The speaker claims to have two bodies: the small one that walks around, and the Universe, which carries us all. Both are mortal. The personal body will die "by and by," and the Universe will too, only on a far larger and slower scale. The poem then turns to "you" and says we share that second body, so we will all die together with it. The Universe even has a "wailing home," a moan or shriek that the speaker calls our ancestral and future home.
The mood is bleak but strangely awed. The repeated "ashes, ashes, we all fall" borrows the rhythm of a children's rhyme, which makes the end of everything sound both playful and ominous. Art itself "crumples," so nothing is spared. The closing image of a tailspin into a black hole feels like a long, dizzying fall. The speaker seems less panicked than fascinated, treating cosmic death as something we all belong to together.