Exploratorium Exhibits - Rental Group A Aeolian Landscape is an exhibit in which a miniature wind-swept desert landscape is recreated by an electric fan and finely ground sand that mimics the process of wind picking up and depositing small particles. Geologists use the term "Aeolian" to refer to land formations that are caused by wind — sand dunes and snow are two common examples. The visitor can change the direction of the fan and notice how the shape of the miniature dunes influences the pattern of the wind, which in turn influences the shape of the dunes. Aeolian Landscape II 451 - Angel Columns is a large-scale example of a figure/ground illusion. Several full-size three-dimensional architectural columns are mounted against a dark wall surface. By looking at the spaces between the columns rather than the columns themselves, it becomes apparent that the spaces actually form human figures. The exhibit is very entertaining, especially as visitors first begin to “see” the figures formed by the background. Angel Columns 134 - Radar Magnet (alias Black Sand) uses a large magnet to attract magnetic sand or steel pellets to form a moldable mound between the pole pieces. Black Sand (Magnet Table) 185 - Catenary Arch is an arch assembled out of numbered blocks. The blocks are laid out on a horizontal board and then tilted into a vertical position. In spite of the fact that the blocks are relatively slender, they can stand due to their catenary shape. Visitors can compare the shape of the arch to the shape of a freely hanging chain and see that the shapes are the same. Graphics, drawings and photographs explain why the catenary is a good configuration for an arch. The mathematical formulae for the catenary are also presented. Catenary Arch 117 - A spinning disc of fabric undulates in complex ways and organizes itself into a pattern of circling waves. The pattern of waves is influenced by the surrounding air currents as well as by visitors who can change the speed of rotation by adjusting a knob. Circling Wave Umbrella 230 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Cloud Rings uses a mist generator and a large rubber membrane with a hole in the middle to launch a ring of vapor up to the ceiling. The ring is generated by the friction between the hole's edge and the vapor flowing through the hole, which forms a swirling pattern known as a vortex. Cloud Rings 176 - Don’t try this at home!! In Color TV and Magnetism, the visitor uses a magnet to manipulate the picture and colors on a color television screen. When you hold the magnet up to the television, its magnetic field distorts the normal flow of electrons to the screen. The distorted electron beams create bands of color which bend and follow the pull of the magnet. Color TV & Magnetism 357 - Eddy Currents consists of a strong electromagnet through which one can drop different discs. Some discs fall freely through the magnetic field while others fall slowly. The magnetic field induces eddy currents in the discs and these currents are magnetic, so although none of the plates are made of magnetic materials, the plates which are electrical conductors are often affected by the magnetic fields. Conductors which have been slotted, so as not to allow the creation of eddy currents, also fall straight through the magnetic field. Eddy Currents 083 - In Falling Magnets, two disc shape metal plates are tilted at a 45 degree angle. Visitors turn the disc and the eddy currents drive the magnets up toward the top of the disc. But then, the gravity force is also pulling it down towards the floor, leaving the magnets floating in orbit. Falling Magnets 626 - Floating in Copper is an elegant expression of a relatively simple phenomenon. Taking advantage of the slowing effects of eddy currents, visitors can make a central magnet literally float in space between two large pieces of copper. Notice that the closer the magnet is to the copper, the slower it moves. As the visitor draws the lower magnet up with the upper magnet, the motion induces eddy currents that serve to slow the lower magnets motion. This effectively sets up a feedback system slow enough for visitors to keep the magnet suspended in mid-air. Floating In Copper 600 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Have you forgotten how the world looks to a small child? Enjoy the fresh perspective provided from the seat of this giant’s chair. Giant Chair 263 - Gravity’s Rainbow launches five small balls into five rubber cups with amazing accuracy. The exhibit employs a steel raceway, whose angle can be adjusted up or down, to vary the distance each ball travels. A catch mechanism holds each ball in place alone the rail; when the catch is released all the balls are launched off the end of the rail. If the rubber cups are set in the proper position they catch each ball which proves that the arc of each ball is predictable. It is possible to move the launch point of each of the five balls and the position of each of the five cups. One can experiment with all elements of the exhibit: the angle of the rail, the number of balls, and the launch and landing points of the balls. Gravity's Rainbow 321 - Hyperbolic Slot displays an aspect of mathematics which is positively arresting. A flat vertical plane made of plastic is mounted on a table top; there is a curve cut into the plastic sheet. Next to the plastic sheet stands a straight stick which is mounted on a vertical rod. The stick, even though it is straight, swings cleanly through the radically curved slot in the plastic. Graphics explain why this is so, and describe the nature of the curve. Hyperbolic Slot 132 - Illusions is a set of common visual illusions displayed in poster formats. The illusions are available individually or in combination. Horse and Cowboy is a puzzle which requires a new way of thinking to find a solution. Old Woman or Young Girl? and Faces or Vases shows how the brain changes the interpretation of the same information. Paris in the Spring and Count the F’s demonstrates how familiarity causes us to overlook details. Illusions Package 153 - Impossible Triangle is a large structure which appears to be an equilateral triangle when viewed from a certain point. Upon closer inspection, visitors discover that this perception is false, and the object does not actually form a triangle. Even given this knowledge, however, it is extremely difficult to view the object from the special vantage point as anything but a triangle. Impossible Triangle 155 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Visitors use magnets to "scoop" up iron particles contained in an oil filled glass tube. Removing the magnets releases the iron into the oil, and the particles swirl in dense clouds. By once again moving the magnets close to the tube, visitors cause the clouds to organize into patterns revealing the magnetic field of the magnets. Magnetic Clouds, aka Magnaflux 435 - This exhibit uses a video camera and a computer to capture the image of the visitor's face and convert it into several of the projections that are used by mapmakers. It's a fun way of using the principles of map making to see how an image with which one is intimately familiar — one's own face — is distorted by the mathematics of map projections. Mercator Your Face 151 - Rollers that are not round, but that are of constant width, are used like roller bearings underneath a flat plate. The visitor moves the plate horizontally along the table. The plate moves smoothly in a horizontal plane while the rollers appear to wobble. Non-Round Rollers 316 - Ten brass weights hang from strings of different lengths. Visitors activate the array of pendulums, which swing back and forth. The timing of each pendulum's motion depends upon its length. Although the weights swing independently, they appear to move together, first in a line, then as a snake. After several periods, the motion becomes seemingly random, and then gradually organizes itself again as the snake pattern returns and the cycle repeats. Pendulum Snake 608 - Reverse Masks is an example of what can happen when vision and experience tell us different things. Two masks of faces are mounted side by side--the right one is concave, the left one convex. When viewing the masks from a distance, the images look two-dimensional or flat. Because we know from experience that faces normally protrude, we assume that both faces are convex. If the visitor walks back and forth in front of the masks, however, the right one seems to follow them. Parallax refers to the rule that more distant objects move less. Since the nose of this mask moves the least, it would seem to indicate a hollow face. Experience overrides this conclusion and the result is perception of a moving face, rather than a hollow one. Reverse Masks 055 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Settling Column demonstrates that sand falling through water forms complex patterns. The visitor turns a tube of sand and blue liquid over to cause the sand to fall. The angle of the tube affects the patterns of flow. As the sand falls, it displaces water at the bottom of the tube causing the fluid to flow upwards. When this up welling encounters more falling sand, much turbulence is created. The more vertically the tube is oriented, the greater the turbulence and the longer the sand takes to settle. Settling Column 163 - Visitors can create unexpected patterns by drawing in the sand on the spinning disk. Shovels, brushes, hands, and fingers are the tools and sand is the medium for making circles, spirals, and heart shaped figures on the variable speed spinning platform. Spinning Blackboard 390 - Visitors stare at the yellow dot for five seconds and then spin the large disc. The colored shapes on the table disappear from view. Even three dimensional objects like keys seem to disappear. The motion of the background is a distraction and causes the eye and brain to temporarily ingore the static images. The phenomenon is referred to as movement induced blindness. Spinning Eraser 664 - In Square Wheel, an ten-inch square wheel rolls smoothly across a very bumpy surface. The bumps are carefully designed, flat catenary curves which exactly match the sides of the wheel in length. These curves also exactly compensate for the changing axle height of the square wheel as it rolls along. The axle of the wheel does not move up and down. Extensive graphics explain the exhibit. Square Wheels 120 - A one-meter-long pendulum performs a strange chaotic dance. Visitors set a pendulum in motion, yet it does not behave like a simple pendulum because it is tipped with a strong magnet. On the table beneath it are three strong magnets oriented to repel the bob. Visitors position the three magnets about on the table to produce different chaotic paths; they also choose the starting position and speed of the pendulum. The sensitive dependence of motion on initial conditions is a property of chaotic systems. The name Strange Attractor was given to this exhibit because due to arrangements of the three table magnets, the pendulum will come to rest at different locations depending on where and how the pendulum is started. Strange Attractor 201 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Subjective Contours allows the visitor to see contours that, in reality, are not there. Two subjective triangles, one that looks whiter than white and the other that looks blacker than black, appear to have distinctive contours. When they are examined closely, they disappear. Subjective Contours 614 - Suspense demonstrates feedback in an eye-catching way: an electromagnet, which is controlled by a photoelectric cell, suspends a metal globe in mid-air. The visitor can block the light and watch the object drop, or place the sphere within the magnet’s grasp and feel as it reaches equilibrium and is suspended. A switch allows the magnet to be turned off. Other objects made from magnetic materials can be suspended. Suspense 174 - Simple wooden blocks can be stacked so that the entire top block extends completely past the end of the bottom block seemingly in dramatic defiance of gravity. To achieve this the visitor makes a vertical stack of 16 blocks. The top block can be slid to the side for half of its length and still remain balanced. The top two blocks can then be slid 1/4 of a block length further, the top three 1/6, and so on down the stack. The displacements of the blocks follows a mathematical series. The mathematical series describing the stacked blocks follows a simple pattern. Take It From the Top, aka Log Blocks 317 - Visitors spin what looks like a large goblet and suddenly two people appear and begin talking in the negative space around the sculpture. Talking in Circles (Faces, Vases) 200 - In an artistic and tactile manner, Tectonic Basin helps demonstrate principles of geology, erosion, chaos and more. Fine grained sand covering a low-frequency vibrating base plate causes the sand to move and settle in unpredictable ways that resemble the shifting sands of a desert. Visitors can spread the sand with their hands and watch the pattern reform within a few seconds. Tectonic Basin 214 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES Exploratorium Exhibits - Rental Group A Tornado uses a large mist generator, fans and a care fully-shaped structure to produce a large tornado. Since the Exploratorium first produced this crowd-pleasing exhibit, it has been duplicated in many museums. Our fourth generation version is intentionally de-tuned so that random air currents can cause both the creation of a tornado and its temporary cessation. This latest Tornado is chaotic and unpredictable much of the time; it wanders off the source of the mist, slips out of the grasp of the shearing winds and presents a delightful and ever-changing image. Tornado 098 - The Turbulent Orb is a large polycarbonate sphere full of special, colored, flow-visualization fluid. The sphere is mounted on top of a pedestal and can be spun in either direction and at different speeds. The fluid in the sphere shows swirls and waves of internal fluid motions produced by the actions of the visitors. The turbulence of the fluid in the sphere is reminiscent of the turbulent flows that occur in planetary atmospheres. This exhibit shows the complexities of fluid motion that can be produced by very simple circumstances. Turbulent Orb 124 - The Turntable disk rotates like a giant compact disk. A supply of small metal disks, rings, and balls, 7-10 cm in diameter, is scattered around the stationary portion of the table top. Visitors try to keep the rings on their edge spinning on the disk. They discover that a ring spinning on edge may stay on the turntable for a while, orbiting the center. A disk laid flat will move in a straight line as soon as it slides off the turntable. Visitors, especially children, love the challenge of getting the disks and rings to stand on edge while moving around the Turntable. Turntable 121 - Prepared on August 23, 2002 EXPLORATORIUM EXHIBIT SERVICES