What could be past the 93 bilon light years we know of?
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We don’t know.
Since the universe isn’t infinitely old, there has only been so much time for light to physically travel. This limits the distance you can see, and thus limits you to a sphere of “observable universe” that has been close enough for long enough that light can reach earth.
It’s not really possible from our vantage point to know what’s beyond the “edge” of what we can observe.
if you want talk about the size of the universe, you first have to talk about its shape. the universe is (probably) not flat and that has profound implications for what is “past” the parts we know of. if you start walking on earth (and gain the ability to walk on water, i suppose), and keep going, eventually you will end up back at your starting point. when scientist talk about a curved space time, that is a very similar thing. it doesn’t make sense to talk about what is outside the universe, there is no such place.
So the size might depend on the shape. There are three potential shapes for the universe: flat, curves away from itself, or curves into itself. The first two could be infinite, the last would put a limit on the size of the universe. Scientists have tried to detect whether there is any curvature and so far have not detected any despite extremely accurate measurements. We can therefore state that, based on the accuracy of our measurement, that if the universe curves in on itself it still must be at least 23 trillion light years across, which is about 15 million times larger than the visible universe.
Obviously no one knows what is beyond the current visible universe, and because we are causally disconnected from anything that far away we will *never* know unless some form of extremely faster than light travel is invented. But it would be reasonable to assume that it’s just more galaxies stretching out tens of trillions of light years in every direction.
Anything could be past it. All we can do is learn about the tiny part of the universe that we can see, and then assume our observations are valid anywhere. This is called the *cosmological principle*: the idea that if you zoom out enough, any sufficiently large portion of the universe will basically be similar to any other.
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