Concept
Axial tilt
Overview
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbital plane. It differs from orbital inclination.
At an obliquity of 0 degrees, the two axes point in the same direction; that is, the rotational axis is perpendicular to the orbital plane.
The rotational axis of Earth, for example, is the imaginary line that passes through both the North Pole and South Pole, whereas the Earth's orbital axis is the line perpendicular to the imaginary plane through which the Earth moves as it revolves around the Sun; the Earth's obliquity or axial tilt is the angle between these two lines.
Over the course of an orbital period, the obliquity usually does not change considerably, and the orientation of the axis remains the same relative to the background of stars. This causes one pole to be pointed more toward the Sun on one side of the orbit, and more away from the Sun on the other side—the cause of the seasons on Earth.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
Found by search and not yet checked by a person; they may only mention the idea in passing.
At other times they are both directed towards the object we are viewing, whereby they converge, so as to make the lines proceeding from each eye to the exact point of the object on which it is fixed, form an _angle_, called the _optic angle_; the lines themselves are called _optic axes_. Now, when the object lies straight before us, these lines exactly impinge upon the centre of each retina, therefore in two points…
Arthur Schopenhauer, On the Fourfold Root of the Principle of Sufficient Reason, and On the Will in Nature
States what Axial tilt is.
As the Moon revolves in an ellipse, which has the centre of the {381} Earth in one of its foci, the longer axis of its orbit is called the Line of its Apsides. This line is found, by observation, not to be always directed towards the same points of the Firmament, but to revolve forwards from west to east, so as to pass through all the points of the Ecliptic, and to complete…
Adam Smith, The Essays of Adam Smith
States what Axial tilt is.
Let the sun shine diagonally into an empty cubical vessel, so that the opposite side be illumined, but not the bottom: let water be then poured into this vessel, and the direction of the light will be immediately altered; for a part of the bottom is shone upon. At the point where the light enters the thicker medium it deviates from its rectilinear direction, and appears broken: hence the phenomenon is called the…
Johann Wolfgang von Goethe, Goethe's Theory of Colours
States what Axial tilt is.
Philosophers who discussed Axial tilt
Related ideas
- Macmillan Publishers
- Mantle (geology)
- Middle Ages
- Neptune
- Moon
- Mercury (planet)
- Sun
- Solar System
- Nature (journal)
- Uranus
- Celestial sphere
- Astronomy
- Denmark
- Gnomon
- Earth
- Ecliptic
Place in the tradition
Part of Anaximander.