How do we determine distances between the earth, sun, and moon, and from the sun to other planets, stars, and distant galaxies? We can't measure these directly, but indirect methods, combined with some basic high school math, can provide convincing and accurate results. Climb a "cosmic distance ladder" with UCLA Professor of Mathematics and 2006 Fields Medalist Terry Tao, as he shows us how measurements of nearby distances can be used to estimate distances that are out of this world. Terry will be introduced by Michael Sipser, Barton L. Weller Professor of Mathematics and Head of the Mathematics Department at Massachusetts Institute of Technology.