Page "Alternate history" Paragraph 3

In writing an alternate history, the author makes the conscious choice to change something in our past.

According to Steven H Silver, alternate history requires three things: 1 ) the story must have a point of divergence from the history of our world prior to the time at which the author is writing, 2 ) a change that would alter history as it is known, and 3 ) an examination of the ramifications of that change.