Topic
Observable Universe
3 questions tagged Observable Universe — spanning every one of the seven Ws.
why
Why is the observable universe limited even though space may be much larger?
We can only see light that has had time to reach us since the beginning of the universe. Because the universe is about 13.8 billion years old and has expanded, the observable universe is much larger than 13.8 billion light-years across.
CosmologyObservable Universe
why
Why is the night sky not filled with light from every star?
The universe is finite in age, so light from the most distant stars has not had enough time to reach us. Also, expansion stretches and dims distant light.
CosmologyObservable universe
what
What is the observable universe?
The observable universe is the part of the universe from which light has had time to reach us since the Big Bang. Its radius is about 46.5 billion light-years.
CosmologyObservable universe