Description

This simulation shows a simplified version of Copernicus' model for the orbit of the Earth around the Sun. The top view shows a 3D depiction of the celestial sphere with the Sun at center. The Earth orbits in a circle centered on the Sun. The Earth's rotational axis is shown, with labels to indicate the north and south celestial poles. Note that the simulation is not to scale. The celestial sphere should be vastly larger than Earth's orbit while the Earth and Sun should be imperceptible compared to Earth's orbit.

Controls allow the user to play/pause, step, reset, or erase the simulation. Sliders allows the user to adjust the time of year, the ratio of the size of Earth's orbit to that of the celestial sphere (which in reality should be approximately zero), and the tilt of Earth's rotational axis. Buttons let the user select a particular day: vernal equinox (VE), summer solstice (SS), autumnal equinox (AE), or winter solstice (WS). The user can also choose whether or not to display various visual elements and/or use the true tilt of Earth's axis.

Four bright stars near the ecliptic can be highlighted for reference: Antares (red), Aldebaran (magenta), Castor (yellow), and Regulus (cyan). Polaris can be found very close to the north celestial pole when the true tilt of the Earth's axis is used.