I'm Steve Strogatz, and this is The Joy of Why, a podcast from Quantum Magazine that takes you into some of the biggest unanswered questions in math and science today.

If you've ever wondered, what are we actually made of?

You probably found yourself going down a rabbit hole of discoveries.

Just like other living things, of course, we're made of

cells, and cells in turn are made of molecules and molecules are made of atoms. Dig even deeper,

and pretty soon you'll find yourself at the level of electrons and quarks. These are the

particles that have traditionally been considered to be the end of the line, the fundamental building blocks

of matter.

But today, we know that's not really the case.

Instead, physicists tell us that at the deepest level, everything is made up of mysterious

entities, fluid-like substances that we call quantum fields.

These invisible fields sometimes act like particles, sometimes like waves.

They can interact with one another. They can even, some of them, flow right through us.

The theory of quantum fields is arguably the most successful scientific theory of all time.

In some cases, it makes predictions that agree with experiments to an astonishing

12 decimal places. On top of that, quantum field theory has also been shedding enormous light

on certain questions in pure mathematics, especially in the study of four-dimensional shapes

and even higher dimensional spaces. Yet, there's also reason to believe that quantum field theory is missing something.

It seems to be mathematically incomplete, leaving us with many unanswered questions.

Joining me now to discuss all this is Professor David Tong.

David is a theoretical physicist at the University of Cambridge.

His specialty is quantum field theory, and he's also renowned as an exceptionally gifted teacher

...