Lecture 43

Hatcher, ch. 0, sec 1 (p5 - 6), bit from chap 4.

Define Cell complex, aka CW complex. Give some of the examples on page 6. State, but do not prove, Whitehead's Theorem 4.5 on page 346. This illustrates the fundamental importance of homotopy groups for homotopy theory. This lecture might be a little short.