Elliptical Kepler orbit (a) and orbit squeezed into a circle (b) from scaling the x-axis by b/a. The travel time from r⁰ to r¹ is equal to the ratio of the swept (cyan) area in (a) to πab times the period. In (b), this ratio is the (yellow) circle segment plus the (gray) triangle minus the image of the (gray) triangle in (a) over πb². The circle segment has area ΔEb²/2, with ΔE = E¹ − E⁰ being the difference in eccentric anomaly.