Class 7 Science Curiosity Chapter 12 MCQ – Earth, Moon and the Sun

Earth rotates from West to East. When viewed from above the North Pole, this rotation appears anticlockwise. Because we observe the sky from this rotating Earth, the Sun appears to move across the sky in the opposite direction.

Earth completes one rotation on its own axis in about twenty-four hours. As it rotates, different places move into and out of sunlight. This produces the familiar cycle of daytime and night-time experienced at most places on Earth.

The axis of rotation is an imaginary line about which Earth spins. It passes through the geographic North Pole and South Pole. A globe uses an axis to help represent this motion and the positions of these two poles.

At any moment, the side of Earth facing the Sun receives sunlight while the other side is dark. Earth’s rotation carries places between these regions. This movement causes day and night without the Sun having to stop producing light.

Earth’s axis of rotation points very close to the Pole Star in the Northern Hemisphere. As Earth rotates, other stars appear to move around this direction. The Pole Star therefore seems nearly fixed in position during the night.

Revolution is the motion of one object around another. Earth revolves around the Sun while also rotating on its own axis. These are different motions: rotation is spinning, whereas revolution involves travelling along a path around another object.

Earth takes about three hundred and sixty-five days and six hours to complete one revolution around the Sun. This is approximately one year. Its path around the Sun is called an orbit and is nearly circular when viewed from above.

As Earth revolves around the Sun, the night side faces different directions in space during different months. We therefore see different stars after sunset over the year. This yearly change is connected with revolution, rather than the daily cycle alone.

Earth’s axis remains tilted as Earth revolves around the Sun. This changes how directly sunlight falls on each hemisphere and how long daylight lasts. Together with Earth’s spherical shape, these differences produce the familiar yearly pattern of seasons.

Around June, the Northern Hemisphere is tilted towards the Sun. Sunlight falls more directly on it and lasts for a longer part of the day. These two effects increase heating and help produce summer in that hemisphere.

Australia is in the Southern Hemisphere, where seasons are opposite to those in the Northern Hemisphere. December is a summer month there. The chapter therefore suggests summer clothes for the Indian cricket team travelling to Australia during December.

The longest daytime in the Northern Hemisphere occurs around twenty-first June, called the summer solstice. After this date, the duration of daylight begins to decrease. The shortest daytime occurs around the winter solstice in December, as described in the chapter.

Around the equinox dates in March and September, daytime and night-time are each about twelve hours long. The chapter calls these the spring and autumn equinoxes in the Northern Hemisphere. Equinoxes differ from the longest and shortest days of solstices.

A solar eclipse occurs when the Moon comes between the Sun and Earth and blocks sunlight from reaching some places on Earth. The alignment matters because the Moon’s shadow must fall on Earth for people there to observe the eclipse.

Apparent size depends on both an object’s actual size and its distance from the observer. The Moon is much smaller than the Sun but also much closer to Earth. Their similar apparent sizes allow the Moon to cover the Sun.

In a partial solar eclipse, the Moon blocks only part of the Sun’s visible disc for the observer. In a total solar eclipse, it covers the entire disc. What people see depends on their position relative to the Moon’s shadow.

A lunar eclipse happens when Earth comes between the Sun and Moon and blocks sunlight from reaching the Moon. Earth’s shadow then falls on the Moon. This arrangement differs from a solar eclipse, where the Moon lies between Earth and Sun.

During a total lunar eclipse, the Moon is completely within Earth’s shadow. The chapter describes its bright disc becoming dark red and remaining so until it moves out of the shadow. A partial eclipse affects only part of the Moon.

Looking directly at the Sun with unprotected eyes can damage vision even during a solar eclipse. The chapter recommends organised viewing with specialised protection or safe projection methods. Ordinary sunglasses do not provide the protection needed for direct solar viewing.

Leon Foucault used a long pendulum to give a simple demonstration of Earth’s rotation. The chapter describes a heavy bob suspended from a high ceiling. Such a pendulum helps connect an observation on Earth with Earth’s motion in space.

In the model, the torch represents the Sun and the sticker marks a place on Earth. Moving from darkness into the illuminated half represents sunrise at that place. Continuing the rotation later carries it out of sunlight, representing sunset.

Rotation is Earth spinning about its axis and takes about twenty-four hours. Revolution is Earth moving around the Sun and takes about one year. Keeping the motions separate helps explain why a daily cycle and a yearly cycle have different causes.

The tree appears to move because the child’s position is changing on the merry-go-round. Similarly, Earth’s rotation makes the Sun and stars appear to move across the sky. Observed motion must therefore be considered along with the observer’s own motion.

Earth’s rotation causes the stars’ apparent movement across the sky during a single night. Earth’s revolution changes the direction in which the night side faces over the year. The two observations therefore connect with different motions of Earth.

The chapter states that Earth is closest to the Sun in January. This shows why a simple closer-in-June explanation is incorrect. Seasons mainly result from the tilted axis, which changes the intensity and duration of sunlight received by each hemisphere.

When the same amount of sunlight falls on a smaller area, it provides more heating to that area. When spread over a larger area, it is less intense. The chapter uses this difference to help explain seasonal heating of the hemispheres.

Apparent size depends on distance as well as actual size. Venus is larger than the Moon but much farther from Earth. It therefore appears too small to cover the Sun completely, showing why physical size alone does not decide what is seen.

Earth rotates while the Moon continues moving in its orbit. These motions make the Moon’s shadow travel across Earth’s surface. A particular place remains in the region of total eclipse only briefly, so complete covering lasts just a few minutes.

The Moon completely covers the Sun for observers in a small region, while observers in nearby regions may see only part covered. Different locations can therefore experience different views of the same eclipse without either report being incorrect.

Earth continues rotating, but its tilted North Pole remains directed towards the Sun during this part of the year. Rotation does not carry the pole into darkness then. Continuous polar daylight therefore does not mean that Earth’s daily rotation has stopped.