The Alaska citizen., 1916-09-18
SCIENCE EXPLAINS
 CURVING OF BALL


 t,e track some time after the train has passed
 This phenomcuon must not be confused with that which makes papers rush in immediately behind train this being caused. of course. by the air rushing in to fill the partial vacuum made by the train. But some distance iii the rear in tcad of this partial vacuum there is breeze blowing directly down tlr track following the train. This breeze certainly cannot take a piece of paper from the side and put il on the track because that would be at right angles 10 its motion
 The reason the paper behaves as it does is that the air pressure at right angles 10 moving stream uf air is less than ordinary atmos- pheric pressure and so the pres sure tl the still air outside the track shoves the paper across. The same thiue happens when a door slams i'll a sudden draught The moving stream of air certainly does not hit the door But the pressure in the moving stream at right angles to its motion is less than that of the still air behind the door, and this still air pressure gradually int D.J stream The stream gives it an acceleration SO that it closes faster and faster shutting with a bang
 If is easier now 10 see why a baseball curyes-or tennis or golf ball The one thing needful is that the ball be rotating as it goes through the air Throwing d ball through still air is the same thing, as far as our argument goes, as having a breeze blow against the ball Remembering this, let us see what happens.
 The ball has a more or less rough surface and there when it rotates.
 
 Thus the rotation of the ball makes little breeze blow around it in thr direction of it's rotation. Now, throw the ball forward and the TO- tatina breeze will be in the same direction a. the main breeze on one tide of the ball while they will be in opposite directions on inc opposite side of the ball.
 Thus the movement of air on one side of the ball is greater than on the other. and consequently the air pressure against the ball at right angles 10 the larger breeze will be less than that on the other side and the ball will have a force on it showing it into the side of the fast est breeze This causes the curve. It is interesting to note just what effect a windy day might have on curves X stiff breeze blowing from the batter to the pitcher will in crease the width of all curves thrown while one blowing in the opposite direction that is. from the pitcher 10 the batter-wilI make the curves very slight If the wind blew in the latter direction just as fast as the pitcher threw the ball there would be no curve at all.
 This is a good thing to remember when you attend the next ball game on a windy day and watch the wind either make or break a pitchers reputation. Of course cross wind will have effects on the ball in its own direction.
 The amount of curving depends upon both the speed of the bal and the rapidity of its rotation. The wonderful curves made by golf anC tennis balls testify to this.
 An easy way to prove the scien tific principle involved is to take a spool place a small sheet of pa per on the bottom and blow througf the spool You will find that, al though the paper will flutter, yot cannot blow it off the end of the spool-for the atmospheric pressure is greater than the pressure a right angles to the air rushing ou from between the spool and tho paper, and so presses the paper in ward.
 A light ball suspended in a jet 0 air works on the same principle.
 The ball is lifted in the air b! the main force of the jet beneatl it, but the air from the jet rushe around the sides of the ball to es cape, thus creating a breeze upwar( all around the ball. Now suppos that the ball tries to fall througl this curtain of moving air on certain side. It will come into COT tact with the regular atmospher pressure which, being greater tha, the pressure against the ball of tn moving air on the opposite side will shove the ball back in wher it belongs
 A VETERAN TWlRLER.
 Fred Beebe, twirler for the Cleve land Maps, is veteran wh