GEORGE MUSSER: Thanks
for coming out today
to talk about some basic physics
and some very interesting
phenomena in that area.
My name is George Musser.
I'm a contributing editor at
"Scientific American" magazine.
I was before the senior
editor for space, science,
and fundamental physics
at that magazine
for I guess it was
something like 15 years.
Actually, I have an
undergraduate degree,
in double E, in math, and the
very first program I wrote
was not "Hello, World" it was
actually in machine language
using actually hexadecimal.
I was like 10 years old.
This was back in 1980 or
so, and I made an LED blink.
I was so proud of myself.
Today, you can do that in
two seconds on an Arduino
or whatever.
My graduate work was
on the planet Venus.
So if you have any
questions about Venus
and you're willing to put
up with information that's
20 years old, I'm
happy to oblige you
in the Q and A session.
So the phenomena I'd like to get
at today is called non-locality
or as the title suggests,
spooky action at a distance.
That's the somewhat
derogatory appellation
that Einstein gave to this
phenomena back in the 1940s,
actually.
So before I get into some
concrete physics about it,
I wanted to spiral
in on the topic
and give you some just
general remarks about it.
And then we'll get
progressively more specific
over the course of the talk.
The basic idea of
non-locality is
you can have a connection
between different things.
Something here can be connected
to something over there.
And the nature of the
connection can vary,
but, in some way or other,
the fates of those objects
are bound together.
In a sense, to touch one
is to touch the other.
You can have an effect
propagating from one
to the other.
And obviously, physics, the
physical sciences in general,
is a story of
connections in the world.
That's what physics tries to do.
But what's unusual about this
particular type of connection
is there doesn't seem
to be a connect door.
There's no rope.
There's no handcuffs binding
the two things together.
There is none of the
standard mechanisms
of physics like forces,
waves, intermediary particles.
These things are acting on
each other at a distance,
hence the name of
the phenomenon,
or phenomena, actually.
As we'll see, this is
a variety of phenomena.
And the question is,
what is up with that?
Like, what could be explaining
this weird connection
without connector?
So spiraling a little bit
more, getting a little bit
more detailed, usually
in a laboratory,
the objects that
are being connected
are subatomic particles.
They don't have
to be, by the way,
particles are easy to manipulate
and the principles that
govern them are quite pure.
They're not confounded by
the complexity of the system,
for example.
But in principle, you could
take these two bottles
and connect them.
I mean, anything can be
connected through this process.
So what you do is you
might create the particles
at the same time, through
the same kind of process,
so they are connected by
virtue of a common origin.
Or you might have
them already created,
bring them together, bang them
together, interact in some way,
and they develop this
peculiar connection
whose nature I'll elaborate on.
And typically in
these experiments,
you might hold onto one--
there may be two of them,
you might hold onto
one of them and you
give the other to your
friend who then goes off
to the other side of the
laboratory or the city
or the solar system
or the galactic empire
or wherever they may go with
their own individual particle.
You then manipulate your
particle in some way.
You measure it, really.
It gives some kind of response.
Your friend does the same
to his or her own particle
and it gives some response.
And they're the same response.
That's the nature of
this non-locality.
The particles are remaining
connected without a connector.
They remain coordinated
without any kind of-- seeming,
at least, that there's no kind
of mechanism to coordinate
them.
So this is-- if you had
to give something that's
as close to Harry Potter as you
can imagine, this is really it,
at least in
contemporary science.
This is the closest
we've got to magic.
A very subtle form of magic,
as I'll come back to later.
It's not the kind
of thing you could
use to apparate or levitate
things or transmute them
or whatever.
By the word magical,
just means that it's not
explicable in our current
physical framework
and our current
theories don't seem
to have an explanation for it.
Now this synchronicity between
these distant particles,
these distant events of
measurement of particles,
is something Einstein
was greatly troubled by.
Goes back to the very,
very earliest days
of quantum mechanics, actually
just over a century ago now.
And he was actually much
more worried about it
than almost any other
aspect of quantum theory.
And people talk a lot
about God not playing dice
with the universe and
Einstein was very worried
about the indeterminism or
randomness of quantum theory.
But non-locality is
actually above that
in his list of problems
with the theory,
or conundrums with the theory.
It's actually the
only thing he ever
wrote a paper about, which
indicates the level of concern
that he had whereas
randomness was just
something he complained about
to his friends over dinner.
Now if I had been giving
this talk 10 years ago,
let's say, I would
actually be done now.
I could take your
questions because that's
as far as people could get.
They knew there was a mystery.
There actually were
technological applications
for it.
But there was no understanding
in any kind of detail.
There's no explanation of it.
And the job of physics is really
to naturalize the supernatural,
is to domesticate
magic and pull it
into the realm of
rational explanation.
And my book is kind
of a meager attempt
to do that, to give a
naturalistic explanation
for what seems, on the
face of it, supernatural,
this non-locality.
And that explanation will
come, as I'll elaborate on,
in the form of a
failure of space.
Spacetime, more generally,
but I really focus on space,
this concept of space, which
in any kind of basic physics
is taken as this substrate, is
taken as the fundamental stage
on which the world takes
place and everything's
phrased in terms of space.
The xyz and the t, if you have
time in there, coordinates,
distances, sizes, everything
we talk about in physics
is spatial in some way or other.
And non-locality seems
to be undermining
that, seems to be
suggesting perhaps
there's a deeper level
that underlies space.
At least that's the proposition
that I'll put forward today.
That deeper level
might indicate a need
for a unified theory of physics.
So it's essential to that
whole quest for unified theory.
It might actually already
be in our theories.
We don't really
need to unify them
but it's there not
fully appreciated.
So there's different ways,
but in some way or other
you need something to
underlie, at least in this way
of thinking, to underlie space.
So let me again, continuing
my tour of the subject,
spiraling in on it.
Let me dissect the
idea of non-locality.
And to do that, I need to
tell you what locality is.
What am I negating?
What's the non in front of?
And the word locality has,
in physics and philosophy,
different associated meanings.
It's really kind of synonymous
actually with spatial.
When you see the
word locality, you
can almost substitute
in your head spatial.
The two ideas are
closely related
but locality is a
bit more specific
about what it
means to be spatial
and it has different meanings.
So meaning number one is
things have locations.
Physical things, at
least, exist in places.
You have a quality of
being localized to a place.
If you can't point to something,
a physical thing at least,
and say here it is, it doesn't
really exist, in a sense.
If, well, teacher wants to
know where your homework is.
I don't know where
it is, nowhere.
It's tantamount to
saying it doesn't exist.
Second, a second
important meaning
is that things in different
places are different things.
They have an autonomy.
They have an autonomous
existence to them.
That's actually what
we mean by thing.
I mean, what does the
word thing really mean?
It means a localized
part of the universe.
A little piece that you
can carve out and say,
ah, there's an
identifiable thing.
Has an existence that's
independent of the other things
that the world consists of.
Third, and this is the
one that people focus on
in terms of the theory,
things in different places,
so hence, different things,
are isolated from one another.
They have a measure
of isolation.
They, of course,
interact with one another
but they always interact through
the space that separates them.
So they might
interact by actually
moving through the space
that separates them
and banging into each other,
called contact action.
That's the original sense
of locality going back
to the ancient Greeks.
Contact action where atoms
would come together and hit.
But in modern physics,
we also have waves,
we have intermediary
particles, other ways for them
to interact, but it's
always through space.
Now the need to
interact through space
tells you, actually,
a lot just on its own.
It's your basic almost
metaphysical concept.
It tells you, for instance,
that the interactions
between objects is attenuated
by the distance between them.
So if I double the
distance between them,
in a lot of force
laws it's a one
over r squared relationship.
It goes down by
a factor of four.
Sometimes it's actually
not such a simple force
law, like with springs,
but in some way or other,
increasing the distance
between objects
makes it more difficult
for them to interact.
It introduces a time
lag between them
because things have to have time
to get from one to the other,
and that is limited
by the speed of light
in our current theories.
That's really the role
the speed of light plays.
It's actually not the
speed of light, that
just was a historical thing.
It's the speed of,
the maximal speed
of interaction between
objects in the universe.
So this idea of
non-locality and spaciality
is really fundamental to our
entire intellectual framework.
It's not just about physics,
it's all the natural sciences.
And it goes all the
way back to the sources
of natural philosophy
in the ancient world.
Ancient China and ancient
Greece both articulated
in different ways a
principle of locality.
And I mean, you think about
it, what does science do?
What is the purpose of
basic science, at least?
It's to create
narratives of the world.
Things exist at certain
places, they move around,
they interact.
And you can break
down any-- in theory,
you can break down any
process into that kind of step
by step causal narrative and
that is dependent on the fact
that we have this
idea of locality.
It also has a
methodological importance.
So the world is so
big and I am so small.
I can't possibly comprehend
the entire universe.
What do I do?
I break it down.
I look at this piece.
I look at this piece.
I look at this other piece.
I see how they interact,
that's usually the hard part.
And I can do that because the
world is divisible into pieces.
The world lets us understand it.
That's actually
extremely profound
and we're lucky that
that's the case.
Probably we couldn't even
exist if that weren't the case.
We certainly couldn't
exist as rational beings
unless the universe were
explicable in some way.
And that's something
Einstein also commented on.
And finally, just
let me throw up
one of the many philosophical
implications of locality,
and it has to do with
our personal identity.
So what does it mean
to be an individual?
Well, it means that each of
us has our own integrity.
We occupy a certain position, a
little volume of the universe,
and that ultimately is
underpinned and guaranteed
by the principle of locality.
Because anything that affects
me has to pass through the space
to get to me, has to
actually pass through my skin
or enter me somehow.
And if that weren't the case,
if things could just reach out,
if something could just
reach into your mind
and control your
thoughts, well, you'd
begin to question whether
your thoughts were your own.
Your whole sense of
personhood would be violated.
So your sense of personhood
depends on this concept
of locality, as well.
So I just bring
all this up really
as a way to demonstrate
the mystery,
the depth of the mystery
that non-locality
is going to represent.
God knows, physics talks
about lots of weird things.
We've got dark energy,
matter, any number
of things from quantum physics.
I mean, just name it.
Even turbulence, I mean,
so many things in the world
are just plain weird.
That's the fun of the world.
Thank God, it's weird,
otherwise, like,
why are we here?
But locality is weirder.
It's the uber weirdness.
It's the thing that burrows into
the very foundations of science
and makes us question
the whole enterprise.
OK, on the one hand,
just to sum up quickly,
the world has this
quality of locality.
Things have positions,
they interact in space.
We're individuals.
Science can partition the world.
And so locality does seem to
be an important characteristic
of, at least, the observable
world, the world that we
inhabit in a daily life.
But if you look
more closely, or do
special analysis of
our current theories,
you see this non-locality, and
it comes out in different ways.
I'll discuss a
couple of the ways
today, but let me
just kind of survey
a few of the different ones.
And what's interesting
is actually
there are many different ones.
Not just the one
Einstein originally
worried about, about
subatomic particles.
There's also a lot of
different kinds of locality
having to do with black holes.
That goes back to the work
really of Stephen Hawking.
And you're probably all aware
of this impending announcement,
one hopes if at least,
rumors are right,
about gravitational
waves, and the importance
of that announcement
probably is it will tell us
a lot about black holes.
So black holes are going
to be in the news a lot
in the coming weeks, at least,
if the rumors are correct.
The workings of gravity
also have a subtle form
of non-locality in
them, which is ironic
because Einstein invented
his theory of gravity,
general relativity, to banish
the Newtonian law on locality
that had been there.
I can come back to that later.
But this is something
that was really
only appreciated in the 1990s.
Cosmology, early universe
observations, Big Bang, all
that, there seems to be,
though it's more controversial,
some kind of non-locality
there, as well that's weird.
So in these different ways
you get different violations
of those principles I
mentioned earlier of locality.
So one example is in some of
these forms of non-locality,
the things at different
places are not
isolated from one another.
You can actually affect
this one and, boom,
instantaneously affect
the other one over there.
The effect jumps across as
if going through hyperspace
or something.
More subtly, the world can
have holistic qualities.
So what that means is and
this is a difficult concept
to wrap around-- I mean, we
use the word holism if you
go to yoga class or
whatever, but this is
a more subtle form of holism.
And I'll come back to it a few
times in the course of the talk
and try to zero in on it.
So if you don't get it
first time, that's cool.
The idea is that properties
cannot be attributed
to the parts of a system.
They're properties of a
collective of the system.
and that's a type
of non-locality.
You can't localize the
property to any of the pieces.
In fact, it's worse.
You can't even build up the
property from the pieces.
It's not like a Lego set where
you get a house from lots
of little bricks.
There's certain properties of
the whole that actually cannot
be partitioned in that way and
that's a type of non-locality.
Now this is something that
you learn as a really--
it's probably actually going
to probably into high school
physics, but certainly
undergraduate physics,
graduate school physics,
a lot of these concepts
are brought up.
But what got me personally
interested to the level that I
would write a book about it
is that I saw connections
among these different areas.
So I try to synthesize
the types of non-locality
in these different areas.
And the fact that you have a
lot of types is interesting.
It indicates that
this is just not
an isolated curiosity that
you can dismiss and put
in a carnival side
show or whatever.
It's actually
something that is maybe
at the root of the mysteries
that we face in physics today.
Now I'm going to throw out
a general purpose disclaimer
before I get into some
of the concrete cases.
I have to do that for
scientific honesty.
A lot of people,
scientists, physicists,
doubt a lot of these
intimations of non-locality.
They think maybe it's a
misinterpretation of the theory
or of the experiment.
And there's actually quite
an interesting and vociferous
debate over that, which
I do talk about a little
in the book trying
to pick it apart.
And you can see where those
skeptics are coming from.
I mean locality is a very
successful principle.
It's something we observe
just from our senses.
So why question it?
But this is one of those
cases where, I think,
the evidence is strong enough.
You don't have to make a
stronger case than that.
It's good enough that we
should pursue what it means.
And that's what I will
do the rest of the talk.
So disclaimer over.
So let me go into a
couple concrete cases
of this non-locality,
and I'll start
with the one that concerned
Einstein, quantum entanglement.
Often when I give
these talks, people
get hung up on the
word entanglement.
And you really just think about
it as a romantic entanglement
thing.
It's a relationship
between objects,
a connection between them
that's awkward, actually.
So this particular laboratory
is in upstate New York,
Colgate University.
And if you've ever
been in a physics lab,
it's actually kind of typical.
There's even a coffee
maker on the left
here, which is an important
and essential part
of any laboratory.
It's the laboratory
of Enrique Galvez, who
is a Peruvian,
actually, I think,
he's a naturalized
US citizen now,
who has really been a
pioneer in miniaturizing
these experiments.
These experiments actually
gp-- this particular kind
of experiment goes really
back to the '70s or even
the late 60s.
But they were humongous, taking
up the whole lab experiments
and now you can really
pull down into-- this
is the size of a
dining room table.
You actually could
get it probably
onto the size of this podium.
That's the progress of
miniaturization on this.
So one thing that's cool
about this table, by the way,
is you see all those
little holes on it?
It's like a pegboard.
You can actually screw
the components down
and that's super
important for getting
the alignment in these
experiments correct.
That's the hard part about
doing these experiments is
they spend months
of work-- well,
Colgate's an
undergraduate institution.
Poor RA is coming in to try to
align these mirrors and things.
So this particular version
experiment uses light.
It's an optical experiment.
It uses photons, in other words,
photons, particles of light.
And photons are great because
they're easy to manipulate.
There's also just an
established technology
for manipulating them.
So there's mirrors, filters,
prisms, non-linear crystals,
optical fibers, the
whole range of equipment
that's available for
these experiments.
Photons also have a lot
of different properties
that are nice.
Obviously, they have
color, so energy, momentum,
the direction they're moving in
but the property that's usually
focused on is
their polarization,
Polarization, it's
a binary property,
so it's just easier
to deal with.
The others are reals,
so it's kind of harder
to deal with a
continuum quantity.
The hard part about
photons is detecting them.
Remember, you have to detect
these photons particle
by particle.
So there's a lot of confounding
light in these experiments.
This room has to be
completely darkened
for them to do the experiment.
Even all the LEDs--
and everything
we have has LEDs in it--
has to be taped over
with electrical tape.
There's a big curtain
drawn around it.
It's actually spooky just
by the virtue of the set up
when they do it.
Other kinds of particles have
countervailing trade-offs.
So maybe they're easier
to detect but harder
to manipulate, like electrons,
protons, charged particles.
And I don't know if anyone
saw, there's a big "New York
Times" article in, I guess,
beginning of November, maybe
late October, spooky action
at a distance proved.
That was the headline,
something like that.
And what was cool about
the experiments described
in that article is they
combined the advantages
of different types of particles.
So they used photons to
connect different wings
of the experiment but electrons
in the wings of the experiment
because they were
easier to detect.
So there was a
hybrid approach that
got over a lot of the
difficulties of doing
this experiment.
But this particular photograph
dates to, I think, 2011 ,
so it predates that.
So from this angle,
this is a blurry shot,
but I show it because
you can see two--
if you run your eye-- I should
have drawn a line on this--
if you run your eye
vertically on this you
see two lines of instruments.
And those would be
the two entangled
photons in this experiment.
So let me just show you
the schematic of this.
So it starts when you
have a laser in back that
emits a stream of photons and
they're blue for a purpose.
There actually are blue or
maybe nearer to violet photons,
and they run through
different set up
instruments that align the
beams and clean up the beam
and everything and
then they hit the thing
I call a crystal, that
I'll come back to.
And that splits them,
through a nonlinear process,
into two photons each
of half the energy.
So that puts them into the
red part of the spectrum.
And then they hit, because I'm
dealing with polarization here,
polarizing filters and they
either get through the filter
or not.
And they're picked up by
a detector-- actually they
go into a set of fiber
optics and they're picked up
by a detector and
instrumentation at the bottom
there and they look
for coincidences.
So when the photons hit the
detectors at the same time
within a certain
window that counts
as a coincident detection.
These particular detectors,
by the way, are about 10%
efficient.
So one in 10 photons
that strikes them gets
picked up and so one in
100 pairs that strikes,
and that kind of statistics
becomes important
but has been overcome in
these recent experiments.
So this is my finger pointing
to the polarizing filters
because that's a central element
of this experiment, gives you
a sense of scale.
That's the distance over
which, in this experiment,
the spooky action is occurring.
It's about the width of my
palm or hand or whatever.
That's the spooky
action distance
in this particular
experiment, but that
can be extended to arbitrary
lengths if you want to.
But here we just do
it to that width.
The distinct look of a 35
millimeter camera lenses,
like a 50 millimeter lens, you
can turn the dial on the side
and that changes the
orientation of the polarization
of the filter.
So, in the past,
I've given a talk
in very similar to
this and at the end
and in email afterwards,
everyone always asks me
about that crystal I mentioned.
The crystal that splits
the incoming blues
into two outgoing reds.
And I think part--
it's a crystal,
sounds weird, but
it's actually--
I didn't even get into the
details in it in previous talks
and not even in the book
because the details actually
don't matter.
But, to head off
any questions, let
me go into the crystal
for a couple minutes
because it is
actually cool physics.
There actually is an amount,
that little transparent cube
in the middle is actually
an example of this crystal.
It's actually a crystal
with barium borate.
Barium borate comes in
different crystalline forms.
This is the beta phase of it.
And it, as this
cool image shows,
it actually splits the incoming
beam into two outgoing beams
through this process
known as down conversion,
spontaneous parametric down
conversion is the full title.
And each of those terms has a
meaning, but down conversion.
This picture, by the way,
is really hard to make.
This is a long exposure.
It's probably a
composite image even
and they actually made it by
taking a piece of tissue paper
and running it along the
beam during the duration
of the exposure so you
can actually see it.
Because otherwise you don't
see the beam in the laboratory.
It would be bad if you
did because that means
there would be
scattering from the beam
and you'd be reducing the
intensity of the beam.
So you don't want to
see the beam usually,
but, in this case, for
the dramatic picture,
they did that using a
little piece of paper.
It's actually cool.
So the splitting that occurs in
the crystal at the very center
of this picture is,
you can loosely think
of it as a type of refraction.
It's a nonlinear exotic
type of refraction,
that's what's occurring here.
It actually requires quantum
field theory to explain fully,
but just for simple
purposes, think of it
that the beam is
actually being refracted
into two outgoing beams.
Now here's a schematic
diagram of that set up.
There's a crystal, that's
that block in the middle.
And that white line
that you can see
on the side of the block, that's
the optic axis of the crystal.
So what you do is-- the crystal
is symmetrical about that axis.
You send in, in this
case, vertically
polarized light
parallel to that axis
and the crystal will create two
outgoing horizontally polarized
photons.
In this case, the photons had
the same polarization, namely
in the horizontal direction.
Now in case you ever watch a
YouTube video or look this up,
I think, even on Wikipedia
or certainly in any magazine
articles, often they
describe a set up
where they're
opposite polarizations
and there's no
contradiction there.
You can actually set up
the crystal to do both.
But in this experiment
that I'm describing,
they're the same polarization.
So you can rotate the whole
thing 90 degrees again you send
something that's-- photons are
polarized parallel to that axis
and they come out polarized
perpendicular to the axis.
So that is how you
get two photons.
Now you need two entangled
photons and that's something
a little bit more subtle.
So if you don't get it
the first time around,
I'm going to come
back to it later.
But let me spill
it out and then we
can talk about it if this
doesn't make any sense.
So what does it mean
to be in entangled?
It means that the photons have
a polarization, excuse me,
that the pair of photons
has a polarization
but the individuals
don't, which is to say,
the individuals have an
ambiguous polarization.
That goes back to this whole
business of the property
can't be localized.
So each photon, as I'll show
in an animation in a second,
actually doesn't even
have a polarization,
but the system, as a whole,
has the property of they're
the same polarization.
And that's the mystery here
that we're trying to solve.
So the way that that's
done in the experiment
is you take two of those
crystals, you pair of them up,
you send in diagonally
polarized light,
and it comes out with an
ambiguous polarization.
It's the same
polarization on both sides
but it's an ambiguous
polarization
and that's the weird
thing about entanglement.
The ambiguity is
only resolved later
when those things
actually hit a detector.
When they hit a
detector, they resolve,
and they're, in this
case, either horizontally
or vertically polarized
but they're always the same
each time.
And I'll come back
to that in a second.
So crystal is nice because
it gives you a controlled way
to produce entangled photons.
But I want to emphasize that
there's nothing special about
the crystal per se.
It's not like a
metaphysical crystal
that you buy in a
Haight-Ashbury kind of thing.
No, it's just a particular
good way of doing it.
I don't know if any of these
lights in here are fluorescent,
they look LEDs to me.
The spots probably
aren't, but if you
go in the fluorescent
lights in the hallway,
they are emitting
entangled photons.
This is something that's
not actually widely known.
The very first
experiment in the 1970s
actually used
mercury vapor lamps
because a mercury
atom gets excited
and then it decays
from its excited
state by emitting photons.
It sometimes emits
photons in pairs,
and those two pairs
will be entangled,
will spin entangled or
polarization entangled with one
another.
I did a do it yourself
version of this experiment
in my basement using a
radioactive isotope, sodium-22.
It gives off
entangled gamma rays,
and it can be picked
up by a Geiger counter.
A Geiger counter is just
an extremely cheap photon
detector, basically.
So you can do this
with all sorts of ways.
You can just bang particles
together and entangle them.
So there's nothing
special about a crystal,
it just, it gives
you a controlled way
to do this experiment.
Now the physical implementation
of this isn't important.
So we can go to a higher
level of abstraction.
We don't have to work at
the physical layer here.
We can go to a higher level.
You can think of
these things as coins.
That's the higher
level of abstraction
we can take this-- each
photon is like a coin,
like flipping a coin.
The whole thing is an extremely
expensive coin tosser,
like $10,000 coin tosser.
And what it does is it creates
coins, flips them, creates
another pair, flips
it, creates a third,
flips it, thousands of times a
second, adds up the statistics.
So whether it comes
up heads or tails
is whether it goes through
the polarizing filter or not.
And those things are
dialed so there's a 50/50
chance it's a fair coin.
So we can go to this higher
level abstraction and a coin
gives you a certain series
of results, heads, tails, et
cetera.
Purely at random, unpredictable
by the indeterminacy of quantum
mechanics.
Go to the other side, you also
get heads, tails, blah, blah,
blah.
Again, completely random,
completely unpredictable,
indeterminate.
Both sides, they're
the same outcome.
That's, in this
particular experiment,
that's the connection
we're talking about.
That's the weirdness
that is at the heart
of this entanglement experiment.
Two random outcomes in two
places giving the same result.
Like two coins being flipped on
two different football fields
all giving the same answer.
I like the coin metaphor
for a number of reasons.
Obviously, any metaphor
will have its limitations,
but this one does
get across the idea
that these are two independent
events, two independent coin
tosses, coming out the
same on both sides.
That's the ambiguity I
was talking about earlier.
Before, you flip a coin,
almost by definition,
there's no outcome to it.
It's ambiguous.
Otherwise why flip?
So unfortunately, a lot
of my Amazon reviewers
are missing this
particular point
and bringing me
down in their stars
because they're saying
well, George, come on,
what's the mystery here?
Why did you write
hundreds of pages
on this topic when it's obvious
you've created identical coins.
And you toss them and they
give identical outcomes.
It doesn't seem
mysterious at all.
Well, that's partly an artifact
of this particular set up
of the experiment.
It's also a misunderstanding
that quantum theory
is indeterminate.
So these are indeterminate
tosses coming out the same.
But to prove the
point, what you can do
is you can do an elaboration
on the experiment.
I can dial those polarizing
filters to different settings.
I have complete freedom.
I can dial it actually
to any setting I want,
but I'll choose two
particular settings.
So there's four
permutations of settings
on the left and the
right, and I'll just,
for the purposes
of metaphor, say
that's like flipping the
coin with my left hand
or with my right hand.
So I choose the hand at random.
In other words, I dial the
polarization at random.
So what I've designated
as left comes out
whatever I go down the line,
it's a series of outcomes.
And so there's two
levels of randomness here
that's important.
One is the choice of hand
with which I'm tossing,
and if I'm coordinated,
which actually I'm not,
I can flip them and get
these kinds of results
with either hand.
And there's the randomness
of the outcomes.
I can do that on the
other side, as well
and I get actually a different
series of hands, in general,
and a set of outcomes.
So, in this case, they're
not exactly identical.
This is where we start getting
to some of the mysteries of it.
Notice that there's--
I've highlighted them,
two exceptions to
the identical rule.
They're not identical
on both sides.
They're identical for three of
the four permutations of left
and right hand, but
for one, they're
actually always anticorrelated,
always the opposite outcome
on the two sides.
Now notice where you
get the exceptions.
You get the exceptions only
if, and only if, coin one
is tossed by the
person with their left
and coin two is tossed by the
person with their right hand.
In all other cases, you
get a different outcome.
So the outcome depends on
both sides inextricably.
It's as though there's
a communication
between both sides.
That's the kind of connection
I'm talking about here.
And you can elaborate on
this to your heart's content.
There's just a zillion different
ways of-- polarizer settings,
you can do three
particles, four particles,
infinite number of
particles, in principle,
and you get outcomes that cannot
be explained simply by taking
two identical coins
and flipping them.
It's more subtle, obviously.
No known force is acting
to interlink the two sides
and communicate between them.
Ah, you say, known force.
Well, what about unknown forces?
And that's always a concern
because we certainly
don't think our
theories of nature
exhaust the
possibilities out there.
Probably the Higgs boson
comes with a whole series
of Higgs-like forces.
Maybe they could
communicate, who knows?
Ah, but you can rule that out.
One easy way to do it is
just move the particles
further apart and see what
happens to the correlation
between them.
And it's not affected by that.
So normally if you
have two things that
are correlated, say, by a wave
and you double the distance,
you expect the strength of
the correlation to diminish
and that doesn't happen here.
So there doesn't seem to be
anything passing through space.
No force, even an unknown kind.
But also what's done
here is the experiment
is done too quickly for a
force or hypothetical effect
to propagate.
You can actually do it at
the same, exact same time.
Measure this particle
and change its setting
at the exact same time
as you do it over here.
So any force would have
to be instantaneous
across that distance.
It would have to
move infinitely fast.
Infinitely is obviously
faster than light,
so that is ruled out by
Einstein's theory, or at least,
would contradict Einstein's
theory in a very serious way.
So it doesn't seem to be caused
even by an unknown force.
We're left with this
magic, this weird thing.
I promised to qualify that
word magic a little bit,
and I'll do so now.
The magic is extremely subtle.
You're not going to win a
Wizarding Cup with this magic.
You're not going to even pass
your Owls with this magic,
because you don't see it if
you just confine your attention
to one side or the other.
You just see heads, tails,
heads, tails, whatever.
Other side, heads,
tails, heads, tails.
You just see 50/50 outcome.
There's no statistical
variation on the two sides.
Only when you compare them do
you see a pattern of any sort.
So very subtle, very
weak form of magic,
but it's still pretty weird.
By the way, that's
the reason-- and I
have to say this whenever
I'm in California doing this,
no psychic powers
can be involved here.
No telepathy, this is not
going to be of any use
to explain paranormal phenomena
even if those phenomena could
be verified experimentally.
Actually in the '70s,
that was a live issue.
So it's been settled.
It's still pretty cool, though.
There's lots of
technological applications
obviously, for
quantum computers.
This is-- or certain types
of quantum computers,
this is important.
The one that gets the most
traction, the most attention
is cryptography.
You can use this to certify
the privacy of a communication
channel.
And essentially
the way it works is
you keep one of the
particles that are entangled.
You give one, or send the
one across to the person
you're communicating with
and if the NSA intercepts it
in the middle, it will
change the correlations
that your friend receives
on the other side
and there's no way for
even the government
to mimic that connection.
It's just guaranteed by the
laws of quantum physics.
And then once you've established
that communication channel,
you can send a secure key
from one party to the other
and then encrypt whatever
message that you have.
OK, so that is
quantum entanglement.
Just to give you a flavor
of how broad the concept
of non-locality
is, and then I'll
try to get into an
explanation for it,
I'm going to mention the
type, or at least one
of the types of
non-locality that
are involved with black holes.
And again, we're going to
hear a lot about black holes
in the coming days,
so that's cool.
Here is a picture of a black
hole indicated by that arrow.
Not much there, which
is the point of it.
You do actually see
a little bit of gas
where that arrow terminates.
And this is an infrared
image, and the spectrum
indicates that the gas has a
temperature of 10,000 kelvins.
Now if you had a region
of that size glowing
with the temperature that's
much hotter than the surface
of the sun, you would
have a little star there.
In fact, what you would see
is something more like that.
So there's a disconnect here
between the temperature that's
observed and the
luminosity of the object.
The object is way underluminous.
The energy is going missing.
It's going down the black hole.
That's some of the best
evidence we currently
have for black holes.
This kind of missing
energy and also
speaks to what is a black hole?
It sucks things in,
can't get back out.
So this is from the movie
"Interstellar" and some
of the simulations of
gravitational lensing done
for that movie.
Black hole basically looks
like, from the outside,
a giant, extremely dark planet
with a lot of stuff around it
usually.
And if you fall into it,
there's no hope for you,
you just fall in and
that's it, you're dead.
So what's important here
is the irreversibility
of the act of falling in.
You can't un-fall You can't
ascend out of the black hole
by definition.
It's got this perimeter or
event horizon that things cannot
cross.
What's important for
our purposes today
is that to cross that event
horizon, in other words,
to escape from a
black hole, you would
have to exceed the speed
of light, you would have,
essentially, to violate
the principle of locality.
Principle of locality
is what's really
explaining or kind
of underpinning
the irreversibility
of black holes.
So there's a connection between
irreversibility of black holes
according to Einstein's theory
and the principle of locality.
And this is the thing
that Stephen Hawking
clarified in the mid-1970s.
He showed that the black
hole is like a big bonfire.
It actually incinerates things.
So if your hapless
astronaut falls in,
the black hole will glow
that much more strongly
and the energy represented
by the astronaut
will actually come out in the
form of random heat radiation.
Now if you were
clever, you might say,
aha, I'm going to collect
all that heat radiation
and I'm going to turn it
back into the black hole
and I'm going to
recover my friend.
And you would reverse the
process, as you could actually
do with chemical burning.
If I had an actual
fire here, God forbid,
and were to burn
something in it,
I could take all the products
of that chemical reaction
and, in principle, run
the reaction backwards.
It would be difficult to
do with an actual fire,
but in principle you could.
But if you try to do
that with a black hole,
try to run it backwards, you
just get more of the same.
You can't recover your friend.
You just get more
random radiation.
It's actually even
uncorrelated with
the first random radiation.
So it's really random now,
and no astronaut will pop out.
If I were to drop an egg on
the floor and it shattered,
a hard-boiled egg
and it shattered,
I could imagine running
the whole movie backwards
and it would pop up off
the floor and back up
onto my plate.
You can't do that
with black holes.
So that is a problem
because everything
in fundamental physics, the
laws of fundamental physics
are all time reversible.
If I can move this direction,
I can move that direction.
If I can make it, I can
break it, or vice versa.
So the black hole's going to
be an exception to that rule.
Obviously, in daily
life, we do see
a lot of irreversible processes,
but if you look more closely
they're reversible
at the atomic level
and what gives them their
apparent irreversibility is
the initial conditions on
it or a asymmetry that you
have in there.
So fundamental physics is by its
very nature, time reversible.
So it looks like black holes
are an exception to that rule.
So there's something
weird going on with them.
And you might say well, it's
just black holes and just
exotic objects in the center
of the galaxy or whatever, so
big deal.
But it turns out that if
you violate irreversibility
in any part of the
fundamental laws of physics,
you would violate it everywhere.
It's like being pregnant.
You can't be a
little bit pregnant.
You can't be a little
bit reversible.
And so the laws of
physics predict,
or at least the grounds
on which we construct
the laws of physics, predict
that black holes themselves
should be reversible.
And I made the point
earlier that irreversibility
and locality are connected.
Ergo, reversibility and
non-locality are connected.
It's a subtle argument,
but the basic idea
is that there just has to be a
way to get out of a black hole.
There has to be an
escape hatch some way
or you have to be able to
exceed the speed of light
or there has to be a
tunnel of some sort
to get you out of a
black hole, all of which
would violate locality here.
So in the interest
of time, I'm actually
going to skip the next instance
of non-locality in black holes
and if you are curious, ask me
about the holographic principle
in the question
session or just we
can talk outside, if you like.
And it's actually pretty cool.
So I promised an
attempt to explain
these non-local phenomena.
So let's think about what
the phenomena represent.
They connect things
like particles,
or the inside and
outside of a black hole,
pieces of a black hole,
different aspects of nature,
as though those objects
were not separated.
As though they were actually
were just juxtaposed
or even coincident.
So the thinking is
deceptively simple,
that the distance between
things is somehow a mirage.
That things seem to be
separated but they're
really juxtaposed
at a deeper level
and might that explain
the non-local phenomena?
So that's just to say that space
is a mirage and mirage isn't
maybe the right word here.
It's really that
space is a construct.
Space is built. It's
not fundamental,
it's built on something.
So this is actually
where we can make contact
with a whole different
direction on the problem,
and that's always good
when you can laterally
think like that, having
to do with understanding
the force of gravity.
So in Einstein's theory, the
general relativity theory,
the force of gravity
is associated
with the structure of
space and particular,
the curvature of space.
So why does a baseball
arc back to the ground?
Well, the trajectories
through space and time
of the ball and the ground
will actually intersect,
and they'll do that
because Earth, its mass,
has warped space
around it causing
paths that were
parallel to actually
not to be parallel anymore.
So gravity reflects the
structure of spacetime.
And one of the great scientific
enterprises of our age
is to combine quantum theory
with Einstein's theory,
to combine quantum theory
with gravity theory
to give a quantum
theory of gravity.
Now this is where you get into
string theory, loop quantum
gravity theory.
You can go watch or read Brian
Greene on this, Lee Smolin.
I have, my first book is
on these theories, as well.
And I'm going to--
there's a lot, by the way,
a lot of controversy and dispute
and everybody hates each other
and it's very vexed.
But what's often
lost in that debate
is they're all saying the
same thing in different ways.
They're all saying that space,
or at least a kind of space
that we inhabit is constructed.
It may be constructed
by strings.
It may be constructed by loops.
It may be constructed by
causal event networks.
Space may look
something like that.
So this featureless
rectangle is meant
to represent the
space that we inhabit.
It's featureless.
You know, I look at
space in front of me
and I don't even see it.
I mean, it has no content to it.
But if I were to
zoom in, deep, deep,
deep down, I would
begin to see some kind
of filigree structure,
quanta of space in some way
or other that might
be formed again,
by any of those kind of
fundamental ingredients
like strings or loops.
So again, space is
a construct in all
of these theories,
independent, completely
independent of all of
these arguments about
spooky action at a distance.
This is coming from another
tradition in physics
altogether.
So one thing that's
cool about this approach
is you can take your
intuitions, such as they,
are about ordinary
atoms, hydrogen, helium,
et cetera, ordinary
molecules, H2O, whatever
and apply it to space.
Some of that intuition
should carry over
into your understanding of
space if both are molecular
or quantized in some way.
So water, what are some of the
properties of liquid water?
So it flows, it can wet
things, form droplets,
so it's associated
with surface tension.
I can send waves through
it, sound waves or ripples
on the surface.
I can freeze it, boil
it, in other words,
I can change its state.
All those properties
of liquid water
are not properties
of H2O molecules.
H2O molecules don't
flow in the sense
that we mean the word flow.
They certainly can't undergo
any change of state, at least,
an ordinary change of state
as we understand that.
All those properties of the
liquid form, the material,
are properties of
the collective.
You take 10 to
the 24 whatever it
is H2O molecules in this bottle,
and you get those properties
just by massing them together.
So maybe that intuition
carries over to space.
The atoms of space,
the quanta of space,
whatever, the strings,
loops, et cetera.
Are not themselves spatial.
Space is something that
emerges in the collective.
It's an emergent property of
kazillions of those quanta.
And the space we inhabit may
be like a crystal in a phase.
It may be one of the many
phases of that system.
So that actually ties into
the idea of locality again.
In a crystal, each
part of the crystal
has a well defined neighborhood.
So a given molecule or atom
or whatever in the crystal
has some neighbors to it.
That's not the
case with the gas.
The neighbors are always
shifting around with that.
There's no fixed
sense of neighborhood.
So our space is sort of
like a crystal in some ways.
It has well defined
neighborhoods of things.
But you could melt space,
evaporate space, screw around
with space in different
ways and transform it
into different phases
and that would--
independent of the
kinds of phenomena
I'm talking about today,
that would actually be
great to explain black holes.
The black hole actually may be
a place where space is literally
evaporated.
It's undergone a
change of phase.
In other words, in
that case, there
wouldn't actually be an
interior to the black hole.
The black hole surface would
actually mark the end of space
and inside would be sort of
like a vapor phase or something,
but something that's
certainly not spatial.
I don't know if anyone in
here has heard of the firewall
paradox that's been
discussed in physics a lot,
but that's kind of the
outcome of that paradox
is to suggest that there is
no interior of a black hole.
So here is in animation
that I created
to try to get across, in a
very simplified model, what
I'm talking about here.
So here we have a collection
of nine atoms space,
those are the dots arrayed
around the polygon.
This is not a spatial system.
This is meant to represent
a highly energetic network.
Each edge of the network
represents a degree of energy
and every node is connected
to every other node.
So there's no sense of
distance in this network.
Everything is equally
distant from one another.
You couldn't even actually
put that into a-- I
guess you'd need a
nine-dimensional or
eight-dimensional space or
whatever to actually represent
that spatially.
So it's not a spatial system.
Then you imagine cooling down
the network, which corresponds
to fewer links, and now you
see what kind of network
that you have.
It's somewhat contrived, but
this gives you an idea of it.
Now you have something that is
beginning to look like space.
There's a sense
of, in other words,
a sense of distance
in this network now.
You can actually assign
coordinates and define a metric
on this network.
Now, what's nice
about this thing is
you can begin to play
games, and you say,
well, crystals have
defects in them.
They have irregularities.
Breakage is an irregularity.
Well, maybe we can try to think
about what that would be here.
So, in that case, maybe you
maintain one of the edges here.
It didn't in the
process of cooling,
and now look what happens.
You get a direct connection
between this bottom left
and the top right node in
this little miniature almost
like Cartesian-like grid.
That is sort of like having
a non-local connection
because those two points in
space, which on the face of it
seem far apart, are
actually directly connected.
Like a little wormhole
between them and actually
there's a connection there
with the idea of wormholes.
So this is, obviously,
a simplified model.
It's highly speculative,
but I think it's fair to say
and I think it's defensible.
I'd actually stand up
in front of Brian Greene
and Lee Smolin and
the others and say,
ha, you guys all think
that space is constructed
in some way or other, it's
coming out of something deeper,
be it just graph theory approach
or some other approaches,
as well.
So, in that case,
non-locality is no longer
an insoluble puzzle.
It's no longer supernatural.
You can make it natural.
You can explain it in terms
of some kind of network.
You have to expand your physical
framework, but you can do that.
More metaphorically,
you can think
of the non-locality as like,
the property of a Turkish rug.
If you go to a Turkish or
a Persian carpet dealer,
sit and have mint
tea for a long time,
eventually walk out
with a rug or kilim.
And you can begin to look
at the quality of the weave.
You can look for worn
spots, imperfections
I've got a one at home.
We've got one, I actually
didn't want to buy it
because it had this guy.
They drew a picture of a guy
on it and he didn't have an arm
and he looked like that.
And my wife was like,
George, no way that's
the cool thing about
this kilim is that it
indicates it was hand-woven.
There's a slight imperfection
in the carpet telling you
how it was made.
So non-locality is like that.
It's an imperfection in space
telling you a little bit maybe,
maybe how space is woven.
So let me just wrap up and then
I'd love to take your questions
and talk about more.
We've got this
phenomenon or phenomena
of non-locality,
spooky connections
between different places,
different things that,
by right, shouldn't
be connected.
And again, most
of the time, that
would be the end of the story.
But in really the past 10
years you're beginning to see,
as people talk more about
emergent spacetime, the germ
of an explanation for it.
It's derived from some
deeper structure in nature.
And what's cool and I hope
science fiction writers will
pick up on this, you can imagine
universes that are not spatial.
That the atoms have
rearranged themselves
into some non-spatialness and, I
mean, what does that even mean?
It's like, how do
you visualize that?
It doesn't mean the
universe has gone away,
but it's entered
this other phase
and how cool would that
be to try to visualize?
Thank you very
much for listening
and I'd love to
take your questions.
So I've been told that
there's microphones,
but I guess you guys know the
routine much better than I do.
Or we can talk
afterwards outside.
AUDIENCE: Going way back over
here to the start of the talk
show because my mind is totally
spinning around circles.
GEORGE MUSSER: That's
where should be.
AUDIENCE: But how
do you actually
measure-- when two photons
strike at the same time,
how do you actually
measure things that
are that close to
one another in time
and that are so small,
in terms of photons?
GEORGE MUSSER: Good question.
So the question is
how do you really
know that you conducted the
experiment simultaneously
on both wings?
AUDIENCE:Very small quantities
at a time, very small, small,
small particles.
GEORGE MUSSER: Right, so
usually with that actually you
guarantee that by the path
length in the experiment.
You just make sure that
the photons are traveling
the same distance and
there's a variety of ways
you can test that and measure.
You look for the phasing
of the light through it.
So there's a whole precursor
to the experiment that'll
establish that the photons are
traveling over the same period
of time to each other.
Does that answer your question?
AUDIENCE: Is that
like [INAUDIBLE]
of a second or something?
Like these things happen at
the exact same time, 0.000,
you know, something?
GEORGE MUSSER: Right so
there's some master signal
that's going out and
you have to be careful
because everything's happening
at the speed of light here,
that the distance over which the
signal that's provoking the two
wings of the experiment
to release their photon,
for example, that the signal's
traveling the same length,
so therefore, it takes
the same amount of time
and that makes these two
events, in theory, simultaneous.
Now obviously,
there's going to be
some kind of experimental
precision on that.
I think the limit is something
like 10,000 times faster
than the speed of light.
That would be the speed
at which something
would have to cross
the wing given
the precision of the timing
on those experiments.
I mean, you can
synchronize them with,
certainly with picoseconds
or something like that,
but I don't know what
the detail would be.
And then you can, another fun
thing you can do is you can,
because the Earth is rotating,
you can actually watch
the experiment for a 24-hour
period and if universe has any
kind of hypothetical frame of
reference that's an absolute
frame of reference, you would
rotate through that frame,
so you should see variations
in the timing, which you don't.
So the whole thing
seems to be kosher
as far as Einstein's
theory is concerned.
AUDIENCE: OK, thanks.
GEORGE MUSSER: Sure.
It's actually fun to get
into the nitty gritty
of these experiments.
The timing is a huge issue.
Those crystals are actually
extremely inefficient.
They'll release only like
one laser photon in a billion
will actually produce
the entangled photon.
So there's a lot of statistics
that you have to work through
on that and that's why this
has taken decades really
to bring to it's current state.
AUDIENCE: You skipped over some
slides about holographic theory
and how it relates
to black holes, which
is an idea I've
learned about recently
and it's really compelling.
So I wondering if you
could elaborate on how that
might relate to non-locality.
GEORGE MUSSER: Yes, so, this
might be too long for an answer
to your question.
We can talk about it
more in the corridor.
But it goes back to what I
was saying about black holes
being like incinerators.
They have a temperature to them.
That comes out of the
work of Stephen Hawking.
So, first of all,
that immediately
implies, by the way,
that the black hole
must consist of some kind
of microscopic structure.
Anything that has a temperature
and can raise or lower
temperature, like water,
has to be molecular
because the molecular
motions are what's
actually storing the heat.
It's what's actually
representing the concept
of temperature here.
So the black hole
already, you know,
has to be divisible into some
kind of molecular, atomic,
or microscopic structure.
And then you can
play other games.
You can do things like
hypothetical games of,
well, if I add a certain
amount of energy to-- well,
let's take it with water.
If I add a certain
amount of heat energy
to this water and the
temperature bumps up
just a teeny amount,
then I know there
must be a lot of molecules
because the energy's being
divided over those molecules.
If it goes up a huge
amount, few molecules.
You can actually
count the number
of molecules in the
water, and you can
do the same for black holes.
And with water, when you do a
counting exercise like that,
the number of molecules is
proportional to the volume
of water.
If I have a bigger
bottle, more molecules.
It just scales up.
There's a volumetric scaling.
It's too long to go back
to the slide on this,
but if you do the same
thing for black holes,
it scales up with the
area of the black hole.
If you do this kind of
exercise of how many molecules
does the black hole have?
It's proportional to the
surface area of the black hole,
not to the interior volume.
So a black hole from the
outside looks three-dimensional
but it's acting, it's behaving
as a two-dimensional system.
And that is where
the word hologram
enters this whole discussion.
Because a hologram, you
know, Princess Leia,
looks three-dimensional.
You can actually walk around the
droid projecting Princess Leia
and see it looks
three-dimensional,
but you know that it's
two-dimensional, ultimately
two-dimensional.
And you could probably
get that by looking
at the kind of details
that Princess Leia had.
If you enlarged
the hologram, you'd
begin to see some
graininess in it that
would indicate the
thing is actually
a two-dimensional projection.
AUDIENCE: But isn't
the surface area
of the black hole related to
its volume, like a sphere.
GEORGE MUSSER: You would
think so but that, no.
I mean, there's a couple levels
at which the answer is no.
First, the level
is actually-- even
in general relativity theory,
the interior of a black hole
is a highly distorted spacetime.
So it doesn't scale up.
There's actually more space
in it than there should be,
in a way, because
of this distortion.
So it looks like a
ball on the outside
but you can't do your
4/3 pi r cubed with it.
It doesn't work like that.
And worse, in the quantum
theory of gravity, at least
according to some of
these interpretations,
there is no interior.
So there's nothing to volume.
There's no volume there at all.
And, oh, but the
connection to locality,
I promised to go back.
The volumetric scaling is
actually related to locality.
So if you scale up--
if I have two water
molecules-- molecules,
certainly, but certainly
bottles, I can treat each
independently and then
add up the total
volume because I've
divided the bucket of water, or
whatever I have into subvolumes
and added up the subvolumes
to get the total volume.
That's where you get
the volumetric scaling.
You just integrate
over that x cubed.
So that volumetric scaling
is failing for black holes
and since the volumetric
scaling comes out of locality,
it means locality is
failing for black holes.
A lot of these
black hole arguments
require a couple
stages in logic.
AUDIENCE: Thanks.
GEORGE MUSSER: Sure.
So you guys are all like happy
with all this and there no
questions?
It takes time to
formulate them, so I
think I'll be around
for lunch and you're
welcome to pester me.
AUDIENCE: Hi, I just
have one question.
I don't understand--
well, by some definition
of understanding-- the
part about when you're
saying that the black
hole is irreversible,
you're saying that you would
expect it to be reversible
but it's not what.
You would expect
it based on what?
Based on the way
the math works out?
GEORGE MUSSER: Yes.
AUDIENCE: And the other
one based on observation?
It's not clear.
GEORGE MUSSER: I
rushed through that
and I'm glad you
called me on it.
So the question is, in
general relativity theory
black holes are
irreversible by definition.
You fall in, you
can't get back out.
It's all the well known
properties of black holes.
You'd have to exceed
the speed of light
to get out, specifically.
So that has always been
considered a paradox in a way.
It's always been considered
a problem that black holes
seemed to be irreversible when
everything else in science is--
AUDIENCE: And by
seem to be, you mean
seem according to the math?
GEORGE MUSSER: Yes, yes.
Well, certainly
according to the theory.
They're observationally
irreversible.
What's a good example of that?
I mean, the simple example
would-- it's not entirely
the same as the theoretical one,
but I'll give it to you anyway.
So if you have a neutron star,
just any physical object,
and matter falls onto that
object, it will heat it up.
It's like, if you pummel
it, it will heat up
and the object will
radiate away that energy.
So there's a steady state
that will be achieved
in any kind of material system.
And this is a well
known aspect of stars
and other systems like this.
Black holes are
unable to achieve
any kind of steady state
like that, at least
according to the theory and
also according to observations.
You see, in the
example I showed,
the black hole was actually
sucking in some gas but it
wasn't-- as it sucked in, it
didn't heat up and release
the energy of the gas out again.
So there seemed to
be an irreversibility
in that process.
So the contention
that Hawking made
is that if you look long
enough, as in 10 to the 30 year
long enough, you
would eventually
see the energy emerge back out
in the form of these Hawking
particles.
And that also was irreversible
because the Hawking particles
coming out are random.
You couldn't unwind the system.
AUDIENCE: Did that
correlate [INAUDIBLE]?
GEORGE MUSSER: Exactly
there's no correlation.
In fact, I'm glad you bring
up the word correlation there
because if you had two
entangled, if you played
a game, two entangled
particles, you
threw one into a black hole.
The one that came
out would no longer
be entangled with that
one that you kept,
which is violating the
reversibility of quantum
theory.
That's actually why
it's called a paradox.
Because quantum
theory is telling you
that you have an
irreversible process,
which is against quantum theory.
So there's a loop there
that is contradictory.
Does that help any?
I know it's hard to get
your mind around but--
AUDIENCE: Thanks.
GEORGE MUSSER: Sure.
Well, thank you all
for coming today.
If you do have
questions, pester me.
I'm happy to-- and
actually for me,
the benefit of
giving these talks
is really the questions
because they provoke me
like it did with the down
version crystal, actually
modified the talk
and will modify
another edition of the
book based on the questions
that I got.
So if you do have
questions, feel free.
Or if you don't
want to ask them,
I can give you my email
address later and we can talk.
Thanks.
[APPLAUSE]
