Welcome to Quantum Magazine's podcast.

Each episode, we bring you stories about developments in science and mathematics.

I'm Susan Vallett.

No sooner had the radical equations of quantum mechanics been discovered when physicists identified one of the strangest phenomena the

theory allows, quantum tunneling.

It shows how profoundly particles like electrons differ from bigger things.

Throw a ball at the wall and it bounces backward.

Let it roll to the bottom of a valley and it stays there.

But a particle will occasionally hop through the wall.

Or as two physicists wrote in nature in 1928, it has a chance of slipping through the mountain

and escaping from the valley.

That's one of the earliest descriptions of quantum tunneling.

Physicists quickly saw that particles' ability to tunnel through barriers solved a lot of mysteries.

It explained various chemical bonds and radioactive decays and how hydrogen nuclei in the sun are able to overcome their mutual repulsion and fuse producing sunlight.

But physicists became curious. Mildly at first, then morbidly so. They wondered how long does it take for a particle to tunnel through a barrier? The trouble was,

the answer didn't make sense. The first tentative calculation of tunneling time appeared in print

in 1932. Ephraim Steinberg, a physicist at the University of Toronto, says earlier calculations may have been done in private.

I suspect a lot of the history is missing.

I think it's because these calculations aren't so hard,

but when you get an answer you can't make sense of, you probably don't publish it.

It wasn't until 1962 that a semiconductor engineer at Texas Instruments wrote a paper that explicitly

embraced the shocking implications of the math. His name was Thomas Hartman. Steinberg says

...