It's moved forward inch by inch by inch.

Everything that's gone on has been

subsumed into a mass of common wisdom that you can draw upon.

I think I'm extraordinarily lucky to be able to just try

to answer these fundamental questions about what forms

the scaffolding for the galaxies that we see in our instruments.

What's this mystery invisible stuff that's making up

the deep sum of the universe?

If you go back to the early days of European exploration,

you have these famous maps where there's the limits of the known

land, and then there's dragons and monsters out there

in the terra incognita, where people don't really

know what's going on.

We are, in some sense, working off the map.

Theorists are the people who come up

with ideas of how the universe might work,

and experimentalists are the people who test them.

You know, humanity is a bootstrap.

If you have to think about all of the creative details that

led to the point that you're at, you'd

never be able to get that little step forward

that would be your own creative addition to it.

Einstein came up with his theory of general relativity, which

predicts, in principle, gravitational waves,

the oscillations of spacetime that carry energy

from distant collapsing pairs of black holes

that will send out these gravitational waves that were

just this last year, for the first time,

heard by the LIGO experiment.

So that's 100 years between the time someone

wrote down a theory and the time that one

of the particular ramifications of that theory

was identified and observed experimentally.

It would be wonderful if we could figure out

what dark matter is.

But so long as we keep finding really interesting new things

along the way, I really can't complain.

You keep butting your head against it.

And every once in a while, some person, usually

a young person looking at it for the first time,

turns the picture through 45 degrees

and sees it organized in a way that the person who'd

been looking at it all their life doesn't see it.

And that's when the breakthroughs occur,

and they're impossible to predict.

It's a wonderful thing to start out with first-year students,

and then you watch them over the years turn

into people who are really masters of the field who

can stand up with you at the chalkboard and say, no, no,

I disagree with you.

It works like this.

And then eventually, they start developing their own interests,

and start diverging from what you're doing,

and you no longer need to come up with projects for them

or steer them because they're striking out on their own.

[MUSIC PLAYING]