Albert Einstein

Dents in space, light in bundles, and matter that turns into energy sound like science-fiction fantasies. However, Albert Einstein said they were real. Other scientists proved through observations that Einstein’s theories were right. Einstein revolutionized the science of physics and helped bring in the atomic age.

WHERE DID EINSTEIN GROW UP?

Albert Einstein was born in Ulm, Germany, on March 14, 1879. He grew up in Germany, Italy, and Switzerland. Einstein taught himself geometry when he was 12 years old. School bored him because it required endless memorizing and reciting. He often skipped classes to study on his own or to play his violin. Yet he graduated from college in 1900 and earned a Ph.D. degree in 1905. From 1902 to 1907, Einstein worked as a clerk in the patent office in Zürich, Switzerland. His job left him plenty of time to think.

WHAT DID EINSTEIN THINK ABOUT?

Einstein thought about the rules that govern the way the world works. For example, he explained why small particles in liquids wiggle around, a movement called Brownian motion. He said that the particles were being bumped into by tiny bits of matter called atoms that are too small to see.

He also thought about light and electricity. Einstein knew that light shining on metal sometimes causes electricity to flow. He explained this result, called the photoelectric effect, by saying that light is made of tiny bundles of energy called photons. Photons hitting the metal knock particles called electrons away. Since electricity is simply moving electrons, he had solved the mystery of the photoelectric effect. In 1921, Einstein won the most famous prize in science, the Nobel Prize, for this work.

Another thing Einstein thought about was time. He said that time does not always flow at the same rate. He proposed that motion affects time. He called this idea the special theory of relativity.

Einstein then came up with his general theory of relativity. This theory has a new explanation for gravity. Einstein said that gravity comes from curves or dents in the fabric of space. Objects make dents in space the way a bowling ball makes a dent in a mattress. The Moon falls into the dent made by Earth and rolls around the Earth. Scientists later proved that the dent a star makes in space-time bends light as the light passes by.

Einstein changed physics by showing that new ideas could come just from thinking. Before Einstein, most new ideas in physics had come from experiments in the laboratory.

EINSTEIN AND ATOMIC ENERGY

Einstein also said that matter and energy are the same thing. He expressed this relation in a famous equation: E=mc2. This equation says that energy (E) equals mass (m) times the speed of light squared (c2). Energy can therefore be changed into matter, and matter into energy. The ability to turn matter into energy led to the development of the atomic bomb and nuclear power.

FAME AND LATER YEARS

Einstein’s theories made him famous, even though few people understood them. He became a university professor and director of a physics institute in Berlin, Germany. After the Nazis rose to power in Germany, Einstein left. In 1933, he came to the United States, where he lived the rest of his life. Einstein died in Princeton, New Jersey, on April 18, 1955.

Einstein’s last great idea was that every force in nature is part of one master force. Physicists are still working on this idea, which they call the theory of everything

Aristotle

What is the universe made of? Why do accidents happen? How do animals grow? Ancient Greek philosopher Aristotle tried to find answers to big questions like these. Today, he is remembered as one of the greatest philosophers who ever lived.

WALKING AND TALKING

Aristotle was born in 384 BC in ancient Macedonia (now northern Greece). His father was a doctor. When Aristotle was 17, he went to Athens, the biggest and richest city in ancient Greece. He stayed there for most of his life, studying and teaching. He set up his own school, where students discussed new ideas while strolling in the gardens.

From 345 to 335 BC, Aristotle lived in Macedonia. He worked as tutor to Prince Alexander, who later became known as Alexander the Great. In 335 BC, Aristotle returned to Athens. In 323 BC, Alexander died, and his friends became unpopular. Aristotle was forced to leave his school in Athens. He died the next year, in 322 BC.

INVESTIGATIONS

Aristotle studied many subjects. But he was most interested in science, especially biology (the study of all living things), zoology (the study of animals), and astronomy (the study of the universe). He tried to find out how humans think, and how they experience the world around them. He also tried to describe invisible things, such as the mind and the soul. He invented a new science, called causality. It explained why things happen.

WHAT WAS SO SPECIAL ABOUT ARISTOTLE?

In all his investigations, Aristotle pioneered a new way of studying. He looked for clues in what he saw and for proof. He didn’t use guesswork or accept whatever people already believed. His method of questioning changed the way scholars worked for many centuries.

Aristotle wrote many books, and he kept notes to help teach his students. These might easily have been lost after ancient Greek civilization collapsed. But Muslim scientists carefully preserved these writings and passed them on to scholars in Europe and Asia. Aristotle’s ideas spread around the world.

Benjamin Franklin

Was Benjamin Franklin a famous scientist? Or was he an inventor? Was he a diplomat and a statesman? Or a printer and a writer? Franklin was not just one of these things—he was all of them!

EARLY LIFE

Benjamin Franklin was born in Boston, Massachusetts, on January 17, 1706. His father, Josiah, had 17 children. Franklin’s mother, Abiah Folger, was Josiah’s second wife.

Like many boys at that time, young Ben attended school for only a few years. At age 10 he began training in his father’s candle-making shop. Ben didn’t like the work. When he was 13, his father sent him to work with his older brother James.

LEARNING A TRADE

James Franklin taught his brother about the printing business. Ben learned to work the heavy printing press. He sold newspapers and even began writing articles. Franklin loved to read and study in his free time, teaching himself math, science, literature, and foreign languages.

In 1722, James Franklin was arrested for criticizing Boston’s leaders in his newspaper. Ben Franklin kept the paper running in his brother’s absence.

In 1724, 18-year-old Ben Franklin sailed to London, England. There he learned all he could about printing and publishing.

Franklin returned to America and settled in Philadelphia, Pennsylvania, in 1726. There he bought a small newspaper, the Pennsylvania Gazette. He married Deborah Read in 1730.

A MAN OF IDEAS

Despite his lack of schooling, Franklin had many ideas on how to improve people’s lives. For example, he organized one of the first public libraries in America. He also started the first fire department and one of the first hospitals in Philadelphia. He busied himself with plans to improve city streets and lighting.

Franklin wrote about improving education, and he helped found a school that became the University of Pennsylvania. In 1732, he began publishing a popular, witty advice book called Poor Richard’s Almanack. Franklin also founded the American Philosophical Society, based in Philadelphia, to discuss the latest scientific theories.

Around 1744, Franklin invented the Franklin stove, which provided more heat while using less fuel. A few years later, he began experimenting with electricity. In 1752, he invented a lightning rod, which keeps lightning from striking buildings and other structures. His scientific ideas and inventions became known in Europe as well as in America.

HOW FRANKLIN SERVED HIS COUNTRY

At the same time, Franklin added politics to his list of achievements. He wrote and published many articles about political issues. In 1754, the colonies sent representatives to a meeting to discuss how they should respond to the French and Indian War. There Franklin proposed his Albany Plan, calling for the colonies to keep their independence while working together on issues that affected all of them. His plan was rejected, but his vision of government would later influence the writing of the United States Constitution.

From 1757 to 1772, Franklin spent most of his time living in London. He represented the colonies in British politics. Franklin explained America’s views of British tax policies, such as the Stamp Act. His efforts helped get the hated Stamp Act repealed by the British government.

Like many Americans, Franklin felt torn between remaining connected to Great Britain and the desire for independence. He understood the growing anger of Americans over British taxes and other actions. Franklin returned to Pennsylvania in May 1775. The American Revolution (1775-1783) had begun a month earlier when fighting broke out in Massachusetts.

In 1775, the 70-year-old Franklin served as a representative at the Second Continental Congress, an early American governing body. He worked on many committees, including the committee that wrote the Declaration of Independence.

FRANKLIN AND THE REVOLUTION

Franklin spent most of the war years in Europe as a diplomat representing the American congress. He helped convince France to loan the Americans money to fund the war effort. Franklin’s humor and intelligence made him very popular in France. Eventually, France joined America in fighting—and defeating—the British.

As the war wound down, Franklin helped negotiate a peace treaty with Great Britain. The treaty, signed in 1783, recognized American independence and ended the long war.

STILL BUSY IN HIS EIGHTIES

Pennsylvania sent Franklin as a delegate to the 1787 convention that planned and wrote the United States Constitution. He was the convention’s oldest delegate.

Franklin remained interested in social causes in his old age. He served as president of the Pennsylvania Abolition Society, an antislavery group. He sent a petition to the United States Congress calling for an end to slavery.

Franklin died on April 17, 1790. His wisdom, wit, and hard work had served his country well.

Charles Darwin

Charles Darwin had no idea when he set off on a sea voyage to explore South America in the 1830s that he would set off a controversy that continues today. Darwin studied animals in isolated places. He thought that differences he saw in similar species (kinds) of animals meant that the animals had evolved, or changed over time. His important idea is called the theory of evolution by natural selection.

WHAT DARWIN OBSERVED

Charles Robert Darwin was born in Shrewsbury, England, on February 12, 1809. He came from a wealthy family and never had to work. He studied medicine and theology. In 1831, he had the chance to go on a scientific expedition. He sailed as a volunteer scientist aboard the HMS Beagle.

Everywhere the Beagle stopped, Darwin made observations of plants and animals. In the Galápagos Islands, Darwin noted that each island had its own form of tortoise, mockingbird, and finch. Each species on each island was slightly different. Darwin wondered if there were links between the similar species.

WHAT DARWIN DECIDED

For the next 20 years Darwin thought about what his observations might mean. He decided that the young of any species must compete for food in order to survive. Those with traits best suited to survival would grow up and reproduce offspring with those traits. Eventually, a new species would evolve. Darwin also thought that all species were descended from common ancestors. In 1859, he wrote a book called On the Origin of Species.

Many scientists did not believe his theory until modern genetics—the study of inherited traits—began in the early 1900s. Most attacks on Darwin’s ideas came from religious opponents. They thought that evolution denied the divine creation of human beings and made people and animals equal.

Darwin spent the rest of his life writing about his theory. He died on April 19, 1882.

Copernicus

When Nicolaus Copernicus went to school, he learned that Earth was the center of the universe and that everything in the heavens revolved around Earth. The Sun and all the planets circled around Earth, he was told.

The Earth-centered theory taught to Copernicus had been developed 1,400 years before by an astronomer named Ptolemy, who lived in Alexandria, Egypt. Copernicus looked into Ptolemy’s system more carefully and came up with a

different idea. He was sure that the Sun is the center of our solar system and that Earth and the other planets go around the Sun. He was right, of course. Today, we think of Copernicus as the founder of modern astronomy.

HIS LIFE AND CAREER

Copernicus was born on February 19, 1473, in Toruñ, Poland. His family was well-to-do. Copernicus went to the best schools. He studied medicine, law, and religion in Italy. He also became interested in astronomy. In 1503, he went back to Poland to work for his uncle. He also worked on his new theory about how Earth moves.

HIS SUN-CENTERED SYSTEM

Copernicus thought that Earth turns once a day and goes around the Sun once a year. Copernicus decided that the way Earth turns makes it look like the Sun, stars, and planets are going around the Earth.

In 1530, he wrote a book called On the Revolutions of the Celestial Spheres. The book was published in 1543, just before Copernicus died. Most astronomers and church officials thought his ideas were too radical. Some others, however, secretly thought he was right.

The Italian astronomer Galileo, German astronomer Johannes Kepler, and English physicist Sir Isaac Newton later did studies that supported the ideas of Copernicus. Not until the early 1700s, however, did most scientists agree that Copernicus was right.

Eli Whitney

In 1793, Eli Whitney invented a simple machine that changed America’s history: the cotton gin.

Whitney’s invention made growing cotton much more profitable. Cotton soon became the most important crop in America’s Southern states.

EARLY LIFE

Eli Whitney was born in 1765 in Westboro, Massachusetts. He attended Yale College (now Yale University).

In 1792, Whitney traveled to the South. While in Georgia, Whitney designed and built a model for the cotton gin.

WHAT DID THE COTTON GIN DO?

Before the cotton gin, cottonseeds had to be picked from the cotton fibers by hand. This took a great deal of time. Whitney’s machine quickly separated the seeds from the fibers. In fact, Whitney’s cotton gin cleaned more cotton in one day than a person could clean by hand in a whole year!

THE COTTON GIN’S IMPACT

The invention of the cotton gin made cotton the most important crop of the American South. Millions of acres of cotton blanketed Southern fields. In turn, the boom in cotton tied millions of slave workers to the fields. They picked cotton for the cotton gins.

The price of cotton clothing fell. Cotton fabrics, such as calico and muslin, could easily be dyed in bright colors and patterns. Soon, everyone wanted to wear these fashionable cotton clothes. This prompted the growth of textile mills in New England and Great Britain. The mills demanded more and more raw cotton to turn into cloth.

DID WHITNEY GET RICH?

Eli Whitney made little money from his cotton gin. Whitney and a partner opened a factory in Connecticut to make cotton gins. But a fire prevented the company from making enough machines to fill the flood of orders.

Other factories soon began copying Whitney’s invention. Whitney had applied for a patent to protect his rights to his invention in 1794. But his patent was not enforced until 1807. Then in 1812, his request to renew his patent was denied.

WHAT ELSE DID WHITNEY DO?

In 1798, Whitney won a contract to provide 10,000 muskets for the American military. Whitney experimented with making standard parts he could use in different guns. He was one of the first manufacturers to do this. Whitney died in 1825.

Galileo

No one was supposed to question any teachings about astronomy or physics in the 1500s. Most of the teachings came from ancient Greeks. Galileo thought that the ancient Greeks were wrong about many ideas. He believed that making careful measurements could help people learn accurate facts about astronomy and physics. Galileo was one of the people who began what we now call the modern scientific revolution.

LIFE AND CAREER

Galileo Galilei was born near Pisa, Italy, on February 15, 1564. After attending the university, he taught mathematics. He also observed how things move. There is a story that he dropped two objects of different weights at the same time from the Leaning Tower of Pisa. He found that light and heavy objects fell at the same rate. The ancient Greek Aristotle taught that heavier objects fell faster.

SCIENTIFIC DISCOVERIES

In the early 1600s, Galileo was the first person to use a telescope to look at objects in the night sky. He discovered many things, including mountains and craters on the Moon and four moons going around Jupiter. Galileo also defended the idea of Polish astronomer Copernicus that Earth goes around the Sun. The ancient astronomer Ptolemy said that Earth was the center of the universe and that the Sun went around Earth. Ptolemy’s system was the official teaching of the Roman Catholic Church. Church authorities ordered Galileo not to defend Copernicus’s theory.

HERESY TRIAL AND CONVICTION

In 1632, Galileo published a book that compared Ptolemy’s and Copernicus’s ideas. The book concluded that Copernicus was right. Galileo was ordered to go to Rome and stand trial for heresy (holding ideas opposed to church teachings). Galileo was forced to say that Copernicus was wrong. Galileo was sentenced to life in prison. He was old and sick, so instead they kept him inside his house. In 1992, Pope John Paul II said the church was wrong to convict Galileo of heresy.

George Washington Carver

When George Washington Carver looked at peanuts he saw more than a nut in a shell. He saw opportunity for farmers in the Southern United States. This great American agricultural scientist found more than 300 uses for the peanut and other plants. From peanuts, Carver made soap, ink, flour, axle grease, and other products. Many Southern farmers raised cotton. He showed farmers the value of raising other crops. He also showed them how to improve the soil.

HIS EARLY LIFE

George Washington Carver was born on a farm near Diamond, Missouri, in 1864. His parents were slaves. The Civil War was being fought when he was born, and the slaves were soon freed. When he was ten years old, he left the farm and began working his way through school.

After he finished high school, he worked his way through Iowa State College of Agriculture and Mechanic Arts (now Iowa State University). When he graduated, he went to work at the college, teaching and doing research.

CARVER’S RESEARCH

In 1896, Carver became director of the Department of Agricultural Research at Tuskegee Normal and Industrial Institute (now Tuskegee University) in Alabama. It was then that he began to experiment with peanuts.

In addition to finding new uses for peanuts, he found industrial uses for sweet potatoes and soybeans. He developed a new type of cotton known as Carver's hybrid. He also taught ways of making soil better for growing crops.

AWARDS AND HONORS

Carver earned many awards and honors for his work. In 1923, the National Association for the Advancement of Colored People (NAACP) awarded him the Spingarn Medal. In 1935, he was appointed to an important position in the U.S. Department of Agriculture. In 1940, he donated his savings to establish the George Washington Carver Foundation at Tuskegee for agricultural research. Carver died at Tuskegee on January 5, 1943. The farm in Missouri where he was born became the George Washington Carver National Monument in 1943.

Henry Ford

Henry Ford put America on wheels. Ford produced a simple, sturdy automobile called the Model T. He sold the car at a low price that many Americans could afford. The car was easy to operate. Automobiles became part of everyday life in the United States because of Ford.

HOW HENRY FORD GOT STARTED

Henry Ford was born July 30, 1863. He grew up on a farm near Dearborn, Michigan, but he disliked farm work. He liked mechanical things.

At age 16, Ford got a job in a machine shop in Detroit. He later worked as an engineer. In his spare time, he built engines. After years of experimenting, Ford produced his first automobile in 1896. This vehicle was powered by a gasoline motor and mounted on four bicycle wheels.

HOW FORD CHANGED FACTORY WORK

Henry Ford founded the Ford Motor Company in 1903. Ford wanted to produce large numbers of cars at low cost. He brought out the first Model T in 1908. From 1908 to 1927, 15 million Model Ts were produced. Some cost as little as $260.

Ford set up factories with assembly lines that could make cars fast and efficiently. As cars were being built, they moved slowly down an assembly line. Each worker along the line did one set of tasks, on car after car.

Workers on the assembly line often found their work dull and tiresome. Many of them quit after a short time. To keep his workers, Ford doubled the pay for his assembly-line workers. But he made them work very hard.

COMPETITION AND WAR WORK

Other automobile companies scurried to catch up with Ford. They copied Ford's successful use of the assembly line. They also started building cars that were more advanced, better looking, and more comfortable than the Model T.

Ford was slow to change his ways. By the 1930s, Ford no longer dominated the car industry.

In 1941, the United States entered World War II. Ford’s factory went from producing cars to producing bomber planes for the U.S. military during the war.

WHAT ELSE FORD DID

Ford started a charity, the Ford Foundation, with his son in 1936. When Ford died in 1947, he left most of his money to the Ford Foundation. The Ford Foundation is still giving money to help poor countries and poor areas.

Ford also built a museum of American history in Dearborn, Michigan. It’s called Greenfield Village. If you visit the museum, you can take a ride in a Model T.

Leonardo da Vinci

Leonardo da Vinci excelled as a painter, sculptor, architect, engineer, and scientist. He had endless curiosity. Leonardo wanted to understand how things worked. He wanted to put down on paper what he saw. He left thousands of pages of drawings and notes that recorded his thoughts.

GOOD AT EVERYTHING

Leonardo was born in 1452 in the small town of Vinci, near Florence, Italy. He had little schooling and was largely self-taught.

Leonardo seemed to be good at everything he tried. He was handsome, a good speaker, and a fine musician. He trained as a painter with Andrea del Verrocchio, a leading artist in Florence. Leonardo later worked for dukes and kings.

HIS MOST FAMOUS PAINTINGS

Leonardo produced a relatively small number of paintings, and he left some of them unfinished. But he had original ideas that influenced Italian artists long after his death. Leonardo believed painting was a science. He applied scientific thinking in his art so that his paintings looked more like the real world. One of his most important painting techniques was sfumato, a blending of one area of color into another so there are no sharp outlines.

Leonardo used sfumato in one of his most famous paintings, the Mona Lisa. When you look at this portrait, notice how colors shade into each other on her face and hands. See how Leonardo has blurred the edges of her mouth to give her the hint of a smile. This mysterious smile has fascinated people for centuries. It looks as if Mona Lisa’s expression might change at any moment because of the way Leonardo has softened the edges of the mouth, eyes, and cheeks. She seems almost alive.

Many people consider a mural by Leonardo known as The Last Supper to be his masterpiece. Christ, seated in the middle of The Last Supper, has just announced that one of his 12 apostles will betray him. Leonardo places the figures in this painting in a way that increases the drama of the announcement. Christ is the calm center. His body, which is set slightly apart from the others, forms a stable triangle. The apostles are arranged in four groups, some leaning toward Christ and some leaning away. Their gestures and the expressions on their faces reveal their reactions to Christ’s words.

HIS DRAWINGS AND NOTEBOOKS

Drawing was Leonardo’s favorite tool. He said that drawing was a better way of communicating ideas than words were. He drew catapults and war machines. He drew the muscles and skeletons of human beings and other animals. He drew clouds, swirling water, and storms. He designed churches that were never built.

Leonardo’s drawings and theories are contained in numerous notebooks. His ideas were far in advance of what other people were thinking at the time. But the notebooks were not published during his lifetime. Had his notebooks been published, they might have revolutionized scientific thinking in the 1500s. Leonardo’s deep love of research was the key to both his artistic and scientific endeavors. Leonardo died in 1519.

Louis Pasteur

No one knew what caused infections when Louis Pasteur was a boy in the early 1800s. No one knew that germs spread disease. There were no antibiotics or other drugs. Many people died from infections.

Pasteur discovered that bacteria cause many diseases. He showed that bacteria get into living things and then multiply. He proved that diseases could be cured by stopping the spread of bacteria. This important discovery is called the germ theory of disease. It led to antibiotics and other medicines that kill bacteria. Pasteur’s discovery has saved the lives of many people.

HOW PASTEUR HELPED INDUSTRY

Louis Pasteur was born in France in 1822. He studied physics and chemistry in Paris. As a professor of chemistry, he worked on problems that affected French industry. The wine-making industry in France was in trouble during the mid-1800s because much of the wine was spoiling. Pasteur discovered that germs were getting into the wine and turning it sour. He found that heat killed these germs and prevented the wine from spoiling. Pasteur later applied his discovery to milk. His way of heating foods to kill bacteria is now called pasteurization.

Pasteur also helped the French silk industry. In the mid-1800s, a disease was killing off silkworms before they could spin silk threads. Pasteur showed that the disease was in the silkworm eggs and that getting rid of any infected eggs could keep the disease from spreading. Pasteur became a national hero in France for saving the wine and silk industries.

HOW PASTEUR PREVENTED DISEASE

Pasteur then discovered how to make vaccines to protect people and animals against disease. He observed that animals infected with a disease sometimes became immune to the disease—that is, protected from getting the disease again. Pasteur found that he could weaken germs in his laboratory. When he put weakened germs into the

bodies of animals, the animals became immune to the disease caused by the germs. Pasteur made a vaccine to protect sheep against a disease called anthrax.

One of Pasteur’s most important discoveries was a vaccine against rabies. People can get this deadly disease if they are bitten by an animal infected with rabies. In 1885, a mother begged Pasteur to treat her young son who had been badly bitten by a dog with rabies. The vaccine worked, and the boy lived. Pasteur then became an even greater national hero. In 1888, the Pasteur Institute in Paris was founded in his honor. Pasteur became its director. He worked there until he died in 1895.

Marie Curie

At a time when women scientists were rare, Marie Curie probed the mysteries of radioactivity and X rays. In 1903, she and her husband won the Nobel Prize in physics, one of the most important awards in science. In 1911, Marie Curie won a second Nobel Prize, this time in chemistry. She is one of very few people in history to win two Nobel prizes.

MARIE CURIE’S EARLY LIFE

Marie Curie was born as Maria Sklodowska in Poland in 1867. Though Maria excelled in school, no university in Poland at that time allowed female students.

In 1891, Maria traveled to Paris, France. She called herself Marie, the French form of Maria. She attended the Sorbonne, a famous college in Paris. Marie studied physics and mathematics and graduated at the top of her class! She also met a French chemist named Pierre Curie. They married in 1895.

WHAT DID THE CURIES RESEARCH?

Marie and Pierre were pioneers in studying radioactivity. Radioactivity is a process in which certain elements, such as uranium, break down into other elements. In the process, they give off energy in the form of radiation. Marie and Pierre built on the work of Wilhelm Roentgen, who discovered X rays, and Antoine Henri Becquerel, who discovered radioactivity in the element uranium. X rays are a type of radiation.

The Curies discovered that a mineral called pitchblende was radioactive. Pitchblende contains uranium. But pitchblende gives off more radiation than uranium alone could. The Curies guessed that there must be other radioactive elements in the pitchblende.

The Curies separated huge amounts of pitchblende into its chemical parts—the elements it is made of. In July 1898, they reported the discovery of a new element called polonium. In December, they announced the discovery of another new element, radium.

MARIE CURIE GOES ON ALONE

In 1906, a horse-drawn carriage hit and killed Pierre. Marie stepped into his teaching post at the Sorbonne. She was the first woman to teach at the university. She poured her energy into research and raising her daughters. One daughter, Irene, followed her parents into scientific research. In 1914, the Sorbonne built a new laboratory to research radioactive materials. Today the laboratory is named after Marie Curie.

Marie Curie earned little money from her famous research. Her Nobel Prize money paid for more research. She did not patent—reserve for her own gain—her discoveries. She left them free for other scientists to use.

SERVICE IN WORLD WAR I

When war broke out in Europe in 1914, Marie Curie helped equip ambulances with X-ray machines. The International Red Cross named her its head of Radiological Service. She taught doctors how to use X rays to help wounded soldiers. X rays help doctors see inside the body so they can figure out what’s wrong with people.

CURIE’S RESEARCH AND HER HEALTH

Radiation in large doses poisons the body. Curie was exposed to radiation for years. At that time, no one knew that radiation was dangerous. Curie’s work gave her leukemia, a form of cancer. Marie Curie died on July 4, 1934. Today, an important result of Marie Curie’s research is the use of radiation to slow or destroy cancers.

Sir Isaac Newton

Isaac Newton was always wondering about the things he saw around him. What holds the Moon and planets in the sky? How does a rainbow form? He uncovered basic laws of nature. He used mathematics to explain these laws and predict how objects would behave. He became one of the greatest scientists of all time.

STUDENT YEARS

Newton was born in Woolsthorpe, England, on December 25, 1642. He loved to build mechanical models, but he was not a good student. His mother took him out of school so that he could help run the family farm. Newton did not like farming. He liked to read and study on his own. A former teacher knew that Newton was very smart and helped him go to the University of Cambridge.

After Newton graduated, bubonic plague broke out in Cambridge. Many people got sick and died. Newton went back to the family farm for two years until the plague died down. He came up with many of his greatest ideas from 1665 to 1667 while he was alone in the countryside.

HIS GREATEST WORK

Newton invented a new kind of mathematics called calculus. Today, scientists and engineers use calculus to solve many kinds of problems.

Newton came up with theories about gravity and motion. He thought that the same force pulling people and apples down to Earth keeps the Moon going around Earth and the planets going around the Sun. He used mathematics to prove his theories.

Newton used a prism, a piece of glass with many sides, to study light. He found that sunlight is made up of every color in the rainbow.

LIFE AT CAMBRIDGE

Newton went back to Cambridge and became a professor of mathematics. He built the first reflecting telescope, which uses mirrors instead of lenses. He became famous for his calculus, but he did not tell many people about his theory of gravity. He was shy and modest and did not want other scientists to criticize his work.

Finally his friends had him write a book about gravity and motion titled Principia Mathematica. Scientists called the book a masterpiece. Newton was made a knight. When he died on March 20, 1727, he became the first scientist to be buried in Westminster Abbey in London.

Thomas Edison

Until the late 1800s, most people went to bed soon after sunset. They used candles and oil or gas lamps for light. American inventor Thomas Edison changed the way people live when he invented the first practical light bulb. The light bulb was just one of more than 1,000 inventions created by one of the greatest inventors of all time.

LIFE AND CAREER

Thomas Alva Edison was born in Milan, Ohio, in 1847, and grew up in Port Huron, Michigan. He attended school for only three months. His mother taught him reading, writing, and arithmetic.

In 1862, Edison saved a boy from being run over by a train. The boy’s father operated a telegraph machine, which sent coded messages over wire. As thanks, the father taught Edison how to operate the telegraph. Edison then made improvements to the telegraph. He earned money from his inventions.

RESEARCH LABORATORY

In 1876, Edison started the first industrial research laboratory at Menlo Park, New Jersey. By then, Edison was partially deaf. He worked very hard. He lived in his laboratory and became rich from his inventions. He was married twice and had six children. But he worked so much that he spent little time with his family.

GREAT INVENTIONS

Edison’s greatest inventions included an improved telephone, the phonograph, the motion-picture camera, and electric storage batteries. He is best remembered for inventing a long-lasting light bulb.

In the 1870s, many inventors were trying to make a practical light bulb. Edison tried hundreds of schemes. Finally he found a filament (thin thread) made of carbon. An electric spark made the filament glow inside a glass tube. Edison’s incandescent lamp was a great success. It burned steadily for more than 40 hours.

Edison wanted people to have electric light in their homes. So he built the first electric power plants.

People liked Edison because he was a down-to-earth man. His favorite saying was, “Genius is 1 percent inspiration and 99 percent perspiration.”

Wright Brothers

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It lasted only 12 seconds, but those 12 seconds changed history. On December 17, 1903, two brothers named Orville and Wilbur Wright made the first airplane flight.

GROWING UP

Wilbur Wright was born in Millville, Indiana, in 1867. Orville was born in Dayton, Ohio, in 1871. Neither boy graduated from high school, but mechanical things fascinated the young Wright brothers. They taught themselves math and engineering. In 1892, the brothers opened a shop in Dayton where they designed and built bicycles.

WHAT SPARKED THEIR INTEREST IN FLYING?

The Wrights became interested in the work of German inventor Otto Lilienthal. Lilienthal designed and flew on gliders. Lilienthal died in a glider crash in 1896. The brothers decided to build a flying machine. They also were determined to learn how to control flight safely. They began experimenting with large kites.

STARTING OUT WITH KITES AND GLIDERS

The Wrights’ kites had controls that let them warp (twist) the ends of the wings. This warping helped them to make the kite more stable and to adjust its direction of flight. In 1900, the brothers built a huge kite with wings that stretched 17 feet (5 meters). The kite was large enough to carry a person.

They tested their flights near the town of Kitty Hawk on the coast of North Carolina. This location was ideal. Steady winds from the ocean lifted the kite into the air. The kite crashed on sand dunes, which was safer than crashing into trees or solid ground. Wilbur actually flew on the kite for a few seconds.

Next, the Wrights built a wooden glider. In 1901, they experimented on the larger sand dunes at Kill Devil Hills. The glider had arched wings, a design that made the glider more stable. It also had hand controls that worked a flap on the tail to control up-and-down movements. But the brothers needed a design with even more stability and control.

MORE TESTS AND EXPERIMENTS

The Wrights designed and built a wind tunnel, a wooden box six feet (2 meters) long with a fan blowing in one end. They tested models of different wing shapes in the wind that blew through the tunnel. They also tried new ways to control their gliders. In 1902, the Wrights built a new glider with a wingspan of 32 feet (10 meters). They added a moveable rudder to the back of the glider to help steer. Their tests were so successful that they decided to build an engine-powered flying machine.

THE FIRST POWERED FLIGHT

The brothers built their own small engine. They also built a propeller. Their plane weighed 750 pounds (340 kilograms). Its wings stretched 40 feet (12 meters) across. On December 17, 1903, Orville made the first successful flight. He stayed in the air for 12 seconds. Wilbur also made flights that day. In the last flight Wilbur stayed in the air for 59 seconds and traveled 852 feet (260 meters)!

HOW DID THE WRIGHTS PROMOTE FLYING?

The brothers continued perfecting their plane. They practiced piloting machines with more powerful engines. These planes made longer flights and sharper turns.

The Wrights gave public demonstrations of flying in both the United States and Europe. Orders for planes rolled in from governments around the world. In 1909, the brothers formed the Wright Company to build airplanes. By that time they’d produced a plane stable enough for a 20-mile (32-kilometer) flight.

Wilbur died of typhoid fever in 1912. Orville sold the company in 1915 and spent time doing more research. By 1918, other companies had begun to build airplanes. Orville won many awards for his work before his death in 1948.