### Spinning Liquid Pen

Get this pen set here (dolphin, turtle, polar bear, penguin):

From Amazon: **BUY NOW: Spinning Liquid Motion Pens**

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Spinning Liquid Pen: two immiscible fluids (three if you count the air bubble) are sorted under gravity by density with the densest on the bottom and the lightest on top. When the container is rotated, the boundary between the layers forms a parabola due to the added influence of centripetal acceleration as seen here in 240 fps slow motion. The plastic dolphin has a density between that of the two liquids so it stays at the boundary layer. A rather silly toy- but so much physics to explore here!

### Motion of Rolling Sphericons

Get these and other amazing developable rollers here:

From Etsy: **BUY NOW: Hexacon and Sphericon Rollers**

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Sphericons are unique solids that roll in such a way that every point on their surface comes in contact with the plane. Solids from the sphericon family all have one side and two edges. Each sphericon is based on an even sided regular polygon, with the basic sphericon derived from a square, and the next two possible shapes are the hexa-sphericon and octo-sphericon, each rolling with a more complicated path.

Speed cube version available here:

From Amazon; **BUY NOW: 1x1x1 cube**

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Completing the collection: the 1x1x1 cube, a silly but logical addition to any twisty cube collection!

### Curta Calculator

These vitiage items are available here, but are a bit pricey:

From eBay: **BUY NOW: Curta Calcualtor**

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Here is an amazing article about the inventor and the device by **Cliff Stoll**

Curta Calculator: before the electronic calculator there was this device that was portable, powered by hand, and could calculate to a precision of 15 decimal places! This is the Type 2 model and it was made in 1962 and still works beautifully. Demonstrated here is how to multiply two large numbers- for fun let’s pick 3803 x 32463. Although the process is not as simple as pressing buttons, the steps are intuitive: First, set in the largest number using the sliders on the side. Next we now multiply that number using each digit of the smaller number and move the top “carriage” to note the place values of each digit. Placing the carriage on 4 will multiply the side number by 1000 for each turn, so we turn the crank 3 times. Following this pattern we then place the carriage on 3 and turn the crank 8 times to multiply by 800, and finally we place the carriage on 1 and turn the crank 3 more times. The number 3803 now appears on the top silver readout, and the result, 123,456,789 is read off the top black output register. From this demonstration we see that the number of crank turns needed is just the sum of the digits of the smaller number (14 for this calculation)- some effort but better than multiplication long hand and with much less chance of mistakes! The device is cleared by lifting the carriage and swinging the clearing ring around once. Invented by Curt Herzstark and manufactured from 1947-1972, these devices are mechanical wonders with over 700 precision components.

### Shashibo Puzzle Dissected

Get this cube puzzle (in a variety of colors and patterns) here:

From Amazon: **BUY NOW: Shashibo Cube**

From Art of Play**: BUY NOW : Shashibo Geometric Art**

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Shashibo Puzzle Dissected: I cut apart one of these puzzles to better understand the geometry: it is indeed a cube dissected into 12 equal irregular tetrahedra as seen here. The embedded magnets still allow construction of the cube. Of course the symmetrically placed hinges (along with strategically placed magnets) creates the real magic of the Shashibo puzzle- a device with more that 70 geometrically interesting and aesthetic configurations including a rhombic dodecahedron as well as the cube.

### Poly acrylamide Polymer Vanishing Act

Get some of these grow-spheres here:

From Educational Innovations:** BUY NOW Growing Spheres **

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Poly-acrylamide Polymer Vanishing Act: these spheres of hydrophilic polymer have an almost identical index of refraction as that of water- thus when submersed they become invisible. Note the elasticity of these spheres from the way they bounce, while at the same time they refract their surroundings as a spherical lens. The super absorbent spheres start as hard crystals with a radius of 2mm and grow to 11mm when immersed in water. So much physics going on here!

### Jansen's Linkage Walker

Get this device here:

From engineDIY: **BUY NOW: Jansen's Linkage Walker**

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Jansen’s Linkage Walker: a mesmerizing motorized sculpture that features Jansen’s linkage- a unique leg mechanism which converts rotary motion of a crackshaft into smooth walking motion. The linkage used here was invented by artist Theo Jansen for his “strandbeest” creations which are usually a couple meters high and walk the beaches of the Netherlands powered by the wind. This kinetic sculpture is powered by two AAA batteries and comes with complete with display stand.

### Resin Art Dome Kalliiroscope

This item came from this Etsy shop:

From Etsy: **SHOP NOW: Sensory Fidgets**

A nice larger glass version is available from this trusted seller:

From PhysicsHack:** BUY NOW: Vortex Dome Kalliroscope **

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Resin Art Dome Kalliroscope: visualizing fluid flow— rheoscopic fluid allows turbulent flow to be made visible with tiny flake crystals of mica catching the light. This fidget version of the kalliroscope is well constructed from poured resin that provides a tight seal- and note that great care was taken to prevent any air bubbles into the system. Rheoscopic fluids were developed by Paul Matisse in the 1970s to allow visualization of fluid motion.

### Noble Gas Display and Tesla Coil

Get this display (Tesla Coil included!) here:

From Engineered Labs: **BUY NOW: Noble Gas Display**

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Glowing Noble Gas Collection: five noble gasses are subjected to the high frequency electric field of a miniature Tesla coil. Encased in acrylic and carefully labeled, this spectacular display collection is the creative work of Tim and Cory Marriott of Engineered Labs Protoshop LLC- and each display comes with this Tesla coil! The high frequency/high voltage field of the coil transmits energy through the thick acrylic to excite the atoms of these gases, revealing the unique color of each gas, which is actually due to a mix of photon frequencies emitted from electron energy transitions specific to each element- the basis of spectroscopy.

### Stomachion Puzzle

Get this 3-color laser cut acrylic version here:

From Kadon Enterprises: **BUY NOW: Stomachion Puzzle**

Also a very nice multicolor acyrlic version here:

From Etsy: **BUY NOW: Stomachion Puzzle**

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Learn about the 1998 discovery of the lost writings of Archimedes (and the technology used to recover them) in this TED talk.

Ancient Stomachion Puzzle: the oldest known puzzle, discovered in the writings of the great Greek physicist and mathematician Archimedes from some 2200 years ago. The puzzle is a dissection of a square into 14 polygons, where the areas of each piece are integer multiples of each other (a curious way to slice it up). In 2003 Bill Cutler showed that there are 536 district ways to configure these pieces to make the square (five are shown here), ignoring simple rotations and reflections. Swipe to see the most famous solution, attributed to Archimedes himself, that was found in an ancient manuscript discovered only in 1998- before this date historians knew the name of the puzzle, but no one knew what it looked like. Kate Jones, the maker of this particularly aesthetic version, found that when using only three colors for the polygons, there are only 6 solutions where no two pieces of the same color touch (four solutions shown here).

### Rattlesnake Eggs

Get a set here!

From Amazon:** BUY NOW Buzzing Magnet Set **

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Rattlesnake Eggs: polished barium-strontium ferrite ceramic magnets influence each other when many centimeters apart, demonstrating the well known but mysterious action at distance via magnetic fields. Sometimes sold as “buzzers” these magnets come together with multiple bounces creating a characteristic zipper sound. Many shops and online vendors incorrectly label these as hematite- a completely different substance that does not magnetize well.

### Bouillant de Franklin (Hand Boiler)

A variety of shapes and colors are available

From Educational Innovations: **BUY NOW: Hand Boilers **

From Amazon: **BUY NOW: Hand Boilers **

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Bouillant de Franklin (Hand Boiler): reversible liquid-gas phase transition device made famous by Benjamin Franklin who was one of the first to describe the physics of its operation. The boiling point of dichloromethane is slightly below body temperature - heat from a hand increases pressure in the bottom bulb pushing the green (dyed) liquid through the glass pipe to the top. A vintage handmade version from France.

### Luna Kinetic Illusion

Available in a number of colors and configurations:

From KickStarter: **Pledge NOW: Luna Kinetic by Mezmoglobe**

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Luna Kinetic Illusion: precision machined and crafted kinetic desk toy with helical motion illusion. A metal sphere seemingly defies gravity as a coil spins around it in this astonishing design by Kristoph Krisjans and the Mezmoglobe team.

### Dudeney's Dissection 3D Print

Get this set here!

From Etsy: **BUY NOW: Dudeney's Dissection 3D Print **

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Dudeney's Dissection: an equilateral triangle canbe cut (dissected) into four pieces that will then assemble into a square. This 3D printed version comes as a puzzle- fit the pieces in each of two containers- a square and a triangle, which also makes it clear the two supplied shapes are of equal area. Fun fact: It is not known if a similar three piece dissection is possible. Also called Haberdasher's problem and described in 1907 by Henry Dudeney it is the only 4 piece solution known.

### Pencil Hyperboloid

Choose your color and get one here:

From Etsy: **BUY NOW **

Hyperboloid Pencil Holder

don't forget a set of pencils:

From Amazon: **BUY NOW **

Colored Pencil Sets

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Better yet- get some thermochromic color changing pencils!

From Educational Innovations: **BUY NOW **

Heat-Sensitive Pencils

Pencil Hyperboloid: a perfect gift for any math teacher- the precisely oriented holes in this base direct 16 pencils to reveal a hyperboloid, the 3D surface traced by revolving a diagonal(skew) line, the outline of which is the conic section of the hyperbola. A doubly ruled surface for any desktop!

### LEDs as PV Cells

Need a UV laser pointer? Get 3 lasers (one of each color) for under $10:

From Amazon:** BUY NOW red+green+blue(UV) laser pointers**

LEDs are really inexpensive these days- for $10 get this assortment of 350 LEDs to experiiment with:

From Amazon: **BUY NOW: LED assortment **

*Note: this site contains affiliate links for which I may be compensated*

For well explained details of the physics see this amazing video by Steve Mould

LEDs as PV Cells: the physics of solar cells (photovoltaic cells) is the reverse process of LEDs (light emitting diodes). Shown here is a very simple circuit I soldered together- a blue LED and red LED connected. When a stream of energetic photons (from a 405nm violet laser pointer) is directed onto the blue diode it produces enough current to power and light the red diode! I saw this demo from fellow physicist @richardvandewege and had to reproduce it for my collection- check out his profile for more fantastic physics via creative demonstrations.

### Map of the Universe: 2dFGRS

Get this laser etched scuplture here:

From Etsy:** BUY NOW: 2dFGRS Crystal Sculpture**

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Map of the Universe: actual astrophysical data with 221,000 laser etched dots, each dot representing a galaxy of stars and revealing the largest scale structures of our universe. This glass cube contains a 3D mapping of galaxies using the data from the 2dF Galaxy Redshift Survey completed in 2003 which revealed the large scale clumping and voids of galaxies, the true structure of our universe out to about 2.5 billion lightyears. The 3.9 meter wide telescope took about 5 years to collect the spectra of each galaxy in two thin slices of the sky, representing about 4% of the total. The Sloan Digital Sky Survey has since expanded on this to about 40% of the sky now mapped to 12 billion lightyears. Hold and explore this mapped chunk of the universe in your own hands!