Teaching Notes

Probably the greatest challenge for the students in this activity is thinking in terms of light travel-time. You can help the students by discussing the progression of travel-times the students calculate in Step 2. Also, when the students make the time-line of Earth history, you can point out the age of the Earth is 4.5 billion years. You may have to suggest a logarithmic graph, with each scale marking indicating a multiple of ten in the time.