The Seasons

Question 1: How long does it take the earth to complete one rotation around its axis?

Answer 1: 24 hours

Question 2: How long does it take the Earth to complete one rotation around the sun?

Answer 2: 365.25 days (The extra 0.25 day is accounted for by a leap year every four years)

Question 3: What is the cause of the Earth’s seasons?

Answer 3: The seasons are the result of the tilt of the Earth's axis as the Earth travels around the sun The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year (these differences are extremely small)

Earth’s axis The Earth's axis is tilted at 23.5° angle Axis points to North Star This tilting is what gives us the four seasons

Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year

Seasons animation http://esminfo.prenhall.com/science/geoanimat ions/animations/01_EarthSun_E2.html https://highered.mcgraw- hill.com/sites/007299181x/student_view0/cha pter2/seasons_interactive.html

Illumination of Earth during various seasons  June May  Sept  Dec

Solar energy Summer is warmer than winter (in each hemisphere) because the Sun's rays hit the Earth at a more direct angle during summer than during winter and also because the days are much longer than the nights during the summer. During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.

Why does the Earth tilt? The tilt of the earth is a result of collisions with large bodies during the formation of the planets in the solar system. The size of the bodies and the angle of collision determined the tilt and the rotation of the planets. Each planet has a different tilt with respect to the planet's plane of the ecliptic.