🛰 Kepler’s laws: the rules of orbits

Unit 1 · Our cosmic neighbourhood · 10 min

Kepler found: (1) planets move on ellipses with the Sun at one focus; (2) a planet speeds up near the Sun and slows down far away; (3) the farther a planet is, the longer its year. Earth takes one year; Neptune about 165.

Words in this lesson

• 椭圆 (tuǒyuán) — ellipse
• 太阳 (tàiyáng) — the Sun

Project: Draw an ellipse with two pins, a loop of string and a pencil; one pin is the Sun.