Light, Dark and the Body Clock: teacher key

Day and Night, grade 5 edition, written for 5th grade. The Earth's spin makes day and night, and the tilt makes the seasons. Living things, and people, keep time by it.

Read the book. Print this page for the key.

Questions and answers

1. What is the line between daylight and darkness called?
   • The terminator (answer)
   • The equator
   • The solstice
2. What do the seasons come from?
   • Earth's spin
   • The Moon
   • Earth's tilt as it goes around the Sun (answer)
3. What makes people sleepy in the evening?
   • Jet lag
   • Melatonin (answer)
   • Twilight
4. Why does jet lag happen?
   • Planets spin
   • The Sun moves faster
   • The body clock no longer matches local day and night (answer)
5. On which planet would the Sun rise in the west?
   • Venus (answer)
   • Mars
   • Jupiter
6. What does hemisphere mean?
   • A long day
   • Half of the Earth (answer)
   • A spinning planet

Words

• terminator: day-night line
• equinox: equal-day time
• melatonin: sleepy hormone
• hemisphere: half of Earth
• circadian: 24-hour body clock