Timing the Transit of Venus.


During the four previous transits of Venus in 1761, 1769, 1874 and 1882 astronomers carefully noted the start and stop times of the passage of Venus across the face of the Sun. When these times were combined with the latitude and longitudes of the various observers, astronomers could calculate the distance between Earth and Venus in terms of actual miles using the properties of triangles. This is similar to the method used by surveyors to determine the distance to remote, or inaccessible, objects on the surface of Earth.

In this activity, students will use the actual transit times recorded by astronomers during the 1882 and 1874 transits to determine the duration of the transit, and the time intervals between specific moments in the transit called 'Contacts'.


The graphical display of numbers may help to show patterns such as trends or varying rates of change. Such patterns sometimes can be used to make predictions about the phenomenon being graphed.


Students will calculate elapsed time and look for patterns.





 1st Contact

 2nd Contact

 3rd Contact

 4th Contact


  1. Review the 24-hour clock. Cover the vocabulary needed in the Vocabulary Transparency Master. Discuss the conversion factors. These items can be found on the Time Conversion Transparency Master .
  2. Use the example of the time calculations provided in the Professor Frisbee Time Calculation Example to explain the time calculation process.
  3. Provide time to allow the students to complete the calculations for Professor Hubert and Professor Compton.
  4. Review the answers for the elapsed time for the 1882 transit times by Professor Hubert and Professor Compton. Be sure to discuss the conversions.
  5. Look for any similarities in the elapsed times for the three observations. Discuss why there may be some differences in observing times and determine if there is a statistical difference for any of the times.
  6. Provide the students with time to complete the 1874 transit observations worksheet for Professor Frisbee, Hubert and Compton.
  7. Review the answers for the elapsed time for each of the observations in 1874. Look for patterns and similarities in the elapsed time for the observations. Determine if there are any observations that do not seem to fit the pattern. Discuss possible reasons for the error in measurements.