I believe I understand that space is constantly expanding “outward” in all directions and this is likely due to an event such as the Big Bang. Can someone explain what space is expanding *into* and how exactly the “space between stuff is also expanding” in the sense that A and B are getting further apart but the space between A and B is also expanding.
Is that simply a function of two objects distancing themselves therefore the space must be getting larger, or is the space actually expanding in between two objects regardless of either object being on either side?
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I think the problem is infinities are just unintuitive. So I’m going to use Hilberts paradox of the grand hotel. Basically, imagine a hotel with infinite rooms. The rooms are numbered 1,2,3,…and so on to infinity. And not only does this hotel have infinite rooms, it currently has infinite guests too. So every room is occupied.
But then a big convention comes to town, a *really* big convention with another set of infinite guests. And they all want to stay at the Hilbert Hotel, even though the infinite rooms are already occupied by infinite guests. That’s ok though, because infinities are weird and the hotel manager knows it. So he just asks all of the guests to move into the room numbered twice as high as their current room. Room 1 to 2, 2 to 4, 3 to 6, etc. Because it’s infinite, every guest still has a room, but now only the even numbered rooms are filled. So our infinite convention attendees can move into the odd numbered rooms and everyone’s happy.
Those guests are kind of like what’s happening in space. We had infinite guests, and we still have infinite guests even after adding new ones. The old guests didn’t ‘expand’ into anywhere, they all just moved further apart from one another and then new guests could move in in between them. And you can keep doing this every time a new convention with infinite people comes around, and the original guests would just keep moving further and further apart from one another. If you do it again, the guest that was in room 2 went to room 4, and would now be in room 8, which is 4 rooms away from the guest originally in room 1 (who is now in room 4). And they’d be 8 (2^3 ) rooms apart if you did it a third time.
With space, it’s not expanding into anything. Every point in space is just moving away from every other point in space. And things aren’t just moving away from some central point. They’re all moving away from everything else. You could go to any galaxy cluster, and over time you’d see every other galaxy cluster in every direction is getting further and further away. And it happens exponentially faster too. Since they’re not just moving away, and space is actually expanding between them, that means the further apart they are, the more space there is that can expand between them and the faster they’ll continue moving apart.
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