Since the 1950s, scientists around the world have sought to replicate the reaction that fuels the sun in search of a clean energy holy grail, a technology capable of providing nonstop electricity without planet-heating emissions or radioactive waste.

U.S. government researchers just got closer than anyone has before, briefly generating more energy from a fusion reaction than it took to set off, achieving whats known as ignition.

Blasting hydrogen plasma with the worlds biggest laser had already yielded a Wright brothers moment in August 2021 when, for a brief 100 trillionths of a second, scientists at the Lawrence Livermore National Laboratory in California registered a historic burst of fusion energy. But the 1.3 megajoules generated was only about 70% of the energy fired from the laser.

Last week for the first time they designed the experiment so the fusion fuel stayed hot enough, dense enough and round enough for long enough that it ignited and it produced more energies than the lasers had deposited, Marvin Adams, the National Nuclear Safety Administrations deputy administrator for defense programs, said Tuesday morning at a White House press conference announcing the discovery. About 2 megajoules in, about 3 megajoules out.

Its a major new milestone the first proof that humanity can harness the cosmic energy released when two lighter atoms fuse into one heavier element, less than a century after the awesome power of splitting atoms debuted as mushroom clouds.

We are in a moment of history, really, said Arthur Turrell, a plasma physicist whose book The Star Builders tracks the growing momentum in nuclear fusion. No doubt its one of the greatest technological challenges humanity has ever undertaken, but here we are. Theyve done it. Theyve proven it can happen.

The Financial Times first reported the experiments results on Sunday.

Conventional nuclear energy is the result of fission, the energy released when the nucleus of an unstable atom divides into two. The first controlled fission experiment took place at the University of Chicago in December 1942. The first commercial nuclear reactor came online in England in August 1956.

Experts say itll take a lot more than 14 years to commercialize fusion energy.

For starters, the $3.5 billion National Ignition Facility was built to test atomic weapons, and its array of 192 high-energy lasers is, at this point, outdated and ill-equipped to scale fusion energy experiments.

And inertial confinement fusion sometimes referred to as laser fusion since it relies on powerful rays to jumpstart the reaction has long been a secondary priority in the field.

Of the roughly $700 million the federal government spends on nuclear fusion research every year, most goes to paying the U.S. share of the International Thermonuclear Experimental Reactor, or ITER. The worlds largest fusion experiment currently under construction in France with funding from the European Union, China, India, South Korea and Japan isnt expected to come online until 2027. But its doughnut-shaped tokamak reactor is designed for magnetic confinement fusion, which holds fuel in place with giant magnets while the atoms nuclei heat up.

That tokamak design and magnetic process have yielded record volumes of energy for seconds at time, but has yet to come anywhere close to so-called net energy gain.