Activity: Possible Worldlines

Student consider several curves on a spacetime diagram and have to judge which curves could be worldlines for an object.
What students learn
  • Speed on a spacetime diagram is inverse slope.
  • Object can't travel faster than the speed of light.
  • Lightlines have a slope of 1 (when axes are scaled to the same units)
  • Media
    • activity_media/possibleworldlines.key
    • activity_media/possibleworldlines.pdf
    • activity_media/possibleworldlines.001.png
    • activity_media/possibleworldlines.002.png

Student Conversations

  • Speed is Inverse Slope Students have trouble fighting their intuitions about speed being the slope on a graph.
  • Time Measured in Units of Length Some students are thrown by multiplying the time coordinate by a speed to get units of distance. This just takes a while to sink in.

Learning Outcomes