Earth, Moon and the Sun | CBSE Class 7 Science Notes

These notes cover the Earth’s rotation and revolution, day and night, the apparent movement of the Sun and stars, the changing night sky, seasons, solstices and equinoxes, apparent size, solar and lunar eclipses, safe eclipse viewing, and observations used to understand these events.

What is the Earth’s rotation?

Definition: Rotation is the motion of an object whose parts move in circles around an imaginary line passing through it. This line is its axis of rotation.

A spinning top, a spinning fan and a spinning ball help us picture rotation. The Earth also spins on its own axis in space. Its axis passes through the geographic North Pole and South Pole, the two poles shown at opposite ends of that axis.

The Equator divides the Earth into two halves. The half towards the North Pole is the Northern Hemisphere; the half towards the South Pole is the Southern Hemisphere. A hemisphere means half of the Earth. These names help us describe rotation and seasonal differences.

In which direction does the Earth turn?

The Earth rotates from West to East. Viewed from above the North Pole, this motion is anti-clockwise, opposite to the direction in which the hands of a clock move. The viewing position matters when describing a turn as clockwise or anti-clockwise.

The Earth completes one rotation in about 24 hours. A globe, a model of the Earth, helps us follow a particular place during this motion. Put a small sticker at a location and rotate the globe while looking down from above its North Pole.

As the globe completes one rotation, the sticker travels around and returns to its starting position. This represents a location moving with the rotating Earth. The globe need not travel around another object to demonstrate this particular motion.

The drawing labels the Earth’s axis, North Pole, South Pole, Equator, Northern Hemisphere, Southern Hemisphere, West and East. An arrow indicates the rotation. The labels NP and SP mean North Pole and South Pole, respectively.

See Fig. 12.3 in your NCERT textbook

Keep the direction and the time together: the Earth spins from West to East and takes about 24 hours for one turn. Its separate movement around the Sun is called revolution, meaning motion around another object.

How does rotation cause day and night?

Daytime occurs on the side of the Earth facing the Sun. The side facing away is dark and experiences night. As the Earth turns, a location moves into sunlight and later into darkness, producing the day-night cycle.

Sunrise occurs when a location moves into light; sunset occurs when it moves into darkness. The Sun’s daily journey across the sky is an apparent motion, a movement that we see because our viewing position on the Earth is moving.

How can a globe and torch show this?

1. Use a globe to represent the Earth and mark a location with a small sticker.
2. Take it into a relatively dark room and use a torch to represent the Sun.
3. Shine the torch from some distance, say 1.5 metres, towards the globe. One half receives light while the other half stays dark.
4. Rotate the globe from West to East and watch the marked location enter the light and then pass into darkness.

The lit half represents day and the dark half represents night. Following the sticker explains the changes experienced at one place. Looking at both halves together explains how different places can experience day and night at the same time.

A torch on the left shines on a globe standing on a table. The half facing the torch is illuminated, while the opposite half is shaded.

See Fig. 12.4(b) in your NCERT textbook

In India, sunrise first occurs in the eastern part and then in other parts. In the model, the eastern part enters the torchlight first when the globe turns from West to East. Reversing the globe’s motion would not reproduce this observed order.

The same explanation accounts for it being daytime in India while someone in the USA is generally asleep at night. The two places can lie on different sides relative to sunlight. Rotation, rather than the Earth’s journey around the Sun, explains this daily cycle.

Why do the Sun, Moon and stars appear to move?

A moving observer can see stationary surroundings appear to move. On a merry-go-round turning anti-clockwise, nearby objects appear to move clockwise. A tree can enter the rider’s view from the left and leave it on the right even though the tree remains in place.

This helps explain apparent motion in the sky. We observe from the rotating Earth. Because it rotates from West to East, the Sun appears to rise in the eastward direction, cross the sky and set in the westward direction.

The Moon also appears to rise eastwards and set westwards because of this rotation. The stars show apparent movement too. The daily movement seen in the sky must therefore be understood together with the movement of the observer on the Earth.

Why does the Pole Star appear nearly stationary?

The Earth’s axis points very close to the Pole Star in the Northern Hemisphere. The Pole Star, also called Dhruva Tara, therefore appears nearly stationary. The stars appear to move around it. “Nearly stationary” is more accurate here than saying it is exactly motionless.

The Big Dipper, also called Saptarishi, is a recognisable pattern of stars that can be used for observations. On an early evening between March and May, identify it and the Pole Star if visible. Record the date, place and time.

Sketch the Big Dipper’s position relative to the Pole Star. Observe again after two hours and repeat after another two hours on the same night. If the Pole Star cannot be seen, use a fixed tree or building in the relevant direction as a reference.

Star trails are arcs recorded when a camera’s shutter stays open for a long time. Such long-exposure photographs record the stars’ apparent motion. They connect a pattern visible in a photograph with the Earth’s rotation during the exposure.

How does revolution change the view of the night sky?

Revolution is an object’s movement around another object. The Earth revolves around the Sun while also rotating on its own axis. These motions happen together, but describe different movements and help explain different observations.

An orbit is the path followed by an object revolving around another object. Viewed from above, the Earth’s orbit around the Sun is nearly circular. A side view can make that path appear elongated, so the shape of a drawing depends on the viewing direction.

The Earth completes one revolution in about 365 days and 6 hours, or nearly one year. The word “about” matters: the time should not be presented as an exact whole number of days.

How do rotation and revolution differ?

After sunset, the night sky becomes visible because the Earth has rotated. As the Earth also travels around the Sun, we look in different directions into the night sky at different times of the year. The stars seen after sunset therefore gradually change.

To observe this yearly change, compare a recognisable star pattern at a fixed time of night on dates separated by a month. Keeping the observation time fixed helps distinguish this comparison from watching apparent movement over a single evening.

The Bhil and Pawara communities of the Tapi Valley in western India used the appearance of particular star patterns as signs of the arrival of monsoon rain. This is an example of connecting recurring observations of the sky with a seasonal event.

Why do seasons occur on the Earth?

The Earth’s axis is tilted, rather than upright with respect to its orbit. The Earth maintains this tilt while travelling around the Sun. Its tilted axis and spherical, or ball-like, shape explain the cycle of seasons as its position in the orbit changes.

In June, the Northern Hemisphere is tilted towards the Sun and the Southern Hemisphere is tilted away. A given amount of sunlight spreads over a smaller area in the Northern Hemisphere than in the Southern Hemisphere, so that area is heated more.

How do sunlight intensity and daytime work together?

Sunlight intensity describes how concentrated the sunlight is over an area. The same amount of sunlight is more intense when spread over a smaller area and less intense when spread over a larger area. The Earth’s spherical surface helps produce this difference.

The Northern Hemisphere also receives sunlight for more than 12 hours in June. More intense sunlight, lasting for a longer time, produces summer there. Both the concentration of sunlight and the duration of daytime belong in the explanation.

In December, the Northern Hemisphere experiences the opposite situation: sunlight is less intense and lasts for a shorter time. It experiences winter. The seasons and daytime lengths are reversed in the Southern Hemisphere, which has winter in June and summer in December.

The drawing places the Earth at positions labelled March, June, September and December around the Sun. June is labelled summer in the Northern Hemisphere and December winter. The orbit is shown from the side; sizes and distances are not to scale.

See Fig. 12.9 in your NCERT textbook

Two Earth drawings compare June and December. The labels contrast the same amount of sunrays spread over a smaller area with that spread over a larger area. The Northern Hemisphere receives more intense sunlight in June; the situation reverses in December.

See Fig. 12.10 in your NCERT textbook

Note: Seasons are not explained by a hemisphere becoming slightly closer to the Sun or by the Earth’s changing distance along its orbit. Those distance differences are very small. The Earth is closest to the Sun in January.

What are solstices, equinoxes and regional seasonal differences?

A solstice marks the longest or shortest daytime of the year in a hemisphere. In the Northern Hemisphere, the summer solstice occurs around 21 June, when daytime is longest. After it, daytime becomes shorter and night becomes longer.

The winter solstice occurs around 22 December in the Northern Hemisphere. It brings the shortest daytime and longest night there. These dates are given as “around” the stated dates, rather than as unchanging exact dates for every year.

An equinox is an occasion when daytime lasts for 12 hours. Around 21 March and 23 September, the Northern Hemisphere has its spring and autumn equinoxes, respectively. Spring and autumn name the seasons associated with these equinoxes.

How do the two hemispheres compare?

The contrast is especially clear at the North Pole. In June, it receives sunlight for all 24 hours of a rotation. In December, it remains in darkness for all 24 hours. The South Pole experiences the opposite behaviour.

At the Equator, there are always 12 hours of sunlight and 12 hours of darkness. There is little difference in the intensity of sunlight there in different months. The seasonal effect is therefore not very prominent in southern Indian states close to the Equator.

Local geographical features and closeness to oceans or seas can also influence these broad seasonal patterns. These differences in sunlight do not provide every detail of conditions at a particular place. The local setting also matters when describing the seasons experienced there.

How can the smaller Moon appear to cover the Sun?

The Moon is the Earth’s natural satellite, a natural object that revolves around the Earth. Although it is much smaller than the Sun, it is also much closer to us. Its visible size in the sky cannot be judged from its physical size alone.

Definition: Apparent size is the size an object seems to have when viewed by the eye. It depends on both the object’s actual physical size and its distance from the observer.

What does the thumb activity demonstrate?

1. Ask a friend to stand about 5 metres in front of you.
2. Close one eye and stretch your hand towards your friend with your thumb pointing upwards.
3. Try covering your friend’s head from your view with the thumb.
4. Compare the objects’ actual sizes with the sizes they appear to have from your position.

The thumb is much smaller than the friend’s head, but is much closer to the eye. Their apparent sizes can therefore be similar. This is an observation about size and distance; it does not mean their actual physical sizes become equal.

The Sun and Moon likewise have similar apparent sizes when viewed from the Earth. Because the Moon is much closer, it can appear to cover the entire Sun. This explains how it can block our view of the Sun despite being physically smaller.

Mercury and Venus are planets revolving between the Earth and Sun. They are much larger than the Moon but much farther from the Earth. Their apparent sizes are very much smaller than the Sun’s, so they never block all its light reaching us.

A Transit of Venus occurs when Venus passes between the Sun and Earth and appears as a tiny black dot against the Sun’s bright face. It is a rare event. Its appearance provides another example of the importance of distance when comparing apparent sizes.

What happens during a solar eclipse?

A solar eclipse occurs when the Moon comes between the Sun and Earth in a position that blocks sunlight from reaching us. The relevant order is Sun, Moon, Earth. The Moon’s shadow falls on a small area of the Earth’s surface.

Observers in the area where the Moon covers the whole Sun see a total solar eclipse. Observers where the Moon covers some regions of the Sun see a partial solar eclipse. The visible event depends on the observer’s position relative to the Moon’s shadow.

The Sun is on the left, the Moon is between it and the Earth, and the shadow reaches the Earth on the right. Labels identify total and partial solar eclipse regions and the two orbits. Sizes and distances are not to scale.

See Fig. 12.13 in your NCERT textbook

Why does total darkness last only briefly?

During a total solar eclipse, it becomes dark for a few minutes in the affected area during daytime. The Earth continues rotating and the Moon continues moving in its orbit. These movements carry the Moon’s shadow across the Earth’s surface.

A total solar eclipse is therefore visible from an affected location for only a few minutes. As the Moon moves away from in front of the Sun, a partial solar eclipse is seen and daylight begins to return.

The darkness does not cover the entire Earth. The Moon’s shadow reaches a small area, so the description must refer to the places experiencing the eclipse. Elsewhere, observers may see a partial eclipse or may not be in the affected area.

The basic explanation brings together three ideas: sunlight travels towards the Earth, the Moon can obstruct it, and the observer’s location determines how much of the Sun appears covered. The Sun and Moon do not need to be equal in actual size for this to happen.

How can a solar eclipse be observed safely?

The Sun remains intense enough during a solar eclipse to damage the eyes and cause blindness. An eclipse must not be viewed directly. The apparent reduction in brightness does not make direct viewing safe, and ordinary sunglasses do not provide an acceptable way to observe it.

Note: Do not view a solar eclipse directly or through sunglasses, binoculars or telescopes. Attend organised solar-viewing activities that provide specialised eye protection and scientific guidance.

Planetaria and astronomy clubs usually hold eclipse-viewing events. These are useful places to observe because the organisers provide specialised eye protection for solar viewing and explain the event scientifically. Following the viewing arrangements is part of observing safely.

How does supervised projection work?

Projection means forming the Sun’s image on a wall or screen so that the image can be observed there. A small mirror can do this. Holding its angle throughout an eclipse can be difficult, so a movable support can help.

The support can use a hollow ball with a small hole, half-filled with sand for stability. A small mirror is attached to the ball, which rests on a circular ring. Turning the ball adjusts the mirror until the Sun’s image appears on the screen.

This activity must be set up and carried out strictly under a teacher’s supervision. The reflected beam must not be directed into anyone’s eyes. Looking at the screen image is the purpose of the arrangement; the beam itself is not a viewing target.

Why should eclipses be understood scientifically?

People recorded eclipses long before their causes were understood. Fear encouraged superstitions about eating, cooking or going outside during an eclipse. Knowing how an eclipse happens removes the need for such fears while leaving the eye-safety precautions fully necessary.

Scientists travel to places where eclipses can be observed because these events allow them to study phenomena that cannot otherwise be seen. An eclipse is called grahan in Sanskrit and many Indian languages. Ancient astronomical texts, including the Surya Siddhanta, contain calculations for predicting eclipses.

What happens during a lunar eclipse?

A lunar eclipse occurs when the Earth blocks sunlight from reaching the Moon. The order is Sun, Earth, Moon. The Earth’s shadow falls on the Moon’s full disc, meaning the circular face of the Moon seen from the Earth.

When the Moon is completely in the Earth’s shadow, the event is a total lunar eclipse. The bright disc begins to look dark red. It remains so until the Moon moves out of the Earth’s shadow.

A partial lunar eclipse occurs when part of the Moon is within the Earth’s shadow and the remaining part is visible. The distinction between total and partial refers to how much of the Moon lies in the shadow.

The Sun is on the left and the Earth is between it and the Moon’s positions on the right. The drawing labels total and partial lunar eclipse positions, the Moon’s orbit and the Earth’s orbit. Sizes and distances are not to scale.

See Fig. 12.16 in your NCERT textbook

How do solar and lunar eclipses differ?

Naked-eye viewing means looking without an optical instrument. The eclipsed full Moon can safely be observed this way. Do not transfer this permission to solar eclipses: direct viewing of the eclipsed Sun must still be avoided.

To explain either eclipse, identify the object blocking sunlight and then identify where its shadow falls. This keeps the arrangements clear. During a solar eclipse the Moon blocks sunlight reaching the Earth; during a lunar eclipse the Earth blocks sunlight reaching the Moon.

How have observers and scientists investigated these movements?

Understanding the sky combines repeated observation, models and instruments. A globe and torch explain light and darkness; observations of star patterns reveal changes during a night and over a year. Historical observers also developed explanations for the movements they saw.

What explanations did Aryabhata and Foucault provide?

Aryabhata, the ancient Indian mathematician and astronomer, wrote the Aryabhatiya around the fifth century CE, meaning Common Era. He explained the apparent westward movement of stars through a comparison with a person in a moving boat who sees stationary objects appear to move backwards.

Aryabhata’s stated time for one Earth rotation is around 23 hours 56 minutes 4.1 seconds in modern units. This is close to the currently accepted value. Keep the qualifier “around” when reporting this historical value.

In the middle of the nineteenth century, Leon Foucault used a long pendulum to give the first simple demonstration of the Earth’s rotation. A Foucault pendulum consists of a long string and a heavy bob, the suspended weight, hanging from a high ceiling.

A Foucault pendulum 22 metres long hangs in the Constitution Hall of the new Parliament building in New Delhi. It is an example of an instrument associated with demonstrating the Earth’s rotation, rather than just representing it with a model.

What contributions have Indian observatories made?

The Kodaikanal Solar Observatory in the Palani hills of southern India was established in 1899. It has supplied solar data for over 100 years and is operated by the Indian Institute of Astrophysics, Bengaluru. An observatory is a place equipped for astronomical observations.

M.K. Vainu Bappu, known as the father of modern Indian astronomy, helped establish telescopes at Manora Peak near Nainital and at Kavalur. The Kavalur observatory is named after him. He mainly studied stars, discovered a comet and travelled to study solar eclipses.

Glossary

• Rotation — Motion in which an object’s parts move in circles around an imaginary line passing through it.
• Axis of rotation — The imaginary line through an object around which its parts move during rotation.
• Hemisphere — Half of the Earth; the Equator separates the Northern and Southern Hemispheres.
• Apparent motion — Movement an observer sees, such as the Sun’s daily motion caused by the Earth’s rotation.
• Revolution — The movement of one object around another, such as the Earth around the Sun.
• Orbit — The path an object follows while revolving around another object in space.
• Pole Star — The star close to the direction of the Earth’s axis that appears nearly stationary.
• Star trails — Arcs in long-exposure photographs that record the apparent movement of stars across the sky.
• Summer solstice — The occasion of longest daytime, occurring around 21 June in the Northern Hemisphere.
• Winter solstice — The occasion of shortest daytime and longest night, around 22 December in the Northern Hemisphere.
• Equinox — An occasion when daytime lasts for 12 hours, around 21 March and 23 September.
• Apparent size — The size an object appears to have, depending on its physical size and distance.
• Solar eclipse — An event in which the Moon comes between the Sun and Earth and blocks sunlight reaching us.
• Lunar eclipse — An event in which the Earth blocks sunlight from reaching the Moon, casting its shadow on it.
• Total lunar eclipse — A lunar eclipse in which the Moon is completely within the Earth’s shadow and appears dark red.

Common errors and misconceptions

• Misconception: The Earth’s revolution causes day and night. Correct: Rotation brings locations into sunlight and then darkness. Revolution is the separate movement around the Sun.
• Misconception: The Earth rotates from East to West because the Sun appears to move westwards. Correct: The Earth rotates from West to East, producing the Sun’s apparent daily motion in the opposite direction.
• Misconception: The Pole Star is exactly motionless in our sky. Correct: It appears nearly stationary because the Earth’s axis points very close to it.
• Misconception: Summer occurs because the Earth is much closer to the Sun. Correct: Seasons arise from the tilted axis and spherical shape, affecting sunlight intensity and daytime length. The Earth is closest to the Sun in January.
• Misconception: Both hemispheres have summer in June. Correct: June brings summer in the Northern Hemisphere and winter in the Southern Hemisphere; the situation reverses in December.
• Misconception: The Moon must be physically as large as the Sun to cover it. Correct: Their apparent sizes are similar because the much smaller Moon is much closer to the Earth.
• Misconception: The Sun lies between the Earth and Moon during a lunar eclipse. Correct: The Earth is in the middle and blocks sunlight reaching the Moon.
• Misconception: An eclipsed Sun is safe to view directly or through sunglasses. Correct: It can still damage eyes and cause blindness. Use organised viewing with specialised protection; the eclipsed full Moon can safely be viewed with the naked eye.

Exam-style questions with model answers

Q1. State the direction of the Earth’s rotation and the approximate time it takes for one rotation. [2 marks]

1. The Earth rotates from West to East, which is anti-clockwise when viewed from above the North Pole.
2. It takes about 24 hours to complete one rotation on its axis.

Q2. A globe is lit from one side by a torch and rotated from West to East. A sticker marks a location on it. Explain what the lit and dark halves represent and what happens as the sticker moves into and out of the light. [3 marks]

1. The torch represents the Sun. The half of the globe facing it receives light and represents daytime, while the unlit half represents night.
2. As the sticker moves into the light, its location experiences sunrise and enters daytime. The location changes position because the globe rotates.
3. As the sticker moves into darkness, its location experiences sunset and enters night. Continued rotation produces the repeating day-night cycle.

Q3. Explain rotation and revolution of the Earth in four points: compare their movements, compare the time taken for one cycle, describe the daily effects of rotation, and explain the yearly change in the night sky caused by revolution. [4 marks]

1. Rotation is the Earth spinning around its own axis. Revolution is its movement around the Sun along its orbit.
2. One rotation takes about 24 hours, whereas one revolution takes about 365 days and 6 hours.
3. Rotation explains day and night and the daily apparent motion of the Sun, Moon and stars across the sky.
4. Revolution changes the direction in which we look into the night sky over a year, so the stars seen after sunset gradually change.

Q4. Explain why June brings summer in the Northern Hemisphere and winter in the Southern Hemisphere. Include the Earth’s tilt, its spherical shape, sunlight intensity and the length of daytime. [5 marks]

1. The Earth’s axis is tilted, and this tilt is maintained as the Earth moves around the Sun. In June, the Northern Hemisphere tilts towards the Sun.
2. Because the Earth is spherical, a given amount of sunlight spreads over a smaller area in the Northern Hemisphere than in the Southern Hemisphere.
3. This more concentrated sunlight is more intense and heats the receiving area more. The Northern Hemisphere also receives sunlight for more than 12 hours.
4. More intense sunlight acting for a longer time produces summer in the Northern Hemisphere. Both effects belong in the explanation of its greater heating.
5. The Southern Hemisphere is tilted away from the Sun, has less intense sunlight and shorter daytime, and experiences winter. The hemispheres have opposite seasons.

Q5. Compare solar and lunar eclipses using five features: the order of the objects, the object blocking sunlight, where the shadow falls, the meaning of a total eclipse, and viewing precautions. [5 marks]

1. In a solar eclipse, the order is Sun, Moon, Earth. In a lunar eclipse, the order is Sun, Earth, Moon.
2. The Moon blocks sunlight from reaching the affected area of the Earth during a solar eclipse. The Earth blocks sunlight reaching the Moon during a lunar eclipse.
3. The Moon’s shadow falls on a small area of the Earth in a solar eclipse. The Earth’s shadow falls on the Moon in a lunar eclipse.
4. A total solar eclipse covers the entire Sun from the affected observer’s view. A total lunar eclipse places the Moon completely within the Earth’s shadow.
5. Direct solar-eclipse viewing must be avoided; organised viewing provides specialised protection. An eclipsed full Moon can safely be watched with the naked eye.

Q6. The Moon is physically much smaller than the Sun but much closer to the Earth. Use these facts to explain how it can cover the Sun from our view. Define apparent size in your answer. [3 marks]

1. Apparent size is the size an object seems to have to the eye. It depends on both actual physical size and distance from the observer.
2. The Moon is much smaller than the Sun, but it is also much closer to the Earth. Consequently, their apparent sizes in the sky are similar.
3. When the Moon comes between the Sun and Earth in a suitable position, it can therefore cover the whole Sun from an affected observer’s view.

Q7. One learner proposes looking directly at an eclipsed Sun, another proposes sunglasses, and a third suggests a planetarium’s organised viewing event. Explain the safe choice and the precautions required if a teacher uses mirror projection onto a screen. [4 marks]

1. Direct viewing is unsafe because the Sun remains intense enough during an eclipse to damage the eyes and cause blindness.
2. Sunglasses are not an acceptable viewing method. Viewing through binoculars or telescopes must also be avoided.
3. The organised event is the safe choice described here because the organisers provide specialised solar-viewing eye protection and scientific explanations.
4. Mirror projection must be set up and performed strictly under a teacher’s supervision. Observe the image on the screen and never direct the reflected light into anyone’s eyes.

Q8. During one Earth rotation of about 24 hours in June, the North Pole remains entirely in sunlight and the South Pole entirely in darkness. How much sunlight does each pole receive during that rotation? [2 marks]

1. The North Pole receives about 24 hours of sunlight because it remains in the illuminated region throughout the stated rotation.
2. The South Pole receives no sunlight during that rotation because it remains entirely in darkness throughout the stated interval.

Key takeaways

• The Earth rotates from West to East in about 24 hours, causing day and night and daily apparent sky movement.
• The Pole Star appears nearly stationary because the Earth’s rotation axis points very close to it.
• The Earth revolves around the Sun in about 365 days and 6 hours, gradually changing the night sky we see.
• The Earth’s tilted axis and spherical shape produce seasonal differences in sunlight intensity and the duration of daytime.
• The Northern and Southern Hemispheres experience opposite seasons, with summer in the south during December.
• Apparent size depends on actual size and distance, explaining how the Moon can cover the Sun from our view.
• A solar eclipse places the Moon between the Sun and Earth; a lunar eclipse places the Earth between the Sun and Moon.
• Never view a solar eclipse directly; organised viewing provides specialised protection, while the eclipsed full Moon is safe for naked-eye observation.

Test yourself

What is the Earth’s axis of rotation?

It is the imaginary line through the Earth’s geographic North and South Poles around which the Earth rotates.

Why does sunrise occur first in eastern India?

The Earth rotates from West to East, bringing the eastern part of India into sunlight before other parts.

What is the difference between observing stars two hours apart and a month apart at the same night-time?

Observations two hours apart show apparent movement caused by rotation. Comparing the sky a month apart at a fixed time reveals the gradual change associated with revolution.

Why should the Earth’s orbit be described as nearly circular when viewed from above?

That is its appearance from above; a side view makes it appear elongated. The viewing direction matters when interpreting a drawing.

Why does the Northern Hemisphere have greater heating in June?

It receives more intense sunlight spread over a smaller area, and sunlight lasts for more than 12 hours.

What happens around 22 December in the Northern Hemisphere?

The winter solstice occurs, bringing the shortest daytime and longest night of the year in that hemisphere.

Why is a total solar eclipse visible at an affected location for only a few minutes?

The Earth’s rotation and the Moon’s motion in its orbit move the Moon’s shadow across the Earth’s surface.

How does the Moon appear during a total lunar eclipse?

Its bright disc begins to appear dark red and remains so until the Moon moves out of the Earth’s shadow.