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malm1987
2010-Aug-09, 07:00 PM
So, I've heard quite a lot about this the last weeks thanks to the upcomming pb-collisions at LHC later this year. And I just thought I'd run this by you, since the answers I've gotten from other sources are far from comforting.

So basically, the theory states that we might be living in something called a false vacuum (i.e. not the universal ideal state) and that a violent collision or such could cause a phase transition into another vacuum state, preferably a true vacuum. But why do some, like Wagner/Gorelik/Plaga seem to believe that LHC could cause such a transition?

I know that this has been discussed before, in my other LHC-thread, so I'm sorry that I bring it up again. But I thought the discussion might be more suited for the Q&A section.

So anyhow, wouldn't more energetic events, like GR bursts or such, be much more likelly to cause a phase transition?

And one other thing I thought about, that I haven't seen discussed elsewhere. Is there any possibility that vacuum bubbles of any kind could be created without causing a propagation of the "inside" vacuum? Kind of like the BEC which is harmless in the unstable configuration but would be quite the opposite if stable...

Finally, and this might be a really stupid question, but what happens to the particles after a collision? I mean, wouldn't excess particles pose a danger or at the very least alter the outcome of the oncomming collisions?

trinitree88
2010-Aug-09, 07:23 PM
So, I've heard quite a lot about this the last weeks thanks to the upcomming pb-collisions at LHC later this year. And I just thought I'd run this by you, since the answers I've gotten from other sources are far from comforting.

So basically, the theory states that we might be living in something called a false vacuum (i.e. not the universal ideal state) and that a violent collision or such could cause a phase transition into another vacuum state, preferably a true vacuum. But why do some, like Wagner/Gorelik/Plaga seem to believe that LHC could cause such a transition?

I know that this has been discussed before, in my other LHC-thread, so I'm sorry that I bring it up again. But I thought the discussion might be more suited for the Q&A section.

So anyhow, wouldn't more energetic events, like GR bursts or such, be much more likelly to cause a phase transition?

And one other thing I thought about, that I haven't seen discussed elsewhere. Is there any possibility that vacuum bubbles of any kind could be created without causing a propagation of the "inside" vacuum? Kind of like the BEC which is harmless in the unstable configuration but would be quite the opposite if stable...

Finally, and this might be a really stupid question, but what happens to the particles after a collision? I mean, wouldn't excess particles pose a danger or at the very least alter the outcome of the oncomming collisions?

malm1987 1.First, there is no experimental evidence that we live in anything other than Minkowski spacetime with 4 dimensions x,y,z and time.
2. Wagner/Gorelik/Plaga have no experimental basis upon which to base their claims but like all of us are free to try to speculate on what might be. Try it yourself.
3. Cosmic rays reach ultrahigh energies never to be seen in the LHC and have never done anything beyond the Standard Model.
4. Good Question, not stupid...stupid is not questioning things. When they collide things at the LHC the circular ring where the energy is slowly ramped up passes under a powerful magnet used in a burst to "kick" them out of the synchrotron , to an interaction zone, where detectors of various designs are prearranged. Jets are made and algorithms sort out events that are specifically looked for by momentum and energy. Then the beam hits a large absorbing mass, like graphite/concrete/dirt/iron....called a beam "dump" . Pretty standard configuration generally for an accelerator. The neutrinos/antineutrinos and muons/antimuons go quite a ways beyond most "dumps" as they interact less strongly than most of the jets. pete

malm1987
2010-Aug-10, 12:59 AM
malm1987 1.First, there is no experimental evidence that we live in anything other than Minkowski spacetime with 4 dimensions x,y,z and time.
2. Wagner/Gorelik/Plaga have no experimental basis upon which to base their claims but like all of us are free to try to speculate on what might be. Try it yourself.
3. Cosmic rays reach ultrahigh energies never to be seen in the LHC and have never done anything beyond the Standard Model.
4. Good Question, not stupid...stupid is not questioning things. When they collide things at the LHC the circular ring where the energy is slowly ramped up passes under a powerful magnet used in a burst to "kick" them out of the synchrotron , to an interaction zone, where detectors of various designs are prearranged. Jets are made and algorithms sort out events that are specifically looked for by momentum and energy. Then the beam hits a large absorbing mass, like graphite/concrete/dirt/iron....called a beam "dump" . Pretty standard configuration generally for an accelerator. The neutrinos/antineutrinos and muons/antimuons go quite a ways beyond most "dumps" as they interact less strongly than most of the jets. pete

Thank you very much for taking the time to explain this stuff to me, sometimes it gets confusing to say the least=)

However, I found this article regarding vacuum bubbles: http://iopscience.iop.org/1126-6708/2009/11/016. To me it looks like as if they are discussing the creation and interactions of vacuum bubbles, but perhaps I'm wrong (most likelly is)? Also, is it the general standpoint of the scientific community that the LSAG report is conclusive or has there been other concerns (like that LHC-concern stuff http://lhc-concern.info/wp-content/uploads/2009/09/brief_info_cern_lhc_critique_3909.pdf)

I have to say that I don't agree with the claims made by LHC-critique (isn't that Wagners group by the way?), but they do seem to have a point regarding the credibility of the comparison with CR collisions. CR collisions can't possibly be exactly the same as LHC collisions, could they? Isn't heavy ion collisions a rather rare event for example?

Basically, what I'm getting at is: could the frequency/luminousity mess up the comparison to CR and invalidate to CR arguements in the LSAG report?

And finally, is there a reason as to why vacuum metastability disaster events are so poorly discussed in the LSAG-report? The only thing that is mentioned is the same CR analogy as everywhere else in the report, but what if by some off chance the CR line of reasoning isn't valid? I assume there is quite a lot theoretical studies behind the report as well as the more empirical ditos, or do they rely solely on the empirical evidence from CR collisions?

Please observe that I'm not saying that the CR analogy isn't valid, I am certain that it is. But I can't help but to wonder how the report (LSAG) would be affected if the analogy wasn't valid=)

malm1987
2010-Aug-10, 10:29 PM
Any comments on the credibility of the articles would be deeply apreciated=) Is there any truth whatsoever to the discussion regarding the credibility of the CR comparison?

Shaula
2010-Aug-10, 11:57 PM
I think the LHC concern site has little or no credability. I spent some time on the forum there and found it very frustrating. They knew it was going to end the world and no amount of physics could convince the average member that it wasn't a vast gamble made by mad scentists.

In collisions it is the energy that is important (especially for vacuum bubbles). There are loads more energetic events going on all the time in the universe than we will ever make. I cannot say what will happen for sure, no one can. Otherwise why would we be doing the experiment? But most the peer reviewed, accepted theoretical studies I have seen/heard of say it is going to be fine. The ones that don't seem to be based on fringe physics, unknown physics or non-mainstream physics.

Edit: the reason I didn't say anything before is that I am not an expert on this at all. I would prefer than you get an expert opinion as a reply - maybe one of them will reply just to shoot down my naive response!

Nereid
2010-Aug-11, 09:58 AM
malm1987 1.First, there is no experimental evidence that we live in anything other than Minkowski spacetime with 4 dimensions x,y,z and time.
2. Wagner/Gorelik/Plaga have no experimental basis upon which to base their claims but like all of us are free to try to speculate on what might be. Try it yourself.
3. Cosmic rays reach ultrahigh energies never to be seen in the LHC and have never done anything beyond the Standard Model.
4. Good Question, not stupid...stupid is not questioning things. When they collide things at the LHC the circular ring where the energy is slowly ramped up passes under a powerful magnet used in a burst to "kick" them out of the synchrotron , to an interaction zone, where detectors of various designs are prearranged. Jets are made and algorithms sort out events that are specifically looked for by momentum and energy. Then the beam hits a large absorbing mass, like graphite/concrete/dirt/iron....called a beam "dump" . Pretty standard configuration generally for an accelerator. The neutrinos/antineutrinos and muons/antimuons go quite a ways beyond most "dumps" as they interact less strongly than most of the jets. peteThank you very much for taking the time to explain this stuff to me, sometimes it gets confusing to say the least=)

However, I found this article regarding vacuum bubbles: http://iopscience.iop.org/1126-6708/2009/11/016. To me it looks like as if they are discussing the creation and interactions of vacuum bubbles, but perhaps I'm wrong (most likelly is)? Also, is it the general standpoint of the scientific community that the LSAG report is conclusive or has there been other concerns (like that LHC-concern stuff http://lhc-concern.info/wp-content/uploads/2009/09/brief_info_cern_lhc_critique_3909.pdf)

I have to say that I don't agree with the claims made by LHC-critique (isn't that Wagners group by the way?), but they do seem to have a point regarding the credibility of the comparison with CR collisions. CR collisions can't possibly be exactly the same as LHC collisions, could they? Isn't heavy ion collisions a rather rare event for example?

Basically, what I'm getting at is: could the frequency/luminousity mess up the comparison to CR and invalidate to CR arguements in the LSAG report?

And finally, is there a reason as to why vacuum metastability disaster events are so poorly discussed in the LSAG-report? The only thing that is mentioned is the same CR analogy as everywhere else in the report, but what if by some off chance the CR line of reasoning isn't valid? I assume there is quite a lot theoretical studies behind the report as well as the more empirical ditos, or do they rely solely on the empirical evidence from CR collisions?

Please observe that I'm not saying that the CR analogy isn't valid, I am certain that it is. But I can't help but to wonder how the report (LSAG) would be affected if the analogy wasn't valid=)
Taking just a few parts of this post.

CR collisions can't possibly be exactly the same as LHC collisions, could they?

That depends on what you mean by "exactly the same"! :razz:

In one sense, of course they are not - they do not occur in carefully constructed underground chambers, inside pipes.

Isn't heavy ion collisions a rather rare event for example?

It depends on what you mean by "heavy ion collisions" and "a rather rare event".

As you now known (I hope), CRs contain "heavy ions", and they collide with the nuclei of oxygen and nitrogen (and other elements) in the Earth's upper atmosphere. These collisions happen extremely frequently, when you consider the whole of the Earth, and even if you consider just a specific energy range, comparable to that which the LHC may one day reach.

could the frequency/luminousity mess up the comparison to CR and invalidate to CR arguements in the LSAG report?

Of course it could ... and you could, one night, be teleported to the Moon, by quantum tunnelling! The only thing anyone can do is present an objective assessment of risk, based on the collective results of all experiments and observations done to date, plus application of the best theories we have, to date.

Now if anyone has a *specific* way that "the frequency/luminousity mess up the comparison to CR and invalidate to CR arguements in the LSAG report", by all means let's hear it!

what if by some off chance the CR line of reasoning isn't valid?

See above.

But I can't help but to wonder how the report (LSAG) would be affected if the analogy wasn't valid

The only way that could be answered would be with some *specifics* concerning the invalidity of the analogy in hand ...

malm1987
2010-Aug-11, 04:36 PM
Thank you Shaula, I think we are on the same page when it comes to LHC-concern/LHC-critique and so forth. I know that most people on this particular forum think of me as someone who aren't going to let go off the subject. That isn't exatly true, even if it comes somewhat close to the truth=)

I simply want to know why people seem to fear the heavy ion collisions (pb-pb) so much, and if there is any basis for theirs and mine fear? I know that people talk about the energies achieved at pb collisions being higher per nuclei then other collisions could ever achieve. Actually I think it was something like 550+Tev/nuclei, which sounds quite much to be honest.

Furthermore I would really like to know what people make of that iopscience article that i linked. Did they forsee a vacuum bubble production at LHC in regards to the upcomming pb-collisions?

malm1987
2010-Aug-11, 04:46 PM
Thank you too for the reply Nereid. I know now, thanks to the links you provided in the other thread, that heavy ion collisions do indeed frequently occur in nature as well. However, I haven't found anything that corresponds to the pb 208-collisions at CERN (pb 208 being the last stable isotope). Is there, or is there not an increased risk with pb collisions compared to Au or Fe collisions? As far as I can see I can't find no reason as to why there should be an increased risk of vacuum bubbles being created in these collisions, but some people still claim that it somehow should be more dangerous (perhaps since these collisions are rare).

But that doesn't make sense, isn't vacuum bubbles supposed to be created at immense energies at center mass of collisions? If so, why would the form of particle matter? And why doesn't GR bursts cause these bubbles to apear? Surely the energies when they hit matter must be higher than collisions at LHC?

And finally, is there anyone who know why LSAG doesn't adress the vacuum metastability disaster event more thouroghly? Far-fetched or poor research from their side?

Shaula
2010-Aug-11, 05:27 PM
I think the reason vacuum disasters are not addressed is simply because, as you have said, it is purely the energy of the event that matters. Higher energy event occur all over the universe and it is still here. Nothing special about what collides, generally. Just the energy.

Lead lead is not instrinsically worse than gold oxygen or anything else. The reason they harp on about it is the mini black hole thing. They claim that if the particles are mismatched in energy (ion-target collisions) then the BH will be moving and so whip through the planet and safely into space. Whereas if it is not moving much due to like-like collisions then it can be dragged down to the Earth's core where all these BHs can coalesce and eat us from within. Which is ignoring the way BHs work and the likely stability of the smallest ones.

Sorry - cannot comment on the article. For the next month I am stuck on a weedy wireless pipe that means a 4MB document would take an hour to download. Perils of travel, eh?!

trinitree88
2010-Aug-11, 06:47 PM
malm. Let me try an historical perspective here. Accelerators fall in two general types: linear and cyclotrons. The advantage of the cyclotron is that the particles in the beam can be boosted by RF frequencies, causing them to go faster towards the outer ring wall. Then the field strength of the confining/steering magnets is increased to bring them back to center. The process is repeated, electronically with computer adjustments to maximize the effect.
So, why can't we reach infinite energy this way? For one thing, the particles, traveling at relativistic speeds are bound by Einstein's Special Relativistic effects....their inertia/mass increases, and it becomes increasingly difficult to accelerate them. More so, the "bending" of their paths causes them to radiate energy away,which is lost. This is referred to as "Bremstrahlung losses"...braking radiation, in which you the race car driver step on the gas while I the passenger step on the brakes. There's a limit here. Less proportional losses for protons, than electrons...hence Fermilab, CERN..etc.
Now, if you use a straight line accelerator...LINAC...you avoid the Bremstrahlung, but don't have the advantage of the multiple passes to ramp energy. Later designs used a little of each with a recirculator ring before injection (Bates, etc).
After the initial designs, as theory advanced, it became obvious that the proton was not a solid particle, but a bag containing quarks and gluons, and that when you smashed them together with other nuclei, you get hot quark soup....jets with gluons, pions, baryons, hyperons, gamma rays (but no free quarks). So the increased energy is distributed over a large collection of particles....
The same issue is not quite the same when you collide electron/positron. Having no interior structure (they are pointllike in nature),all the energy turns into a photon that can then create a particle/antiparticle pair.....not distributed over a quark/gluon bag.and an antiquark/antigluon bag.
Cosmic rays , though mostly H and He, and likely products of Sne, can be any nucleus, though mostly light ones. In space, supernovae shock fronts should be rife with black holes according to many alarmists, but observational astronomy says....they're not.:naughty::dance:

so, bring on the LHC pete

malm1987
2010-Aug-12, 04:22 PM
I think the reason vacuum disasters are not addressed is simply because, as you have said, it is purely the energy of the event that matters. Higher energy event occur all over the universe and it is still here. Nothing special about what collides, generally. Just the energy.

Lead lead is not instrinsically worse than gold oxygen or anything else. The reason they harp on about it is the mini black hole thing. They claim that if the particles are mismatched in energy (ion-target collisions) then the BH will be moving and so whip through the planet and safely into space. Whereas if it is not moving much due to like-like collisions then it can be dragged down to the Earth's core where all these BHs can coalesce and eat us from within. Which is ignoring the way BHs work and the likely stability of the smallest ones.

Sorry - cannot comment on the article. For the next month I am stuck on a weedy wireless pipe that means a 4MB document would take an hour to download. Perils of travel, eh?!

Thank you for clarifying that, I was under the impression that Pb would mean an increased risk (think Wagner claimed so before) and it's nice to know that it wasn't the case. No worries regarding the article, I think it was purely theoretical and hadn't much to do with reality anyway.

Just one thing though, when they created quark gluon plasma at BNL previously didn't that go against the standard model of physics? If so, isn't more deviating things possible when they increase the beam energies at LHC? I don't know if I understood it correctly but isn't it possible that they would go beyond the plasmatic version and see a transgression from the semi-liquid plasma to a pure gas form?

Nereid
2010-Aug-12, 05:12 PM
Thank you too for the reply Nereid. I know now, thanks to the links you provided in the other thread, that heavy ion collisions do indeed frequently occur in nature as well. However, I haven't found anything that corresponds to the pb 208-collisions at CERN (pb 208 being the last stable isotope). Is there, or is there not an increased risk with pb collisions compared to Au or Fe collisions? As far as I can see I can't find no reason as to why there should be an increased risk of vacuum bubbles being created in these collisions, but some people still claim that it somehow should be more dangerous (perhaps since these collisions are rare).

But that doesn't make sense, isn't vacuum bubbles supposed to be created at immense energies at center mass of collisions? If so, why would the form of particle matter? And why doesn't GR bursts cause these bubbles to apear? Surely the energies when they hit matter must be higher than collisions at LHC?

And finally, is there anyone who know why LSAG doesn't adress the vacuum metastability disaster event more thouroghly? Far-fetched or poor research from their side?
Would you like to work with me, and other BAUTians, on making some bounded estimates of 208Pb - 208Pb collision rates, within a particular energy range, where one nucleus is a CR, and the other in an atom either in the atmosphere of the Earth or the surface of the Moon or Mercury?

Alternatively, we could consider such a CR collision with an atom in the Sun's corona, or photosphere.

Shaula
2010-Aug-12, 08:40 PM
Just one thing though, when they created quark gluon plasma at BNL previously didn't that go against the standard model of physics? If so, isn't more deviating things possible when they increase the beam energies at LHC? I don't know if I understood it correctly but isn't it possible that they would go beyond the plasmatic version and see a transgression from the semi-liquid plasma to a pure gas form?
Not that I know of. I thought that the results were pretty close to what was expected. They were certainly modelled well by a standard lattice QCD model. The issue was that there were two possibilities allowed for the plasma interaction strength. An asumption was made as to which would dominate near the transition point - this assumption was wrong IIRC. But the point is both were predicted by QCD.

Pure gas plasma of quarks/gluons strikes me as unlikely. You'd possibly need a low density for that as the requirement for it to be gas like is that the particles weakly or rarely interact. And would it matter? New state of matter = good. New physics = good. As has been said if we can make these things then they have been made elsewhere before now. The universe is still here. The beam energy is small compared to stuff the universe does daily and we've seen no evidence for a new for of matter that destroys all other forms of matter, vacuum bubbles bursting or ravenous micro black holes that gang up to mug stars.

mugaliens
2010-Aug-13, 12:57 AM
Cosmic rays , though mostly H and He, and likely products of Sne, can be any nucleus, though mostly light ones. In space, supernovae shock fronts should be rife with black holes according to many alarmists, but observational astronomy says....they're not.:naughty::dance:

so, bring on the LHC pete

Are you sure they're not simply created then destroyed via evaporation? A black hole massing half a million pounds would evaporate in about a second. Such evaporation would hardly be noticed among the massive release in a supernova.

malm1987
2010-Aug-14, 08:33 PM
Would you like to work with me, and other BAUTians, on making some bounded estimates of 208Pb - 208Pb collision rates, within a particular energy range, where one nucleus is a CR, and the other in an atom either in the atmosphere of the Earth or the surface of the Moon or Mercury?

Alternatively, we could consider such a CR collision with an atom in the Sun's corona, or photosphere.

Sorry that I haven't answered earlier, but I would really like to work with you guys. Although I doubt I will be of much use=)

How are you guys going to approach the different energy ranges and what statistics are you going to work with?

malm1987
2010-Aug-14, 09:21 PM
Not that I know of. I thought that the results were pretty close to what was expected. They were certainly modelled well by a standard lattice QCD model. The issue was that there were two possibilities allowed for the plasma interaction strength. An asumption was made as to which would dominate near the transition point - this assumption was wrong IIRC. But the point is both were predicted by QCD.

Pure gas plasma of quarks/gluons strikes me as unlikely. You'd possibly need a low density for that as the requirement for it to be gas like is that the particles weakly or rarely interact. And would it matter? New state of matter = good. New physics = good. As has been said if we can make these things then they have been made elsewhere before now. The universe is still here. The beam energy is small compared to stuff the universe does daily and we've seen no evidence for a new for of matter that destroys all other forms of matter, vacuum bubbles bursting or ravenous micro black holes that gang up to mug stars.

My apologies, I seem to have mixed up some terms (yet again). I was under the impression that the QGP was a step away from the standard model. Furthermore, I do agree with you that the Universe is more then exciting enough without vacuum bubbles having to be created on a terrestrial level.

Do you happen to know what scientists at CERN are hoping to find out when they achieve a beam energy of aprox. 2.80Tev? I'm assuming they hope to recreate QGP, perhaps at higher beam energis too? Or does ALICE have another mission objective? I heard from LSAG that they are going to start at 400Gev and work their way up to (hopefully) 2.80Tev. Are they doing that just so they can cover the different energy spectrums and thus eliminate the potential overlook of some phenomenas that are "energy specific" (i.e. only found at a certain energy frequency)?

At the homepage of ALICE they state that they are going to try and find out if Quarks inside of Protons/Neutrons can be freed. Isn't that what happens when QGP is created? Or is that a completelly different process?

Nereid
2010-Aug-14, 09:50 PM
Would you like to work with me, and other BAUTians, on making some bounded estimates of 208Pb - 208Pb collision rates, within a particular energy range, where one nucleus is a CR, and the other in an atom either in the atmosphere of the Earth or the surface of the Moon or Mercury?

Alternatively, we could consider such a CR collision with an atom in the Sun's corona, or photosphere.Sorry that I haven't answered earlier, but I would really like to work with you guys. Although I doubt I will be of much use=)

How are you guys going to approach the different energy ranges and what statistics are you going to work with?
Actually, you are going be of great help, and deeply involved! :)

Let's start with some easy things:

1) what, to within a factor of ~3, is the surface area of the Earth, at the height in its atmosphere where CRs likely first collide?
2) what, to the same degree of accuracy, is the surface area of the Moon?
3) what, to the same degree of accuracy, is the surface area of the Mercury?

Do you think you could take a stab at working these three things out?

malm1987
2010-Aug-14, 11:17 PM
Actually, you are going be of great help, and deeply involved! :)

Let's start with some easy things:

1) what, to within a factor of ~3, is the surface area of the Earth, at the height in its atmosphere where CRs likely first collide?
2) what, to the same degree of accuracy, is the surface area of the Moon?
3) what, to the same degree of accuracy, is the surface area of the Mercury?

Do you think you could take a stab at working these three things out?

Absolutelly, although I didn't really get the first one. What part of the atmosphere are you looking for?

For the others:

1) Surface area of Earth ~ 510,072,000 km˛
2) Surface area of Moon ~ 3.793 × 10^7km˛ (37,930,000km˛)
3) Surface area of Mercury ~ 7.48 × 10^7 km˛ (74,800,000km˛)

Nereid
2010-Aug-14, 11:33 PM
Absolutelly, although I didn't really get the first one. What part of the atmosphere are you looking for?

For the others:

1) Surface area of Earth ~ 510,072,000 km˛
2) Surface area of Moon ~ 3.793 × 10^7km˛ (37,930,000km˛)
3) Surface area of Mercury ~ 7.48 × 10^7 km˛ (74,800,000km˛)
OK, good (I'll do my own calculations later).

The idea here is that we know CRs collide ... but with what? In the case of the Moon and Mercury, the nuclei of atoms in the rocks on their surfaces; in the case of the Earth it's atomic nuclei - mostly in molecules of nitrogen and oxygen - high in the Earth's atmosphere. So in this case, the "surface area" we need to estimate is not that of the 'sea level' surface of the Earth, but some dozens, or even hundreds, of km above that.

Next: what is the relative abundance of lead (Pb) in Moon rocks? In Mercury rocks?

Also: how to estimate the number of lead nuclei in the Earth's atmosphere, per unit volume, at heights where CRs collide?

No need to have an answer, just some ideas on how to work out what the answer might be (including likely ranges, since a single number won't do).

Shaula
2010-Aug-15, 10:08 AM
Do you happen to know what scientists at CERN are hoping to find out when they achieve a beam energy of aprox. 2.80Tev?
They want to find Higgs and then break the Standard Model! Well, maybe not break but certainly find its limits. The whole point of higher and higher energies is that they unlock new physics. QGP will be involved but so will other, hopefully new, effects.

The ramp up is basically because higher energy collisions tend to be very messy - we need to scale up, checking the predictions as we go so that we can be sure when things change. No point suddenly leaping up to TeV and finding you cannot interpret your data! Plus it is better to run in the machine in stages. Higher beam energies mean you are more likely to damage the machine if someone forgot to nail a panel on properly.

QGP is a soup of semi-free quarks and gluons - safe to say that we need to study and understand this better. Depends what they mean by a free quark - do they mean one extracted from a QGP? No idea.

malm1987
2010-Aug-15, 01:04 PM
OK, good (I'll do my own calculations later).

The idea here is that we know CRs collide ... but with what? In the case of the Moon and Mercury, the nuclei of atoms in the rocks on their surfaces; in the case of the Earth it's atomic nuclei - mostly in molecules of nitrogen and oxygen - high in the Earth's atmosphere. So in this case, the "surface area" we need to estimate is not that of the 'sea level' surface of the Earth, but some dozens, or even hundreds, of km above that.

Next: what is the relative abundance of lead (Pb) in Moon rocks? In Mercury rocks?

Also: how to estimate the number of lead nuclei in the Earth's atmosphere, per unit volume, at heights where CRs collide?

No need to have an answer, just some ideas on how to work out what the answer might be (including likely ranges, since a single number won't do).

I'll try to get an estimate on the Mesosphere and then get on with the others. Meanwhile, could you take a look at something for me? I've looked at the LSAG report regarding vacuum decay and they simply refers to the RHIC safety report regarding the meassurment of iron nuclei in CR. They give an upper estimate of 2Tev/nucleons for Fe and a lower estimate of 100Gev (COM), and I can't find out how LSAG arrive to the conclusion that CR consisting of heavy ions reach far greater energies than anything achieved at the LHC? Here's a quote from Review of speculative disaster at RHIC:

"For heavy ions, Hut and Rees derived an estimate of the number of cosmic ray collisions in our past light cone. We have updated their result in eq. (7), and normalized
it so that the coefficient 10^47 equals the number of iron-iron collisions at a center of mass energy exceeding 100 GeV/nucleon. The abundance of iron in cosmic rays
has now been measured up to energies of order 2 TeV/nucleon [9] and agrees with the estimate used by Hut and Rees. This result translates into a bound of 2×10−36 on, p,
the probability that (in this case) an iron-iron collision at RHIC energies would trigger a transition to a different vacuum state. While we do not have direct measurements
of the fractional abundance of elements heavier than iron in cosmic rays of energy of order 100 GeV/nucleon, we do have good measurements at lower energies, where
they track quite well with the abundances measured on earth and in the solar system. For “gold” (defined as Z > 70) at lower energies ��(Au)/��(Fe) ≈ 10−5, leading to a
bound, p < 2×10−26 on the probability that a gold-gold collision at RHIC would lead to a vacuum transition."

Is the upper bound really as low as 2Tev/nucleon for Fe, and if so, how can they be sure that energies at LHC is safe? Isn't the COM about 2.80TeV or 574TeV/nucleon? That seems like a lot higher energies than what the RHIC report deems as safe, or am I missing something here?

Shaula
2010-Aug-15, 02:41 PM
It is more likely that because the heavy ions and energetic cosmic rays are much rarer (so one that is both is rare squared) they have not been able to get a good number of the flux of these particles. So they will probably have measured the fluxes of smaller and less energetic events and the plug these numbers into their models or extrapolations from longer term averages. For example the 1 TeV cosmic rays hit at a rate of a few a month IIRC (order of magnitude). Nuclei heavier than iron pop up as less than one percent of rays. So you'd either have to mobile a lot of telescopes or wait a long time to get a decent sample.

BTW for an article on the ultrahigh energy ones see here (http://www.nature.com/news/2010/100222/full/4631011a.html)

malm1987
2010-Aug-17, 06:31 PM
It is more likely that because the heavy ions and energetic cosmic rays are much rarer (so one that is both is rare squared) they have not been able to get a good number of the flux of these particles. So they will probably have measured the fluxes of smaller and less energetic events and the plug these numbers into their models or extrapolations from longer term averages. For example the 1 TeV cosmic rays hit at a rate of a few a month IIRC (order of magnitude). Nuclei heavier than iron pop up as less than one percent of rays. So you'd either have to mobile a lot of telescopes or wait a long time to get a decent sample.

BTW for an article on the ultrahigh energy ones see here (http://www.nature.com/news/2010/100222/full/4631011a.html)

That was kind of relieving to know, the ultrahigh energy part that is=) But this whole vacuum metastability disaster event, isn't it just a theory without any basis in reality? I mean, if vacuum bubbles could form in collisions wouldn't the COM acheived be the vital aspect of the possible disaster (i.e. higher energies=higher risk)? In that case it wouldn't matter if they collide protons or heavy ions, right?

Btw, does the fact that the energy in Pb^208 collisions reach as high as ~575TeV/nuclei play a part in the claimed risk with heavy ion collisions?

And finally, how come that we even think that we could be able to create something that the universe hasn't been able to do during it's existence?=)

Shaula
2010-Aug-17, 08:50 PM
Indeed that vacuum instability thing is pure speculation.

Since the nucei don't collide and interact like one particle I think the 575 number is meaningless. 575 TeV per nuclei is nothing like a 575 TeV collision. More like a cluster of 2 TeV events. People are scaremongering by inflating the numbers. A bit like saying that one car crash releases X joules of energy so if two streams of traffic collided the energy released would level a city...

Philosophical question - most people making that claim see science as unnatural and the universe as natural. Therefor we can make dangerous stuff Mother Nature is too wise to play around with.

malm1987
2010-Aug-17, 11:52 PM
Indeed that vacuum instability thing is pure speculation.

Since the nucei don't collide and interact like one particle I think the 575 number is meaningless. 575 TeV per nuclei is nothing like a 575 TeV collision. More like a cluster of 2 TeV events. People are scaremongering by inflating the numbers. A bit like saying that one car crash releases X joules of energy so if two streams of traffic collided the energy released would level a city...

Philosophical question - most people making that claim see science as unnatural and the universe as natural. Therefor we can make dangerous stuff Mother Nature is too wise to play around with.

So basically heavy ion collisions isn't more dangerous/likelly to produce a false vacuum decay than pure proton collisions?

I must say that I've never quite understood the claims that we could beat nature in it's own game. I mean, if whole galaxies can collide without triggering a phase transition then I think that we are going to be safe in regards to those measly energies achieved at LHC.

Shaula
2010-Aug-18, 06:12 AM
So basically heavy ion collisions isn't more dangerous/likelly to produce a false vacuum decay than pure proton collisions?
Not significantly. Because you get big messy collisions there is generally more energy in our heavy ion experiments. If you said "no more likely to cause vacuum decay than equivalent energy proton collisions" I'd agree. But since you are asking about something we have no evidence for how it works you are asking a bit of an impossible question if you want a definite answer. There is a chance they are more dangerous. There is a chance the sun will turn itself inside out and start dancing the waltz. You cannot rule anything out, just say that to the best of our knowledge the odds of the two are pretty similar.

Galactic collisions are pretty tame - gamma ray bursts, Quasars, hyernovae, merging black holes/neutron stars - those are the real powerhouses. It is true to say that we can't even imagine being able to replicate the most extreme events in this universe.

malm1987
2010-Aug-19, 01:30 AM
OK, good (I'll do my own calculations later).

The idea here is that we know CRs collide ... but with what? In the case of the Moon and Mercury, the nuclei of atoms in the rocks on their surfaces; in the case of the Earth it's atomic nuclei - mostly in molecules of nitrogen and oxygen - high in the Earth's atmosphere. So in this case, the "surface area" we need to estimate is not that of the 'sea level' surface of the Earth, but some dozens, or even hundreds, of km above that.

Next: what is the relative abundance of lead (Pb) in Moon rocks? In Mercury rocks?

Also: how to estimate the number of lead nuclei in the Earth's atmosphere, per unit volume, at heights where CRs collide?

No need to have an answer, just some ideas on how to work out what the answer might be (including likely ranges, since a single number won't do).

Sorry that I've been more or less abscent the last couple of days, school has taken pretty much all my sparetime. I think, however, that I'm beginning to grasp the different aspects of this study/research and do even think that I perhaps have found a way to estimate the number of lead nuclei in Earth's atmosphere, but let me get back tomorrow and I'll see to it that I have a draft of a formula to do the calculations. By the way, I did a really preliminary calc. on earths area at aprox. 100km and got these numbers: ~514598953,28km^2

You might want to double-check those though=)

Nereid
2010-Aug-21, 05:38 PM
Absolutelly, although I didn't really get the first one. What part of the atmosphere are you looking for?

For the others:

1) Surface area of Earth ~ 510,072,000 km˛
2) Surface area of Moon ~ 3.793 × 10^7km˛ (37,930,000km˛)
3) Surface area of Mercury ~ 7.48 × 10^7 km˛ (74,800,000km˛)
A bit late, but I get much the same numbers; for our calculations we'll need only 1, perhaps 2, significant figures.

Nereid
2010-Aug-21, 05:50 PM
Sorry that I've been more or less abscent the last couple of days, school has taken pretty much all my sparetime. I think, however, that I'm beginning to grasp the different aspects of this study/research and do even think that I perhaps have found a way to estimate the number of lead nuclei in Earth's atmosphere, but let me get back tomorrow and I'll see to it that I have a draft of a formula to do the calculations. By the way, I did a really preliminary calc. on earths area at aprox. 100km and got these numbers: ~514598953,28km^2

You might want to double-check those though=)
I didn't get quite the same number; how did you do your calculation?

Remember that we need the answer to no more than 2 significant figures!

How are you coming along with the two (three) other questions? Here they are again:

What is the relative abundance of lead (Pb) in Moon rocks? In Mercury rocks?

How to estimate the number of lead nuclei in the Earth's atmosphere, per unit volume, at heights where CRs collide?

Nereid
2010-Aug-25, 12:27 PM
While we wait for malm1987, I'll introduce the WP Abundances of the elements webpage (http://en.wikipedia.org/wiki/Abundances_of_the_elements_(data_page)).

From this we see that the molar abundance of lead, relative to Si ("Atom mole fraction relative to silicon = 1"), in the Sun (and solar system) is, according to three sources:
2 x 10^-6
3.1 x 10^-6
3.15 x 10^-6 (+/- 7.8%).

Lead (Pb) has four stable isotopes, 204Pb, 206Pb, 207Pb, and 208Pb. Of these lead-208 is the most abundant, comprising approx 50% of all lead atoms (at least here on the Earth).

malm1987
2010-Aug-25, 07:28 PM
I didn't get quite the same number; how did you do your calculation?

Remember that we need the answer to no more than 2 significant figures!

How are you coming along with the two (three) other questions? Here they are again:

What is the relative abundance of lead (Pb) in Moon rocks? In Mercury rocks?

How to estimate the number of lead nuclei in the Earth's atmosphere, per unit volume, at heights where CRs collide?

Hi Nereid

Sorry that I haven't answered the questions yet. I've frequented at the hospital the last couple of weeks and honestly hasn't been able to look further into the questions you gave me earlier. But now I should be able to invest some time in this project and hopefully I'll be able to give you some answers (or at least estimates) later tonight. How are you getting along with the research?

Nereid
2010-Aug-26, 01:58 PM
Hi Nereid

Sorry that I haven't answered the questions yet. I've frequented at the hospital the last couple of weeks and honestly hasn't been able to look further into the questions you gave me earlier. But now I should be able to invest some time in this project and hopefully I'll be able to give you some answers (or at least estimates) later tonight.
No worries, take your time.

And if you lose interest, or ability, to pursue this, please drop a note to say so.


How are you getting along with the research?
Quite well, thank you.

However, this exercise is far more about you, and helping you to develop some simple hypotheses, develop some ways to test them, and then actually doing so. The actual result, while certainly interesting (if not all that new), is less important, to me, than having you develop the skills to do some simple OOM checking on your own.

Of course, anyone else reading this thread is more than welcome to participate; this is, after all, a forum, not an exchange of private emails! :razz:

malm1987
2010-Aug-28, 11:06 PM
No worries, take your time.

And if you lose interest, or ability, to pursue this, please drop a note to say so.

However, this exercise is far more about you, and helping you to develop some simple hypotheses, develop some ways to test them, and then actually doing so. The actual result, while certainly interesting (if not all that new), is less important, to me, than having you develop the skills to do some simple OOM checking on your own.

Of course, anyone else reading this thread is more than welcome to participate; this is, after all, a forum, not an exchange of private emails! :razz:

Hi again Nereid, I really appreciate that you have tried to help me gain some fundamental understanding of how this stuff works but I must admit that I lack the time (and most of all brains) needed to address the different questions in the appropriate manner. To be honest, mu sudden interrest for this matter is a combination of fear and OCD (perhaps not that much of a surprise). I recently learned about all the claimed risks of heavy ion collisions, and since then (~2 months), I've been unable to let go of the subject.

I really hate to admit it, since I know how ridiculous it sounds, but the ALICE experiments really freak me out big time, especially the Vacuum bubble part. The worst part is that LSAG doesn't adress this matter in the most nearly as thouroughly as the MBH/Strangelet scenario, which further diminishes my chances of letting go of the subject. So, sorry that I have taken your time with this relentless nonsense.

Nereid
2010-Aug-29, 09:41 PM
Hi again Nereid, I really appreciate that you have tried to help me gain some fundamental understanding of how this stuff works but I must admit that I lack the time (and most of all brains) needed to address the different questions in the appropriate manner. To be honest, mu sudden interrest for this matter is a combination of fear and OCD (perhaps not that much of a surprise). I recently learned about all the claimed risks of heavy ion collisions, and since then (~2 months), I've been unable to let go of the subject.

I really hate to admit it, since I know how ridiculous it sounds, but the ALICE experiments really freak me out big time, especially the Vacuum bubble part. The worst part is that LSAG doesn't adress this matter in the most nearly as thouroughly as the MBH/Strangelet scenario, which further diminishes my chances of letting go of the subject. So, sorry that I have taken your time with this relentless nonsense.
No worries.

I'll write three separate posts, as follows (maybe not all today):

-> an introduction, explaining the strengths and limitations of what I'll be doing over my next several posts

-> a question to you

-> a first step in making an estimate.

Here, then, is the first post.
- - - - - - - - - - - - - INTRODUCTION - - - - - - - - - - - - -

The objective of this exercise is to estimate the frequency of collisions between 208Pb (lead-208) nuclei in (galactic) cosmic rays and lead-208 nuclei in one or more solar system objects.

A frequency can be given in a wide variety of units, but generally I am aiming to express it as an estimated number of collisions (bodyX) experiences in (time period); for example, the estimated number of lead-208 - lead-208 collisions the Sun experiences in a year.

The estimates are intended to be accurate to only an order of magnitude (OOM), or even only 2 OOM. For example, if an estimate come out as 6 (let's not worry about the units, for now), then that means the 'true' collision frequency could be anywhere between 0.6 and 60, or even between 0.06 and 600. Of course, we can discuss the implications of these estimates, wrt your fears and interests!

Actually, I aim to develop two (sets of) estimates; one for lead-208 collisions in general, and one for lead-208 collisions within a specific energy range. I will need your help in determining which energy range, or ranges, is the one(s) that you are most interested in.

Of course, this is not 'my' thread, nor 'yours'; any BAUTian may contribute, at any time (as long as it's within the BAUT rules and Q&A guidelines).

Any questions?

Nereid
2010-Aug-29, 09:59 PM
Here's the question for you, malm1987 (actually, it's two questions);

What is the energy range you are most interested in? You may express this in any way you like, as long as it is quantitative and objective. If you're not sure what the energy range you're interested in is, just say so, explain what you're looking for, and we can work together to get a concrete answer.

My second question to you: what frequency (estimated lead-208 - lead-208 collisions, within your chosen energy range) is the one that will put your mind at ease?

From your earlier posts I gather you have two concerns, vacuum instability and mini-BHs.

I'm guessing that, for the former, an estimate of one collision per the life of the solar system is good enough - had there been such a collision, in the past ~4.5 billion years, we wouldn't be here today!

For the latter, I don't know, but it's probably something similar (if a mini-BH had been created, it would have 'eaten' the solar system object by now*, and we wouldn't see it; instead, we'd see a ~planet-mass BH orbiting the Sun).

* that mini-BHs don't, or aren't expected to, behave in this way is a separate issue; your concern centres around the possibility that they might

Nereid
2010-Aug-30, 02:13 PM
The third of the promised posts; this one, a first step to making an estimate.

Let's take the Sun.

High energy cosmic rays (CRs) headed directly towards the Sun will collide with nuclei close to the photosphere, generally*.

Assume that the frequency of a CR-nucleus of type (X) collision is directly proportional to the abundance, by number, of X (X could be helium-4, or iron-56, or lead-208; i.e. a nuclide, or isotope).

Now from an earlier post of mine, in the Sun, lead has a molar abundance wrt silicon of ~2 to 3 x 10^-6. Let's be conservative and take 2 x 10^-6.

From the same source, we read that hydrogen has a molar abundance, wrt silicon, of 2.8 x 10^4. And we know that hydrogen comprises some 75% of all matter in the Sun.

That suggests that the absolute abundance of lead, in the Sun, is ~5 x 10^-11.

Questions?

* in some later posts I'll go over various caveats, etc that need to be entered, if one is interested in getting a more accurate estimate. In this case, such caveats might include the CRs that are deflected from the Sun before they collide, and what proportion of collisions are likely to take place above the photosphere.

malm1987
2010-Aug-30, 07:06 PM
Here's the question for you, malm1987 (actually, it's two questions);

What is the energy range you are most interested in? You may express this in any way you like, as long as it is quantitative and objective. If you're not sure what the energy range you're interested in is, just say so, explain what you're looking for, and we can work together to get a concrete answer.

My second question to you: what frequency (estimated lead-208 - lead-208 collisions, within your chosen energy range) is the one that will put your mind at ease?

From your earlier posts I gather you have two concerns, vacuum instability and mini-BHs.

I'm guessing that, for the former, an estimate of one collision per the life of the solar system is good enough - had there been such a collision, in the past ~4.5 billion years, we wouldn't be here today!

For the latter, I don't know, but it's probably something similar (if a mini-BH had been created, it would have 'eaten' the solar system object by now*, and we wouldn't see it; instead, we'd see a ~planet-mass BH orbiting the Sun).

* that mini-BHs don't, or aren't expected to, behave in this way is a separate issue; your concern centres around the possibility that they might

Nereid, you have no idea how much I appreciate your help. The energy ranges that I am most interrested in is 2TeV and above, any kind of heavy ion would do (lead-208 would be interresting but not a necessity).

As you wrote, just knowing that lead or other heavy ions like iron reaches 2.80TeV without causing a phase transition would be enough. I've looked at the Auger data but can't seem to find any direct meassurments of the "heavier" heavy ions, and then I saw that set of data from HiRes(?) that claimed all CR to be protons, but my understanding of it was that they were talking about lower-energy CR. Was that correct or do their data cover UHECR too?

You're equally correct regarding the frequency, just knowing that heavy ions collide at energies greater than achieved at LHC would be enough.

As for MBH's, I think I've managed to get over that (much because LSAG covers all possible scenarios quite extensivelly). Although there is one thing that I thought about. Earlier I happened to see a post made by Gorelik, were in he stated that all concerns he had might be in vain because a dangerous kind of condensate had already been created and currently grows in earths core. The post was made over at LHC-portal. As for all things Gorelik says, I know there is no reason whatsoever to believe in him but I'm still curious about this condensate. Could he mean Bose-Einstein Condensate or has he "found" yet another phenomena unknown to the rest of the scientific community?

Bottom line, the thing that scares me the most is the uncertainity regarding what could trigger a phase transition and the fact that there is close to zero papers that deal with this. Even LSAG lack information about it, but I guess that could be because this whole scenario is so incredibly far-fetched/unlikelly? Just knowing something about heavy ions reaching the same or higher energies would be enough to set my mind at ease.

Again, thank you so much for taking the time and adressing my crazy questions.

Nereid
2010-Aug-30, 07:10 PM
Nereid, you have no idea how much I appreciate your help. The energy ranges that I am most interrested in is 2TeV and above, any kind of heavy ion would do (lead-208 would be interresting but not a necessity).

As you wrote, just knowing that lead or other heavy ions like iron reaches 2.80TeV without causing a phase transition would be enough. I've looked at the Auger data but can't seem to find any direct meassurments of the "heavier" heavy ions, and then I saw that set of data from HiRes(?) that claimed all CR to be protons, but my understanding of it was that they were talking about lower-energy CR. Was that correct or do their data cover UHECR too?

You're equally correct regarding the frequency, just knowing that heavy ions collide at energies greater than achieved at LHC would be enough.

As for MBH's, I think I've managed to get over that (much because LSAG covers all possible scenarios quite extensivelly). Although there is one thing that I thought about. Earlier I happened to see a post made by Gorelik, were in he stated that all concerns he had might be in vain because a dangerous kind of condensate had already been created and currently grows in earths core. The post was made over at LHC-portal. As for all things Gorelik says, I know there is no reason whatsoever to believe in him but I'm still curious about this condensate. Could he mean Bose-Einstein Condensate or has he "found" yet another phenomena unknown to the rest of the scientific community?

Bottom line, the thing that scares me the most is the uncertainity regarding what could trigger a phase transition and the fact that there is close to zero papers that deal with this. Even LSAG lack information about it, but I guess that could be because this whole scenario is so incredibly far-fetched/unlikelly? Just knowing something about heavy ions reaching the same or higher energies would be enough to set my mind at ease.

Again, thank you so much for taking the time and adressing my crazy questions.
Thanks for this, it helps a lot.

If you have any questions about any of my other posts, which are aimed at addressing your concerns, please don't hesitate to ask them, at any time. However, the sooner the better, if only so I don't go too far on something that you think might be irrelevant, or needs further clarification.

Nereid
2010-Aug-30, 07:52 PM
The third of the promised posts; this one, a first step to making an estimate.

Let's take the Sun.

High energy cosmic rays (CRs) headed directly towards the Sun will collide with nuclei close to the photosphere, generally*.

Assume that the frequency of a CR-nucleus of type (X) collision is directly proportional to the abundance, by number, of X (X could be helium-4, or iron-56, or lead-208; i.e. a nuclide, or isotope).

Now from an earlier post of mine, in the Sun, lead has a molar abundance wrt silicon of ~2 to 3 x 10^-6. Let's be conservative and take 2 x 10^-6.

From the same source, we read that hydrogen has a molar abundance, wrt silicon, of 2.8 x 10^4. And we know that hydrogen comprises some 75% of all matter in the Sun.

That suggests that the absolute abundance of lead, in the Sun, is ~5 x 10^-11.

Questions?

* in some later posts I'll go over various caveats, etc that need to be entered, if one is interested in getting a more accurate estimate. In this case, such caveats might include the CRs that are deflected from the Sun before they collide, and what proportion of collisions are likely to take place above the photosphere.
Second step.

The 'surface area' of the Sun is ~6 x 10^18 m^2 (can you check please?)

I think the CREAM results encompass the energy range malm1987 is interested in (500-3980 GeV/nucleon).

Also, from Ahn et al. (2010) (http://adsabs.harvard.edu/abs/2010ApJ...715.1400A) - "Measurements of the Relative Abundances of High-energy Cosmic-ray Nuclei in the TeV/Nucleon Region", a reasonable first approximation to the relative abundance of heavy CR nuclei impacting the Sun is the observed solar abundance*.

Further, from the plot on this WP page (http://en.wikipedia.org/wiki/Cosmic_ray), we can take the frequency of (all) CRs in the energy range of interest to be ~1 m^-2 year^-1.

Thus lead nuclei, in this energy range, hit the Sun at a rate of ~5 x 10^-11 m^-2 year^-1.

Questions?

* there are puts and takes, of course: light nuclei are considerably over-abundant (wrt solar), due to spallation; some intermediate nuclei (e.g. Sc, Ti) are also somewhat over-abundant, for the same reason; if ~20% of CRs in this energy range originate in MSOs (massive star outflows), the relative abundances will change a bit; and so on.

malm1987
2010-Aug-30, 11:40 PM
Second step.

The 'surface area' of the Sun is ~6 x 10^18 m^2 (can you check please?)

I think the CREAM results encompass the energy range malm1987 is interested in (500-3980 GeV/nucleon).

Also, from Ahn et al. (2010) (http://adsabs.harvard.edu/abs/2010ApJ...715.1400A) - "Measurements of the Relative Abundances of High-energy Cosmic-ray Nuclei in the TeV/Nucleon Region", a reasonable first approximation to the relative abundance of heavy CR nuclei impacting the Sun is the observed solar abundance*.

Further, from the plot on this WP page (http://en.wikipedia.org/wiki/Cosmic_ray), we can take the frequency of (all) CRs in the energy range of interest to be ~1 m^-2 year^-1.

Thus lead nuclei, in this energy range, hit the Sun at a rate of ~5 x 10^-11 m^-2 year^-1.

Questions?

* there are puts and takes, of course: light nuclei are considerably over-abundant (wrt solar), due to spallation; some intermediate nuclei (e.g. Sc, Ti) are also somewhat over-abundant, for the same reason; if ~20% of CRs in this energy range originate in MSOs (massive star outflows), the relative abundances will change a bit; and so on.

The surface area seems to be correct according to Wikipedia, although they display the numbers in km^2 instead of m^2.

The CREAM data seems to be spot on, or rather, covers the entire energyspan that I'm interrested in. Might as well throw in a really stupid question here; 3980GeV/nucleon equals ~3,98TeV, right?

Once again, sorry for my stupidity here but what energy do the estimates of lead abundance in the sun correspond to?

Nereid
2010-Aug-31, 02:23 PM
The surface area seems to be correct according to Wikipedia, although they display the numbers in km^2 instead of m^2.
But I converted km^2 to m^2 correctly, didn't I?



The CREAM data seems to be spot on, or rather, covers the entire energyspan that I'm interrested in. Might as well throw in a really stupid question here; 3980GeV/nucleon equals ~3,98TeV, right?
I think so ... what do other BAUTians think?



Once again, sorry for my stupidity here but what energy do the estimates of lead abundance in the sun correspond to?
I'm afraid I don't understand your question; can you clarify please?

Lead in the Sun is no different than lead in the Earth, from the perspective of the OOM calculations I'm doing, so perhaps you could answer your own question, slightly rephrased as: "what energy do the estimates of lead abundance in the Earth correspond to?"

Suppose the molar abundance of lead, on the surface of the Earth, is the same, relative to silicon, as it is in the Sun. That means* if you pick randomly pick a lot of atoms, from the surface of the Earth, and find that there are a million silicon atoms among them, how many lead atoms would you expect to find?

* Does it? What does "molar abundance" mean?

Nereid
2010-Aug-31, 02:41 PM
Third step, checking our understanding.

If the Sun's surface - from the point of view of the CRs in our chosen energy range - has a surface area of 6 x 10^18 m^2, and if the frequency of CR collisions, in the energy range we are interested in, with the surface of the Sun, is one per square metre per year, then in one year there will be 6 x 10^18 collisions.

If there are 5 x 10^-11 lead atoms* for every atom on its surface, and if a CR collides with a nucleus randomly, and if CR-nuclei collision rates are independent of composition**, then there will be 3 x 10^8 CR-lead nucleus collisions on the Sun's surface each year.

If there are 5 x 10^-11 lead nuclei for every CR particle, in the energy range we are interested in, and if a CR collides with a nucleus randomly, and if CR-nuclei collision rates are independent of composition**, then there will be 3 x 10^8 "CR lead nuclei"-"atoms on the Sun's surface" collisions each year.

Questions?

* actually they'll be lead ions, each of which will have one or more fewer electrons than a lead atom; however, this is irrelevant to these OOM calculations, because CRs collide with lead nuclei, not the electrons in a lead ion (or atom)
** i.e. if the CR is a proton and the target is also a proton, the collision is just as likely as if the CR is a lead nucleus and the target also a lead nucleus; ditto for a CR lead nucleus/proton, and a CR proton/lead nucleus; etc. Note that this is not the case when the collider particle and target particle have energies in the range typical of nuclear interactions, such as those which take place in the Sun's core. We may explore this 'cross section' issue later.

Nereid
2010-Sep-08, 03:40 PM
Bump. malm1987 has been gone for over a week, and no one else has commented.

Looks like it might be time for me to finish my analyses?

WayneFrancis
2010-Sep-08, 04:28 PM
I think the reason vacuum disasters are not addressed is simply because, as you have said, it is purely the energy of the event that matters. Higher energy event occur all over the universe and it is still here. Nothing special about what collides, generally. Just the energy.

Lead lead is not instrinsically worse than gold oxygen or anything else. The reason they harp on about it is the mini black hole thing. They claim that if the particles are mismatched in energy (ion-target collisions) then the BH will be moving and so whip through the planet and safely into space. Whereas if it is not moving much due to like-like collisions then it can be dragged down to the Earth's core where all these BHs can coalesce and eat us from within. Which is ignoring the way BHs work and the likely stability of the smallest ones.

Sorry - cannot comment on the article. For the next month I am stuck on a weedy wireless pipe that means a 4MB document would take an hour to download. Perils of travel, eh?!

Just suggesting that anyone that is worried about a BH from 2 heavy elements then here is an assignment for you. Calculate the size of the event horizon of said BH. Then seeing said BH is probably positively charged calculate the odds of it coming into contact with more matter

I think you'll find that a BH of even something like a 6.5x10-25kg would be microscopic even in quantum terms and we are ignoring that it would, if Hawking is correct, evaporate almost immediately.

malm1987
2010-Sep-09, 06:25 PM
Bump. malm1987 has been gone for over a week, and no one else has commented.

Looks like it might be time for me to finish my analyses?

Hi again Nereid

Sorry that I haven't been around for such a long time, school just recently started and it takes up all my available time at the moment.

You converted the numbers correctly, at least as far as I can see=)

I think I follow your estimates up to the third step, but must admit that numbers isn't really my strong side. Nevertheless, I don't think I can come up with any questions as of now so feel free to finnish your analyzis if you like to:) And once again, thank you so much for taking the time to explain this to me.

Nereid
2010-Sep-10, 06:32 PM
Hi again Nereid

Sorry that I haven't been around for such a long time, school just recently started and it takes up all my available time at the moment.

You converted the numbers correctly, at least as far as I can see=)

I think I follow your estimates up to the third step, but must admit that numbers isn't really my strong side. Nevertheless, I don't think I can come up with any questions as of now so feel free to finnish your analyzis if you like to:) And once again, thank you so much for taking the time to explain this to me.
No worries.

I think I follow your estimates up to the third step, but must admit that numbers isn't really my strong side.

To be clear, you can follow the calculations in the third step? Or you cannot follow them?

Fourth step.

Start with this: 3 x 10^8 CR-lead nucleus collisions on the Sun's surface each year.

As there are 5 x 10^-11 lead nuclei for every CR particle, the number of lead-lead collisions on the Sun's surface each year will be ~1.5 x 10^-2.

Next: 3 x 10^8 "CR lead nuclei"-"atoms on the Sun's surface" collisions each year, so as there are 5 x 10^-11 lead nuclei for every atom on the Sun's surface, the number of lead-lead collisions on the Sun's surface each year will be ~1.5 x 10^-2. That's good, the estimated number is the same, by two separate methods.

Finally: 50% of lead nuclei are lead-208, so the number of lead-208/lead-208 collisions, in the energy range of interest, on the Sun's surface each year will be ~4 x 10^-3.

So, if a lead-208/lead-208 collision, in the energy range of interest, creates a vacuum bubble which destroys the universe, at the speed of light, it would have been destroyed approximately 20 times since written records have been kept by humans (~5,000 years).

Next step: how good are these estimates; specifically, could "20 per 5,000 years" be as low as (or lower than!) "1 per 5,000 years"?