[horn honking]
[siren wailing]
A city is like a brain.
It develops from a small center
and slowly grows and changes,
leaving many old parts
still functioning.
New York can't afford to
suspend its water supply
or its transportation system
while they're being replaced
by something more efficient.
Changes have to
happen piecemeal.
And that's how it
is for the brain.
There is no way for evolution
to rip out the ancient interior
of the brain because
of its imperfections
and replace it with something
of more modern manufacture.
The brain and the city both
must function continuously
during the renovation.
That's why our limbic
system is surrounded
by the cerebral cortex.
The old part is in charge of
too many vital mechanisms for it
to be replaced altogether.
So it's sometimes
counterproductive,
but that's a necessary
consequence of evolution.
The city is a gift of
the cerebral cortex.
But the brain's language is
not encoded in the DNA of genes
because the vocabulary
of life is too small.
Our brains need a language with
10,000 times as many words.
The information content of the
human brain expressed in bits
is probably comparable
to the total number
of connections
among the neurons,
about 1,000 trillion bits.
If all the contents
of your brain
were transcribed into
written language,
it would amount to
vastly more books
than are contained in the
largest libraries on Earth.
The equivalent of more
than 4 billion books
are inside your head.
The brain is a very big
place in a very small space.
It's written in those
neurons pioneered
by the undersea microbial mats.
These are tiny
electrochemical switching
elements, typically a few
hundredths of a millimeter
across.
Each of us has 86
billion neurons,
comparable to the number of
stars in the Milky Way galaxy.
The neurons and their parts,
axons, dendrites, synapses,
and the cell bodies themselves
make up a network in the brain.
Many neurons have
thousands of connections
with their neighbors.
Dendrites, those pathways
sent out by neurons
to connect with other neurons,
extend these nerve cells
to synapses until they
create a full-blown network
of consciousness.
[orchestral music]
The neurochemistry of the
brain is astonishingly busy,
the circuitry of a
machine more wonderful
than any devised by humans.
Your brain functions are due
to those 100 trillion neural
connections that make you you.
Your deepest feelings of love
and awe, those moments when we
glimpse the grandeur
of nature and all
the elegant architecture
of consciousness
are made possible by
those connections.
This is the essence of
emergence, tiny units of matter
operating collectively
to become something
much more than
themselves, to enable
the cosmos to know itself.
But there is a
vision of emergence
that takes it even higher.
Can we know the universe?
And will it ever
come to know us?
[dramatic music]
