On Quora, I've run into such a sentence where the author describes a hypothetical situation if astronauts wore unsuitable space suits on the Moon:
At about this time, they’d realize that the sides of their body in shadow up till now had grown very cold and those in the sunlight were uncomfortably hot.
I don't understand sequence of tenses here. Does a sentence describing a hypothetical future situation requires past perfect in constructions like this?
Which is correct?
If this occurred, somebody would realize something had happened.
If this occurred, somebody would realize something has happened.
Is past perfect used because the whole clause is shifted to the past in conditional? And what if we are talking about hypothetical past? Do we just add have after would? For example:
If this had occurred, somebody would have realized something had happened.