GC Leong Test: The Earth and the Universe - UPSC MCQ

- Statement 1 is correct. The Winter Solstice occurs around December 21st or 22nd when the Earth's axis is tilted at approximately 23.5 degrees towards the Southern Hemisphere. This tilt causes the Sun's rays to fall directly on the Tropic of Capricorn, marking the start of summer in the Southern Hemisphere and winter in the Northern Hemisphere.

- Statement 2 is incorrect. During the Winter Solstice, the Northern Hemisphere experiences the shortest day and the longest night of the year, not the longest day. This is because the Sun is at its lowest point in the sky, resulting in the shortest amount of daylight.

- Statement 3 is incorrect. Although the Equator generally experiences roughly equal day and night lengths throughout the year, it is not exactly 12 hours each day. The duration can vary slightly due to the Earth's axial tilt and atmospheric refraction, which can affect the precise length of day and night.

Therefore, only statement 1 is correct, making Option A: 1 Only the correct answer.

1. Rotation of Earth - Incorrect. The Earth rotates from west to east, not east to west. This rotation is responsible for the apparent daily motion of the sun across the sky.

2. Inclination of Earth's Axis - Correct. The Earth's axis is inclined at 23.5° to the perpendicular to the plane of the elliptic. This inclination causes the variation in solar intensity experienced in different parts of the world, leading to seasons.

3. Velocity of Earth's Rotation - Incorrect. The velocity of Earth's rotation is highest at the equator and decreases towards the poles. This is due to the greater circumference at the equator compared to the poles.

4. Polestar - Incorrect. The Polestar, or Polaris, is not the brightest star in the sky, but it is the brightest star in the constellation Ursa Minor and is located nearly at the north celestial pole, making it an important navigational star in the northern hemisphere.

Hence, only pair 2 is correctly matched.

The varying lengths of day and night throughout the year are primarily caused by the Earth's axial tilt, which is inclined at 23.5 degrees to the perpendicular to the plane of its orbit around the sun. This tilt results in different parts of the Earth receiving varying amounts of sunlight at different times of the year, leading to the changing seasons. When one hemisphere is tilted towards the sun, it experiences longer days and shorter nights, while the other hemisphere experiences shorter days and longer nights. This phenomenon is essential for the seasonal changes we observe on Earth.

1. Jupiter - Largest planet with 12 satellites: Incorrect. Jupiter is indeed the largest planet, but it has more than 12 satellites. As of current knowledge, it has 79 known moons.

2. Uranus - Orbits the sun in a clockwise direction from east to west: Correct. Uranus is unique among the planets as it rotates on its side with its axis nearly parallel to the orbital plane, and it orbits the sun in a clockwise direction from east to west.

3. Venus - Twice the distance from the sun compared to Earth: Incorrect. Venus is actually closer to the sun than Earth. It is the second planet from the sun, whereas Earth is the third.

4. Neptune - Outermost planet visible with telescopes: Correct. Neptune is the outermost planet in the solar system and can be observed with the help of telescopes. Pluto was once considered the outermost planet but has been reclassified as a dwarf planet.

Hence, pairs 2 and 4 are correctly matched.

During the Summer Solstice, which typically falls around 21/22 June, the Sun's rays fall vertically at the Tropic of Cancer. This marks the point when the Northern Hemisphere experiences the longest day of the year. The tilt of the Earth's axis causes the Sun to be directly overhead at the Tropic of Cancer, resulting in more direct sunlight and the start of the summer season in the Northern Hemisphere. This phenomenon also leads to varying daylight hours at different latitudes, with regions like the Arctic Circle experiencing 24-hour daylight during this period.

The sun is directly overhead at the equator on two particular days each year, which are usually on March 21st and September 21st. These days are known as the equinoxes, where all locations on Earth experience approximately equal durations of day and night. This phenomenon occurs due to the tilt of the Earth's axis and its orbit around the Sun, marking the transition between seasons.

Statement-I is accurate as the nearest star's light, traveling at the speed of light, takes around 4 years to reach Earth, a concept known as light-years. Statement-II correctly describes the composition of the Solar System, including the Sun and the 8 planets orbiting it in elliptical paths. However, Statement-II does not provide an explanation for the time taken for light from the nearest star to reach Earth, making option (b) the correct answer.

1. Statement 1 is correct. The axis of Earth's rotation is indeed inclined at 23.5° to a perpendicular to the plane of the ecliptic. This inclination is significant as it causes the seasonal variations experienced on Earth.

2. Statement 2 is incorrect. The velocity of Earth's rotation is actually greatest at the equator and decreases towards the poles. This is because the equatorial region is the widest part of the Earth, and thus, points on the equator must travel a longer distance in the same period (24 hours) compared to points near the poles.

3. Statement 3 is incorrect. The weight of a body is less at the equator than at the poles. This is due to the greater centrifugal force experienced at the equator as a result of the higher rotational velocity, which effectively reduces the gravitational force felt by an object. Additionally, the Earth's equatorial bulge means the surface is farther from the center of gravity, slightly reducing gravitational pull as well.

Thus, only statement 1 is correct. Hence, the correct answer is Option A: 1 Only.

(b) Both Statement I and Statement II are correct, but Statement II does not explain Statement I.

Here’s the breakdown:

1. Statement I is correct. The sun is vertically overhead at the equator twice a year, around March 21 (vernal equinox) and September 21 (autumnal equinox).

2. Statement II is also correct. The summer solstice, usually on June 21, occurs when the sun is directly overhead at the Tropic of Cancer, causing the longest day and shortest night in the northern hemisphere.

Although both statements are true, Statement II does not explain Statement I. Statement I refers to the equinoxes, when the sun is over the equator, whereas Statement II refers to the solstice, a different phenomenon related to the sun's position over the Tropic of Cancer.

Statement-I correctly explains the phenomenon of the Summer Solstice causing longer days in the Northern Hemisphere due to the tilt of the Earth's axis. Statement-II accurately describes the regions near the poles where there are periods of continuous day or night. The tilt of the Earth and the Sun's position during the solstice directly impact the lengths of days in different parts of the world. Thus, both statements are correct, and Statement-II provides additional context that supports Statement-I.

1. Statement 1: The Milky Way galaxy contains approximately 100,000 million stars. This statement is correct. The Milky Way is indeed estimated to contain around 100 billion stars, which corresponds to 100,000 million.

2. Statement 2: The planet Venus is located twice the distance from the Sun compared to Earth. This statement is incorrect. Venus is the second planet from the Sun, and it is not located twice the distance from the Sun compared to Earth. In fact, Venus is closer to the Sun than Earth is, making this statement false.

3. Statement 3: Neptune is the outermost planet in the solar system and is much colder than Uranus. This statement is incorrect. While Neptune is indeed one of the outermost planets, the statement that it is much colder than Uranus is misleading. Both planets are very cold, but Uranus is often considered to have a colder atmosphere in certain aspects. Additionally, the statement does not address the full context of Uranus and Neptune’s relative positions since Pluto, although reclassified as a dwarf planet, was traditionally considered the outermost planet.

Therefore, only statement 1 is correct, making Option A the correct choice.

- Statement-I: Incorrect. The Earth's axis is inclined at 66.5 degrees to the plane of the ecliptic, not the Tropic of Cancer. 

- Statement-II: Correct. The Earth's axis is tilted at 23.5 degrees from the perpendicular to the plane of the ecliptic, causing seasonal changes.

- Correct Answer: D. Statement-I is incorrect, but Statement-II is correct.

The shape of the Earth is primarily described as an oblate spheroid in the text. This means that the Earth is slightly flattened at the poles and slightly bulging at the equator. The concept of an oblate spheroid helps us understand the Earth's shape more accurately, considering its actual measurements and deviations from a perfect sphere.

1. Winter Solstice: Sun's rays fall vertically at the Tropic of Cancer.
Incorrect. During the Winter Solstice, which occurs around December 21/22, the sun's rays fall vertically at the Tropic of Capricorn, not the Tropic of Cancer. This marks the shortest day in the Northern Hemisphere.

2. Equinox: Sun is vertically overhead at the equator on 21 March and 21 September.
Correct. During the Equinoxes, which occur around March 21 and September 21, the sun is directly overhead at the equator. These are the days when all parts of the world experience approximately equal lengths of day and night.

3. Summer Solstice: Sun's rays fall vertically at the Tropic of Capricorn.
Incorrect. The Summer Solstice, occurring around June 21, is when the sun's rays fall vertically at the Tropic of Cancer, not the Tropic of Capricorn. This marks the longest day in the Northern Hemisphere.

4. Winter Season in Southern Hemisphere: The sun is overhead, and days are longer than nights.
Incorrect. During the winter season in the Southern Hemisphere, the sun is not overhead, and days are shorter than nights. The sun being overhead with longer days occurs during the summer season.

Only pairs 2 and none of the other pairs are correctly matched.

1. Summer Solstice - Sun’s rays fall vertical at the Tropic of Cancer.
This is correctly matched. During the Summer Solstice, which occurs around June 21st, the Sun is directly overhead at the Tropic of Cancer.

2. Winter Solstice - Sun’s rays fall vertical at the Tropic of Capricorn.
This is correctly matched. During the Winter Solstice, which occurs around December 21st, the Sun is directly overhead at the Tropic of Capricorn.

3. Equinox - Sun’s rays fall vertical at the Equator.
This is correctly matched. During the Equinoxes, which occur around March 21st and September 23rd, the Sun is directly overhead at the Equator.

4. Arctic Circle - Experiences 24 hours of daylight during the Summer Solstice.
This is incorrectly matched. The Arctic Circle experiences 24 hours of daylight during the Summer Solstice, but the question states it as a general occurrence without specifying the conditions of the solstice.

Pairs 1, 2, and 3 are correctly matched, while pair 4 is incorrectly matched because it lacks the specific context of the Summer Solstice for 24 hours of daylight. Thus, three pairs are correctly matched.