SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/astro-kepler-second-law

Where does a planet move fastest in its elliptical orbit?

At perihelion, its closest point to the Sun.

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  1. At aphelion
  2. At perihelion ✔
  3. At every point equally

Why: Kepler's second law requires the Sun-planet line to sweep equal areas in equal times. The planet must cover a longer arc per unit time when it is nearer the Sun.

Huh, didn't know that: The same law makes a planet slowest at aphelion, its greatest distance from the Sun.

The dad joke
Planets hurry through perihelion because the Sun keeps them on a tight schedule.
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References

Answer: At perihelion. Kepler's second law requires the Sun-planet line to sweep equal areas in equal times. The planet must cover a longer arc per unit time when it is nearer the Sun.

  1. Orbits and Kepler's Laws science.nasa.gov/solar-system/orbits-and-keplers-laws
    The imaginary line joining a planet and the Sun sweeps out equal areas of space during equal time intervals.
    Checked 2026-10-10.

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