Gravity on Trial: teacher key

Gravity, grade 10 edition, written for 10th grade. Scientists have tested gravity with eclipses, atomic clocks, lensed galaxies and moving stars. See what the tests showed and what they left open.

Read the book. Print this page for the key.

Questions and answers

1. What did the GRACE spacecraft measure?
   • Variations in Earth's gravity (answer)
   • Sea salt
   • Moon dust
2. Why do GPS satellite clocks run faster than clocks on Earth?
   • Weaker gravity speeds them up by more than orbital speed slows them (answer)
   • They are bigger
   • They use batteries
3. What did Einstein ask astronomers to watch in 1911?
   • Comets
   • Total solar eclipses (answer)
   • Meteor showers
4. What won the 2020 Nobel Prize in this story?
   • Finding dark matter
   • Tracking stars to show a supermassive black hole at the Milky Way's center (answer)
   • Measuring G
5. What did Fritz Zwicky suggest in 1933?
   • An invisible form of matter (answer)
   • A new planet
   • A bigger Sun

Words

• precession: orbit slowly turning
• lensing: light bending
• microseconds: millionths of seconds