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Show jin wrrrjn11 v . Sunday Science Test Your f t h f Deductive Powers n The W r X r ' xtev' f -- V by Dr. Robert R. Kadesch ! 1 This time exposure shows a black card with vertical sRf cut into it being moved back and forth In front of a television screen. Note the slanting lines. What can you deduce from this, phenomenon? F V VER WIGGLE your finger back and forth in front of your television set? If not, you may be In for a surprise. Hold your hand at arms length with the illuminated picture tube behind. Now wiggle a finger rapidly from side to side. You see what appears to be a number of images of your finger.- But look more closely now. Your finger' will appear strangely elastic, bending in a weird way with each swing. Although theres no great scientific phenomenon Involved here, lets use this situation to test and develop your deduction. Deduction powers-o- f is the process of drawing conclusions from available evidence. Your observations constitute the evidence. What conclusions can be drawn from them regarding the nature of the phenomenon? SOMETIMES a person can arrive at a ridiculous conclusion ip spite of sound deductive reasoning. Take for example the case of the scientist with - Stars above the trained fly. Whenever he commanded the fly to jump, it promptly jumped. But then he removed two of the fly's six legs. He said jump, and the fly jumped as before. Upon removing two more legs, he once more commanded the fly to jump and once more the fly Jumped. Finally he removed legs number five and six. He shouted jump, but the fly did not move. His conclusion:" A fly becomes deaf when all six legs are removed. Curiously enough, his conclusion was sound on' the basis of his limited amount of evidence. Heres hoping you wont make the same kind of mistake. BUT LETS GET back to the antics in front of your television set. Fingers do not make the best objects with which to experiment Instead, cut a sixteenth-incwide slit In a piece of heavy, paper. Now move this rapidly from side to side at arms length in front of the screen. ' finger-wavin- g h What do you see? Tou should see a succession of slit images, but notice that each slit Image is slanted at its top away from the direction of motion of the slit at that particular time. When the slit moves rapldly to theright, the upper portion of the slit image slants to the left When the slit moves to the left, the upper portion of the slit image is seen to slant to the right What conclusions can you draw from this evidence conclusions regarding the nature of the light emanating from the television screen? Before reading further, take time out at this point to make your own deductions. . FIRST OF ALL we may con- clude that the television picture is a flashing picture, with the illumination coming on and turning off rapidly. This must be the reason for seeing multiple fingers or slits. But this In itself does not explain the slant in the slit images or the apparent bending of your finger. If the entire picture were to turn on and off at the same time, the moving slit would not Appear slanted as it moved from one side to the other. It would be seen perfectly straight up and down whenever the screen was illuminated. We must conclude that the Illuminated portion of the television tube-moacross the face of the tube, for then, as the slit Is moved, we see part of the slit when the illumination is located Intone region on the screen, and another part of the slit when the illumination on the screen has moved else--' where. THE OBSERVATIONS ten us that file illumination starts at the top of the tube, moves down, and then jumps back to the top to begin its cycle all over again. Lets, check this tentative conclusion. Suppose the slit is moving to the right When the top of the tube is ' illuminated we will see the top of the slit But as the illumination moves down the tube, lower portions of the slit will be illuminated, but this comes when theglit is farther and farther to the right Hence the -- slant to the slit Moving the slit across to the left the slant direction will be reversed. Provided, then, that television screens do not behave like insects, we have made a proper deduction from the observations. In actuality, the illuminated spot on a television tube moves horizontally across the tube, jumps down a bit, moves across across to the right once more, and repeats this procedure until It gets to the bottom of the tube. Evidence in this experiment reveals the downward motion of the spot but not the motion from left to ves by Sherman Walker Northern Crown Looks Just Like One lOU SHOULD HAVE no difficulty deciding where the Northern Oown (Corona Borealis) got its name. It is one of the constellations whose shape suggests the object for which it is named, and its string of small white stars helps in the illusion.' The brightest star of the figure. Alpha Coronis, is also known as Gemma, the gem of the crown. This should not be confused with Gamma, the third ' letter of the Greek alphabet, which is applied to the third brightest star in each constellation. The crown is not a brilliant constellation, and you wont notice it at first glance; but once found, you will m six-legg- ,, . right ' x fore. It grows on you. The crown is tucked In betwen two large and figures, Bootes and Hercules. Corona Borealis passes almost overhead for most U.S. latitudes. To Identify it, you should look at the sky at 9 pm. standard time at a point a short distance south of the zenith or overhead point. THE NORTHERN CROWN contains some of the most interesting (and puzzling) variable stars in the entire sky. The star known as T Coronae Borealis flared up in 1866 as a nova, changing from a telescopic star to one of second magnitude. It quickly faded and was a ninth magnitude telescopic object until Feb. 8, 1946, when it again flared up to third magnitude for a very short time. R Coronae Borealis Is also very unusual. It remains steadily at sixth magnitude for years! then dims rapidly to 125 magnitude, remains there for weeks, or even years, after which It The Salt Lake TribuneHome Magazi well-know- n |