Science has moved a step closer to harnessing the process that powers the sun to produce energy on earth. The National Ignition Facility in the United States of America announced this week that its researchers had managed to focus a laser beam onto hydrogen atoms to generate enough energy to heat more than a dozen kettles of water. That might seem like a small step for science, but it could portend a giant leap for humankind. Nuclear fusion, the mechanism that powers the sun, has the potential to generate significantly greater amounts of energy in safer ways than is possible with nuclear fission, the process that is used in atomic reactors and weapons. Unlike with fission, fusion does not leave radioactive waste that can poison the planet and its people for decades. It also does not depend on fossil fuels. Yet, for more than 50 years, science has struggled to generate high enough temperatures and sustain those long enough to be able to trigger fusion reactions. Even now, it will take several years before laboratories can scale the recent experiment to a level where fusion can actually become helpful as a reliable source of clean energy for homes and industries. The recent attempt in the US too did not generate more energy than was used to trigger the reaction in the first place. Still, for scientists to have cracked what until now has seemed an impossible barrier represents a historic achievement.

But as with all major scientific advancements, it is important to temper excitement with realism. In theory, the abundance of hydrogen in the atmosphere means nuclear fusion can produce as much clean energy as the world needs. But throughout history, such breakthroughs have far too often served to deepen — rather than reduce — disparities. Not many nations will have the resources to scale up the success of what has been attempted in the US. There is no reason to believe that nations that succeed will share their technological knowhow with countries that are poorer or have less sophisticated scientific establishments. This could widen the energy access gap between wealthy and developing economies. If countries use fusion to develop a new generation of devastating weapons, it could spark a dangerous new arms race. Like the sun itself, the power of fusion must be a source of life, available to rich and poor alike. Science must benefit all.