Topic Index
Atomic Physics
Balloon Universe, Blow up a balloon and model the expansion of the universe.
Bouncing Balls, bounce a tennis ball on a basketball, it will gain energy.
Candle in Freefall, drop a candle in a plastic bottle and observe how it behaves in freefall.
Circle Universe, imagine how the expansion of a universe that is a circle would appear to an inhabitant of the circle.
City Universe, Imagine a city in which light travels one block per decade, how would it look? An exploration of time in the universe.
City Universe Size, map the size and locations of objects in the 14 billion year old universe onto a city street that is 14 blocks long.
Cratering, Make craters in salt and study ejecta.
Curved Space, There is more distance between two objects when a massive object is brought nearby. relativity.
Dance of the Day and the Year, Why the length of the day varies from 24 hours over the course of a year.
Dance of the Sun and the Moon, Dance your way to understanding Eclipses.
Earth Rotation, measure the length of a sidereal day.
Expanding Universe, Use two transparencies to show how everyplace is the center as the universe expands
Expansion of light, when light travels through an expanding universe its wavelength is stretched.
Find Fibonacci numbers in plants, count the number of spirals in pineapples, pinecones and artichokes.
Gravitational Lens, model the images formed by a gravitational lens produced by a distant galaxy using the base of a wineglass.
Gravity Assist, a simple non-vector calculus example of how a spacecraft gains speed passing around a planet.
Gravity Well, Roll a marble around a correctly shaped funnel and study the orbits of satellites and planets.
Gravity Well Explainer, feel the forces involved in the gravity well experiment.
Icy Bodies, create comet models using dry ice.
Mars Calendar and Clock, make your own calendar and also a clock for use on Mars.
Mars Size, Explore the size of Mars using clay.
Moon Phases, Use a lamp and styrofoam ball to model the phases of the moon.
Moonwalk, Walk on an inclined plane with assistance from a rope to feel lunar gravity.
MR diagram, graph the mass versus radius of everything in the universe.
Partial Eclipse, several methods to allow safe viewing of a partial solar eclipse.
Playdough Moon, Construct a scale model of the earth and moon from playdough.
Self Centered Globe, Place an earth globe in sunlight and see a model of the sunlight pattern on the real earth.
Spin a Koosh, Model the equatorial bulge of the earth by spinning a koosh ball.
Tides, use dancing people and models drawn on transparencies to model the tides.
Tide Gravity, use a gravity well to model the tides.
Transit of Venus, learn how observations of Venus moving across the face of the sun led to the measurement of the Astronomical Unit, the size of the solar system.
Universe City size, Map the entire universe onto 14 city blocks.
Universe City time, Take a walk down a street where light travels 1 block per decade.
Bubbles in a bottle, Fill a bottle with soap solution, pour it out and the bottle will fill with bubbles.
Bubble Prints, Blow bubbles in a solution laced with food coloring and you can lift bubble prints onto paper.
Film Can Periodic Table, use pennies in film cans to model atoms in the periodic table.
Film Can Rocket, Baking powder and water create gas which propels this rocket.
Highway Seismometer, measure road bump magnitude with a pen and paper. Model earthquake magnitude.
Ice Balloon meanders, Salt on ice balloons creates runoff that carves meandering channels.
Mica, Heat mica and it will swell up, this was used as home insulation.
Pasta Quake, illustrate a magnitude scale of earthquakes by breaking pasta.
Water Cycle Video, watch the water cycle video by Andrej Zdravic and write a narration for it.
Spinning Cylinder. Explore the stable patterns produced by a spinning PVC cylinder.
Angular Size, the definition of the angular size of an object in radians and degrees.
Bicycle Gear Mathematics, count teeth on bicycle gears and find ratios.
Bicycle Gear Ratios, explore the mathematics of bicycle gears.
Bifurcation, droplets of food color divide over and over when dropped into water.
Bouncing Ball, drop a steel ball onto a steel surface and listen to the pattern of bounces, listen to Zeno's paradox. (You can also drop it onto a can covered with a balloon.)
Cardiod, use magnets to draw a cardiod
Chaotic Pendulum, an exploration of the exhibit or the toy.
Curved Pi, what is the ratio of the circumference of a circle to its diameter on a sphere?
Fractal Paint, One drop of model airplane paint will spread into a circle between two CD jewel boxes and pull into a fractal.
Frequency, the relationship between frequency and period.
Frequency of the fundamental, How the frequency of the fundamental oscillation of a spring depends wave speed and length.
Frequencies of the Harmonics, harmonics have frequencies which are integer multiples of the fundamental.
Glide Ratio, measure the glide ratio of a paper plane.
Gray step, a digital model of lateral inhibition.
Interference, calculate the angles of the minima from 2 slits
Mars Calendar and Clock, make your own calendar and also a clock for use on Mars.
Mars Size, Explore the size of Mars using clay.
Metric Prefixes, check out the new metric prefixes, like yocto and Yotta then try the quiz
Mobius, count the edges and sides on a Mobius strip.
Mobius Collision, collide to Mobius strips and analyze the resulting strip.
Mobius Decay, analyze the products when a Mobius strip fissions.
Mobius Dissection, cut a Mobius strip in half, but first, predict what will happen.
Mobius Space, Move a pattern around a Mobius space and watch it convert from right to left.
Model Fibonacci numbers in plants, create a model of plant growth and see if it produces Fibonacci numbers of spirals.
Multiplication Blocks, place these blocks side-by-side and they multiply!
Patterns of Nature, A two day workshop on patterns in nature.
Pendulums, find out how the period of a pendulum depends on its length, and other factors.
Pinhole, Optimum size, Find the best size for a pinhole.
Planet Shape How to add rotationally symmetric basic shapes to create the shape of a planet.
Plant Leaf Patterns, a mathematician designs a plant, place leaves around a plant 137.5 degrees apart.
Playdough Moon, Construct a scale model of the earth and moon from playdough.
Refraction, trace light through layers.
Relativity Television, Consider the time and space measured by an electron in a television. Right and Left, explore the meaning of right and left.
Rotation of the Earth, Observe the motion of the sun and stars and discover that the solar and sidereal days have different lengths.
Simple Inverse Square, use a simple photometer to compare the brightness of one light to four lights.
Speed of a wave, measure the speed of a pulse on a phonecord.
Speed of a wave vs. tension and density, calculate the speed of a wave in a phone cord based on its tension and density.
Spirograph, use spirographs to investigate greatest common divisors, modular mathematics, and art.
Waterwaves, Measuring the period, and wavelength of an ocean wave to get its speed.
Atomic PhysicsBohr Atom Model, Use a gravity well to model how stable electron orbits form around a proton.
Energy Level Model, use a stool to illustrate energy levels of an atom.
Domino Model of a Nerve, a line of falling dominos models the discharge of a nerve.
Dry Tongue, Dry taste buds don't work. Sugar on a dry tongue is not sweet.
Aluminum Air Battery, Use activated charcoal and aluminum foil to make a battery.
Ammeter, wind your own coil and make an ammeter
Attract a water surface electrostatically, Charged plastic can pull up a mound in water.
Batteries and Bulbs, Use the bulbs themselves to probe the power distribution in series and parallel circuits.
Battery, Bulb, Meter, Make a flashlight then measure voltages and currents with a meter.
Battery Bulb Meter 2000, measure series and parallel circuits containing batteries and bulbs.
Battery Dissection, take apart a carbon zinc battery.
Camera Electronics, study the strobe unit electronics on a disposable camera.
Electric Current Model, magnets rolling around the rim of another magnet model electricity.
Electric Dill, Put dill in oil, move it with electrostatic fields.
Electrophorus, move charge around
Electrostatic attraction of water, hold an electrically charged comb over the surface of water and watch the reflections in the surface of the water distort.
Electrostatic clearing of mist, use an electric wind from a Van deGraaf to move CO2 mist.
Electrostatic Motor, Move a meter stick with an electrically charged rod.
Flying hydra, electrostatic repulsion flies plastic
Flying tinsel, electrostatic repulsion flies aluminized mylar
Glowing Pickle, A pickle glows in sodium light at 110 volts AC use a GFI for protection.
Making Battery Holders, several ways to make a battery holder.
Meters, current, How to use a meter to measure electric current.
Meters Voltage, Use a meter to measure the voltage across a battery
Meters Resistance, Use two meters to measure the voltage across and current through a circuit element.
Multimeter Electroscope, a digital multimeter can be used to measure the sign of a static electric charge.
Neon Tubes, explore electricity with neon glow tubes.
Quiet Lightning, Explorations at the Exploratorium Exhibit.
Saltwater battery, make a battery with salt water, copper wire and aluminum foil.
See Electric fields, use fresh dill seed in oil to see electric field direction.
Solar Cells, measure the power produced by a solar cell.
Tape electroscope, using sticky tape as an electric charge detector
Voltage, Use a meter and a battery to measure voltage and explore its meaning.
Atmosphere Bar, make a steel bar that exerts the same force on you as the earth's atmosphere.
Blow between cans to make them move together or apart. Bernoulli in action.
Buoyancy, compare the buoyancy of crumpled aluminum foil to flat.
Bubbles in a bottle, Fill a bottle with soap solution, pour it out and the bottle will fill with bubbles.
Candles in a jar, Observe candles at different levels in a jar go out one by one.
Candle in a vacuum, Slowly pump the air out of a jar containing a candle.
Curve Balls, use the magnus force and Bernoulli's equation to explain curve balls.
Floating Coins, Aluminum coins can be "floated" on the surface tension of water.
Lava Lamp Sprinkle salt onto a layer of cooking oil floating on water and create convection plumes.
Martian water, explore the triple point of water where it freezes and boils at the same time.
Neutral Buoyancy Create a ball of oil floating in a mixture of water and isopropyl alcohol.
Paper Airplane Science, build a paper airplane, find its center of gravity and pressure, make it stable and controllable, measure its glide ratio.
Pump, Film Can, Make a water pump out of a film can.
Soap driven convection in milk, Food coloring is used to trace surface tension driven convection in milk.
Styrofoam Airplane, Turn a Styrofoam plate into a stable airplane one step at a time.
Sugar Cube in Oil, drop food coloring onto a sugar cube in cooking oil.
Terminal Velocity, Drop basket type coffee filters and find their terminal velocity.
Vacuum Bottle Collapse, use a vacu-vin to pump the air out of a stiff plastic bottle, sudden buckling results, whomp.
Water Cycle Video, watch the water cycle video by Andrej Zdravic and write a narration for it.
Water Glass, A stiff piece of paper holds water in an inverted glass.
Water Wave Video, watch the wave video by Andrej Zdravic.
Audible Magnetic Domains, Use an iron cored coil and audio amplifier to listen to the motion of magnetic domains, known as the Barkhausen effect.
Black Sand Exploration, Magnetic sand is pulled into spikes when near a magnet.
Floating in Copper, Eddy currents allow you to fly a magnet between two slabs of copper.
Force between Two Magnets, The force between two magnets can be measured with a digital scale.
Garden of Magnets mini, Float magnets in a tray and they will form crystal patterns.
Magnetic Accelerator, ball bearings and magnets can be arranged to create great velocity increases.
Magnetic Atmosphere Model, balance five magnets on a pencil and model the atmosphere.
Magnetic Feedback, use a radioshack amplifier and pickup to model how a metal detector works.
Magnetic Field of planets, which planets have magnetic fields and why.
Magnet flyer, Fly a magnet between two metal disks.
Magnetic Globe , A toy Earth with a magnet inside has the same magnetic field as the earth.
Magnetic Guide Rail, A slab of aluminum will guide a rolling disk magnet to roll along its center.
Magnetic optical bench, laser pointer mounts.
Magnetic Oscillator, two magnetic oscillators are coupled invisibly by their magnetic fields.
Magnetic Poles , An exploration of the attraction and repulsion of magnetic poles.
Magnetic Push-ups, Use tape to hold one magnet flying over another.
Magnetic Silent Collisions, Collide two magnets on a pencil.
Magnetic Tape, Build a digital tape recorder using bits of cassette tape. Model continental drift.
Magnets 3 vs 1, feel how the magnetic force between two groups of magnets gets stronger as you add more magnets, and bring them closer together.
Magnets Round the Rim, Roll small magnets around a large one to model electric current .
Repel a Grape, Use a strong neodymium magnet to repel a grape which contains diamagnetic water.
Where's North? , Hang several magnets and they all line up!
Accelerometer, measure acceleration with a protractor
Bicycle Gear Mathematics, count teeth on bicycle gears and find ratios.
Bouncing Ball, drop a steel ball onto a steel surface and listen to the pattern of bounces, listen to Zeno's paradox. (You can also drop it onto a can covered with a balloon.)
Bouncing Balls, bounce a tennis ball on a basketball, it will gain energy.
Bouncing Egg, Drop an egg on a basketball the bounce is surprising and eggs-citing.
Candle in Freefall, drop a candle in a plastic bottle and observe how it behaves in freefall.
Computer Stroboscope, watch a rubber band vibrate in slow motion in front of a computer screen.
Coupled Pendulums, Explore how two coupled pendulums send motion back and forth.
Drop a Slinky, the top of the slinky falls faster than g.
Falling Coins, a moving coins falls at the same rate as one starting at rest.
Falling Dominos, In a line of falling dominos each domino is exponentially bigger than the previous one.
Falling faster than g, some parts of a stretched slinky fall faster than g, some fall slower, and some fall just right.
Falling Rhythm, drop weights spaced along a string and listen to their rhythm.
Film Can Rocket, Baking powder and water create gas which propels this rocket.
Frictionless CD puck, make an airpuck with a CD and a balloon.
Gravity Assist, a simple non-vector calculus example of how a spacecraft gains speed passing around a planet.
Gravity Well, Roll a marble around a correctly shaped funnel and study the orbits of satellites and planets.
Gravity Well Explainer, feel the forces involved in the gravity well experiment.
Newton's laws. Simple experiments to explore Newton's laws of motion.
Ollie Physics, how to make a skateboard follow you up and over by pushing down
Pendulum, make a pendulum and find how its period depends on its length.
Pendulum Snake, observe how a set of pendulums moves from order to chaos then back to order again.
Phase Pendulum, explore why the sky is blue and the cause of refraction.
Reaction Timer, measure your reaction time with a ruler.
Relative Motion Pendulums, The eye and brain jump into the moving reference frame of a pendulum table and so add two oscillations at right angles.
Slinky, falling faster than g
Spoon Rattleback, Make a rattleback by bending a spoon.
Spring Scales, Explore the readings on two springs scales when they are hooked together.
Stocking Force Visualization, The stretch on a stocking shows the force it is exerting.
Terminal Velocity, Drop basket type coffee filters and find their terminal velocity.
Turning in air, How can a person in freefall turn around while initially at rest?
Light Energy vs Color, find that the voltage necessary to light a blue LED is greater than that for a red.
Nuclear Fission, chain reaction human model.
Nuclear Fission, magnetic model.
Particle accelerator, Roll a coin around in a balloon to simulate an accelerator.
Radioactive Decay Model, have a large audience of people flip coins listen to radioactive decay.
Radioactive Decay Math Root, the mathematics of radioactive decay.
Relativistic appearance of stars, a series of images
Anti slit, project the spectrum of an antislit through a diffraction grating on an overhead projector
Camera Dissection, Take apart a disposable camera.
Color, Diffraction Grating, project a slit of light on an overhead projector and spread it into a spectrum with a holographic diffraction grating.
Colored Shadows, A red green and blue light make magenta, cyan and yellow shadows.
Colored Shadows Mirror, Reflect light off a mirror at the colored shadows exhibit.
Colors of Nature, A two day exploration of colors in Nature.
Comparing Yellows, an exploration at an Exploratorium museum exhibit.
Computer polarized light source, Use a portable computer as a source of polarized light.
Cylindrical Mirror Image, How to find the two different locations of the image made by a cylindrical mirror.
Diffraction, Observe the diffraction of light as it passes through a narrow slit. Uses a minimaglight.
Diffraction grating , explore color
Energy versus color , red green and blue LEDs turn on at different voltages
Finding images, use a large mirror
Finding Images, Straws, find an image made by a Fresnel lens using a straw viewer.
Fluorescence vs Phosphorescence, explore the differences between these two forms of luminescence
Fresnel lens and laser, trace light rays with a pointer laser
Glowing Pickle, A pickle glows in sodium light at 110 volts AC use a GFI for protection.
Gravitational Lens, model the images formed by a gravitational lens produced by a distant galaxy using the base of a wineglass.
Image on a Mirror, Use a lens to make an image on the surface of a mirror.
Infrared Remote Control, investigate the infrared light from a TV remote control.
Interference, Laser , Shine a laser through two slits to see that Light plus light can equal dark.
Laser CD, reflect and diffract a laser beam off a CD to measure the line spacing of the CD.
Laser Light, explore the beam divergence, frequency,polarization and phase of a laser beam.
Laser Milk, shine a laser through a milk solution and observe the changing pattern of scattered light.
Laser speckle, a laser pointer generates speckles which seem to move when you do
Lightbox, Build a simple lightbox out of a cardboard box.
Light Energy vs Color, find that the voltage necessary to light a blue LED is greater than that for a red.
Locating rays, find the rays emanating from a minimag light point source
Mirror Pairs, Look at yourself in two square mirrors and notice how the images change as you change the angles between the mirrors.
Mirrors and right-left reversal, Explore what mirrors do, and the meaning of right and left.
Peel a CD, The metal coating under the label of a compact disk can be easily peeled off of some cheap CDs this makes the CD into a diffraction grating.
Permanent Oil Slick, A layer of nailpolish on black paper makes interference colors.
Phase Pendulum, explore why the sky is blue and the cause of refraction.
Pinholes 1 versus 3, look though a film can with a single pinhole on one end and three on the other.
Pinhole images, explore your eye and brain and image inversion
Right Left Reversal in a flat mirror., use hands to explore what a mirror does to right and left
Right and Left in 3 different mirrors, what do flat, cylindrical and spherical mirrors do to right and left.
Scan a laser, Scan a laser pointer into a mirror and notice how the beam bounces off the mirror.
Scan a Laser: Lens, Scan a laser into a lens and notice how the beam bends as it passes through different parts of the lens.
Seeing your retina, Use a small dim light to see your own retina.
See your pupil, use a filmcan with a pinhole in the bottom
Simple Inverse Square, use a simple photometer to compare the brightness of one light to four lights.
Soap film colors, use a color image to explore soap film colors
Soap film in a can, a soap film across the mouth of a film can
Soap film interference, modeling soap film interference
Solar Brightness, A photometer is used to compare the brightness of the sun to the brightness of a lightbulb.
Solar Cells, measure the power produced by a solar cell.
Spectra Explorations, Use a diffraction grating or spectrometer to look at spectra of common light sources.
Spectra CD introduction, Reflect sunlight onto a white paper in a shadow.
Spectrometer CD, build a spectrometer with a compact disk.
Two slit interference model, draw sinewaves on white cards and investigate interference.
Ball Packing, Steel spheres in a gentle bowl pack in a hexagonal closest packed array with flaws that can be annealed out.
Polarized light from a laptop computer Use a portable computer liquid crystal display as a source of polarized light.
Poisson Spot, project the shadow of a sphere and notice a bright point of light in its center.
Project a Spectrum, Use a diffraction Grating and an overhead projector.
Ray Tracing, How to use rays to predict the positions of images made by lenses and mirrors.
Red/Green Look at colored photos through red and green filters.
Dance of the Sound Wave, dance out a sound wave step by step.
Decibel meter, measure the loudness of sound with a meter.
Find the highest note, an auditory illusion, use an Exploratorium online exhibit
Opera Loudness, use a sound level meter to measure the loudness of opera singing.
Opera Acoustics, use a frequency analyzer to look at the frequencies of sung vowels.
Phonecord Harmonics, Explore the frequencies of the harmonics of an oscillating phonecord.
Reflections on an open end, How does sound bounce off the open end of a tube.
Ringing Aluminum Rod, Explore the resonances of an aluminum rod. Use your fingers.
Sound Column, Explore sounds in a long concrete tube at the Exploratorium.
Straw Oboe, How to make a straw oboe, how shorter lengths make higher pitches.
Two Head Harp, Wrap a string around the 4 ears of two people facing each other, share the music.
Vertical Slinky, Model resonances of a tube open at one end and closed at the other.
Whirly, the sound from a twirled corrugated tube
Whirly 2, a second version of the whirly lesson.
Thermodynamics
Blow Out Your Toaster, Heat a nichrome wire to incandescence then blow it out. Vibrate it with a magnet.
Boyle-ing water, boil water at room temperature by reducing the pressure.
Burning peanut, Use the heat flow from a burning peanut to boil water and measure the energy in the peanut.
Candles in a jar, Observe candles at different levels in a jar go out one by one.
Cold Spot, A 2 meter diameter mirror is used to make an image of a block of dry ice, does the image feel cold? This is a variation of the Hot Spot Exhibit at the Exploratorium.
Conduction, Convection, Radiation, Use liquid crystal thermometers to investigate heat flow.
Feel Temperature, have people line up from hottest hands to coldest.
Hot Hands, have people line up from hottest hands to coldest.
Liquid Crystal thermometer , Use liquid crystal thermochromic material to show conduction, convection and radiation, evaporation too.
Martian water, explore the triple point of water where it freezes and boils at the same time.
Negative Temperatures,Use poker chips to explore the meaning of negative temperatures.
Solar Thermal Energy, measure the power of the sun using a liquid crystal thermometer.
Temperature Illusion, touch a cold glass of water with one hand and a hot glass with the other them try to sense the temperature of a room temperature glass. Each hand will sense a different result.
Temperature sensing, Feel the temperature of other people's hands.
Hanging Slinky, study standing waves on a long slinky hung by strings from a heavy cord.
Harmonic Phonecord, resonances of a phonecord.
Origin of Water Waves, adding oil to water changes the surface tension and smoothes out surface waves made by the wind.
Phonecord Harmonics, Explore the frequencies of the harmonics of an oscillating phonecord.
Reflections on an open end, How does sound bounce off the open end of a tube.
Slinky in hand, explore the different types of waves on a slinky.
Slow waves on a Phonecord, measure the speed of pulses on a stretched phonecord.
Tape Electromagnetic Wave, wiggle charged tapes back and forth and send and receive radio waves.
Vertical Slinky, Model resonances of a tube open at one end and closed at the other.
Waterwaves, Measuring the period, and wavelength of an ocean wave to get its speed.
Water Wave Video, watch the wave video by Andrej Zdravic.
Afterimage, Move a minimag light around in space and observe the stringlike afterimage.
Ball Bounce in a Mirror, Bounce two balls on opposite sides of a mirror, stop bouncing one ...
Binocular Vision, the view from one eye is not the same as the view from the other.
Blind spot, use a minimag light to "see" your blindspot
Crater illusion, rotate the image and make the craters into bumps
Expanding Afterimages, Look at a bright square then look at its afterimage on backgrounds at varying distances.
Find the highest note, an auditory illusion, use an Exploratorium online exhibit
Floaters, observe the inside of your eye.
Gray step , use a gray step postcard to explore this illusion
Green Bananas, Look at a yellow banana image through a form fitting cyan filter and it will look green, use a larger filter and it will look yellow.
Lego Illusion, the width of the far end of a stack of lego blocks appears to be wider than the near end.
Macula, Use a museum exhibit to see your own private shadowy shapes.
Master eye, Find out if you have a master eye by pointing at a distant object.
Moon illusion, why does the moon look larger on the horizon?
Near Hand Far Hand, One hand is twice as far away as the other does it look half as high using 2 eyes? using 1?
Nose Cone, Look through a cone and notice that depth perception is difficult.
Pinholes 1 versus 3, look though a film can with a single pinhole on one end and three on the other.
Pinhole images, explore your eye and brain and image inversion
Positive Afterimages, Look at a brightly lit scene and you can observe a positive afterimage.
Reaction Timer, measure your reaction time with a ruler.
Red/Green Look at colored photos through red and green filters.
Red/Green afterimage, Look at a bright light through red and green filters, one on each eye, then notice the colors in the afterimages.
Right and Left, explore the meaning of right and left.
Seeing your retina, Use a small dim light to see your own retina.
See your pupil, use a filmcan with a pinhole in the bottom
Size Constancy, The apparent size of an object is determined in part by its perceived distance.
Swing a Blinky , persistence of vision using moving AC neon lights
Weight Illusion, The perceived weight of an object depends on its perceived size.
Bifurcation, droplets of food color divide over and over when dropped into water.
Camera Dissection, Take apart a disposable camera.
Car Science, science through your windshield.
Ice Balloon meanders, Salt on ice balloons creates runoff that carves meandering channels.
Memory , Your memory of things past is not always accurate.
Metric Prefixes, check out the new metric prefixes, like yocto and Yotta then try the quiz
Paper Airplane Science, build a paper airplane, find its center of gravity and pressure, make it stable and controllable, measure its glide ratio.
Spinning Cylinder. Explore the stable patterns produced by a spinning PVC cylinder.
|
Scientific Explorations with Paul Doherty |
|
31 January 2001 |