* The universe is expanding: The distance between galaxies is constantly increasing. So, even if we could measure its size at a specific moment, it would change shortly after.
* We can't see the whole universe: We can only see a certain distance, called the observable universe. Beyond that, light hasn't had enough time to reach us since the Big Bang.
* The universe might be infinite: Some theories suggest that the universe may extend infinitely.
What we DO know:
* The observable universe is about 93 billion light-years across.
* A light-year is the distance light travels in one year, about 5.88 trillion miles.
So, while we can't give a precise number of miles, we can say the observable universe is incredibly vast.
