Earth rotates every 24 hours, giving sunlight to one side while the other side is in darkness. earth revolves around the sun every 365 days, with a one-day adjustment in our calendar every four years. Seasons occur because of the angle at which sunlight strikes the earth. Because the planet is always moving, the seasons change on a regular basis.

1. Vocabulary
 Seasons: Why do we have them?
Earth and Environmental Science
For NCVPS
Kella Randolph, M. Ed
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3. Direct sunlight – sunlight that strikes
Earth’s surface at close to a 90° angle.
Image courtesy of: 324x400-icp.giss.nasa.gov

4. Earth’s axis – an imaginary line through
the center of Earth that connects the
North Pole to the South Pole.
Image courtesy of: clasfaculty.ucdenver.edu1601 × 1135
Earth rotates about its axis once every
24 hours.
Earth’s axis is tilted at an angle of 23.5
degrees.

5. Equator
 Image courtesy of: scijinks.jpl.nasa.gov800 × 597
an imaginary horizontal line around the
middle of Earth.

6. Northern hemisphere – the half of
Earth north of the equator.
 Image courtesy of:
www.astronomy.org570 × 320

7. Hemispheres
 Image courtesy of: urbanext.illinois.edu900 × 600

8. North Pole – the northernmost point on Earth.
 Image courtesy of:
Earthobservatory.nasa.gov1280 × 720

9. Indirect sunlight – sunlight that strikes Earth’s
surface at an acute angle (less than 90˚).
 Image courtesy of: http://scijinks.jpl.nasa.gov/solstice

10. Season – one of the major divisions of the year,
usually based on regular weather changes.
In temperate places, the year is divided into four
seasons: winter, spring, summer, and autumn
(fall). Each season is three months long.
In tropical regions, average temperatures do not
change much during the year. In these regions, it
is common to refer to the “rainy season” and the
“dry season.”
Image courtesy of: http://1.bp.blogspot.com/-
V1748xphwI8/UMRn83Bq_fI/AAAAAAAAAgw/TtrGR_sW5js/s1600/seasons.jpg
This Photo by https://www.otherworldlyincantations.com/wp-
content/uploads/otherworldly-incantations-forest-worldbuilding-
monsoon-season.png

11. Southern hemisphere – the half of Earth south
of the equator.
 This photo courtesy of: http://urbanext.illinois.edu/treehouse/seasons.cfm?Slide=6

12. South Pole – the southernmost point on Earth.
 This photo courtesy of: science.dodlive.mil330 × 317

13. Summer solstice – the
first day of summer.
The summer solstice is the longest day
of the year. North and south of the
tropics, it is also the day when the noon
Sun is highest in the sky.
In the northern hemisphere the summer
solstice occurs on or near June 21.
In the southern hemisphere the summer
solstice occurs on or near December 21.
This photo courtesy of: Solarsystem.nasa.gov732x520

14. Winter solstice – the first day of
winter.
 This photo courtesy of: spacescience.arc.nasa.gov860 × 389
The winter solstice is the shortest day
of the year. It is also the day when the
noon Sun is lowest in the sky.
In the northern hemisphere the winter
solstice occurs on or near December 21.
In the southern hemisphere the winter
solstice occurs on or near June 21.

15. That is why do we have seasons.
NCVPS
Kella Randolph M.Ed.