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Earth, Moon, and the Sun - Revolution of the Earth

Grade 7CBSE

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

🔑Concepts

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Revolution is the motion of the Earth around the Sun in a fixed, elliptical path called an orbit.

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One complete revolution around the Sun takes approximately 36514365 \frac{1}{4} days, which constitutes one solar year.

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The Earth's axis is not vertical; it is tilted at an angle of 23.5∘23.5^\circ from the perpendicular to the orbital plane, or 66.5∘66.5^\circ with the orbital plane itself.

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A Leap Year occurs every four years and has 366366 days. The extra day is formed by adding the 1/41/4 day (approximately 66 hours) saved every year (6×4=246 \times 4 = 24 hours).

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Seasons are caused by the tilt of the Earth's axis and its revolution around the Sun. The four main seasons are Summer, Winter, Spring, and Autumn.

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Summer Solstice occurs on June 21. The Northern Hemisphere is tilted towards the Sun, leading to the longest day and shortest night in this region.

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Winter Solstice occurs on December 22. The Southern Hemisphere is tilted towards the Sun, meaning the Northern Hemisphere experiences its shortest day and longest night.

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Equinoxes occur on March 21 and September 23. On these days, the Sun's rays fall directly on the Equator, and the entire Earth experiences equal days and nights (1212 hours each).

📐Formulae

Time for one Revolution=36514 days\text{Time for one Revolution} = 365 \frac{1}{4} \text{ days}

Angle of Tilt with Orbital Plane=66.5∘\text{Angle of Tilt with Orbital Plane} = 66.5^\circ

Angle of Tilt with Perpendicular Line=90∘−66.5∘=23.5∘\text{Angle of Tilt with Perpendicular Line} = 90^\circ - 66.5^\circ = 23.5^\circ

Leap Year Duration=365 days+1 day=366 days\text{Leap Year Duration} = 365 \text{ days} + 1 \text{ day} = 366 \text{ days}

💡Examples

Problem 1:

If we ignore the 14\frac{1}{4} day for three years and add them all together in the fourth year, calculate the total number of days in that 4-year cycle using vertical addition (365+365+365+366365 + 365 + 365 + 366).

Solution:

365365365+3661461\begin{array}{r} 365 \\ 365 \\ 365 \\ + 366 \\ \hline 1461 \end{array}

Explanation:

We sum three common years of 365365 days and one leap year of 366366 days to find the total number of days in a four-year period.

Problem 2:

Calculate the exact number of hours represented by the 14\frac{1}{4} day fragment in the Earth's revolution period.

Solution:

1 day=24 hours1 \text{ day} = 24 \text{ hours} 14×24=6 hours\frac{1}{4} \times 24 = 6 \text{ hours}

Explanation:

Since one full day is 2424 hours, a quarter of a day is 2424 divided by 44, which equals 66 hours. These 66 hours accumulate over 44 years to create 2424 hours, or 11 full day.

Problem 3:

At what angle is the Earth's axis tilted with respect to its orbital plane?

Solution:

90∘−23.5∘=66.5∘90^\circ - 23.5^\circ = 66.5^\circ

Explanation:

The Earth's axis makes an angle of 23.5∘23.5^\circ with the line perpendicular to the orbit. Therefore, its angle with the orbital plane itself is the complement, which is 66.5∘66.5^\circ.