My Interpretation of What Happened

I saw this recently, watched it twice, and my sense of the (much bastardized) story, based on my own life experiences and my sometimes morbid imagination, is this:

(Spoiler) There was a child born to the marriage, but the child and the wife had both died, either in childbirth or due to miscarriage. This is signified by the apparition of the wife appearing to rock her empty arms as if holding a child. The ring with an inscription about waiting for who is to come refers to the couple's anticipation of their child's birth. The mockingly-smiling bust of a child in his room represents the lost child.

The angry rattling at the door is the man's helpless rage at his losses and at the emptiness of his life, which after his tragic losses, consisted only of his life as an astronomer--which was also now lost to him, as he had retired the previous year. He lacked even the comfort of any belief in a possible afterlife.

His wife's empty chair at the "home" where she appeared to be warehoused with other silent women indicated that she was never truly there. She existed only in her husband's memory, and when she died, that memory was gone.