The book of mormon states that Lehi and his family left Jerusaelm around 600 B.C, At this time, the world was Geo-centric, Almost everybody believed that the sun went around the earth. Yes, I know there were some eccentrics who thought that the earth may be round before then but they didn't sway the current view until long after they were dead. According to the Bible, Isaiah died in 681 B.C.
Forum: Deconstructing Mormonism