| In the orbit of a planet, means the line joining its aphelion and perihelion. |
| At present the earth is about three millions of miles nearer the sun in perihelion than in aphelion. |
| It goes without saying that the orbit of the moon would vary in accordance, expanding towards perihelion and contracting towards aphelion. |
| But it's not that simple either, because the dates of the perihelion and aphelion are also shifting. |
| The most energy efficient method of getting there is to launch oneself into an orbit whose aphelion reaches the orbit of Mars and whose perihelion is the orbit of the Earth. |
| The perihelion currently occurs in January and the aphelion in July. |
