The following podcast contains some graphic descriptions which some listeners might find upsetting.

In a disused squash court buried beneath an old football stadium in the center of Chicago,

the world's first nuclear reactor lies in weight.

25 feet wide, the size of a two-car garage, it resembles a giant black egg, haphazardly propped up by

wooden scaffolding. This is pile one.

A team of physicist has been working for nearly a year to get to this point.

Hard, dirty work.

Every surface is slippery with a coating of graphite. The light is dim underground and the scientists

are almost invisible except for the occasional flash of eyes or teeth.

Forty tons of graphite have been cut and drilled to follow Leo Salard's carefully designed lattice pattern and assembled under Enrico Ferme's precise direction.

Tiny uranium orbs dot the structure, which is intersected with long cadmium

control rods placed to absorb stray neutrons and prevent meltdown.

On the 1st of December, 1942, the scientist lay the 57th layer of bricks. Fermei checks calculations on his slide rule and confirms.

Tomorrow, pile one will be ready to test.

Nearby and Eckhart Hall, an old Gothic style building near the central quadrangle of the University of Chicago,

Leo Zalard gets up from his desk.

He wraps his coat tightly around his short round flame guarding against the bitter cold of the

Chicago winter.

What his colleagues are building in the squash court is not a bomb, but an experiment designed to do exactly what a bomb does.

It will trigger a nuclear chain reaction, the very first in human history.

If Salard and Fermi's calculations are off,

they will likely all die,

...