Kind: captions
Language: en
we we've talked a little bit about arrow
of time last time but in many worlds
that there is a kind of implied arrow of
time right so you've talked about the
arrow of time that has to do with the
second law of thermodynamics
that's the arrow of time that's emergent
or fundamental we don't know I guess
no it's emergent it's a is that there's
everyone agree on that when nobody's
reading so that area of time is that
different than the arrow of time that's
implied by many worlds it's not
different actually no in both cases you
have fundamental laws of physics that
are completely reversible if you give me
the state of the universe at one moment
in time I can run the clock forward or
backward equally well there's no arrow
of time built into the laws of physics
at the most fundamental level but what
we do have are special initial
conditions fourteen billion years ago
near the Big Bang in thermodynamics
those special initial conditions take
the form of things where low entropy and
entropy has been increasing ever since
making the universe more disorganized
and chaotic and that's the arrow of time
in quantum mechanics these special
initial conditions take the form of
there was only one branch of the
wavefunction and the universe has been
branching more and more ever since okay
so if time is emergent so it seems like
our human cognitive capacity likes to
take things that are emergent and assume
and feel like they're fundamental so
what it sequence of times emergent and
locality like space emergent yes okay
but I didn't say time was emergent I
said the arrow of time was emergent
those are different what's the
difference in the arrow of time and time
are you using arrow of time to simply
mean this they're synonymous with the
second law thermodynamics no but the
arrow of time is the difference between
the past and future so all right there's
space well there's no arrow of space you
don't feel that space has to have an
arrow right you could live in
dynamic equilibrium there be no arrow of
time but there'd still be time there's
still be a difference between now and
the future whatever also okay so if
nothing changes there's still time well
things could even change like if the
whole universe consisted of the earth
going around the Sun yeah okay it would
just go in circles or ellipses right
that's not every things would change but
it's not increasing entropy there's no
arrow if you took a movie event and I
played you the movie backward you would
never know so the arrow of time can
theoretically point in the other
direction for brief briefly so intent
that it points in different directions
it's not a very good arrow I mean the
arrow of time in the macroscopic world
is so powerful that there's just no
chance of going back when you get down
to tiny systems with only three or four
moving parts then entropy can fluctuate
up and down
you