Description

This simulation illustrates two different perspectives on the apparent daily rotation of the sky. The top view shows the Earth at the center, with a green horizon and white zenith line drawn for an observer on the equator. East and West directions are indicated along the horizon line. In addition, this view shows a set of stars on the celestial sphere, with one star highlighted in magenta.

The bottom view shows a stretch of the sky as seen by the observer on Earth. The portion of the sky shown runs from the observer's eastern horizon to the western horizon along the celestial equator.

When the Rotating Earth button is selected, the top view shows a rotating Earth and a stationary celestial sphere. when the Rotating Celestial Sphere button is selected, the top view shows a stationary Earth and rotating celestial sphere. In both cases the bottom view is the same.