Calories (Units of Energy)

“All forms of energy and mechanical work are equivalent and can be converted from one form to an other.”

  • Who discovered it?: James Joule
  • Year of Discovery: 1843

How was it Discovered?

A portrait for James Joule

We now know that mechanical work, electricity, momentum, heat, magnetic force,
etc., can be converted from one to another.

There is always a loss in the process, but it can be done. That knowledge has been a tremendous help for the development of our industries and technologies. Only 200 years ago, the thought had not occurred to anyone.

James Joule discovered that every form of energy could be con verted into an equivalent amount of heat. In so doing, he was the first scientist to come to grips with the general concept of energy and of how different forms of energy are equivalent to each other. Joule’s discovery was an essential foundation for the discovery (40 years later) of the law of conservation of energy and for the development of the field of thermodynamics.

Born on Christmas eve, 1818, James Joule grew up in a wealthy brewing family in Lancashire, England. He studied science with private tutors and, at the age of 20, started to work in the family brewery.

Joule’s first self-appointed job was to see if he could convert the brewery from steam power to new, “modern” electric power. He studied engines and energy supplies. He studied electrical energy circuits and was fascinated to find that the electrical wires grew hot when current ran through them. He realized that some of the electrical energy was being converted into heat.

He felt it was important for him to quantify that electrical energy loss and began experiments on how energy was converted from electricity to heat. Often he experimented with little regard for safety—his or others. More than once, a servant girl collapsed unconscious from electrical shocks during these experiments. While he never converted the brewery to electrical power, these experiments turned his focus to the process of converting energy from one form to another.

Joule was deeply religious, and it seemed right to him that there should be a unity for all the forces of nature. He suspected that heat was somehow the ultimate and natural form for calculating the equivalence of different forms of energy.

Joule turned his attention to the conversion of mechanical energy into heat. In real life a moving body (with the mechanical energy of momentum) eventually stopped. What happened to its energy? He designed a series of experiments using water to measure the conversion of mechanical motion into heat.

Two of Joule’s experiments became famous. First, he submerged an air filled copper cylinder in a tub of water and measured the water temperature. He then pumped air into the cylinder until it reached 22 atmospheres of pressure. The gas law said that the mechanical work to create this increased air pressure should create heat. But would it? Joule measured a 0.285°F rise in water temperature. Yes, mechanical energy had been converted to heat.

Next, Joule attached paddles onto a vertical shaft that he lowered into a tub of water. Falling weights (like on a grandfather clock) spun the paddles through the tub’s water. This mechanical effort should be partially converted to heat. But was it?

His results were in conclusive until Joule switched from water to liquid mercury. With this denser fluid, he easily proved that the mechanical effort was converted to heat at a fixed rate. Liquid was heated by merely stirring it.

Joule realized that all forms of energy could be converted into equivalent amounts of heat. He published these results in 1843 and introduced standard heat energy units to use for calculating these equivalences. Since then, physicists and chemists typically use these units and have named them joules.

Biologists prefer to use an alternate unit called the calorie (4.18 joules = 1 calorie). With this discovery that any form of energy could be converted into an equivalent amount of heat energy, Joule provided a way to advance the study of energy, mechanics, and technologies.

Fun Facts: The calories on a food package are actually kilocalories, or units of 1,000 calories. A kilocalorie is 1,000 times larger than the calorie used in chemistry and physics. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. If you burn up 3,500 calories during exercise, you will have burned up and lost one pound. However, even vigorous exercise rarely burns more than 1,000 calories per hour.


“Microorganisms too small to be seen or felt exist everywhere in the air and cause disease and food spoilage.”

  • Who Discovered it?: Louis Pasteur
  • Year of Discovery: 1856

How was it Discovered?


In the fall of 1856, 38-year-old Louis Pasteur was in his fourth year as Director of Scientific Affairs at the famed Ecole Normale in Paris. It was an honored administrative position. But Pasteur’s heart was in pure research chemistry and he was angry.

Many scientists believed that microorganisms had no parent organism. Instead, they spontaneously generated from the decaying molecules of organic matter to spoil milk and rot meat. Felix Pouchet, the leading spokesman for this group, and had just published a paper claiming to prove this thesis.

Pasteur thought Pouchet’s theory was rubbish. Pasteur’s earlier discovery that microscopic live organisms (bacteria called yeasts) were always present during, and seemed to cause, the fermentation of beer and wine, made Pasteur suspect that microorganisms lived in the air and simply fell by chance onto food and all living matter, rapidly multiplying only when they found a decaying substance to use as nutrient.

Two questions were at the center of the argument. First, did living microbes really float in the air? Second, was it possible for microbes to grow spontaneously (in a sterile environment where no microbes already existed)?

Pasteur heated a glass tube to sterilize both the tube and the air inside. He plugged the open end with guncotton and used a vacuum pump to draw air through the cotton filter and into this sterile glass tube.

Pasteur reasoned that any microbes floating in the air should be concentrated on the outside of the cotton filter as the air was sucked through it. Bacterial growth on the filter indicated microbes floating freely in the air. Bacterial growth in the sterile interior of the tube meant spontaneous generation.

After 24 hours the outside of his cotton wad turned dingy gray with bacterial growth while the inside of the tube remained clear. Question number 1 was answered. Yes, microscopic organisms did exist, floating, in the air. Any time they concentrated (as on a cotton wad) they began to multiply.

Now for question number 2. Pasteur had to prove that microscopic bacteria could not spontaneously generate.

Pasteur mixed a nutrient-rich bullion (a favorite food of hungry bacteria) in a large beaker with a long, curving glass neck. He heated the beaker so that the bullion boiled and the glass glowed. This killed any bacteria already in the bullion or in the air inside the beaker. Then he quickly stoppered this sterile beaker. Any growth in the beaker now had to come from spontaneous generation.

He slid the beaker into a small warming oven, used to speed the growth of bacterial cultures.

Twenty-four hours later, Pasture checked the beaker. All was crystal clear. He checked every day for eight weeks. Nothing grew at all in the beaker. Bacteria did not spontaneously generate. Pasteur broke the beaker’s neck and let normal, unsterilized air flow into the beaker. Seven hours later he saw the first faint tufts of bacterial growth. Within 24 hours, the surface of the bullion was covered.

Pouchet was wrong. Without the original airborne microbes floating into contact with a nutrient, there was no bacterial growth. They did not spontaneously generate.

Pasteur triumphantly published his discoveries. More important, his discovery gave birth to a brand new field of study, microbiology.


Fun Facts: The typical household sponge holds as many as 320 million disease-causing germs.

Doppler Effect

“Sound- and light-wave frequencies shift higher or lower depending on whether the source is moving toward or away from the observer.”

  • Who Discovered it?: Christian Doppler
  • Year of the Discovery: 1848

How was it Discovered?


Austrian-born Christian Doppler was a struggling mathematics teacher—struggling both because he was too hard on his students and earned the wrath of parents and administrators and because he wanted to fully understand the geometry and mathematical concepts he taught. He drifted in and out of teaching positions through the 1820s and 1830s as he passed through his twenties and thirties. Doppler was lucky to land a math teaching slot at Vienna Polytechnic Institute in 1838.

By the late 1830s, trains capable of speeds in excess of 30 mph were dashing across the countryside. These trains made a sound phenomenon noticeable for the first time. Never before had humans traveled faster than the slow trot of a horse. Trains allowed people to notice the effect of an object’s movement on the sounds that the object produced.

Doppler intently watched trains pass and began to theorize about what caused the sound shifts he observed. By 1843 Doppler had expanded his ideas to include light waves and developed a general theory that claimed that an object’s movement either increased or decreased the frequency of sound and light it produced as measured by a stationary observer. Doppler claimed that this shift could explain the red and blue tinge to the light of distant twin stars. (The twin circling toward Earth would have its light shifted to a higher frequency—toward blue. The other, circling away, would shift lower, toward red.)

In a paper he presented to the Bohemian Scientific Society in 1844, Doppler presented his theory that the motion of objects moving toward an observer compresses sound and light waves so that they appear to shift to a higher tone and to a higher frequency color (blue). The reverse happened if the object was moving away (a shift toward red). He claimed that this explained the often observed red and blue tinge of many distant stars’ light. Actually, he was wrong. While technically correct, this shift would be too small for the instruments of his day to detect.

Doppler was challenged to prove his theory. He could n’t with light because telescopes and measuring equipment were not sophisticated enough. He decided to demonstrate his principle with sound.

In his famed 1845 experiment, he placed musicians on a railway train playing a single note on their trumpets. Other musicians, chosen for their perfect pitch, stood on the station platform and wrote down what note they heard as the train approached and then receded. What the listeners wrote down was consistently first slightly higher and then slightly lower than what the moving musicians actually played.

Doppler repeated the experiment with a second group of trumpet players on the station platform. They and the moving musicians played the same note as the train passed. Listeners could clearly hear that the notes sounded different. The moving and stationary notes seemed to interfere with each other, setting up a pulsing beat.

Having proved the existence of his effect, Doppler named it the Doppler Shift. However, he never enjoyed the fame he sought. He died in 1853 just as the scientific community was beginning to accept and to see the value of, his discovery.

The Doppler Effect is one of the most powerful and important concepts ever discovered for astronomy. This discovery allowed scientists to measure the speed and direction of stars and galaxies many millions of light years away. It unlocked mysteries of distant galaxies and stars and led to the discovery of dark matter and of the actual age and motion of the universe. Doppler’s discovery has been used in the research efforts of a dozen scientific fields.

Few single concepts have ever proved more useful. Doppler’s discovery is considered to be so fundamental to science that it is included in virtually all middle and high school basic science courses.



Fun Facts: Doppler shifts have been used to prove that the universe is expanding. A convenient analogy for the expansion of the universe is a loaf of unbaked raisin bread. The raisins are at rest relative to one another in the dough before it is placed in the oven. As the bread rises, it also expands, making the space between the raisins increase. If the raisins could see, they would observe that all the other raisins were moving away from them although they themselves seemed to be stationary within the loaf. Only the dough—their “universe”—is expanding.

Electrochemical Bonding

Molecular bonds between chemical elements are electrical in nature

  • Who Discovered it?: Humphry Davy.
  • Year of Discovery: 1806

How was it Discovered?

Davy discovered that the chemical bonds between individual atoms in a molecule are electrical in nature. We now know that chemical bonds are created by the sharing or transfer of electrically charged particles—electrons—between atoms. In 1800, the idea that chemistry somehow involved electricity was a radical discovery.250px-Sir_Humphry_Davy,_Bt_by_Thomas_Phillips

Humphry Davy was born in 1778 along the rugged coast of Cornwall, England. He received only minimal schooling and was mostly self-taught. As a young teenager, he was apprenticed to a surgeon and apothecary. But the early writings of famed French scientist Antoine Lavoisier sparked his interest in science.

In 1798 Davy was offered a chance by wealthy amateur chemist Thomas Beddoes to work in Bristol, England, at a new lab Beddoes built and funded. Davy was free to pursue chemistry-related science whims. He experimented with gases in 1799, thinking that the best way to test these colorless creations was to breathe them. He sniffed nitrous oxide (N2O) and passed out, remembering nothing but feeling happy and powerful. After he reported its effect, the gas quickly became a popular party drug under the name “laughing gas.” Davy used nitrous oxide for a wisdom tooth extraction and felt no pain.

Even though he reported this in an article, it was another 45 years before the medical profession finally used nitrous oxide as its first anesthetic.

Davy also experimented with carbon dioxide. He breathed it and almost died from carbon dioxide poisoning. A born showman, movie-star handsome, and always fashionably dressed, Davy delighted in staging grand demonstrations of each experiment and discovery for thrilled audiences of public admirers.

In 1799, Italian Alessandro Volta invented the battery and created the world’s first manmade electrical current. By 1803, Davy had talked Beddoes into building a giant “Voltaic Pile” (battery) with 110 double plates to provide more power. Davy turned his full attention to experimenting with batteries. He tried different metals and even charcoal for the two electrodes in his battery and experimented with different liquids (water, acids, etc.) for the liquid (called an electrolyte) that filled the space around the battery’s plates.

In 1805 Davy noticed that a zinc electrode oxidized while the battery was connected.  That was a chemical reaction taking place in the presence of an electrical current. Then he noticed other chemical reactions taking place on other electrodes. Davy realized that the battery (electric current) was causing chemical reactions to happen.

As he experimented with other electrodes, Davy began to realize the electrical nature of chemical reactions. He tried a wide variety of materials for the two electrodes and different liquids for the electrolyte.

In a grand demonstration in 1806, Davy passed a strong electric current through pure water and showed that he produced only two gasses—hydrogen and oxygen. Water molecules had been torn apart by an electric current. This demonstration showed that an electrical force could tear apart chemical bonds. To Davy, this meant that the original chemical bonds had to be electrical in nature or an electric current couldn’t have ripped them apart.

Davy had discovered the basic nature of chemical bonding. Chemical bonds were somehow electrical. This discovery radically changed the way scientists viewed the formation of molecules and chemical bonds.

Davy continued experiments, passing electrical currents from electrode to electrode through almost every material he could find. In 1807 he tried the power of a new battery with 250 zinc and copper plates on caustic potash and isolated a new element that burst into brilliant flame as soon as it was formed on an electrode. He named this newly discovered element; PotassiumA month later he isolated Sodium. Davy had used his grand discovery to discover two new elements.

Davy’s discovery started the modern field of electrochemistry and redefined science’s view of chemical reactions and how chemicals bond together. Not to mention that he discovered the two new very important elements, Potassium, and Sodium.

Fun Facts: A popular use of electrochemical bonding is in cookware. The process unites the anodized surface with the aluminum base, creating a nonporous surface that is 400 percent harder than aluminum.


An atom is the smallest particle that can exist of any chemical element.

  • Who discovered it?: John Dalton
  • Year of Discovery: 1802

How was it Discovered?


In the fifth century B.C.Leucippus of Miletus and Democritus of Abdera theorized that each form of matter could be broken into smaller and smaller pieces. They called that smallest particle that could no longer be broken into smaller pieces an atomGalileo and Newton both used the term atom in the same general way. Robert Boyle and Antoine Lavoisier were the first to use the word element to describe one of the newly discovered chemical substances. All of this work, however, was based on general philosophical theory, not on scientific observation and evidence.

John Dalton was born in 1766 near Manchester, England, and received a strict Quaker upbringing. With little formal education, he spent 20 years studying meteorology and teaching at religious, college-level schools. Near the end of this period, Dalton joined and presented a variety of papers to the Philosophical Society. These included papers on the barometer, the thermometer, the hygrometer, rainfall, the formation of clouds, evaporation, atmospheric moisture, and dewpoint. Each paper presented new theories and advanced research results.

Dalton quickly became famous for his innovative thinking and shifted to science research full time. In 1801 he turned his attention from the study of atmospheric gasses to chemical combinations. Dalton had no experience or training in chemistry. Still, he ploughed confidently into his studies.

By this time almost 50 chemical elements had been discovered—metals, gasses, and nonmetals. But scientists studying chemistry were blocked by a fundamental question they couldn’t answer: How did elements actually combine to form the thousands of compounds that could be found on Earth? For example, how did hydrogen (a gas) combine with oxygen (another gas) to form water (a liquid)? Further, why did exactly one gram of hydrogen always combine with exactly eight grams of oxygen to make water—never more, never less?

Dalton studied all of the chemical reactions he could find (or create), trying to develop a general theory for how the fundamental particle of each element behaved. He compared the weights of each chemical and the likely atomic structure of each element in each compound. After a year of study, Dalton decided that these compounds were defined by simple numerical ratios by weight. This decision allowed him to deduce the number of particles of each element in various well-known compounds (water, ether, etc.).

Dalton theorized that each element consisted of tiny, indestructible particles that were what combined with other elements to form compounds. He used the old Greek word, atom, for these particles. But now it had a specific chemical meaning.

Dalton showed that all atoms of any one element were identical so that any of them could combine with the atoms of some other element to form the known chemical compounds. Each compound had to have a fixed number of atoms of each element. Those fixed ratios never changed. He deduced that compounds would be made of the minimum number possible of atoms of each element. Thus water wouldn’t be H4O2 because H2O was simpler and had the same ratio of hydrogen and oxygen atoms.

Dalton was the first to use letter symbols (H, O, etc.) to represent the various elements. Scientists readily accepted Dalton’s theories and discoveries, and his concepts quickly spread across all Western science. We still use his concept of an atom today.

“Since atoms are the key to understanding chemistry and physics, Dalton’s discovery of the atom ranks as one of the greatest turning points in science. Because of this discovery, Dalton is often called the father of modern physical science.”

Oceans control Global Weather

By pumping massive amounts of heat through the oceans, vast ocean currents control weather and climate on land.

  • Who Discovered it: Benjamin Franklin.
  • Year of Discovery: 1770


How was it Discovered?

The Atlantic Ocean’s Gulf Stream is the most important of our world’s ocean currents. It is a major heat engine, carrying massive amounts of warm water north to warm Europe. It has directed the patterns of ocean exploration and commerce and may be a major determinant of the onset of ice ages. Finally, it is the key to understanding global circulation patterns and the inter-connectedness of the world’s oceans, weather, and climates.

American statesman, inventor, and scientist Benjamin Franklin conducted the first scientific investigation of the Gulf Stream and discovered its importance to Earth’s weather and climate. His work launched a scientific study of ocean currents, ocean temperature, the interaction of ocean current with winds, and the effect of ocean currents on climate. Franklin’s discoveries mark the beginnings of modern oceanographic science.

Benjamin Franklin set out to map the Gulf Stream in order to speed transatlantic shipping. He wound up discovering that ocean currents are a major controlling factor of global climate and weather.

Ocean surface currents were noted by early Norse sailors as soon as they sailed the open Atlantic. Columbus and Ponce de Leon described the Gulf Stream current along the coast of Florida and in the strait between Florida and Cuba. Others noted North Atlantic currents over the next hundred years. However, no one charted these currents, recorded them on maps, or connected the individual sightings into a grand, ocean-wide system of massive currents.

In 1769 British officials in Boston wrote to London complaining that the British packets (small navy ships that brought passengers and mail to the colonies) took two weeks longer in their trans-Atlantic crossing than did American merchant ships. Benjamin Franklin, an American representative in London at the time, heard this report and refused to believe it. Packet ships rode higher in the water, were faster ships, and were better crewed than heavy Rhode Island merchant ships.

Franklin mentioned the report to a Rhode Island merchant captain off-loading cargo in London. This captain said it was absolutely true and happened because Rhode Island whalers had taught American merchant captains about the Gulf Stream, a 3 mph current that spread eastward from New York and New England toward England. American captains knew to curve either north or south on westward trips to avoid fighting this powerful current.

When Franklin checked, the Gulf Stream didn’t appear on any maps, nor did it appear in any of the British Navy shipping manuals. Franklin began interviewing merchant and whaling captains, recording on maps and charts their experience with the Gulf Stream current. Whalers, especially, knew the current well because whales tended to congregate along its edges.

By 1770 Franklin had prepared detailed maps and descriptions of this current. British Navy and merchant captains, however, didn’t believe him and refused to review his information. By 1773 rising tensions between England and the colonies made Franklin withhold his new findings from the British.

Franklin began taking regular water temperature readings on every Atlantic Ocean crossing. By 1783 he had made eight crossings, carefully plotting the exact course his ship took each time and marking his temperature readings on the ship’s map.

On his last voyage from France to America, Franklin talked the ship’s captain into tracking the edge of the Gulf Stream current. This slowed the voyage as the ship zigzagged back and forth using the warm water temperature inside the Gulf Stream and the colder water temperature outside it to trace the current’s boundary.

The captain also allowed Franklin to take both surface and subsurface (20 and 40 fathoms) temperature readings. Franklin was the first to consider the depth (and thus the volume) of an ocean current.

Franklin discovered that the Gulf Stream poured masses of warm water (heat) from the tropical Caribbean toward northern Europe to warm its climate. He began to study the interaction between wind and current and between ocean currents and weather. Through the brief papers he wrote describing the Gulf Stream data he had collected, Franklin brought science’s attention and interest to ocean currents and their effect on global climate.

Franklin’s description of the Gulf Stream was the most detailed available until German scientist Alexander von Humbolt published his 1814 book about the Gulf Stream based on his measurements from more than 20 crossings. These two sets of studies represent the beginnings of modern oceanographic study.

Fun Fact: The Gulf Stream is bigger than the combined flow of the Mississippi, the Nile, the Congo, the Amazon, the Volga, the Yangtze, and virtually every other major river in the world.

Distance to the Sun

“The first accurate calculation of the distance from the earth to the sun, of the size of the solar system, and even of the size of the universe.”

  • Who Discovered it: Giovanni Cassini
  • Year of Discovery: 1672

How was it Discovered?


Our understanding of the universe depends on two foundations—our ability to measure the distances to faraway stars, and our ability to measure the chemical composition of stars. The discovery that allowed scientists to determine the composition of stars is described in the 1859 entry on spectrographs. The distance to the sun has always been regarded as the most important and fundamental of all galactic measurements. Cassini’s 1672 measurement, however, was the first to accurately estimate that distance.

Cassini’s discovery also provided the first shocking hint of the truly immense size of the universe and of how small and insignificant Earth is. Before Cassini, most scientists believed that stars were only a few million miles away. After Cassini, scientists realized that even the closest stars were billions (if not trillions) of miles away!
Born in 1625, Giovanni Cassini was raised and educated in Italy. As a young man, he was fascinated by astrology, not astronomy, and gained widespread fame for his astrological knowledge. Hundreds sought his astrological advice even though he wrote papers in which he proved that there was no truth to astrological predictions.
In 1668, after conducting a series of astronomical studies in Italy that were widely praised, Cassini was offered a position as the director of the Paris Observatory. He soon decided to become a French citizen and changed his name to Jean Dominique Cassini.
With an improved, high-powered telescope that he carefully shipped from Italy, Cassini continued a string of astronomical discoveries that made him one of the world’s most famous scientists. These discoveries included the rotational periods of Mars and Saturn, and the major gaps in the rings of Saturn—still called the Cassini gaps.
Cassini was also the first to suspect that light travelled at a finite speed. Cassini refused to publish his evidence, and later even spent many years trying to disprove his own theory. He was a deeply religious man and believed that light was of God. Light, therefore, had to be perfect and infinite, and not limited by a finite speed of travel. Still, all of his astronomical work supported his discovery that light travelled at a fixed and finite speed.
Because of his deep faith in the Catholic Church, Cassini also believed in an Earth-centered universe. By 1672, however, he had become at least partially convinced by the early writing of Kepler and by Copernicus’s careful arguments to consider the possibility that the sun lay at the centre.
This notion made Cassini decide to try to calculate the distance from the earth to the sun. However, it was difficult and dangerous to make direct measurements of the sun (one could go blind). Luckily, Kepler’s equations allowed Cassini to calculate the distance from the earth to the sun if he could measure the distance from the earth to any planet.
Mars was close to Earth and well-known to Cassini. So he decided to use his improved telescopes to measure the distance to Mars. Of course, he couldn’t actually measure that distance. But if he measured the angle to a spot on Mars at the same time from two different points on Earth, then he could use these angles and the geometry of triangles to calculate the distance to Mars.
To make the calculation work, he would need to make that baseline distance between his two points on Earth both large and precisely known. He sent French astronomer Jean Richer to Cayenne in French Guiana off the north coast of South America. Cassini stayed in Paris.
On the same August night in 1672, at exactly the same moment, both men measured the angle to Mars and placed it exactly against the background of distant stars. When Richer returned to Paris with his readings, Cassini was able to calculate the distance to Mars. He then used Kepler’s equations to discover that the distance to the sun had to be 87 million miles (149.6 million km). Modern science has found that Cassini’s calculation was only 7 percent of the true distance (just over 93 million miles).

Cassini went on to calculate the distances to other planets and found that Saturn lay a staggering 1,600,000,000 (1.6 billion) miles away! Cassini’s discoveries of distance meant that the universe was millions of times bigger than anyone had dreamed.


Fun Facts: The sun’s diameter is 1.4 million km (875,000 miles). It is approximately 109 times wider than the earth.