The Future Circular Collider: A Debate with Sabine Hossenfelder & Harry Cliff

The Core Debate: Future Circular Collider

• 💡 The central discussion revolves around whether to invest tens of billions of dollars into the Future Circular Collider (FCC), a proposed successor to the Large Hadron Collider (LHC).
• 🎯 Harry Cliff, an experimental physicist at CERN, advocates for the FCC, emphasizing its scientific potential.
• 📌 Sabine Hossenfelder, a theoretical physicist and science popularizer, argues against the project, citing concerns about its cost and scientific return.

Case for the FCC: Harry Cliff

• 🔬 The primary goal of the FCC's first phase (an electron-positron machine) is to produce millions of Higgs bosons for high-precision measurements.
• 🔑 This aims to determine if the discovered Higgs boson is the Standard Model Higgs or a more exotic particle, providing clues to physics beyond the Standard Model.
• 🚀 Precision measurements of known particles can also offer indirect evidence for new physics at energy scales far beyond direct reach.
• 💰 The estimated cost of the first phase, around €15 billion over 15 years, is presented as a manageable sum when spread across CERN's member states, comparable to other major science projects.

Case Against the FCC: Sabine Hossenfelder

• ⚠️ Hossenfelder views the FCC as a high-risk, low-return investment, arguing that the expected outcome—more precise Higgs constants—does not justify the estimated €40 billion total cost (including operations).
• 🧠 She contends there's no scientific evidence linking the Higgs boson to major mysteries like dark matter or the origin of the universe, despite theoretical speculation.
• 📉 Such a massive project could drain intellectual talent from other, potentially more promising, areas of physics and societal challenges.
• 💬 Hossenfelder criticizes particle physicists for overstating scientific promises (e.g., finding dark matter or supersymmetry) to the public and media, which often do not materialize.

Cost, Talent, and Alternatives

• 📊 The debate highlights differing perspectives on the FCC's financial impact, with Cliff viewing it as a small percentage of government spending and Hossenfelder seeing it as a substantial investment that could be better allocated.
• 🌱 Hossenfelder suggests investing in areas like the measurement problem in quantum mechanics or probing the weak field limit of quantum gravity, which she believes are currently underfunded and could yield significant technological and scientific breakthroughs.
• 🤝 Cliff argues that science funding is not a zero-sum game, and investment in one area should not preclude others, emphasizing the broader benefits of fundamental research, including technological spin-offs.

Future of Physics and Collider Technology

• 🔭 Cliff believes physics is generally moving in the right direction, with a broad range of experiments exploring fundamental questions, and the FCC representing the best foreseeable machine for particle physics.
• 🛑 Hossenfelder, however, asserts that fundamental physics has stagnated for 50 years on big questions, and the community needs self-reflection to identify truly promising experiments.
• ⚡ Alternative collider technologies like muon colliders are discussed as potentially more innovative and cost-effective, though their technology is not yet mature enough for immediate construction on a human timescale.