Please help me understand this. The age of the universe is given as being about 13.8 billion years. The size of the universe is estimated to be 93 billion light years ( https://en.m.wikipedia.org/wiki/Universe) Since the oldest light to reach us comes from 13.8 light years away, why do we estimate that the universe has a radius of 46+ billion light years instead of 13.8 ? I know that the universe expanded faster than the speed of light but why do we think that and why 93 billion light years? Thank you.