Top Puzzle 19: The Two-Hemisphere Earth Puzzle | Puzzles for Interview - Interview Preparation PDF Download

Problem Statement

The Two-Hemisphere Earth Puzzle is a classic interview question that tests a candidate's problem-solving, analytical and creative thinking skills.

Imagine the Earth is divided into two equal hemispheres, Hemisphere A and Hemisphere B. Hemisphere A consists of land area only, and Hemisphere B consists of water area only. Your task is to find a way to travel from any point on the land in Hemisphere A, to any point in the water in Hemisphere B, using the following rules:

1. You can only travel in a straight line.

2. You can only travel across the boundary between Hemisphere A and Hemisphere B once.

3. You cannot travel in a straight line that goes through either the North Pole or the South Pole.

4. You must stay on the Earth's surface at all times during the journey.

Can you find a solution to this puzzle that meets all the given rules?

Solution

The solution to this puzzle is quite simple once you visualize the problem correctly.

Since Hemisphere A consists of land area only, and Hemisphere B consists of water area only, the boundary between the two hemispheres will be a continuous line that goes around the Earth. This line is similar to the equator, but it separates the land and water hemispheres instead of the Northern and Southern hemispheres.

To travel from a point on the land in Hemisphere A to a point in the water in Hemisphere B, simply travel in a straight line perpendicular to the boundary between the two hemispheres. This straight line will start from the land point in Hemisphere A, cross the boundary between Hemisphere A and Hemisphere B exactly once, and then end at a water point in Hemisphere B.

Since the straight line is perpendicular to the boundary, it will not pass through either the North Pole or the South Pole, fulfilling Rule 3. The line also stays on the Earth's surface at all times, meeting Rule 4. Thus, this solution follows all the given rules for the Two-Hemisphere Earth Puzzle.