On Christmas eve in 1938, the physicist Lise Meitner took a walk in the snowy woods of Kungalv, Sweden, with her nephew, Otto Frisch, also a physicist. A Jewish refugee who recently had escaped from Hitler's Germany, Meitner began discussing with Frisch some puzzling experimental results from a lab in Berlin.

By the time their famous walk was over, Meitner for the first time had scribbled down the equations that demonstrated the possibility of extracting huge amounts of energy from the splitting or "fission" of uranium atoms. Seventy years ago, the woman whom Albert Einstein called "our Madame Curie" ushered us into the nuclear age.

Meitner wanted nothing to do with the military use of the unprecedented energy she had discovered. Still, the insights of Meitner and others made it possible to create the bombs used to conclude World War II in the tragedies of Hiroshima and Nagasaki, and the great taboo has held since then. But it might not last much longer. As we contemplate the prospect of nuclear weapons in the hands of North Korea and Iran, it would seem that the advance of science has outpaced the needed capacities of human stewardship.

But there is more to this Christmas story than the unhappy possibility of nuclear power's abuse. Like the three wise men following a star, Meitner was also bearing gifts. The world is becoming increasingly aware of the costs and consequences of our present global energy system, from carbon emissions to the massive petro-funding of fanatic theocracies. Yet, as Meitner showed, all of the energy we could ever hope to use is around us in ordinary matter.

Our physical world is the product of long-ago nuclear explosions, whose vast energy remains stored in the atoms of our planet. Hydrogen was forged in the super-high temperatures of the Big Bang, and other basic chemical elements of life, including oxygen and carbon, were created in the cores of early stars, long before the Earth and sun were formed.

As Meitner recognized, the energy from these primordial nuclear power plants is available to us in astonishing abundance.

The technology is already well known. Consider France, which generates 80 percent of its electricity using fission to release the energy inside relatively rare uranium atoms.

Although the vexing and politically charged issues of nuclear waste disposal have not been fully resolved, nuclear energy is both green and clean, especially as compared with dirty, dangerous oil and coal.

The French have been using nuclear energy for decades, with few safety problems and no carbon footprint. Expanding America's already well-established and impressively safe nuclear-power capacity by a factor of roughly 15 (to put us on a par with France) would allow us to make a relatively quick transition to energy security and to much-lower greenhouse gas emissions.

But Meitner's legacy might eventually yield still more precious gifts. Scientists and engineers have been working for more than half a century on ways to use the energy available from "burning" deuterium (a rare but stable isotope of hydrogen) in fusion reactions — that is, by combining rather than splitting atoms. This is a very difficult technological objective, but it might well be achieved in a few decades.

If fusion technology using deuterium were to be developed, current total world energy demand each year could be met by using the natural deuterium available in a cube of water measuring about 200 meters on each side. Such technology would be incredibly eco-friendly, especially as compared with solar power and other renewable energy sources, which make hugely problematic demands on land use.

Science has given us vast new powers. Unfortunately, human civilization has not developed in such a way as to ensure the wise use of these powers. Meitner appreciated the complexities of this dilemma, but she also understood that nuclear energy might turn out to be an unprecedented boon. Today, it remains the most obvious and elegant solution to our twin energy and environmental crises, if only we can manage to assess its potential without the usual alarmism and phobias.

Confronting our dangerous and uncertain future is a matter of hope and of a faith that is not wholly rational. One might compare it to following a star from Persia to Bethlehem — or to trusting that the brilliant insights of a snowy walk in the woods ultimately will serve to benefit all humankind.

Charles L. Harper Jr. is an astrophysicist and senior executive vice president of the John Templeton Foundation. He wrote this commentary for the Los Angeles Times.