NCERT Solutions for Class 7 science Chapter 12: Earth Moon and the Sun Class 7

How day and night occur on the Earth due to its rotation? (Page 172)
Answer:
Day and night occur because the Earth rotates on its axis from west to east. As it rotates, the side facing the Sun experiences day, and the side away from the Sun experiences night.

Since the Earth is rotating, shouldn’t the stars also appears to move in the sky like the Sun? (Page 1 74)
Answer:
Yes, since the Earth rotates from west to east, the stars appear to move across the sky from east to west, just like the Sun. This movement is only apparent it happens because the Earth is spinning on its axis.

Why do different stars appear in the night sky over the course of a year? (Page 175)
Answer:
We see different stars at night during the year because the Earth moves around the Sun. As it moves, the part of the sky we can see at night also changes, so new stars and constellations become visible in different months.

We go through a cycle of seasons every year. Is it related to the revolution of the Earth around the Sun in some way? (Page 1 77)
Answer:
Yes, the cycle of seasons is related to the Earth’s revolution around the Sun. As the Earth revolves around the Sun, its tilted axis causes different parts of the Earth to receive different amounts of sunlight at different times of the year. This change in sunlight causes the seasons.

Why days are longer in summer than in winter? (Page 177)
Answer:
Days are longer in summer than in winter because the Earth’s axis is tilted. During summer, your part of the Earth is tilted towards the Sun, so it gets more sunlight for a longer time each day.

Could the light from the Sun get blocked by the two planets which are revolving between the Earth and the Sun? (Page 1 79)
Answer:
No, the light from the Sun does not usually get blocked by the two planets (Mercury and Venus) because they are very small compared to the Sun and are far away from the Earth. Sometimes they do come between the Earth and the Sun, but they block only a small part of the sunlight and it’s hardly noticeable from Earth.

In Fig. 12.17, how many hours of sunlight do the North Pole and the South Pole receive during one rotation of the Earth?

Answer:
In the given figure, the North Pole is in darkness, which means it is winter in the Northern Hemisphere. During this time, the North Pole receives 0 hours of sunlight, while the South Pole, experiencing summer, receives 24 hours of sunlight during one rotation of the Earth. This occurs due to the tilt of the Earth’s axis.

Fill in the blanks
(i) Stars rise in the ______ and set in the _______.
Answer:
east, west

State whether True or False
(i) Lunar eclipse occurs when the Sun comes between the Earth and the Moon.
Answer:
False

Padmashree saw the Orion constellation nearly overhead at 8 pm yesterday. When will she see Orion overhead today?
Answer:
Padmashree will see the Orion constellation overhead about 4 minutes earlier each day due to Earth’s revolution. If she saw it at 8:00 pm yesterday, she will see it at 7:56 pm today.

Nandhini saw a group of stars rising at midnight on 21 June. When will she see the same group of stars rising at midnight next
year?
Answer:
Stars rise about 4 minutes earlier each day because of Earth’s orbit around the Sun. Over a year, this adds up to a 24-hour shift. This means Nandhini will see the same stars rising at midnight on 20 June next year, as they rise one day earlier on the calendar each year.

Abhay noticed that when it was daytime in India, his uncle who was in the USA was generally sleeping as it was night-time there. What is the reason behind this difference?
Answer:
The Earth rotates, which creates different time zones around the world. India is ahead of the USA in time. So when it’s daytime in India, it is night-time in the USA, and Abhay’s uncle is asleep.

Four friends used the following ways to see the solar eclipse. Who among them was being careless?
(i) Ravikiran used a solar eclipse goggle.
(ii) Jyothi used a mirror to project the Sun’s image.
(iii) Adithya saw the Sun directly with his eyes.
(iv) Aruna attended a programme arranged by a planetarium.
Answer:
(iii) Adithya was being careless because he looked at the Sun directly with his eyes, which can damage eyesight. The safe ways to view a solar eclipse are using solar eclipse glasses, indirect viewing methods, or attending guided programmes.

Fill in the circles in Fig. 12.18 appropriately with one of the following: Sun, Moon, Earth.

Answer:

The Moon is much smaller than the Sun, yet it can block the Sun completely from our view during a total solar eclipse. Why is it possible?
Answer:
The Moon and the Sun look almost the same size from Earth, even though the Moon is much smaller. This happens because the Moon is much closer to Earth than the Sun. Since the Moon appears nearly the same size as the Sun in the sky, it can completely cover the Sun during a total solar eclipse.

The Indian cricket team matches in Australia are often held in December. Should they pack winter or summer clothes for their trip?
Answer:
They should pack summer clothes for their trip. In Australia, December falls in summer because it is in the Southern Hemisphere, where the seasons are opposite to those in India. So while it’s winter in India in December, it is summer in Australia.

Why do you think lunar eclipses can be seen from a large part of the Earth when they happen, but total solar eclipse can be seen by only a small part of the Earth?
Answer:
A lunar eclipse can be seen from a large part of the Earth because the Earth’s shadow is big, and it covers the Moon for a longer time. Everyone on the night side of the Earth can see it. But a total solar eclipse is visible only for a few minutes and from a small area, because the Moon’s shadow is small and moves quickly across the Earth due to the Moon’s motion and Earth’s rotation.

If the Earth’s axis were not tilted with respect to the axis of revolution, explain what would be the effect on seasons?
Answer:
If the Earth’s axis were not tilted, there would be no seasons. Every place on Earth would get the same amount of sunlight throughout the year. As a result, the weather would stay almost the same all year round  no summer, winter, spring, or autumn. The length of days and nights would also stay nearly equal every day.