What is a 20 sided dice called?

As tabletop gamers, we all know the iconic dice used in Dungeons & Dragons and other RPGs – the one with 20 triangular faces that rolls and tumbles with satisfying clatter. That‘s right…the twenty-sided die, also known as the d20.

But what exactly makes the d20 so special mathematically, why did it become the most popular RPG die, and what is the story behind its ancient origins and adoption into modern gaming? As a lifelong D&D player, I wanted to share some of the fascinating facts I‘ve picked up over the years about the icosahedral twenty-sider we know and love.

The Geometric Elegance of the Icosahedron

The secret behind the d20 is that its shape forms an icosahedron, one of the five perfect Platonic solids. What exactly does that mean?

Platonic solids are 3D geometric shapes where each face is a regular polygon, and the same number of faces meet at each vertex. There are only five such shapes that meet these criteria – the tetrahedron (4 triangle faces), cube (6 square faces), octahedron (8 triangle faces), dodecahedron (12 pentagon faces), and finally the icosahedron, with its 20 equilateral triangle faces.

Here‘s some cool mathematical properties that emerge from the icosahedron structure:

• It has 20 identical equilateral triangle faces
• There are 12 vertices where 5 triangles meet
• 30 edges connect the vertices and faces
• When inscribed in a sphere, each vertex touches the sphere
• It has 52 rotational symmetries

In fact, the icosahedron maximizes the volume for surface area ratio compared to other Platonic solids. This efficiency and symmetry contributes to its appeal!

No wonder ancient philosophers and mathematicians were fascinated by these shapes. The d20 retains the perfect icosahedral form – which is why it feels so balanced and rolls so cleanly.

Ancient Twenty-Siders – For Oracles, Not Games

While we now associate 20-sided dice with RPGs and gaming, some of the earliest known d20s come from ancient civilizations where they served a completely different purpose – divination and fortune telling!

Archeologists have uncovered icosahedral dice made of materials like stone, glass, and gemstones dating back thousands of years:

• The Roman 20-sided die (c.2nd-4th century CE) pictured below was made of glass and discovered in the ruins of Antioch. The Greek letters were likely used to reference an oracle text.

• This Egyptian d20 (c. 304-30 BCE) predates even the Romans. Carved from serpentine, the faces are inscribed with Greek letters and it remains in amazing condition.

• Mesopotamian icosahedra (c. 1800 BCE) were excavated from the ancient city of Tell Asmar and made of hematite, limestone and marble.

Scholars believe these cultures used 20-sided dice to randomly select a symbol or verse to consult for guidance, similar to drawing lots or sticks. The icosahedron provided a convenient and fair way to leave one‘s fate up to the gods!

Of course, we have no records of how the ancients actually played games with dice. But it‘s clear this shape held significance for ritual and divination centuries before becoming a gaming staple.

Reviving the d20 for Wargames and D&D

The icosahedron largely faded from view through the Middle Ages and Renaissance periods in Europe. But it rolled back into popularity thanks to an English mathematician named Sir Thomas Brisbane. In 1833, he published a taxonomy of the Kepler-Poinsot polyhedra which included the icosahedron, sparking new interest in this shape among academics.

Not long after, the fledgling tabletop wargaming community adopted polyhedral dice like the d20 for simulating probabilistic chance in battle outcomes. The first modern wargame rulebook, "Little Wars" by H.G. Wells in 1913, specifically promoted the d20 as an improvement over existing systems.

Wells wrote:

The game has grown out of a small war game we contrived in the days when smokeless powder was undreamed of…and from that we developed the ammunition and shooting side until there grew under our hands a body of rules and equivalents that made what we may call a game for two players or two sides. Hitherto war games have been either for one person alone, one general, planning his campaign, or else have been played by a very large number of players…. This game we tried over with varying fortunes for some years before we published it.

As wargaming proliferated through the 1900s, so did the use of polyhedral dice like the d20. But it took the 1970s creativity of Gary Gygax and Dave Arneson to propel the d20 from obscurity into lasting fame. When developing the original Dungeons & Dragons – and inventing the concept of tabletop RPGs – they adapted the offbeat dice from wargames to use in their fantasy game.

Players loved how throwing these odd shapes added an element of randomness and chance to their experience adventuring in dungeons full of dragons and magic. And the d20, with its probability spread ideal for generating ability scores, attack rolls, and saving throws, quickly became the workhorse die that drove much of the gameplay.

Soon D&D exploded in popularity, exposing millions of gamers to polyhedral dice through the 1980s and 1990s. The rest is history – today the d20 remains not just the most recognizable die, but a symbol of tabletop RPGs as a whole.

Probability Curves and Game Design

We‘ve talked about the physical appeal of the d20 shape, but let‘s discuss the probabilities and math that make it so useful for RPGs.

Each of the 20 faces has an equal 1-in-20 chance of landing face-up when rolled. This means over a large number of rolls, you‘ll see each number or value appear close to 5% of the time:

Compare this to a common 6-sided cube die:

As you can see, the d6 probability distribution is uneven, with middle values of 3-4 coming up more often. The d20 provides a flatter curve with better spread.

Game designers prefer the high variability and lower potential streakiness of the d20 for key gameplay mechanics like ability checks, attack rolls, and saving throws. The more granular range of results from 1 to 20 allows implementing finer gradients of challenge difficulty classes (DCs) for scenarios.

Other common RPG dice like d10s and d12s offer less overall randomness:

• The d10 has a bell curve distribution focused in the middle that repeats every 10 rolls.

• With only 12 possibilities, the d12 provides limited variability.

Thus the icosahedral twenty-sider‘s high number of faces, equal probability distribution, and nice large number range helped cement it as the go-to die for d20 system games.

Collecting Beautiful, Exotic d20s

After learning so much about the d20, I couldn‘t resist starting a collection of gorgeous artistic, luxury dice beyond the standard plastic sets. Part of the appeal is the creativity dice makers show in crafting d20s out of different materials:

• Heavy metal dice like zinc, copper, and brass that feel substantial rolling in your hand and ping loudly on the table. I‘m partial to the steampunk aesthetic of gears, tubing, and patina.

• Semiprecious gemstone dice made of tiger‘s eye, malachite, amethyst, and other vibrant stones that shine when lit. My bloodstone dice look like swirling red clouds.

• Wood dice with natural woodgrain patterns – maple burl, ebony, and pink ivory are beautiful choices. Just beware of any sealing oils interfering with fair rolls.

• Hand engraved dice etched with ornate filigreed designs or custom logos/symbols. An artist engraved my wife‘s druid character and symbols on a set of bronze dice as a gift.

• Large engraved dice up to 2 inches across! Not necessarily fair for games, but fun display pieces.

Beyond materials, artists have pushed creative boundaries with novel d20 designs:

• Dice with elaborate internal floaters that move inside as you roll them.

• Glowing fluorescent dice charged by light sources.

• Swirling cosmic nebula and galaxy designs that look like glimpses of space.

• Detailed painted scene dice that reveal images across multiple faces.

Part of the joy of collecting dice is appreciating both the mathematical perfection and artistic expression. A beautiful twenty-sider can be functional, yet visually captivating too.

When Good Dice Go Bad – Dealing with Cheaters

Sadly, wherever games of chance and money co-mingle, cheaters emerge trying to beat the odds with loaded dice. Since RPGs use dice to represent random chance, some dishonorable players succumb to the temptation to introduce gaffed or weighted dice:

• Carefully shaving corners alters the center of gravity and distribution of mass within a die. Casinos watch for unusually rounded dice.

• Plugging a heavy material into one face through a tiny drilled hole weights a certain side to come up more often.

• Interior stickers, paint drops, or bubbles can add mass to one side without being obvious. Fluorescing epoxy resins under UV can reveal these tricks.

• Two piece construction with heavier or magnetic halves allows creating high and low sides. But telltale seams often give these away.

Game stores and convention organizers know to watch for cheaters. But home games between friends rely on trust and honor. As tempting as an unfair advantage may seem, true players understand you have to take the bad rolls alongside the critical hits to earn glory honestly. Karma has a way of correcting those who try to beat the odds indefinitely!

And casinos have developed high tech dice screening tools to isolate and quickly identify unfair dice in high stakes games before they cause trouble:

• Precision balancing devices can detect tiny differences in center of gravity distribution between sides.

• Film and x-ray imaging reveals interior alterations, weights, and defects.

• MRI density scanning maps the magnetic properties throughout a die seeking anomalies.

• Optical surface scanning under different light spectra highlights modifications.

While home games likely don‘t require such paranoid precautions, it‘s comforting casinos take dice integrity seriously, given the vast sums at stake in games like craps.

Quirky Dice Superstitions that Guide Our Fate

Over years of racing friends through dungeons and slaying dragons, I‘ve observed dice superstitions and traditions among RPG players that run the gamut from playful to nearly religious! We game geeks are a superstitious lot regarding our mystical polyhedra. Some quirky yet common habits include:

• Always rolling the same "hot" dice that have scored critical hits previously. Retiring "cold" dice that roll poorly to the "dice jail."

• Gently blowing on dice before rolling to "fill them luck." I once knew a guy who would huff deeply and exhale massively!

• Insisting on rotating dice just so before rolling, like a basketball player‘s free throw rituals. Dice rack position and order is serious business.

• Never allowing others to touch your personal dice or use them in play, lest their bad mojo rubs off! Dice are intimate like toothbrushes.

• Cleaning dice before a big game. Some use holy water, cleansing smoke, moonlight, or other spiritual rituals to remove accumulated bad karma.

• Praying to gods or offering obeisance for favor. One friend would say "Show me some love!" before every big roll, without fail.

• Chanting, shaking methods, taking dice to special locations or items to "charge their luck". The variations are endless.

Now as a man of science, I take a dim view of magical thinking and rituals. But I have to admit – indulging small superstitions gives us a greater sense of control and confidence. And that positive attitude can become a self-fulfilling prophecy! So if it works for you, embrace the quirky habits that enhance your enjoyment of rolling dice. Just don‘t let them slow down the game!

Advice for New RPG Players With Their First d20

As a veteran RPG gamer, let me share some tips for new players who are excited to roll their very first 20-sided die:

• Don‘t get overwhelmed by all the dice options at first. Just get a basic 7 die RPG set with d4, d6, d8, d10, d%, d12, and most importantly, the d20!

• Spend more time developing your character background and abilities before you dive into complicated mechanics. Focus on story.

• Learn the key checks and rolls like attacks, saves, and skill tests that use your trusty d20. Write these on your sheet!

• Use a pencil or paint pen to mark the key target numbers like 15, 17, 19, 20 on your d20 so they stand out for important rolls.

• Before big rolls, consider your odds and probability range. Don‘t leave your fate entirely up to chance.

• Don‘t feel compelled to stick to gaming tropes. Take creative license telling the story when you succeed or fail!

• Have spare dice handy for rolling large numbers, and keep your main d20 within quick reach. Designate dice spots.

• Share in celebrating your friend‘s awesome rolls, and laugh together when dice betray you both. Stay positive!

Most importantly, have fun and embrace the excitement of letting fate decide! The randomness of dice rolls tells memorable stories. Let your d20 open new adventures!

Timeless Twenty-Siders: The Past, Present, and Future of the d20

Our wanderings through the history, mathematics, and lore of the venerable twenty-sided die have illuminated why it remains so beloved today. Since ancient times, its unique icosahedral form has dazzled, its useful probabilities have powered games of chance, and its imaginative imprint on culture has inspired.

We‘ve seen how the d20 evolved from a tool for divination to a cornerstone of RPGs and an icon of geekdom. It reminds us of childhood stories, tense dice rolls shared with friends, and the endless potential of probability.

Even in today‘s virtual worlds, tangible dice like the d20 retain their magic. As long as quests need vanquishing and foes need slaying across tabletops, the twenty-sider will roll on into future generations. So grab your trusted d20, embark on bold quests, and let the dice tell memorable tales! Just beware malformed dice and temper superstitions, lest the randomness of fate teach a harsh lesson. But with wisdom and camaraderie, the d20 shall remain by your side, a timeless icon of adventure.