What did Acts 1:8 mean by “the ends of the earth”?

What did Acts 1:8 mean by “the ends of the earth”? 3-minute lecture clip by Acts scholar Craig Keener.

For 23 free lectures on Acts, see http://faculty.gordon.edu/hu/bi/ted_hildebrandt/DigitalCourses/00_DigitalBiblicalStudiesCourses.html#Acts_Keener; this may be especially valuable to viewers in locations where they cannot attend seminary.