Karen Hill

As science moved toward experimentation to prove its theories, tools of measurement became vital. The measurement of time was probably the most important of all, but in Galileo’s time, scientists had not yet invented a dependable timepiece. Ancient humans could measure years, months, and days with the movements of Earth, the Moon, and the Sun. … Read more

It had been 70 years since Copernicus proposed that the Sun, not Earth, was the center of the universe. The academic world, however, was still teaching the Ptolemaic system, with an unmoving Earth at the center. Most scientists simply did not believe Copernicus’s theory; others who did and tried to teach it were burned at … Read more

By the late eighteenth century, the development of the telescope had made it possible for many amateur astronomers to search the skies. Most were content to view what was already known, while some dreamed of great discoveries. One 41-year-old musician in Bath, England, wanted to systematically catalog the whole sky. This amateur wound up making … Read more

If Galileo Galilei had never looked through a telescope, he still would have been considered a great scientist. His findings on the laws of motion set the stage for the work of Sir Isaac Newton one generation later. Galileo not only proved that weight does not affect how quickly objects fall, he also proved that … Read more

When Enrico Fermi was conducting his experiments with neutrons and the elements, he was looking for a better, artificial way to produce radioactivity, not nuclear fission. When he got to uranium, he was concerned that its very high level of radioactivity might harm his instruments. Fermi placed a sheet of aluminum foil between the uranium … Read more

Once the war was over, scientists could concentrate on other uses for this new source of tremendous amounts of energy. Nuclear power plants were built to use fission to produce electricity. There are now over 400 nuclear power plants in the world. France and Sweden produce nearly half their electricity with nuclear power. There are … Read more

In the early 1400s, a new number system was introduced into Europe from Arabia. The old Greek and Roman systems made calculations very difficult. Using the new Arabic numerals, only 10 different digits were needed to express any number. People at that time still depended on celestial movements to determine medical treatment and to predict … Read more

Around 270 B.C., the Greek astronomer Aristarchus proposed that Earth and the other planets revolved around a stationary Sun. He was dismissed as a madman, until Copernicus. Copernicus studied the movements of the planets in the 1,400 years since Ptolemy and found that Ptolemy’s idea of epicycles, secondary orbits within the main orbit, could not … Read more

When Christopher Columbus sailed to the New World in 1492 and proved Earth is a sphere, astronomers started thinking differently about Earth’s place in the universe. For 1,400 years the Ptolemaic system, with Earth at the center of the universe and all other celestial bodies revolving around it in transparent spheres, had remained unquestioned. The … Read more

The immediate reaction to Nicolaus Copernicus’s book on heliocentric cosmology was minimal. It opened the eyes of some scientists, but most people continued to believe in the Ptolemaic system, probably because it made humans seem more important. By the end of the 1500s, an Italian scientist and philosopher named Giordano Bruno started to teach the … Read more

Actually, Nicolaus Copernicus didn’t do much of anything with his experiments and findings. It took tremendous courage for him to conduct his experiments. He was defying Ptolemy, the church, and common sense. He did not want his discovery to cause any conflict, so when he had finished writing a book on his findings, he kept … Read more

When Kepler started his experiments, he knew he needed the most accurate measurements of the planets’ movements available. Tycho Brahe was a Danish astronomer who had his own observatory and the most advanced instruments of the time. He had giant sextants and quadrants and a tool called an equatorial armillary that measured the angles between … Read more

As brilliant as Copernicus’s theory about the movement of the planets was, he was still wrong about one vital issue: he thought their orbits were perfect circles. The idea that Earth was not the center of the universe and that planetary orbits were not circular was very hard to accept. It was frightening to many … Read more

The problem for Copernicus was that even though the circle was accepted as the shape of celestial orbits, careful measurements did not support it. Copernicus was never able to solve the problem, but Kepler had some extra information to work with. In the 60 years since Copernicus’s death, astronomers had continued to study the planets’ … Read more

In 1609, Galileo Galilei announced the discoveries he had made with his first telescope. Johannes Kepler was of course fascinated by the idea and wrote the first treatise on optics. His theories were basically correct and are still in use today. The study also included a discussion of the nature of light and proposed that … Read more

Johannes Kepler had no trouble combining his belief in science with his belief in God. He believed that God made the universe according to a mathematical plan. This led to his theory of perfect shapes and perfect numbers, something he called “the music of the spheres.” Kepler, like the ancient Greeks, believed in five perfect … Read more

According to Albert Einstein time travel is possible, but you can only travel forward in time. If a spaceship is traveling at the speed of light, time slows down for the spaceship and its passengers. Space travelers who travel to the nearest star system and return to Earth at this speed might have a few … Read more

Scientists debated the composition of light for centuries. Did it consist of waves like sound waves? Or was it matter? The Dutch scientist Christiaan Huygens proposed his wave theory of light in the late 1600s and used it to explain reflection and refraction. At about the same time, Sir Isaac Newton suggested that light was … Read more

As soon as scientists heard the equation E = mc2 in 1905, they knew it was only a matter of time before a weapon of tremendous power would be devised. In 1939, Albert Einstein was informed that scientists in Europe, including Germany, had discovered a way to release the atomic energy of the element uranium. … Read more

Enrico Fermi was born in Rome, Italy, in 1901. His family was poor, and Fermi was so shy that he had few friends. He would spend his time in used bookstores buying as many books as he could on his favorite subjects, math and physics. Throughout his education, he was far ahead of his classmates … Read more

In 1932, the English physicist Sir James Chadwick discovered that the nucleus of the atom consisted of another particle besides protons. He called the particles neutrons because they had a neutral charge, unlike the positively charged protons. At the time, the discovery did not make many headlines. Ernest Rutherford had predicted the neutron’s presence many … Read more

Enrico Fermi’s discovery of man made nuclear fission had two implications. If the reaction could be controlled, it would be a new source of tremendous amounts of power to produce electricity. Sustained fission could also produce the most destructive weapons ever made. The nuclear power plants would have to wait, World War II had just … Read more

Marie and Pierre Curie’s discovery of radioactivity was a breakthrough, but it was limited to a few elements. Enrico Fermi wanted to test all the elements, and he made one other key change. Fermi thought the newly discovered neutron would prove a better “bullet” than the positively charged alpha particles the Curies had used. He … Read more

James Clerk Maxwell made the first color photograph in history, and he was only 18 when he made it. While he was still at Edinburgh University, Maxwell decided to study how human eyes detect color. He was very interested in a theory that said that the eye has three types of fibers that are sensitive … Read more

One of the first questions James Clerk Maxwell tackled concerned the composition of Saturn’s rings. Are they solid or composed of countless separate particles? Maxwell first theorized that the rings could not be either uniformly solid or liquid because they would be unstable and would break up. He used mathematics to indicate that the only … Read more

James Clerk Maxwell’s findings about electromagnetism in the 1870s and Hertz’s discovery of radio waves in the 1880s made Nikola Tesla think that the possibilities of electricity were endless. Tesla’s next research was on high frequency electricity, but he had a problem. Even his advanced AC generators could only generate a current of about 20,000 … Read more

Tesla hated warfare, and one of his dreams was to find a scientific way to end it. He thought it could be reduced to “a mere spectacle of machines.” In 1934, he announced that he had found a way to do this. His invention was a weapon that could send through the air “concentrated beams … Read more

Thomas Edison’s invention of the lightbulb led to the creation of the Edison Power Company. He had a power plant in New York City, but it was huge and could only transmit power over one square mile through thick, dangerous cables. The problem was that Edison was using DC (direct current) power, a very inefficient … Read more

Nikola Tesla was one of the greatest scientific minds in history and one of the most imaginative inventors. Many of his ideas were so far ahead of their time that they remained misunderstood and unstudied. Tesla invented the radio, but the Italian inventor Guglielmo Marconi received credit for it. He discovered X rays, but German … Read more

Ernest Rutherford agreed with Curie that radioactive rays came from the atom, but what was the nature of these subatomic rays? Rutherford’s early research would answer this question. He placed a tray of uranium near the poles of a magnet and placed a photographic plate beyond the magnet. The radiation particles moved quickly between the … Read more

Science in the twentieth century was dominated by two pursuits: astronomers looked farther and farther into space to the very edge of the universe, and physicists looked deeper and deeper into matter at the smallest particles in the universe. Marie Curie gave the first hints of subatomic particles when she theorized that the atom was … Read more

Part of the reason Nikola Tesla has remained unappreciated as a scientist is that his ideas were so brilliant that they were far ahead of their time. Here are some examples. Tesla discovered the basic science behind radar, the electron microscope, and the microwave oven. Edison called his idea for radar “ridiculous,” so it was … Read more

Much of Albert Einstein’s theory of relativity is baffling even to other scientists. However, the more they studied it, particularly the mathematical equations he offered as proofs, the more they saw how accurate it was. Here are some of its basic points. Around 1900, the Dutch scientist Hendrik Lorentz worked out a formula showing that … Read more

One of the most startling discoveries in all scientific history was the amount of energy that is stored in matter. For example, if all the energy that is stored in just one pound of coal could be converted into energy, it would produce the amount of electricity the entire world uses in one day. This … Read more

In a way, Ernest Rutherford was the first successful alchemist. It started in 1901, when Rutherford noticed a strange property of the radioactive element thorium. As thorium gave off radiation, it also produced an invisible gas that was also radioactive. He studied the gas and devised a bold theory. Since radiation particles are coming from … Read more

Ernest Rutherford found that radioactive atoms release radiation in order to take on a more stable form. He called the process radioactive decay. As radioactive elements decay, they change into other elements until they are no longer radioactive, or are stable. Radioactive decay takes place at different rates in different elements. Rutherford called an element’s … Read more

In 1908, Ernest Rutherford conducted his greatest experiment. First, he directed alpha particles at several different materials and found that they passed through easily. Rutherford beat a piece of gold leaf into a thinness of one fifty-thousandth of an inch. He estimated that the gold leaf was now about 2,000 atoms thick. If atoms filled … Read more

In 1820, the Danish scientist Hans Christian Orsted was conducting an experiment with an electrical circuit. He noticed that when he turned the circuit on and off, a nearby compass needle jumped. He concluded that electricity produces magnetism, and the science of electromagnetism was born. The finding was interesting, but one English scientist realized it … Read more

Isaac Newton had tried for years to build a better telescope, and eventually built the first practical reflecting telescope. Like most astronomers of the day, he was troubled by the blurry images and the halos of color that lenses produced. Newton turned to a study of light to try to resolve the problem. In Newton’s … Read more

In 1696, the Swiss mathematician Johann Bernoulli challenged the scientists of the world to solve a problem he proposed. It was a very difficult problem, so he allowed six months for the solution. At the end of the six months, there were no solutions. The German mathematician, Gottfried Wilhelm Leibniz, who is given credit along … Read more

Newton finally published his scientific breakthroughs in 1687 in a three volume set called Principia Mathematica. It took him three years to write down his vast store of knowledge, but the book was immediately recognized at the time as the most important scientific work ever written. It was also the beginning of the science of … Read more

One simple experiment students often conduct is to place two magnets on a table with opposite poles facing each other but not touching. A piece of paper is placed on top of the magnets and iron filings are dropped on top of the paper above the magnets. Friction keeps the iron filings from moving much, … Read more

The experiment Michael Faraday devised in 1831 to bring about the conversion of magnetism to electricity, also known as electromagnetic induction, sounds very simple. In time, it led to the huge generators used today to make electric power. First, Faraday made a conductor for the electricity by winding 220 feet of copper wire around a … Read more

Michael Faraday was born in 1791 in Newington, near London, England. His father was a blacksmith and the family was very poor. There were times when the young Faraday had only bread to eat. Faraday’s family belonged to a small Christian sect called the Sandemanians. Its founder, Robert Sandeman, believed that the greatest achievement a … Read more

The substance was different from all other matter. It couldn’t be seen or felt or even measured, but it was present everywhere. It existed throughout space and even in vacuums. It was stationary and all bodies in space traveled through it. Its basic property was that it was luminiferous, it could carry light. It was … Read more

On Christmas morning in 1821, Michael Faraday had an unusual present for his wife. He led her to his laboratory, where he presented her with one of his experiments, but she had no idea what it was. There was a small container of mercury with a magnet attached to it. A copper rod was placed … Read more

The beginnings of Michael Faraday’s ideas about magnetism started over 200 years before in a book titled Of Magnets by English scientist William Gilbert. It was published in 1600 and was probably the first great scientific work written in England. Gilbert was a remarkable scientist who was centuries ahead of his time in many fields. … Read more

In 1798, the British scientist Benjamin Thompson, Count Rumford, proved that heat was a form of motion, not the weightless fluid of previous theories. By James Clerk Maxwell’s time, it was known that it was the atoms or molecules of the hot substance that were moving, but what was the nature of the movement? Did … Read more

Michael Faraday studied the lines that iron filings formed by magnets and saw lines of force spreading across the universe. He thought other forces, like gravity, electricity, and even light, all acted with these lines of force. He was right, but he could not work out the mathematical proof, or description, of his theory. James … Read more

A drug that kills bacteria is referred to as an antibiotic. Many antibiotics have been developed since Ehrlich founded chemotherapy and Alexander Fleming discovered the first antibiotic, penicillin, in 1928. There is a growing problem, however, with the use of antibiotics. They have been overused. Just as humans develop immunity to diseases, bacteria develop immunity … Read more

The human body’s immune response, using its own antibodies, was still not enough for many diseases. Common diseases like malaria, sleeping sickness, and syphilis are caused by bacteria and other infectious germs that the body’s “magic bullets” cannot destroy. Paul Ehrlich set out to create chemical “magic bullets” that would cure these kinds of diseases. … Read more

In 1890, another German researcher Emil von Behring, discovered that the blood of animals infected with different diseases contained chemicals that attacked the disease cells. He called these chemicals antibodies and found that they often provided immunity, or lifetime protection, against a disease after the first attack. Paul Ehrlich realized that this was how his … Read more

Isaac Newton’s first discovery concerned gravity. Scientists knew of gravity, and Johannes Kepler had theorized that it had something to do with the movement of the planets, but this was not enough for Newton. When he saw an apple fall from a tree at his family’s farm, he wanted to know the laws at work … Read more

In 1665, the bubonic plague swept over London, England, killing tens of thousands of people. To try to stop the spread of the disease, students were sent home from universities and were not able to return for 18 months. The time was a tragedy for England, but an amazing leap forward for the science world. … Read more

Considering all the discoveries that have been made since Dmitri Mendeleyev devised his periodic table, there have been few changes to his table. Fifty new elements have been added as they have been discovered, but the main change had to do with a new measure of the atom, the atomic number. Mendeleyev’s first periodic table … Read more

Dmitri Mendeleev was convinced he had uncovered the chemical “order” of the universe, but he had two problems. First, there were gaps in the table-places where elements were needed to complete the group. Mendeleyev simply said these were elements that had not yet been discovered. He said they would be discovered soon, and he predicted … Read more

Most scientific funding at the time was going toward the study of X rays. Marie Curie was much more interested in this new radiation and its source. The Curies were poor, so they had to take the only “lab” available to them, a cold, rundown shack near the Sorbonne. Curie’s first step in her research … Read more

It was not until the 1920s that scientists became aware of the dangers of working with radioactivity. Radioactive rays hold an incredible amount of fast-moving energy and easily penetrate human tissue. Once inside the body, the rays damage or destroy cells at a rapid rate. Radioactive substances can affect human bodies in different, unpredictable ways … Read more

In 1895, the German physicist Wilhelm Roentgen discovered X rays, a radiation that could penetrate most solid materials and expose photographic plates. Also, any gas, such as air, became electrified when struck by these rays. The discovery eventually led to the use of X rays to take pictures of the inside of the human body … Read more

Madame Curie had one of the most difficult lives of any of the amazing scientists that ever lived. Her mother died when she was just 10 years old. She was forced to leave her homeland because women were not allowed to attend college. She lived in poverty during her college years, often barely surviving on … Read more

Paul Ehrlich was born in Strehlin, Germany, in 1854. He received his medical degree from the University of Leipzig in 1878, but he was much more interested in research than opening up a practice. At the time, French chemist Louis Pasteur and German bacteriologist Robert Koch were each discovering the role bacteria played in disease, … Read more

By the 1850s, people still didn’t know exactly what caused disease. There were many theories, but none were based on scientific principles. In 1858, the German physician Rudolf Virchow offered the first clue with his cell theory. He said the cell, which Dutch inventor Antoni van Leeuwenhoek had seen 200 years earlier, was the basic … Read more

Marie Curie discovered that a small amount of radium would destroy human tissue. This meant it would be tremendously effective in treating many types of cancer by destroying cancerous tumors. Doctors immediately started treating cancer patients with radiotherapy, or Curie therapy as it was sometimes called. There was a problem, however. Many years later, it … Read more

Avogadro’s study of gases and atomic weights led him to two conclusions. First, the atoms of many elements actually occur in groups of two or more, called molecules. A molecule, which means “mass” in Latin, is the smallest unit of a substance that has all the chemical properties of that substance. For example, two oxygen … Read more

The discoveries of chemists like Dalton, Lavoisier, and Avogadro concerning atoms and atomic weights made it easier for scientists to detect new elements. In 1808, John Dalton created a table of the 21 known elements. By 1860 there were 63 known elements and chemists were beginning to notice similarities in the properties of some of … Read more

The confusion over atomic weights could have been cleared up decades earlier than it was, but no one was listening. The main reason was that the theory depended on the idea that identical atoms may combine with one another to form a molecule. Chemists at the time could not believe this, so Avogadro lived out … Read more

There were several reasons why Dmitri Mendeleev was able to put together a remarkably accurate periodic table. First, he used the new atomic weights calculated by Italian chemist Stanislao Cannizzaro. Cannizzaro had taken the new figures to the Karlsruhe Convention of chemists in 1860 to defend the still-unknown Avogadro and his molecular laws. Then, Mendeleyev … Read more

Dmitry Mendeleyev was born the youngest of 14 children in Tobolsk, Siberia, in 1834. His family had been pioneers in desolate Siberia, starting the first printing press, the first newspaper, and the first glass factory. Russia had been under the strict rule of monarchs called czars, since the sixteenth century and revolutionaries were starting to … Read more

After Avogadro’s law finally was accepted, some scientists tried to calculate how many molecules might be present in a specific weight of a substance. Eventually, they calculated that 22 liters of gas contains 602 billion trillion molecules. This is usually written as 6.02 x 10^23 (to the twenty-third power) and is referred to as Avogadro’s … Read more

Many scientists who make great leaps forward in their discoveries generate as many questions as they answer, like John Dalton and his atomic theory. Dalton had proven the existence of the atom, and his relative atomic weights were a brilliant start to measuring the atom, but questions remained. Scientists were still puzzled by the true … Read more

There are many examples of a scientist’s theory being rejected in his lifetime despite its accuracy. Sometimes, fellow scientists want to see a theory proven before they accept it. Louis Pasteur constantly had to prove his theories to his fellow scientists. Often, believers in organized religion feel threatened by findings that oppose their beliefs. Galileo … Read more

John Dalton was now convinced he had enough proof to back up an atomic theory. By 1803 he was lecturing on his theory, and by 1808 he had published his findings. His atomic theory states the following: All matter is made up of small, indivisible particles called atoms. Atoms of different elements have different properties, … Read more

John Dalton published his findings on atomic weights and his atomic theory in 1808 in A New System of Chemical Philosophy. The book also included a set of symbols for the elements to help explain his findings. In 1814, Swedish chemist Jons Berzelius improved on Dalton’s findings. He made some of the atomic weights more … Read more

Some of Antoine Lavoisier’s other discoveries were so far ahead of their time that his fellow scientists had trouble accepting them. He applied what he had learned about combustion and oxygen to the human body. As a result of his experiments, he knew that we take in oxygen through the air and exhale the waste … Read more

John Dalton couldn’t actually weigh atoms. The technology to do that was still over 100 years in the future, but he could do the next best thing. He could measure their relative atomic weights. Dalton first turned to the results of past studies. In 1799, the French chemist Joseph-Louis Proust followed the lead of Antoine … Read more

John Dalton was fascinated by Earth’s atmosphere. He called air “elastic fluid” and made his own weather instruments, barometers, thermometers, and rain gauges, to study it. Dalton made daily readings of the air for 57 years and recorded his findings in notebooks. In all, he recorded over 200,000 observations on the weather in these notebooks, … Read more

The theory of the atom would remain unproven until 1803, when an English scientist presented the proof. John Dalton was born in poverty in Eaglesfield, England, in 1766. He was such a genius at mathematics when he was young that the village allowed him to open up his own school at the age of 12. … Read more

The Greek philosopher, Democritus was called “the Laughing Philosopher” because he said the purpose of life was “to be cheerful.” Around 470 B.C., he proposed a theory that made others laugh at him. Democritus argued that all matter was made up of invisible particles he called atoms, from the Greek for “indivisible”, and that the … Read more

Antoine Lavoisier was heavily involved in many official duties for the French government. He was the leader of the commission set up to create a new system of weights and measures. The result was the metric system used in most of the world today. Despite his close ties to the government, Lavoisier was a strong … Read more

By 1770, Antoine Lavoisier was carefully studying how combustion worked. How did things burn and how did they rust? Stahl’s phlogiston theory was still accepted, but Lavoisier had a problem with it: the theory had never been proven with measurements. Two hundred years before, Galileo had stressed the importance of measurement in astronomy. Lavoisier wanted … Read more

In 1765, the French government asked a 22-year-old lawyer to make a study of the best way to light the streets of Paris at night. The young man made a close study of fuels and combustion, or burning. He found the best type of oil to burn for the streetlamps, the best time to light … Read more

With his new findings, Antoine Lavoisier was able to explain how metals were created from ores. The ores were a combination of metal and gas. When the ore was heated, usually with charcoal, the charcoal took the gas from the ore, leaving the pure metal behind. Lavoisier knew there was another piece of the puzzle … Read more

Antoine Lavoisier was a great admirer of the Swedish scientist Carolus Linnaeus, who started a classification system for biology. Inspired by Linnaeus, Lavoisier, and three other French chemists set up a new chemical naming system. An exact system of prefixes and suffixes would now clearly describe chemical compounds. For example, carbon dioxide contained twice as … Read more

\Joseph Priestley’s upbringing as a Dissenter stuck with him throughout his life. Priestley was a freethinker with bold ideas on science, theology, and politics. Despite his interest in experimental science, he remained a pastor his entire life. He wrote often on religion, including his very controversial History of Corruptions of Christianity. In this work, he … Read more

The Greeks had a myth to explain the beginning of the universe. They said it started with thin matter without structure that spread out everywhere. They called this original matter “chaos.” When the alchemist Jan van Helmont started noticing these airlike substances, he thought that chaos would be a good name for them. However, Helmont … Read more

In all, Joseph Priestley discovered nine gases. He did not know what these gases were, but he isolated them and described their properties. One of these discoveries could have disproven an incorrect theory called the phlogiston theory of fire, but Priestley drew the wrong conclusion from a successful experiment. The phlogiston theory was developed in … Read more

Joseph Priestley’s next door neighbor in Leeds was a brewery. He became fascinated by the gases that rose out of the beer vats and thought of Helmont’s desire to capture gases. Some scientists tried to capture gases using a bent pipe and an upside-down water-filled bottle. The gas was supposed to rise up through the … Read more

Modern chemistry had its beginnings in the strange practices of alchemy. Alchemy got its name from an Arabic word meaning “Egypt” because at first it was a secret cult of Egyptian priests. From their studies, the priests learned glassmaking, metalworking, and methods of preserving mummies. By the time alchemy reached Europe centuries later, alchemists had … Read more

Joseph Priestley was born in Leeds, England, in 1733. Priestley was raised by an aunt who was a member of a religious group called the Dissenters. The freethinking group rejected many of the beliefs of the Church of England and gave Priestley a spirit of rebellion that would stick with him throughout his life. Priestley … Read more

Birute Galdikas was born in Wiesbaden, Germany, in 1946. She also had an interest in animals from an early age and was especially fascinated by orangutans. Along with chimps and gorillas, orangutans are humans’ closest living relatives. Galdikas’s family moved from Germany to Canada and then to the United States, and Galdikas studied anthropology at … Read more