“Why are there

seasons?”GEMS Space Science Unit 2

Unit 2 Key ConceptsThe distance between the Sun and the Earth is so great if you had the model of the Sun, the size of a pea, on drawn on a piece of paper, the Earth would be off the page.

Day and Night Cycle

Unit 2 Key ConceptsScientists use models to demonstrate ideas, explain observations, and make predictions.

Unit 2 Key ConceptsEarth travels around the Sun in a nearly circular orbit called an ellipse.

Unit 2 Key ConceptsThe Sun is very close to the center of Earth’s orbit.

Unit 2 Key ConceptsPatterns of average-temperature change (and seasons) are opposite for the Northern and Southern Hemispheres.

Summer in the Northern Hemisphere

Winter in the Northern Hemisphere

Unit 2 Key ConceptsEarth’s tilt does not significantly change its distance from the Sun.

Unit 2 Key ConceptsScientific explanations are based on evidence gathered from observations and investigations.

Unit 2 Key ConceptsFor any given latitude, spring and summer days have more hours of daylight, and fall and winter nights are longer.

Unit 2 Key ConceptsIn the Northern and Southern Hemispheres, day-length changes (and seasons) are opposite one another during the year.

Unit 2 Key ConceptsDay-length changes are more dramatic farther away from the Equator.

Unit 2 Key ConceptsEarth’s tilted spin axis causes seasonal changes in hours of daylight and night throughout the year.

Unit 2 Key ConceptsAt the beginning of summer, sunlight falls at a steep angle and shines most intensely on Earth’s surface.

Unit 2 Key ConceptsAt the beginning of winter, sunlight falls at a shallow angle and shines least intensely on Earth’s surface.

Unit 2 Key ConceptsEarth’s tilt causes sunlight to strike the ground at steeper angles in summer and shallower angles in winter.

Unit 2 SummaryThe seasons are not caused by variations in Earth’s distance from the Sun. Earth’s spin axis remains tilted toward Polaris as it orbits the Sun.

Unit 2 SummaryEarth’s tilt does not significantly change its distance from the Sun.Seasons are caused by Earth’s tilt, which affects the intensity of sunlight and the number of daylight hours at different locations on Earth.

Unit 2 Key Concepts

The Seasons