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ellipse

An ellipse is a planar curve. All points on the curve are located around two focal points, such that the sum of the distances to each focal point is equal for all points.

Special cases of an ellipse are a circle (in this special case, both focal points are at the same location) and a straight line joining the two focal points (in this special case, the specific distance chosen is equal to the distance between the two focal points).

As far as gravity is concerned, ellipses are of interest as the orbit of a lonely planet around a central star is an ellipse, according to Newton’s theory of gravity.

Definitioner

straight line

In the plane, in three-dimensional everyday space or in more general flat spaces: Any line that forms the shortest connection between two given points. In the spacetime of special relativity: The world-line of an object moving with constant speed on a path that is straight in space.

point

Elementary "building block" of geometrical entities such as surfaces or more general spaces. For instance, a surface is the set of all its points, of all possible locations on the surface, and all geometrical objects in that surface are defined by the points that belong to them - for instance, a line on the surface is the set of (infinitely many) points.

line

Geometric object with a single dimension. A line can either be an independent one-dimensional space (in the abstract mathematical space where a space does not need to have three dimensions), or it can be embedded into a more general space, like a line drawn onto a piece of paper (i.e. a surface).

ellipse

An ellipse is a planar curve. All points on the curve are located around two focal points, such that the sum of the distances to each focal point is equal for all points. Special cases of an ellipse are a circle (in this special case, both focal points are at the same location) and a straight line joining the two focal points (in this special case, the specific distance chosen is equal to the distance between the two focal points). As far as gravity is concerned, ellipses are of interest as the orbit of a lonely planet around a central star is an ellipse, according to Newton's theory of gravity.

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ellipse

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