Explorations to Accompany Exhibit Set 5
by Paul Doherty
A figure ground illusion. It is amazing to watch visitors walk by these columns, then see one of them do a double take as they see the angels. The angels are from the sculptures on the outside of the Palace of Fine Arts, the home of the Exploratorium. We were originally going to name this exhibit "Tween Angels."
You can collect black sand if you live downstream from a mountain range with granite rocks. Turn a ziploc bag inside out. Then place the largest magnet you can get inside the bag. Push the magnet through the sand at your local rivershore or beach. Black sand made of magnetite will be magnetically attracted to the outside of the bag. Turn the bag inside out once again and you have a clean magnet and a bag full of magnetic sand. A fraction of this magnetic sand is iron and comes from meteorites.
Blind Spot Snack
Advanced Blind Spot, The blind spot is not left empty by the eye and brain, sometimes it is filled in with a pattern.
Blind Spot Exploration, Put a small, dim lightbulb into your blindspot and it will vanish.
Bottle Still Life
Cheshire Cat Snack
Circles of Magnetism
Circles of Magnetism Snack
Color TV and Magnetism
Use a junk color television. Turn it on and tune it to a station. Place a large magnet near the screen and notice how the picture and its colors are distorted. Inside the cathode ray tube of the television picture tube electrons are shot from a gun at one end of the tube to the screen at the other end. The moving electrons are deflected by the magnetic field of the magnet and so do not hit the screen where they are supposed to. Remove the magnet and notice that the colors remain distorted. The magnet has magnetized the nickel "shadow mask" inside the color television. If this happens to a non-junk television a technician can use a degaussing coil to demagnetize the shadow mask and restore the color. Degaussing coils cost under $20. Many color televisions have a built in degaussing coil and automatically degauss themselves every time they are turned on.
Colored Words Stroop Test
Try naming the colors of the words when the test
is held upside down, or rotated 90 degrees.
Try naming the colors when the words are viewed in a mirror.
Try naming the colors when the words for the colors are in a foreign language.
When these strong neodymium magnets accelerate downward under gravity they move next to an aluminum plate. When magnets move next to an electrical conductor like aluminum they create electric currents called eddy currents in the conductor. These electrical currents make the conductor into an electromagnet. The electromagnet always opposes the motion of the falling magnets. The magnets also all have the same magnetic pole facing outward toward the visitor, thus, they all repel each other. This causes them to create interesting patterns of motion as they fall.
Eddy Currents Snack
Far Out Corners
Far out Corners Snack
Floating in Copper
Floating in Copper Snack
Hoop Nightmares Snack in "Human Body Explorations" Book
Magnetic Cloud a.k.a. Magnaflux
Magnetic fields are "trapped" inside of iron. Crack the iron and the field leaks out at the crack. Sprinkle finely ground of magnetic powder called magnaflux powder on a cracked iron engine block, put a huge electric current through the iron of the block to make it into a magnet, and the magnaflux powder will gather where the magnetic field leaks out of the block, i.e. at the crack. In this exhibit the magnaflux powder shows the magnetic field outside of two strong neodymium magnets.
Motor Effect Snack, This quintessential discovery of the 19'th century changed the way we lived in the 20'th century by making possible the invention of the electric motor.
Paris in the Spring
Can you pass this tricky reading test? Read the following aloud.
How did you do? Did you read two identical words in a row? Look again.
Perspective Window Snack in "Square Wheels" book
Similar triangles lead to the mathematics behind perspective drawing.
Reach For Meaning
Size and Distance
Size and Distance Snack
You perception of the size of an object depends on your perception of its distance:
Size Constancy Exploration
This effect leads to an explanation of why the full moon looks large to a human viewer when it rises or sets, but is found on photographs to be exactly the same size as a moon overhead when photographed. The apparent large size of the moon is a size-distance illusion.
Strange Attractor Snack
Stripped Down Motor
Stripped Down Motor Snack
3-D shadows Snack in "Square Wheels" book
Two as One
Vanna (about face)
Scientific Explorations with Paul Doherty
13 May 2003