When we see a galaxy 8 billion light-years away we are looking how many years into the past?
Assignment 1 1. The moon is about 240,000 mi away. What is this in scientific notation? 2. The planets shine because they [produce their own energy, reflect sunlight]. 3. What is meant by the AU? 4. The light-year is a unit of [time, distance]. 5. How many years does it take light from Proxima Centauri […]