The Ground Under You Is Turning: teacher key

Day and Night, grade 7 edition, written for 7th grade. The Sun looks like it travels across the sky, but it is Earth that turns. Read how that turn makes day and night, clock time and body clocks.

Read the book. Print this page for the key.

Questions and answers

1. What is the line between daylight and darkness called?
   • The equator
   • The terminator (answer)
   • The meridian
2. How long does one turn of Earth against distant stars take?
   • 24 hours exactly
   • 23 hours, 56 minutes and 4 seconds (answer)
   • 25 hours
3. Which pair came from Earth's tilt as it goes around the Sun?
   • Day and night
   • The seasons (answer)
   • Jet lag
4. Why did railroads need standard time?
   • Towns set clocks by their own Sun, so travel needed a uniform time system (answer)
   • Trains were too slow
   • The Sun stopped moving
5. Which of these animals is diurnal?
   • Owl
   • Squirrel (answer)
   • Sea turtle hatchling
6. What does the hormone melatonin do?
   • Makes people sleepy (answer)
   • Keeps people awake
   • Makes plants flower

Words

• terminator: day-night line
• twilight: glow after sunset
• sidereal: measured by stars
• equinox: equal day, night
• diurnal: active by day
• melatonin: sleepy hormone