How can the observable universe be over 90 billion light-years across when the universe is only 14 billion years old?
In: Physics
Because the universe itself is expanding.
Imagine yourself and a bunch of friends standing together in the middle of a gymnasium. You all run away from each other toward the walls, spreading further apart as you run, but as you’re running the entire room just keeps getting BIGGER. You turn around and look back at your friends and they’re all impossibly far away, as the room has expanded in every direction. They only ran 14 meters in a couple seconds, yet they’re now 45 meters away from the center because the room itself expanded. Your friend on the opposite side from you is now 90 meters away. It sounds crazy, but this is how the math of the universe works out.
Source: https://www.forbes.com/sites/startswithabang/2018/02/23/if-the-universe-is-13-8-billion-years-old-how-can-we-see-46-billion-light-years-away/#662b8ba71303
Edit: as fiiiiine points out, you shouldn’t think of the walls in this example. In fact, imagine that you can’t even see the walls. (It’s a big room, not very well lit.) Really it’s the floor that’s stretching out in every direction. And if one of your friends stayed near the center, they’re still pretty close to center. Meanwhile your furthest friend ended quite far away because of all the floor stretching that happened in between you.
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