‘Physics advances through a productive tension between theory and experiment. Theorists and experimentalists often frustrate each other—experimental results can ruin elegant theories, while theorists can annoy experimentalists—but that conflict is actually valuable. Even wrong theories can push experimentalists to build new experiments, sometimes leading to discoveries they would never have made otherwise. Progress in physics depends on this rough back-and-forth: theory challenges experiment, experiment tests theory, and both sides keep each other skeptical. That is why there’s a healthy distrust on both sides, captured in the jokes that a theorist is the only one who believes their paper, while an experimentalist is the only one who doesn’t believe theirs, and that people should not trust an experimental result until theory can explain it.’ Thoughts from Prof Max Tegmark on The Into The Impossible podcast with host Prof Brian Keating