Physics 7.1 (Solar System)

Earth is tilted 23.5° anticlockwise

Sidreal day: time taken for a distant star to return to the same position in the sky (Earth spins 360°), this takes 23hours 56minutes

Solar day: time taken for the sun to return to the same position in the sky (Earth spins over 360°), this takes 24hours

Used to determine where a star is (it doesn't rotate with the Earth)

Vernal equinox reference point Right ascention measures angle East from the vernal equinox Declination measures angle of the star above or below the celestial equator

Angles: 60 seconds in a minute, 60 minutes in a degree, 360 degrees in a circle (Degree = 3600 seconds)

Lunar eclipse Earth blocks sun from the moon and so the moon appears to vanish

Solar eclipse The sun and the moon have the same angular size so the moon is able to block the sun but because the moon orbits at an angle it happens infrequently

Heliocentric model Sun at the centre of the solar system

Geocentric model Earth is at the centre of the solar system

Evidence: Phases of Venus, retrograde motion of Mars (Earth surpasses Mars in it's orbit so Mars appears to move backwards in the sky)

(Angular size = conversion factor * width of image)