MALE SPEAKER: Good morning.
Thanks for coming.
I'm here to introduce
Amanda Gefter and her book,
"Trespassing on
Einstein's Lawn."
And I came to this book
through a confluence
of several factors.
My late father was a physicist
and had the opportunity
to exchange a few letters
with Einstein himself
and always had them locked
away in the safe deposit box.
It was always a
special family thing.
And separately, he
and my mother used
to go to a particular Chinese
restaurant in Philadelphia
all the time, and the young
five-year-old son of the owners
would always hang
around, being playful.
But he also liked
math a lot, and my dad
started tutoring him in math.
The young man grew
up, went to Wharton,
and is now at Khosla
Partners, a venture
capitalist out in
Silicon Valley.
So my dad helped spawn a
Silicon Valley hotshot.
So when I heard of Amanda's book
and that it involved Einstein,
physics, fathers, Chinese
restaurants, and Philadelphia,
where I'm from, I realized
this was a book I had to read.
So without further
ado, Amanda Gefter.
[APPLAUSE]
AMANDA GEFTER: So
first I just want
to thank Google so much
for hosting me here today.
It's a real privilege to
be here in this building
and to get to talk
to all of you.
So when I was 15
years old my father
took me out to dinner at our
favorite Chinese restaurant
and asked me how I
would define nothing.
And this was an odd dinner
table question but not
entirely out of character
for my father, who
was this sort of Zen
guru, former hippy
turned radiologist.
And so I said I
would define nothing
as the absence of something
or the absence of everything.
And really this is how everyone
defines nothing, as a void.
But my father had
a different idea.
He had been thinking about
this for a while, he told me.
And the other day he
had had an epiphany.
He was at the mechanics
waiting for his car to be fixed
and it dawned on him that
you could define nothing
as "an infinite, unbounded,
homogeneous state."
So a state of
utter sameness that
extends, without bound, forever.
And this wasn't
a semantic trick.
An infinite,
unbounded, homogeneous
state would literally be
indistinguishable from a void.
It's nothing.
But my father thought it was
an interesting definition
because it defined
nothing not in terms
of what it isn't but
in terms of what it is.
And so he explained
all this to me
over a plate of cashew chicken.
And then he asked
me, do you think
this could help explain
how the universe began?
Now you have to bear in mind,
I'm his teenage daughter.
I was not exactly the
most well-behaved kid.
I would not be
described as studious.
I was failing math class.
I was not even
taking physics class.
I had opted for
meteorology because that
was what my high school
offered in place of physics
for the underachievers.
And here my father is asking
me how the universe began.
And he just sort of shrugged
like it was a normal thing
to do and said, I think
we should figure it out.
And so that is how,
at 15 years old,
I found myself on a
mission to figure out
the origin of the universe.
So my father and I started
teaching ourselves physics.
We stayed up late
every night, we
started amassing a crazy
collection of physics books,
reading everything we
could get our hands on,
and talking about
all these ideas
until my mother would
yell at us to go to bed.
Because if you want to
understand this something that
came from nothing when
the universe was born,
you have to look at
both sides of the coin.
So my father had already thought
long and hard about the nothing
part, and now we needed to
understand the something.
And that's what physics is.
Incidentally, before I
started this secret project
with my dad, I had no
idea what physics was.
I didn't take physics class
because I thought that physics
was like a set of
rules and numbers
for describing how
levers and pulleys work.
And now I know that
physics is about uncovering
the reality behind appearances.
It's about glimpsing this
deep and hidden architecture
of existence itself.
It's about embracing the
fact that the world is not
what it seems and that
everything is stranger
and simpler than we can
imagine, and yet comprehensible.
And I think if I had
known that from the start,
I wouldn't have
taken meteorology.
But eventually I
graduated high school,
and I move to New
York City for college.
And then when I
finish college I did
what any physics-loving,
amateur reality hunter would do,
and I took a job at
a bridal magazine.
So I was working as an
assistant at "Manhattan Bride."
And I was there in the
office, which was really
just the one-bedroom apartment
of a guy named Rick, when
I read an article in
"The New York Times"
announcing this huge physics
conference that was going
to be happening in
Princeton, New Jersey
called Science and
Ultimate Reality.
And all the world's
leading physicists
were going to gather there
to talk about their most
cutting-edge ideas.
So I'm reading this
article and a light bulb
goes off over my head.
I wait until Rick
leaves for lunch
and then I pick up the
phone, I call the people
in charge of publicity
for the conference,
and in the most
professional voice
that I can muster I lie and
say that I am a journalist
and that I'm calling
from "Manhattan
Magazine," because
that sounded better,
and that I wanted to
come cover the event.
Oh, of course, we would
love you to come, they said.
Great, I said, put
me down plus one.
Now in that moment,
I had no idea
how that one little
lie would forever
alter the course of my life.
But I called my dad and
I said, pack your bags,
we're going to Princeton.
So my dad and I
show up in Princeton
and we crash this
physics conference,
posing as journalists.
We found our press badges
at the press table.
Mine said "Manhattan Magazine,"
I had a blank for my plus one.
And we put them around our
necks and just wandered
amongst our heroes
like two idiot deer
caught in genius headlights.
We got to listen to
these physicists lecture
about their most recent ideas
about the nature of reality.
And then, as if that
wasn't good enough,
we got to go into this
magical little room
that they call the press
room, where you sit down
and they deliver
to you, one by one,
each physicist so you
can ask them questions.
It was the most amazing
experience of my entire life.
And when the conference
let out, my father and I
just sort of wandered
through the town of Princeton
in a daze, talking about
everything we had just heard.
And eventually we
found ourselves
on Mercer Street, which
is the street where
Einstein had lived.
And we found his
house at 112 Mercer.
It was undergoing some
sort of construction,
so it was sort of cordoned
by yellow tape like a murder
scene.
But we just stood there
in awe, trespassing
on Einstein's lawn, two bogus
press badges still hanging
around our necks.
And it struck me then that
this little private hobby
that I shared with
my dad was maybe
going to be something bigger.
And it also dawned
on me that I was not
ready to give up this journalism
front because it was just
too good to be true.
All you need is this press
badge and suddenly you
can learn physics directly
from the physicists.
I figured the "Manhattan
Magazine" scam wouldn't
work for long
because someone was
bound to look it up and
see that it didn't exist.
But I figured I would
use it one more time.
So when I got back to New
York I called an editor
at "Scientific American."
Again I lied and said that I was
a journalist at the "Manhattan
Magazine" and that I had
been to this conference
and that I wanted to
cover it, or write
an article about physics
for their magazine.
And miraculously he agreed.
So my article comes out
in "Scientific American."
And suddenly my fake
journalism career
has just morphed into a
real journalism career,
and I was able to use that
to sort of worm my way
into more situations
where I didn't belong.
So I'm sure you can see
Stephen Hawking there,
front and center.
And then there,
inexplicably, is me.
It was the perfect scam.
And at this
particular conference
I ended up meeting an editor
from "New Scientist" magazine.
We struck up a
conversation, and I
mentioned that I wrote
for "Scientific American."
I didn't mention
it was only once
and it was the only
article I'd ever done.
And he suggested maybe I should
write for "New Scientist."
And so I started writing
articles for "New Scientist."
And then when I turned
25 "New Scientist"
asked me to be an
editor there, landing
me the ultimate
permanent press badge.
So once I was an editor at
a major science magazine,
I had access to everything
that my father and I needed
to learn physics and
start to figure out
the origin of the universe,
which was the whole point.
And I was learning
so much, trying
to come to grips with this
something that supposedly arose
from nothing 14
billion years ago.
And if you try to learn
all of fundamental physics
from scratch, not only
is it a lot to learn
but it can seem like a lot
of crazy, unrelated facts.
But early on I had
an epiphany that
made it infinitely easier
to connect the dots
and to see the big picture.
And so I think if
you want to know
one thing about
fundamental physics,
this is the one thing to know.
Something is only real
if it's invariant.
And I'll explain
what that means.
Something is only
real if it remains
unchanged in every
reference frame.
If it changes or disappears
from some perspective,
then it's not ultimately real.
And actually, even though
this is a very deep idea,
it's something that we all
sort of know intuitively.
Like if you were
sitting in your lobby
and out of the corner of your
eye you saw an elephant walk
by, even for Google that
would be pretty unusual.
And you might find
yourself wondering,
is that elephant real or am I
having some kind of break down.
And instinctively
you know there are
two strategies that you
can use to find out.
So the first would be to get
up, walk over to the elephant,
and just walk in a circle around
it, eyeing it from every angle,
suspiciously.
Because you know that if at
some angle it just vanishes,
then it was something
more like a mirage
and less like a mammal.
And the other
strategy you can use
is to just turn to the
Googler next to you
and say, do you see
that elephant too.
And if she says, no,
or just stares at you
blankly, then you know
that you should probably
go see a neurologist.
And why do you know that?
Because you know that
something is only real
if it remains invariant
in every reference frame.
OK.
So just because something's
not ultimately real
it doesn't mean it has to
be a hallucination, right?
Take a rainbow.
Is a rainbow real?
Not really, right?
It's not subjective.
It's not a hallucination.
But it's also not a physical
object hanging in the sky.
You can't go touch it.
Because it's a product
of your reference frame.
You see a rainbow
when you're standing
in just the right spot
and the sun's streaming
in from behind you,
and the light's
being refracted by the
moisture in the air.
And if you ask the
guy next to you,
do you see that rainbow too,
he'll probably say, yes.
But if you run the test of
walking around it in a circle,
you will eventually
see it disappear.
Because it's not invariant.
It's not ultimately real.
It's not a fundamental
ingredient of ultimate reality.
And so if you want to find
the fundamental ingredients
of ultimate reality,
the something that
arose from nothing, you have
to find what's invariant.
So if there's one thing that
you remember about physics,
let it be that.
It was Einstein who
first recognized
this link between
invariance and reality.
And I would actually
argue that this
was Einstein's single greatest
contribution to physics, which
I realize is a very
bold statement.
He did a lot of things-- special
relativity, general relativity.
That's not even what he
won the Nobel Prize for.
He won it for the
photoelectric effect.
Which is just so badass,
if you think about it.
Because the thing he
won the Nobel Prize
for barely cracks the list of
the best things he ever did.
But the best thing
he ever did was
to illuminate this link
between invariance and reality.
Because it set the future
trajectory of modern physics
in motion.
And it changed
physics from being
a set of rules and
numbers that describe
how levers and pulleys
work to being a way
to glimpse the reality
behind appearances.
And there's a good reason
that no one before Einstein
thought of this link between
invariance and reality.
And it's that before
Einstein, everyone
shared the same reference frame.
So in a Newtonian universe
the speed of light
is instantaneous, which means
everyone sees the same thing.
So everything's invariant.
And in Einstein's universe
this is no longer true.
So Einstein realized that
in order for every observer
to see the same laws of
physics, every observer
has to measure the speed
of light to be the same.
And so it doesn't
matter if you're
running a million miles an
hour or you're standing still.
As you measure a beam of
light, that beam of light's
going to be moving at
186,000 miles per second.
And what's important about that
number is that it's finite.
Light does not travel
instantaneously.
It takes time.
Light from the sun takes
eight minutes to reach us.
Light from distant galaxies
takes millions or even
billions of years.
And so looking out
into the universe
is a way of looking
back in time.
But the point is you
can't see everything.
The universe you can see
is bounded by the fact
that light has only had 14
billion years to reach you.
And so beyond that the
universe for you is dark.
Now the boundary that marks the
very edge of what you can see
is called your horizon.
And it's uniquely yours.
You are sitting at the center
of a sphere that encompasses
your one-of-a-kind universe.
And the person next
to you is sitting
at the central of
a different sphere.
Now they mostly overlap,
but not entirely.
And so Einstein realized
that in a universe
with a finite speed of
light, every observer
occupies a unique
reference frame.
So you can no longer just
describe the universe
without first
specifying from who's
frame you're describing it.
Because things might look
very different from one
frame to another.
And if things look very
different from one frame
to another, this introduces
a fundamentally new problem.
How do you know which
things are real?
And Einstein figured
out the solution.
Something is real if it's
invariant in every reference
frame.
So it was this way of
thinking that led Einstein
to his famous discovery.
By analyzing how things
look from different frames,
he was able to see that
space and time, which
everyone had always assumed were
the same for every observer,
are in fact not the
same for every observer.
They look different from one
reference frame to another.
So what I see as space, you
might experience as time.
And vice versa.
And so space and time
are not invariant.
They are relative to
your reference frame.
That's what relativity is.
But he found that
there is something
that remains invariant.
And that is this combination
of space and time.
This unified
four-dimensional spacetime.
So we might disagree on
measurements of space
or of time, but
everyone will always
agree on measurements of
this combined spacetime.
OK.
So space and time are not
real, spacetime is real.
And everyone always
focuses on the first part
because it's really
mind-blowing,
that space and time aren't real.
But Einstein actually cared
more about the second part.
Because he knew that the key
to finding ultimate reality
is to find the invariant.
And actually later
in life he said
that he regretted calling
it the theory of relativity
and wished that
instead he had called
it the theory of invariance.
So once we knew all
this, my father and I
now had a concrete plan.
The question, what
is ultimately real,
what is the something
that arose from nothing,
it was no longer this vague
philosophical question.
It was a rigorous
physics question.
What is invariant?
And so we were out to
breakfast at a pancake house,
and we wrote a list of possible
ingredients of ultimate reality
on a napkin.
So things like spacetime,
dimensionality, particles,
strings, et cetera.
This image, by the
way, is a recreation.
The original napkin
was eventually lost
or possibly sneezed in.
But we made this list, and then
I used my journalism career
to investigate each one.
And I want to tell you about
two of the items on the napkin.
So the first one is particles.
Particles seem
pretty fundamental.
If you ask, what is all the
stuff in the universe made of,
particles is the obvious answer.
That's what I thought,
until I encountered
the work of Stephen Hawking.
So I have to confess something.
When I was first learning
all of this stuff,
I had this suspicion that
Stephen Hawking was overrated.
I just wasn't convinced that
his contribution to physics
could be proportionate
to his fame.
Because there's just
something about a guy that
speaks in a computer voice
that sort of automatically
sounds like a genius.
He automatically
sounds like he knows
something no one else
could possibly know.
But as I studied
his work, I learned
that he had done this remarkable
calculation in the 1970s.
Actually he was annoyed
at another physicist,
and so he was doing this
calculation in order
to show that this
other guy was wrong.
And the calculation
proved three things.
First, that revenge is an
excellent fuel for genius.
Second, that I was an idiot.
Because if anything,
Hawking is underrated.
His physics is brilliant.
And the only thing
that's disproportionate
is the fact that everyone
knows who Stephen Hawking is,
but if you ask them,
what did he actually
do that was so important,
hardly anyone knows.
But now you guys will
know, because I'll
tell you the third thing.
His calculation proved
that particles are not
ultimately real.
And here's why.
So thanks to quantum
mechanics, empty space
is not really empty.
The uncertainty principle
tells us there's
a trade-off between
time and energy, which
means that on incredibly
short time scales--
a fraction of a
fraction of a fraction
of a second-- large
amounts of energy
can bubble up out
of empty space.
And this energy takes
the form of pairs
of particles and antiparticles
that emerged from empty space
and then meet and annihilate
and in the blink of an eye,
disappear.
And this is happening
all the time
all around us, these
particles and antiparticles
emerging, meeting,
annihilating, and disappearing.
But it happens so
quickly that we just
refer to them as
virtual particles.
But when Hawking was
doing this calculation
he realized that
something different
happens when you have a horizon.
And so, as you already
know, a horizon
marks an edge beyond which
light can't reach an observer.
So we talked about
the horizon that
surrounds your unique universe.
And there's an analogous
kind of horizon--
it's actually a mathematically
equivalent kind of horizon--
that surrounds a black hole.
So in this case the
horizon marks the edge
beyond which light can't escape
gravity's clutches in order
to reach an observer
on the outside.
So if you're standing
outside the black hole,
the horizon marks the
edge of what you can see.
So Hawking realized
that if these pairs
of particles-- virtual
particles and antiparticles--
are bubbling up out of
empty space in the vicinity
of a horizon, something
sort of amazing can happen.
The horizon can
separate the pairs.
So that where one particle
is just outside the horizon,
its antiparticle partner can
be just inside the black hole.
And now they can no
longer annihilate.
And so instead of disappearing
they just stick around.
These virtual particles
are not so virtual anymore.
They're actually totally
normal particles.
They're exactly the
same as the particles
that make up anything
in this room.
You could collect a bunch
of them and build a chair.
But there would be something
really weird about that chair.
Because it would owe its
existence to the horizon,
but the horizon's
not a real thing.
The horizon is not like a brick
wall that's floating in space.
The horizon's like a rainbow.
It's a product of
a reference frame.
Namely, the reference
frame of an observer who
is lucky enough to remain
outside the black hole.
And textbooks tend to call the
observer outside the black hole
Bob.
I like to call him Safe.
There's another kind of
observer who is not so lucky.
An observer who's in
inertial motion-- free-fall--
can't escape gravity's
clutches and falls straight
through the horizon and
into the black hole.
And I like to call him Screwed.
So from Safe's point of view,
these once-virtual particles
that can no longer annihilate
with their partners
are streaming out
from the horizon,
as if the black
hole is radiating.
That's why we call
it Hawking radiation.
But for Screwed,
there is no horizon.
He just falls straight
through, and there's
no edge of what he can see.
So for Screwed, these
virtual particles
just continue to annihilate
and disappear like always.
And so where Safe sees this
stream of hot particles,
Screwed just sees
ordinary empty space.
So you see what's
happening here.
The particles are not invariant.
And that's what Hawking
discovered that's so important.
Particles are not
ultimately real.
They're a product of
your reference frame.
Not only in the
vicinity of a black hole
but everywhere,
because every one of us
is surrounded by a horizon.
So my father and I crossed
particles off the list
on the napkin.
Now Hawking's
discovery has driven,
and continues to drive,
theoretical physics forward
for the last four decades.
Because it's rife
with paradoxes.
And there is nothing
that a physicist
loves more than a paradox.
And I'll give you an example.
So let's take our
elephant from the lobby
and throw him into a black hole.
All right, there he goes.
So Safe is watching
this from afar.
And so we can ask,
in Safe's reference
frame, what does this look like.
And fair warning,
It's not pretty.
So from Safe's point
of view, the elephant
is going to fall
towards the black hole
and then encounter this stream
of hot Hawking radiation.
And he's going to
be burned to a crisp
before he ever
crosses the horizon.
And his ashes will just
emanate back into the universe.
OK.
So that gruesome and terrible.
But we can also look at
Screwed's point of view.
Because Screwed is
just falling straight
through alongside the elephant.
And for Screwed
there is no horizon.
So there are no hot particles
to harm any animals.
And so for Screwed,
the elephant is just
in ordinary empty space.
And he can live out
the rest of life
until he eventually reaches
the center of the black hole.
So there's a problem.
The laws of physics require that
both of these stories be true.
If either one of
them were not true,
you'd violate a law of physics.
And so the elephant has to be
both dead in a pile of ashes
outside the black hole and alive
and well inside the black hole.
That alone is just weird.
But the problem comes
in because there's
another law of physics
that's equally as
fundamental as the others
that says you can't have
two copies of the same elephant.
So both stories have to be true,
and both stories can't be true.
That's the paradox.
And it was a physicist
named Lenny Susskind
who solved this paradox.
He said, as long as you stick to
one observer's reference frame,
as long as you talk about the
Safe sees or what Screwed sees,
all the laws of
physics remain intact.
It's only when you try to talk
about their points of view
simultaneously that
you see these two
illegal copies of the elephant.
So it's this picture
that's the problem.
Einstein had said, if you
describe the universe,
you have to first specify
your reference frame.
And the fact is this is an
unphysical reference frame.
It's impossible.
There's no one who can see
inside and outside a horizon
simultaneously.
That's the idea of a horizon.
And so as long as we just
stick to physical reference
frames, what an observer
could actually see,
we never see two
copies of the elephant.
And all the laws of
physics remain intact.
So the problem is solved.
But there's still something
very unsettling about that.
Because we would like
to think that there's
some actual answer
to the question,
where is the elephant?
Is the elephant dead
outside the black hole
or alive inside the black hole.
We like to think that
there's some real answer.
And what this is telling
us is that there's not.
So Susskind realized
that the location
of the elephant in
spacetime is not invariant.
So spacetime-- this unified,
four-dimensional spacetime
that was left invariant
by Einstein's theory
of invariance-- turns out not
to be invariant after all.
And so my dad and I had to
cross spacetime off the list.
So we continued our search for
these ever-elusive invariants,
these fundamental ingredients
of ultimate reality.
I was running around
the world having
fascinating conversations with
these brilliant physicists
and usually making a total
fool of myself in the process.
And often my dad
was there with me.
And when he couldn't be,
I would report back to him
and detail all of my crazy
adventures and everything
I had learned.
But looking back on this
17-year journey, here's
what I realize now.
If it weren't for
my father I would've
never done any of this.
Even if I had somehow
become interested in physics
on my own, I would've
never crashed
a conference posing
as a journalist.
I would have never
turned one little lie
into an entire career.
Because without my
dad there at my side
or on the other
end of the phone,
it wouldn't have been fun and
it wouldn't have meant anything.
And that's the thing
about invariance.
It doesn't just make objects
real, it makes our lives real.
And I really think that's
why we need other people.
We need them because they
bear witness to our lives.
And in doing so, they
anchor us to the world.
They anchor us to a reality that
can be seen from every angle
when you walk around it.
I needed my dad because
that second reference frame
gave my life a
sense of invariance
and created between
us a shared reality.
So that every time I learned
something deep and wondrous
about the universe, I could
turn to my dad and say,
do you see that too.
And he could smile back
at me and say, yes.
But just as we were
creating this shared reality
we were also chipping
away at it piece by piece
as we crossed item after
item off the napkin,
slowly undermining the very
notion of a shared reality.
Because once you know this
one thing about physics,
that what's real is
what's invariant,
the entire trajectory of
physics snaps into focus.
The whole history of
physics, from Einstein
to exactly what's
going on right now,
has been a steady and relentless
progression of invariant
after invariant giving
way to observer dependence
and illusion.
And so the list of fundamental
ingredients of reality
is getting shorter and
shorter and shorter.
And so we can ask, where
does this trajectory end.
Does it end with one fundamental
ingredient, one invariant, one
thing that everything
else is made of?
Well, that used to be the hope.
A lot of people thought that.
That was sort of the
idea of string theory.
That all these different
things, all this variety
we see in the world,
is actually all just
made up of this one ingredient,
these little vibrating strings.
But the most exciting and
interesting and challenging
thing that's happened in
string theory in recent years
is that it's turned out that
strings are not invariant.
And so physicists are starting
to think that maybe there's
not one fundamental ingredient.
So where does the
trajectory end?
Does it end at nothing?
Because here's the interesting
thing about nothing.
If you think about
it not in terms
of what it isn't but
in terms of what it is,
an infinite, unbounded
homogeneous state
is by definition invariant in
every possible reference frame.
So my dad had started with this
sort of existential question
of, how do you get
something from nothing?
And now everything
we were learning
was presenting us with
the very real possibility
that that something might
not be made of anything.
That the something
might be nothing.
And on the one hand,
that's really good news.
Because that actually
offers a possible solution
to this ancient
existential riddle.
But on the other hand, it's kind
of a bummer when you've just
spent 17 years trying
to create a shared
reality with your
father, only to learn
that there may be no such thing.
Physics taught me that I
have my reference frame
and my dad has his
reference frame.
And they mostly overlap,
but not entirely.
Which I think is
just another way
to say that over
the past 17 years,
physics has taught me
what it means to grow up.
But still I am comforted to
know that there is a reference
frame in which we are together,
side by side, my dad and me.
And that's the
reference frame that
sits between the
covers of my book.
So thank you very much.
[APPLAUSE]
I can take questions,
if anyone has.
AUDIENCE: What's
a good suggestion
for getting our daughters
involved in math and science?
You have a chance to
speak with a lot of people
who have made this
be their profession.
And from their
experience and yours,
what do you think is
a good first step?
AMANDA GEFTER: So I think it
depends on personality a lot.
So for me, I was sort
of this rebellious kid.
And I think if physics
had been presented
to me in any normal way,
like as something you
have to study in
school, I just don't
think it would have ever
captured my imagination.
I think it was the fact
that my dad presented it
as this secret thing
that we were going to do,
and it was this
mission and we were
going to figure out the
origin of the universe.
And it felt like
by doing physics
I was rebelling in some way.
Actually, I've thought
about this a lot.
I think physics is a very
inherently rebellious subject.
Because it requires you
to question everything
we think we know about reality.
And if you look at the
greatest physicists of all time
they tend to be very
rebellious characters.
So I think it's a shame because
a lot of times the people who
are encouraged to go
into science and math
tend to be the very studious
people who go by the book.
And you need that,
but that's not always
going to be the most
creative thinkers.
And I think sometimes we weed
out creative thinkers who
could have really
contributed to physics
by not appealing to
that type of kid.
But I realize not
everyone's going
to go on a secret
mission for 17 years
to figure out the
nature of the universe.
So I really think
the physics that's
taught in school-- you don't
get to the really good stuff
until you've already committed.
You do Newtonian
physics in high school,
and then it's not until-- if
you did physics in college,
you'll start to get into
relativity and quantum
mechanics.
And that's where it
gets really cool.
But I think you could actually
present those topics to kids
without needing a crazy amount
of math that they don't have.
And so I think if
there was a way
to present the cooler parts
of physics, the really
exciting, mind-blowing stuff
earlier on-- so that they would
see that, OK, I have to get
through all this other stuff,
but it's going to be really
good-- I feel like people
would be more into it that way.
AUDIENCE: Hi.
So I'm actually about 50%
through your book right now.
And I have this
problem when reading
these sort of theoretical
physics books.
Which is that I usually follow
through special relativity
and general
relativity, but once I
get to sections about
supersymmetry and string theory
and things like that, I
just stop understanding.
And you actually talk a little
bit about this in your book,
that part of the problem here is
that these descriptions aren't
actually accurate.
Because really they're
just describing
these mathematical equations.
So is it impossible to
understand this stuff
without understanding
the math involved?
Or is this something
that you encountered
when you were learning this?
At some point did you just
say, wow, I didn't take physics
but now I have to learn
differential equations just
to even understand this at all?
AMANDA GEFTER: That's
a really good question.
And I sort of
struggled with this.
Because there definitely
were times where I was like,
oh my god.
I'm reading through
these papers and I'm
like, if I knew this math,
this would be a lot easier.
And I think it's true,
what you were referring to,
this idea that physics is
expressed in mathematics.
And then if you try to
translate that into English,
there's not a
one-to-one correlation
between English and math.
And so something is inevitably
lost in the translation.
And science writers tend
to rely a lot on metaphors.
And so now you're
almost at another level
where you're losing a little
bit of something else.
It might make it easier
to sort of understand,
but on the other hand you're
losing more of the nuance.
And so you might say you
can't really understand it
unless you understand the math.
But on the other hand--
the joke that the meaning
of life, the universe,
and everything
is 42, the reason
that's funny-- why
is 42 not a satisfying answer?
Because you want an
answer in English.
A number wouldn't be
the answer, because we
want to know what it means.
And so the math doesn't tell
you what anything means.
And so even though you lose
something in the translation,
you gain a sense of meaning.
And a lot of physics
is really based
on principles and having
these foundational principles
and then deriving
the math from that.
And that's how Einstein worked.
And so you can understand
all the principles
without understanding
the particular solutions
of equations.
And so I think you actually
can have a complete big picture
understanding, even
if you can't sit down
and actually do a
particular problem.
AUDIENCE: So my understanding
of string theory-- by the way,
I really enjoyed your talk-- my
understanding of string theory
is a little bit outdated.
Why are strings not invariant?
AMANDA GEFTER: Yeah,
great question.
So there was a period
of time where everyone
was hoping that
that was the case.
And then physicists
realized they
had five different
versions of string theory
that were all
completely consistent.
And so this was sort of an
embarrassment of riches.
You don't want five
theories of everything,
you want one theory
of everything.
And so this was
sort of a crisis.
And Ed Witten came
along, and he realized
that actually these
five string theories,
even though they
look very different,
are all mathematically
equivalent.
There are
transformations that you
can make to go from
one to another.
And that's really unexpected.
Because you have a theory
with strings vibrating
in 10 dimensions,
and then you have
a theory of these
membranes in 11 dimensions,
and then you have particles.
And you have radically
different spacetime geometries
and what would look to us
like drastically different
physical worlds.
And they're actually all
descriptions of the same thing.
And so people refer to that
as the second superstring
revolution.
And that was considered
this amazing step.
Because, oh, we don't
really have five theories,
we have one theory.
And now we'll call it M-theory.
And that's great.
But what M-theory
is telling you is
that things like dimensionality
and strings are not invariant.
Because what look like
strings in one point of view,
one of these theories, look
like particles in another.
And they look like
membranes in another.
And what looks like
10 dimensions in one
is 11 dimensions in another.
And it's not like one's
right and one's wrong.
It's just that there
are two different ways
of looking at the
exact same thing.
And so now M-theory
basically undermined the idea
that you can have an invariant
fundamental ingredient.
AUDIENCE: I was snooping
at your bookshelf,
so I know you've run
into a couple of these.
And I'm not going to
remember the guys' names,
but there are a couple people
who look at the evolving
contradictions
and-- if you wind up
proving that nothing is real--
If all of our particles that
make up us in this room right
now originated as Hawking
radiation, so there's some
frame of reference from which
absolutely nothing is
real, that you sort of
need to find another
kind of answer to things.
I think of that as sort of like
Godel's notion of completeness
and being able to prove
the system is complete.
So you've got the guy who thinks
that the entire universe is
a cellular automata.
And then there's also the
thought experiment thing
that suggests that maybe
the entire universe is
a simulation in somebody
else's universe.
And I just wondered
what you thought
about those kind of notions.
AMANDA GEFTER: Yeah, so
they're all really interesting.
I think the same problems sort
of plague all of those ideas.
And the simulation question
is really interesting.
And it's actually
directly related
to Godel's
incompleteness theorem.
Because the main
conceptual difficulty
in talking about the
universe as a whole,
especially when you have
to apply quantum mechanics
to the universe as
a whole, is the fact
that unlike anything
else that we know of,
the universe only has an inside.
It doesn't have an outside.
It's like a one-sided coin.
And so you can't have an
observer outside the universe.
The universe is this set
that contains itself.
You get into these
weird paradoxes.
And there's no way
for an observer
to describe the universe without
it being self-referential
in some sense,
because the observer's
part of the universe.
And so with the
simulation question,
you're saying, what if this
whole universe is actually
a simulation embedded on
a computer in some higher
reality.
Well, for one
thing, I don't know
that it would matter that much.
There would still be some
fundamental laws of physics
that I really believe you
would be able to figure out.
But in order to assess
the reality of reality,
you have to step outside of it.
So to know that you
were a simulation,
you'd have to be
outside the simulation.
And then how do you know
that that's not a simulation.
You'd have to be
outside of that.
And so it's again
this question of,
what is your reference frame.
Because by definition you
can't be outside reality.
And so there is
no reference frame
from which you can determine
the reality of reality.
I don't know if that totally
answers your question,
but I think all of these
issues that you're raising
are very related.
And Stephen Wolfram's theory
that you were referring to
is really interesting.
I don't really
know it well enough
to comment that
intelligibly, but it's
going to be subject
to the same issues
that we're talking about here.
Because it's another
way of doing things,
but it still has to replicate
all of physics as we know it.
And so it's going to run
into these same questions.
Anyone else?
AUDIENCE: One more question, but
I want to see if it make sense.
Because this stuff's amazing
but also makes my head spin.
You said there is a
trajectory and what
is invariant's become
smaller and smaller,
and it may be nothing.
But what is the endgame?
Obviously there's an
endgame for people
that study this and are amazed
by it and everything else.
But for someone who doesn't
have this understanding--
and if there is an endgame where
it does become figured out,
what effect could it have
on people outside of just
in theory?
AMANDA GEFTER: Probably none.
[LAUGHTER]
I don't think it's going to
have technological applications.
You never know, right?
You never know.
You can never see
these things coming.
I think this is really
just about answering
deep existential questions
that humans have been asking
for as long as there
have been humans.
The question of what is real,
what am I, how am I here,
what am I seeing?
I think it's just things
that we deeply want to know.
And it's funny because
on the one hand
it seems incredibly abstract,
especially if you're
talking about 14
billion years ago
and the origin of the universe.
Or the cosmos, which is so huge.
And quantum mechanics,
which the scale is so tiny.
And you can't place
yourself in these things.
But I always have
these moments where--
because I start thinking about
this stuff and I kind of start
taking it for
granted a little bit.
And then all of a sudden
I'll have this moment
where I'm like, oh my
god, I'm talking about,
literally, this isn't real.
I'm talking about the
stuff right here and me
and all of us.
And so it's not that abstract.
It's just you can't really live
your life thinking about it
every minute like that, or else
you're going to have a problem.
I think any time you have a
better understanding of the way
that nature works it's
going to have some effect.
It's going to be
useful in some way.
But when you get to this
level, will it be practical?
Probably not.
AUDIENCE: Sorry for
being a stick in the mud,
but if strings aren't
invariant, are there
any invariants in M-theory?
There are not that
anyone knows of.
And it's really
interesting because when
I've talked to
string theorists--
string theorists
will say things like,
we don't really know
what the theory is.
We have all these equations,
we have the theory,
but we don't know
what it's a theory of.
And what they mean by
that is quantum field
theory is the theory
of quantum fields,
string theory was the
theory of strings.
M-theory, they don't know.
They have this
theory and they don't
know what it's describing.
There's no basic ontology there.
And they're well aware of that.
They see it as either
something will emerge
and there will be
something that it's
describing that we
just don't realize yet.
I happen to think it's actually
more useful if there's not
an ontology there.
Because now you can
answer this question
of how you get
something from nothing.
It's really fascinating.
M-theory-- if you read physics
books, everything you read
will say, nobody knows
what the M stands for.
Maybe it stands for
mystery or mother or magic.
There was a Nobel
Prize winner who said,
it's the upside
down W for Witten.
And people had all
these theories.
You read Stephen
Hawking's book and it's
like, no one knows
what the M stands for.
And I'm like, how
can no one know?
Ed Witten coined it,
and he's still alive.
Why doesn't someone
just ask him?
So I went and I asked him.
And he was like, it
stands for membrane.
I originally said, oh, it
could be mother or mystery
or whatever, but I was kidding.
And nobody really got the joke.
But so the M stands
for membrane.
But membranes are not
invariant in that theory.
And so there's a deeper
point to the no one
knows what M stands for, which
is even though literally it
stands for membrane,
I think part
of what that means is they don't
know what it's a theory of.
Which has never really happened.
It's a weird way
of doing physics.
But fascinating.
All right, thank you
guys so much for coming.
[APPLAUSE]
