In modern physics, at both the macro and micro levels, such concepts as simultaneity and cause and effect are not defined (or even undefinable). Its like asking, "What were the plays Shakespeare would have written if he hadn't died so young?" Perhaps your question may fall into the category of "irrelevant".

It may simply not make any sense to ask the size of the universe, just as it makes no sense to ask what was there before the universe happened, or what is beyond the edge of the cosmos. These statements are linguistically correct, but may have no physical referent. The sort of questions physicists deal with now are so counter-intuitive and abstract that they are only accessible through impenetrable mathematics. At best, they simply cannot be understood by those who have not mastered the math; at worst, they may simply be beyond human capacity to understand at all. How can we think of science as an objective pursuit when it is so intimately entangled with the concepts of perception and consciousness? We all experience the universe we perceive, not the one that actually exists.

On the other hand, whatever the universe REALLY is, we can only deal with the parts we can make sense of. So our minds construct models and shortcuts that allow us to function and survive regardless of what is actually going on "out there". In other words, we can't understand the real universe, so we have to devise one that we CAN understand in order just to get along. This universe, our internal model, is the one we have to deal with on a day-to-day basis, so it is (for all practical purposes) just as real and important as actual reality.

I've been getting into the Tokyo Olympics on the telly, and I enjoy watching, and highly admire, the skill and dedication of the athletes. These kids are doing remarkable things with their bodies, completely without any true understanding whatsoever of the physical dynamics of motion in a gravitational field or of the molecular biology of the human body. They simply do not need to know what is going on at the space-time or quantum levels. Likewise, we don't need to understand (or maybe we just can't) what is happening at cosmological scales. Our minds are still capable of coming up with the strategies we need to deal with it. Not only do we know what what we need to know, we decide just what it is we need to know.

At the risk of going all Zen on you, remember: You don't have to be black or Christian to enjoy Gospel music.