Mercury is the closest planet to the Sun, with an average distance of 35,000,000 miles. It takes light about 3 minutes to travel from the Sun to Mercury. Neptune is the farthest, with an average distance of 2.8 x 109 miles from the Sun. How many times farther from the Sun is Neptune than Mercury? How long does it take light to reach Neptune? Follow the steps to find out. 1. Write the distance from the Sun to Mercury in scientific notation. Include units with your answer.