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User: Physics+Guy

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  1. Re:This is utter BS on NASA collecting anti-matter with giant ballon · · Score: 1

    The concept of `negative energies' was invented in the 1930's when Dirac was trying to justify his equation as a representation of electrons. The Dirac equation is a replacement for the Schrodinger equation in Quantum Mechanics, and was necessary since Schrodinger's equations is not relativistically correct, nor does it take account of electron spin (which amounts to much the same thing; c.f. E. Wigner, annals of mathematics, vol 40, jan. 1939. this is really dry stuff).

    Anyway, when Dirac was first playing with his equation, he found two solutions which we now consider to be the electrons and positrons (anti-electrons) but, since he was only looking for electrons he misinterpreted the second solution as electrons with negative energies
    (he tried to make them into protons: can't blaim him for trying)

    Some time later, Feynman and Stuckelberg came along and demonstrated that the negative energy solutions that Dirac had found were really the prediction of a positive energy anti-electron. They also showed that within the framework of the equations, pushing an electron along `the wrong way' in time gave the same mathematical behaviour as a positron going forward in time.

    In The Dancing Wu Li Masters, one has a laymans approach to all that. Sadly, most of what is now known as Quantum Field Theory is not easily accessable without oodles of mathematics, and most popularizations are stuck with the ideas of the 1930's and 40's, which have evolved quite a bit by now. Dirac's equation is still very important and is used frequently by particle physicists, but its interpretation has changed.

    Suffice it to say that negative energy was an interesting idea at the time, but it didn't survive contact with the reality of particle physics for very long. For more information, i'd suggest the first chapter of David Griffiths book, Introduction to Elementary Particles.

  2. Re:"Collect" anti-matter? on NASA collecting anti-matter with giant ballon · · Score: 1

    You would put it in a magnetic bottle or accelerator ring. Antimatter (positrons, antiprotons, the pions, muons, kaons, W+ and W-, etc, ad nausium) have been in production and use in one form or another at accelerator labs here on earth for quite a while (cern, fermilab, triumf, psi, etc). It is an important tool for the study of the fundamental symmetries in nature.

    One big puzzle in astronomy/cosmology is actually why matter exists at all; why is the universe asymmetric, i.e., made up of matter and not antimatter? tough question. Finding the distribution of antimatter of cosmic origin would go a long way to solving this problem, but, since the x-ray telescopes don't see the gammas of matter-antimatter annihilation with any great frequency, it is dubious that any balloon will help much.

    An antimatter flux from the sun, however, is really interesting...