It was touted as a "major scientific breakthrough" and, it seems, the rumors were true: On Tuesday, scientists at Lawrence Livermore National Laboratory announced that they have, for the first time, achieved net energy gain in a controlled fusion experiment. "We have taken the first tentative steps toward a clean energy source that could revolutionize the world," Jill Hruby, administrator of the National Nuclear Security Administration, said in a press conference Tuesday. The triumph comes courtesy of the National Ignition Facility at LLNL in San Francisco. This facility has long tried to master nuclear fusion -- a process that powers the sun and other stars -- in an effort to harness the massive amounts of energy released during the reaction because, as Hruby points out, all that energy is "clean" energy.

This article initially misstated the amount of energy in the fusion reaction. NIF powered the lasers with about 2 megajoules and produced 3 megajoules as a result.

The big fusion experiment The NIF, which takes up the space of around three football fields at LLNL, is the most powerful "inertial confinement fusion" experiment in the world. In the center of the chamber lies a target: a "hohlraum," or cylinder-shaped device that houses a tiny capsule. The capsule, about as big as a peppercorn, is filled with isotopes of hydrogen, deuterium and tritium, or D-T fuel, for short. The NIF focuses all 192 lasers at the target, creating extreme heat that produces plasma and kicks off an implosion. As a result, the D-T fuel is subject to extreme temperatures and pressures, fusing the hydrogen isotopes into helium -- and a consequence of the reaction is a ton of extra energy and the release of neutrons. You can think of this experiment as briefly simulating the conditions of a star.

The future of fusion The experiment at NIF might be transformative for research, but it won't immediately translate to a fusion energy revolution. This isn't a power-generating experiment. It's a proof of concept. This is a point worth paying attention to today, especially as fusion has often been touted as a way to combat the climate crisis and reduce reliance on fossil fuels or as a salve for the world's energy problems. Construction and utilization of fusion energy to power homes and businesses is still a ways off -- decades, conservatively -- and inherently reliant on technological improvements and investment in alternative energy sources. Generating around 2.5 megajoules of energy when the total input from the laser system is well above 400 megajoules is, of course, not efficient. And in the case of the NIF experiment, it was one short pulse.