How much memory is needed to create an artificial digital universe?

I have this story concept of the world coming to an end from this alien "crystal" that's rapid spreading and will eventually crystallize the majority surface of the world. Before that, humans created this artificial digital universe where humans can hibernate forever in the real world and live in this other world. But how much memory is needed to support this artificial universe? This universe is going to have different laws of physics and function differently.

The world is flat and smaller than the area of earth. You can compare it similar to Minecraft, eventually, you'll reach the border of the land and even farther is blackness of nothing. Light can also be bent and captured and stored. There's no sun, and the moon acts as a light source emitting lights that give off special vibes (like the sun giving vitamin-D) and not making any heat. Matter can be created and destroyed, and living beings are hallowed, but still put on weight. Just like a video character model is hollow.

But how much memory is needed for this world considering there won't be any true outer space and will be smaller than earth, and is capable of holding the minds of other people that will live there?

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