Final answer:
The Second Coming refers to an eschatological event in Christian theology, with historic groups like the Mormons and followers of William Miller showing great anticipation for it in the mid-nineteenth century. No exact temporal measure is provided, but the suddenness of change is a common theme in religious texts.
Step-by-step explanation:
The query about the Second Coming and the speed at which we shall all be changed is rooted in eschatological beliefs, particularly within Christian theology. The scriptures mention the event's suddenness, comparing it to the twinkling of an eye, but do not provide a precise temporal quantification. The spiritual and moral preparation, rather than the physical timing, is emphasized in religious teachings. Historical accounts from the mid-nineteenth century reveal that groups like the Mormons, Shakers, and followers of William Miller were deeply invested in the imminent expectation of the Second Coming. Such fervor sometimes led to dramatic actions, such as Miller's group selling their possessions in anticipation for an event that ultimately did not materialize as expected in 1844.