For a Fraction of a Second, We Lit a Star on Earth

2 min read

The Sun makes its light by fusion: under crushing pressure and heat, hydrogen nuclei are forced together to form helium, and a sliver of their mass is converted into enormous energy. For seventy years, physicists have tried to reproduce that process on Earth in a controlled way. The central obstacle has always been the same — it took more energy to ignite the fuel than the fuel gave back.

At the National Ignition Facility, researchers crossed that line. They focused 192 of the world's most powerful lasers onto a tiny capsule of hydrogen fuel, delivering about 2.05 megajoules of energy in a pulse lasting billionths of a second. The capsule imploded, its core reaching temperatures and densities like those at the heart of a star. The fusion that followed released roughly 3.15 megajoules — more energy out than the lasers had put in. Scientists call this milestone 'ignition.'

It is essential to be honest about what this does and does not mean. The reaction produced more energy than the laser light that reached the target, but not more than the total electricity drawn from the wall to fire those lasers. A power plant is still decades away, and the engineering between here and there is formidable. What changed is the physics: the long-standing question of whether net energy gain from controlled fusion is possible at all has been answered, and the answer is yes.

The promise on the far side of that work is a source of energy as clean as it is vast — fueled by forms of hydrogen drawn from water, producing no carbon and no long-lived radioactive waste. For one fraction of one second, in a building in California, human beings briefly held the same fire that powers the stars. We have not tamed it. But we now know it can be done.

1 min read

Every second, the Sun turns millions of tons of matter into light through a process called fusion. It is the reaction that lights every star in the sky. For seventy years, scientists have chased a daring idea: to build that same fire here, on the ground, and use it to power our world.

The hardest part was always the ledger. Igniting the fuel cost more energy than the fuel returned — like striking a match that gives off less warmth than your hand spent striking it. Then, at the National Ignition Facility, 192 lasers struck a fuel capsule no bigger than a peppercorn, and for an instant the fusion gave back more than the lasers delivered. Net energy gain, at last.

There is a long road from this spark to a power plant; no one's lights are running on fusion yet. But a question scientists have asked since before most of us were born has finally been answered. The fire of the stars is not beyond our reach. We have held it, just for a moment, and lived to study the ashes.

1 min read

The Sun shines because it squeezes tiny bits of hydrogen together so hard that they join and release energy. That is called fusion. Scientists have dreamed for a long time of making that same starlight here on Earth, to power our homes cleanly.

In a giant lab, 192 lasers all aimed at one tiny dot of fuel — smaller than a peppercorn — and for a flash, it gave back more energy than the lasers put in. It is the first time we have ever made a little star's fire and gotten more out than we put in. We can't use it for electricity yet, but now we know it is truly possible.