This document discusses the motions of the Earth and their effects. It explains that the Earth rotates on its tilted axis daily, completing a rotation every sidereal day. It also revolves around the sun yearly, with the sun returning to the same position every solar day. These simultaneous motions allow life to exist on Earth by providing a steady flow of solar energy through radiation. As the Earth rotates and revolves, the angle of solar radiation varies, causing the seasons and changes in weather, ecology, and day length.

1. M O T I O N S
O F T H E
E A R T H
C H A P T E R 1 │ L E S S O N 4

2. • The solar system that
we believe today places
the sun at the center
with the terrestrial and
Jovian planets moving
around it. The motions
of the sun and planets
happen simultaneously.
Earth’s motion is
evidenced by the daily
rotation and yearly
revolution

3. Terms needed to be considered:
•Earth’s rotation--
is the amount of
time that it takes
to turn around
once on its axis.

4. Axis
-is an imaginary
line about which a
body rotates.
Earth’s axis is
tilted 23.5 degrees.

5. Sidereal day
•The amount it
takes Earth to
turn on its
axis.

6. Solar day (Mean
Solar Day)
•The amount of
time it takes for
the sun to return
to the same spot.

7. The simultaneous
motions of Earth
make it possible to
support life. As Earth
rotates around the
sun, a flow of energy
is received through
radiation.

8. • Biologically, only
photosynthetic organisms are
capable of harnessing and
converting radiant energy into
chemical energy through the
process of photosynthesis.
This chemical energy is
transferred from one level of
the trophic level to the next.

9. • Physiologically, all organisms
respond to stimulus. Each
organism is equipped with a
unique structure, such as the
human skin, that responds to
sunlight. Melanin is a brown to
black pigment occurring in the
hair, skin, and the iris of the
eyes in animals. When
produced, melanin serves as
protection.

10. • Meteorologically, Earth’s weather
and climate is driven by solar
radiation. Heating of the planet as
a result of rotation affects the
different biogeochemical cycles
such as the hydrologic cycle. The
water vapor in the atmosphere
causes moisture and cloud to form
and precipitation to happen.
Moreover, the varying atmospheric
pressure exerted by air results to
the general circulation that
determines the different
ecosystems of the Earth.

11. • The solar radiation Earth
receives everyday, is not
the same throughout the
year. Since the Earth is
tilted 23.5 degrees on its
axis, the angle by which
light is received on Earth
varies. This results in
changes in weather,
ecology, and daytime called
season.