Angular Size

How big things look

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Angular size $\theta \approx \text{size}/\text{distance}$ (radians).
• The Moon and the Sun both appear about 0.5° across.
• Magnification is a ratio of angular sizes.

Steps

1. Size divided by distance
2. The Moon
3. Cover the Moon
4. What magnifiers do
5. The space station overhead
6. Jupiter’s disc