FIGURE ILLUSTRATING THE CHANGE OF SEASONS THROUGHOUT THE YEAR
The change of seasons is caused by the revolution of the earth around the sun, and the inclinations of the planes of the equator and ecliptic. These causes also account for the difference in the length of the days and nights and the difference in the height of the midday sun. The exact duration of the seasons we get by observing the dates of equinoxes and solstices.
FIGURE SHOWING THE CAUSE OF DAY AND NIGHT
The revolution of the earth gives us the length of the year; its rotation on its axis, the length of the day and night, by causing the risings and settings and daily apparent motion of the sun and stars.
EFFECT OF UNEQUAL DAYS AND
NIGHTS ON TEMPERATURE
The inequality in the length of the days in different parts of the year, occasioned by the inclination of the Earth’s axis, is of itself sufficient to produce a marked variation in temperature.
During the day the Earth receives from the Sun more heat than it radiates into space; while during the night it radiates more than it receives. Hence a succession of long days and short nights results in an accumulation of heat, raising the average temperature and producing summer; while long nights and short days result in a temperature below the average, producing winter.