A San Francisco startup says it just turned mercury into real gold, and their own math says gold is one of the cheapest things their machine can make. Aim it at a different metal and it makes a cancer drug ingredient worth tens of billions of dollars a gram. Here's how it works. When you fuse two kinds of hydrogen, deuterium and tritium, every single reaction kicks out a neutron moving at 14.1 MeV, which is absurdly fast. Fire one into mercury-198 and it knocks another neutron loose on the way through, so two come out and you're left with mercury-197. Give that a few days and it decays into gold-197, the only stable kind of gold there is. The whole trick needs neutrons above about 6 MeV, and regular nuclear reactors barely make those, while fusion makes one every time it fires. Now swap the mercury for radium-226. Same reaction, one neutron in and two out, and you end up with radium-225, which decays into actinium-225. Novartis is building its next prostate cancer drug around actinium-225, and it's so scarce it sells by the millicurie, roughly $1,200 to $2,500 apiece. Price it by the gram and you're into the tens of billions of dollars, for a material so radioactive nobody could safely hold a gram of it anyway. Marathon's team actually put a dollar value on a single fusion neutron in a paper this year. Use it to make electricity and it's worth about $3 × 10⁻²⁰. Gold comes in at $2.6 × 10⁻²⁰, basically a wash. Molybdenum-99, which goes into about 80% of nuclear medicine scans, is worth $2.6 × 10⁻¹⁷ a neutron. Actinium-225 is worth about $10⁻¹⁰, around 3 billion times what the electricity's worth. That's why fusion people should care. Every fusion company you've heard of is chasing electricity, and selling electricity only pays once the plasma puts out something like 10 to 22 times the energy you pump in to heat it. The best result so far, at JET in England, was about a third. Add gold on the side and Marathon's math says you break even around 3x. For molybdenum-99, the number is 0.001x. So a machine that gives back one-thousandth of the energy you feed it can still make money, as long as the neutrons hit the right metal. By their numbers, a 3 megawatt machine running way below breakeven could cover the whole world's supply of molybdenum-99, which today comes from splitting uranium in a handful of research reactors. Today's experimental fusion machines already beat the gain that job needs. Their second post basically says this out loud. Marathon now describes itself as an isotope company for radiopharma. Their chart shows roughly 390 targeted radiotherapy trials. Pluvicto, the prostate cancer drug Novartis launched at $42,500 a dose, did $1.9 billion in sales last year. Gold still matters to them, just later. It's about a $700 billion a year market, and Marathon's paper figures it could soak up around 2 terawatts of fusion capacity, which is roughly the scale where fusion actually moves the grid. So the plan is to sell cancer isotopes out of small machines now and use gold to pay for the giant ones, years before electricity can pay for itself.

Madhu Guru (@realmadhuguru) led product for Gemini. He thinks fewer than 75 PMs are qualified to do the work. That's a pretty wild stat. Madhu is now a senior director of AI at Meta, and he identified 5 skills that every PM working on things like Gemini needs to be able to do: 1) Vision and opinionated UX design 2) Model intuition to extract max value 3) Going from pixels to evals to hill climbing 4) Agentic flows: tools, context and safety guardrails 5) Deep user understanding He says it's scar tissue from hiring, so I'm inclined to believe him. He means AI-native PMs, but I really think it's fewer than 75 for model PMs. I found 46 open model PM roles, oddly close to 75. I read all the postings, and they ask for similar things. Here's what they look for, by percentage of postings: 1) Vision and opinionated UX design: 61% 2) Model intuition to extract max value: 61% 3) Going from pixels to evals to hill climbing: 76% 4) Agentic flows: tools, context, safety guardrails: 59% 5) Deep user understanding: 50% Now the last line of his tweet: "It is a rare, but learnable skillset. Only way is to build, build, build." I think that's the most important point, and the postings agree with him. Only 7 of the 46 require production experience. What they're really looking for is that you are building, and you can go build these things on the side. What I recommend: pick a task your favorite model struggles with. Write down the failure modes. That's the start of your eval set, and that's the product you should build, something that solves them. Start with a behavior spec for it: "the model should..." Those lines become additional evals. Then ask Claude Code to build a product that passes those evals, and iterate. You'll learn how to build on top of models. Model PMs are paid extremely well. The median posted base is $345K, and the range runs from $144.6K to $490K. As he said, it's learnable. Because there's so little supply, why don't you become one? Why don't you get that pay bump? I think you can, and I'm here to help. Let me know any challenges you face in the comments.