Which observation is commonly cited as evidence that Earth is spherical?

Which observation is commonly cited as evidence that Earth is spherical?

• A. The horizon appears flat from any vantage point.
• B. Ships appear to shrink as they move toward the horizon.
• C. The sun rises in the east and sets in the west.
• D. The stars appear to rotate around Polaris.

Answer: (B)

Think about how curvature affects what you can see at a distance. When a ship sails away on a curved surface, the lowest part of the hull dips below the line of sight first, so the hull appears to shrink and disappear before the upper parts like the mast. This hull-first vanishing is a classic cue that the surface you’re looking over curves away, consistent with a spherical Earth. If the Earth were flat, the ship would just get smaller with distance but would remain fully visible (until it’s too far to resolve), not vanish hull-first. The other observations describe effects of Earth's rotation or general perception of the horizon, which do not directly demonstrate spherical shape.

Think about how curvature affects what you can see at a distance. When a ship sails away on a curved surface, the lowest part of the hull dips below the line of sight first, so the hull appears to shrink and disappear before the upper parts like the mast. This hull-first vanishing is a classic cue that the surface you’re looking over curves away, consistent with a spherical Earth. If the Earth were flat, the ship would just get smaller with distance but would remain fully visible (until it’s too far to resolve), not vanish hull-first. The other observations describe effects of Earth's rotation or general perception of the horizon, which do not directly demonstrate spherical shape.