### Square Dissection Puzzles

Get these and other well made disection puzzles here:

From Etsy: **BUY NOW: Square Dissection Puzzles**

These puzzles are expertly laser cut and sold by GamesEfce. I spray-painted the pieces of mine to better show the shapes and relationships for the video.

Square Dissection Puzzles: a square can be cut (dissected) into polygons and then reassembled into other regular polygons. Shown here: an equilateral triangle, a pentagon, and a hexagon. These are the record holders for smallest number of pieces needed: triangle (4 pieces by Henry Dudeney 1902), hexagon (5 pieces Paul Busschop 1870s) and pentagon (6 pieces Robert Brodie 1891). Fun fact- It is not known if any of these records are the smallest possible, no mathematical proofs yet exist on this question.

### Nova Plexus Interlocking Puzzle

Precision machined and available in brass or stainless steel:

From Art of Play: **BUY NOW: Nova Plexus Puzzle**

Nova Plexus Puzzle: 12 identical brass rods can create 4 interlocking triangles in a perfect symmetry- look carefully and you can see that each rod is in an identical configuration with the 5 others that connect with it. Precision machined notches on the ends of the rods allow them to interlock with elastic tension such that vector sum of the 5 forces on each rod is zero- creating this astonishing geometry as the equilibrium state. Unlock the ends of any two rods and the system instantly disassembles (swipe to view process in slow motion). Invented/designed by artist and computer scientist Geoff Wyvill in 1978, this puzzle has just recently been made available for sale with a limited production run.

### Impossible Dovetail

Inexpensive versions of this "impossible box" like that in the video avaiable here:

From Amazon: **BUY NOW: Impossible Box Puzzle**

Impossible Dovetail: this impossible object is pretty common, but it is a classic, and included in my collection. If one assumes a regular dovetail joint then this construction would indeed seem impossible without cutting and gluing, but what one sees from the sides makes for misleading assumptions as this box opens easily. Swipe for reveal once you’ve thought about about possible constructions.

### Four Marble Puzzle

Get this well crafted puzzle from Creative Crafthouse here:

From Amazon: **BUY NOW Crossroads Four Marble Puzzle **

From Etsy: **BUY NOW Four Marble Puzzle **

Four Marble Puzzle: physics brain teaser- move all four marbles to their corner locations simultaneously. Each slot slopes down towards the center such that the marbles tend to stay at the center- so, how would one get them to roll outward at the same time? The solution to this puzzle (like others featured here) relies on some fun basic physics principles. Answer below and swipe to reveal solution. A beautiful and well-made puzzle from Creative Crafthouse.

### Magnetic Cube

Many colors to choose from:

From MagneticCube.com: **BUY NOW Magnetic Dice Cube **

See also the original indestructibles post: Magnetic Acrylic Rubik's Cube

Magnetic Cube: a twisty Rubik’s Cube puzzle made from 27 dice and 108 neodymium magnets. This cube includes the scrambled states and solutions of the original 3x3 Rubik’s Cube but is held together only by magnets! The magnets, in this special configuration, lock the dice together with a satisfying click upon rotation. This beautiful cube was produced by Owen Lillywhite of magneticcube.com and is based on a gfixler design posted on instructables.

### Impossible Braid

Get this nice example of mystery braid here:

From Art of Play:** BUY NOW: Impossible Braid Key Fob**

Here is a great video on how to make the mystery braid

See other **Impossible Objects** in my collection.

Mystery Braid: challenge- how can three strands be braided if both sets of ends are connected? (swipe for reveal) A new addition to my collection of “impossible objects”, this leather key fob is braided from a single piece of leather, constructed by making two parallel slits but not cutting the ends. The solution is well known to those in the field of leatherwork- due to a twist of topology it’s possible to make this braid if the number of left strand over right crossings equals the times the right strand crosses over the left. Four strands braided this way is not mathematically possible, but 3, 5, or any odd number can be done!

### Pentominoes 3 Color Challenge

@physicsfun exclusive design- available only from **STEMCell Science**:

From Etsy: **BUY NOW: 3 Color Pentominoes Puzzle**

Pentominoes 3 Color Challenge: fit all 12 pentominoes into a 6x10 rectangle such that no two identically colored pieces touch. Pentominoes are the set of all 12 possible arrangements of five identical squares joined edge to edge. Since 5x12=60, the pentominoes can tile a 6 x 10 rectangle with no gaps (there are 2339 ways to do this- yet even finding one solution is quite difficult). Adding the 3 color challenge reduces the number of possible solutions to just this one shown here! Made from laser cut acrylic and wood- and now available for the first time in a limited production run.

### Frabjous Geometric Sculpture Puzzle

Get one here- five colors to choose from:

From MoMath: BUY NOW: Frabjous Sculpture Puzzle

Frabjous Geometric Sculpture Puzzle: 30 identical laser cut acrylic pieces interlock into 12 interconnected five point stars (each with a spiral vortex center) in this puzzle based of the Frabjous sculpture by artist and professor of mathematics George Hart (Prof. Hart is now on Instagram, follow him at @george.hart.sculptor to see more of his amazing work.) Note that if one connects the tips of the stars one gets the outline of a dodecahedron, with its 30 edges and 12 sides, and if one considers the face planes of the linked pentagrams the underlying shape is a polyhedron called the “great rhombic triacontahedron”. A year or so ago I got to visit the National Museum of Mathematics in NYC where I bought this puzzle in the @momath1 museum shop. This puzzle was great fun to assemble- buy one to support this inspirational museum, and make a great sculpture for your bookshelf!

### Matsuyama's Paradox

Get this and other amazing math puzzles here:

From Etsy: **BUY NOW: Missing Square Puzzle**

Matsuyama’s Paradox: dissect a large square in to four equal quadrilaterals, rotate and reassemble- to find a small square is missing! Where did the additional area come from? Fun math involved in the design of this puzzle, which illustrates how the concept of area can often challenge our intuitions. Swipe to compare the two assemblies. A precision crafted puzzle by Jeux Efcé game shop. Wikipedia has good details: Missing square puzzle.

### Balance Stacking Sculpture

Another wonderful desing by BinDesign- get one here in black or natural wood:

From Etsy: **BUY NOW: Bin Design Balancer Puzzle**

Balance Stacking Sculpture: a series of torques in unstable equilibrium complete this Calder-esque structure. As each component is added its weighted end balances all the others before it, with the initial small piece weighing about a gram or so. Remove the end piece and the whole structure comes down. Another wonderful design by artist Bin Xu.

### TrueBalance

Get the full version (8 disks made of wood) or the mini (6 disks, blue or red plastic):

From Amazon: **BUY NOW TrueBalance Coordination Puzzle **

TrueBalance: coordination challenge puzzle- get the six disks, connected by bearing swivels, into a vertical stack by only tilting the handle. Harder than it looks to get each disk’s center of mass above the one below at the same time into the unstable equilibrium final state. The swivels constrain the system, limiting the degrees of freedom, and allowing strange and interesting motion. Kinetic art as a toy!

### Impossible Wallet

Available here:

From Amazon: **BUY NOW Magic Wallet **

From eBay: **BUY NOW Magic Wallet**

Impossible Wallet: this pocketbook has a special double hinge that allows the wallet to be opened from either side, and leads to some rather nonintuitive consequences. Note that once inserted, the bill shows the same face independent of which way the wallet is opened. The construction of this magic (or flip) wallet is similar to the famous Jacob's Ladder toy.

### Pythagorean Puzzle

Available here:

From Creative Crafthouse:** BUY NOW Pythagorean Puzzle**

Pythagorean Puzzle: a proof, in physical form, of one of the most famous equations concerning the sides of any right triangle. The area of a square with side c of the hypotenuse is indeed equal to the sum of the areas of the squares of side a and b. This kit also allows at least two other ways to prove this theorem named after the famous Greek mathematician from 500 BC. One of the most used formulas when calculating vectors in physics classes ?

### Raketti Puzzle

Versions of this puzzle avaioable fron these sources:

From Etsy: **BUY NOW Raketti Physics Puzzle **

From eBay: **BUY NOW Raketti Physics Brain Teaser **

Raketti Puzzle: physics brain teaser- the challenge is to remove the cone topped cylinder from the hole without touching the bottom container (no fair using sticky tape or such). It can be done in a matter of seconds! The solution to this puzzle (like others featured here) relies on some fun physics principles. Answer below and swipe to reveal solution.

### Aristotle's Wheel Paradox

Get this demonstration puzzle here:

From Etsy: **BUY NOW: Aristotle's Wheel**

WIkipedia has some details on the Wheel "Paradox"

Aristotle’s Wheel “Paradox”: How does the smaller attached disk travel the same length as the larger one if both disks only make one full rotation? Note the shorter path of the smaller disk, if rolled on its own. This beautifully made demonstration depicts an issue of geometry and motion that perplexed the best minds of humanity for 2000 years. The ancients knew the formula for circumference, and C=2πR for the large disk is clearly greater than C=2πr for the smaller- so how could the smaller disk, rotated once, still travel the distance of the larger one if attached? The great Galileo even offered a solution to the problem in his book Two New Sciences, where he approximated the situation as concentric hexagons and considered the limit as the number of sides increased. So what is the best answer to make sense of this situation?

### Sphere Sticks Geometric Puzzle

Get this affordable and amazing puzzle here:

From Etsy: **BUY NOW: Sphere Sticks**

Sphere Sticks Puzzle: 30 identical wood pieces, each with two notches as shown, can create 12 interlocking pentagons in a perfect symmetry- look carefully and you can see that each rod is in an identical configuration with the 4 others that connect with it. Precision cut notches on the rods allow them to interlock with elastic tension such that vector sum of the 4 forces sum to zero in this tensegrity type equilibrium. The dodecahedron, with its 30 edges and 12 sides, is the basis of this puzzle sculpture.

### Elastic Equilibrium Puzzle

Get this puzzle here:

From Amazon: **BUY NOW: Atomic Cherry Puzzle**

Elastic Equilibrium Puzzle: six spheres held together by three plastic springs. When assembled each sphere exerts the same force on its four neighboring spheres, producing this equilibrium state only if all six spheres are used to balance all the forces. A fun configuration to analyze in a 1st year physics course- the Atomic Cherry by Brainwright puzzles.