The quest to bottle the power of the sun has led to countless starry-eyed predictions of an imminent clean energy revolution. But the expectations for fusion have always been outsized, the trail of broken promises has grown long and public perception has soured.

While our cynicism about fusion may feel justified, it’s also unfortunate. Because, despite tepid support and constant funding peril, researchers are making progress toward this futuristic energy source. Scientists will eventually solve fusion’s immense technical challenges, if society can commit to the journey.

Last week, I visited the Princeton Plasma Physics Laboratory to tour the recently-upgraded National Spherical Torus Experiment (NSTX-U), the most powerful “spherical tokamak” fusion reactor on Earth. An 85 tonne beast of a machine shaped like a giant cored apple, the NSTX-U uses high energy particles to heat hydrogen atoms to temperatures of 100 million degrees Celsius, hotter than the core of the sun. To contain this super-hot plasma, winding copper coils generate a magnetic field 20,000 times stronger than that of the Earth. All of this so that for a few magic seconds, atomic nuclei will collide, fuse and release energy.

The experiment is a step along the path toward a fusion plant that would run constantly, powering entire cities on mere grams of seawater.

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