# Archives September 2012

#### CIRCLES OR SQUARES

Do you see dozens of little white circles on the diagram below? Look a little more closely and you will realize that no circles exist. The circles that you seem to see are illusions, created by your mind. But the question is why do they look like circles instead of little white squares?   HOW  DOES  IT  WORK?   In this instance, disconnected images form an interrupted pattern. The mind in its own way tried to fill in the missing part of the pattern to make it a whole. Where the brain expects the lines of the pattern to connect to a continuous grid, circles appear. Now the question is why circles? This is probably because our eyes and brain are used to natural shapes such as circles rather than geometrical ones such as squares.

#### ILLUSION OF SIZE

Comparing shapes is one of the most amazing of all optical illusions. It is next to impossible not to view the top of table on the left side as longer and thinner than the one kept on the right. All you need to do to convince yourself that the two are the same size is to photocopy the picture. Cut out the table tops. It will fit neatly over both tables in the illustration.   HOW  DOES  IT  WORK?   No one is certain why the illusion works, but scientists feel that the vertical table top appears longer than the horizontal one because its position is reinforced by the vertical orientation of the page. Our brain processes vertical arrays of visual information more easily than those that are horizontal. There are other theories that suggest that vertical sensitivity could actually be the fallout of how light-sensing cells are bunched up at more...

#### A ROTATING ILLUSION

YOU  NEED:
• A large wooden match
• A safety pin
You can try this trick to make a match go through a wire. Just remove the head from a single wooden match stick. Push a safety pin through the match as shown in the illustration. Shut the pin and then hold it in a horizontal position between thumb and forefinger. Now with the tip of a finger of the other hand press down on the end of the matchstick and slide your finger quickly off the end of the match. It would seem as if the match has gone through the safety pin.   HOW DOES IT WORK? What really happens is that the match rotates rapidly around its axis. The movement is so rapid that the eyes cannot follow it. Owls perched on the branch of a tree create a similar illusion. If you happen to walk more...

#### A THREE DIMENSIONAL ILLUSION

YOU  NEED:
• An empty kitchen towel roll
• Scissors
Before discarding the cardboard tube after you have exhausted the roll of toilet paper take a good look. It is difficult to believe that the circumference of the cylindrical tube is longer than its length. But the fact is that it is, longer than the tube's length! Cut the cylinder open along a dotted line as shown in the illustration. The rectangle that you are left with has one side that was the tube's circumference. The other side was the tube's length. Now if you fold one edge of the cardboard over the top of the other edge, you will find out that the circumference is about an inch longer than the length of the erstwhile tube.

#### CHANGING DIRECTIONS OF ROTATION

This is an optical illusion that was created by an expert. And it is truly a unique one. To get a feel of this illusion, focus your attention on the central dot of the illustration then move the page slowly forward and backwards. The inner wheel seems to rotate slightly in a counter clockwise direction as the page moves towards you. It moves clockwise as the page moves away from you. HOW  DOES  IT  WORK?   Psychologists are stumped by this illusion. They do not quite understand why it happens. The explanation is similar to that proposed for the "Flexible Ovals" illusions, mentioned earlier. The brain is transmitted a series of images of the motion of the dot and wheel coming towards and moving away from you. The brain therefore tries to piece them together in what is a logical sequence of motion.

#### IS IT HALF FULL?

YOU  NEED:
• A capped bottle
• Water
• A marker
Here is a riddle. A bottle which is capped seems to be half full of water. Given that the bottle has a long neck, it becomes difficult to gauge whether the water fills more than half the bottle, less than half or exactly half. How will you tell? Well here is how. Mark the level of water on the outside of the bottle keeping the bottle in an upright position. Now turn the bottle upside down. If the water level is above the mark, the bottle is more than half full. If it is below the mark, it is less than half full. It is exactly half if the water level is right on the mark.

#### A DISAPPEARING SMUDGE

Put a hand over an eye. Now stare at the centre of the smudge on the left. After a few seconds the smudge will mysteriously disappear. Now repeat the same exercise with the smudge on the right. The circle prevents the smudge from vanishing. The reason is not understood. HOW DOES IT WORK? If you stare at anything long enough, the light sensing cells of the eyes become tired- They tend to "shut off" temporarily. If you move the eye slightly the cells are refreshed. Your stare wavers slightly between the smudge and the circle surrounding it and your eyes are refreshed and that is what keeps the smudge from disappearing.

#### FINDING THE LONGER PENCIL

YOU NEED :
• Two pencils of the same length but of different colours
Let’s start with the assumption that one of the two pencils used for this trick is red and the other blue. Hold the red pencil vertically and place the blue pencil horizontally on top to make a T, as in the illustration. To onlookers the red pencil will seem  be considerably longer than the blue one. Make the T again, this time with the blue pencil in a vertical position and the red one on top. Now the blue pencil will seem longer than the red one. HOW DOES IT WORK? This simple demonstration is till today largely unexplained. It is felt that the vertical pencil seems longer than the one placed horizontally, because the position is reinforced by the vertical position of the arm and body while the trick more...

YOU  NEED:
• A pencil or a pen
• Paper
Try to write your name on the paper while making a circular motion with one foot. You will not be able to do it.   HOW  DOES  IT  WORK?   The brain which sends messages to the entire body will be unable to direct your foot to go around in circles while telling your hand to write.

#### THE DISAPPEARING PULSE

NOTE : PERFORM  UNDER  ADULT  SUPERVISIONï»¿ YOU  NEED:
• A handkerchief
A bit of secrecy is involved in this one. Tie a few tight knots in a handkerchief and secretly place it under one of your armpits. It will remain concealed by your clothes. Allow a friend to feel the pulse in the arm under which the handkerchief is hidden. Ask him to count up to three and you will stop your pulse. The pulse will stop much to the surprise of your friend. HOW  DOES  IT  WORK?   To stop your pulse, all you have to do is press the sides of your arm against the knotted cloth under the armpit. Pressure is created on the arm's main artery. This lowers the pulse rate to a level which cannot be felt. After some time snap your fingers and end the pressure. The more...

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