Allan D. Franklin is professor of physics emeritus at the University of Colorado. He began his career as an experimental high-energy physicist and later changed his research area to history and philosophy of science, particularly on the roles of experiment. In 2016, Franklin received the Abraham Pais Prize for History of Physics from the American Physical Society. He is the author of twelve books including most recently Shifting Standards: Experiments in Particle Physics in the Twentieth Century, What Makes a Good Experiment? Reasons and Roles in Science, and Is It the Same Result? Replication in Physics

Alysia D. Marino is a member of the physics faculty at the University of Colorado. She has been a researcher in experimental neutrino physics for over 20 years, studying neutrino oscillations with solar neutrinos and with accelerator-generated neutrino beams.

1. The Road to the Neutrino. 2. The Neutrino Hypothesis. 3. Towards a Universal Fermi Interaction. 4. Fermi's Theory: The Final Act. 5. 'Observing' the Neutrino: The Reines-Cowan Experiments. 6. How Much? The Mass of the Neutrino. 7. How Many? Whose? 8. The Missing Solar Neutrinos. 9. Neutrino Oscillations. 10 Conclusion: There Are Neutrinos. 11. Epilogue.