Ecliptic — The ecliptic is the geometric plane that contains the orbit of the Earth. The orbits of most planets in the Solar System lie very close to it.

Seen from the Earth, this is the great circle on the celestial sphere that contains the different positions of the Sun relative to the background stars throughout the year, and most planets can be seen close this circle.

The zodiac also lies along the plane of the ecliptic.

Because there are about 365.25 days in a year and 360 degrees in a circle, the Sun appears to move along the ecliptic at a rate of about 1 per day. This motion is from west to east, in opposition to the apparent east-west movement of the celestial sphere.

The ecliptic and the celestial equator intersect at two points, directly opposite one another. These are the equinoxes and when the Sun appears at these points, day and night are each about 12 hours long at all locations on Earth.

The point on the ecliptic that is farthest north of the celestial equator is called the summer solstice in the northern hemisphere, and the winter solstice in the southern hemisphere. When the Sun is farthest south of the celestial equator the reverse is true.


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