Who invented the light bulb?

Ernest Freeberg, University of Tennessee

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.


Who invented the light bulb? – Preben, age 5, New York City


When people name the most important inventions in history, light bulbs are usually on the list. They were much safer than earlier light sources, and they made more activities, for both work and play, possible after the Sun went down.

More than a century after its invention, illustrators still use a lit bulb to symbolize a great idea. Credit typically goes to inventor and entrepreneur Thomas Edison, who created the first commercial light and power system in the United States.

But as a historian and author of a book about how electric lighting changed the U.S., I know that the actual story is more complicated and interesting. It shows that complex inventions are not created by a single genius, no matter how talented he or she may be, but by many creative minds and hands working on the same problem.

Thomas Edison didn’t invent the basic design of the incandescent light bulb, but he made it reliable and commercially viable.

Making light − and delivering it

In the 1870s, Edison raced against other inventors to find a way of producing light from electric current. Americans were keen to give up their gas and kerosene lamps for something that promised to be cleaner and safer. Candles offered little light and posed a fire hazard. Some customers in cities had brighter gas lamps, but they were expensive, hard to operate and polluted the air.

When Edison began working on the challenge, he learned from many other inventors’ ideas and failed experiments. They all were trying to figure out how to send a current through a thin carbon thread encased in glass, making it hot enough to glow without burning out.

In England, for example, chemist Joseph Swan patented an incandescent bulb and lit his own house in 1878. Then in 1881, at a great exhibition on electricity in Paris, Edison and several other inventors demonstrated their light bulbs.

Edison’s version proved to be the brightest and longest-lasting. In 1882 he connected it to a full working system that lit up dozens of homes and offices in downtown Manhattan.

But Edison’s bulb was just one piece of a much more complicated system that included an efficient dynamo – the powerful machine that generated electricity – plus a network of underground wires and new types of lamps. Edison also created the meter, a device that measured how much electricity each household used, so that he could tell how much to charge his customers.

Edison’s invention wasn’t just a science experiment – it was a commercial product that many people proved eager to buy.

Inventing an invention factory

As I show in my book, Edison did not solve these many technical challenges on his own.

At his farmhouse laboratory in Menlo Park, New Jersey, Edison hired a team of skilled technicians and trained scientists, and he filled his lab with every possible tool and material. He liked to boast that he had only a fourth grade education, but he knew enough to recruit men who had the skills he lacked. Edison also convinced banker J.P. Morgan and other investors to provide financial backing to pay for his experiments and bring them to market.

Historians often say that Edison’s greatest invention was this collaborative workshop, which he called an “invention factory.” It was capable of launching amazing new machines on a regular basis. Edison set the agenda for its work – a role that earned him the nickname “the wizard of Menlo Park.”

Here was the beginning of what we now call “research and development” – the network of universities and laboratories that produce technological breakthroughs today, ranging from lifesaving vaccines to the internet, as well as many improvements in the electric lights we use now.

Sparking an electric revolution

Many people found creative ways to use Edison’s light bulb. Factory owners and office managers installed electric light to extend the workday past sunset. Others used it for fun purposes, such as movie marquees, amusement parks, store windows, Christmas trees and evening baseball games.

Theater directors and photographers adapted the light to their arts. Doctors used small bulbs to peer inside the body during surgery. Architects and city planners, sign-makers and deep-sea explorers adapted the new light for all kinds of specialized uses. Through their actions, humanity’s relationship to day and night was reinvented – often in ways that Edison never could have anticipated.

Today people take for granted that they can have all the light they need at the flick of a switch. But that luxury requires a network of power stations, transmission lines and utility poles, managed by teams of trained engineers and electricians. To deliver it, electric power companies grew into an industry monitored by insurance companies and public utility regulators.

Edison’s first fragile light bulbs were just one early step in the electric revolution that has helped create today’s richly illuminated world.


Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Ernest Freeberg, Professor of History, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Why do giraffes have such long legs? Animal simulations reveal a surprising answer

If you’ve ever wondered why the giraffe has such a long neck, the answer seems clear: it lets them reach succulent leaves atop tall acacia trees in Africa.

Only giraffes have direct access to those leaves, while smaller mammals must compete with one another near the ground. This exclusive food source appears to allow the giraffe to breed throughout the year and to survive droughts better than shorter species.

But the long neck comes at a high cost. The giraffe’s heart must produce enough pressure to pump its blood a couple of metres up to its head. The blood pressure of an adult giraffe is typically over 200mm Hg – more than twice that of most mammals.

As a result, the heart of a resting giraffe uses more energy than the entire body of a resting human, and indeed more energy than the heart of any other mammal of comparable size. However, as we show in a new study published in the Journal of Experimental Biology, the giraffe’s heart has some unrecognised helpers in its battle against gravity: the animal’s long, long legs.

Meet the ‘elaffe’

In our new study, we quantified the energy cost of pumping blood for a typical adult giraffe and compared it to what it would be in an imaginary animal with short legs but a longer neck to reach the same treetop height.

This beast was a Frankenstein-style combination of the body of a common African eland and the neck of a giraffe. We called it an “elaffe”.

We found the animal would spend a whopping 21% of its total energy budget on powering its heart, compared with 16% in the giraffe and 6.7% in humans.

By raising its heart closer to its head by means of long legs, the giraffe “saves” a net 5% of the energy it takes in from food. Over the course of a year, this energy saving would add up to more than 1.5 tonnes of food – which could make the difference between life and death on the African savannah.

How giraffes work

In his book How Giraffes Work, zoologist Graham Mitchell reveals that the ancestors of giraffes had long legs before they evolved long necks.

This makes sense from an energy point of view. Long legs make the heart’s job easier, while long necks make it work harder.

However, the evolution of long legs came with a price of its own. Giraffes are forced to splay their forelegs while drinking, which makes them slow and awkward to rise and escape if a predator should appear.

Statistics show giraffes are the most likely of all prey mammals to leave a water hole without getting a drink.

How long can a neck be?

 
In life, the Giraffatitan dinosaur would most likely have been unable to lift its head this high. Shadowgate / Wikimedia, CC BY

The energy cost of the heart increases in direct proportion to the height of the neck, so there must be a limit. A sauropod dinosaur, the Giraffatitan, towers 13 metres above the floor of the Berlin Natural History Museum.

Its neck is 8.5m high, which would require a blood pressure of about 770mm Hg if it were to get blood to its head – almost eight times what we see in the average mammal. This is implausible because the heart’s energy cost to pump that blood would have exceeded the energy cost of the entire rest of the body.

Sauropod dinosaurs could not lift their heads that high without passing out. In fact, it is unlikely that any land animal in history could exceed the height of an adult male giraffe.The Conversation

Roger S. Seymour, Professor Emeritus of Physiology, University of Adelaide and Edward Snelling, Faculty of Veterinary Science, University of Pretoria

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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