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A Little Atmosphere
Use a little bit of math to make a bonus accessory for your globe of the earth—an atmosphere, to scale.
A Splash of Color
What color is water? Look through a clear tube to find out.
Afterimage
After looking at something bright, such as a lamp or a camera flash, you may continue to see an image of that object when you look away. This lingering visual impression is called an afterimage.
Agar Cell Diffusion
Use cubes of agar to model how diffusion occurs in cells. By observing cubes of different sizes, you can discover why larger cells might need extra help to transport materials.
Aluminum-Air Battery
Use aluminum foil, salt water, and activated charcoal to construct a simple battery strong enough to power a small motor or light.
Ambiguous Cube
“Ambiguous” objects provide visual input that your brain can interpret in more than one way. With this Snack, you can make an ambiguous three-dimensional cube from drinking straws.
Ames Chair
Short pieces of chenille stem inside a box look like a random jumble, but when viewed in the proper perspective, and without normal depth perception, they look like a chair!
Anti-Gravity Mirror
A reflection of your right side can appear to be your left side. Try this activity and you'll appear to perform many gravity-defying stunts.
Anti-Sound Spring
In this simple exploration, a coiled phone cord slows the motion of a wave so you can see how a single pulse travels and what happens when two traveling wave pulses meet in the middle.
Antibody Attack
Explore how your immune system seeks out and disables pathogens, and prepares your body for future attacks.
Aporrea una pila
Una simple pila de bloques de madera demuestra que un objeto en reposo permanecerá en reposo al menos que una fuerza haga que se mueva.
Arpa de cabeza
Envuelve una cuerda alrededor de tu cabeza y púlsala para hacer música.
Avalanche
What starts out as a cascade of well-mixed granular materials sorts itself into alternating layers of salt and sand.
Backyard Bug Bonanza
You may think that hunting for insects requires a trip to the Amazon, but they’re everywhere on our planet. Where do you think you’ll find the greatest diversity of insects in your neighborhood?
Bacteria Culture Club
Yogurt is the byproduct of hungry bacteria that digest the lactose in milk. You can make more yogurt just by feeding the bacteria more milk.
Bacteriopolis
Make a living artwork that reveals the colorful microorganisms that live in the soil underfoot.
Balancing Ball
A ball stably levitated on an invisible stream of air is a dramatic sight. Try to pull the ball out of the air stream—you can feel a force pulling it back in.
Balancing Stick
The distribution of the mass of an object determines the position of its center of gravity, its angular momentum, and your ability to balance it.
Bean-Counter Evolution
In this simulation game, teams of predators equipped with genetically different “mouths” hunt for “prey.” Over time, the fittest among the predators and prey dominate the population, modeling the process of natural selection.
Bee Hummer
When you spin it around, this toy sounds like a swarm of buzzing bees.
Benham's Disk
Rotate this black-and-white pattern at the right speed, and the pattern appears to contain colored rings. You see color because different color receptors in your eyes respond at different rates.
Bernoulli Levitator
The Bernoulli principle explains how atomizers work and why windows are sometimes sucked out of their frames as two trains rush past each other. Choose from two versions of this Snack—small or large.
Bicycle Wheel Gyro
A spinning bicycle wheel resists efforts to tilt it and point the axle in a new direction. Any rapidly spinning wheel exhibits this gyroscopic property—you can use this tendency to take yourself for a spin.
Bird in a Cage
You see color when receptor cells in your eye’s retina are stimulated by light. If one of these adapts to a stimulus because of long exposure, it responds less strongly—changing the colors you see!
Blind Spot
The eye’s retina receives and reacts to incoming light and sends signals to the brain, allowing you to see. One part of the retina, however, doesn't give you visual information—this is your eye’s “blind spot.”
Blue Sky
When sunlight travels through the atmosphere, blue light scatters more than other colors, leaving a yellowish hue to the transmitted light. The scattered light makes the sky blue; the transmitted light makes the sunset red.
Bone Stress
When certain plastics are placed between two pieces of polarizing material, their stress patterns become dramatically visible in a brightly colored display. A stressed plastic object can be used to illustrate stresses found in bones.
Bottle Blast Off
Experiment with rocket designs and a PVC launcher to discover how high—and how far—you can make your rockets go.
Bottle Racer
In this modern adaptation of a classic toy—the spool racer—a plastic water bottle is propelled by energy stored in a wound-up rubber band.
Boyle-ing Water
The temperature at which water boils depends on pressure. You can demonstrate this by dramatically lowering the pressure in a water-filled plastic syringe at room temperature.
Breakfast Proteins
Model the central dogma of molecular biology by constructing a colorful chain using a simple code (and some delicious cereal).
Bronx-Cheer Bulb
Some light sources may appear to wiggle and flash when you give them the raspberry, but the only thing wiggling is you.
Bubble Suspension
This beautiful investigation illustrates the principles of buoyancy and semipermeability.
Bubble Tray
Bubbles are fascinating. What gives them their shape? What makes them break or last? What causes the colors and patterns in the soap film, and why do they change?
CD Spectroscope
Turn an old CD into a spectroscope to analyze light—you may be surprised by what you see.
Cell Phone Miniscope
Open your eyes to the amazing world of the ultra-tiny when you convert your cell phone into a portable, picture-taking Miniscope using a simple plastic lens from a laser pointer.
Cellular Soap Opera
Use soap film to model a cell membrane.
Center of Gravity
Here’s an easy way to find the center of gravity of a long, thin object, even if the object’s weight is unevenly distributed.
Charge and Carry
Tired of electrostatic experiments that just won’t work? This experiment will produce a spark that you can feel, see, and hear.
Cheshire Cat
Under most circumstances, both of your eyes receive fairly similar views of the world around you. You fuse these views into a single three-dimensional picture. But what happens when your eyes receive different images?
Circles of Magnetism
Create a magnetic field that is stronger than Earth's field by using electric currents, and a compass needle will orient itself parallel to the new field.
Circles or Ovals?
You have two eyes, yet you see only one image of your environment. If your eyes receive conflicting information, what does your brain do?
Circuit Workbench
Build a simple circuit board and easily connect small holiday lights in a variety of ways to learn some of the characteristics of series and parallel circuits.
Coffee-Can Cuíca
Build a homemade cuíca (“kwee-ka”)—a musical instrument that originated in Africa but is commonly played during Carnival festivities in Brazil.
Cold Metal
Your hand isn't always a good thermometer. When you touch a variety of materials, some will seem warmer or colder than others, even when they're at the same temperature.
Color Contrast
In this investigation, you'll discover how colors seem to change when you place them against different-colored backgrounds. You need to consider this phenomenon when you pick out colors for carpeting or walls or when you're painting a picture.
Color Me Human
Skin—we’ve all got it, and it comes in a range of colors and shades. Find a few partners and explore the question of nature vs. nurture by comparing the skin on different parts of your body.
Color Table
A brightly colored picture takes on a whole new look when you view it through a colored filter, which transmits some colors and absorbs others. Using a colored filter, you can even decode secret messages.
Colored Shadows
Learn about human color perception by using colored lights to make additive color mixtures.
Condiment Diver
Changes in fluid pressure affect the buoyancy of a Cartesian diver made from a condiment packet. The diver floats, sinks, or hovers in response to pressure changes.
Conductivity Meter
This simple and portable device lets you test the conductivity of liquids anywhere, any time.
Convección en un molde de aluminio
Visualiza el movimiento de los fluidos de las celdas de convección. Para esta actividad, todo lo que necesitas es agua jabonosa, una fuente de calor y un poco de colorante para alimentos; el efecto causado por los fluidos que suben y bajan es espectacular.
Convection Currents
Here's a simple and visually appealing way to show convection currents in water. Warmer water rising through cooler water bends light, allowing you to project its motion onto a screen.
Convection Detection
A bag of colored water inside a CD case shows the mesmerizing movement of a fluid undergoing convection.
Conversation Piece
Sound energy spreads out as it travels away from a source, but a balloon filled with carbon dioxide gas can focus sound, acting like a lens to create a loud spot.
Cool Hot Rod
Changes in temperature cause objects to expand or contract. Try this experiment and directly observe the expansion and contraction of a metal tube.
Corner Reflector
Two hinged mirrors create a kaleidoscope that shows multiple images of an object. When you set the hinged mirrors on top of a third mirror, you create a reflector that always sends light back in the direction from which it came.
Corte de pi
El hilo y las tijeras son todo lo que necesitas para encontrar el número pi a tu alrededor.
Coupled Resonant Pendulums
Two pendulums suspended from a common support will swing back and forth in intriguing patterns if the support allows the motion of one pendulum to influence the motion of the other.
Coupled Resonant Pendulums 2
By taking advantage of resonance, you can cause two pendulums to swing in identical cycles.
Critical Angle
A transparent material, such as glass or water, can actually reflect light better than any mirror. All you have to do is look at it from the proper angle.
Critter Comparison
Take an inventory of a variety of traits in a group of living specimens, and discover that even small inherited differences have the potential to impact a population’s long-term survival and evolution.
Cup Speaker
Wind up a coil of wire, attach it to the bottom of a paper cup, hold a magnet nearby, and listen to the radio! You’ve made your own speaker.
Curie Point
A piece of iron ordinarily will be attracted to a magnet, but when you heat the iron to a high enough temperature (called the Curie point), it loses its ability to be magnetized. Heat energy scrambles the iron atoms so they can’t line up and create a magnetic field—this Snack is a simple demonstration of this effect.
Curveball Demonstrator
Throw ‘em a curve—and demonstrate the Magnus effect—by launching cups with rubber bands.
Cutting Pi
String and scissors are all you need to find pi all around you.
Cylindrical Mirror
A flat mirror will always reflect an image that's right side up and reversed right to left. A cylindrical mirror can produce images that are flipped upside down and images that are not reversed. The image you see in a cylindrical mirror depends on the orientation of the mirror and the distance between you and the mirror.
Deep Blue
Use photographs and colored light bulbs to see how changing light conditions affect the apparent color of deep-sea organisms.
Depth Spinner
When you watch a continuously rotating spiral, the motion detectors in your eyes become adapted to that motion. Then, when you look away, the world seems to move toward or away from you.
Designer Ears
See how differently shaped ears affect your hearing.
Diablillo cartesiano de condimento
Los cambios de presión que ejercen los líquidos afectan la flotabilidad de un diablillo cartesiano hecho con un paquete de condimentos. El diablillo flota, se hunde o se desplaza en respuesta a los cambios de presión.
Diffraction
You can easily demonstrate diffraction using a candle or a small bright flashlight bulb and a slit made with two pencils. This bending is called diffraction.
Dipping Bird
A dipping bird is an example of a heat engine. It converts a difference in temperature between its head (cooled by evaporation) and its bottom (at room temperature) into cyclical motion.
Disappearing Act
Some animals blend in with their surroundings so well that they’re nearly impossible to see until they move. Compare what you see when a camouflaged figure remains still to when the figure is moving.
Disappearing Glass Rods
Glass objects are visible because they reflect some of the light that shines on them and bend or refract the light that shines through them. If you eliminate reflection from and refraction by a glass object, you can make that object disappear.
Distortion Goggles
Distort your vision with special goggles and see what your brain learns.
Domino Effect
Your nervous system transmits information as electrical impulses that move through the long bodies of nerve cells. In this Snack, falling dominoes simulate many aspects of the process.
Doppler Effect
When a sound source moves in relation to you, its pitch changes. From this, you can determine whether the source is moving toward or away from you, and you can estimate how fast it’s going.
Downhill Race
Two objects with the same shape and the same mass may behave differently when they roll down a hill. A cylinder with a heavy hub accelerates more quickly than a cylinder with a heavy rim.
Drawing Board
A marking pen remains stationary and a platform swings beneath the pen, acting as a pendulum. As the platform swings, the pen marks a sheet of paper that is fastened to the platform, generating beautiful, repetitive patterns.
Drip Chamber
Make a captivating moving artwork by illuminating a thick, clear liquid with a cell phone flashlight.
Duck Into Kaleidoscope
With this mirrored kaleidoscope, you can create hundreds of images of whatever you place inside. The basic structure is a triangle, but mirror tiles can be formed into other shapes and angles as well.
Dye Like a Natural
Stain your clothes on purpose, bringing the colors of nature to your own wardrobe: use colorful molecules found in natural organisms and objects to dye fabrics or other textiles.
Ear Sort
Survey a wide variety of earlobes and decide for yourself if sorting their shapes into two groups—“free” or “attached”— is as simple as it sounds.
Earth and Moon
Use different-sized spheres to explore the relative sizes of the earth and moon and the distances between them.
Eddy Currents
When a magnet is dropped down a metallic tube, the changing magnetic field created by the falling magnet pushes electrons around in circular, eddy-like currents. These eddy currents have their own magnetic field that opposes the fall of the magnet. The magnet falls dramatically slower than it does in ordinary free fall inside a nonmetallic tube.
Electric Current Model
Model the motion of electrons through a wire by pushing on a circle of small magnets around the rim of a large magnet.
Electrical Etching
The chlorine in saltwater can corrode many metals, including stainless steel, leaving them pitted and rough. Speed along the process with electricity, and rapidly etch a pattern onto stainless steel.
Electrical Fleas
Static electricity makes the sparks when you comb your hair on a cold day, and it makes balloons stick to the wall at a birthday party. Here, static electricity makes electric “fleas” jump up and down.
Electromagnetic Antigravity
A current-carrying wire changes the weight of mounted magnets resting on an electronic scale—simple but dramatic proof of the Lorentz force, the phenomenon at work in most electric motors.
Electroscope
By suspending pieces of tape from a straw, you can build an electroscope—a device that detects electrical charge.
Everyone Is You and Me
Looking for Everyone Is You and Me? Your Father's Nose is an alternate Snack that relates to the same general principles.
Eyedropper Hydrometer
Construct a simple hydrometer that you can use to compare the densities of different solutions.
Fading Dot
A fuzzy-colored dot that has no distinct edges seems to disappear. As you stare at the dot, its color appears to blend with the colors surrounding it.
Falling Feather
Prove to yourself that Galileo was right—in a vacuum, two different weights will fall at the same acceleration.
Falling for Gravity
Calculate the acceleration of gravity using simple materials, a cell phone, and a computer to record, watch, and analyze the motion of a dropped object.
Falling Rhythm
Space weights along a string so they make a regular rhythm of beats when they strike the ground.
Fan Cart
Build a low-friction cart and explore Newton’s third law.
Far-Out Corners
At first glance you might see a bunch of boxes here, but, in fact, there are no boxes at all. A closer look reveals you're looking at a cluster of corners lit from below.
Feeling Pressured
Feel changes in atmospheric pressure by stepping into an extra large garbage bag—a breathtaking experience.
Flash Pickling
Infuse vegetables with a tasty brine—instantly—using a syringe.
Floaters
Gazing at a blue sky, you may see shapes drifting through your field of view—blobs and squiggles called floaters. Why do they jump away when you try to get a better look?
Flower Dissection
Dissect a flower to explore the form and function of plant reproductive structures.
Flying Tinsel
By experimenting with positive and negative charges, you can suspend tinsel in the air. (No need to reveal it's just electrostatic repulsion.)
Fog Chamber
In the atmosphere, clouds usually form when moist air cools as it rises to higher altitudes. You can create the same effect by rapidly expanding the air in a jar.
Follow the Carbon
Model the carbon cycle and its principal reservoirs and flow rates using rice.
Fractal Patterns
Lightning bolts, river deltas, tree branches, and coastlines are all examples of patterns in nature called fractals. In this Snack you get a striking hands-on introduction to fractal patterns and how they are formed.
Fruit Dissection
Investigate the shared structures of fruits, and explore the traces of their flowery pasts.
Gas Model
A fun way to visualize gas molecules constantly in motion, pinging and ponging against each other and the walls of whatever container they're in.
Gassy Eggs
Discover properties of gases and learn about the anatomy of an egg by observing different boiled eggs.
Gel Electrophoresis
Simulate the process of manipulating DNA by using electricity to separate colored dyes.
Geyser
Natural geysers form when underground chambers fill with water and are heated geothermally. When the water is heated to its boiling point, the geyser erupts, spewing its contents—and the cycle starts again.
Giant Lens
A large hanging lens creates upside-down images of distant objects and right-side-up images of nearby objects. You can locate the upside-down images by using a piece of white paper as a screen. The right-side-up images are harder to find.
Giant Sieve Sorter
Create a series of boundaries that keep some things out while letting other things through.
Give and Take
Use temperature-sensitive liquid crystal to monitor temperature changes and show that dark-colored materials absorb and re-emit the energy contained in light more readily than light-colored materials.
Globos de hielo
Haz un experimento con un globo de agua congelada y aprende sobre la química del agua, los cambios de fase y la densidad.
Glow Up
Different kinds of light can be used to study life.
Glue-Stick Sunset
Model the scattering of light by the atmosphere—which makes our sky appear blue and our sunsets red—by shining a flashlight through clear hot-glue sticks.
Gray Step
Two slightly different shades of the same color may look different when there’s a sharp boundary between them. But if the boundary is obscured, the two shades may be indistinguishable.
Groovy Sounds
In this classic activity, make a record player out of simple materials and listen to your favorite vinyl LP—no outlet required.
Hand Battery
When you place your hands on metal plates, you and the plates form a battery.
Hand-Held Heat Engine
Can you get the liquid in a so-called "hand boiler" to travel up and then back down again without turning it over?
Handy Measuring Tool
Many of the numbers we use in science have never been measured directly; we only know them from indirect measurements. How far is it to the sun? What is the diameter of Saturn’s rings? You can use nonstandard measurements and simple ratios for estimating sizes or distances.
Having a Gas with Water
Build a simple electrolysis device using a 9-volt battery wrapped in oil-based modeling clay, trap the two gases produced, and end with a bang as you test their composition.
Head Harp
Wrap a string around your head and pluck it to play music.
Height Sight
Build an inclinometer, a tool that can measure the height of a distant object, no matter how far away it is.
Holding Charge
Use static electricity to stick a straw to the palm of your hand, a window, a door, a wall—or just about anywhere.
Hole in Your Hand
You have two eyes, yet you see only one image of your environment. If your eyes receive conflicting information, what does your brain do?
Hot Spot
Though you can’t see infrared radiation light with your eyes, you can focus it with a mirror or a lens and feel the warmth it produces. Try this Snack and you'll also learn how parabolic shapes concentrate energy.
How Many HeLa?
Dividing cells expand exponentially.
Hydraulic Arm
When you push the plunger on a syringe, water is forced into a second syringe, extending its plunger and lifting a mechanical arm. The process illustrates aspects of fluid pressure, force, mechanical work, and biomechanics.
Hydraulic Battle
Two different-sized syringes full of water are connected together. Push on one and feel the force—multiplied—in the other.
Hyperbolic Slot
If you see a straight rod and a curved slot, common sense says the rod can't possibly fit through the slot. But if the rod is angled and rotated through space and the slot is the exact right shape, it will pass through.
Ice Balloons
Have a ball experimenting with a frozen water balloon—and learn about water chemistry, phase changes, and density.
Indicating Electrolysis
Break up water into hydrogen and oxygen gas with a simple electrolysis device, and use an acid-base indicator and a magnet to create groovy swirls of color.
Infrared Remote
Investigate infrared electromagnetic radiation by using your television remote control as a source and a digital camera as a detector.
Inverse-Square Law
We all know that the farther away we get, the dimmer a light will look. The question of how much dimmer it looks was answered a long time ago. Here’s an easy way to repeat that discovery.
Inverted Bottles
Investigate convection by using food coloring and water at different temperatures.
Jacques Cousteau in Seashells
Seeing is a cooperative effort involving your eyes and your brain. Your eyes may perceive a group of dots, but it’s your brain that has to decide whether or not the dots form a pattern that means something.
Klutz-Proof Density Column
This density column always returns to its original three layers—no matter how many times you shake it up.
Laser Jello
Gelatin can be used for much more than a sweet treat. It can also act as a smoked lens—which allows you to view total internal reflection—or as a color filter.
Laser Speckle
A laser pointer and a frosted light bulb are all you need to investigate laser speckle, grainy patterns in laser light that seem to move differently depending on your visual acuity.
Lateral Inhibition
Do receptors in our eyes act independently, or do they influence each other? Look through some simple paper tubes and explore how your eyes work.
Leaf Filter
Photosynthesis requires light, but plants don’t use all the colors that make up white light. Use a spectroscope to explore the absorption and transmission of white light through leaf material.
Life Size
Explore the size and scale of microscopic biology.
Light Conversation
Explore the behavior of a common night-light controlled by a photocell sensor, and the interaction of two or more night-lights with one another.
Light Wind
Use wind to power a motor and generate enough electricity to light an LED.
Look into Infinity
If you've ever been between two mirrors that face each other, such as in a barbershop or a beauty salon, you're be familiar with the seemingly endless line of images fading into the distance. This Snack recreates this effect.
Looking a Little Spotty
By digitally manipulating an image, you can test how well your brain can see something where—at first glance—there appears to be nothing but spots.
Magic Wand
When you view a projected slide show or a movie, where is the picture? Is it on the film, in the air, on the screen, or in the eye of the viewer? This Snack will help you investigate and locate this type of image.
Magnetic Atmosphere Model
Ring magnets stacked on a pencil model Earth’s atmosphere, demonstrating how both density and pressure decrease with height.
Magnetic Chains
Build a model using a scale and tiny spherical magnets to show how the arrangement of domains in a magnet affects its overall strength.
Magnetic Fruit
When we think about objects that respond to magnets, fruit usually doesn't come to mind. Watch a rare-earth magnet repel a grape and discover different kinds of magnetism.
Magnetic Lines of Force
Iron filings will line up parallel to a magnetic field, making the pattern of the field visible. This is a simple Snack to build—and because the filings are trapped in a bottle, they don’t make a mess.
Magnetic Pendulums
The current generated when one copper coil swings through a magnetic field will start a second coil swinging, showing some of the ways that electricity and magnetism interact.
Magnetic Shielding
Magnetic-field lines pass through cardboard, air, and certain other materials, depending on whether they're permeable or nonpermeable. Test different materials to see which are which.
Magnetic Suction
Have you ever wondered how an old-style doorbell works? This Snack shows you how. A coil of wire with current flowing through it forms an electromagnet that acts very much like a bar magnet. The coil will magnetize an iron nail and attract it in a remarkably vigorous way.
Make Your Own Rainstick
The rainstick is a traditional instrument thought to have originated in Chile, where cactus spines are inserted into dried, hollowed-out cactus branches that are then filled with pebbles, raw rice, or dried beans.
Marshmallow Puff Tube
Experiment with cardboard tubes of different lengths to see how far you can blow a marshmallow.
Melting Ice and Rising Seas
Does the location of melting ice on Earth lead to different effects on sea level rise? Investigate with this model of seas and continents.
Michelle O (formerly Vanna)
Your brain gets used to seeing familiar things in certain ways. When the brain receives a strange view of a familiar object, the consequences can be intriguing.
Microbalance
Make a balance that weighs very light things.
Micrometer Caliper
Make a device sensitive enough to measure the thickness of a sheet of paper or the diameter of a human hair.
Milk Makes Me Sick
Use glucose test strips to investigate the function of the lactase enzyme and discover what it means for milk to be "lactose free."
Mind the Magnetic Gap
A swinging aluminum plate stops dead in the presence of a strong magnetic field, demonstrating the presence of eddy currents.
Miniscopio para teléfono celular
Abre tus ojos al maravilloso mundo de lo ultrapequeño al convertir tu teléfono celular en un miniscopio portátil para tomar fotos con una simple lente de plástico de un puntero láser.
Mirror Reversal
Mirrors seem to reverse left and right, but not up and down. Actually, they don’t do either.
Mirrorly a Window
When your brain expects to see one thing and is presented with something quite different, you may feel some peculiar sensations.
Modelo de desintegración radiactiva
Arroja cien monedas. Retira todas las que queden en “cruz” y arma una columna con ellas; repite… De esta manera, tú has generado tu propio modelo práctico para representar el fenómeno de la desintegración radiactiva.
Modulated Coil
Transfer the sound from an iPhone, iPod, or radio to the speaker of a cassette-tape player by merely holding a coil of wire near the player when it's running—without a cassette in place.
Modulated LED
An LED connected in place of a headphone will flicker at the same frequencies that the headphone would have vibrated. If the light hits a solar panel connected to a speaker, it can reconstruct the sound.
Moiré Patterns
Moiré patterns appear whenever one semitransparent object with a repetitive pattern is placed over another. They can be used to demonstrate wave interference.
Momentum Machine
You’ve probably seen an ice skater spinning on the tip of one skate suddenly start to spin dramatically faster. This speeded-up rotation results from a sudden redistribution of mass. You can make yourself suddenly spin faster while sitting in a rotating chair.
Motor Effect
This simple device shows that when an electrical current flows through a magnetic field, a force is exerted on the current. This force can be used to make an electric motor.
Naked Egg
Use de-shelled chicken eggs as models for investigating diffusion and osmosis across plasma membranes.
Non-Round Rollers
The most common closed and curved plane figure that has a constant width as it rotates is the circle. Surprisingly, however, there are other figures that have this property. You can construct a variety of these shapes with a compass and straightedge. The rollers you can build with this Snack behave in seemingly paradoxical ways.
Oboe de pajilla
Al cortar dos “labios” en el extremo aplanado de una pajilla de refresco y soplar con la presión adecuada, puedes hacer que los sonidos resuenen en la pajilla.
Ocean Acidification in a Cup
Create a carbon dioxide–rich atmosphere in a cup and watch how it diffuses into the water beneath it, causing the water to become more acidic. Ocean acidification is a change that can be harmful to marine life.
Oil Spot Photometer
When an oil spot on a card is illuminated equally from both sides, it mysteriously disappears. This allows you to compare the brightness of the light sources on either side of the card.
On the Fringe (formerly Bridge Light)
When light hits two slightly separated transparent surfaces, part of the light will be reflected from each surface. If the distance between the surfaces is a multiple of half the wavelength of any one color of light, destructive and constructive interference will occur, producing an interference pattern.
Orejas de diseñador
Investiga cómo orejas de diferentes formas afectan tu audición.
Organ Pipe
You can amplify a tuning fork by holding it over a pipe and changing the length of the pipe. At certain pipe lengths, the pitch made by the tuning fork sounds very loud as it resonates with the air column in the pipe.
Our Changing Atmosphere
Graph carbon dioxide data from the National Oceanic and Atmospheric Administration (NOAA) to learn about natural cycles and unnatural changes in our atmosphere.
Out of Sink
Change a bottle’s shape to affect the buoyancy of a Cartesian diver inside of it. Make the diver rise when the bottle is squeezed in just the right way.
Outdoor Shadows
Go outside and trace an outline of your shadow. Wait a while, try again, and watch how your shadow changes over time.
Output of a Solar Cell
Measure the efficiency of solar cells as they convert sunlight to power.
Over the Hill
Explore energy transformations by rolling a marble on a track.
Overlapping Spots
You have two eyes, yet you see only one image of your environment. How does your brain interpret brightness when each eye perceives it separately?
Pájaro en una jaula
Tú ves color cuando las células fotorreceptoras en la retina de tu ojo son estimuladas por la luz. Si dichas células se adaptan a un estímulo prolongado, responden con menos sensibilidad ¡y los colores cambian!
Palm Pipes
Banging the open end of a PVC pipe against the palm of your hand makes a musical sound. The tone depends on the length of the pipe. Simple songs can be easily played.
Parabolas
What you perceive as an object in this Snack is really an image in space, created by two concave mirrors. This illusion would do credit to any magician.
Parachute Plummet
Make a parachute using simple materials and watch how the forces of gravity and air resistance affect it as it falls.
Pasta Quake
Break spaghetti to create a “pasta magnitude scale” that models the energy released in an earthquake.
Pendulum Snake
Ten pendulums of different lengths swing back and forth at different rates. As they swing, they move in and out of interesting patterns.
Penny Battery
Use two different metals and some sour, salty water to create an inexpensive battery.
Periodic Pasta Table
Create a three-dimensional model of the periodic table that uses sticks of spaghetti to show how trends of atomic properties are used to organize elements into periods and families.
Peripheral Vision
Test the limits of your peripheral vision and measure how much you can see out of the corner of your eye. You’ll find that you can detect motion at a wide angle, colors at a narrow angle, and detailed shapes at a surprisingly narrow angle.
Persistence of Vision
When you look through a narrow slit, you can see only a thin strip of the world around you. But if you move the slit around rapidly, your eye and brain combine these thin strips to make a single complete picture.
Personal Pinhole Theater
Have you ever heard of a camera without a lens? Get an inside look at how a lensless camera works.
Photoelectricity
Recreate the experiment that proved Einstein’s theory that light waves are made up of quantized energy—what we now call photons.
Photosynthetic Floatation
Show that gas is produced during photosynthesis.
Pi Graph
Use straight lines to learn about circles.
Pi Toss
Randomly toss some toothpicks, with pi as your reward.
Pie-Pan Convection
Visualize the fluid motion of convection cells. For this activity, all you need is soapy water, a heat source, and some food coloring—the effect caused by the rising and sinking fluids is spectacular.
Pinhole Magnifier
A pinhole in a card can act like a magnifying glass, helping your eye focus on an object that is very close to you. However, by limiting the amount of light that reaches your eye from the object, the pinhole also makes the object appear dimmer.
Pipes of Pan
Separate the hum of background noise into some of its different frequencies.
Pixel Tube
Rolls of shiny Mylar bundled into a tube together create a dazzling pixelated view of the world.
Pixels, Pictures, and Phones
Learn about screen technology and human visual perception by investigating color images up close. Even the fanciest smartphone screen only has three colors.
Plankton Projector
Who needs a microscope to see what lives in a drop of water? Instead, shine a laser pointer through a drop of water and be dazzled by a display of tiny organisms.
Plankton Rainbow
Brine shrimp swim in different directions in response to light. But do they respond equally to all colors of light?
Plot the Dot
Graphs can reveal patterns that lead to deeper understanding of phenomena. Collect some data from ordinary objects to reveal a constant in nature.
Poking Fun at Art
Set up some red, green, and blue lights and build a simple pinhole viewer to investigate colorful and creative mixtures of light.
Poking Fun at Color Mixing
Mix red, green, and blue light using a pinhole viewer and conduct simple scientific investigations into human color perception.
Poking Fun at Light Rays
Build a simple pinhole viewer and set up some colored lights to investigate how light gets from Point A to B.
Poking Fun at Math
Investigate pinholes with a simple viewing device and some colored lights, and collect data to create real mathematical formulas.
Polarized Sunglasses
When light reflects from nonmetallic surfaces, it becomes polarized—the reflected light is usually vibrating more in one direction than others. Polarizing sunglasses reduce this reflection when the polarizing lenses are oriented properly.
Polarized-Light Mosaic
Using transparent tape and polarizing material, you can make and project beautifully colored patterns reminiscent of abstract or geometric stained-glass windows.
Pop Bottle
Twisting a plastic water bottle changes its volume, pressure, and temperature—and ends with a bang.
Productive Poop
Given the right conditions, worms can accelerate the breakdown of rotting food and produce rich compost in return.
Proprioception
Even with our eyes closed, we have a sense of our body parts and their position thanks to proprioceptors in our muscles, tendons, joints and inner ear. They (and our brains) provide a sense of body orientation and movement.
Pulgas eléctricas
La electricidad estática produce chispas cuando te peinas en un día de frío y hace que los globos se peguen a la pared. Aquí, la electricidad estática hace que las “pulgas” eléctricas comiencen a saltar.
Pupil
You can watch the pupil of your eye change size in response to changes in lighting. You can also experiment to determine how light shining in one eye affects the size of the pupil in your other eye.
Radioactive-Decay Model
Throw one hundred coins, remove all those that come up tails, and place them in a pile, repeat—you'll have made yourself a hands-on model for radioactive decay. The piles graphically show the meaning of the term “half-life.”
Radiohead
Most of the time, we hear sounds transmitted through the air, but that’s not the only way to hear things.
Raining On Your Data Parade
Sometimes when you’re looking at data, you come across something surprising—a measurement that’s so unusual, you wonder if it’s correct. Take a look at some actual data from a rain gauge, then investigate what is likely to be accurate, and why.
Re-Engineering the Circulatory System
Engineering isn’t just about physics; it’s part of life sciences too! Using simple materials, students can design, build, and test their own model circulatory system, and then figure out how to make it better.
Real Image
Looking for Real Image? Parabolas is an alternative Snack that relates to the same general principles.
Remote-Control Roller
Rub a balloon on your head, then watch a soda can race across the floor. As you observe the interplay between electrons and protons, you’ll also discover why clothes cling together in a dryer.
Resonant Pendulum
By exerting very small forces at just the right times, you can make a massive pendulum swing back and forth in very large swings.
Resonant Rings
This device graphically demonstrates that objects of different sizes and stiffness tend to vibrate at different frequencies.
Resonator
Explore resonance to discover how objects vibrate at certain frequencies. When you shake your Resonator at just the right frequency to cause one dowel to vibrate violently, another dowel may hardly vibrate at all.
Reverse Masks
One mask protrudes from the black surface like an ordinary face, and the other is indented into the surface. When you close one eye and view the two masks, they both look like they are protruding, and when you move sideways, the indented mask seems to turn to follow your movement!
Rodillo a control remoto
Frota un globo en tu cabeza, luego observa cómo una lata de refresco corre por el piso o una mesa. Al observar la interacción entre los electrones y los protones, también descubrirás por qué la ropa se pega en una secadora.
Rotating Light
White light is made up of all the colors in the rainbow. When polarized white light passes through a sugar solution, each color’s direction of polarization is changed by a different amount. The colors change as the depth of the solution changes or as the polarizing filter is rotated.
Saltwater Pentacell
Make a battery by creating five simple cells from aluminum foil, copper wire, and saltwater, and connecting them in series. Use the battery to light an LED.
Salty Pits
Explore how different deodorants work and what that means for the bacteria in your armpit.
Scintillating Little Star
Why do stars twinkle? Have a scintillating experience by making your own “light twinkler.” Use a hot plate and laser to show that light can change direction and appear to twinkle.
Secret Bells
Create your own personal sound system with a coat hanger and a string, producing musical sounds that only you can hear.
Secret Codon
Write a message in DNA.
See Inside a Seed
Soaked in water, dried beans spring to life. Learn your way around a legume as you explore the various structures that protect and feed a developing plant embryo.
Seed Germinator
What goes on underground when seeds are sprouting? Make yourself a window onto the process of plant development.
Seeing Your Retina
A dim point of light will cast a shadow of the retina's network of blood vessels onto the retina itself. Try this activity and you'll be able see the blood supply of your retina—and your blind spot.
Self-Centered Globe
Place an Earth globe in sunlight, and you can align it so the patterns of light and shadow match those on real Earth
Sensitive Filament
The exposed filament from a 100-watt incandescent light bulb is wired in series with a flashlight bulb and a 9-volt battery. Blow on the filament and the flashlight bulb gets brighter.
Separation Anxiety
Color chromatography uses capillary action and the fact that different types of ink migrate different rates. Use this technique to discover the secret colors hidden in black ink.
Shaky Sediments
This Snack models ground failure in a phenomenon called liquefaction. See what happens when you shake up structures, loose sediments, and water in a simulated earthquake.
Shell Shifts
Increasing amounts of carbon dioxide in the atmosphere are making the ocean water more acidic. See why this makes it harder for shellfish to build and maintain their shells.
Short Circuit
Current flowing through a wire heats the wire. The length of a wire affects its resistance, which determines how much current flows in the wire and how hot the wire gets.
Shrinking Spot
In this perception illusion, an automatic reflex causes light entering one eye to change what you see in the other eye, demonstrating one of your visual system’s many idiosyncrasies.
Single-Serving Volcanism
Simulate subsurface magmatism and surface volcanism by injecting a sweet sauce into a single-serving cup of gelatin.
Siren Disk
Sounds can be made in some surprising ways. Blowing air through a spinning disk full of holes can make a variety of pitches.
Size and Distance
By removing clues to the actual size and distance of an object, you can trick your brain into thinking that two similar objects of different sizes are really the same size.
Sizing Up
Discover some big surprises in the microscopic world.
Sizing Up Temperature
Discover the relationship between temperature and volume of a given amount of gas.
Skin Shield
Explore the body’s first line of defense against pathogens.
Skin Size
Work out the approximate surface area of your skin while also figuring out the approximate amount of atmospheric force pushing on it.
Skippy
Skippy is a mechanical creature that uses an off-center rotation, or eccentric motion, to produce interesting vibrational behavior.
Sliding Gray Step
Make one shade of gray look like two by putting it against two different color backgrounds.
Slinky in Hand
With just a Slinky and your hands, model transverse wave resonances as well as longitudinal wave resonances. Learn about nodes and antinodes of motion and compression.
Slow Your Roll
In this activity, you can investigate the motion of a slow-moving wheel on a track by using a timer, tape, and permanent marker.
Soap Film Interference Model
By experimenting with this model of light-wave addition, you can understand the behavior of light reflecting off soap films. Why do you see blue or red? It’s all a matter of phases.
Soap Film on a Can
Why do we see colors in oily water and soap bubbles? Experiment with soap film to observe the behavior and colorful appearance of different wavelengths of light.
Soap Film Painting
Under the influence of gravity, a thin soap film constantly changes thickness, creating an ever-shifting array of colors.
Soap-Bubble Shapes
Make three-dimensional geometric frames of different shapes, then dip them in a soap solution to form fascinating and colorful soap films.
Soda Can Mirror
Wrap a piece of Mylar around a soda can to make a cylindrical mirror. Then create your own anamorphic art to explore how curved mirrors reflect images.
Sonidos maravillosos
Haz un tocadiscos con materiales simples y escucha tu LP de vinilo favorito. No se requiere una fuente de electricidad.
Sound Bite
When you listen to a radio or music player, you normally hear the sound coming from the speaker or headphones. But in this Snack, you pick up sound vibrations through your teeth!
Sound Cups
This Snack encourages participants to ask questions, carry out investigations, and use their senses to find a person whose Sound Cup matches theirs, and then together recreate the sounds they hear.
Sound Sandwich
By making simple adjustments to this noisemaker, you can raise or lower its pitch and make different kinds of sounds.
Spaghetti Accelerometer
How does your phone know to rotate its screen when you rotate the phone? Make a model of your phone’s accelerometers, tiny sensors in your phone that detect changes in motion.
Spaghetti Resonance
If you shake an object or otherwise make it vibrate at its natural frequency, it will start to vibrate more and more, often violently enough to break.
Spherical Reflections
Round mirrored holiday ornaments packed together in a box create an array of spherical reflectors. Study the properties of spherical mirrors while you create a colorful mosaic of reflections.
Spinning Blackboard
When you draw on a spinning disk, you make unexpected patterns. If you try to draw a straight line, for instance, what appears on the disk is a spiral. The patterns you make result from adding the motion of your hand to the spinning motion of the disk.
Spinning Cylinder
A piece of pipe with a mark at each end is set rotating and spinning at the same time. In the blur of the moving cylinder, one of the marks appears three times, forming a stationary triangle.
Square Wheels
A square wheel will roll smoothly, with its axle at a constant height, on a surface with bumps of the right size and shape.
Squeeze Box
Compress layers of sediments in an easy-to-build deformation chamber to see folds, faults, and other geologic features develop in real time.
Squirming Palm
Stare at a waterfall for some time and then stare at the rocks nearby—the rocks will appear to be moving upward. This illusion is known as the waterfall effect, and you can recreate it—without getting wet.
Stereo Sound
Sound from a given source must travel slightly different distances to reach your two ears, which each hears the sound at a slightly different time. This lets you determine where a sound source is located.
Strange Attractor
Patterns of order can be found in apparently disordered systems. This pendulum—a magnet swinging over a small number of fixed magnets—is a very simple system that shows chaotic motion for some starting positions of the pendulum. The search for order in the chaos can be engrossing.
Straw Oboe
By cutting two “lips” into the flattened end of a soda straw and blowing with just the right pressure, you can make sounds resonate in the straw.
String Machine
By attaching a string to two small electric motors rotating in the same direction, you can create and play with a special class of waves called standing waves.
Stripped-Down Generator
In an electric power plant, steam or water power is used to move huge coils of wire past extremely strong magnets, generating megawatts of electricity to light whole towns. This Snack uses your muscles to move ordinary magnets past a small coil of wire, generating milliwatts of electricity—just enough to light an LED. The two generators work at very different scales, but they are both based on the same physics principles.
Stripped-Down Motor
A coil of wire becomes an electromagnet when current passes through it. The electromagnet interacts with a permanent magnet, causing the coil to spin. Voilà! You’ve created an electric motor.
Swelling Seas
Watch water swell and shrink with heating and cooling.
Take It from the Top
Simple wood blocks can be stacked so that the top block extends completely past the end of the bottom block, seemingly in a dramatic defiance of gravity. The trick is to move the top block first and then proceed on down the stack.
The Three Little Pigments
Investigate how light and color interact by aligning cyan, magenta, yellow, and black transparencies.
Thread the Needle
Close one eye and you eliminate one of the clues your brain uses to judge depth. Trying to perform a simple task with one eye closed demonstrates how much you rely on your depth perception.
Tidal Ties
Examine water-depth measurements from the Exploratorium and make predictions about water temperature and salinity.
Tide-O-Matic
Model the equilibrium theory of the tides and discover why there are two tide cycles per day, why the heights of the tides change over the course of a month, and why the tides occur about an hour later each day.
Tiny Hot Pile
No yard? No problem. Make a mini indoor compost pile, and look for evidence of microbial metabolism.
Tired Weight
You don't need to be a sideshow strongman to calculate the weight of a car—you can do it by measuring the surface area of each tire's "footprint" and the pressure inside each tire.
Touch the Spring
Place an object in front of a concave mirror so it isn't visible to the viewer, but the viewer can see the mirror image of the object formed in space. Try to touch the image—your fingers pass right through it.
Truly Primary Pigments
The primary colors of pigment are cyan, magenta, and yellow, which can be mixed to make many other colors, but demonstrating this can be difficult if you want to use markers. Using printer ink to make your own markers will give you more accurate results.
Tu sentido del gusto
Percibimos sabores a través del trabajo de distintos tipos de receptores en nuestras lenguas. Estos receptores se unen a las moléculas químicas en nuestros alimentos y transmiten la información sobre dichos químicos a nuestros cerebros.
Tubo lanzador de bombones
Experimenta con tubos de diferentes longitudes para ver cuán lejos puedes hacer viajar un bombón con tu soplido.
Twirling Tester
Rotational inertia (sometimes called angular inertia) is the rotational analog to linear inertia. This Snack explores what makes some turning objects harder to start and stop than others
Two-Slit Experiment
Recreate the two-slit experiment by shining a laser pointer through two narrow slits and observing the interference pattern on a distant screen.
Two-Slit Wave Model
By experimenting with this model of light-wave addition, you can understand the behavior of light as it passes through two narrow slits.
Uncanny Motion
On a flat tabletop, arrange two empty cans so you can blow between them. Depending on one small detail, the cans either come together or move apart.
Vector Toy
A mass hangs from a string attached to the front of this walking toy (also called a "ramp walker"). Watch as the string almost draws the vectors that make the toy work.
Vegetable Revival
Use vegetable scraps from your kitchen to investigate the stem cells of plants and their potential for new growth.
Viral Packaging
Solve the problem that took viruses millions of years to conquer by efficiently fitting nucleic acid and proteins into a small package.
Vocal Visualizer
Croon a tune, croak like a frog, hum, hoot, or holler—you don’t need to be Pavarotti to transform laser light into dazzling shapes and patterns with the power of your voice.
Vortex
Water forms a spiraling, funnel-shaped vortex as it drains from a soda bottle. A simple connector device allows the water to drain into a second bottle.
Wait, Weight, Don't Tell Me!
A simple chemistry experiment—adding baking soda to vinegar—seems to challenge the law of conservation of mass.
Water Sphere Lens
A round bowl of water can act as both a magnifier and a lens.
Water Spinner
When you spin a tank of water on a lazy Susan, the surface of the water forms a curve called a parabola.
Water-Bottle Membranophone
Kazoos and drums are membranophones—instruments that produce sound from a vibrating stretched membrane. Here, a water bottle and a paper tube make a membranophone that sounds like a saxophone crossed with a clarinet.
Whack-a-Stack
A simple stack of wood blocks demonstrates that an object at rest will remain at rest unless a force causes it to move.
What's the Size of What You See?
Determine the field diameter of a compound microscope.
Where's North?
Observing the effects of the earth’s magnetic field on magnets is similar to some of the earliest experiments conducted on magnets.
Whirling Watcher
A series of slits moving rapidly past your eye allows you to see images in short bursts. Such rapid but fragmented views of moving objects can make the objects appear to jerk along, change speed, or even move backward.
Wiggle Pressure
Self-rolling pet toys can wiggle around, pushing on objects a lot like air molecules do, modeling many of the behaviors of the molecules in gases.
Wind Turbine Power Lifter
Using skateboard bearings to reduce friction, build a wind turbine sturdy enough to lift a weight. Adjust your turbine’s blade design to investigate—and maximize—the power you can extract from the wind.
Your Father's Nose
In a normal mirror, you see your own face looking back at you. But what if you looked into a mirror and saw a face that was partly yours and partly another person’s?
Your Sense of Taste
We perceive flavors through the work of different types of receptors on our tongues—those that detect sweet, sour, salty, bitter, and umami (savory). These receptors bind to chemicals in our food and transmit the information about the chemicals to our brains.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Attribution: Exploratorium Teacher Institute
