13. Kepler's third law Unit 122) describes planetary orbital sizes relative to Earth's orbit, which is assigned a size of 1 AU. One method for finding absolute orbital sies is to use radar
ranging between planets. Use Venus's scaled orbital size of 0.723 AU, and the observation that a radar signal takes 276 sec to make a round-trip between Earth and Venus when
they are minimally separated, to find how many kilometers are in an AU