(Lecture: 10 minutes)

• Application of surveyor's parable to spacetime
• Use same units
• Interval is invariant
• Conversion is Lorentz transformation

See §5.1 of the text.

This is the second of two short lectures based on the surveyor's parable. The first lecture introduced the parable in its Euclidean setting, where its consequences are rather obvious. This lecture discusses the implications for special relativity, setting the stage for the use of spacetime diagrams.

Both lectures can be given the same day, although it is quite effective to end one day with the first lecture, ask students to reflect on it, then begin the next class with an interactive version of the second lecture.