Musée de Lettres et Manuscrits

Last Friday, May 31, our class visited the Museum of Letters and Manuscripts, a modest museum containing texts handwritten by prominent historical, artistic, and scientific figures. Though the collection was small, I spent several minutes by each piece, deciphering the descriptive plaque and attempting to unravel the unusual handwriting of the creator. At the time we left, I had only made a thorough investigation of the scientific texts and a few historical documents, but I had already found one document that particularly impressed me. Displayed below was a paper that I recognized on sight, because it teaches special relativity in the same way I learned it last fall:

Drawings made in 1939 by Albert Einstein to explain
Special Relativity to his neighbor

In a museum where so much is faded, or illegible,or written in a language I have never learned, I found this document without words astonishing. Special relativity is nothing like the beast many people make it out to be, and can be reduced to saying that the faster an object goes relative to you, the shorter it appears, and the slower time will seem to progress on that object. In explaining the mechanics of this, little math is required for a simple understanding, and what I found fascinating is that Einstein's method of explanation is identical to the one I have learned in physics classes and textbooks.

The key diagram in this picture is the M-shaped line in the lower half, which indicates the path of a light particle reflected between two mirrors that are moving at constant velocity. If lightspeed is constant, and the light between the moving mirrors needs to follow this M shape, then from the perspective where the mirrors are moving, it must be the case that time is passing more slowly for the mirrors. Much of the rest of relativity follows from this simple observation, and I am astonished and happy that based only on the barely-marked sketches of Einstein I can give a clear explanation of this fundamental piece of the explanation.

Understanding Einstein's sketch of his proof makes me feel not only academic pride, but also a sense of connection with the originator of this important discovery. I have made scratches like these on the back of several notebooks and napkins over the years, and knowing that the most revered of modern physicists did the same in his own studies makes me feel more like an actual physicist. As someone who hasn't quite figured out what to do with his degree after graduation (I don't know how to balance teaching, research, and speaking), it is heartening to know that I share these drawings and this joy in explanation with Einstein.