What type of experiments are conducted entirely in a person's mind, often utilized by Einstein?

Thought experiments are a conceptual tool frequently used in physics, particularly by thinkers like Einstein, to explore ideas without the need for physical implementation. In a thought experiment, an individual imagines a scenario and analyzes its implications to reveal underlying principles or test hypotheses. This approach allows theorists to engage with complex concepts in a way that traditional physical experimentation might not allow, especially when dealing with abstract or theoretical frameworks, such as in relativity or quantum mechanics.

The use of thought experiments can illuminate the consequences of a theory by considering hypothetical situations, enabling critical insights into processes and phenomena that may be impossible or impractical to replicate in a laboratory setting. This method relies entirely on cognitive reasoning and creative visualization, making it unique from physical experiments, field experiments, and controlled experiments, which require tangible experimentation and external validation.