Velikovsky searched for common mention of events within literary records, and in the Ipuwer papyrus he believed he had found a contemporary Egyptian account of the Israelite Exodus. Moreover, he interpreted both accounts as descriptions of a great natural catastrophe. Velikovsky attempted to investigate the physical cause of the Exodus event, and extrapolated backwards and forwards in history from this point, cross-comparing written and mythical records from cultures on every inhabited continent, using them to attempt synchronisms of the historical records, yielding what he believed to be further periodic natural catastrophes that can be global in scale.[citation needed]