text: what is coriolis effect?   coriolis showed that an acceleration acts on all bodies moving on the earth’s surface.  if one looks along the earth’s axis from the north pole, the rotation appears counter clock wise. hence in the northern hemisphere, any body moving rectilinearly relative to any inertial system will deviate to the right (as viewed by a terrestrial observer) in the course of its motion, while in the southern hemisphere, it will deviate to left.  this deviation could be large or small, depending on the direction of motion with respect to the axis and on the linear velocity of the motion.  the deviation of the body can take place in the horizontal or vertical plane (with respect to the surface of earth). the coriolis acceleration is directed perpendicular to the earth’s axis; hence, the deviation taking place in the horizontal plane is the greatest at the poles and equal to zero at the equator.  the reverse is true for deviations in the vertical plane.  the deviation of bodies moving in the horizontal plane from their rectilinear path is the reason why the right side banks of rivers are eroded in the northern hemisphere, and the left banks in the southern hemisphere to the left.  all masses flowing into regions of low pressure deviate from the radial direction to the right in the northern hemisphere, (to the left in the southern hemisphere) and form cyclones. thus cyclones in the northern hemisphere stir the air masses counter clockwise, and in the southern hemisphere clockwise.    as a result of the vertical deviation, a falling body does not fall exactly vertically. such a body deviates from east to west.