:The size of the observable universe can be calculated as a sphere with a radius equal to the age of the Universe in light years. First, "age in light years" doesn't make sense, since light years are a unit of length. Second, the above sentence is a crass oversimplification, since it doesn't take into account that the universe has been expanding. This expansion "pulls light along" and therefore the radius of the observable universe is larger than 15 billion light years. --AxelBoldt |