Catching the Shake of Space: teacher key

Gravity, grade 11 edition, written for 11th grade. From a falling apple to wobbles smaller than an atom, see how gravity's tests grew more sensitive and what they found.

Read the book. Print this page for the key.

Questions and answers

1. How long does it take the Moon to fall about 1.4 millimeters toward Earth?
   • One second (answer)
   • One hour
   • One year
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 heavier
   • They are colder
3. What did Taylor and Weisberg find in 1982?
   • A binary pulsar orbit slowly shrinking because of gravitational waves (answer)
   • A new planet
   • A black hole eating stars
4. What did the Livingston detector's 7 millisecond lead show?
   • The source was in the Southern Hemisphere (answer)
   • LIGO had a flaw
   • The wave was a sound
5. What did Vera Rubin study in the 1970s?
   • Comets
   • Stars at the outer edges of spiral galaxies (answer)
   • Eclipses

Words

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