s=t Usage note Although some usage guides insist that only farther should be used for physical distance ( We walked farther than we planned ), farther and further have been used interchangeably throughout much of their histories. However, only further is used in the adverbial sense “moreover” ( Further, you hurt my feelings ) and in the adjectival senses “more extended” ( no further comment ) and “additional” ( Further bulletins came in ). You have the idea of physical distance here, so either one is OK.
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