Untangling the question of antimatter mass A group of researchers at University of California Riverside hopes to chip away at one of physics’ ‘question of questions’ – why the blazes we’re here at all. Their hope is to make electron/positron pairs live long enough to measure the positron’s mass and find out if it’s different to the electron. It’s a puzzle that resists …
OK while we're on the topic of matter/anti-matter, maybe a physicist can answer a few questions for me.
Given:-
(1) Matter has mass.
(2) Anti-matter has mass.
(3) Collide matter and anti-matter and you get photons(energy) . They have no mass.
Q1 - Where the hell does the 'mass' go ?
Q2 - What's so special about anti-matter that enables it to unzip ordinary matter into a bazillion massless photons ?
Q3 - if everything can be converted to photons then aren't electrons, quarks etc at the same level as atoms ? ie. not really fundamental at all ?
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> Q1 - Where the hell does the 'mass' go ?
Matter is converted into either energy (and by this I mean “converted into photons”), or other types of matter (pions).
> Q2 - What's so special about anti-matter that enables it to unzip ordinary matter into a bazillion massless photons ?
Long story short? There isn’t anything. (In theory.) Antimatter is composed of different fundamental particles, but (in theory) these particles are completely identical to their “regular” counterparts, excepting that the charge/colour/flavour of the given fundamental particle is exactly the opposite of its antiparticle.
Thus when you get a particle and anti particle together they (and I am REALLY simplifying this here) attract eachother with such a powerful force that they obliterate eachother. (Thing car crash.) This particles to convert into other particles.
>Q3 - if everything can be converted to photons then aren't electrons, quarks etc at the same level as atoms ? ie. not really fundamental at all ?
Matter/antimatter collisions don’t produce exclusively photons. A proton/anti-proton reaction actually produces pions indeed of photons. These pions decay about 25% into high-energy photons on the one side and 75% (via a few different routes) into neutrinos on the other.
Remember that a proton and an anti-proton are not in fact annihilating eachother. Instead, the quarks and anti-quarks that are the constituent parts of these larger particles are doing the sub-atomic dance of destruction.
Remember that electrons are leptons; fundamental particles in their own right. So their path to annihilation is actually completely different than protons, as protons are in fact aggregations of quarks.) Each fundamental particle’s interaction with its antiparticle is different than the next.
Even Bosons have antiparticles. The W boson for example has a direct antiparticle (W+ and W- particles). The photon (another boson, just BTW,) also has an anti-particle: itself!
Oh, yeah, didn’t I mention the photon was a particle, not just a quanta of energy? Silly me. But because a photon’s gague symmetry doesn’t break, (i.e. it doesn’t interact with the Higgs field) it doesn’t have a rest mass.
In other words, there are indeed fundamental particles other than photons. Everything does not “convert into photons.” In fact, there are all sorts of ways for particles to convert from one into the other. But each fundamental particle acts completely differently from the other. That’s part of what makes them “fundamental.” They don’t break into smaller ones, and they all have entirely unique behaviours.
Ok. I know the matter gets converted. My question was how do we go from particles that have mass (quarks and electrons) to particles that have no mass (photons). What is it about anti-matter that causes this to happen with such apparent ease ? If we look at electrons, here we have a particle with mass that can apparently disintigrate when it touches an identical partical with opposite charge. Why does it do that ? Or am i completely missing something important here ..
"3) Collide matter and anti-matter and you get photons(energy) . They have no mass."
The flaw in your theory is that photons DO have mass. See:
http://hubblesite.org/newscenter/archive/releases/2003/01/image/a/format/web_print/
For more, look up "gravitational lensing" in your favorite search engine. From there, you should be able to track down an easy reference as to why mass and energy are synonymous ... and don't actually "go away", but are converted into another form. Simplistic? Yes, at this level, in under 75 words and an URL. But it works for my nieces & nephews ...
I thought that gravitational lensing worked because the fabric of the universe was curved around the mass, and that the light traveled in straight lines through the curved space, and hence only appeared to be bent (if you're struggling with that, think light travelling through a fibre-optic cable).
"I thought"
Dangerous, that ...
"that gravitational lensing worked because the fabric of the universe was curved around the mass, and that the light traveled in straight lines through the curved space, and hence only appeared to be bent."
The gravity of your misconception is staggering ... bottom line: energy is mass. Mass is energy. Both interact with each other.
Curved, bent & straight (etc.) space are figments which attempt to teach TheGreatUnwashed[tm] concepts that they have absolutely no concept of ...
1) The mass goes into the energy of the photon - E = mc^2, the energy of the photon being related to its wavelength, the higher the energy, the shorter the wavelength, so gamma rays are more energetic than visible light, which is more energetic than infrared, which is more energetic than radio waves, etc.
2) The 'standard model' of particle physics states that every particle has an equivalent anti-particle. Combine these, you get a photon. Photons can spontaneously split into particle/antiparticle pairs but since these start off right next to each other, they tend to annihilate each other straight away and you get your original photon back again. The notable exception to this is the special case where this happens at the event horizon of a black hole and one particle (or antiparticle) goes over the event horizon and the other doesn't. This results in the black hole gradually losing energy adn therefore mass, and is known as 'Hawking radiation' after the well-known physicist who predicted it.
3) Whilst every particle has an antimatter opposite, this doesn't make them the same. A positron, for example, can annihlilate an electron, but not a proton. Atoms themselves are not fundamental particles, they are composed of protons, neutrons, and electrons. Protons and neutrons themselves are composed of quarks, IIRC.
....I did study university-level physics and I am a keen student, so I will give these questions a shot.
A1) The mass is converted to energy according to the famous Einstein equation I need not repeat here. The photons emitted are gamma rays with LOTS of energy.
A2) That is what the boffins are attempting to determine. AFAIK the only distinction that is definitively known about partices vs. antiparticles is opposite electric charge. This would imply, for example, that there is no such thing as an antineutron. Photons are massless which is equivalent to saying they move at the speed of light; but photons of different wavelength have different energies.
A3) There is a lot of reason to believe that quarks themselves are not fundamental; I refer you to M theory, a.k.a. superstring theory, for elaboration. Brian Greene is an excellent resource.
The reason that the anti-proton has a negative charge is that the anti-quarks that make up the anti-proton have the opposite charge from the quarks that make up a proton. The proton contains two quarks with plus 2/3 charge and one with minus 1/3 charge. The neutron contains 1 quark with plus 2/3 charge and two with minus 1/3 charge for a net charge of zero. The anti-neutron contains two anti-quarks with plus 1/3 charge and one anti-quark with minus 2/3 charge.
You needn't wait for such a rare event. Type II supernovae explosions are driven* in part by neutrino heating. So many neutrinos are released in the core that their interactions with the shell have a pronounced effect. No doubt if you were close enough you could feel the neutrinos too (for a brief instant before being atomised by the explosion).
Almost all the neutrinos escape of course, to the point at which they can be detected on Earth as in SN1987a. If you want to stress the exponent facility of your calculator, work out the surface area of a sphere radius 168,000 ly, divide it by the cross-section of the three neutrino detectors involved and then again by the probability of neutrino capture. Multiply by 24 (the number detected) and you have an estimate of the number emitted. It's a VERY big number, even by astrophysical standards :) - and SN1987a was an oddly small (for a supernova) explosion.
* At least, according to our best current theories, which are some way from a perfect understanding.
What I like most about science is that bright people are hell bent on improving our understanding of the universe and our place within it.
What I don't like about science is that very bright people are hell bent on improving our understanding of the universe and our place within it and are letting the morons* ruin our lives within it.
*Politicians for the most part.
What I don't like about dumb people is that they don't like bright people, becuase it reminds them of how dumb they are, so go on ignoring what they are told by bright people who are hell-bent on trying to improve our understanding of the universe.
Cases in point are 'intelligent design' and anti-global warming proponents, not to mention those responsible for thing like drugs policy who have such a massive aversion to demonstrable facts.
The solution, of course, is in part to ensure that everyone gets a good education, in particularly a strong foundation in maths and the sciences. You have only to look at which nations provide such an education, and which do not to see which are the rising stars, and which are in decline.
However, ID and Anti-AGW people just don't have the ability to recognise how dumb they are, because that bit of brain appears to be missing.
Pity we can't transfer our knowledge, experience and wisdom to new generations more efficiently than continuously having to educate each new generation of potential cave-people from scratch.
One problem with getting a good education is that everyone else becomes relatively more stupid, but quite why people happily boast about being thick, and celebrate ignorance is just beyond me.
Education is absolutely crucial for the future of the whole planet.
If the author had checked with the wikifiddlers he'd find that
"In physical cosmology, baryogenesis is the generic term for hypothetical physical processes that produced an asymmetry between baryons and antibaryons in the very early universe, resulting in the substantial amounts of residual matter that make up the universe today."
which is what the author thought baryogenesis meant.
I thought Lucy was pretty good and missed her when she left. Lester wasn't a bad substitute but Richard is pretty good. He explains things clearly, lets you know where he thinks he may have a lack of understanding and manages to make readable articles.
And now back to my copy of Scientific American...
No, we know the *mass* of the positron. What we don't know is whether gravity treats "antimatter mass" like "normal matter mass". Is matter attracted to antimatter? Or does matter repel antimatter? Or do they just experience slightly different gravitational forces? We don't know for certain because the gravitational force is dwarfed by the electromagnetic one. So scientists create electrically neutron atoms containing antimatter, and then see how they interact with gravity. It's expected that antimatter will behave the same, but it isn't yet proven.
At least, that's my reading what they're trying to do. (The first sentence of the linked press release is "Does antimatter behave differently in gravity than matter?") But I couldn't find the paper on arXiv, so I may have got the wrong end of the stick.
@see http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter
There are three parts to this*:
1) We don't know whether gravity treats matter and anti-matter identically (eg whether they're identically affected by the Higgs field, or <insert gravitational theory here>)
2) We know that electrons and positrons have very similar masses, but not that they're identical.
3) In a direct annhililation, the tiny fractional differences in mass would be utterly swamped by uncertainties in the measurement (both experimental and fundamental). In the proposed experiment, if the lifetime (and hence beam length) of the positronium can be made sufficiently large, it may be possible to reduce the uncertainties to such an extent that the differences are measurable.
* I don't see how the proposed experiment could disentagle the effects of 1) and 2), but maybe that's why I can only call myself a physicist if I add the prefix 'failed'.
My view on antimatter is, that it is the mind and consciousness of all living entities.
You are your own universe.
Reality is where the minds (antimatter) meets the physical universe.
There is as much antimatter as matter. The reason it seems that there is much more matter than antimatter, is because the majority of antimatter is located in parallel universe. One of them being your mind.
Interested? Then read my philosophical multiverse theory.
Google crestroyer theory, and find it instantly.
http://crestroyertheory.com/the-theory/
"While other experiments have created long-lived antimatter (CERN has created anti-hydrogen with a thousand-second lifetime), what's notable about the Riverside experiment is that it seeks to create a long-lived antimatter that can be put in a beam."
Antimatter beams are nothing new. For example, CERN's LEP collider (which used to be in the tunnel now used for the Large Hadron Collider) used a positron beam. SLAC is another example.
Oh, and regarding "long-lived" antimatter, may I suggest Googling "storage ring"?
I've just read the article again, and while it's clear the article is talking about "a matter/anti-matter bound state", the article didn't explain why electrical neutrality is needed, and why a storage ring full of positrons wouldn't do.
The bit of the article I was responding to didn't even specify electrically neutral particles containing antimatter. It said, "what's notable about the Riverside experiment is that it seeks to create a long-lived antimatter that can be put in a beam."
Nowhere in the article was the significance of electrical neutrality explained. Without that explanation, it seemed the point of it was "to create a long-lived antimatter that can be put in a beam", since that's what the article itself said.
Since reading the comments here, I now know the article is woefully deficient, in that the key flippin' point is completely omitted. If only I could go back and re-rate the article, I'd give it a lower rating accordingly.
They didn't do it when I was at school either. However, instead of waiting for someone to spoon feed me the stuff, I went and bought some books and read up on it myself.
Go to your local Waterstone's, and visit the Popular Science section. My suggestion is to look for stuff by John Gribbin. (I know Brian Greene maybe a science best-seller, but I found his stuff quite heavy going.)
I think distance between "A level" and "recent popular science books" is an order of magnitude less than the distance between either and "what experts are doing right now". A couple of decades ago, I did a degree in this shit, and I was pretty confident when I graduated that I was less than half-way there. OTOH, I've a much clearer idea than most people of just how much I don't understand.
I love this stuff but it turns my brain to mush every so often.
Quantum: Einstein, Bohr and the Great Debate About the Nature of Reality by Manjit Kumar
Is a very good introduction into the quantum world. But it's still a brain twister at points. The human mind just isn't built to visualise some of these things which just don't fit with what seems logical.
Kudos to our boffins who know this stuff. Just keep to the other side of the room at parties please.
Given that positron tracks can be observed in cloud chambers, and we know their electric charge and can measure their velocity, surely we can calculate their mass from how sharply their paths bend in a known electric field. In a horizontal cloud chamber, gravitational effects are irrelevant. So to then see if gravity affects antimatter differently from matter, turn the cloud chamber on its side and see if you get different results.
What am I missing?
Two particles, different mass (ie energy) meet up, decide to smash into each other in the hope of total obliteration. Everything is lost yet somehow something remains - surely?
For true total obliteration they would need identical energy (mass) or to have drunk an awful lot of Stella.
Except that particles never actually annihilate. What we think of as “annihilation” of a particle/anti-particle pair is in fact nothing more than the conversion of two fundamental particles into various other fundamental particles.
Think of it more like decay. (It’s not, in the physics sense, but let’s bypass that for a moment here.) Two particles are so very strongly attracted to each other because – for all intents and purposes – they are the same thing but with a different charge/flavour/colour. (Think positive and negative electromagnetic charge attraction.) They try to “become one with eachother,” which doesn’t really work all that well.
A proton or a neutron is composed of these things called quarks. Now when you get a proton and an antiproton together they shatter into a little cloud of quarks. These quarks very rapidly reassemble into pions (a pion is composed of two quarks). Pions then decay (mostly) into either photons or neutrinos.
This is an important concept. The proton/antiproton pair does not convert into energy. In fact, no energy is released during the initial collision at all! Instead, they are “smashed into little bitty bits.” The “little bitty bits” don’t like being bits – quarks are social particles, they have this weird need to hang out with eachother – and they immediately reassemble into pions.
But here there’s a problem; quarks are like you and I. They don’t do well in a two-quark relationship. It always goes sour. So these two quark pions rapidly fall apart and the quarks commit hara-kiri, choosing instead to live life as some other particle.
For the most part, they choose to be neutrinos. But some quarks want to go out with a bang and convert directly to high-energy photons. Still other quarks decide to assert their independence and choose to convert into an electron/positron pair, which promptly annihilate themselves by converting into photons.
Well.
*mostly*
You see, electron-positron annihilation is not so cut-and-dried. It really is all about “how much energy the little buggers have.” If the electron/positron pair have enough energy – say because they absorbed the high-energy photons emitted by the decay of some of the other pions – the electron-positron anhillation will not in fact produce photons. Instead, they’ll produce D mesons.
And a D-meson is…
…two quarks.
Oh, but that’s not all! Apparently, with even more energy, an electron/positron collision will actually create a W+/W- boson pair, or a Z boson! Which is interesting, because W and Z bosons are actually force carriers and not really particle sin the way you are used to thinking about it.
So…nothing is ever lost. It all just gets continually recycled. What various subatominc “annihilations” ultimately end up producing (pions, D mesons, bosons, photons, etc.) actually is down to “how much energy did the particles attempting to squish eachother into the same fragment of spacetime have?”
The more energy the particles had on contact, the weirder the resulting particle soup.
Ball lightning is a naturally occurring Rydberg positronium cloud generated at high altitude, that travels down the plasma channel and emerges at a point where the channel narrows or changes direction.
This neatly explains many of its bizarre properties including its ability to be deflected by iron, as well as how it appears to "emerge" from household wiring as the plasma channel weakly links to the wiring during a lightning strike acting as a conduit.
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