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Language: en
how does many-worlds help us understand
our particular branch of reality so okay
that's fine and good that is everything
is splitting a we're just traveling down
a single branch of it so how does it
help us understand our little unique
branch yeah I mean that's a great
question but that's the point is that we
didn't invent many worlds cuz you
thought it was cool to have a whole
bunch of worlds right we amended it
because we were trying to account for
what we observe here in our world and
what we observe here in our world are
wavefunctions collapsing okay we do have
a position of the situation where the
electron seems to be spread out but then
when we look at it we don't see it
spread out we see it located somewhere
so what's going on that's the
measurement problem of quantum mechanics
that's how we have to face up to so many
worlds is just a proposed solution to
that problem and the answer is nothing
special is happening it's still just the
Schrodinger equation but you have a wave
function - and that's a different answer
than would be given in hidden variables
or dynamical collapse theories or
whatever so the entire point of many
worlds is to explain what we observe but
it tries to explain what we already have
observed right it's not trying to be
different from what we've observed
because that would be something other
than quantum mechanics but you know the
idea that there's worlds that we didn't
observe they keep branching off it's
kind of it is uh you know it's
stimulating to the imagination so is it
possible to hop from you mentioned the
branches are independent yes is it
possible to hop from one to the other
no it's so physical limit there's a the
theory says it's impossible there's
already a copy of you in the other world
don't worry yes leave them alone
no but there's a there's a fear of
missing out form oh yes that I feel like
immediately start to wonder if that
other copy is having more or less fun
yeah well the downside of many worlds is
that you're missing out on an enormous
and that's always what it's gonna be
like and I mean there's a certain stage
of acceptance and that yes in terms of
rewinding do you think we can
why in the system back sort of the the
nice thing about many-worlds I guess is
it really emphasizes the maybe you can
correct me but to determine it the
deterministic nature of a branch and it
feels like it could be a while back is
it is do you see is this something that
can be perfectly one that rewinded back
yeah you know if you're at a fancy
French restaurant
yeah there's a nice linen white
tablecloth and you have your glass of
Bordeaux and you knock it over and the
wine spills across the tablecloth
if the world were classical okay it
would be possible that if you just
lifted the wine glass up you'd be lucky
enough that every molecule of wine would
hop back into the glass right but guess
what it's not going to happen in the
real world
and the quantum wave function is exactly
the same way it is possible in principle
to rewind everything if you start from
perfect knowledge of the entire wave
function of the universe in practice
that's never gonna happen
so time travel not possible
nope at least quantum mechanics has no
help what about memory does the universe
have a memory of itself or we could in
in so not time travel but peek back in
time and do a little like replay well
it's exactly the same in quantum
mechanics as classical mechanics so
whatever you want to say about that you
know the fundamental laws of physics in
either many worlds quantum mechanics or
Newtonian physics conserve information
so if you have all the information about
the quantum state of the world right now
your Laplace's demon-like and your
knowledge and calculational capacity you
can wind the clock backward but none of
us is right and you know so in practice
you could never do that you can do
experiments over and over again starting
from the same initial conditions for
small systems but once things get to be
large
Avogadro's number of particles right
bigger than a cell no chance
you