In philosophy, physics, and other fields, a thought experiment (from the German Gedankenexperiment) is an attempt to solve a problem using the power of human imagination. These experiments are used to attempt to understand something about the universe. Thought experiments have been used to pose questions in philosophy at least since Greek antiquity; a famous example is Plato's cave, but others pre-date Socrates. In physics and other sciences many famous thought experiments date from the nineteenth and especially the twentieth century, but examples can be found at least as early as Galileo.
Many thought experiments include apparent paradoxes about the known or accepted, that with time have led to the reformulation or precision of theories.
Famous thought experiments
Thought experiments are popular in physics and include:
The field of philosophy makes extensive use of thought experiments: