noon
`` I use only my chronometer , '' Captain Nemo answered me . `` At noon tomorrow , March 21 , if , after accounting for refraction , the sun 's disk is cut exactly in half by the northern horizon , that will mean I 'm at the South Pole . '' `` Right , '' I said . `` Nevertheless , it is n't mathematically exact proof , because the equinox need n't fall precisely at noon . '' `` No doubt , sir , but the error will be under 100 meters , and that 's close enough for us . Until tomorrow then . '' Captain Nemo went back on board .