Orbits
Circles, ellipses, and the quiet geometry of things in motion. An experiment in seeing the paths we cannot see.
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A familiar beginning.
When both focal points meet, the ellipse becomes a circle. Every point along the curve is the same distance from the centre.
A simple shape, and a useful place to begin looking.
A small deviation.
Separate the focal points and the circle stretches into an ellipse. Eccentricity describes how far this shape departs from a circle.
The line becomes a way to see a relationship: distance, position, and the space between two points.
Same rule. Another shape.
Increase the eccentricity and the ellipse grows narrower. At every point on its edge, the sum of the distances to the two foci stays constant.
This is a schematic illustration of shape, rather than a simulation of a moving body.