why there is more matter than antimatter...

agge
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Topic 193995

Is it possible that the reason that there is more matter than antimatter is that antimatter not only has opposite electric charge be also negative gravitational 'charge', so that early in the universe when the concentration of matter was very high, the antimatter was strongly repelled and blown away very high speeds?

ulenz
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why there is more matter than antimatter...

You should ask CERN and the scientists of LHC.....

Intel Q9300 Quadcore, 2500 Mhz, 4096 MB RAM, GeForce 9800 GT, Vista Ultimate 64-bit, Ubuntu 10.10 64 bit

tullio
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It seems that the PAMELA

It seems that the PAMELA observatory has detected a good number of positrons in space. While this seemed to confirm the existence of dark matter, a second theory now puts their emission to the magnetic fields of pulsars. I have read this in a New Scientist article but could not go further for lack of a subscription.
Tullio

agge
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RE: You should ask CERN and

Message 86841 in response to message 86839

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You should ask CERN and the scientists of LHC.....

oh, ok, do you have their number?

Simplex0
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RE: You should ask CERN and

Message 86842 in response to message 86839

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You should ask CERN and the scientists of LHC.....

Providing you don't mean the message board at LHC@home which
has the poorest support in the BOINC galaxy.

agge
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although is if antimatter had

although is if antimatter had opposite gravitational fields, i guess it would still be attracted to itself, and repelled by normal matter, so it wouldn't really explain why one dominates today...

Chipper Q
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RE: Is it possible that the

Quote:
Is it possible that the reason that there is more matter than antimatter is that antimatter not only has opposite electric charge be also negative gravitational 'charge', so that early in the universe when the concentration of matter was very high, the antimatter was strongly repelled and blown away very high speeds?


Nope, don't think so - antimatter has positive mass. For example, the positron has the same mass (and spin) as the electron. When these collide into each other, the result is positive energy. From E=mc^2, if the mass of the antiparticle was negative, then the total energy from annihilation would be zero (because m_positron + m_electron would equal zero total mass if one were negative with respect to the other, and zero times c squared is zero energy) ...

Mike Hewson
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RE: Is it possible that the

Quote:
Is it possible that the reason that there is more matter than antimatter is that antimatter not only has opposite electric charge be also negative gravitational 'charge', so that early in the universe when the concentration of matter was very high, the antimatter was strongly repelled and blown away very high speeds?


While there may be some form of matter with a negative mass value/charge, the current definition of antimatter does not include that property. The idea of antimatter arose out of solutions ( by Paul Dirac 1926 ) of quantum mechanical equations. Some solutions were the familiar particles already known, but others were a new form that would have the property of annihilating with the corresponding known particles. In a rough sense they are a 'negative' solution, although you have to be a bit careful about what you mean by that. The charge is also inverted.

So an electron with a charge that we designate as negative has the anti-particle version called the positron which is positively electrically charged. Both have positive mass ( inertial and gravitational ) and thus respond in the same way gravitationally and dynamically. A number of fine experiments have demonstrated that. A proton, with positive charge, has it's anti-proton. The neutron has it's anti-neutron. If either particle meets it's antiparticle both are replaced by energy in say photon form. So a neutron meeting an anti-neutron, both which have no electric charge, will annihilate. Mind you a proton meeting with a positron won't annihilate even though they are matter and anti-matter - they'll respond according to other characters though, so you'd expect electrical repulsion as they both have a positive electrical charge.

Perhaps a better way of viewing this is that all particles now have an extra ( quantum ) number associated with them that records whether they are matter or antimatter. Plus for matter, negative for antimatter. Note this is not a recording of electric charge. The force 'carriers' are zero on this scale, that is there is no anti-particle for a photon, say. For any system of particles the total of this number over all of them is a constant at all times. So when an electron ( +1 ) meets a positron ( -1 ) the photons ( each 0 ) are emitted during annihilation [ thus (+1) + (-1) = 0 + 0 ]. So you have a conservation or invariant principle here. Without going into deep explanations, which have some surprising convolutions, this conservation is the result of underlying symmetries. Richard Feynman characterised the anti-particle of 'X' as the particle 'X' but moving backward in time. Hmmmm .......

Well, almost symmetrical. Indeed one popular/favoured reason why matter dominates numerically over anti-matter today is some issue of symmetry 'breaking' during the early universe. This refers to single 'simple' symmetry operations breaking but not a combined group of operations called CPT - for Charge ( electric ), Parity ( mirror reflection ) and Time. To date the CPT symmetry combination is upheld by experiment, so no known exceptions. Yet. The breaking means that not all, but some, interaction situations do not uphold the conservation laws alluded to above. These have been observed at 'low' energies ( in 50's and 60's particle accelerators ) where non-equal proportions of decay products are formed - where full adherence to each symmetry separately would predict equal amounts. Like most quantum mechanical stuff, we are applying statistical arguments to groups of results and not a specific prediction of one event.

Now consider really high energies, such as the unimaginably high temperatures shortly after the Big Bang. One set of mechanisms has been applied to predict unequal decay of 'stuff' to matter/antimatter. The antimatter that is produced annihilates with an equal amount of matter for sure, but there will be matter left over. If you have more boys than girls at a dance then after all the girls have paired off with a boy each, some boys will be hanging around partner-less. We are made of those partner-less particles. You can produce antimatter these days, but only with the corresponding matter to boot ie. not in excess. Also of note here is that force particles ( say photons ) numerically outweigh matter particles by about a factor of a billion to one. Well, in the universe that we can observe/access at least. These photons are probably the products of the initial orgy of annihilation.

A quite terrific book about all of this, that I would recommend, is by Leon Lederman ( a Nobel Laureate ) called 'Symmetry and the Beautiful Universe'. It has virtually no maths in the main text, but you still have to concentrate though, as some conclusions can sneak up on you! :-)

Cheers, Mike.

( edit ) The quantum number that denotes matter/antimatter is the baryon number, where 'bary' means 'weight' or 'heavy' ie. has ( rest ) mass. I'm politely not mentioning the intermediate vector bosons, Higgs etc.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
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J.J.Goldstone in 1961 has put

J.J.Goldstone in 1961 has put forward the idea of spontaneous symmetry breaking, in which a set of equations respects a symmetry (e.g. t to -t) but the ground state of a system described by those equations does not respect it because it was arbitrarily chosen. So maybe the ground state of the universe was chosen by someone (God or the "providential authorities", as Niels Bohr used to say) as a state in which matter is more present that antimatter. But I have a question. Is dark matter made of matter or antimatter?
Tullio

Mike Hewson
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RE: J.J.Goldstone in 1961

Message 86847 in response to message 86846

Quote:
J.J.Goldstone in 1961 has put forward the idea of spontaneous symmetry breaking, in which a set of equations respects a symmetry (e.g. t to -t) but the ground state of a system described by those equations does not respect it because it was arbitrarily chosen. So maybe the ground state of the universe was chosen by someone (God or the "providential authorities", as Niels Bohr used to say) as a state in which matter is more present that antimatter. But I have a question. Is dark matter made of matter or antimatter?


Could be either, to fit the hypothesis of unseen but yet gravitationally acting material ( positive mass and attractive ). If it was antimatter it would have to be sufficiently separate from ordinary matter to diminish the hubbub we'd otherwise see as annihilation occurs. Matter/antimatter annihilation is 100% efficient for mass to energy conversion and is thus quite 'bright' when it happens. So I suppose that's also why everyone wants their warp drives powered by it, the ultimate bang for your buck! :-)

You know what I really see as weird in wording or presentation, and that is the Dark Energy business driving the universe apart. Now if any energy is equivalent to some mass then why can't I say that we have 'mass with repulsive properties' pushing stuff apart. For me at least, I have certainly lost the thread of definitions on that topic. I grant that the acceleration of cosmic expansion is probably real but I think the GR explanation ( all that minus one-third of the negative pressure stuff ) has been pushed too far. Sign a missing puzzle piece.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

agge
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thank you for your answer

Message 86848 in response to message 86847

thank you for your answer mike. I'll look into that book.

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