Why do U.S. representatives serve shorter terms than U.S. senators?

Why this is the answer

Because the House was designed to be the part of the federal government closest to the people. A representative who faces the voters every two years has to keep track of what the district thinks, so the House follows public opinion closely. The Senate's six-year terms were designed for the opposite quality, steadiness. The Federalist Papers made the argument: frequent elections are what keep the House dependent on, and in sympathy with, the people. Memory hook: two years means quick to answer to the public.