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turban
2009-Jul-14, 06:33 PM
To discuss the possibility of antimatter galaxys.

Glom
2009-Jul-14, 06:54 PM
Imagine a love story between someone from a matter galaxy and someone from an antimatter galaxy. Sparks will fly...

trinitree88
2009-Jul-14, 07:34 PM
if you ever find an antimatter galaxy. There is no evidence that one exists. Only tiny bits of antimatter appear like fireflies...and then wink out.

Glom
2009-Jul-14, 07:37 PM
if you ever find an antimatter galaxy. There is no evidence that one exists. Only tiny bits of antimatter appear like fireflies...and then wink out.

You mean antimatter galaxies would be in the minority and be annihilated in short order?

turban
2009-Jul-14, 07:38 PM
How would you say so that they just disappear?

trinitree88
2009-Jul-14, 07:53 PM
You mean antimatter galaxies would be in the minority and be annihilated in short order?

777 Nope. Our known universe is ~ 99.9999999% matter. Normal protons, electrons, neutrons. It's true that violent collisions produce some positrons....cosmic rays, supernovae jets, pulsars hitting gas clouds, etc. but that's not the everyday stuff.
There is at present no evidence for an exact match to our matter universe, nor is there evidence of a gamma burst from colliding galaxies of the sort, nor is there substantial antimatter in our neighborhood. None.
We do see some 1.022 Mev gamma sources from electron/positron annihilations. Just not much. The observed asymmetry in matter over antimatter remains one of the outstanding theoretical problems unexplained in physics, and is completely unexplained by Big Bang cosmology. The small observation of an asymmetry in the b-meson factory doesn't do it....they're not baryons. pete

JustAFriend
2009-Jul-15, 02:00 AM
Considering that the nearest galaxy is 2 MILLION light-years away: Who cares?

(Unless you have an intergalactic Stargate handy under Cheyenne Mountain...)

tusenfem
2009-Jul-15, 07:09 AM
What happens when in Italy a truck loaded with pasta and one loaded with anti-pasta collide?


Dear Turban
It is nice that you want to open this thread, but just saying "to discuss XXX" is not really useful.

If you want to know something, or if you have questions, then just go to Q&A.
If you have some ideas that you want to have discussed, then state them here.
If you have some unconventional theory about anti-matter galaxies, take it to ATM.

But in all, participate, YOU started this thread, so YOU should come up with some stuff. If you don't I will feel the necessity to close this thread.

robross
2009-Jul-15, 07:24 AM
Say there were a galaxy made of antimatter, segregated from any other normal-matter galaxies. And say normal matter/anti-matter interactions in this galaxy occurred with the same frequency as they do in the Milky Way.

What would an astronomer on Earth expect to see, looking at this distant galaxy, to give them definitive proof that this galaxy was made up of anti-matter and not normal matter?

Rob

Glom
2009-Jul-15, 09:15 AM
Say there were a galaxy made of antimatter, segregated from any other normal-matter galaxies. And say normal matter/anti-matter interactions in this galaxy occurred with the same frequency as they do in the Milky Way.

What would an astronomer on Earth expect to see, looking at this distant galaxy, to give them definitive proof that this galaxy was made up of anti-matter and not normal matter?

Rob

If the galaxy was sporting a stylish goatee, that would be definitive.

robross
2009-Jul-15, 09:28 AM
If the galaxy was sporting a stylish goatee, that would be definitive.

Funny. Not helpful, but funny. :surprised

Rob

antoniseb
2009-Jul-15, 10:00 AM
--- What would an astronomer on Earth expect to see, looking at this distant galaxy, to give them definitive proof that this galaxy was made up of anti-matter and not normal matter?

This is the key question. Since galaxies are spewing out protons, electrons, and other ionized atoms from Supernova, and these are going into the intergalactic medium, there will be places in which there will be boundaries where matter IGM meets antimatter IGM, giving off 511KeV gamma rays and many gammas in the hundreds of MeV range.

If there were any isolated anti-matter galaxies that were part of an otherwise matter cluster, eventually there would be a merger, and that could be spectacular.

It's not clear if the intensity of the first situation would be visible (but a back of the envelope calculation (which I haven't done here) should tell us. The second one would be quite obvious, and isn't visible anywhere, so must not exist.

robross
2009-Jul-15, 05:51 PM
This is the key question. Since galaxies are spewing out protons, electrons, and other ionized atoms from Supernova, and these are going into the intergalactic medium, there will be places in which there will be boundaries where matter IGM meets antimatter IGM, giving off 511KeV gamma rays and many gammas in the hundreds of MeV range.

If there were any isolated anti-matter galaxies that were part of an otherwise matter cluster, eventually there would be a merger, and that could be spectacular.

It's not clear if the intensity of the first situation would be visible (but a back of the envelope calculation (which I haven't done here) should tell us. The second one would be quite obvious, and isn't visible anywhere, so must not exist.

Sorry, you missed the point of my question. Let's increase the structure size of the example to anti-matter super-cluster, gravitationally bound only with other anti-matter galaxies. The amount of normal matter in this entire supercluster would be in the same proportions as the amount of anti-matter in our local supercluster. The anti-matter supercluster is of course surrounded by voids, just like we are.

Now, taking any huge matter/anti-matter interactions off the table, I ask again.

What would an astronomer expect to see when looking at an anti-matter supercluster, that is NOT undergoing any more matter/anti-matter reactions than our own supercluster?

Rob

Amber Robot
2009-Jul-15, 06:16 PM
What would an astronomer expect to see when looking at an anti-matter supercluster, that is NOT undergoing any more matter/anti-matter reactions than our own supercluster?



Probably the best answer is that we won't know until we get our first spectrum of anti-hydrogen. I'm looking forward to that!

turban
2009-Jul-15, 08:10 PM
the most likely thing tht i have thought for years was that we dont know about them yet because they are in a different section of the universe because it is very unlikely that if there were equal amounts of matter and antimatter that only matter would surivive

GOURDHEAD
2009-Jul-16, 02:48 AM
What would an astronomer expect to see when looking at an anti-matter supercluster, that is NOT undergoing any more matter/anti-matter reactions than our own supercluster?Not being inhibited by not knowing, my guess is, except for the IGM interactions with particles from matter superclusters, since photons are their own anti-particles, the astronomer wouldn't be able to tell any difference. He should expect to see the same as if he were looking at a matter supercluster and its emitters.

robross
2009-Jul-16, 05:30 AM
Not being inhibited by not knowing, my guess is, except for the IGM interactions with particles from matter superclusters, since photons are their own anti-particles, the astronomer wouldn't be able to tell any difference. He should expect to see the same as if he were looking at a matter supercluster and its emitters.

Interesting. So then, I hypothesize that among the visible galactic superclusters in our observable field of view, about half of them are made of anti-matter. I think this is a simpler explanation than the unexplained matter asymmetry during baryogenisis.

To test this, we would need to first expand our understanding of antimatter molecules here on Earth, especially anti-hydrogen and anti-helium, and hope that we can discover something about each that gives them a way to be identified when comparing them with normal hydrogen and helium. If we can do this, we should be able to scan the observable superclusters and see if any of our observations match what we noted for anti-hydrogen and anti-helium.

Rob

antoniseb
2009-Jul-16, 08:02 AM
... To test this, we would need to first expand our understanding of antimatter molecules here on Earth, especially anti-hydrogen and anti-helium, ...

Anti-Helium will be pretty difficult to come by. You'll need to collect enough anti-Hydrogen to make fusion happen. Maybe simply observing anti-Hydrogen will be good enough.

As to the asymmetry, the same issues that lead us to think there may be supersymmetric particles lead us to think there should be an asymmetry.

trinitree88
2009-Jul-23, 03:41 PM
SNIPPET...As to the asymmetry, the same issues that lead us to think there may be supersymmetric particles lead us to think there should be an asymmetry....SNIPPET

Antoniseb. True, but after ~25 years of waiting,(and there's been plenty of energy exceeding the LHC in the ambient cosmic ray flux,) we have yet to see one of the 34 predicted particles from supersymmetry. At Fermilab and CERN sometimes a billion interactions per second, years of runs. Nothing. I'm thinking it's a dead end based on the empty data tables. pete

Jeff Root
2009-Jul-23, 04:44 PM
Robross has described the speculation I have been nurturing since the
mid-1970s. The possibility that the Universe is composed of equal amounts
of matter and antimatter, separated from each other at the time the CBR
was released and after by their mutual gravitational repulsion. I have
elsewhere mentioned four possible tests of this idea: Comparing predictions
to the power spectrum of the CMBR; gravitational lensing of antiphotons by
ordinary matter and of ordinary photons by antimatter; observing whether
antihydrogen atoms fall or rise in Earth's gravity; and an experiment similar
to the Pound-Rebka experiment using an antimatter radiation source.

Pete, you've commented some on those ideas. Any more comments?

-- Jeff, in Minneapolis

antoniseb
2009-Jul-23, 05:55 PM
....years of runs. Nothing. I'm thinking it's a dead end based on the empty data tables. pete

Note quite nothing. Just not enough results to be certain. Also, why throw in the towel now, just months before the LHC goes online?

trinitree88
2009-Jul-23, 07:35 PM
Robross has described the speculation I have been nurturing since the
mid-1970s. The possibility that the Universe is composed of equal amounts
of matter and antimatter, separated from each other at the time the CBR
was released and after by their mutual gravitational repulsion. I have
elsewhere mentioned four possible tests of this idea: Comparing predictions
to the power spectrum of the CMBR; gravitational lensing of antiphotons by
ordinary matter and of ordinary photons by antimatter; observing whether
antihydrogen atoms fall or rise in Earth's gravity; and an experiment similar
to the Pound-Rebka experiment using an antimatter radiation source.

Pete, you've commented some on those ideas. Any more comments?

-- Jeff, in Minneapolis

Jeff. I'll comment on the photons/anti-photons. The prevailing view in particle physics is that they are indistinguishable. I believe an old thread by Grey gave the correct rationale, and I'll search for it.
It will take a while before they Master a Penning trap to do some neutral atoms' physics, but I think some clever team will be up to the challenge. It may require the vacuum of the moon or better.Tracks of anti-protons exhibit identical inertial masses to protons in bubble chambers, wire chambers, cloud chambers, with regards to their curving traces, so I have no expectation that their gravitational masses ought to vary, else the principle of equivalence fails....gravitational, inertial, neutrino interactive masses.
As to the Mossbauer effect, which I have previously delineated for neutrino sea checking, it's impossible to touch an antimatter source without annihilations, and manipulating such an object without touching it will be the hardest experiment ever devised.
Hawking himself capitulated, I believe, on surmising that only the matter would escape a BH event horizon. Instead, equal amounts of matter and antimatter ought to leave randomly during Hawking radiation, such that the universe gains net energy as a BH evaporates. (The gurus will set me straight here if that's not true, and generally I stay out of GR discussions because I'm more of a particle physics guy, than a spacetime geometry guy. You really need to be a PhD to read half their stuff.)
Nevertheless, the universe continues to surprise, and since as yet you can't be proven totally absurd...hang in there hoping for the best with your slant on things. Since it's relatively easy to confine regular matter in a Penning trap, it ought to be harder to do so if you confined some near a piece of antimatter, if your repulsion holds up....but, and this is a huge "but", the electromagnetic force is ~ 40 orders of magnitude larger than the gravitational, and I don't think you'll find an experimental design ever to separate those two. It's why in E & M teaching one ignores gravity.

pete

Glom
2009-Jul-23, 08:17 PM
If there are two flavours to the universe, shouldn't we see evidence of interaction in the really, really deep field?

Jeff Root
2009-Jul-23, 09:16 PM
Pete,

Someone at CERN estimated in April that the first measurement of the
effect of Earth's gravity on antihydrogen should come circa 2015. He
says it will be less accurate than measurements using other equipment
a few years later, but I think he was talking about measuring slight
differences. Since I'm looking for an effect in the opposite direction
to the usual, even a very crude measurement will suffice to make or
break my idea. There won't be any halfway about it. I'll either be
shockingly right or boringly wrong.

I was probably all wet when I argued at Ken recently that antimatter
antigravity would leave the principle of equivalence intact. If I was
wrong about that, though, I would just change my assertion to say
that only a "minor" adjustment would be needed: Take the absolute
value before calling it an equivalence. That's a big conceptual change
of course but it would have no effect at all on general relativity.

Glom,

If that question was directed mainly at me, I'll answer it. If it was more
generally directed, I'll let someone else reply.

-- Jeff, in Minneapolis

trinitree88
2009-Jul-27, 04:45 PM
Pete,

Someone at CERN estimated in April that the first measurement of the
effect of Earth's gravity on antihydrogen should come circa 2015. He
says it will be less accurate than measurements using other equipment
a few years later, but I think he was talking about measuring slight
differences. Since I'm looking for an effect in the opposite direction
to the usual, even a very crude measurement will suffice to make or
break my idea. There won't be any halfway about it. I'll either be
shockingly right or boringly wrong.

I was probably all wet when I argued at Ken recently that antimatter
antigravity would leave the principle of equivalence intact. If I was
wrong about that, though, I would just change my assertion to say
that only a "minor" adjustment would be needed: Take the absolute
value before calling it an equivalence. That's a big conceptual change
of course but it would have no effect at all on general relativity.

Glom,

If that question was directed mainly at me, I'll answer it. If it was more
generally directed, I'll let someone else reply.

-- Jeff, in Minneapolis


Jeff. Browsing ArXiv files I saw this. I once watched a demo as optical; tweezers were used to move paramecia around under a microscope. But, note, these guys are inmproving methods to trap neutral particles with photons, since photons won't annihilate antimatter...they might hold your antihydrogen for testing? pete SEE:http://arxiv.org/PS_cache/arxiv/pdf/0907/0907.4198v1.pdf

mollwollfumble
2009-Jul-29, 06:02 AM
There was an article really quite recently, in the past couple of months, about a Chandra survey of a supercluster of galaxies looking for signs of gamma rays from matter/antimatter collisions. The survey drew a blank, which was enough to show that well over 99% of the galaxies in that supercluster were made of normal matter.

On a slightly different note, electron/positron collisions within our own Milky Way have recently been shown to be sufficient to account for the observed gamma ray emissions. Dark matter isn't necessary. Part of this study consisted of showing that antimatter generated near the heart of the Milky Way had a much longer mean free path than had previously been assumed, allowing some positrons to penetrate out into the galactic halo before being annihilated.

Drbuzz0
2009-Aug-08, 12:33 AM
All indications are that there's no significant antimatter just floating around in this region of the universe. If there were antimatter galaxies or other formations, they'd have to be sequestered very very well from regular matter. Even a small amount of standard matter like a little bit of gas would react and produce characteristic radiation energy levels. If there was more than a minute amount of this happening then we'd be able to detect it with gamma ray astronomy.

robross
2009-Aug-08, 12:39 AM
All indications are that there's no significant antimatter just floating around in this region of the universe. If there were antimatter galaxies or other formations, they'd have to be sequestered very very well from regular matter. Even a small amount of standard matter like a little bit of gas would react and produce characteristic radiation energy levels. If there was more than a minute amount of this happening then we'd be able to detect it with gamma ray astronomy.

Not if the sequestration was in the form of galactic superclusters, which are being separated from each other due to expansion and will never interact. Every other galactic supercluster could be made of matter and the remaining, anti-matter, and there would be no matter/anti-matter interactions between superclusters. Then we would not see anything strange when we looked at those antimatter superclusters. They would look just like a matter supercluster.

Rob

matt.o
2009-Aug-08, 04:07 AM
If you look at the large scale structure of the Universe, you see that the clusters and superclusters form at the intersections of filaments in a spiderweb like structure. These filaments funnel matter into the clusters and superclusters. This is a major problem for the matter/antimatter segregation you guys are pushing since there would have to be a very special distribution of matter and antimatter such that antimatter filaments feed antimatter clusters and vica-versa. Thus, I don't think this idea holds any water.

robross
2009-Aug-08, 04:38 AM
If you look at the large scale structure of the Universe, you see that the clusters and superclusters form at the intersections of filaments in a spiderweb like structure. These filaments funnel matter into the clusters and superclusters. This is a major problem for the matter/antimatter segregation you guys are pushing since there would have to be a very special distribution of matter and antimatter such that antimatter filaments feed antimatter clusters and vica-versa. Thus, I don't think this idea holds any water.

The filaments are not "feeding" anything, they're the result of the superclusters gravitationally "sucking in" the matter in its vicinity and leaving large voids. Like patterns in the sand near the beach after low tide has come. Obviously, the segregation of matter and antimatter would have had to happen in the extremely early universe, otherwise we would be able to tell.

Also, I'm not really pushing anything. I'm just pointing out that when people say that if there were large structures of antimatter in the universe we'd be able to see this and tell it was present, here's one obvious way this would be a false statement. You *could* have large structures of antimatter, that in general do not interact with matter, and there would be nothing to observationally distinguish that from an all-matter universe.

Rob

matt.o
2009-Aug-08, 05:25 AM
The filaments are not "feeding" anything, they're the result of the superclusters gravitationally "sucking in" the matter in its vicinity and leaving large voids. Like patterns in the sand near the beach after low tide has come. Obviously, the segregation of matter and antimatter would have had to happen in the extremely early universe, otherwise we would be able to tell.


The filaments collapse due to their own gravitational instability, not because of the clusters they feed (and they do feed matter onto clusters). The point is, these filaments stretch from cluster to cluster (see e.g., Figure 2 of Kevin Pimbblet's paper on detecting filaments (http://www.publish.csiro.au/?act=view_file&file_id=AS05006.pdf)) and you'd expect that if there were matter and antimatter clusters, the filaments would be feeding matter or antimatter onto them, thus we should observe lots of annihilation signatures, which we don't.



Also, I'm not really pushing anything. I'm just pointing out that when people say that if there were large structures of antimatter in the universe we'd be able to see this and tell it was present, here's one obvious way this would be a false statement. You *could* have large structures of antimatter, that in general do not interact with matter, and there would be nothing to observationally distinguish that from an all-matter universe.
Rob

And I'm pointing out that that is wrong based on what we see in the actual Universe. The large scale structure in the Universe is spiderweb-like; clusters and superclusters aren't non-interacting "island universes" sitting by themselves.

robross
2009-Aug-08, 03:49 PM
And I'm pointing out that that is wrong based on what we see in the actual Universe. The large scale structure in the Universe is spiderweb-like; clusters and superclusters aren't non-interacting "island universes" sitting by themselves.

That is not my understanding of the large scale structure with respect to gravity, in an expanding universe. In a static universe, you could say that every atom affects every other atom gravitationally, in the entire universe. But in our expanding universe you can no longer say that. Even now, the universe is divided into regions that are gravitationally bound, and those that are not, due to expansion. Those areas that are no longer gravitationally bound will never interact with each other, so they avoid the potential for matter/antimatter interactions.

Rob

matt.o
2009-Aug-08, 11:15 PM
That is not my understanding of the large scale structure with respect to gravity, in an expanding universe. In a static universe, you could say that every atom affects every other atom gravitationally, in the entire universe. But in our expanding universe you can no longer say that. Even now, the universe is divided into regions that are gravitationally bound, and those that are not, due to expansion. Those areas that are no longer gravitationally bound will never interact with each other, so they avoid the potential for matter/antimatter interactions.

Rob

But the point is that it is not divided sharply. Did you look at the image I linked to in my last post (here's another from the SDSS (http://www.sdss.org/includes/sideimages/sdss_pie2.jpg))? Did you see the filaments which connect the clusters? Do you understand that these clusters grow hierarchically, mainly through the infall of matter funneled in through the filaments (you might read Dario Fadda's paper (http://arxiv.org/abs/0711.2561) to see evidence for this and how it affects the galaxies involved)? By extension, I can't see how there would be "island universes" on the cluster scale which can be either matter or antimatter and would not produce a large amount of radiation due to annihilation.

You might also want to read Volker Springel's (http://arxiv.org/abs/astro-ph/0604561) Nature paper on the large scale structure of the Universe.

robross
2009-Aug-09, 07:47 AM
But the point is that it is not divided sharply. Did you look at the image I linked to in my last post (here's another from the SDSS (http://www.sdss.org/includes/sideimages/sdss_pie2.jpg))? Did you see the filaments which connect the clusters? Do you understand that these clusters grow hierarchically, mainly through the infall of matter funneled in through the filaments (you might read Dario Fadda's paper (http://arxiv.org/abs/0711.2561) to see evidence for this and how it affects the galaxies involved)? By extension, I can't see how there would be "island universes" on the cluster scale which can be either matter or antimatter and would not produce a large amount of radiation due to annihilation.

You might also want to read Volker Springel's (http://arxiv.org/abs/astro-ph/0604561) Nature paper on the large scale structure of the Universe.

Your point is valid. However, I still think it is simpler to think we have an equal amount of matter and antimatter in the universe. All of our understanding of particle creation tells us these quantum numbers need to be conserved, and every experiment that has tried to observe some asymmetry in matter/antimatter creation has failed to find it, except for one experiment with K mesons I believe, and even in that case the asymmetry was much too small to be helpful in solving the asymmetry problem.

Rob

matt.o
2009-Aug-09, 08:22 AM
Yes, I agree that our understanding of the baryon asymmetry will require much more work. However, there is strong observable evidence which suggests that the asymmetry is real.

cjameshuff
2009-Aug-09, 12:22 PM
Your point is valid. However, I still think it is simpler to think we have an equal amount of matter and antimatter in the universe. All of our understanding of particle creation tells us these quantum numbers need to be conserved, and every experiment that has tried to observe some asymmetry in matter/antimatter creation has failed to find it, except for one experiment with K mesons I believe, and even in that case the asymmetry was much too small to be helpful in solving the asymmetry problem.

But the asymmetry does exist, so we know the universe is not perfectly symmetrical in that way, and that those quantum numbers need not always be conserved. There seems no way for a near-equal amount of antimatter to exist in the universe without annihilations being observed, and no evidence whatsoever for large concentrations of antimatter, so it really seems the simpler explanation is that there's another mechanism that produces a similar but greater asymmetry at very high energies.