Touch / drag the slider — watch the planet speed up near the Sun and slow down far away.
| Planet | Semi-Major Axis \(a\) (AU) | Eccentricity \(e\) | Orbital Period (yr) |
|---|---|---|---|
| Mercury | 0.387 | 0.206 | 0.241 |
| Venus | 0.723 | 0.007 | 0.615 |
| Earth | 1.000 | 0.017 | 1.000 |
| Mars | 1.524 | 0.093 | 1.881 |
| Jupiter | 5.203 | 0.048 | 11.862 |
\(d\) = distance between foci · \(L\) = length of the major axis
🌠 Phenomenon: Why does orbital velocity increase at perihelion, and why does Earth’s orbit appear circular despite being an ellipse?
1 · Pattern observed — How does the separation between the two foci change the orbit’s shape?
2 · Evidence from simulation — How does the \(e\) value relate to the change in orbital velocity between perihelion and aphelion?
3 · Mechanism — Use \(F_g = \frac{G m_1 m_2}{r^2}\) and kinetic vs. potential energy to explain the speed change.