10 Things That Were Invented Twice


History is filled with the names of inventors like Nikola Tesla, Thomas Edison, Sir Isaac Newton, and Dmitri Mendeleev. Some of these names are of interest because they’re examples of the seemingly not-so-rare event of simultaneous invention. This event is defined as an invention that is independently researched, invented, or discovered by two or more people. 

From calculus and the lightning rod to the polio vaccine and plastic, here are 10 things that were invented twice.

10. Calculus

Sir Isaac Newton and Gottfried Leibniz both invented (or discovered, if you’d prefer) calculus in the 1600s. Today Newton is famous for igniting the scientific revolution of the 17th century. He was a physicist, mathematician, and philosopher. 

Gottfried Leibniz, a German man born in 1646, was also a mathematician and philosopher. He’s credited with many contributions to Metaphysics and Logic. These two men created calculus, and they did it wholly independently of one another around the same time. 

Upon its discovery, calculus was considered a wholly new invention within the realm of mathematics, but the foundation for it was actually forged by pioneers like Kepler, Archimides, Diophantus, Fibonacci, and Ptolemy. 

If Newton and Leibniz hadn’t discovered calculus in the 1600s, someone, somewhere, somewhen would have stumbled upon it. At the time of calculus’ discovery, however, Newton actually accused Leibniz of plagiarism, claiming that he had copied his research and methodology. While Newton discovered calculus (a term which didn’t become the norm until Leibniz published his own paper) using a geometric approach while he was working on his theory of fluxions, and only after referencing the work of his predecessor, John Wallis, was he able to create calculus. Leibniz, however, couldn’t have copied Newton’s work, since he followed an analytical approach that didn’t rely on Newton’s previous work. 

9. The Polio Vaccine

Polio was a devastating and deadly virus that in about 2% of cases could enter the bloodstream and attack a patient’s nerve cells, which could leave that patient paralyzed. While it’s common knowledge that polio has effectively been eradicated, what may not be as well known is that the vaccine was actually invented twice. Jonas Salk and Albert Bruce Sabin both invented the polio vaccine at two different points in history. 

In the 1940s, Doctor John Enders showed that the poliovirus could be grown in human tissue and was eventually rewarded for this breakthrough discovery with the Nobel Prize in 1954. Even in the ’40s, the virus was far too small to be imaged by scientists. Enders’ research was conducted on mice and monkey tissue that showed signs of the virus’ trademark paralysis.

This research directly led to Professor Albert Sabin and Jonas Salk’s independently developed vaccines. The first vaccine was released by Salk in 1953 after he was presented a research grant from Franklin D. Roosevelt’s National Foundation for Infantile Paralysis (Roosevelt actually suffered from the permanent paralysis of his legs thanks to a bout with polio when he was 39). After the release of the vaccine, Sabin became instantly famous.

The second vaccine would be developed in 1963 and would differ from Salk’s vaccine (which used a dead form of the virus), as it was introduced orally. Sabin’s vaccine ended up overtaking Salk’s, and he would donate the vaccine strains to the World Health Organization.

8. The Periodic Table

In 1869 and 1870 Dmitri Mendeleev and Lothar Meyer published two strikingly similar periodic tables. Though Dmitri Mendeleev is credited with the discovery, as his table was the first to be published, Lothar Meyer’s table is remarkably similar to Mendeleev’s, even though the two scientists worked completely independently of each other.

Mendeleev’s work was revolutionary. His table was so advanced, that he was able to predict where several elements would go that hadn’t yet been discovered. 

Meyer’s table (finished in 1868) was organized by atomic weight and valency. Amazingly, the two scientists were completely unaware of each other’s work, even years after the publication of both of their periodic tables. Meyer did admit, however, that Mendeleev’s table was published first. 

Although he was late to the party, Meyer’s contribution to the periodic table cannot be ignored as Meyer was the first to show the pattern in atomic value when plotted against its atomic weight.

7. Electricity and the Lightning Rod

Six years before Benjamin Franklin invented his lightning rod (or Franklin Rod, if you could travel back in time and ask him yourself), Prokop Diviš devised the first grounded lightning rod. Prokop’s device was meant to both act as a lightning rod and potentially dispel thunderstorms all together. While the second aim of Diviš’s lightning rod was more than a little unsuccessful, the lightning rod itself was a success! His fellow citizens, however, did not trust his invention, and in 1756, Prokop took his invention down and abandoned his experiments, deciding to turn his attention to music instead. 

Benjamin Franklin would invent the second grounded lightning rod in 1752 as part of a larger exploration of the properties behind electricity. 

Franklin was also the first to produce a workable system for testing his hypothesis, stating, “The electrical fire would, I think, be drawn out of a cloud silently before it could come near enough to strike.” 

Unlike Prokop’s lightning rod, Franklin’s Franklin Rod would come to adorn most rooftops in what would become the United States, often featuring ornamental glass balls as part of their overall aesthetic. But ironically, Prokop’s rod is thought to have been better grounded than Benjamin’s, but his theories and studies on electricity would not become public until after his passing.

6. Neutrinos Mass Discovery

A neutrino is a neutral subatomic particle that doesn’t typically interact with normal matter. They were first observed in 1956 by Fred Reines of the University of California at Irvine, but after it was shown that nuclei that undergo beta decay emit neutrinos along with their electrons, physicists wanted to know whether or not these particles also had mass.

Takaaki Kajita in Japan (in collaboration with a team of 120 other US and Japanese scientists) and Arthur B. McDonald in Canada both proved that neutrinos have mass and they did it using completely different methods. Kajita’s team measured the neutrinos produced in the atmosphere from cosmic rays using SuperKamiokande, a Cerenkov detector containing 50,000 tons of ultrapure water. Kajita’s team revealed that their detector measured the neutrinos to have a mass below one electronvolt.

To put this in perspective, one electron has a mass of 511,000 electronvolts. 

Now, Kajita’s study was conducted in 2015, but Arthur B. McDonald’s study took place 15 years earlier and revealed that neutrinos actually deviate into different types, causing them to switch to different states (electron neutrinos, muon neutrinos, and tau neutrinos, which all exhibit different behaviors). This study effectively suggested that these subatomic particles have to have mass in order to exhibit this kind of behavior.

And as a result, both Takaaki Kajita and Arthur B. McDonald share the Nobel Prize. 

5. The Television

Television may be the greatest example of simultaneous invention, as it wasn’t just two inventors that contributed to its inception, but several.

The device was originally conceived as an educational tool and a means for interpersonal communication that would quickly become a broadcast medium that continues to wield significant influence over the citizens of many countries in the modern world. 

The first discovery of television was made by a telegraph worker named Joseph May when he realized that selenium wire varied in its electrical conductivity. May observed that direct contact with sunlight caused these variations, which would lead to the method in which light is transformed into an electrical signal. 

In 1880, French Engineer, Maurice LeBlanc published an article in the journal La Lumière électrique, which outlined the basic principles that would make up all television technology going forward. Though LeBlanc never actually developed a working prototype, his concepts were further fleshed out by British and US inventors John Logie Baird and Charles Francis Jenkins respectively, which consisted of the transmission of a single live human face.

This would all culminate in the first successful demonstration of television in its modern form in 1927 by Philo Taylor Farnsworth, a 21-year-old inventor who lived in a house without access to electricity until he was age 14.

4. Automated Teller Machine

In 1967, Scottish inventor John Shepherd Barron invented what was called at the time the De La Rue Cash System (known as the ATM today). Though at the time, ATM cards did not exist, so Barron’s machine accepted checks imprinted with Carbon-14, an isotope that carries slight radioactivity. The invention changed banking as it was known at the time.

But in 1969, Don Wetzel invented America’s first ATM, which was installed at Chemical Bank (which is now a Chase Banking location) in the Rockville Center of Long Island. Wetzel’s machine was able to receive deposits, dispense cash, and transfer money between accounts, and it was accessed using an ATM card with a magnetic strip. 

Both inventors were inspired by being stuck in long lines and by being locked out of their banking institution after hours and developed the concept independently of each other.  

3. The Microchip

Robert Norton Noyce, nicknamed the Mayor of Silicon Valley, was an American physicist and the co-founder of Intel Corporation and Fairchild Semiconductor. He’s also one of the men responsible for the invention of the microchip and holds the US patent for miniaturized electronic circuits.

Jack Kilby is also the inventor of the microchip, holding the US patent for a silicon-based electronic circuit. Kilby was an electrical engineer, and also co-invented the pocket calculator (known as the pocketronic). 

Amazingly, the two men developed their microchips within six months of each other. Though, between the two of them, Kilby was the only one to receive the Nobel Prize for his work, as Noyce died before he could receive his.

2. Plastic

Dr. Hermann Schnell, inventor in the employment of Bayer (who both manufactured aspirin and chemical weapons, as mentioned in our list of the most deadly chemical weapons) invented polycarbonate Makrolon in 1953.

One week later, Dr. Daniel Fox invented a polycarbonate called LEXAN, which has since gone on to be used in CDs and DVDs (you know, those ancient storage devices previously used by humans long ago to listen to music and watch movies). 

Although Fox applied for the patent for polycarbonate, it was ultimately given to Bayer, as Schnell had developed plastic first. Fortunately for the company Fox worked for (a little company called GE you might have heard of) Bayer allowed them to use the patent as well.  

1. The Jet Engine

During World War II, on opposite sides of the conflict, Sir Frank Whittle and Hans von Ohain both independently developed the jet engine. 

The jet engine created by Hans von Ohain in conjunction with Max Hahn (an automotive engineer at the time) was actually larger in diameter than Whittle’s finished model, but there were serious issues with the engine’s ability to maintain combustion stability.

Whittle’s engine, while admittedly smaller, was first tested in 1937 and this event is considered to be the first successful test of the invention (even though Ohain had demonstrated the first operational use of a jet engine). 

The two met up after the war was officially over, posing for a photograph where they both held up pictures of their jet engine designs. 

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