Test: Introduction to Earth & Universe- 1 - UPSC MCQ

1. Mercury - Smallest and closest to the sun

   • Correct. Mercury is indeed the smallest planet in our solar system and the closest to the sun.

2. Jupiter - Second largest planet with 12 satellites

   • Incorrect. Jupiter is the largest planet in our solar system, not the second largest. Also, Jupiter has at least 80 known moons (as of 2023), not just 12.

3. Uranus - Orbits around the sun in a clockwise direction from east to west

   • Correct. Uranus has an axial tilt of about 98 degrees, which means it essentially orbits the sun on its side, appearing to rotate clockwise (retrograde rotation) when viewed from a certain perspective.

4. Neptune - Natural satellite is the moon

   • Incorrect. Neptune has 14 known moons, with Triton being its largest. The statement is wrong because:
     a) "The moon" specifically refers to Earth's moon
     b) Neptune doesn't have just one natural satellite

Correctly matched pairs: 1 and 3 (two pairs)

1. Solar Eclipse - Occurs at full moon.
Incorrect. A solar eclipse occurs when the moon comes exactly between the Earth and the Sun, which happens at new moon, not full moon.

2. Lunar Eclipse - Occurs at new moon.
Incorrect. A lunar eclipse occurs when the Earth comes exactly between the Sun and the Moon, which happens at full moon, not new moon.

3. Dawn - Period between sunset and complete darkness.
Incorrect. Dawn is the period between sunrise and full daylight, not between sunset and complete darkness. The correct term for the period between sunset and complete darkness is twilight.

4. Twilight - Period between sunrise and full daylight.
Incorrect. Twilight refers to the period between sunset and complete darkness, not as the period between sunrise and full daylight. In this context, it is incorrectly matched.

Only the fourth pair is correctly matched, making the answer Option A: No pair.

Statement-I is correct as the Earth does indeed rotate around its own axis from west to east in an anticlockwise direction. This rotation causes the phenomena of day and night.
Statement-II is also correct as the velocity of the Earth's rotation does decrease from the equator to the poles. This is due to the Earth being an oblate spheroid, causing a greater circumference at the equator than at the poles. The decrease in velocity from the equator to the poles is related to the conservation of angular momentum.
While both statements are correct, Statement-II does not directly explain Statement-I. The Earth's rotation direction and the change in velocity from equator to poles are related phenomena but do not explain each other in a causal or explanatory manner. Hence, option (b) is the correct answer.

• Statement-I: Correct
  The Tropic of Cancer experiences about 14 hours of daylight during the Summer Solstice. This is because the Northern Hemisphere is tilted towards the sun, resulting in longer daylight hours.

• Statement-II: Correct
  The Equator consistently has 12 hours of daylight every day of the year. This is due to its position, where day and night lengths remain nearly equal throughout the year.

• However, Statement II does not explain why the Tropic of Cancer has fourteen hours of daylight during the Summer Solstice. The reason for the longer day at the Tropic of Cancer is the tilt of the Earth's axis, not the situation at the Equator.

Statement-I is about the time it takes for light from the nearest star to reach Earth. The actual time is approximately 4 years, as the closest star is Proxima Centauri, part of the Alpha Centauri star system. Therefore, this statement is incorrect.
Statement-II discusses Neptune's temperature. Neptune is indeed much colder than Earth due to its significant distance from the Sun, making this statement correct.

Therefore,Correct Answer - Option D

The Earth moves in space by rotating on its own axis from west to east every 24 hours, causing the phenomena of day and night. Additionally, it revolves around the sun in an elliptical orbit every 365.25 days, resulting in the changing seasons and marking the passage of a year. These two motions, rotation, and revolution, are fundamental to various natural phenomena on Earth, including the length of days, seasonal variations, and the distribution of sunlight across the planet.

Statement 1: The Earth's axis is indeed inclined at 23.5° to the perpendicular to the plane of the ecliptic. This inclination is responsible for the seasonal changes experienced on Earth. Since this is a factual statement about Earth's axial tilt, it is correct.

Statement 2: The Tropic of Cancer does not receive vertical sunrays at the winter solstice. Instead, it receives vertical sunrays at the summer solstice, when the Northern Hemisphere is tilted towards the sun. During the winter solstice, the Tropic of Capricorn receives vertical sunrays as the Southern Hemisphere is tilted towards the sun. Therefore, this statement is incorrect.

Statement 3: The length of latitudes, or parallels, does indeed decrease from the equator to the poles. This is because the circumference of the Earth is greatest at the equator and gradually reduces towards the poles. Hence, this statement is correct.

Given the correctness of statements 1 and 3, the correct answer is:

Option C: 1 and 3 Only

• During summer, the sun is overhead, so its rays fall almost vertically on the Earth.
• This concentrates heat on a small area, causing temperatures to rise and making summers warm.
• In winter, the sun's rays are more oblique and spread over a larger area.
• These rays travel through the atmosphere less directly, losing heat to the air and water vapour.
• As a result, the temperature remains low in winter.

Both statements are correct, and the explanation in Statement-II supports the observations in Statement-I.

• During the winter solstice at the Tropic of Capricorn, the duration of daylight is approximately 12 hours.
• This occurs because the Tropic of Capricorn is the latitude where the sun is directly overhead at noon during the solstice.
• Thus, the day lengths are relatively equal to the night lengths, resulting in approximately 12 hours of daylight.

Therefore,Correct Answer- Option C

- Statement 1 is correct. Dawn is indeed the brief period between sunrise and full daylight. During dawn, the earth receives diffused or refracted light from the sun while it is still below the horizon.

- Statement 2 is correct. Twilight is the period between sunset and complete darkness. Similar to dawn, it is caused by the earth receiving diffused or refracted light from the sun when it is below the horizon.

- Statement 3 is incorrect. The duration of twilight is not the same at the equator and the poles. At the equator, the sun rises and sets in a vertical path, resulting in a shorter duration of refracted light. In contrast, at the poles, the sun rises and sets in an oblique path, resulting in a much longer period of twilight.

Therefore, the correct answer is Option B.

A supernova occurs when a massive star exhausts its nuclear fuel and undergoes a catastrophic explosion at the end of its life cycle, releasing vast amounts of energy and forming heavy elements. This distinguishes it from star formation, neutron star mergers, or black hole formation from white dwarfs.

1. Winter Solstice in the Southern Hemisphere: Day lasts for 6 months at the South Pole
Incorrect. The South Pole experiences 6 months of darkness during the Winter Solstice (21 December), not daylight. The North Pole experiences 6 months of daylight instead.

2. Equinoxes: Sun's rays are vertical at the Tropic of Cancer on 21 March and 21 September
  This statement is incorrect. During the Equinoxes (around March 21 and September 23), the Sun's rays are vertical at the Equator, not at the Tropic of Cancer.

3. Summer Solstice: Sun's rays fall vertically at the Tropic of Capricorn on 21 June
   This statement is incorrect. During the Summer Solstice (around June 21), the Sun's rays fall vertically at the Tropic of Cancer, not the Tropic of Capricorn.

4. Seasonal Changes: Longer days in summer lead to higher temperatures
   This statement is correct. Longer days in summer result in more hours of sunlight, which leads to higher temperatures.

Only the last statement about seasonal changes is correct. Therefore, Correct Answer- Option A

On June 21 (Summer Solstice), the Sun does not set below the horizon at the Arctic Circle, resulting in 24 hours of daylight, known as the Midnight Sun phenomenon.

A protostar forms during the birth of a new star when a cloud of interstellar gas and dust undergoes gravitational collapse, heating up and beginning nuclear fusion. This process is distinct from a supernova, neutron star mergers, or black hole formation from a white dwarf.

• Comets have highly elliptical orbits and are mainly made up of ice and dust. This gives them their bright appearance when they get close to the Sun.
• The tail of a comet always points away from the Sun. This is because the solar wind and radiation pressure push the gas and dust in this direction.
• Halley's Comet is a famous example that appears about once every 76 years, making it a well-known periodic comet.

All three statements are correct. Therefore,Correct Answer - Option C