Impossible Objects Explained

Quick answer: an impossible object is a puzzle you explain rather than solve. It appears to have been assembled in a way that could not have happened, and the challenge is working out how it was actually made. Some come apart and some genuinely never will.

Best for: people who enjoy wondering, and anyone who wants an object on their desk that makes visitors pick it up.

Most mechanical puzzles ask you to do something. Take this apart, build this shape, get this open.

An impossible object asks you a question instead, and the question is not how to open it. It is how on earth it was made.

What Is an Impossible Object?

An object whose construction appears to violate something obvious about physics or geometry.

An arrow through a bottleneck narrower than its head. A joint whose two halves could not have been slid together in any direction. A bolt inside a sealed glass with no opening large enough to admit it. Nothing about the object is hidden, which is exactly what makes it uncomfortable to look at.

They are one of the seven categories in the guide to mechanical puzzles, and the odd one out, because for many of them there is no solving action available at all.

How Do Impossible Objects Work?

Broadly three ways, and knowing them spoils nothing, because identifying which one applies to a particular object is the puzzle.

Something was once flexible. Wood can be soaked, compressed or steamed, and will return to shape afterwards. A great many impossible bottles rely on this.

Something was assembled through a route you have not considered. The classic case, and the one that produces the best reaction, because the move is usually available in plain sight once seen. Angles that look square often are not.

Something was built in place. The object was never assembled at all in the way you are imagining, because part of it was formed or finished after the rest was positioned.

What Is the Impossible Dovetail?

The most famous of them, and the one worth owning.

A dovetail joint is a woodworking joint with angled tails that slide together in one direction and lock against being pulled in any other. An impossible dovetail appears to have those tails on two faces at once, which would mean the two halves must slide together along two different axes simultaneously. That cannot happen, and the joint is clearly there.

Our Impossible Dovetail Box is a working version with a compartment inside, so it is also a box you can open. We explain the illusion in the dovetail article deliberately without revealing the mechanism, because an impossible object you have been told the answer to is just an object.

What Is a Dissection Paradox?

The flat cousin of the impossible object, and arguably the purest example of the whole idea.

Take a shape, cut it into pieces, rearrange them, and end up with the same shape plus a hole, or minus one square, or somehow larger than you started. The pieces are all present and none has changed size. The best-known versions date back well over a century and they still catch people, including people who know exactly what they are looking at.

The resolution is always the same in kind: a line that appears straight is very slightly not, and the error accumulated across the whole figure is precisely the area that seems to have appeared or vanished. Knowing this does not help you see it, which is why the effect survives explanation better than almost any other illusion.

Which Impossible Objects Do You Sell?

Three, which is more than we have in several of the other categories.

Impossible Dovetail Box is the classic, described above.

Newton's Gravity Defying Puzzle balances a rocket on its base, and your task is to remove the rocket without touching the base. It looks completely impossible, which is the point, and the answer is an idea rather than a trick of handling.

Infinity Chocolate is a geometric dissection illusion: rearrange the pieces in a particular sequence and a square appears to be created from nothing. It belongs to a family of mathematical dissection paradoxes that have been puzzling people for well over a century, and it is the most immediately convincing thing on this list.

What Is an Impossible Bottle?

The most recognisable form, and the one most likely to be homemade.

A sealed glass bottle containing something that plainly will not fit through the neck: a deck of cards, a pair of scissors, a tennis ball, a padlock. Nothing is glued and the bottle is intact, which you can usually verify by looking.

Most rely on one of two routes. Either the object went in flexible and recovered its shape inside, or it went in disassembled and was reassembled through the neck with tools, which is a genuine craft and takes practice. The best ones use an object that cannot plausibly do either, which is what separates a clever bottle from a merely surprising one.

They are a popular thing to make rather than buy, and a well-made one is usually a gift from somebody who built it, which is part of their charm.

Why Do They Work So Well on a Desk?

Because they do not require anything of the person looking at them.

A burr on a desk is a commitment: picking it up means an hour you may not have. An impossible object asks for five seconds and a raised eyebrow, and it keeps working on everyone who sees it rather than being used up by the first solver. That makes it the best category for an office, which is covered in gifts for coworkers.

There is more on the form at explorepuzzles, these sit in collectible puzzles because they get kept rather than solved and shelved, and the wider range is in mechanical puzzles.

Frequently Asked Questions

What is an impossible object?

A puzzle whose construction appears to break physics or geometry, such as an arrow through a bottleneck narrower than its head. The challenge is explaining how it was made rather than taking it apart, and some cannot be disassembled at all.

How is an impossible dovetail made?

It appears to have angled tails on two faces at once, which would require the halves to slide together along two axes simultaneously. The resolution involves an assumption about the geometry that is not true, and we deliberately do not spell it out, because being told the answer ends the puzzle permanently.

Can impossible objects be taken apart?

Some can and some genuinely cannot. Those built around a material that was temporarily flexible, or finished in place, may be permanently assembled. Others only look sealed, and the solving action is discovering that they are not.

Are impossible objects good gifts?

Unusually so, because they need nothing from the recipient. A difficult puzzle is an obligation; an impossible object works in five seconds and keeps working on everyone who sees it, which makes it well suited to a desk or an office.