Rotating Earth Sunlight animations © Swinburne

Star Trails due to Earth’s Rotation

The Celestial Sphere and Celestial Poles north celestial pole The Celestial Sphere and Celestial Poles Celestial Sphere south celestial pole

… which is an extension of the Earth’s equator. north celestial pole “celestial equator” … which is an extension of the Earth’s equator. south celestial pole

We can also project the Earth’s imaginary longitude north celestial pole We can also project the Earth’s imaginary longitude and latitude lines onto the celestial sphere The corresponding celestial coordinates are: Longitude  right ascension (RA) Latitude  declination (dec) south celestial pole

Phases as seen from Earth Phases of the Moon Third quarter A B C D E F G H Sun’s rays New moon Full moon First quarter A B C D E F G H Phases as seen from Earth

The Earth Orbits Around the Sun The Earth takes one year to make a complete orbit around the Sun.

1 AU = distance between Earth and Sun = 1.495979 x 108 km

zodiacal constellations

The Earth’s rotational axis is tilted by 23 The Earth’s rotational axis is tilted by 23.5° with respect to a line drawn perpendicular to the plane of the ecliptic. 23.5° Earth’s rotation axis plane of the ecliptic

Let’s have a look how it works during the course of a year: northern spring northern summer northern hemisphere winter southern autumn southern winter northern autumn southern hemisphere summer southern spring

Northern hemisphere in summer ... equator rotation axis sunlight