MULTIREALISTS IN EINSTEINIANA

http://www.project-syndicate.org/com...utsch2/English
David Deutsch: "What these paradoxical interpretations have in common
is that they abandon realism, the doctrine that a physical world,
existing in reality, accounts for all of our experience. Anti-realism
remains popular and appears in various guises in textbooks and popular
accounts of quantum theory. But Einstein insisted that physical
phenomena have explanations in terms of what he called "elements of
reality." Fortunately, a minority of physicists, myself included,
likewise side unequivocally with realism, by adopting Hugh Everett's
multiple-universes interpretation of quantum theory. According to this
view, no particles exist where they have insufficient energy to be; it
is simply that in some universes they have more energy than average,
and in others, less. All alleged "paradoxes" of quantum theory are
similarly resolved."

Bravo, David Deutsch! I think you are the greatest multirealist in
Einsteiniana! Now there is a paradox that your brothers Einsteinians
who are not multirealists cannot solve. According to Einstein's
special relativity, arbitrarily long objects can be trapped inside
arbitrarily short containers:

http://math.ucr.edu/home/baez/physic...barn_pole.html
"These are the props. You own a barn, 40m long, with automatic doors
at either end, that can be opened and closed simultaneously by a
switch. You also have a pole, 80m long, which of course won't fit in
the barn. Now someone takes the pole and tries to run (at nearly the
speed of light) through the barn with the pole horizontal. Special
Relativity (SR) says that a moving object is contracted in the
direction of motion: this is called the Lorentz Contraction. So, if
the pole is set in motion lengthwise, then it will contract in the
reference frame of a stationary observer.....So, as the pole passes
through the barn, there is an instant when it is completely within the
barn. At that instant, you close both doors simultaneously, with your
switch. Of course, you open them again pretty quickly, but at least
momentarily you had the contracted pole shut up in your barn. The
runner emerges from the far door unscathed.....If the doors are kept
shut the rod will obviously smash into the barn door at one end. If
the door withstands this the leading end of the rod will come to rest
in the frame of reference of the stationary observer. There can be no
such thing as a rigid rod in relativity so the trailing end will not
stop immediately and the rod will be compressed beyond the amount it
was Lorentz contracted. If it does not explode under the strain and it
is sufficiently elastic it will come to rest and start to spring back
to its natural shape but since it is too big for the barn the other
end is now going to crash into the back door and the rod will be
trapped IN A COMPRESSED STATE inside the barn."

http://www.quebecscience.qc.ca/Revolutions
Stéphane Durand: "Pour mieux comprendre le phénomène de ralentissement
du temps, il est préférable d'aborder un autre phénomène tout aussi
paradoxal: la contraction des longueurs. Car la vitesse affecte non
seulement l'écoulement du temps, mais aussi la longueur des objets.
Ainsi, une fusée en mouvement apparaît plus courte que lorsqu'elle est
au repos. Là aussi, plus la vitesse est grande, plus la contraction
est importante. Et, comme pour le temps, les effets ne deviennent
considérables qu'à des vitesses proches de celle de la lumière. Dans
la vie de tous les jours, cette contraction est imperceptible.
Cependant, si une fusée de 100 m passait devant nous à une vitesse
proche de celle de la lumière, elle pourrait sembler ne mesurer que 50
m, ou même moins. Bien sûr, la question qui vient tout de suite à
l'esprit est: «Cette contraction n'est-elle qu'une illusion?» Il
semble tout à fait incroyable que le simple mouvement puisse comprimer
un objet aussi rigide qu'une fusée. Et pourtant, la contraction est
réelle... mais SANS COMPRESSION physique de l'objet! Ainsi, une fusée
de 100 m passant à toute vitesse dans un tunnel de 60 m pourrait être
entièrement contenue dans ce tunnel pendant une fraction de seconde,
durant laquelle il serait possible de fermer des portes aux deux
bouts! La fusée est donc réellement plus courte. Pourtant, il n'y a
PAS DE COMPRESSION matérielle ou physique de l'engin."

http://www.parabola.unsw.edu.au/vol3...ol35_no1_2.pdf
Parabola Volume 35, Issue 1 (1999)
LENGTH AND RELATIVITY by John Steele
"The Pole in the Barn Paradox. Now we know about length contraction,
we can invent some amusing uses of it. Suppose you want to fit a 20m
pole into a 10m barn. If the pole were moving fast enough, then length
contraction means it would be short enough. (...) Now comes the
paradox. According to your friend who is going to slam the barn doors
shut just as the end of the pole goes in, the pole is 10m long, and
therefore it fits. However as far as you are concerned, the pole is
still 20m long but the barn is now only 5m long: length contraction
must work both ways by the first postulate. How can you fit this 20m
pole into a 5m barn? This paradox is apparently due to Wolfgang
Rindler of the University of Texas at Dallas. Of course the key to
this is relativity of simultaneity. Your friend sees the front end of
the pole hit the back wall of the barn at the same time as the doors
are closed, but you (and the pole) do not see things this way. You are
standing still and see a 5m long barn coming towards you at some
shockingly high speed. When the back of the barn hits the front of the
pole (and takes the front of the pole with it), the back end of the
pole must still be at rest. It cannot 'know' about the crash at the
front, because the shock wave travelling along the pole telling it
about the crash travels at some finite speed. The front of the barn
has only 15m to go to get to the back of the pole, but the shock wave
has to travel the whole length of the pole, namely 20m. The speed of
the barn is such that even if this shock wave travelled at the speed
of light, it would not get to the back of the pole before the front of
the barn did. Hence in both frames of reference, the pole fits inside
the barn (and will presumably shatter when the doors are closed)."

David Deutsch, Multirealists, could it be that in some universes the
long object is safely trapped inside the short container but in other
universes it cannot be trapped at all? This would be a glorious
multirealist solution to the awful paradox - brothers Einsteinians
would be grateful.

Another paradox: According to Einstein's special relativity, the
observer travelling with the rivet sees the bug squashed while the bug
sees itself alive and kicking:

http://hyperphysics.phy-astr.gsu.edu.../bugrivet.html
"The bug-rivet paradox is a variation on the twin paradox and is
similar to the pole-barn paradox.....The end of the rivet hits the
bottom of the hole before the head of the rivet hits the wall. So it
looks like the bug is squashed.....All this is nonsense from the bug's
point of view. The rivet head hits the wall when the rivet end is just
0.35 cm down in the hole! The rivet doesn't get close to the
bug....The paradox is not resolved."

I think the multirealist solution to this paradox is easier: different
observers live in different universes where different things happen.
Am I right?

Pentcho Valev