Nuclear fusion breakthrough offers hope for future generations - but the reality may be more complicated
This is a historic moment in fusion science.
Scientists have been pursuing the dream of producing energy from nuclear fusion for more than 70 years.
While fusion - the same reaction that powers the sun - has been achieved many times in many different types of devices around the world, all of them require massive amounts of energy to get fusion going.
This is the first time they've produced more energy from a fusion reaction than they put in.
And if you want to make energy from fusion, achieving that is about the most fundamental step there is.
But does it take us any closer to realising commercial nuclear fusion?
On a theoretical level, yes, it does. Someone had to the first to show you could get a gain of energy from doing fusion on Earth.
But on a practical level, not so much.
First, consider that although the US team got more energy out of their reaction chamber than they put into it, the overall energy they had to put into their power-hungry lasers to create the star-like conditions for the reaction to occur was 100 times what they got out of the fusion.
That's a 99% loss, not a net energy gain.
The other important caveat is the incredible National Ignition Facility (NIF) at the Laurence Livermore Lab in California, which achieved the result, isn't a fusion reactor. It's an experimental tool whose primary function is to test atomic weapons for the US government.
The fusion event they created lasted about 100 trillionths of a second and produced enough energy to boil about seven kettles. A whopping amount of power given the timescales - but hardly the energy source of the future.
Building a machine that is means harnessing a fusion for days or months, not nanoseconds. And then somehow capturing that energy to convert it into electricity.
And that is a very, very, hard science and engineering challenge.
Not the only game in town
Arguably, the NIF takes us no closer to that.
But fortunately for fusion science, and for humanity, which will one day befit from near-limitless energy with barely any waste, it's not the only game in town.
There are several state-funded fusion projects, one enormous international collaboration called ITER in France, and more than 30 small-scale commercial fusion ventures.
Nearly all are being designed with a pathway to a power reactor in mind.
But it's also important to say none of them are very close yet. The most common approach: using magnets to confine the charged fusion plasma in a spherical or doughnut-shaped reactor has the clearest route to success.
Some privately funded approaches like the UK's leading venture, Tokomak Energy, are aiming to be deliberately small, so they can experiment with new materials and magnet technologies.
"The smaller you can make a reactor, the more cost-effective it will be," says Dr Greg Brittles, its senior magnet engineer.
"In the development phase, it means we can get there faster. We can fail fast. We can learn fast. We can build things and learn.
"And that's going to get us the fusion as quickly as possible, which is what everyone needs," he says.
The company's plan is to get electricity out of a pilot commercial reactor by the 2030s.
Harnessing the power of the sun
But other experts doubt those claims. Some of the problems of making a commercial scale reactor get exponentially larger with size, says fusion scientist Dr Richard Pitts.
Maybe he would, because he's one of the lead scientists at the ITER, the world's biggest fusion experiment.
Although smaller start-ups may have the latest technology, he argues, they simply don't have the financial support to solve the big problems of physics and engineering that fusion constantly throws up.
"They are a very long way away from being at the scale necessary to generate fusion power from their devices," says Dr Pitts.
"In order to do that, you need to be at the scale of the ITER plant. And when you get up to those scales, life gets very much more complicated."
One thing is certain, fusion is unlikely to come online fast enough, or at least at sufficient scale, to solve humanity's current challenge: finding a new source of energy to replace fossil fuels.
We'll need to pursue existing technologies for that.
But today's breakthrough does offer the genuine hope future generations can look forward to harnessing the power of the sun here on Earth. With all the benefits that might bring.