Memo from Massachusetts: Thanks, Arthur Eddington, for figuring out fusion
A century separates the pioneering work of a UK astrophysicist and CFS’ fusion energy work. Chief Science Officer Brandon Sorbom still feels the link.
To: Sir Arthur Eddington, Fellow of the Royal Society
From: Brandon Sorbom, CFS Chief Science Officer
Date: December 2024
Subject: From one physicist to another: thank you
Sir Arthur:
I’m sure we agree that luminaries such as James Clerk Maxwell, Marie Curie, Niels Bohr, and Albert Einstein earned their fame. But since I’m the co-founder of a fusion energy startup, Commonwealth Fusion Systems, I think it’s time we try to give you the credit you deserve too.
I just reread your famous 1920 paper, The Internal Constitution of the Stars. The magnitude of your achievement — being the first person to figure out how the sun works — leaves me in awe.
Modern scientific equipment is much better at probing the mysteries of the universe than what you had available. You had to rely on applying Einstein’s then-novel E=mc2 equation to the difference in mass between four hydrogen atoms and one helium atom. A quartet of hydrogen atoms is somewhat heavier together, so merging them releases a lot of energy.
In your words, “The total heat liberated will more than suffice for our demands, and we need look no further for the source of a star’s energy.” You nailed it.
These days we call that process fusion, and here at CFS we’re trying to use that process to recreate the power of the sun on Earth. I think you’d appreciate it.
Out with the old
What a profound change from just a few decades earlier, when Sir William Thomson, aka Lord Kelvin, posited that the collisional energy from a pileup of meteors was most likely the cause of the sun’s heat.
That sounds better than a sun made of burning coal that would last only a few thousand years. Lord Kelvin moved to a gravitational contraction idea that fared a little better than the meteoric hypothesis, but still didn’t explain how the sun could be billions of years old.
The idea that there could be a different process that powered the sun, a process that’s a hundred million times more efficient and could lead to a sun that would burn for billions of years — that was a profound insight.
And your dismissal of that last explanation was awesome: “Only the inertia of tradition keeps the contraction hypothesis alive — or rather, not alive, but an unburied corpse.”
Citing findings from geology, astronomy, and even evolution-era biology, you concluded, “If the contraction theory were proposed today as a novel hypothesis I do not think it would stand the smallest chance of acceptance.”
In with the new
You factored modern physics into your thinking at Greenwich and Cambridge, a radical leap. Well done.
Sir Isaac Newton masterfully explained the mechanics of human-scale objects, observable simply by using our senses. Modern physics, whether at the immense scale of stars and galaxies or the tiniest scale of atoms, is profoundly alien to our experience. To many, it’s baffling.
But it works, successfully explaining what’s happening in the sun and in other domains.
In particular, E=mc2 gives you the physical means to explain the sun. In that equation, c, the speed of light, is a really big number, and c2 is a ridiculously large number. So if you’re converting a little bit of mass of a nucleus into energy, all it takes is a tiny, tiny amount of mass and you get a whole lot of energy.
It took more work to nail down the details of stellar fusion and prove it all true. Ernest Rutherford’s lab successfully fused deuterium isotopes of hydrogen into helium in 1934. Hans Bethe figured out the more complicated fusion reactions that actually take place in the sun.
A golden age of physics
You lived in a golden age of physics, and I wish I could have seen it myself. Nobel Prize-class research sprang up all over the place. I mean, sheesh, Einstein alone probably deserved four Nobel Prizes.
It’s hard to say what led to this explosion of activity at the same time Europe was suffering through two world wars, but I think it’s mostly that the foundations were laid for smart people to take the next leaps. Mathematics had matured. The first principles of electromagnetism and thermodynamics had arrived. And although we couldn’t just use our eyes and ears to run the experiments to prove this new physics, the experiments still often fit on a lab benchtop.
With all that, you and your peers not only could suggest an idea about how things work at the atomic level, but also could translate that into something detectable on the macro scale. Your experiments could show you weird stuff you wouldn’t normally expect in everyday life.
You were a remarkable bunch of hardcore experimental and theoretical physicists. There was so much discovery going on. And you did it all wearing suits, which honestly is pretty badass.
Compare these experiments to CERN’s Large Hadron Collider, an underground ring 27 kilometers in circumference that had to run for years before finding its target, the Higgs boson. I point out that exciting discovery not to diminish it, but to highlight how exciting it must have been to be able to make fundamental discoveries about nature in a university-scale lab. Y’all described fundamental discoveries in a couple of pages dashed off to Nature, but these days it often takes 50-page super-proofs to detail new physics.
Putting your ideas to good use
At CFS, though, we’re not developing the basic laws of physics to make fusion power plants at a commercial scale. We still have plenty of engineering, design, and modeling work, but the fundamental foundation of squeezing energy out of a plasma is well understood — indeed, that’s why we selected the tokamak approach for our work.
I’m sure you can relate. Having explained the mechanism of the sun’s heat, you wrote in that paper 104 years ago that you “sometimes dream that man will one day learn how to release it and use it for his service. The store is well-nigh inexhaustible, if only it could be tapped.”.
Well, guess what? That’s exactly what we’re doing. We’re a few steps farther down the march of science history, and it’s really cool that we’re directly following a path you helped to blaze.
I wish you could be here to see it.
