Hostname: page-component-78c5997874-dh8gc Total loading time: 0 Render date: 2024-11-06T10:35:57.856Z Has data issue: false hasContentIssue false

The Elliptical Orbit of the Earth

Published online by Cambridge University Press:  03 November 2016

Extract

Preliminary note. Beginners find two ways of regarding an ellipse easy to understand. The first presents it as the curve traced out by a point P (Fig. 1) when r + r′, the sum of P’s distances from two fixed points F and F′, is a constant, 2a. From this definition come the equivalences AA′ = 2a, CA = CA′ = a, and CF = CF′ = ae, where e is a fraction less than unity C is the “centre” of the ellipse, F and F′ its “foci”, CA = a the “semi-axis major”, CB = b the “semi-axis minor”, and e the “eccentricity”

Type
Research Article
Copyright
Copyright © Mathematical Association 1941

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Page 280 of note * At the beginning of the seventeenth century it was much easier to observe that the sun’s movement along its apparent annual path varies in speed. The theory of the elliptical orbit started from such observations, but those assumed in this article are vastly easier to treat mathematically.

Page 282 of note * Strictly speaking, the entries in the Nautical Almanac are not records but predictions. But, being based upon records of observations and amply verified by later observations, they may for our purpose be regarded as records of measurements made.