Axial Tilt

The Reasons For The Seasons

“File:AxialTiltObliquity.png” by Dna-webmaster is licensed under

By: Allen Chhu, Journalist

The axial tilt, also called obliquity, of a planet is the amount of degrees off a planet spins relative to the perpendicular ecliptic which is the plane of it’s orbit around it’s star. For example, Venus’ axial tilt is almost 180 degrees so it spins backwards and almost straight up while Uranus’ tilt is roughly 97 degrees so it spins on it’s side. The axial tilt of a planet also effects many things on the planet most notably the seasons, tropics, and polar circle. Earth’s axial tilt is roughly 23.5 degrees but what if it was different and how would that effect things?

First of all, it’s common knowledge that the earth has season because of it’s obliquity which tilts the earth throughout the year. The same amount of light hitting a greater amount of area causes colder temperatures and the more light hitting a smaller area causes warmer temperatures, hence seasons. If the tilt of the earth was zero degrees then there would be no seasons as the change in sunlight to surface area wouldn’t exist. Likewise, if the tilt of the earth was 90 degrees then the seasons would just cause one half of the earth to face the sun while the other faces away so winter would be always night while summer is always day.

The axial tilt of a planet will also affect the tropics and polar circles of a planet but what are the tropics and polar circles. Well, the tropics of a planet are where the sun will be directly overhead that latitude for a day and the polar circles of a planet will be where a latitude of a planet will be facing away from the sun for an entire day. The location of the tropic and polar circles depend entirely on the tilt of the planet. The tropics are simply calculated as the degrees of axial tilt north and south of the equator so for earth that’s 23.5 degrees north and south. Meanwhile, the polar circles are calculated as the degrees of axial tilt subtracted from 90 so that would be 90-23.5=66.5 for the earth.

In conclusion, the axial tilt of a planet effects many things from the tropics, polar circles, and the seasons. If the tilt of the earth changed, it would affect all of these factor disrupting everything on our planet.