That Earth is spherical in space is not proved by which of the following statements: I. If Earth were flat there would be some sharp edges to be found by travellers. II. Solar eclipses show the shadow of earth as circular. III. Sunrise is not visible from all places on Earths surface at the same time. IV. The altitude of stars seen from different places on Earths surface vary,

1. Earth's Shape: The Concept of the Geoid (basic)

When we look at a globe, the Earth appears to be a perfect, smooth sphere. However, in reality, the Earth's shape is slightly more complex. It is technically described as an oblate spheroid or, more accurately, a Geoid. This means the Earth is not perfectly round; it is slightly flattened at the North and South Poles and features a noticeable bulge at the Equator. This characteristic shape is a direct result of the Earth's rotation on its axis. As the Earth spins, the centrifugal force (the outward force felt by a rotating object) is strongest at the Equator because that part of the Earth is moving the fastest. Over millions of years, this force has pushed the Earth's mass outward at the middle while flattening the top and bottom Physical Geography by PMF IAS, Latitudes and Longitudes, p.241.

The term Geoid literally means "Earth-shaped." It refers to the physical surface of the Earth as defined by gravity. Because the Earth's mass is not distributed perfectly evenly (think of massive mountain ranges versus deep ocean trenches), the force of gravity varies slightly from place to place. This causes the "sea level" surface to undulate. One critical consequence of this shape is that the gravitational pull is not uniform across the globe; it is actually stronger at the poles (since they are closer to the Earth's center of mass) and weaker at the equator Physical Geography by PMF IAS, Latitudes and Longitudes, p.241.

Feature	At the Equator	At the Poles
Shape	Bulged outward	Flattened
Radius	Larger (approx. 21 km more)	Smaller
Gravity	Relatively Weaker	Relatively Stronger

Historically, long before satellite imagery confirmed this, humans deduced the Earth was spherical through observation. Early proofs included the circumnavigation of the globe by explorers like Ferdinand Magellan Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.4, the circular shadow cast by the Earth on the Moon during a lunar eclipse, and the fact that different constellations (like the Pole Star) appear at different altitudes in the sky depending on your latitude. If the Earth were flat, everyone on Earth would see the sun rise at the exact same moment and view the same stars at the same angles, which we know is not the case.

Sources: Physical Geography by PMF IAS, Latitudes and Longitudes, p.241; Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.4; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Solar Radiation, Heat Balance and Temperature, p.67

2. Earth's Rotation and the Day-Night Cycle (basic)

Earth’s rotation is the spinning movement of the planet around its own axis. This axis is an imaginary line that passes through the North Pole, the Earth's center, and the South Pole. A fundamental fact to remember is the direction of this spin: Earth rotates from West to East. This counter-clockwise motion (when viewed from above the North Pole) is the reason why the Sun, Moon, and stars appear to rise in the east and set in the west Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.251.

The most immediate consequence of this rotation is the Day and Night cycle. Because the Earth is a sphere, the Sun can only illuminate one half of it at any given time. The boundary that separates the lighted portion of the Earth from the dark portion is known as the Circle of Illumination. As the Earth rotates, different parts of the globe cross this line, moving from darkness into light (sunrise) or light into darkness (sunset) Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.251. It takes approximately 24 hours (specifically 23 hours, 56 minutes, and 4 seconds) to complete one full rotation.

Beyond light and dark, rotation also drives critical physical phenomena. One of the most significant is the Coriolis Force. This is an inertial force caused by the Earth's rotation that deflects moving objects, such as winds and ocean currents, to the right in the Northern Hemisphere and to the left in the Southern Hemisphere Fundamentals of Physical Geography (NCERT Class XI), Atmospheric Circulation and Weather Systems, p.78. Interestingly, the strength of this force is not uniform; it is zero at the equator and reaches its maximum at the poles Physical Geography by PMF IAS, Pressure Systems and Wind System, p.309.

Feature	Description
Direction	West to East
Duration	~24 Hours (Solar Day)
Primary Effect	Day and Night cycle
Physical Force	Coriolis Effect (Deflection of winds)

Sources: Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.251; Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.268; Fundamentals of Physical Geography (NCERT Class XI), Atmospheric Circulation and Weather Systems, p.78; Physical Geography by PMF IAS, Pressure Systems and Wind System, p.309

3. Solar vs. Lunar Eclipses: Shadow Mechanics (intermediate)

To understand eclipses, we must first look at them as a simple game of shadows. An eclipse occurs when one celestial body moves into the shadow of another. The mechanics depend entirely on the alignment of three actors: the Sun (the light source), the Earth, and the Moon. While they might seem like rare celestial events, they are predictable results of orbital geometry.

In a Lunar Eclipse, the Earth is the central player. It positions itself directly between the Sun and the Moon, blocking sunlight from reaching the lunar surface. We see the Earth's shadow falling on the full disc of the Moon Science-Class VII, Earth, Moon, and the Sun, p.182. These shadows have two distinct zones: the Umbra (the darkest, central part where the light is completely blocked) and the Penumbra (the outer, lighter part where light is only partially blocked). If the Moon passes entirely through the Umbra, we witness a Total Lunar Eclipse, often turning the Moon a deep red due to Earth's atmosphere scattering sunlight Science-Class VII, Earth, Moon, and the Sun, p.183.

Conversely, a Solar Eclipse occurs when the Moon moves between the Sun and the Earth, casting its shadow onto our planet. Even though the Moon is much smaller than the Sun, it can block the Sun completely because it is nearly 400 times closer to us than the Sun is Science-Class VII, Earth, Moon, and the Sun, p.186. Because the Moon’s shadow is relatively small, a total solar eclipse is only visible from a very narrow path on the Earth's surface, unlike a lunar eclipse which can be seen from almost anywhere on the night side of the Earth.

You might wonder: If the Moon orbits Earth every month, why don't we have eclipses every single month? The answer lies in the Orbital Tilt. The Moon’s path around the Earth is tilted at an angle of about 5.1° relative to the Earth’s orbital plane around the Sun Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.265. Most of the time, the Moon passes slightly "above" or "below" the direct line of sight between the Sun and Earth, missing the shadow entirely.

Feature	Lunar Eclipse	Solar Eclipse
Body in the Middle	Earth	Moon
Lunar Phase	Full Moon	New Moon
Visibility	Visible to half the planet	Visible in a narrow path

Sources: Science-Class VII, Earth, Moon, and the Sun, p.182; Science-Class VII, Earth, Moon, and the Sun, p.183; Science-Class VII, Earth, Moon, and the Sun, p.186; Physical Geography by PMF IAS, The Motions of The Earth and Their Effects, p.265

4. Latitudinal Variations: Heat Zones and Star Altitudes (intermediate)

To understand how our planet works, we must first look at latitude—not just as lines on a map, but as the angular distance of a place north or south of the equator, measured from the Earth’s center Physical Geography by PMF IAS, Latitudes and Longitudes, p.240. Because the Earth is a sphere, this angle determines two critical things: how much heat we receive from the Sun and which stars we see in the night sky. Since the Earth is slightly flattened at the poles (an oblate spheroid), the linear distance of 1° of latitude actually increases slightly as you move from the equator (~110.6 km) toward the poles (~111.7 km) Physical Geography by PMF IAS, Latitudes and Longitudes, p.240.

The curvature of the Earth creates distinct Heat Zones. At the Equator, the Sun’s rays strike vertically, concentrating energy over a small area. As we move toward the poles, the Earth curves away, causing the rays to strike at an angle. These slanting rays must travel through more atmosphere and spread over a larger surface area, providing less heat. This gives us the Torrid Zone (hot, between the Tropics), the Temperate Zones (moderate), and the Frigid Zones (cold, near the poles).

Beyond heat, latitudinal variation is the reason for the changing positions of stars. The Pole Star (Polaris) sits almost directly above the Earth's North Pole axis Physical Geography by PMF IAS, The Universe, p.16. If the Earth were flat, the Pole Star would appear at the same angle to everyone on Earth. However, because the Earth is curved, the altitude of the Pole Star (its height above the horizon) changes with your latitude. If you are at the North Pole (90°N), Polaris is directly overhead; at the Equator (0°), it rests on the horizon. This variation is a classic proof of the Earth’s sphericity Certificate Physical and Human Geography, GC Leong, Chapter 2, p.4.

Similarly, constellations like Ursa Major (the Big Dipper) appear to revolve around the Pole Star because of the Earth's rotation Science-Class VII NCERT, Earth, Moon, and the Sun, p.174. As you travel south across the equator, these northern constellations eventually dip below the horizon and vanish, replaced by southern stars like the Southern Cross. This "hiding" of stars behind the Earth’s curve would be impossible on a flat surface Physical Geography by PMF IAS, The Universe, p.15.

Sources: Physical Geography by PMF IAS, Latitudes and Longitudes, p.240; Physical Geography by PMF IAS, The Universe, The Big Bang Theory, Galaxies & Stellar Evolution, p.15-16; Science-Class VII NCERT, Earth, Moon, and the Sun, p.174; Certificate Physical and Human Geography, GC Leong, Chapter 2: The Earth's Crust, p.4-5

5. Longitude and Time: Non-Simultaneous Sunsets (intermediate)

Have you ever wondered why, when it’s a bright morning in Tokyo, it’s still the middle of the night in London? This phenomenon is one of the most elegant proofs of our planet's shape and movement. The Earth is a sphere that rotates on its axis from West to East. Because of this rotation, only one half of the Earth faces the Sun at any given time, while the other half remains in darkness Certificate Physical and Human Geography, The Earth's Crust, p.6. As the Earth turns, different longitudes are gradually brought into the Sun’s rays. This is why sunrise and sunset occur at different times across the globe.

If the Earth were flat, the entire world would see the Sun rise at the exact same moment. However, because the surface is curved, places in the East (like Japan or Northeast India) see the Sun earlier than places in the West (like Gujarat or Europe). In India, for instance, there is a time lag of nearly two hours between the sunrise in Arunachal Pradesh and the sunrise in Jaisalmer, Rajasthan INDIA PHYSICAL ENVIRONMENT, India — Location, p.2. To avoid the chaos of every town having its own local time based on the Sun's position, countries adopt a Standard Meridian. India uses 82°30' E as its standard, which is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT) Physical Geography by PMF IAS, Latitudes and Longitudes, p.245.

The relationship between longitude and time is purely mathematical. Since the Earth completes one full 360° rotation in 24 hours, we can calculate the following:

Rotation Scale	Time Duration
360° (Full Circle)	24 Hours
15° (Time Zone)	1 Hour (60 minutes)
1° (Longitude)	4 Minutes

Countries with a massive East-West span, such as Russia (11 time zones) or the USA and Canada (6 time zones each), find it impossible to function with just one standard time. They divide their territory into multiple zones to ensure that "noon" on the clock actually aligns somewhat with the Sun being at its highest point in the sky Physical Geography by PMF IAS, Latitudes and Longitudes, p.243.

Sources: Certificate Physical and Human Geography, The Earth's Crust, p.6; INDIA PHYSICAL ENVIRONMENT, India — Location, p.2; Physical Geography by PMF IAS, Latitudes and Longitudes, p.243-245

6. Classic Proofs of Earth's Sphericity (exam-level)

Before the era of satellite imagery, humanity relied on logical deduction and celestial observation to understand the Earth's true shape. While we now have the 'ultimate proof' through high-altitude photographs showing the Earth's curved edge Certificate Physical and Human Geography, Chapter 2, p.4, classic proofs remain essential for understanding physical geography. One of the most intuitive proofs is circumnavigation. If the Earth were a flat plane with edges, a traveler would eventually reach a boundary; instead, explorers like Ferdinand Magellan proved between 1519 and 1522 that by sailing in one general direction, one eventually returns to the starting point Certificate Physical and Human Geography, Chapter 2, p.4.

Celestial phenomena provide even more rigorous evidence. During a lunar eclipse, the Earth casts a shadow on the Moon. This shadow is always circular; only a spherical body can cast a circular shadow from every possible angle. It is crucial to distinguish this from a solar eclipse, where the Moon's shadow falls on the Earth. Furthermore, the varying altitude of stars proves curvature. For instance, the Pole Star (Polaris) appears directly overhead at the North Pole (90° latitude) but sinks toward the horizon as one travels south, disappearing entirely once the Equator is crossed Certificate Physical and Human Geography, Chapter 2, p.5.

Finally, the timing of sunrise and sunset offers daily proof of sphericity. Because the Earth rotates from west to east on a curved surface, different places experience sunrise at different times. If the Earth were flat, the Sun would rise and set at the exact same moment for every person on the planet Exploring Society: India and Beyond (NCERT Class VI 2025), Chapter 1, p.12. Similarly, when watching a ship approach from the horizon, the mast appears first and the hull last—a phenomenon only possible if the ship is 'climbing' up the curve of the Earth's surface.

Sources: Certificate Physical and Human Geography (GC Leong), Chapter 2: The Earth's Crust, p.4-5; Exploring Society: India and Beyond (NCERT Class VI), Chapter 1: Locating Places on the Earth, p.12

7. Solving the Original PYQ (exam-level)

Now that you have mastered the fundamental concepts of Earth's geometry and its relationship with celestial bodies, this question tests your ability to apply that knowledge with precision. The building blocks you've learned—such as the rotation of the Earth, the behavior of latitudinal variation, and the mechanics of eclipses—all converge here. According to Certificate Physical and Human Geography, GC Leong, the proofs for the Earth’s sphericity are grounded in observable phenomena: the fact that sunrise occurs at different times across the globe (Statement III) and that the altitude of stars changes as a traveler moves north or south (Statement IV) are direct consequences of a curved surface. Furthermore, as noted in NCERT Class VI: Exploring Society, the logical absence of a "sharp edge" (Statement I) supports the concept of a continuous, spherical surface rather than a flat disc.

The reasoning required to identify the correct answer, (C) Only II, hinges on a single, subtle distinction. While it is true that a circular shadow cast by the Earth is a definitive proof of its shape, Statement II incorrectly attributes this to a solar eclipse. In a solar eclipse, the Moon passes between the Earth and the Sun, casting the Moon's shadow onto our planet. It is actually during a lunar eclipse—when the Earth passes between the Sun and the Moon—that the Earth casts its circular shadow on the lunar surface. Because Statement II misidentifies the astronomical event, it fails as a valid proof.

UPSC frequently uses "trap" options like (A) and (D) to catch students who recognize a familiar phrase—like "circular shadow"—but do not pause to verify the technical accuracy of the surrounding details. Statements I, III, and IV are all scientifically sound proofs of sphericity; therefore, they cannot be part of the answer for a question asking which statement does not prove the concept. By carefully deconstructing the mechanics of each celestial event, you can avoid these common pitfalls and identify when a correct principle is being applied to the wrong phenomenon.