Why do the planets go around the sun?

1. 1

   Zib says

   Every planet is racing along through space. The sun is huge, and the more stuff something has, the harder its gravity pulls. So the sun keeps tugging on each planet, bending its path a little all the time. Bend a path again and again, and it curves right around. That's how the planets keep going around the sun.

   For ages 8–10
   Hear Zib

   Checked against What is gravity? (NASA Space Place)

2. 2

   Why doesn't the sun pull them all the way in?

   Each planet is always falling towards the sun. But it's also moving sideways so fast that it keeps missing. If it went slower, it would fall in. If it went faster, it would fly away. The planets move at just the right speed to keep falling around the sun, trip after trip.

   For ages 9–11
   Hear Zib

   Checked against What is an orbit? (NASA)

3. 3

   Is a planet's path a perfect circle?

   Each planet's path is an ellipse, which is a circle stretched out a little. So on every trip, a planet swings a bit closer to the sun, then a bit farther away. It zooms fastest at its closest point and slows down at its farthest.

   For ages 10–11
   Hear Zib

   Checked against Orbits and Kepler's laws (NASA Science)

In Lil' Phil, reaching the bottom of this wonder earns a sticker for Zib's collection.

• 

  How do astronauts float?

  Ages 8–11Zib
• 

  Why do we have seasons?

  Ages 8–11Zib