 01:53, 2 July 2015 (UTC)

No, but what you DO find in there is a primary source masquerading as a review. The review part is okay, but not the rest. The authors do not go on to say that in their new theory "antimatter falls apart" which is the statement the cite references. That whole sentence should go. Canetti et al. admit that what they are floating in this paper, at the end, is a new "testable hypothesis" beyond the standard model, which has something to do with baryogenesis by means of Big Bang oscillations of a hypothesized sterile neutrino which has not been detected, but which the authors are going to use, to explain dark matter, too! All Nobel Prize stuff if it works. Meanwhile, it is just some beyond-Standard Model hypothesizing, like a thousand string theory papers. By definition it has not yet been tested and is not standard or accepted. Such things have no place explaining anything so basic as antimatter, in Wikipedia. Feynman and Stuckelberg are fine. The rest is not. SBHarris 03:05, 2 July 2015 (UTC)

I'll agree on that point. Headbomb {talk / contribs / physics / books} 05:32, 2 July 2015 (UTC)

That's what I meant by my comment. The source is provides a (as they put it) "testable hypothesis" which might lead to a new theory. Even if "antimatter falls apart" was a consequence of their their theory, it shouldn't be in the "history" section, but in a separate "speculations" section. It is noted in the Gravitational interaction of antimatter article that some speculate that antimatter would have antigravity; if it repelled itself, then it would "fall apart" on large scales. — Arthur Rubin (talk) 00:55, 3 July 2015 (UTC)

Question about the webm nasa video

The video states that when an electron can create gamma ray when it hits an atom and in return when that gamma ray hits an atom it creates another electron and a positron. Is this energy conversion from speed/force of impact? 2601:280:C301:215D:0:0:0:32BF (talk) 19:01, 31 October 2015 (UTC)

New Measurement of Antihydrogen Electric Charge

Phys.org report on M. Ahmadi et al. An improved limit on the charge of antihydrogen from stochastic acceleration, Nature (2016). DOI: 10.1038/nature16491, which reports on the most precise measurement yet of the electric charge of antihydrogen. — Preceding unsigned comment added by Ecwiebe (talk • contribs) 23:02, 20 January 2016 (UTC)

References

Time to create a gram of antihydrogen

I found this surprising paragraph in the article: "In 2016 a new antiproton decelerator and cooler called ELENA (E Low ENergy Antiproton decelerator) was built. It takes the antiprotons from the antiproton decelerator and cools them to 90 KeV which is "cold" enough to study. More than a hundred antiprotons can be captured per second, a huge improvement, but it would still take several thousand years to make a gram of antimatter." I refer to the final sentence, in particular.

If you replaced "years" with "lifetimes of the universe", the statement would be more accurate. For comparison: at one million (10^6) particles per second, it would take about the lifetime of the universe (over 10^10 years, one year is 3*10^7 seconds) to produce an Avogadro's number (6*10^23) of particles -- a gram of antiprotons.

I should probably fix this myself. However, I'm still uncertain enough (not about the facts, but about proper editing) to ask someone else to change this. --Johnm307 (talk) 01:41, 2 October 2016 (UTC)

You see one reason I didn't change it myself. I meant to create a new section, rather than tack it on the end of this section. --Johnm307 (talk) 01:48, 2 October 2016 (UTC)

@Johnm307: Yes, it's more like a nanogram in a few thousand years. But that whole insertion really needs a citation. SpinningSpark 10:27, 2 October 2016 (UTC)

Citation 63 404

Just clicked on citation 63 looking for more info, only to find it leads to this: http://i.imgur.com/Z7PAMEt.png

Link to see for yourself: http://www.engr.psu.edu/antimatter/Papers/pbar_med.pdf — Preceding unsigned comment added by SecretNenteus (talk • contribs) 17:06, 3 October 2016 (UTC)

That's because the link goes to a, probably copyvio, copy of the paper on a university website. People never learn that those kind of links only stay up as long as the professor's students need them. It was probably this paper, but I can't be sure because the full citation information wasn't given. SpinningSpark 20:25, 3 October 2016 (UTC)

Update: Wayback Machine archive verifies it is the same paper. SpinningSpark 20:28, 3 October 2016 (UTC)

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Antihelium

I think that it should be called Antihelium--4(Antihelium negative four). After all, Antiparticles are basically negative versions(negative numbers, not charge) of particles.32ieww (talk) 01:37, 12 February 2017 (UTC) 32ieww (talk) 01:37, 12 February 2017 (UTC)

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