World-Changing Inventions

I(ndigo) Would Dye 4 U

Indigo is more than just a color and a prefix for the popular folk-rock duo Girls. It’s actually a natural dye extracted from plants that is now commonly used to color your blue jeans. Once upon a time, however, blue dyes were quite rare, and the process for extracting indigo ultimately proved to be an important discovery in textile history. Read on to learn more!

Made from the Best Indigofera Juice on Earth

Though indigo dye can be derived from a variety of plants, it is most commonly obtained from those in the Indigofera genus, especially Indigofera tinctoria—hence the name. These plants can be found in abundance throughout Asia and the Indian subcontinent, and it is therefore unsurprising that ancient Indians were the first to make extensive use of indigo dye.

The surprisingly pink Indigofera tinctoria plant.

The surprisingly pink Indigofera tinctoria plant.

I. tinctoria was first domesticated in India, and the colorant derived from it is amongst the oldest used for textile dyeing and printing. After it rose to prominence in India, indigo became common in what are now China, Japan, and other Asia nations.

India was not only the primary center for the actual, physical act of indigo dyeing in the ancient world, it was also the primary supplier of the pigment to Europe, dating as far back as the Greco-Roman days. In ancient Greece and Rome, indigo dye and anything dyed with indigo were considered luxury products. India is so closely associated with the indigo trade, in fact, that the Greek word for the dye—indikόn—literally means “Indian”. Those lazy Romans reduced it to indicum, and the even lazier English eventually turned it into “indigo.”

Cuneiform tablets from the 7th century BCE provide a recipe for dyeing wool with indigo, showing just how far back the practice dates. (Though it likely goes back even further than that.) Ancient Romans used it for painting and as an ingredient in medicines and cosmetics. In the Middle Ages, a chemically-identical dye derived from the woad plant was used to mimic indigo dye, but true indigo was still viewed as superior and remained a luxury item.

Indigo from India To Go

This remained more or less the case until the late 1400s, when Portuguese explorer Vasco “Grande Vasco” de Gama “discovered” a sea route to India, opening up direct trade between the Indian and European markets and cutting out those pesky Persian and Greek middlemen who had driven up prices.

Expanding European empires of the day soon established numerous indigo plantations in their tropical territories to keep up with growing demand for the now-inexpensive dye. Jamaica, the Virgin Islands, and what is now South Carolina all had expansive indigo fields during this period. Those buzzkills in France and Germany quickly outlawed imported indigo to protect their struggling local woad dye industries.

Natural indigo continued to be massively popular for centuries to come. In 1897, over 2,700 square miles (7,000 square kilometers) of farmland worldwide were used to grow indigo-producing plants—nearly three times the size of the nation of Luxembourg. Over 19,000 tons of indigo were produced from these and other plant sources.

Indigoing Down

With continuing advances in organic chemistry came synthetic indigo pigments. By 1914, production from natural sources was down to a mere 1,000 tons worldwide. As of 2002, worldwide production of synthetic indigo had topped 17,000 tons.

Photo credit: museumdetoulouse via / CC BY

Historical Science & Technology

The Iron Bridge: The World’s First Iron Arch Bridge

Clearly, clever names for things were not a priority back in the 18th century CE, elsewise the world’s first cast iron arch bridge would be known as something a little less on the nose than the Iron Bridge. But those were simpler times. Join us, won’t you, as we take a historical journey back to Shropshire, England, in the late 1700s.

Spanning the River Severn

Can we pause for a moment to note how much cooler “the River Severn” sounds than “the Severn River”? Good ol’ Britons and their classy syntax. Anyway, at that time, Shropshire was a major industrial center thanks to its proximity to coal mines. The River Severn was a key trading route, but also a barrier to travel, as the nearest bridge was some two miles away.

In 1773, architect and Shropshire native Thomas “Big Tommy” Farnolls Pritchard wrote to John “Big John” Wilkinson, the ironmaster of nearby Broseley, suggesting the construction of a bridge across the River Severn. Pritchard had the skills to design the bridge, Wilkinson had the skills to build it.

Local newspapers took up the cause and helped champion the project, and by 1775, nearly four thousand pounds to put toward the project had been raised via subscription. In March 1776, the project received Royal Assent, but no satisfactory proposal for actually building the bridge was made until 1777.

Iron Bridge

The Iron Bridge as it looks today. (Pretty much the same as it always did.)

Because the Severn saw a lot of boat traffic, and was at the bottom of a fairly deep gorge, any bridge crossing it would need to be a single-span job, and be high enough to allow the tall ships used in those days to pass under it. The steep sides of the gorge were somewhat unstable, making constructing any type of bridge difficult.

In December 1777, just a month after construction had begun, Pritchard died following a prolonged illness. However, the plans for the bridge had been completed and construction continued. Masonry and abutments were completed in 1778, with ribs fitted into place in early 1779. The first span crossed the River Severn in July 1779. The Iron Bridge was opened to traffic on New Year’s Day 1781.

The Iron Bridge Today

Apart from several temporary closures for maintenance and repairs, the Iron Bridge remained open and in use from 1781 until 1923. At that time, the bridge was closed due to concerns that its massive weight, combined with the weight of vehicles crossing it, would prove unsafe. It remained closed to vehicular traffic until 1934, when a project to remove unnecessary “dead weight”, such as the all-metal deck, was completed.

The Iron Bridge had been built at a total cost of approximately £6,000. A restoration project was completed between 1972 and 1975 at a cost of £147,000. (Neither figure is adjusted for inflation.) It remains open and in use to this day.

Photo credit: Charles D P Miller via / CC BY

Important People, Important Discoveries

Laying Down the Law(s) with Big Joe Gay-Lussac

The deceptively-named Gay-Lussac’s Law is actually more or less two laws, both concerning the properties of gases—and one of them wasn’t actually discovered by Gay-Lussac. When Gay-Lussac’s Law is invoked these days, it is usually in reference to the French chemist’s first notable discovery regarding the combining of volumes (the one he did discover). No matter what anyone, scientist or otherwise, tells you, however, don’t turn your back on Gay-Lussac’s Law, Part II—it’s just as important and twice as dangerous!

Gay-Lussac’s Law of Combining Volumes

“The ratio between the volumes of reactant gases and the products can be expressed in simple whole numbers.” – Joseph Louis Gay-Lussac, 1808

Gay-Lussac discovered that, for example, two volumes of hydrogen combined with one volume of oxygen would react to create one volume of gaseous water.

Gay-Lussac's plaque in the Chemistry Hall of Fame.

Gay-Lussac’s plaque in the Chemistry Hall of Fame.

Building on Big Joe’s findings, contemporary Italian scientist (deep breath) Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto, more succinctly-known as Amedeo Avogadro, developed Avogadro’s Law, which states that, at equal temperature and pressure, equal volumes of gas would contain equal numbers of molecules.

Avogadro’s Law as not widely accepted by chemists until a third dude got involved. Italian chemist Stanislao Cannizzaro convinced the First International Chemical Congress of 1860 of Avogadro’s findings’ accuracy.

Guy-Lussac’s Law of Pressure-Temperature (In Your Face, Amontons)

Though it’s commonly referred to Amontons’s Law of Pressure-Temperature, this one is pure Gay-Lussac. Okay, that’s totally not true. In 1702, Guillaume Amontons discovered the relationship betwixt the pressure of a fixed mass of gas at constant volume and its temperature. Amontons’s Law states that:

“The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature.”

In essence, if a gas’s temperature increases, and its mass and volume are held constant, then so, too, will its pressure increase. Mathematically, this law can be expressed in a simple formula that is nonetheless still complex to type out here.

Anyway, Gay-Lussac got his name amended to Amonton’s Law round about 1802, when he expanded on Amontons’ findings with additional research on other gases that were unavailable to the original researcher due to the technical limitations of the era.

Photo credit: Leo Reynolds via / CC BY-NC-SA

Historical Science & Technology, Important People, Important Discoveries, Science

In Brief: Astronomy in the Renaissance

Thanks to the Teenage Mutant Ninja Turtles, among other things, the Renaissance period is perhaps best known for its art and culture. But science went through a real Renaissance during the Renaissance as well. Astronomy, in particular, was a field that saw a number of significant discoveries.

Astronaissance? Renaisstronomy?

As everyone knows, astronomy in the pre-Renaissance Middle Ages was based on Ptolemy’s geocentric model (i.e., Earth is the center of the universe). It is highly unlikely, however, that many astronomers of the Middle Ages had actually read Ptolemy’s writings. Derivations of Ptolemy’s work were more common points of reference, including a series of textbooks known collectively as the Theorica Planetarum—roughly translated, “Planetary Theory”.


To predict planetary motion across the heavens, Renaissance astronomers utilized the Alfonsine Tables. These tables were based on models presented in Ptolemy’s Almagest, but incorporated a number of modifications developed by later stargazers.

Round about 1450 CE, Austrian astronomer Georg “Gorgeous George” von Peuerbach took up a lecturer’s position at the University of Vienna, in the heart of the land of tiny sausages. A student of Peuerbach’s with the name of a dinosaur discovered in Montana, Regiomontanus, collected lecture notes and published them as the Theoricae Novae Planetarum in the 1470s. This “New Planetary Theory” then became the go-to textbook for advanced astronomy.

In 1496, the Epitome of the Almagest, a work begun by Peuerbach and completed by Regiomontanus after his mentor’s death, was published. A summary of, commentary on, and companion piece to Ptolemy’s earlier work, its publication gave many scientists across Europe their first exposure the latest advances in Ptolemaic astronomy.

Copernicus Drops the Mic


Nicolas “Big Nick” Copernicus was the first of the New Wave of Renaissance Astronomers, taught with the Theoricae Novae Planetarum, to sign with a major label. In the early 1510s, Copernicus began to research a wild new theory—that the Earth revolves around the Sun!

For the rest of his days, Big Nick attempted to prove heliocentrism via a mathematical proof. His magnum opus, De Revolutionibus Orbium Coelestium (or “On the Revolutions of the Heavenly Spheres”), was finally published in 1543 as he was literally on his deathbed. Though the book proved that the sun, not the Earth, is the center of our solar system, Copernicus’ work is not as revolutionary as it is often deemed. The latter scientist’s writing is really more of an extension of the latter’s, as Copernicus follows Ptolemy’s methods and order of presentation to deduce a logical extension of and conclusion to the Almagest.

Photo credit: Norman B. Leventhal Map Center at the BPL via / CC BY

Important People, Important Discoveries, Technology

It’s A Gas: The History of Neon Lighting

What would the nighttime world be without neon lighting? Boring as heck, that’s what! We all know that neon lights get their name from the electrified neon gas inside them, but how did anyone figure out that that was a thing? Who’s bright idea was the neon light?

Is this a little too on the nose?

Is this a little too on the nose?

Ramsay & Travers: Gas Scientists

Neon was discovered in the Earth’s atmosphere by William “Big Bill” Ramsay and Morris William “Smaller but Still Quite Big Bill” Travers. After the duo had successfully extracted pure neon from the atmosphere, they began exploring its properties using a Geissler tube. (These electrical gas-discharge tubes were similar to those used in modern neon signs.)

Travers wrote of their experiments, “…the blaze of crimson light from the tube told its own story, and was a sight to dwell upon and never forget.” Producing colored light (or “spectral lines”) via electrical gas discharge was a well-known practice at the time, but was then only used to identify the gas in question. The intensity of light created by electrified neon was unlike anything ever seen by science to that point.

Ride the Lighting

Almost immediately, illuminated neon tubes were being produced for use both as scientific instruments and as novelties. Pure neon gas was still quite rare, however, and the potential for its use as a light source was not widely researched. Other, similar technologies used nitrogen or carbon dioxide as an illuminating medium, and found moderate success in the United States in the late 1800s and early 1900s.

In 1902, a company owned French engineer and inventory Georges “Gorgeous George” Claude began producing purified neon in mass quantities, as the gas was a natural byproduct of their air liquefaction process. Using this gas, Claude built two 39-foot long, bright red neon tubes for display at the Paris Motor Show.

In creating the giant, glowing neon tubes, Claude more or less invented the neon lighting industry. He was granted a US patent for the design of his gas-discharge electrodes, a patent that gave Claude Neon Lights a monopoly on neon lighting in the United States until the 1930s. Claude later pioneered the use of other gases that, mixed with neon, would produce colors that electrified neon alone could not.

Modern neon lights are not much different from Claude’s massive prototypes from over 110 years ago, though today’s neon tubes can be as long as 98 feet. In your face, Georges!

Photo credit: Toby Dickens via / CC BY-NC-SA