Earth is not a perfect sphere; it has an oblate spheroid shape. This means it is slightly flattened at the poles and bulges at the equator. The planet's rotation causes this bulging effect, making the equatorial diameter about 43 kilometers (27 miles) larger than the polar diameter. The concept of Earth's shape has been studied for centuries, with early thinkers like Aristotle providing evidence for a round Earth. Modern technology, such as satellites and GPS, has allowed scientists to measure and confirm Earth's shape with great precision, enhancing our understanding of its dimensions and gravitational field.