Page 162 - Science Course 3 (Book 2)

Mo12-L1a: What Causes Seasons on Earth?

The side of Earth facing the Sun is in daylight. Key Concept
The side of Earth away from the Sun is in darkness.
What Causes Seasons on Earth?
Earth makes one full rotation every 24 hours.
What causes seasons?

SUMMARY

What Causes Seasons on Earth?

Earth’s tilt does not change as Earth orbits the
Sun.
Earth’s Tilt and Seasons

Seasons occur because Earth’s tilt does not change as Earth orbits the Sun.

The North Pole and the
South Pole always point in
the same directions.

However, the portion of
Earth tilted toward the Sun
does change.

An equinox occurs when
Earth’s rotation axis is tilted
neither toward nor away
from the Sun.

An equinox occurs twice
each year. These two days
signify the beginning of
spring and fall.

When the Earth’s rotation
axis is tilted directly toward
or away from the Sun a
solstice occurs.
When the North Pole is toward the Sun, it is summer
in the northern hemisphere.

When the South Pole is toward the Sun, it is winter in
the northern hemisphere.

The hemisphere tilted more toward the Sun receives
more direct sunlight, for more hours during the day.

154