Welcome to our exploration of the universe's size! This is one of the most profound questions in astronomy. When we look up at the night sky, we're seeing only a tiny fraction of what exists. The universe we can observe has boundaries, but what lies beyond remains a mystery.
The observable universe is the portion of the universe we can actually see from Earth. Light from distant objects takes time to reach us, so we see them as they were in the past. The most distant light we can observe comes from about 46.5 billion light-years away, giving the observable universe a total diameter of approximately 93 billion light-years.
You might wonder why the observable universe is 93 billion light-years across when it's only 13.8 billion years old. The answer lies in cosmic expansion. While light from the most distant galaxies took 13.8 billion years to reach us, those galaxies have been moving away from us due to the expansion of space itself. They are now about 46.5 billion light-years away in each direction, giving us the total diameter of 93 billion light-years.
What lies beyond the observable universe? This is one of the greatest mysteries in cosmology. The entire universe could be much larger than the part we can see, or it might even be infinite in size. There could be countless other regions of space, each with their own galaxies and structures, forever hidden from our view beyond the cosmic horizon. We may never know the true extent of the universe.
To summarize: the observable universe has a diameter of approximately 93 billion light-years and contains everything we can possibly see from Earth. However, the entire universe could be vastly larger, or even infinite in size. This remains one of the greatest unsolved mysteries in cosmology. While we continue to push the boundaries of our observations with better telescopes and technology, there may always be regions of the universe that remain forever beyond our cosmic horizon.