Conference noted::sf

    Positrons are particles with positive charge (and negative lepton
    number, if you are keeping count of lepton number), otherwise identical
    to electrons.  They can be created in the lab and have been.  When
    positrons an electrons come into contact, they cancel out in a burst
    of X-rays.
    
    This time-reversal is a theory put forward by Richard Feynmann.  He
    noticed that positrons behave like time-reversed electrons.  He also
    came up with the conceit that all electrons have the same mass (equal
    to the mass of positrons) because there is only one, weaving backward
    and forward through time.  He does not put this forward very seriously.
    I don't know that it has ever been tested, but you OUGHT to be able
    to generate an electron-positron pair out of an X-ray photon, test
    their masses, then allow them to annihilate with each other.  They
    ought to have the usual mass, even though they couldn't be part
    of this electronic time-travel tapestry.
    
    But matter as time-reversed anti-matter (or vice versa) is a valid
    model, at least to a high degree of approximation.  At least, Feynmann
    thinks so.
    
    Earl Wajenberg

    Actually, after Feynmann put forward his theory, they found an
    exception.  Neutral K-mesons (or kaons) come in matter and antimatter
    forms.  (The charges are the same but the magnetic fields and some
    other things are opposite.)  But kaons and anti-kaons don't have
    the same decay rate.  They think.  It was a kind of shaky test.
    It's the only exception I know of to the rule that you can regard
    anti-matter as time-reversed matter.
    
    Earl Wajenberg

    
    I ran into a mention of the same theory (?) a couple of weeks back
    in a book called "In Search of Schrodinger's Cat." Don't have the
    authors name offhand. Its a nonmath overview of the Copenhagen School
    of quantum mechanics. The reviews on it were good. Worth reading
    if you want a quick intro to the awe and mystery of recent QM.
    
    Ed E.

    Positrons, by the way, were the first elementary particles to have
    their existence predicted before they were discovered.  The predictor
    was P. A. M. Dirac, I think.
    
    Earl Wajenberg

    re .4:
    
    Correct. They fell out of Quantum Electrodynamics.
                                                   
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	If I piece the first few replies to this note I get the impression
that positrons have a negative decay rate, since they appear to be 
time  reversed electrons and electrons have a positive decay rate. Although
I can't see how an elementary particle can decay. But that would imply that
entropy is positive with respect to positron, but not necessarily anti-matter
in general. That means we can create a particle in the lab that violate
classical conservation{of energy. Not to mention the time implications.

	The theory about all electrons being the same one reminds me
of "temporal Fugue" in Lord Of Light. Neat concept, but it does agree
with basic fundamentals of electrons move in a conductor. If it is 1 electorn,
it would be in great demand all over the universe. Which makes me wonder
how we could ever generate electricity if same electron just hops molecules
and time.

Amr

Re .6

Positrons, like electrons, do not decay at all and so do not have a "negative 
decay rate."  The negative of a decay rate, by the way, would be a rate of 
production.

The time-reversal of elementary particles, entropy, and conservation of energy 
are three separate things.  None of them has anything directly to do with the 
others.  So, for example you cannot really speak of the entropy of a single 
particle, positron or electron.  Entropy is a property of collections, not 
single items, while the time-reversal of the electrons IS a property of single 
items.  And you can switch the time directions of both entropy and particles
without violating conservation of energy. 

Feynmann wasn't really very serious about his theory of only one electron.  
But if, for instance, the universe ends with a Big Crunch, the reverse of the 
Big Bang, and if equal amounts of matter and antimatter meet in the Big 
Crunch, there is the opportunity for The Electron to time-reverse and move 
back to the beginning of time as a positron, where it reverses to an electron, 
bouncing back and forth between the two ends of time over and over again.