Nobody is answering the phones in Los Alamos.

It's July 1945.

The war in Europe is over, but in the Pacific the war rages on.

In most cases an unanswered phone would not be a particular cause for concern.

But to Leo Salard, the silence is ominous.

He suspects what no one is willing to confirm, that the Manhattan Project is getting ready for the first atomic bomb test. Robert J. Oppenheimer is a scientist in charge of overseeing Los Alamos.

He is responsible for designing a bomb and making sure it works.

Some of the most brilliant minds in the world have been working on this bomb. They've achieved some of the quickest scientific advances in history.

In theory, the bomb should work perfectly.

But until now, the preliminary tests of the individual components have failed.

Like a Russian doll, the bomb is built in layers. The most highly combustible substance is at the core. It's at the core that those first neutrons are fired that cause fission and a nuclear

chain reaction. This is the process that Leo Salad first envisioned on a London street corner over a decade ago.

Adams break apart.

More neutrons are released.

Smashing more atoms, releasing energy and more neutrons and more energy.

The goal is to make that nuclear chain reaction

as big and as destructive as possible.

On July 16, 1945, deep in the New Mexican desert,

the bomb will be tested for the first time.

5.25 a.m. the closest viewing stations are all at least five miles from the test itself.

Some of the scientists have even taken bets, half joking,

on whether they will ignite the atmosphere.

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