The Clock Set by the Sun: teacher key

Day and Night, grade 6 edition, written for 6th grade. Earth's spin makes day and night, and people set their clocks by it. Other worlds have much stranger days.

Read the book. Print this page for the key.

Questions and answers

1. About how long is a solar day on Venus, from one noon to the next?
   • 117 Earth days (answer)
   • 24 hours
   • 243 hours
2. Why were standard time zones needed?
   • Owls needed them
   • The Moon moved away
   • Railroad travel made them necessary (answer)
3. Which planet is tipped on its side?
   • Mars
   • Uranus (answer)
   • Jupiter
4. What does nocturnal mean?
   • Very far away
   • Active by day
   • Active at night (answer)
5. Which can disturb sleep?
   • Even dim light at night (answer)
   • Cool air
   • Quiet

Words

• meridian: north-south line
• circadian: 24-hour body clock
• nocturnal: active at night
• terminator: day-night line
• equinox: equal-day time