PHY105 (Fall 1995)

Science for the 21st Century

Assignment 13

Due Friday, December 8, 1995 at the start of lecture

Read The Light Cone module Some of this assigment requires the use of the Web.

Then answer the following questions:

  1. Draw a spacetime diagram of the following scenario:
    1. Event A: Albert is asleep in his bed at 8am, and continues to sleep.
    2. Event B: Albert wakes up in his bed at 9am, and proceeds to walk with a uniform speed to school.
    3. Event C: Albert arrives at school at 10am, and remains seated in class.
    4. Event D: Albert leaves his seat at 11am, and quickly runs to the bathroom.
    5. Event E: Albert arrives at the bathroom at 11:01am. and quickly runs back to class.
    6. Event F: Albert arrives back in his seat at 11:02am, and remains seated in class.
    7. Event G: Albert leaves his seat at 11:30pm, and starts running back to his bed.
    8. Event H: Albert arrives at his bed at 11:45am, and goes back to sleep.

    9. Give an interpretation for the following spacetime diagram.

    10. For each of the following spacetime-models (Aristotle's, Galileo's, and Einstein's):
      1. Draw a neat picture of each spacetime-model.
      2. Fill in the table with the words "absolute" or "relative":
        elapsed time   
        spatial separation   
        "at the same place"   
        moving at uniform speed   
        being at rest   

    11. Using a search engine or the Syracuse Physics Department Web Server find information on the "the Binary Black Hole Grand Challenge" and on "LIGO". What is each about? For each, find a list of the participating institutions.

      1. What is a light cone?
      2. What is a worldline?
      3. Draw a picture of your light cone and your worldline.
      4. Why can't you leave your light cone?

      1. What is a black hole?
      2. Why can't you escape once you have crossed the event horizon?

    12. Relativity has been historically regarded as counterintuitive. Why do you think that is? Why can we get along in our everyday life (today) without relativity?