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Underground Lab To Probe Ratio of Matter To Antimatter
Posted by
Soulskill
on Sat Oct 25, 2008 04:14 AM
from the scotty-unavailable-for-consult dept.
from the scotty-unavailable-for-consult dept.
Wired reports on the Enriched Xenon Observatory 200, a particle detector scientists hope will answer the question of why there is significantly more matter than antimatter in the universe. Quoting:
"The new detector will try to fill in the picture, determining basic features of [neutrinos], like their mass and whether or not they, unlike almost all other particles, are their own antiparticles. That quirk is why some scientists believe neutrinos could be the mechanism for the creation of our matter-filled universe. Almost all other particles have an antiparticle twin that, if it comes into contact with the particle, immediately annihilates it. But if neutrinos are their own antiparticles they could conceivably be knocked onto matter's 'team,' thereby causing the cascading win for matter over antimatter that we know occurred. As the Indian theoretical physicist G. Rajasekaran put it in a speech [PDF] earlier this year, neutrinos that are their own antiparticles would explain 'how, after [the] annihilation of most of the particles with antiparticles, a finite but small residue of particles was left to make up the present Universe.'"
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How can you tell? (Score:1)
I thought it wasn't possible to tell antimatter from matter from afar?
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IP Finding [ipfinding.com]
the neutrinos are everywhere (Score:5, Funny)
Even in your closet!
So you don't have to look afar.
Parent
Re:the neutrinos are everywhere (Score:5, Funny)
Even in your closet!
Neutrinos are gay?
Parent
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Except most of them are not even sure what >90% of the universe is made of, so what makes them so sure that the rest of the universe is mostly straight?
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I have no real explanation for the release of free energy in this case, but there's definitely no offspring; I think you get the idea ..
My understanding was that matter and anti-matter are more like straight women and straight men. When anti-matter and matter collide they emit gamma rays, and if the gamma rays are sufficiently dense they can condense back into either matter or anti-matter. So there are at least three good explanations for a mostly female universe: either there were more women to begin with,
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Gays are everywhere! Vote yes on 8! We have to stem the tide of gay neutrinos! Think of the children! They'll all be made gay if we let the neutrinos take over the school system!
Re:How can you tell? (Score:5, Interesting)
That's the premise in one of Larry Niven's old Beowulf Shaeffer stories (collected in Crashlander [amazon.com] ). Shaeffer and a Steve Fosset-like millionaire come upon an isolated planet, only to discover to their dismay that it is made out of antimatter. Unfortunately, the relatively believable science ends there, because Niven's way of having them colonize it relies on a species of unobtainium
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-Spoiler-
I remember the story differently:
They cannot figure out why the planet and sun are such an anomaly
(high velocity indicating origin outside of the milky way, no sign of interstellar debris, unusual high activity of the sun)
They argue about landing on the planet, even thought their ships hull gets damaged by an unknown force
In the end they decide not to risk it, and go back to civilisation, and only then are told that their hull must have been damaged by antimatter, that therefore the whole system wa
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"Crashlander" follows the story of Beowulf Shaeffer for a few years (it's actually a set of different short stories held together by a "glue" story). It is said in the glue story that matters got complicated, the UN got involved and eventually nobody went back due to bureaucratic reasons.
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In the last two Ringworld books, the design of the UN ships reveals that they are powered by antimatter and as I recall, The Hindmost tells his allies that the UN has possession of an antimatter system which presumably is the same one Shaeffer and Elephant visited. The Kzinti's source of antimatter remains a mystery. The most recent Man-Kzin Wars book might discuss it.
Shaeffer must have been good about keeping secrets since his son Louis apparently does not know about any of his father's exploits. Oddly
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Spoiler for yourself CRCulver (715279) and Ernesto Alvarez (750678) : there is significant new matter on this in the recent "Juggler of Worlds" by LarryN and ANOther.
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Spoiler space
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There isn't any plan to colonize the antimatter planet as such, but there is a plan to send people and/ or equipment to mine the antimatter planet. The military implications of this are not lost on the pacified species (Kzinti) of Known Space, nor on the several remaining dangerous, if not aggressive, species (not named - RTF
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In my recollection, the idea that it might be colonized using a stasis field was one reason Niven opened Known Space to other writers and took a bit of a hiatus himself (and then went back and covered the earlier history a bit). He felt that too many problems were too easily solvable at that point.
Re:How can you tell? (Score:4, Informative)
In a perfect vacuum, it isn't. However, even the intergalactic medium isn't a perfect vacuum, and somewhere there would have to be a border between a matter region and an antimatter region. Such a region would give off a very specific gamma ray spectrum, with a peak at 511 keV due to positron-antipositron annihilation and several peaks in the 70-400 MeV range due to proton-antiproton annihilation; the rate of interaction would be low, but the surface area of the frontier so large that we should be able to observe it from Earth. If it is a more localized phenomenon (like Niven's star system), then it would be travelling through the interstellar medium, inside a galaxy, which is far denser.
Parent
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due to positron-antipositron annihilation
Am I missing something? Isn't a "antipositron" an electron? Generally the anti- prefix goes with the antimatter, not the matter.
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I meant electron-positron annihilation, of course. My brain had "proton-antiproton" in its head when I wrote that, and so it came out weird.
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Pardon my naivete, but given the theories of hyperexpansion in the early universe, isn't it just as likely that the preponderance of matter was strictly local, the same way the differences in the background radiation were exceedingly small, but sufficient differentiate spacial regions?
Neat as any gamma ray spectra at X keV would be, I would presume that any ongoing border between a matter/antimatter region would create sufficient 'pressure' for the regions to not mix, the same way dropping sodium on water
How so? (Score:4, Interesting)
Re:How so? (Score:5, Informative)
If there had been an exactly equal amount of matter and antimatter since the birth of the universe, it would have long ago annihilated into photons. Since this has manifestly not occurred, one is in excess of the other. Which one you label as "matter" and which one "antimatter" is purely down to personal preference.
Some differences can be observed in the behaviour of matter and antimatter; for example, in a magnetic field, electrons will curve in one direction and positrons in another. Another example is the asymmetries observed in the oscillations of mesons (the classic example being the K0) which reveal a clear, fundamental difference between matter and antimatter.
Parent
Re:How so? (Score:5, Informative)
Even an easier explanation. The annihilation of antimatter with matter gives off very distinct spectral patterns. We know what these are, and we have calculated them for any observable red/blue-shift range. We've yet to observe any great quantity, or even a 'halo' around any other galaxies. In an equally distributed universe, you would see such things, as high-velocity matter from one universe collided with another, and give off pretty lights. We don't see such, hence, the universe is mostly matter.
Parent
Reserves still going strong, no need to panic ! (Score:5, Funny)
Dear citizens and members of the galactic Economic Council
The rumors about a shortage of antimatter to fuel or spacefleets and habitats is unfounded.
Everyday our scientists everywhere in this universe are finding new ressources, new anti-black stars to drill for our energy.
We used antimatter for thousands of millenia now, will continue for a lot more. I am happy to announce you the we finally opened for production that galaxy on the outer left reach of the milky way. There most advanced civilisation is a monkey like tribe that have barely learned to cover themselves and there was so to speak no Spaceflight activities to be observed.
One or two derelicts spacecrafts have been observed, but they use a primitive explosion system, so we are sure those Terrans will not mind if we pump their galaxy dry of the stuff.
The message from SF DR SD 3, President of ExNegMat power industries.
Parent
Re:How so? (Score:5, Informative)
Who says there is more matter than antimatter in the universe? Has anyone ever gone to the Andromeda galaxy? So how do we now it consists of normal matter?
Gas is observed between the galaxies, but not the hard radiation that would be produced when it reached a galaxy and annihilated.
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Additionally, if some far away galaxy consisted completely of antimatter, to the inhabitants of this galaxy we would clearly be the "antimatter people".
Like in telecommunications with another civilization somewhere else in the universe it would not be a trivial task to agree upon the meaning of "left" vs. "right" (no political pun intended here).
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"My parents have been on vacation to a planet where the dominant species has no lateral symmetry - and all they brought me is this lousy F-shirt!"
Obviously these guys need to watch more Star Trek (Score:5, Funny)
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Has a breach in Matter/Anti-Matter containment ever opened up a time rift? Not AFAIK...
Questions for a physicist in this field (Score:4, Interesting)
Does antimatter attract matter or repulse it (could a double star, one of antimatter and one of matter, i.e. where the stars revolve around each other exist?).
Would it be a prerequisite that a big bang produces as much matter as antimatter?
Bert
Re:Questions for a physicist in this field (Score:5, Informative)
Does antimatter attract matter or repulse it
*Charged* antimatter will attract its matter counterpart electrostatically via the Coulomb force. For example, an electron will attract a positron. This does not occur for neutral particles.
The gravitational attraction between bodies must also be considered: it is negligible between individual particles, but comes into effect for macroscopic objects. The gravitational interaction is determined by the amount of mass present, and is always attractive, regardless of whether it is between matter or antimatter.
(could a double star, one of antimatter and one of matter, i.e. where the stars revolve around each other exist?).
A star will be (on average) neutrally charged, otherwise Coulomb repulsion between like charges will break it apart. Therefore it is fair to say that both the matter and antimatter star will be electrically neutral or at least not significantly charged.
Even if there were two charged objects, the Coulomb force, like the gravitational force, follows the inverse square law, so extra electrostatic attraction will be equivalent to more mass.
In either case, a stable orbit could form.
Would it be a prerequisite that a big bang produces as much matter as antimatter
I'm moving out of my depth here, but the answer is probably no. Even if it did, future interactions between particles may cause an imbalance (as is thought to have occurred in our universe). A prerequisite for what, anyway?
Parent
Re:Questions for a physicist in this field (Score:5, Informative)
Would it be a prerequisite that a big bang produces as much matter as antimatter?
I'm moving out of my depth here, but the answer is probably no. Even if it did, future interactions between particles may cause an imbalance (as is thought to have occurred in our universe). A prerequisite for what, anyway?
I'm afraid the answer is actually yes, at least if you replace 'a prerequisite' by 'excepted from the laws of physics'. Since there is nothing in the laws of physics to make us believe that matter is 'preferred' over anti-matter, we naturally assume that the amounts of both in the early universe are the same. The problem with this most natural assumption is that, if there was the same amount of matter and anti-matter in the universe, and they stayed in thermal equilibrium as the universe cooled (which is true for most of its history), they would almost completely annihilate and there would be too little matter left over today to make up what we presently see. So we need an event that favours matter over anti-matter to produce the required leftover matter we see. This is called the baryogenesis problem [wikipedia.org]. Of course, you CAN just demand that the required extra matter be put in as an initial condition, but most physicists shun that approach, especially since the matter excess is one part in 10 billion, an unnaturally small number which would have to be put in by hand. We prefer to find a way to generate that asymmetry dynamically.
Parent
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Once again, why? Why isn't postulating that such an event must exist nothing more than forcing the universe into a preconceived box, and as such no different from something like creationism?
Saying "there may be a way of generating this asymmetry dynamically, and if so we should look for it" is not forcing the universe into a pre-conceived box. It is the opposite view, that anything we measure should just be explained away as an initial condition of the universe ("that's just the way things started out"), that is closer to creationism ("it's just the way god created it").
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Once again, why? Why isn't postulating that such an event must exist nothing more than forcing the universe into a preconceived box, and as such no different from something like creationism?
Saying "there may be a way of generating this asymmetry dynamically, and if so we should look for it" is not forcing the universe into a pre-conceived box. It is the opposite view, that anything we measure should just be explained away as an initial condition of the universe ("that's just the way things started out"), that is closer to creationism ("it's just the way god created it").
But the model that you use to "generate the asymmetry dynamically" can be described as "that's just the way things started out" too, so I'm not sure what the distinction is here...
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The gravitational attraction between bodies must also be considered: it is negligible between individual particles, but comes into effect for macroscopic objects. The gravitational interaction is determined by the amount of mass present, and is always attractive, regardless of whether it is between matter or antimatter.
This is an unproven assertion. Noone ever built a large enough lump of antimatter to verify that its gravitational force is indeed attractive. It is true that within the current physical theories gravity is always attractive (leaving aside the cosmological terms), yet, unless this is verified by experiment it is but a very convincing assumption.
Basic answer (Score:4, Informative)
Does antimatter attract matter or repulse it
IANA particle physicist or cosmologist, but I can answer this one: it depends on which particles. For example, a position (anti-electron) has opposite charge to an electron and will thus attract electrons and repulse protons.
Parent
To pick a nit (Score:2, Informative)
It's been theorized, I think, that the former is true, that it really is it's own antiparticle, based on hypothesized neutrinoless double-beta decay--which, if true, insinuates the former. But this is cl
Re:To pick a nit (Score:4, Informative)
See the graphic at http://en.wikipedia.org/wiki/Elementary_particle [wikipedia.org] and the article at http://en.wikipedia.org/wiki/Antiparticle [wikipedia.org] is also of interest.
Elementary particles with no charge cannot have an anti-particle, since the definition of anti-particle has to do with having the opposite charge, as I understand things.
Parent
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Actually, in the standard model, both neutrinos and antineutrinos exist and are distinct. The key point is that it is the weak, not electromagnetic, force that is important.
The weak interaction 'connects' leptons and neutrinos. For example, an electron can turn into an electron neutrino by emitting a virtual W- boson. Conversely, a positron turns into an anti-electron neutrino by emitting a virtual W+.
Just like electrons have non-zero electromagnetic charge, neutrinos and leptons have non-zero weak charge,
Re:To pick a nit (Score:5, Interesting)
Parent
Extension to the Standard Model (Score:5, Insightful)
The Standard Model assumes that all three neutrino species (electron, muon, and tau) are massless, and is essentially agnostic about whether neutrinos are their own antiparticles. If a neutrino is (is not) its own antiparticle, we call it a Majorana (Dirac) particle. Most any reaction which could tell the difference between Majorana and Dirac neutrinos can't occur in a Standard Model with massless neutrinos, so the difference is subtly and has no real experimental consequence.
We know the Standard Model is wrong, however. From neutrino oscillations, we know that neutrinos have tiny masses. This suddenly means that there ARE experimental consequences: neutrino-less double beta decay is possible for Majorana neutrinos but not Dirac neutrinos, for example. This is what EXO and many other experiments (GERDA, MAJORANA, CUORE, ...) are looking for. Existing results aren't quite sensitive enough to tell the difference, but new ones may be.
Just because something is not part of the Standard Model doesn't mean that it's unpopular - we need to change the Standard Model somehow, after all, since it's wrong about neutrino masses! My impression (as a particle physicist, but not in this sub-field) is that most particle theorists actually expect neutrinos to be Majorana particles. There are very interesting theories based upon a scheme called the "see-saw mechanism" which can simultaneously explain why neutrinos have such tiny masses and why the universe has so much more matter and antimatter. If neutrinos are just boring old Dirac particles, it will be back to the drawing board!
Parent
Re: (Score:3, Interesting)
a neutrino isn't actually it's own anti-particle, strictly, it's that a neutrino doesn't actually have a known strictly defined antiparticle equivalent.
IAAPP. Neutrinos have very well-defined antiparticles, and we observe them all the time in nature. We can verify that they and neutrinos have quantum numbers that are opposite to one another. Normally, for charged particles, the antiparticles have the opposite charge and so there is no question that these are distinct. But for neutral particles, really the only non-zero quantum number available is the handedness (this is related to helicity, which describes if their spin is left-handed or right-handed w
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Hmff, /. undid the moderations anyway. THEN WHY DO THEY ASK? :) Oh well.
This makes me wonder (Score:2, Flamebait)
When I first read "probe" (Score:2)
I guess I've got Quark on the brain from watching too much DSP DVDs.
"Underground lab" (Score:1)
Underground lab? (Score:2)
Aren't they supposed to make Meth or something? Why are they switching to Neutrinos? Do they give you an even better buzz? Has anybody tried Neutrinos? How was it?