Editing Axial tilt (section)

=== Seasons ===
{{main|Season}}
[[File:Earth tilt animation.gif|thumb|An illustration of [[axial parallelism]]. The axis of Earth remains oriented in the same direction with reference to the background stars regardless of where it is in its [[Earth's orbit|orbit]]. Northern hemisphere summer occurs at the right side of this diagram, where the north pole (red) is directed toward the Sun, winter at the left.]]
[[Earth]]'s axis remains tilted in the same direction with reference to the background stars throughout a year (regardless of where it is in its [[orbit]]) – this is known as [[axial parallelism]]. This means that one pole (and the associated [[Hemispheres of the Earth|hemisphere of Earth]]) will be directed away from the Sun at one side of the orbit, and half an orbit later (half a year later) this pole will be directed towards the Sun. This is the cause of Earth's [[season]]s. [[Summer]] occurs in the [[Northern hemisphere]] when the north pole is directed toward and the south pole away from the Sun. Variations in Earth's axial tilt can influence the seasons and is likely a factor in long-term [[climate change (general concept)|climatic change]] ''(also see [[Milankovitch cycles]])''.

[[File:axial_tilt_vs_tropical_and_polar_circles.svg|thumb|center|420px|Relationship between Earth's axial tilt (ε) to the tropical and polar circles]]