“Gedankenexperiments” is what Albert Einstein called one of his most enduring contributions to physics. You might know them better as “thought experiments.” Whether daydreaming of riding beams of light or picturing people tumbling into black holes, Einstein used his mind’s eye to explore the natural world and then sought out ways to test his intuitions with real-world experiments. Theoretical physicist Sabine Hossenfelder explores several of the famous physicist’s best-known Gedankenexperiments and shows how influential they’ve been.