Comprehensive Study G8uide for Grade 5 Science: Earth's Rotation, Revolution, and Patterns over Time

Grade 5 Science Final Exam Materials: Competency 3.2

• ‘ This material covers Competency 3.2 for the Grade 5 Science Final Exam: Discuss using mathematical modeling the patterns of daily changes in length and direction of shadows, day and night, and the season appearance of some stars in the sky.

• The primary focus is on Earth’s movement, the solar system, and how these movements affect life on Earth.

Earth in the Solar System

• We reside on planet Earth, which is one of eight planets in our solar system.

• Keywords for Study:

  • Solar system

  • Sun

  • Planet

  • Orbit

  • Earth

  • Moon

  • Rotation

  • Revolution

  • Axis

  • Shadow

  • Constellation

Earth's Movement: Rotation vs. Revolution

Earth moves in two distinct ways in space: rotation and revolution. The primary differences between these movements are summarized below:

• Rotation:

  • Definition: Rotation is a complete spin on the axis.

  • Mechanism: Earth spins on its imaginary axis.

  • Duration: It takes approximately $24\,\text{hours}$ to complete one rotation.

  • Primary Effect: Earth's rotation causes day and night.

• Revolution:

  • Definition: Revolution is a complete pass around the Sun.

  • Mechanism: Earth moves in a path called an orbit around the Sun.

  • Duration: It takes approximately $365.25\,\text{days}$ (or one year) to complete one revolution.

  • Orbit: An orbit is defined as the path that a revolving object follows.

The Earth's Axis and Tilt

• Definition of Axis: The axis is an imaginary line through the center of the Earth. It extends from the North Pole to the South Pole.

• Degree of Tilt: The axis is tilted at an angle of $23.5^{\circ}$.

Implications of the Axial Tilt (Critical Thinking)

If the Earth’s axis were not tilted at $23.5^{\circ}$, the following conditions would occur:

• Earth would have no seasons.

• All places on Earth would receive nearly the same amount of sunlight all year long.

• Days and nights would remain nearly the same length every single day. Ll

Day and Night Cycles

• Rotation is the direct cause of the day and night cycle.

• As the Earth rotates on its axis, different sides of the planet are exposed to the Sun.

• Daytime: The side of the Earth facing toward the Sun experiences day.

• Nighttime: The side of the Earth facing away from the Sun experiences night.

Earth's Revolution and the Seasons

Earth's revolution around the Sun, combined with its tilted axis, results in the changing of seasons. The amount of direct sunlight a hemisphere receives determines its season.

Seasonal Mechanics by Hemisphere

• Summer in the Southern Hemisphere:

  • Caused by more direct sunlight shining onto the Southern Hemisphere (e.g., Australia).

  • While it is summer in the Southern Hemisphere, it is winter in the Northern Hemisphere (e.g., Japan).

• Winter in the Southern Hemisphere:

  • Occurs when there is less direct sunlight on the Southern Hemisphere.

  • During this time, the Northern Hemisphere receives more direct sunlight and experiences summer.

Transitional Seasons

• Autumn (Fall):

  • Occurs after summer.

  • Characterized by weather starting to cool down.

  • Deciduous leaves may fall from trees.

• Spring:

  • Occurs before summer.

  • Characterized by weather becoming warmer.

  • Plants begin their growth cycle.

Patterns of Light and Shadows

• Definition of a Shadow: A shadow is a dark area or shape that is made when an object blocks a source of light.

• Requirement for Shadows: You must have a source of light to create a shadow. The Sun is a natural source of light for Earth.

Daily Shadow Patterns

Shadows change their size and position throughout the day because the Sun appears to move across the sky from East to West due to Earth's rotation. Sunlight strikes objects at different angles:

• Morning ($6:00\,\text{AM}$): The Sun rises in the East. Shadows are long.

• Noon ($12:00\,\text{PM}$): The Sun is at its highest point in the sky. Shadows are at their shortest.

• Afternoon ($6:00\,\text{PM}$): The Sun is in the West. Shadows are long again.

Seasonal Shadow Patterns

• Winter Season: The Sun appears very low in the sky, causing shadows to be at their longest.

• Summer Season: The Sun appears very high in the sky, causing shadows to be at their shortest.

Stars and Constellations

• Star Brightness:

  • Some stars in a constellation appear brighter than others.

  • The apparent brightness of a star as seen from Earth is related to its distance. Stars that are closer to Earth generally appear brighter.

  • The Sun: The Sun is a star that is much closer to Earth than any other star. Consequently, the Sun appears much brighter than all other stars.

• Movement of Stars:

  • Constellations appear to move across the sky over time. This apparent movement is caused by the Earth’s rotation.

• Hemispheric Perspective:

  • The appearance of the night sky looks different depending on whether it is viewed from the Northern Hemisphere or the Southern Hemisphere.