Max and min orbital speed
SMRTR summary
The ratio of a planet's maximum to minimum orbital speed is (1 + e)/(1 - e), with e being the orbit's eccentricity. For small eccentricities, this approximates to 1 + 2e. Earth's orbital speed varies by 3% (e = 0.0167), while Mars' varies by 19% (e = 0.0934). The function (1 - z)/(1 + z) has applications in impedance calculations, mental math, and ellipse perimeter calculations.
SMRTR provides this summary for quick context. The original article belongs to John D. Cook.
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