5 Chapter Task Parallax Parallax is the apparent displacement of an object when it is viewed from two different positions. parallax apparent image angle of the Moon Moon I ruler Earth apparent image of the Moon Astronomers measure the parallax of celestial bodies to determine how far those bodies are from Earth. On October 28, 2004, three astronomers (Peter Cleary, Pete Lawrence, and Gerardo Addiego) each at a different location on Earth, took a digital photo of the Moon during a lunar eclipse at exactly the same time. The data related to these photos is shown. Shortest Distance on Earth's Surface Between Two Locations Parallax Angle AB (Montreal, Canada to Selsey, UK) 5 220 km 0.7153 AC (Montreal, Canada to Montevideo, Uruguay) 9 121 km 1.189 BC (Selsey, UK to Montevideo, Uruguay) 10 967 km 1.384 ? What is the most accurate method to determine the distance between the Moon and Earth, from the given data? . Sketch a triangle with the Moon and locations A and B as the vertices. Label all the given angles and distances. What kind of triangle do you have? Task Checklist B. Determine all unknown sides to the nearest kilometre and angles to the Did you draw the correct nearest thousandth of a degree. How far, to the nearest kilometre, is the sketches? Moon from either Montreal or Selsey? Did you show your work C. Repeat parts A and B for locations B and C, and for A and C. Did you provide approp D. On October 28, 2004, the Moon was about 391 811 km from Earth (surface reasoning? to surface). Calculate the relative error, to the nearest tenth of a percent, for Did you explain your all three distances you calculated. thinking clearly? E. Which of your results is most accurate? What factors contribute most to the error in this experiment? Trigonometric Ratios NEL