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The Floating Finger Sausage
Discrepant Events Research
LEGO Timeline
LEGO Story
A LEGO Lesson
Evaporation Activity
Condensation Activity
Raindrop Activity
Mass/Weight Misconception
Dissolving Misconception
Living Things Misconception
Air/Oxygen Misconception
Planetary Orbit Misconception
Surface Tension Demonstration
Air Pressure Paradox
Iodine/Starch Paradox
Air Pressure Paradox
Daytime Star Paradox
Mouse Simile
Rabbit Simile
Giraffe Simile
Bear Simile
Air Speed/Flight Demonstration
Cohesion Demonstration
Optical Illusion Demonstration
Lightning Demonstration
Twinkling Star Demonstration
Density Paradox

Science Area:  Life Science
Content:  Creating Illusions/Depth Perceptions

Floating Fingertip



Two Fingers



Touch index fingers together.

Stretch your arms out in front of you with your index fingers still touching at eye level.

Keep both eyes open.

Look straight ahead and focus on a far point.

Slowly bring your touching index fingers closer in toward the bridge of your nose

What do you see? (It will appear that you grew a sausage between your index finger tips).



How does this happen?

What might happen if you close one eye?





Even though your eyes are focused on a far point, we still see objects that are closer to the eyes.  This is the reason why we see only a piece of the finger.  What ever image overlaps is seen more clearly.  Optical illusions are the result of our brains folllowing reasoning to what would apprear to be a logical conclusion.  The image of the two eye retinas have to correspond.  Our visual system attempts to do the best it can, but sometimes it is wrong.


Source:  Levenson, Elaine. Teaching Children About Life and Earth Sciences. TAB Books (Division of McGraw Hill, Inc.). New York.  1994.  p. 37.