February 25, 2004
A: FROM MENTOR JOAN LUSK IN RI
I'm no expert on relativity, so I checked this out - a school posted this
http://www.geocities.com/thesciencefiles/theoryof/relativity.html with links to a downloadable demonstration (it didn't work for me but I'm on a Mac right now - maybe it's for Windows). Tell your Mom that the site says that the relativistic runner would look thinner but would actually weigh more! So much for that great diet plan. Your Mom and I will have to think of something else.

The relevant equation, showing how length gets smaller when an object moves at nearly the speed of light, is on the first page of this PDF (and in many textbooks). the PDF has some entertaining pictures and examples, and if you've had algebra you'll understand the equations. But _really_ understanding relatively, _feeling_ that yes, the world does have to be like that, well, that takes deeper study. Enjoy!
http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/Pdf_downloads/6.pdf