Transcriber: Carlos Arturo Morales Reviewer: Elisabeth Buffard
What makes a physical law fundamental?
How do we go about finding
the deepest and truest things about our universe?
For centuries, we, as physicists, have been attacking this
from the point of view of reductionism.
Reductionism is the idea
that I'll learn the truest and deepest things about the universe
by reducing things to their smallest bits.
So, for example, we've taken matter
and we've broken it down into smallest bits and we've found atoms.
And then we took the atoms, smashed them together,
broke them into pieces and found that atoms are made
of electrons and protons and neutrons.
And we didn't stop there,
we took the protons and the neutrons,
we smashed them into each other
and we found that they're made of quarks.
And we're still on the business of trying to find
all of these smallest particles of the universe.
Now, implicit in this idea that that's the way to find
the truest and deepest things about the universe,
implicit in that idea is the related idea
that I can then take those bits--
If I understand the smallest bits and how they work together,
maybe I can build them back up and reconstruct everything,
maybe I can get a theory of everything and then predict
what can be known about the universe.
Now, there's one problem
with that piece of the idea and that is,
that reductionism can't answer every question that needs to be
addressed. So, for example, here's the Mona Lisa,
and the Mona Lisa is smiling,
but she's smiling in kind of a subtle way.
She's smiling with her eyes.
Now, we can ask the question:
How did Leonardo Da Vinci make her smile with her eyes?
Now, reductionism gives you an idea of how to tackle that question.
Reductionism would say:
Okay, the way to tackle that question is to start with the colors.
Let's look at the colors with which she's painted
and let's do a chemical analysis on the pigments.
We'll break her into the smallest bits
and then we'll be able to build her back up.
Now, how many of you think
that by doing a chemical analysis of the pigments
we're going to find out why the Mona Lisa is smiling?
Yeah, I thought so.
So, there are certain questions that can not be addressed
with the reductionism philosophy. And, in fact,
the reductionism idea really is just a philosophy.
It was handed down to us by the Greeks.
It's a way of gaining knowledge that's gotten us a lot of mileage
but it can't necessarily be used to answer every question.
Now, when we're trying to address questions in science,
especially when we're after the questions of why did something happen,
why dit it happen this way, we're always looking for
the broadest explanation, the explanation with
the broadest explanatory power.
So, enter my field, condensed matter physics,
and we mean condensed in the sense of condensation,
that is, that gas condenses to liquid, liquid condenses to solid,
that type of condensation. So, we're really in the business
of phases of matter and phase transitions.
We also study what electrons do inside of solids.
It turns out that electrons inside of materials
have their own phases of matter and their own phase transitions.
And you're already somewhat familiar with this:
you know that a metal can carry electricity, it can carry current
and when it's doing that,
the electrons inside of the metal are flowing.
Now, something that flows is a liquid.
So the electrons inside of the metal are liquid.
But it's very different inside of an insulator like plastic.
Plastic doesn't have current flowed through it.
The electrons are stuck in there
and the electrons are solid like in that type of material.
So, electrons inside of materials have their own phases of matter,
their own phase transitions. And in fact, they have many,
many more phases of matter than just solid, liquid and gas,
and that's my field of research.
Now, one of the things that we've discovered
in condensed matter physics, in thinking about
these phases of matter and phase transitions,
is that when you're studying large scale behavior,
and you do need many, many particles
in order to observe the phase transition,
when you're studying collections of many particles,
often, there is behavior that presents itself
in the whole collection of particles, collective behavior,
that seems to be quite independent of the constituents.
And again, in answering the question of why,
we're always looking for the broadest explanation.
So, for example, this is my cat,
her name is Marshmallow
and I named her Marshmallow because she is sweet and fluffy.
And we could ask the question, why does she have fur, okay?
Is it A, because she is Marshmallow,
Is it B, because she is a cat,
or does she have fur because C, she is a mammal.
Now, we're looking for the broadest explanation
and in this case the broadest explanation is that she is a mammal
and mammals all have some type of fur.
Now, the same way, I can ask a question about physics.
And I can ask why is this rock hard, okay?
Well, a reductionist idea would say: Okay, tell me what's in the rock
and then I'll be able to tell you why is it hard.
What's in this rock, is calcium, and carbon, and oxygen, okay?
And so, the reductionist philosophy
will tell you that this is hard because it's made of calcium,
carbon, and oxygen. But there's a problem with that.
This rock is also hard
and there's no carbon in it; it's got sulfur in it instead.
So, it's not fair to say that this rock is hard
because it has carbon in it,
or that this rock is hard because it has sulfur in it.
There's something very similar
about the behavior of these hunks of matter
that transcends the actual individual atoms that make them up.
In fact, the reason that they're hard is because the atoms inside
have a regular periodicity to them,
they're in a crystaline structure
and that's the origin of the hardness.
It's not because this rock has carbon in it
or because this rock has sulfur in it.
There's a larger organizing principle at work.
Now, that's an example of what we call emergence.
Emergence is when behavior happens at a large scale,
at the scale of the collection of particles,
collective behavior that transcends
the individual particles that make it up.
And it's not just confined to physics.
People also have emergent behavior.
If you've been in a stadium and participated in a wave,
you've participated in a collective phenomenon
that was emergent, okay?
Now, one of the ways that you know you have
emergent collective behavior going on,
is that the behavior,
when it rises at the level of the collection of particles,
has some properties to it that are independent
of the individual constituents. So, for example, if the wave
is happening in a stadium, it doesn't matter whether
it's a baseball stadium in Boston
or a soccer stadium in Rio de Janeiro.
When the wave happens, it looks more or less the same.
And it doesn't matter whether the fans are tall
or whether they're short,
it doesn't matter exactly who showed up that date
and it doesn't matter what color they're wearing.
There's something about that wave
that transcends the individual people that are making it up.
In the same way, because it's an emergent phenomenon,
it's not fair to say that that wave--
It's not fair to say that all waves are due to people
standing up and sitting down at the right time.
The reason I know that's not the right explanation is because
I've seen waves in other contexts.
I've seen waves happen on water.
Right now, you're hearing my voice
because of compressional waves in the air
that are carrying the sounds to your ears. So, waves,
when they happen, all look more or less the same.
But there's something about the wave;
It's an emergent phenomenon
that transcends the individual particles that make it up.
Another way you can tell if you're dealing with an emergent phenomenon
is that, again, it transcends the building blocks that make it up.
So, for example, when you build a house
you can build a house out of brick,
or out of wood, or out of stone,
but it wouldn't be fair to walk into my home,
look at the floor plan and say, "Oh! Look how the kitchen
flows into the dining room ,
or how the dining room flows into the living room.
It must be because of the particular bricks they used."
That wouldn't quiet be correct, right?
The large scale structure of the house
transcends the actual bricks. I could use the same floor plan,
but make it out of bricks, or out of stone, or out of wood.
And that's another clue that you have emergent behavior happening.
Now, I think this idea of emergence
opens up some really interesting and deep philosophical questions,
deep questions even about who we really are as humans.
And now, I'm going to take off my physicist hat
and I just want to talk as one human to another.
I think this opens up, you know,
the interesting question of who really are you?
I hear our society having echoes of reductionism in it.
I hear the reductionist idea echoing around this TED says:
Well, we're really just a collection of atoms.
I'm made of atoms, I have DNA and the reductionist idea would say
that if I just understand your atoms and how they work together,
and if I just understand enough about your DNA,
not only can I predict
what height you'll be when you grow up,
and what color hair you'll have,
I can even predict who you'll be as a person
and why do you like ketchup or mustard, okay?
But that idea that you as a human
are determined by your atoms and by your DNA,
that's a reductionist idea!
And we already know that reductionism
didn't even work for this hunk of rock
because the rock is too large and it's too complex
to apply reductionism to it.
Well, you're large and you are complex,
larger and more complex than a rock.
So, that brings up the question in my mind
of what really are we? Are we reducible to our atoms?
Or are you just your atoms? Or, in the same way
that the Mona Lisa's smile transcends her pigments,
is it posible that the light in your eyes
trancends your atoms?
Are you just a collection of atoms and DNA?
Or are you more than your atoms?
Thank you. (Applauses)