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Post by Progenitor A on Nov 20, 2010 9:04:17 GMT 1
CERN has made anti-hydrogen and keeps it in bottles. I suppose that you can buy little bottles of it in the CERN Visitor Centre Shop If you are fortunate enough to have a bottle, then try this little experiment. Buy a bottle of hydrogen and pour the anti-hydrogen into it. You will be quite surprised at the result! Now it won't be long before an anti-hydrogen engine is made, with a carburetter that mixes anti and (pro?) hydrogen together in each cylinder. A nice thing about this fuel is that the waste products are clean and envirionment friendly; water and anti-water, and the other nice thing is that you can then use these two waste products in the same way to power your car.
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Post by abacus9900 on Nov 20, 2010 19:12:22 GMT 1
CERN has made anti-hydrogen and keeps it in bottles. I suppose that you can buy little bottles of it in the CERN Visitor Centre Shop If you are fortunate enough to have a bottle, then try this little experiment. Buy a bottle of hydrogen and pour the anti-hydrogen into it. You will be quite surprised at the result! Now it won't be long before an anti-hydrogen engine is made, with a carburetter that mixes anti and (pro?) hydrogen together in each cylinder. A nice thing about this fuel is that the waste products are clean and envirionment friendly; water and anti-water, and the other nice thing is that you can then use these two waste products in the same way to power your car. Matter anti-matter propulsion systems may be a thing of the future but it is the daunting engineering problems that have to be overcome before it could become a reality. Not in my lifetime I think, but who knows?
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Post by speakertoanimals on Nov 22, 2010 15:49:22 GMT 1
Just to point out, a hydrogen burning engine produces water, but burning anti-hydrogen won't produce anti-water unless you have some anti-oxygen as well. Mixing hydrogen and antihydrogen will just produce gamma rays, not water...................
And anti-hydrogen would be found to have a rather distressing effect on your carburettor........................
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Post by principled on Nov 22, 2010 17:00:27 GMT 1
STA Could you give a bit more detail on anti-matter? For example- and just as a discussion point- if we mixed anti-hydrogen and anti-oxygen and produced a drop of anti-water, what would happen if it were mixed with normal water? Are you saying gamma rays would be given off, can you explain why? I assumed that the result would be nothing. If gamma rays are given off, this would seem to suggest that there is a difference in energy levels from between "normal" and anti-matter, or am I missing something at this atomic level? I viewed anti-matter more like "anti-sound", where an out-of-phase sound of the same frequency and amplitude effectively neutralised the original sound. P
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Post by speakertoanimals on Nov 22, 2010 18:04:08 GMT 1
If matter meets anti-matter, then electrons annihilate with anti-electrons (positrons) to give gamma rays, and anti-protons annihilate with anti-protons to give more gamma rays, and anti-neutrons annihilate with neutrons to give even more gamma rays!
Its not energy levels, its just basic matter and antimatter annihilate whenever they meet.
This effect is actually used on PET scanners, which as the name suggests (Positron Emission Tomography), involves positrons. These are produced by injecting a radio-nuclide into the body that produces positrons. When these emitted positrons annhilate with electrons in the body, they produce a pair of back-to-back gamma rays, and it is these pairs of gamma rays that are detected, in order to infer the line on which the annihilation event occured, hence infer (using the results of other such events), where the radionuclide ended up. This works because the positrons are emitted with an energy such that they typically travel about 1mm before loosing enough energy to annihilate with an electron.
The images are useful since the radionuclide is usually part of a biologically-active molecule, and what clinicians are interested in is places where this becomes concentrated.
The only problem then is producing the required biologically-active molecule and incorporating the radioactive isotope required into that molecule. These radioisotopes have short half-lives (basically, decay quickly), so your production facility has to be close to your scanner, and uses a particle accelerator called a cyclotron to produce the radioisotopes, and then you need on-site chemical synthesis facilities to incorporate these into your biologically-active molecule.
This is why bottling anti-matter is so difficult -- you must keep it from contacting ordinary matter, hence the use of magnetic traps and suchlike, and why the set-up in Angels and Demons would not work.
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Post by principled on Nov 22, 2010 18:40:15 GMT 1
Thanks for that STA. A couple of other points of clarification. Does the positron exhibit the same characteristics as the electron (ie: wave/particle)?
I assume that when we bring matter and anti-matter together what is left is nothing other than the gamma rays. Correct? Does the energy the gamma rays posses, therefore, reflect the loss of the mass after the two masses combine (ie from mass "x" of the two separate masses to zero mass + gamma rays when the masses are combined/annihilated) ? I was thinking in terms of the mass/energy equivalence as per E=MC2 P
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Post by abacus9900 on Nov 22, 2010 19:27:37 GMT 1
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Post by speakertoanimals on Nov 22, 2010 21:21:11 GMT 1
The positron (which was actually predicted by Dirac when he was trying to write down a relativistic version of quantum theory for the electron), behaves just like the electron, except it has a positive charge rather than a negative one.
The gamma rays produced have same total energy as 2mc^2, where m is mass of electron (same as mass of positron).
It can go the other way as well, from gamma rays to particle-antiparticle pairs-- in the old days when they used bubble chambers at accelerators, a gamma ray entering the liquid (held just below boiling by pressure, then pressure reduced so hot enough to boil, just needed slightest perturbation to start boiling and produce bubbles, which was what the charged particles passing through did, so path of particle revealed by little trail of bubbles!) could produce an electron-positron pair. Since the detector was placed in a magnetic field, electrons would curl one way, and positrons the other, hence producing characteristic swirly pair of tracks.
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Post by principled on Nov 23, 2010 20:27:08 GMT 1
Thanks for that STA. I wasn't aware of the experiment you mentioned. Very interesting. Can you tell me what happens to the proton in an anti-matter atom? Does it change its charge? If not, then what prevents the positrons from being repelled from around the proton by their like charges with the proton? P
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Post by eamonnshute on Nov 23, 2010 20:33:46 GMT 1
An anti-matter hydrogen atom contains an anti-proton (negative charge) not a proton.
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Post by principled on Nov 23, 2010 20:47:15 GMT 1
Thanks Eamonn. That was the answer I was looking for. P
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Post by principled on Nov 24, 2010 17:10:16 GMT 1
Bearing in mind that anti-matter is a mirror image of ordinary matter, why did "ordinary" matter become dominant (or did it?) in the universe. Would a universe of anti-matter have been as stable as the matter one we have now? I ask because of the problems of keeping anti-matter as outlined previously by STA., which I assume is because we are surrounded by "normal" matter but would like that confirmed. P
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Post by eamonnshute on Nov 24, 2010 17:34:41 GMT 1
Bearing in mind that anti-matter is a mirror image of ordinary matter, why did "ordinary" matter become dominant (or did it?) in the universe. P The theory is that matter and antimatter were produced in almost identical amounts, but that there is a slight asymmetry in the laws of nature, so that for every billion particles of anti-matter there were a billion and one particles of matter. These annihilated each other to leave one particle of matter and a billion photons, which we see today.
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Post by speakertoanimals on Nov 24, 2010 18:43:43 GMT 1
The annihilation of matter with anti-matter (apart from the residual scum of matter which is all the matter we see) to photons is what produced the photons that are the cosmic microwave background. We have already detected asymmetries in the laws of nature between matter and anti-matter, but not quite in the right channel to explain why we have a matter universe -- the problem being, it is a very SMALL asymmetry, hence a delicate job of trying to get a handle on it in experiments: www.sciencedaily.com/releases/2010/08/100816095717.htm
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Post by principled on Nov 24, 2010 20:14:10 GMT 1
STA That link was spot on. I find the asymmetry to be interesting and wonder why that is. Does this suggest then that the anti-matter isn't quite a mirror image of "normal" matter? Do physicists have an explanation for this? Is it like saying (at its simplest level) that normal matter energy obeys E=mc2 and anti-matter is E=mc2- "a little bit". If so, where is this difference? Is it in the energy levels of the positrons or in the anti-proton (I assume that the neutron is identical, which could be wrong of course)? P PS: Helen, be a good girl. I've put in a good word for you, but as I note my karma is zero, I suspect I hold little influence!
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