LOS ALAMOS, N.M. - David Hawkins stared south through the chilly canyon gloom toward the wide open range. Behind him, an Army secretary worked quietly at her desk.

It was July 16, 1945. They were the only ones inside the darkened Technical Area of the Manhattan Project, the top secret research compound hidden in the foothills of the Rocky Mountains.

A philosopher, not a physicist, Hawkins was a lonely man that summer morning, as other "white badge" insiders took their places miles away to witness the biggest scientific experiment of the 20th century: The test blast of the atomic bomb.

So he waited at the window, and watched. At 5:29:45 a.m., a brilliant flash of white light spread silently across the desert horizon.

"I wonder when we'll hear from them," the secretary mused, not looking up.

"Any minute now," Hawkins replied. Then, in the quiet of this momentous dawn, the teletype began to clatter.

Now, fast forward to today and click on cable TV.

In The Simpsons, buffoonish Homer Simpson works as a safety manager at a fictitious nuclear power plant. In one episode of the cartoon satire, federal inspectors backpedal in fear upon discovering a radioactive fuel rod in a package of doughnuts.

Oblivious, Homer gobbles a glowing pastry and extends the box with the invitation, "Sprinkles?"

So the Atomic Century ends. Not with a bang, but with a snicker.

What started as a theoretical journey inside brilliant scientific minds, and literally exploded into a fundamental issue facing humankind, has wound up as a punchline.

"I think it's because a lot of things were done wrong, and other things didn't have to be done at all," said University of Wisconsin physicist Robert March.

March is a prize-winning author who studied under Nobel laureate Enrico Fermi, a Manhattan Project collaborator who produced the first self-sustaining nuclear chain reaction in 1942.

"Everybody has a right to feel ambivalent about the horror hanging over our heads with nuclear weapons," March said. "And the weapons builders thought they had to give nuclear power to the world almost as an atonement for their sins. They pushed the technology prematurely."

The Atomic Century actually was 25 centuries in the making.

In the 5th century B.C., the Greek philosopher Democritus suggested matter could be divided into finer and finer pieces until a fundamental unit was reached.

In 1803, British chemist John Dalton described atoms as the unique constituents of the chemical elements. All atoms of one element, say hydrogen, were alike and weighed the same, Dalton determined. But all hydrogen atoms were different from atoms of the other elements.

It wasn't until the turn of this century that experiments hinted at the power trapped inside the atom.

Radiation is the energy given off by atoms. A handful of unstable heavy metals emit energy when their nuclei disintegrate.

In 1903, Marie and Pierre Curie realized that uranium ore contained more radioactivity than could be accounted for by the uranium itself. From tons of ore, they isolated small amounts of two highly radioactive new elements - radium and polonium.

They shared the Nobel Prize in physics in 1903. Marie Curie won the chemistry Nobel in 1911 for describing the new elements' properties.

In 1905, Albert Einstein began publishing equations describing the atom and the forces controlling it.

His signature equation, E=mc2 (energy equals mass times the velocity of light squared), was the cornerstone for controlling the release of energy from the atom.

Incredible forces bound the atom tightly. If an atom was split, its two parts would weigh less than the whole, he reasoned. The difference was energy released.

In 1938-39, German and Austrian scientists in Berlin bombarded uranium with neutrons and detected the emergence of much lighter elements. Physicist Lise Meitner determined the uranium atoms had split. She named the reaction fission.

It was a scientific triumph, but an alarming development. What to do with Einstein's energy, once liberated?

It was no idle question. The world was mobilizing for war.

Splitting atoms of radioactive, heavy metals in an uncontrolled chain reaction would release excess energy in one colossal ka-boom one million times more powerful than TNT.

Whoever won this dreadful race to unleash the power of nature could rule the planet. Or destroy it.

As European scientists fled to the United States and England to escape Nazi persecution, Hungarian-American physicist Leo Szilard and others persuaded Einstein to alert authorities to the danger inherent in the Berlin breakthrough.

In an obliquely worded warning, Einstein wrote President Franklin Roosevelt: "Certain aspects of the situation which has arisen seem to call for watchfulness."

FDR scrawled "This requires action" across the physicist's letter. The president later militarized physics by authorizing the Manhattan Project on Dec. 6, 1941 - one day before Pearl Harbor.

By the following summer, philosopher Hawkins moved from Berkeley, Calif. to the lonely New Mexico mesa where Los Alamos was sprouting.

As physicists toiled around the clock to transform blackboard equations into a weapon, he served as science's envoy to the outside world - project historian, civilian liaison to the War Department and assistant to project director J. Robert Oppenheimer.

"We all knew it was something important," recalled Hawkins, now 85 and living in Boulder, Colo. "I wanted to be part of it."

But by the time the scientists gathered to watch the test blast, code-named Trinity, Hawkins declined to join them.

He no longer believed a doomsday weapon was necessary. He was frightened by the scientists' casual hallway debate whether there was a chance, however slim, that the blast might ignite nitrogen in the atmosphere and literally blow up the world.

"The climactic thing to me was my decision not to go see the test," Hawkins said. It was the start of "a certain alienation," said the man who has devoted his life to arms control and science education, for which he would be awarded an inaugural MacArthur Foundation "genius grant."

At Ground Zero, 200 miles south of Los Alamos, the hazy flash that Hawkins glimpsed actually was a mushroom cloud boiling like lava six miles into the sky.

It vaporized the 10-story steel test tower. Desert sand fused into a radioactive green glass.

"There was an enormous flash of light, the brightest light I had ever seen," physicist Isidor I. Rabi recalled later. "There was an enormous ball of fire that grew and grew and it rolled as it grew; it went up in the air, in yellow flashes and into scarlet and green. A new thing had been born; a new control; a new understanding which man had acquired over nature."

Within three weeks, two atomic bombs of differing designs would reduce the Japanese cities of Hiroshima and Nagasaki to ash. They effectively ended World War II and pre-empted a U.S. invasion that would have cost untold lives.

Still, many of the physicists began to reassess their handiwork.

Said Oppenheimer: "The time will come when mankind will curse the names of Los Alamos and Hiroshima."

But once split, the atom could not be put back together again.

Over the next 30 years, more than 100,000 nuclear weapons would be manufactured in the United States and Soviet Union.

Along the way there have been moments of real terror. The Cuban Missile Crisis in 1962. Superpower saber rattling in the Middle East a decade later.

Ambitious powers in the world's toughest neighborhoods are elbowing into the exclusive nuclear club. Israel has the bomb, and last summer rivals India and Pakistan tested devices, too.

Thousands have been exposed unknowingly to test-related radioactive fallout.

And every American paid: The arms race has cost $5.5 trillion in the United States alone, according to the Brookings Institution.

The United States still spends $35 billion a year to maintain its aging nuclear arsenal, now down to 10,400 warheads. The number is to be reduced under disarmament agreements to fewer than 3,000.

Even then, how to handle the radioactive leftovers that will remain environmentally dangerous for eons, and keep fissionable materials out of the hands of rogue states and terrorists?

Scientists still proclaim the power of the atom to transform our everyday lives in benign ways.

Scanning microscopes allow researchers to examine the atomic structure cells and viruses, and build new industrial materials. Doctors infuse patients with weak radioactive cocktails to illuminate from within an array of illnesses. In many cases, especially cancer, they use higher doses of radiation to treat the illnesses, too.

Safety - now and later - is the issue. Accidents like Three Mile Island in 1979 and Chernobyl in 1986 demonstrated that combining human operators and complex systems can result in catastrophe.

Pure research has dimmed in the twilight of the Atomic Century.

In 1993, Congress canceled the $11 billion Superconducting Super Collider, the world's largest atom smasher. It would have enabled physicists to study the structure of matter in unprecedented detail in search of a unified theory of how nature works.

Mourning the collider, Nobel laureate Sheldon Glashow of Harvard said: "There are surprises that natural phenomena have in store for us. We're not going to find them unless we look."

He might have been summing up the promise and peril of the Atomic Century.

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