I ask this question in the context of thinking about infinite ethics. It seems to me that I would need to give up at least one of three beliefs about the universe in order to coherently think that it is infinitely large. They are:

(i) at some past point in time t the universe was finitely large

(ii) since t a finite amount of time has passed

(iii) since t the universe has always expanded with finite speed

To the extent that I continue to believe all three, I would have to be convinced that the universe is finite. Right?

My very layman's understanding of the big bang theory is that it implies (i) and (ii), i.e. that the universe was initially a finite matter-blob and that the universe started to expand a finite amount of time ago (~13 billion years give or take).

So, which of these assumptions are given up by e.g. cosmologists who take seriously that the universe is infinitely large? Or, put another way, which of these assumptions is least likely given our current understanding of physics?

Thanks! The StackExchange discussion is actually very good!