Important Questions Test: Motions Of The Earth - UPSC MCQ

Every year, 365 days pass, but due to the Earth's orbit, there are actually about 365.25 days in a year. To make up for the extra 0.25 days, an extra day (24 hours) is added every four years. This extra day is added to the month of February, making it 29 days instead of the usual 28. A year with 366 days is called a leap year.

There are 2 solstices each year:

• Summer Solstice: Occurs around June 21st in the Northern Hemisphere. It marks the longest day of the year with the most daylight hours.
• Winter Solstice: Occurs around December 21st in the Northern Hemisphere. It marks the shortest day of the year with the least daylight hours.
  Solstices occur due to the Earth's axial tilt, causing varying daylight hours as the Earth orbits the Sun.

Old NCERT

Revolution is the term used to describe the path (or orbit) of Earth through space. Earth's revolution around the sun is responsible for seasonal change and leap years. This path is shaped like an ellipse and has points when Earth is closer to the sun and farther from it.

•  The sun rays are vertical over the Tropic of Capricorn during the winter solstice.
• The winter solstice occurs around December 21st in the Northern Hemisphere.
•  During this time, the Southern Hemisphere experiences its longest day.
• The Tropic of Capricorn is located at 23.5 degrees south latitude.

sun provides heat so the area near the sun gets summer ant area away gets winter so, when the part of the earth where it was winter faces the sun ( revolving of earth) it is summer in that region and it is winter on the other region

• The axis of the Earth is an imaginary line.
• It runs from the North Pole to the South Pole.
• This line is crucial for understanding Earth's rotation.
• Earth rotates around this axis, which is tilted at an angle of approximately 23.5 degrees.
• This tilt is responsible for the changing seasons as the Earth orbits the Sun.
• The concept of an imaginary axis helps explain phenomena like day and night and the variation in sunlight received at different latitudes.

Winter, Autumn and Spring are names of seasons whereas, Axis is an imaginary line which runs through the poles on which the Earth rotates. 

Old NCERT

Rotation and Revolution are two motions of the earth. When earth spins or rotates around its axis, that movement of spinning is called Rotation of Earth. And when earth spins or revolves around the sun, that movement is called Revolution of Earth.

The rotation of the earth on its own axis and the revolution of earth around the sun cause changes in season and day and night. The change in seasons is caused by the rotational tilt of the earth on its axis when it revolves around the sun.

The earth has an axial tilt of 23.5 degrees which means that its rotation axis is inclined to its orbital axis at an angle of 23.5 degrees. This causes one pole of the earth to be directed more towards the Sun on one side of the orbit, and the other pole on the other side. This is the reason for occurrence of 'seasons' on earth'.

As the earth spins on its axis, producing night and day, it also moves about the sun in an elliptical (elongated circle) orbit that requires about 365 1/4 days to complete. The earth's spin axis is tilted with respect to its orbital plane. This is what causes the seasons.

The Circle of Illumination divides the Earth into the part that is in daylight and the part that is in darkness. It separates day from night.

The axis of the earth which is an imaginary line, makes an angle of  66^1/2° with its orbital plane. The plane formed by the orbit is known as the orbital plane. Theearth receives light from the sun.

The portion facing the sun experiences day while the other half away from the sun experiences night. The circle that divides the day from night on the globe is called the circle of illumination. The earth takes about 24 hours to complete one rotation around its axis.

This spinning movement is called Earth's rotation. At the same time that the Earth spins on its axis, it also orbits, or revolves around the Sun. This movement is called revolution.

In the winter, Earth tilts away from the Sun. In North America, around June 21, Earth tilts on its axis toward the Sun. This is called the summer solstice, and it is when the Northern Hemisphere has the most daylight of any time of the year.

The Poles basically experience about six months of day and six months of the night because of the tilt of the Earth on its axis. At the point when the North Pole is tilted towards the Sun, it experiences continuous daylight for six months.

The correct answer is B: Rotation.

• Rotation refers to the spinning of Earth on its axis.
• This rotational movement takes approximately 24 hours to complete one full turn.

The sun is exactly over the Tropic of Cancer. on 21st June summer solstice occurs in the northern hemisphere. It gets more heat and light and that time there is winter solstice in the Southern Hemisphere as it is away from the sun.

Earth's orbit is not a perfect circle. It is elliptical, or slightly oval-shaped. This means there is one point in the orbit where Earth is closest to the Sun, and another where Earth is farthest from the Sun.

Old NCERT

 In Australia, Christmas is celebrated in the summer season. This is because of the tilt of the earth. Australia is situated in the southern hemisphere and during the month of December, there will be the summer season in the southern hemisphere and the winter season in the northern hemisphere.

• The winter solstice falls on 22nd December during which there is continuous daylight on the South pole and continuous darkness at the North pole. Hence option A is correct.
• During summer solstice i.e. 21st June, there is continuous daylight at the North pole.
• Equinox refers to an equal period of darkness and daylight.