Why does earth's distance from the sun change?

Question

Asher Cohen · Accepted Answer

The Earth's orbit around Sun is under a central force that is inversely proportional to square of distance from Sun.The orbit is not a circle but an ellipse with Sun at one focus.

The distance #r# changes according to the formula
#l/r = 1 + e cos (theta)#
where #e# is the eccentricity of the ellipse,
#l = (("minimum distance")("maximum distance"))/("semi major axis of the ellipse")#.
#theta# is the inclination of Sun-Earth radius to least-distance radius.

Luke Allen · Answer

Thanks for the depiction. The Sun's distance CS = ae from center C is 1 in 60 of the semi-major a. So, for orbit on an A4 paper, S will be quite close to C.

The orbit, when drawn to scale on A4 paper, will appear as a circle. Naturally, some elongation is required to show what it is, an ellipse. e = 0.01671. CS/a = 0.01671. Minor axis b is 0.99986a.

Alexander Acosta · Answer

undefined Since Earth has an elliptical orbit—one in which the Sun is at one of its foci—it is not a perfect circle; rather, it is an ellipse whose orbital path causes it to vary in distance from the Sun, with perihelion—the closest point on Earth's orbit—and aphelion—the furthest point—due to gravity and the geometrical features of Earth's orbit.