Determine Where We Are
摘要
Earth is the third of the eight planets in the solar system, in order of distance from the Sun. Mercury and Venus are inner planets, while Mars, Jupiter, Saturn, Uranus, and Neptune are outer planets. Our planet orbits the Sun yearly at an average distance of about 150 million kilometers; this distance is called an astronomical unit. The Earth is roughly a sphere with a radius of 6400 km. How to determine the position of a point on our planet?