they say that if one black hole has two times more mass than the other black hole it's radius is two times bigger. what if all the stars in the universe were to join to make one big big black hole how big would it be. if a black hole with the mass of the sun is 3 km in radius and two times the mass of the sun is 6 km in radius then what would the black hole with all the stars in the universe be, what would it's radius be. if there are 200 billion stars in a galaxy and there are 200 billion galaxy's in the universe then there are 40,000,000,000,000,000,000,000 stars in the universe. 40,000,000,000,000,000,000,000 times 3 (because a black hole with a mass of a star the size of the sun is 3 km in radius) is 120,000,000,000,000,000,000,000. so this black hole would be 120,000,000,000,000,000,000,000 km in radius this is 20 billion light years in radius (because 1 light year is about 6,000,000,000,000 km) now how is this possible if the universe is only 15 billion years old. how can this black hole be bigger then the universe.???????????????????