Which one of the following statements is not correct ?

1. Earth's Shape and the Geographic Grid System (basic)

Welcome to your first step in mastering geography! To understand how we locate any place on our vast planet, we must first look at the Earth's true shape. While we often call it a sphere, the Earth is actually a Geoid (or an oblate spheroid). Imagine taking a soft rubber ball and spinning it very fast; the center bulges out while the top and bottom flatten slightly. This is exactly what happens to Earth due to its rotation. The centrifugal force is strongest at the Equator, causing a bulge there, while the poles are flattened Physical Geography by PMF IAS, Latitudes and Longitudes, p.241. Because of this shape, you would actually weigh slightly more at the North Pole than at the Equator, as you are physically closer to the Earth's center of gravity!

To navigate this non-spherical world, we use a Geographic Grid System consisting of imaginary lines called Latitudes and Longitudes. Think of these as the Earth's personal address system Physical Geography by PMF IAS, Latitudes and Longitudes, p.240. Mapping these onto a flat surface is tricky—like trying to flatten an orange peel without tearing it Exploring Society: India and Beyond (NCERT Class VI), Locating Places on the Earth, p.12. This is why a globe is the most accurate representation of our planet Exploring Society: India and Beyond (NCERT Class VI), Locating Places on the Earth, p.13.

A crucial distinction to remember is how these lines behave. Parallels of Latitude run east-west and, as the name suggests, are always parallel to each other. However, Meridians of Longitude are quite different. They are semi-circles that connect the North and South Poles. Because they all meet at the poles, they are not parallel. They are spaced widest apart at the Equator (about 111.3 km) and gradually converge until the distance between them becomes zero at the poles Certificate Physical and Human Geography (GC Leong), Longitude, p.11.

Sources: Physical Geography by PMF IAS, Latitudes and Longitudes, p.240-241; Exploring Society: India and Beyond (NCERT Class VI), Locating Places on the Earth, p.12-13; Certificate Physical and Human Geography (GC Leong), The Earth's Crust, p.11

2. Understanding Parallels of Latitude (basic)

To understand the geography of our planet, we first need a way to describe where we are. Imagine the Earth as a giant sphere. Latitude is the angular distance of a point on the Earth's surface, measured in degrees from the center of the Earth Certificate Physical and Human Geography, Chapter 2, p.10. These lines run in an east-west direction and are known as parallels because, unlike the lines of longitude, they are perfectly parallel to one another and never meet.

The most important parallel is the Equator (0°), which sits midway between the North and South Poles. Because the Earth is a sphere, these parallels are actually full circles that wrap around the globe. However, they are not all equal in size. The Equator is the largest circle (often called a Great Circle), and as you move toward the poles, the circles become progressively smaller until they shrink to a single point at the North Pole (90° N) and South Pole (90° S) Exploring Society: India and Beyond (NCERT Class VI), Chapter 1, p.14. This reduction in size is a key geometric property: while the distance between degrees of latitude remains relatively constant (about 111 km per degree), the actual length of the parallel circle decreases as you move away from the Equator Certificate Physical and Human Geography, Chapter 2, p.10.

Beyond the Equator and the Poles, there are four other special parallels that are vital for understanding Earth's climate and seasons Physical Geography by PMF IAS, Latitudes and Longitudes, p.240:

• Tropic of Cancer (23½° N): The northernmost point where the sun can be directly overhead.
• Tropic of Capricorn (23½° S): The southernmost point where the sun can be directly overhead.
• Arctic Circle (66½° N): The boundary of the northern frigid zone.
• Antarctic Circle (66½° S): The boundary of the southern frigid zone.

Sources: Certificate Physical and Human Geography (GC Leong), The Earth's Crust, p.10; Exploring Society: India and Beyond (NCERT Class VI), Locating Places on the Earth, p.14; Physical Geography by PMF IAS, Latitudes and Longitudes, p.240

3. Understanding Meridians of Longitude (intermediate)

Unlike the parallels of latitude that circle the Earth like stacked rings, Meridians of Longitude are imaginary semi-circles that run from the North Pole to the South Pole. Think of them like the segments of an orange; they are widest at the middle and meet at the tips. While latitudes measure how far North or South you are from the Equator, longitudes measure the angular distance east or west of a starting point called the Prime Meridian Physical Geography by PMF IAS, Latitudes and Longitudes, p.242.

A critical geometric property to remember is that all meridians are of equal length. This is a major departure from latitudes, which get smaller as they move toward the poles. However, because meridians must all meet at the North and South Poles, they are not parallel to each other. They are spaced farthest apart at the Equator (approximately 111.3 km) and gradually converge as they move toward the poles, where the distance between them becomes zero Certificate Physical and Human Geography, Chapter 2, p.11.

Historically, the choice of a "starting line" or 0° longitude was a matter of convention. In 1884, the meridian passing through the Royal Astronomical Observatory at Greenwich was chosen as the international Prime Meridian Physical Geography by PMF IAS, Latitudes and Longitudes, p.242. However, Indian astronomical tradition, which dates back centuries, used a prime meridian known as the Madhya Rekhā that passed through Ujjayinī (Ujjain), a great center for ancient science Exploring Society: India and Beyond (NCERT Class VI), Chapter 1, p.17.

Sources: Physical Geography by PMF IAS, Latitudes and Longitudes, p.242, 243, 250; Certificate Physical and Human Geography (GC Leong), Chapter 2: The Earth's Crust, p.11; Exploring Society: India and Beyond (NCERT Class VI), Chapter 1: Locating Places on the Earth, p.17

4. Longitude and Global Time Standards (intermediate)

Unlike parallels of latitude, which circle the Earth horizontally and never touch, meridians of longitude are semi-circles that run from the North Pole to the South Pole. A fundamental geometric property of meridians is that they are not parallel. They are spaced widest apart at the Equator (roughly 111.3 km) and gradually converge as they move toward the poles, where they all meet at a single point GC Leong, Physical and Human Geography, Chapter 2, p.11. While we can draw an infinite number of these lines, they all have equal length, unlike latitudes which get smaller toward the poles.

The most vital function of longitude is determining Local Time. Because the Earth is a sphere (360°) and completes one rotation in 24 hours, we can calculate a precise relationship between distance and time:

• 360° = 24 hours
• 15° = 1 hour (360 divided by 24)
• 1° = 4 minutes (60 minutes divided by 15)

Since the Earth rotates from West to East, places located to the East see the sun earlier and are "ahead" in time, while places to the West see the sun later and are "behind" GC Leong, Physical and Human Geography, Chapter 2, p.12.

To avoid the chaos of every town having its own local time based on the sun's position, countries adopt a Standard Time. This is usually based on a central meridian passing through the country. For instance, Indian Standard Time (IST) is calculated from the 82.5° E meridian (passing near Prayagraj). By multiplying 82.5 by 4 minutes, we get 330 minutes, which means IST is exactly 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT) PMF IAS, Physical Geography, Latitudes and Longitudes, p.245.

Sources: Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.), Chapter 2: The Earth's Crust, p.11-12; Physical Geography by PMF IAS, Latitudes and Longitudes, p.243-245; Exploring Society: India and Beyond, NCERT Class VI (2025), Locating Places on the Earth, p.21

5. Great Circles and Small Circles (exam-level)

To understand the geometry of our planet, we must distinguish between Great Circles and Small Circles. Imagine the Earth as a perfect sphere. If you were to pass a flat plane (like a giant blade) through the sphere such that it passes exactly through the center of the Earth, the resulting intersection on the surface is a Great Circle. This is the largest possible circle that can be drawn on the globe, and it divides the Earth into two equal halves or hemispheres Certificate Physical and Human Geography, The Earth's Crust, p.14.

There are an infinite number of Great Circles that can be drawn. The most famous example is the Equator, which is the only line of latitude that qualifies as a Great Circle Exploring Society: India and Beyond, Locating Places on the Earth, p.14. All other lines of latitude, such as the Tropics of Cancer and Capricorn or the Arctic Circle, are Small Circles because their planes do not pass through the Earth's center; they grow progressively smaller as they move toward the poles Physical Geography by PMF IAS, Latitudes and Longitudes, p.250. Conversely, every meridian of longitude, when combined with its opposite meridian (e.g., 0° and 180°), forms a complete Great Circle.

The practical significance of Great Circles lies in navigation. The shortest distance between any two points on a sphere always lies along the arc of a Great Circle. This is why long-distance flights and shipping routes often appear curved on a flat map—they are following the "Great Circle route" to save time and fuel Certificate Physical and Human Geography, The Earth's Crust, p.15. For instance, the direct route between Vancouver and Yokohama across the North Pacific is a Great Circle path that significantly reduces travel distance compared to following a constant latitude line FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII, Transport and Communication, p.63.

Sources: Certificate Physical and Human Geography, The Earth's Crust, p.14; Certificate Physical and Human Geography, The Earth's Crust, p.15; Exploring Society: India and Beyond, Locating Places on the Earth, p.14; Physical Geography by PMF IAS, Latitudes and Longitudes, p.250; FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII, Transport and Communication, p.63

6. Geometric Properties of the Grid: Parallelism vs. Convergence (exam-level)

When we look at a map or a globe, we see a network of intersecting lines known as the graticule. To master the geometry of this grid, you must understand the fundamental difference in how these lines behave as they move across the Earth's curved surface. While parallels of latitude are exactly what their name suggests—parallel to one another—meridians of longitude follow a very different geometric rule called convergence.

Parallels of latitude are circles drawn around the Earth, centered on the polar axis. Because they run east-west and stay at a constant angular distance from the Equator, they never meet or intersect. The linear distance between two degrees of latitude is relatively constant, averaging about 111 km (69 miles) Physical Geography by PMF IAS, Latitudes and Longitudes, p.240. However, due to the Earth’s slight flattening at the poles (the geoid shape), this distance actually increases very slightly as you move from the Equator (110.57 km) toward the poles (111.7 km) Physical Geography by PMF IAS, Latitudes and Longitudes, p.240. Despite this minor variation in spacing, their defining characteristic remains their parallelism.

In sharp contrast, meridians of longitude are not parallel. They are semi-circles of equal length that run from pole to pole Physical Geography by PMF IAS, Latitudes and Longitudes, p.243. Because all meridians must pass through the North and South Poles, they are spaced widest apart at the Equator and gradually draw closer together as they move toward higher latitudes. This phenomenon is known as convergence. At the Equator, 1° of longitude measures approximately 111.3 km, but this shrinks to 79 km at 45° latitude, and eventually reaches 0 km at the poles, where all meridians finally intersect at a single point Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.11.

To visualize the difference clearly, consider this comparison:

Sources: Physical Geography by PMF IAS, Latitudes and Longitudes, p.240; Physical Geography by PMF IAS, Latitudes and Longitudes, p.243; Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.11

7. Solving the Original PYQ (exam-level)

Now that you have mastered the building blocks of the geographic grid, this question tests your ability to distinguish between the spatial behaviors of Latitudes (Parallels) and Longitudes (Meridians). The fundamental concept to recall is the geometry of a sphere: while parallels are concentric circles that never meet, meridians are semi-circles that must converge at the poles. Think of the segments of an orange; they are widest at the middle and meet at the ends. This visualization immediately helps you identify that meridians cannot be equidistant throughout their length.

Walking through the options, Statements (A), (B), and (D) are factual descriptions of longitudinal properties. Meridians do indeed run north-south, are widest at the Equator, and because they are mathematical lines, an indefinite number can be drawn. However, Statement (C) All meridians are always parallel to one another is the incorrect statement and thus the right answer. The very term "Parallel" is a synonym for lines of latitude, precisely because they maintain a constant distance from one another—a property meridians lack as they move from the 111.3 km spacing at the Equator toward zero at the poles.

UPSC often uses the "Not Correct" format to catch students who rush. The trap here lies in the linguistic confusion between the two systems; by using the word "parallel" in a description of meridians, the examiner is testing if you can mentally separate the two distinct grid patterns. As noted in Certificate Physical and Human Geography, GC Leong, the convergence of meridians is a defining characteristic of our spherical Earth, making it impossible for them to be parallel. Always double-check if a statement about longitudes is actually a hidden description of latitudes.