Einstein relished what he called Gedankenexperimente, ideas that he twirled around in his head rather than in a lab. That’s what teachers call daydreaming, but if you’re Einstein you get to call them Gedankenexperimente. As these thought experiments remind us, creativity is based on imagination. If we hope to inspire kids to love science, we need to do more than drill them in math and memorized formulas. We should stimulate their minds’ eyes as well. Even let them daydream… [The] ability to visualize the unseen has always been the key to creative genius. As Einstein later put it, “Imagination is more important than knowledge. 

Walter Isaacson, author of Einstein: His Life and Universe, on Einstein’s thought experiments