Skip to main content
Twinkling Stars: How Light Bends in Air

Twinkling Stars: How Light Bends in Air

Ages 6-1210-15 minutesEasy Difficulty

About This Activity

Learn why stars twinkle in the night sky by simulating how light bends when it moves through air and water.

Materials Needed

  • A clear glass of water
  • A pencil or straw

Safety Notes

  • Handle the glass carefully to avoid spills or breakage.
  • Ensure the glass is placed on a stable surface to prevent tipping.

Instructions

  1. Fill a clear glass with water.
  2. Place a pencil or straw inside the glass.
  3. Look at it from the side. Notice how it appears bent or wavy?
  4. This is similar to how starlight bends when it passes through Earth's atmosphere.

How It Works

Stars twinkle because their light passes through Earth's moving atmosphere, causing it to bend and shift. This bending, or refraction, makes stars appear to twinkle. The same effect happens when light moves through water, which you can see by looking at the pencil in the glass.

Tips for Success

  • Try using a spoon instead of a pencil for a different effect.
  • Observe the twinkling stars at night and compare them to steady planets.
  • Try looking through wavy or heated air to see similar bending effects.