One of the effects of post-traumatic stress disorder, as described in Kurt Vonnegut’s novel Slaughterhouse Five, is coming “unstuck in time”. After surviving the bombing of Dresden, like the book’s author, its hero Billy Pilgrim stops making normal earthly distinctions between past, present and future and begins to experience time as it appears to the inhabitants of the planet Tralfamadore ­– or, perhaps, to an eternal God. Tate Modern’s exhibition “Conflict, Time, Photography” (until 15 March) takes Vonnegut’s idea as the starting point for a long hard look at war photography. Instead of following a chronological order, its record of conflicts from the Crimea to Syria is arranged according to the closeness of the image to the even