Earth's Movements (Rotation, Revolution)
Earth's Movements (Rotation, Revolution) MCQ Questions
13.
Local time increases as one moves:
ANSWER :
C. From west to east
Approach
The question asks about how local time changes with geographical movement. This relates to the Earth's rotation and its division into longitudes and time zones. We need to understand the relationship between the Earth's rotation, the sun's apparent movement, and the concept of local time.
Step-by-step
- Earth's Rotation: The Earth rotates on its axis from west to east. This rotation causes the apparent movement of the sun from east to west across the sky.
- Sun's Apparent Movement and Time: Because the Earth rotates from west to east, places located further east experience sunrise earlier than places located further west. When the sun is directly overhead (noon) at a particular longitude, it will already have passed that point for longitudes to its east, and it will yet to reach that point for longitudes to its west.
- Longitude and Time Difference: The Earth completes one full rotation (360 degrees) in approximately 24 hours. This means that for every 15 degrees of longitude, there is a time difference of 1 hour. Specifically, \(360 \text{ degrees} / 24 \text{ hours} = 15 \text{ degrees/hour}\).
- Direction of Time Change: As one moves eastward, they are moving towards where the sun has already risen or will rise sooner. Therefore, local time increases as one moves from west to east. Conversely, as one moves westward, they are moving towards where the sun will rise later, so local time decreases.
Correct Option:
C) From west to east — As the Earth rotates from west to east, the sun appears to move from east to west. This means places to the east experience sunrise earlier and thus have a later local time compared to places to their west. Therefore, local time increases as one moves from west to east.
Incorrect Options
- A) From north to south — Movement from north to south (or vice versa) along a single longitude does not significantly affect local time, as all points on the same longitude theoretically share the same local time (solar time).
- B) From south to north — Similar to option A, movement along a meridian (north to south or south to north) does not cause a change in local time.
- D) From east to west — As one moves from east to west, they are moving against the direction of the Earth's rotation relative to the sun's apparent movement. This means they encounter earlier times (the sun will rise later), so local time decreases, it does not increase.
14.
Which of the following latitudes experiences the longest day and shortest night on June 21?
A.
Tropic of Capricorn (23.5°S)
B.
Tropic of Cancer (23.5°N)
C.
Arctic Circle (66.5°N)
ANSWER :
C. Arctic Circle (66.5°N)
Approach
The question asks to identify the latitude that experiences the longest day and shortest night on June 21. This date marks the Summer Solstice in the Northern Hemisphere. We need to understand how the Earth's tilt and revolution around the Sun affect the duration of day and night at different latitudes.
Step-by-step
- Earth's Tilt and Solstices: The Earth is tilted on its axis by approximately \(23.5^\circ\) relative to its orbital plane around the Sun. This tilt causes the seasons. On June 21 (Summer Solstice in the Northern Hemisphere), the Northern Hemisphere is tilted most directly towards the Sun.
- Sun's Apparent Position: On June 21, the Sun's direct rays fall vertically on the Tropic of Cancer (\(23.5^\circ \text{N}\)). This means that all locations north of the Equator receive more direct sunlight and experience longer days.
- Daylight Duration in Northern Hemisphere: As one moves further north from the Equator towards the North Pole during the Northern Hemisphere's summer, the duration of daylight increases.
- Arctic Circle on June 21: The Arctic Circle (\(66.5^\circ \text{N}\)) is the southernmost latitude in the Northern Hemisphere where the Sun remains visible for 24 hours (polar day) on June 21. This means it experiences continuous daylight, which is the longest possible day.
- Longest Day and Shortest Night: A 24-hour day naturally implies the longest possible day and the shortest possible night (zero hours of night). Therefore, the Arctic Circle experiences the longest day and shortest night on June 21.
Correct Option:
C) Arctic Circle (66.5°N). On June 21, the entire region north of the Arctic Circle experiences 24 hours of daylight. The Arctic Circle itself marks the boundary where the sun does not set for at least one day around the summer solstice, making it the latitude that experiences the longest day and shortest night (zero night) among the given options.
Incorrect Options
- A) Tropic of Capricorn (23.5°S). On June 21, the Southern Hemisphere is tilted away from the Sun. Therefore, the Tropic of Capricorn experiences its shortest day and longest night, marking the winter solstice for the Southern Hemisphere.
- B) Tropic of Cancer (23.5°N). While the Sun's direct rays fall on the Tropic of Cancer on June 21, making it a very long day, it does not experience 24 hours of daylight. The duration of daylight is approximately 13.5 hours, which is long but not the longest possible.
- D) Equator (0°). The Equator experiences approximately 12 hours of day and 12 hours of night throughout the year, with very minor seasonal variations. It does not experience a significantly longer day or shorter night on June 21 compared to other latitudes in the Northern Hemisphere.
15.
The Earth completes one revolution around the Sun in approximately:
B.
365 days 5 hours 48 minutes 46 seconds
ANSWER :
B. 365 days 5 hours 48 minutes 46 seconds
Approach
This question tests knowledge of the Earth's orbital period around the Sun, also known as a sidereal year. Understanding the precise duration is crucial for concepts like leap years and astronomical calculations.
Step-by-step
- The Earth's revolution around the Sun defines a year. There are different types of years, but for general purposes and calendar systems, the sidereal year or tropical year is considered.
- A sidereal year is the time it takes for the Earth to complete one full orbit relative to the fixed stars. Its duration is approximately 365 days, 6 hours, 9 minutes, and 10 seconds.
- A tropical year (also known as a solar year) is the time it takes for the Sun to return to the same position in the cycle of seasons, as seen from Earth. This is the basis for our calendar year. Its duration is approximately 365 days, 5 hours, 48 minutes, and 46 seconds.
- The difference between the sidereal and tropical year is due to the precession of the equinoxes.
- Our Gregorian calendar is based on the tropical year to keep the seasons consistent. To account for the extra 5 hours, 48 minutes, and 46 seconds beyond 365 days, a leap day is added approximately every four years.
- Comparing the given options with the known astronomical values, option B provides the most accurate duration for the Earth's revolution around the Sun, specifically referring to the tropical year which is relevant for our calendar system.
Correct Option: B) 365 days 5 hours 48 minutes 46 seconds. This is the precise duration of a tropical year, which is the time it takes for the Earth to complete one orbit around the Sun relative to the equinoxes, and it forms the basis of our calendar system.
Incorrect Options
- A) 364 days — This is incorrect. It is significantly shorter than the actual orbital period.
- C) 366 days — This is incorrect. While a leap year has 366 days, the actual orbital period is not exactly 366 days; the extra day is an adjustment to account for the fractional part of the year.
- D) 365 days exactly — This is incorrect. If the Earth completed its revolution in exactly 365 days, there would be no need for leap years, and our calendar would gradually drift out of sync with the seasons. The extra approximately 6 hours per year accumulate to necessitate a leap day every four years.
16.
The change of seasons on Earth is primarily caused by:
A.
Earth's rotation speed
B.
The tilt of Earth's axis (23.5°) combined with revolution
C.
The elliptical shape of Earth's orbit only
D.
Earth's varying distance from the Sun
ANSWER :
B. The tilt of Earth's axis (23.5°) combined with revolution
Approach
The question asks for the primary cause of seasonal changes on Earth. We need to evaluate each option based on astronomical principles and their effect on Earth's climate.
Step-by-step
- Understand Earth's Movement: Earth has two main motions: rotation (spinning on its axis) and revolution (orbiting the Sun).
- Consider the Tilt of Earth's Axis: Earth's axis is not perpendicular to its orbital plane; it is tilted at approximately \(23.5^\circ\). This tilt is constant relative to the stars as Earth revolves around the Sun.
- Analyze the Effect of Tilt and Revolution: As Earth revolves, different parts of the planet receive more direct sunlight at different times of the year due to this axial tilt. When the Northern Hemisphere is tilted towards the Sun, it experiences summer because sunlight hits it more directly and for longer durations. Conversely, when it's tilted away, it experiences winter. The Southern Hemisphere experiences the opposite seasons.
- Evaluate Other Factors: Consider if Earth's rotation speed, orbital shape, or varying distance from the Sun significantly cause seasons. While Earth's orbit is slightly elliptical, the change in distance from the Sun is not the primary driver of seasons; in fact, Earth is closest to the Sun during the Northern Hemisphere's winter.
- Conclude the Primary Cause: The combination of Earth's axial tilt and its revolution around the Sun is the fundamental reason for the change of seasons.
Correct Option: B) The tilt of Earth's axis (\(23.5^\circ\)) combined with revolution. This is the correct answer. The constant tilt of Earth's axis relative to its orbital plane, combined with Earth's annual revolution around the Sun, causes different parts of the Earth to receive varying amounts of direct sunlight throughout the year. This variation in solar insolation leads to the change of seasons.
Incorrect Options
- A) Earth's rotation speed — Earth's rotation causes day and night, not the change of seasons. Its speed is relatively constant and does not explain seasonal variations.
- C) The elliptical shape of Earth's orbit only — While Earth's orbit is elliptical, the varying distance from the Sun is not the primary cause of seasons. For example, Earth is closest to the Sun (perihelion) in early January, which is winter in the Northern Hemisphere, and farthest (aphelion) in early July, which is summer in the Northern Hemisphere. This contradicts the idea that distance alone causes seasons. The effect of the tilt is far more significant.
- D) Earth's varying distance from the Sun — This is related to option C. As explained, the varying distance is not the primary factor. The difference in solar energy received due to the elliptical orbit is much less significant than the effect of the axial tilt on the angle at which sunlight strikes the Earth's surface.
17.
Earth is closest to the Sun (Perihelion) around:
Approach
The question asks about the Earth's closest approach to the Sun, known as perihelion. This is a specific astronomical event that occurs annually on a particular date. Understanding the Earth's elliptical orbit around the Sun is key to answering this.
Step-by-step
- The Earth's orbit around the Sun is not a perfect circle but an ellipse.
- Due to this elliptical orbit, there are times when the Earth is closer to the Sun (perihelion) and times when it is farther away (aphelion).
- Perihelion occurs when the Earth is at its closest point to the Sun. This event typically happens in early January each year.
- Aphelion, when the Earth is farthest from the Sun, occurs in early July.
- The exact date of perihelion can vary slightly from year to year, but it generally falls around January 3rd or 4th.
Correct Option:
D) January 3. The Earth reaches its perihelion (closest point to the Sun) around January 3rd each year. At this time, the Earth is approximately \(147.1\) million kilometers from the Sun.
Incorrect Options
- A) March 21 — This date is approximately the Northern Hemisphere's vernal (spring) equinox, when day and night are roughly equal in length. It has no direct relation to perihelion.
- B) September 23 — This date is approximately the Northern Hemisphere's autumnal (fall) equinox, when day and night are roughly equal in length. It has no direct relation to perihelion.
- C) July 4 — This date is approximately when the Earth reaches its aphelion (farthest point from the Sun), not perihelion. At aphelion, the Earth is about \(152.1\) million kilometers from the Sun.
18.
Earth is farthest from the Sun (Aphelion) around:
Approach
The question asks about the Earth's aphelion, which is the point in its orbit where it is farthest from the Sun. This phenomenon is a result of Earth's elliptical orbit around the Sun. We need to identify the approximate date when this occurs.
Step-by-step
- Understand Aphelion: The Earth's orbit around the Sun is not a perfect circle but an ellipse. Due to this elliptical path, there are times when Earth is closer to the Sun (perihelion) and times when it is farther away (aphelion).
- Identify the Date of Aphelion: The Earth reaches its aphelion, the point of maximum distance from the Sun, annually around early July. The exact date can vary slightly from year to year due to gravitational perturbations from other planets and the precession of Earth's orbit.
- Compare with Options:
- December 22 is close to the winter solstice in the Northern Hemisphere, and the Earth is generally closer to the Sun around this time (perihelion occurs in early January).
- July 4 falls within the typical period for aphelion.
- June 21 is the summer solstice in the Northern Hemisphere, but aphelion usually occurs a couple of weeks later.
- January 3 is the approximate date for perihelion, when Earth is closest to the Sun.
- Conclusion: Based on astronomical data, Earth is farthest from the Sun (aphelion) around July 4th.
Correct Option: B) July 4
Incorrect Options
- A) December 22 — This date is near the winter solstice in the Northern Hemisphere. Earth is actually closer to the Sun around this time, approaching its perihelion.
- C) June 21 — This is the summer solstice in the Northern Hemisphere, marking the longest day. While it's in the summer, aphelion typically occurs a couple of weeks later.
- D) January 3 — This date is approximately when Earth is closest to the Sun, a point known as perihelion, not aphelion.
