  The traceroute utility on any computer connected to the Internet can be used
to record the roundtrip time for small Internet packets between major Internet
traffic hubs. Some of the routes include transmission over transoceanic fiber
optic cable. We report on traceroute's use by students to quickly and easily
estimate the size of the Earth. This is an inexpensive way to involve
introductory physics students in a hands-on use of scientific notation and to
teach them about systematics in data.
