I've had much the same thought every now and then.
Now:
Take the world with all of that.
Then expand. outwards.
The galaxy - various panets, stars, etc.
Consider the calculation of say one of the gigantic storms on Jupiter, is it? I think.
Consider the effects of solar storms, sun spots, etc etc on our world (and it has among other things, at least one surprising effect, REALLY surprising effect that you wouldn't even think of.)
Consider that it tracks asteroids, collisions, further out from our solar system. Across billions of solar systems, in which any number of them anything could be going on.
Consider how ridiculously VAST the universe is, and consider how ridiculously varied it is.
Here's the thing: games like Oblivion, etc etc are known to have big game worlds (and I know there are much bigger). They are generated by, pretty much, layering the same set of terrain formation (via algorithm) over and over again in various ways. This means that you don't have to calculate each 4bits of memory per tiny little face on the mesh. Calculating all of that individually would probably slow most of the biggest machines down to a crawl, let alone putting AI in there.
The real world has no problem with this and it's got the biggest game worlds beaten by fucking MILES.
Now you've got that attributed to untold numbers of planets, formations, etc
Shit, I could on and on, because there's so much of the universe, and we probably only know about 0.1 percent of anything, but yeah. Moving out from the world in that frame of mind is pretty interesting.