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Key facts

Earth

Earth is the third planet from the Sun and the only place in the universe where we know life exists. About 71% of its surface is covered by liquid water, and a thin blanket of air protects us from the cold and radiation of space.

International Space Station

The International Space Station is the biggest thing humans have ever built in space – a laboratory and home where astronauts from many countries live and work. People have been living on board without a break since November 2000.

The Moon

The Moon is Earth’s only natural satellite. Scientists think it formed about 4.5 billion years ago when a Mars-sized world crashed into the young Earth and the debris clumped together. Its gravity creates the ocean tides.

The Sun

The Sun is a star – a giant ball of hot gas. In its core, hydrogen atoms smash together to make helium, releasing the energy that lights and warms our planet. It holds about 99.8% of all the mass in the Solar System.

Quiz

1. About how long does sunlight take to reach Earth?

   • ☐ 8 seconds
   • ☐ 8 minutes
   • ☐ 8 hours
   • ☐ 8 days

2. Why do we always see the same face of the Moon?

   • ☐ The Moon doesn’t spin
   • ☐ It spins exactly once per orbit
   • ☐ Earth blocks the other side
   • ☐ The far side is invisible

3. Who measured the size of the Earth more than 2,000 years ago using shadows?

   • ☐ Galileo
   • ☐ Newton
   • ☐ Eratosthenes
   • ☐ Copernicus

4. How long does the International Space Station take to circle the Earth?

   • ☐ About 90 minutes
   • ☐ One day
   • ☐ One week
   • ☐ One month

Find it in the sky

Use the Sky Finder at seethestar.com. Tick what you find and write when you saw it.