In the early 70s, Rob Goldston was a graduate student in plasma physics, and experiments to produce fusion energy were just starting to bear fruit.
“We had a huge party because we had made 1/1000th of a joule of fusion energy,” he told me. “It was ridiculous, it was a tiny amount of energy." A 35-watt light bulb, for instance, uses 35 joules every second. Now, 40 years later, the game has changed. A recent experiment at the Joint European Torus fusion reactor in the United Kingdom produced 20 million joules. And the National Ignition Facility in California just reached a milestone by producing more energy in a fusion reaction than was needed to start that reaction.