Brian, welcome to the show.

Thank you so much.

The elegant universe turns 25 this year, just like me.

I wish I could say that about myself.

I'd like to get into what's changed where we're at,

but I think it's going to require starting with the question

that I'm sure you've never been asked before.

What is string theory?

Yes, good question.

There are a number of ways of framing what string theory is about,

but perhaps from the largest perspective,

it's an attempt to realize a dream that really begins with Albert Einstein,

which is this idea that we have a single universe. So we should

have a single theoretical explanation for how that universe works. And that single explanation should be

mathematical. And so there should be some grand mathematical formula, some mathematical equation

that would describe everything in the universe.

And Einstein sought this so-called unified theory for decades, but he never found it.

And string theory just may be the theory that Einstein was looking for.

Now, what kinds of problems is the scientific community faced with that leads them to come up

with something like string theory?

I mean, we already had a lot of ideas about what the universe was made of, the different

constituent particles and stuff.

...