Document page
igcse physics notesprinted 121 · PDF 121
124 pagesrevision 46936
printed 121 · PDF 121
Page image rendered from the stored file at 110 dpi; it sharpens as you zoom. Outlines are placed from each region’s stored position on the page (612 × 792 pt).
readable
Source of this text: embedded text layer. The better of the embedded text and OCR is kept.
121
Unit 6: Space Physics
The Earth's Axis
The Earth is a rocky planet that rotates in a near circular orbit around the Sun It rotates
on its axis, which is a line through the north and south poles The axis is tilted at an
angle of approximately 23.5° from the vertical The Earth completes one full rotation
(revolution) in approximately 24 hours (1 day) This rotation creates the apparent daily
motion of the Sun rising and setting Rotation of the Earth on its axis is therefore
responsible for the periodic cycle of day and night Day and Night The Earth's rotation
around its axis creates day and night Day is experienced by the half of the Earth's
surface that is facing the Sun Night is the other half of the Earth's surface, facing away
from the Sun
Rising and Setting of the Sun
The Earth's rotation on its axis makes the Sun looks like it moves from east to west At
the equinoxes the Sun rises exactly in the east and sets exactly in the west Equinox
(meaning 'equal night') is when day and night are approximately of equal length
However, the exact locations of where the Sun rises and sets changes throughout the
seasons In the northern hemisphere (above the equator): In summer, the sun rises
north of east and sets north of west In winter, the sun rises south of east and sets south
of west
The Sun is highest above the horizon at noon (12 pm) In the northern hemisphere, the
daylight hours are longest up until roughly the 21st June This day is known as the
Summer Solstice and is where the Sun is at its highest point in the sky all year The
daylight hours then decrease to their lowest around 21st December This is known the
Winter Solstice and is where the Sun is at its lowest point in the sky all year
The Earth's Orbit
The Earth orbits the Sun once in approximately 365 days This is 1 year The
combination of the orbiting of the Earth around the Sun and the Earth's tilt creates the
seasons