Kyu a scris:Despre ce fenomen vorbesti mai exact, te-as ruga sa dai un link ce explica un asemenea lucru. Multumesc.
din "the tao of physics":
"...The unusual aspect is connected with diagrams
containing positron lines, like the one picturing the positron-photon
scattering. The mathematical formalism of field theory
suggests that these lines can be interpreted in two ways;
either as positrons moving forwards in time, or as electrons
moving backwards in time! The interpretations are mathematically
identical; the same expression describes an antiparticle
moving from the past to the future, or a particle moving
from the future to the past. Our two diagrams can thus be
seen as picturing the same process evolving in different
directions in time. Both of them can be interpreted as the
scattering of electrons and photons, but in one process the
particles move forwards in time, in the other they move
backwards. The relativistic theory of particle interactions shows
thus a complete symmetry with regard to the direction of time.
All space-time diagrams may be read in either direction. For
every process, there is an equivalent process with the direction
of time reversed and particles replaced by antiparticles.
To see how this surprising feature of the world of subatomic
particles affects our views of space and time, consider the
process shown in the diagram below . Reading the diagram
in the conventional way, from the bottom to the top, we will
interpret it as follows: an electron (represented by a solid line)
and a photon (represented by a dashed line) approach each
other; the photon creates an electron-positron pair at point
A, the electron flying off to the right, the positron to the left;
the positron then collides with the initial electron at point
B and they annihilate each other, creating a photon in the
process which flies off to the left. Alternatively, we may also
interpret the process as the interaction of the two photons
with a single electron travelling first forwards in time, then
backwards, and then forwards again. For this interpretation,
we just follow the arrows on the electron line all the way
through; the electron travels to point B where it emits a photon
and reverses its direction to travel backwards through time to
point A; there it absorbs the initial photon, reverses its direction
again and flies off travelling forwards through time. In a way,
the second interpretation is much simpler because we just
follow the world line of one particle. On the other hand, we
notice immediately that in doing so we run into serious difficulties
of language. The electron travels
E grav daca nu ti se pare pozitiv ca omul sa se preocupe de bunastarea sa...Dar de ce sa se preocupe pentru a fi pozitiv din punctul tau de vedere? Venerarea unei fiinte non-existente pe tot parcursul vietii, pentru a ajunge dupa in raiul atat de mult dorit de unii? Aici e problema unei parti a societatii din ziua de azi.