Спереводом . in 1692 halley proposed that the geomagnetic field moved because earth had a magnetic "nucleus or inner globe included within ours, with a fluid medium in between." and that was the first theory of geomagnetism. (read the paper here.) today, we believe that the earth's magnetic field is generated as the inner core, a sphere of solid iron inside the liquid outer core, spins out of phase with the rest of the planet. essentially, halley was right. similarly halley made the first map of the world's winds, setting the baseline for another great field of geophysics, atmospheric dynamics. and he applied newton's new physics to the problem of predicting the tides from the sun and moon's gravity. thus he did his part for the newtonian revolution, which united the physical laws of heaven and earth. along those lines, he suggested in 1694 that comets might strike the earth, a subject he said he would "leave to be discussed by the studious of physical matters." and so we discuss cosmic impacts to this day. ps: halley's first geophysical voyage was the model for scientific research cruises of later years. captain james cook's first voyage in 1769 was made to observe a transit of venus. halley had proposed these observations as the best method of measuring the true distances of the sun and planets, at the time one of science's most vexing problems. the last one was in 2004, the first since 1882; the next one is in 2012.