Essay 3

Instructions

This essay is bigger than your previous essays: it is worth 7% of your final course grade. Accordingly, it is longer. Please write 4-4.5 pages of single-spaced content, not including references. References should take up less than 2/3 of a page. Due date: before 2:10pm on Wednesday November 28th. (Note: you may hand in up to one week late if you accept the 4% per business day lateness penalty. Essays handed in late will be graded late.)

Context

In 2003-4, a new PBS science TV documentary aired: a three-part NOVA series “Elegant Universe” about string theory starring Professor Brian Greene. Your humble professor in a blue shirt also makes a few short appearances in these videos (as the only researcher at a Canadian institution interviewed, and one of very few women), but that’s not why I’m assigning watching it as homework!   This NOVA series is very professional-looking, with absolutely awesome animations; it constitutes a good learning tool and we’re going to start making use of it now.

Question

Watch the first episode of the NOVA documentary series and the first quarter or so of the second episode. (Note: you are welcome to watch more of the three videos than this much, but I am not expecting you to write about the origins of string theory or anything about string duality here!)

(a) Give a summary of what you learned from watching the NOVA videos. Emphasize the things that the documentary explained particularly well and the things that helped your physics understanding the most.[40%]

(b) How does superstring theory unify all forces and matter together?  In particular, describe in detail how superstring theory has both gauge (massless spin 1) and gravity (massless spin 2) modes. [30%]

(c) How does superstring theory resolve the gigantic clash of titans between General Relativity and Quantum Mechanics?  Focus on the way in which string theory smoothens out gravitational interactions, as compared to particle theory, mending the sicknesses of quantum general relativity. [30%]