Imagine you tied a rope tightly around the Earth, so it was hugging the surface all the way around. Now imagine you wanted to raise the rope 1 meter off the ground. How much extra length will you need to add to the rope? Though it may seem like you’d need miles of rope, the answer is 6.28 meters. Circumference is proportional to radius, so if you increase radius by 1 unit, you increase circumference by 2π units.
