Introduction.- The Meselson-Stahl Experiment: “The Most Beautiful Experiment in Biology”.- The Discovery of the Positron.- The Discovery of the Omega Minus Hyperon.- Once Should Have Been Enough: Gregor Mendel, “Experiments in Plant Hybridization”.- Once Came Close To Being Enough: Electron Polarization and Parity Nonconservation.- The Discovery of Parity Nonconservation.- The Search for the Magnetic Monopole.- Conclusion.

Allan 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. He has twice been Chair of the Forum on the History of Physics of the American Physical Society and served two terms on the Executive Council of the Philosophy of Science Association. 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. He and Ronald Laymon are the co-authors of Measuring Nothing, Repeatedly.
Ronald Laymon is Professor of philosophy emeritus at the Ohio State University where he specialized in the history and philosophy of science. He has published widely, was the recipient of multiple National Science Foundation research grants, and was a Fellow at the Center for the Philosophy of Science at the University of Pittsburgh and a Resident Scholar at the Rockefeller Foundation’s villa in Bellagio. In 1995, he took advantage of an early retirement option and completed a law degree at the University of Chicago School of Law in 1997. He then went on to practice large-scale commercial litigation at the Jones Day law firm where he had the good fortune to serve as second chair on a case before the United States Supreme Court. Now retired from the full-time practice of law, Laymon does consulting work for a biotech, intellectual property firm that facilitates the open source creation of therapeutic technologies. Retirement has also made it possible for Laymon to resurrect his interest and earlier work in the history and philosophy of science. He and Allan Franklin are the co-authors of Measuring Nothing, Repeatedly.