Conceptual Understanding in Introductory Physics V: Length Contraction and Time Dilation

This series continues with yet another question from introductory special relativity. I have seen this question asked many times in various places and unfortunately, have rarely seen the correct answer given.

After studying special relativity, students sometimes ask, “What really happens to a moving rod to make it contract?” and “What really happens to a moving clock to make it run slow?” Comment on whether or not these are legitimate questions and on how to respond to them. 

Special relativity has a reputation for introducing non-intuitive findings into physics and these are somehow treated as obstacles that must be overcome. I take the point of view that instead, they are opportunities to refine and refine our physical intuition. It’s important, I think, for introductory students to understand that our intuition isn’t necessarily innate, and that it can change to reflect our deeper understanding of Nature when evidence suggests something new is afoot.

Okay, see what you can do with this question!


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