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Earth and Space - Earth’s Rotation and Revolution

Grade 6IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Earth's Rotation: The Earth spins on its imaginary axis from West to East. This rotation takes approximately 23.9323.93 hours (rounded to 2424 hours) and is responsible for the cycle of day and night.

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Earth's Axis: The Earth is tilted on its axis at an angle of 23.5∘23.5^\circ relative to its orbital plane. This tilt remains constant as the Earth orbits the Sun.

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Earth's Revolution: The movement of the Earth around the Sun in an elliptical orbit. One complete revolution takes 365.25365.25 days, which defines one solar year.

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The Seasons: Seasons are caused by the 23.5∘23.5^\circ tilt of the Earth's axis and its revolution around the Sun. When a hemisphere is tilted toward the Sun, it experiences summer; when tilted away, it experiences winter.

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Solstices and Equinoxes: A solstice occurs when the Sun reaches its highest or lowest point in the sky at noon (Summer Solstice and Winter Solstice). An equinox occurs when day and night are of approximately equal length (1212 hours each).

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Leap Year: Because a revolution takes 365.25365.25 days, the extra 0.250.25 day is accumulated over four years to add an extra day (FebruaryFebruary 2929) to the calendar, maintaining seasonal alignment.

📐Formulae

Rotation Rate=360∘24 hours=15∘/hour\text{Rotation Rate} = \frac{360^\circ}{24 \text{ hours}} = 15^\circ/\text{hour}

1 Tropical Year≈365.25 days1 \text{ Tropical Year} \approx 365.25 \text{ days}

Axial Tilt≈23.5∘\text{Axial Tilt} \approx 23.5^\circ

vorbital=2πrTv_{orbital} = \frac{2\pi r}{T}

💡Examples

Problem 1:

Calculate how many degrees the Earth rotates in 44 hours.

Solution:

15∘/hour×4 hours=60∘15^\circ/\text{hour} \times 4 \text{ hours} = 60^\circ

Explanation:

Since the Earth completes a 360∘360^\circ rotation in 2424 hours, it rotates 15∘15^\circ every hour. Multiplying the hourly rate by 44 gives the total rotation.

Problem 2:

If it is the Summer Solstice in the Northern Hemisphere, which way is the North Pole tilting relative to the Sun?

Solution:

The North Pole is tilted at 23.5∘23.5^\circ toward the Sun.

Explanation:

During the Summer Solstice in the Northern Hemisphere, the axial tilt causes the North Pole to lean towards the Sun, resulting in the longest day of the year for that hemisphere.

Problem 3:

Why do we have a leap year every 44 years?

Solution:

0.25 day×4=1 full day0.25 \text{ day} \times 4 = 1 \text{ full day}

Explanation:

The Earth's actual orbital period is 365.25365.25 days. To keep our 365365-day calendar synchronized with the solar year, we add one day every four years.