Annie Jump Cannon


Born: Dec 11, 1863 in Dover, Delaware
Died: Apr 13, 1941 (at age 77)
Nationality: American
Famous For: Stellar classification
Awards: Henry Draper Medal (1931)

Annie Jump Cannon was a Delaware-born astronomer who discovered at least 300 variable stars. These are stars that change their brightness or magnitude over time. These discoveries made Cannon a vital part of the evolution of stellar classification. She also discovered five new stars and a double star and analyzed over a quarter of a million stars to show the relationship between their spectral type, brightness, and distribution.

She also compiled a bibliography of 100,000 references to variable stars. In 1896 she joined the staff of the Harvard Observatory.

Cannon’s Early Years

Annie Jump Cannon was born in Dover, Delaware, the daughter of a state senator and a mother who kindled Cannon’s interest in the stars. She attended Wilmington Conference Academy and then went to Wellesley College, one of the so-called “seven sisters” colleges for women. While there, Cannon contracted scarlet fever, which destroyed much of her hearing. Still, she graduated from Wellesley and went to Europe to experience the 1892 solar eclipse.

When Cannon returned, she found few opportunities available to her, both because she was a woman and because of her partial deafness. Finally, after the death of her mother, Cannon wrote to her physics teacher at Wellesley and asked if there was the possibility of employment for her. Her old professor, Sarah Whiting, hired Cannon on as her assistant. Cannon took advantage of her position to audit graduate courses. She was especially enthusiastic about the astronomy course.

Cannon’s Collaboration with Pickering

Cannon studied spectroscopy, which is a science that deals with how radiant energy and matter interact. In those days, however, it was the study of how visible light could be separated into its component colors when it was passed through a prism. Cannon also took up photography, which was a new and fascinating art form at the time. She took graduate courses in astronomy and physics and entered Radcliffe College so she could use Harvard’s famous observatory. While there, she caught the attention of Edward C. Pickering, who was the observatory’s director. He was impressed with her knowledge and hired her on as an assistant in the observatory.

Classifying the Stars

Pickering had a coterie of female assistants known as Pickering’s women, or conversely, Pickering’s Harem. He hired these women to map the stars and complete what was called the Draper Catalogue. The goal of this catalogue was to map every star in the sky that had a magnitude up to +9.

These stars were to be classified by their spectra, which at the time was difficult. Pickering picked women for this task because he thought they were more efficient and patient than men and he knew that women also worked for less pay.

When a dispute arose as to how to classify the stars, Cannon created a compromise that divided the stars into the now famous OBAFGKM classification that is based on their temperatures. Cannon kept up her work in stellar classification for over 40 years and died in 1941 after she had been named the William C. Bond Astronomer at Harvard. She also was the only sole woman to be honored with the Henry Draper Award.

Carl Sagan


Born: Nov 9, 1934 in Brooklyn, New York, U.S.
Died: Dec 20, 1996 (at age 62) in Seattle, Washington, U.S.
Nationality: American
Famous For: Search for Extra-Terrestrial Intelligence (SETI), Cosmos: A Personal Voyage, Cosmos
Awards: NASA Distinguished Public Service Medal (1977), Pulitzer Prize for General Non-Fiction (1978), Oersted Medal (1990)

Carl Sagan, an astronomer, cosmologist, and astrophysicist, was born in Brooklyn, New York, in on November 9, 1934. He spent most of his career as a professor at Cornell University where he also directed other studies. During his time, he made over 600 scientific publications and he also wrote and edited more than 20 scientific books. In addition, he advocated scientific skeptical inquiries and methods, promoted and pioneered exobiology, and promoted the SETI (Search for Extra Terrestrial Intelligence).

Early Life

Sagan graduated from the University of Chicago where he studied extraterrestrial intelligence and planets. Before then, he graduated from Rahway High School in New Jersey in 1951. Carl was raised with his sister, Carol, in Brooklyn’s Bensonhurst neighborhood and his father, Samuel Sagan, was a Russian immigrant worker in the United States. Even at a young age, Sagan was so eager to become a scientist. This idea was driven by a science book he read about how the sun was close to the earth.

Sagan’s Career

Carl Sagan was an astronomer who excelled at explaining the most complicated ideas in a simplified manner that was easy to understand. He was once described by Isaac Asimov as one of the only two people he had ever met with higher intelligence than his.

While attending the Chicago University, Sagan participated in the Ryerson Astronomical Society in 1954 and received a bachelor of arts in “nothing,” as he described it. In 1955, he received a bachelor of science in physics and in 1956, he obtained a master’s in physics before earning his astronomy and astrophysics Ph.D. in 1960.

Sagan’s Contributions to Astronomy

Besides his popularity in science books and the award winning Cosmos TV series, Carl made tremendous contributions to the field of astronomy. In the 1950s, he helped design mechanical devices that were used on space flights. He also published two crucial theories that were confirmed by space flights.

One of Sagan’s theories was that the planet Venus was very hot. The other one stated that Mars did not have a season where plants could be grown, contrary to what other scientists had believed at the time. He explained that the dark areas of Mars that were thought to be plants were simply gigantic dust storms in the Martian atmosphere.

Sagan was also involved in efforts of the Americans trying to explore the other planets in the solar system. He was one of the members of the Mariner-Nine to Mars voyage, which was the first vehicle to orbit a different planet. He also helped in choosing the landing area for Viking One and Two, which were the first two vehicles to land on Mars. In addition to these, he worked on Pioneer Two, which was the first space vehicle that was to investigate Jupiter, and the Pioneer 11 which flew past Saturn and Jupiter.

Sagan’s Death

Before his death on December 20, 1996, Carl Sagan served as the Duncan David Professor of Astronomy and Space Sciences as well as the Director of Laboratory for Planetary Science Studies at the University of Cornell. He died of pneumonia in Seattle, Washington.

Caroline Herschel


Born: Mar 16, 1750 in Hanover, Germany
Died: Jan 9, 1848 (at age 97) in Hanover, Germany
Nationality: German
Famous For: discovery of comets
Awards: Astronomical Society (1828), Prussian Gold Medal for Science (1846)

Caroline Herschel was an astronomer in the late 18th and early 19th centuries who lived in both England and Germany. Her older brother was the renowned astronomer Sir William Herschel, and the two siblings worked in close partnership for a number of years.

Caroline was particularly known for discovering a number of comets, one of which was named after her. Her personal life was sometimes difficult due to the after effects of typhus, which she contracted at age 10 and which severely stunted her growth.

Early Life

Herschel was born in Germany, and spent her entire childhood there. In her early 20s, she accompanied her brother to Bath, England, where William had obtained a job teaching music. Caroline proved herself to be an impressive singer, to the extent that she acquired a considerable reputation and was asked to perform publicly. However, she was uncomfortable with Bath society and was somewhat isolated socially.

When William began studying astronomy as a hobby he fit around his musical commitments, Caroline quickly joined him. At first, the pair worked on the development of more powerful telescopes. Despite her typhus-ravaged body, she possessed immense dexterity, which allowed her to set up telescopes effectively.

Caroline also worked as a record-keeper and organizer, categorizing her brother’s copious notes. This work increased her own levels of interest in astronomy and by 1782, she was performing her own observations.

Caroline’s Contributions to Astronomy

After William had advised her to spend time learning to understand astronomy rather than simply observing it, Caroline Herschel discovered a number of comets. She also made history in that she was the first woman to be paid for her scientific work, something that was rare in the 1780s, even for men.

However, her brother’s marriage in 1788 reputedly upset her and led to their partnership becoming strained, eventually breaking down altogether. Science benefited from her domestic problems, since she threw herself into increasingly independent research and observation.

Most of Caroline Herschel’s observations in the 1780s were carried out with a 27-inch Newtonian telescope. With this she discovered M110, the Andromeda Galaxy’s second known companion. This was probably her most significant discovery during this period.

In addition, she discovered eight comets, five of which were certainly unknown to any previous astronomer. In 1798, at the recommendation of her brother, Caroline drew up a new star catalog, which the Royal Society published in 1798 as a considerable improvement to John Flamsteed’s previous catalog.

Caroline’s Later Years and Honors

After William died in 1822, Caroline moved back to Germany, although she continued her astronomical work in Hanover for several years. In 1828, she became the first woman to be awarded the Gold Medal of the Royal Astronomical Society and would remain the only female recipient of this honor for more than 170 years.

Herschel was given an honorary membership of the society in 1835. She lived into her late 90s, with the King of Prussia bestowing his own Gold Medal on her in 1846 for her work in the cataloging and categorization of nebulae. Herschel died in Hanover on January 9, 1848. A small asteroid and a crater on the moon are both named in her honor.

Charles Messier


Born: Jun 26, 1730 in Badonviller, France
Died: Apr 12, 1817 (at age 86) in Paris, France
Nationality: French
Famous For: Messier catalog
Awards: Cross of the Legion of Honor

Charles Messier came to be known across the scientific community of Europe as “The Ferret of Comets.” That is because as a French astronomer, he discovered at least 20 comets, a remarkable feat considering that most famous astronomers of the day were lucky to find just one.

Messier was eager to discover as many comets as he could, partially because they were of scientific interest, but he also hoped they would provide him with fame and notoriety. Comets are generally named after their discoverers, as in the most famous case, Halley’s Comet, named for English astronomer Edmund Halley.

Messier’s Childhood

Charles Messier was born in Badonviller, France, in 1730, one of 12 children of Nicolas Messier and Françoise B. Grandblaise. By the time he was 11, his father had died and six of his siblings would not survive to adulthood. Charles Messier’s youth was a “life of poverty,” said writer and astronomer David Levy in his book, Cosmic Discoveries: The Wonders of Astronomy

Messier’s First Comet Sighting

With only a basic education in reading, writing, and arithmetic, the young Charles Messier was a youth without parents and without prospects. But 1744 was the year of the appearance of a spectacular comet of six tails, easily visible to the naked eye across the Northern Hemisphere. At the time, Messier was only 14 years old and the comet filled him with a sense of wonder.

Thus, as a penniless youth, Charles made his way on foot to Paris where he presented himself to a Parisian astronomer by the name of Delambres. He was hired as a lowly assistant to keep observatory records. Because of his excellent spelling skills and his “neat handwriting,” he was able to get his foot in the door.

The job with Delambres led to another position with another astronomer. He learned the science of observational astronomy “on the job,” and his long career as an astronomer had begun.

Messier’s Catalogue

Messier’s subsequent obsession with discovering new comets led him to compile a list of astronomical objects which remains one of the most significant documents in the field today. The 110 objects listed in the “Messier Catalog” have been a useful tool and an icon of astronomy for almost three centuries.

The Messier Objects are what appear to be fuzzy splotches of light in the deep night sky as seen through the most powerful telescopes of the day. These objects are actually star clusters, distant galaxies (such as the Andromeda Galaxy), and nebulae, or clouds of interstellar gas.

What motivated Messier to make a catalog of these objects is the fact that they could easily be mistaken for comets that were still a far distance from earth. Messier was tired of getting the “false alarm” of believing he had spotted a new comet whenever his telescope swept across the night sky and spotted a distant galaxy, cluster, or nebula.

Messier’s Lasting Influence

Creating a catalog of where these objects were located saved astronomers a great deal of time. Over the years, amateur astronomers have considered it a point of honor to spot as many or all of the Messier Objects with their backyard telescopes. In fact, many astronomy enthusiasts still do this today.

Messier was perhaps not a superior theoretician or mathematician, but his observational work earned him enormous respect and a place in astronomical history. A crater on the moon and an asteroid are named in honor of him.

In his lifetime, Charles Messier was elected to three of most prestigious scientific organizations in Europe: The British Royal Society, the Royal Swedish Academy of Sciences, and the French Academy of Sciences. He died at the age of 86 in 1817.

Christiaan Huygens


Born: Apr 14, 1629 in the Hague, Dutch Republic
Died: Jul 8, 1695 (at age 65) in the Hague, Dutch Republic
Nationality: Dutch
Famous For: Titan, explaining the rings of Saturn, centrifugal force, Huygens-Fresnel principle, wave theory, and many others

Christiaan Huygens was a natural philosopher and mathematician from the Netherlands. He was notably known as a physicist, astronomer, and horologist. Christiaan was a dominant natural philosopher in his time and his work was composed of telescopic studies on the rings of Saturn, the creation of the pendulum clock, investigations of timekeeping and the discovery of Saturn’s moon, Titan.

Huygens’ Early Life

Christiaan was born in 1629 as the second of five children. His father taught him at home until when he was 16 years old and he was later sent to study mathematics and law at the University of Leiden. He mostly wrote his name as Hugens.

Career Life

At an early age, Christiaan started working in advanced math by trying to disprove theories that had been established by ancient Greeks in geometry. He was interested in telescopes and astronomy and spent a lot of time designing methods to improve mechanical and optic performance of the telescopes.

His achievement in astronomy was reported in his book entitled Systema Saturnium, which was published in 1659. In this book, he noted the discovery of the rings around planet Saturn and his observations about the planets, the moon, and Orion Nebula.

Christiaan’s keen interest in the field of astronomy led him to measure time and other matters that relate to mechanical physics. He was involved in the 17th controversy with Vibiani as to the real creator of the pendulum clock, which he had presented as an accomplishment of the Dutch Science in his book, Horologium Oscillatorium. This may have been considered Christiaan’s finest efforts since he also suggested vital principles of classical physics like centrifugal force and gravity in a vacuum.

Huygens’ Reputation Builds

In the mid 17th century, Christiaan wrote a small piece on the calculus of probabilities pegged on theories of Fermat and Pascal. He spent a few years in England doing this. His reputation as a scientist and a scholar became known worldwide and he was given a pension by King Louis XIV to move to Paris. While in France, his works on timepieces continued to the point of an inclusion of balance springs in order to increase accuracy and reliability.

The very first watch made using this principle was completed in 1675 and was presented to Christiaan’s sponsor, King Louis. In 1681, Christiaan went back to Holland and began constructing optical lenses containing very big focal lengths. These were later given to the Royal Society in London where they remain to date. He perfected his lens grinding skills and eventually created the achromatic eyepiece which bears his name and is used worldwide today.

He published a book entitled Traite de la Lumiere in 1690 in which he suggested a theory explaining the wave behavior of light. He claimed that light waves travel on an invisible ether that fills the void throughout space and air.

Huygens’ Death

Christiaan Huygens died in the Hague in 1695 after suffering from depressive illness. He was laid to rest in the Grote Kerk.

Clyde Tombaugh


Born: Feb 4, 1906 in Streator, Illinois
Died: Jan 17, 1997 (at age 90) in Las Cruces, New Mexico, U.S.
Nationality: American
Famous For: Discovery of Pluto

Pluto used to be the ninth plant in the solar system until it was demoted to a dwarf planet several years ago. Its demotion happened less than a decade after the death of its discoverer, Clyde Tombaugh, who died in 1997.

Tombaugh discovered the small, rocky, frigid planet while he was studying photographic plates with a blink microscope at the Lowell Observatory in 1930. It was just where Percival Lowell had predicted it would be some 15 years earlier.

Tombaugh’s Early Life

Born in Streator, Illinois, Tombaugh and his family moved to Burdette, Kansas, when he was still young. Unable to go to college because he was needed on his family’s farm, Tombaugh was largely self-taught. When he was still young, he began to build his own telescopes and was hired to work at the Lowell Observatory in Flagstaff, Arizona, which was and still is run by members of the Lowell family. He stayed at the Observatory from 1929 to 1945. During his time there, Tombaugh attended the University of Kansas. He worked at the observatory during his summer breaks.

Tombaugh’s Discoveries

At Lowell Observatory, Tombaugh was given the job of actively searching for Pluto. He used a 13-inch astrograph, which is a telescope that takes pictures of the stars. The blink microscope helped him tell the different images apart and compare them.

A moving object would change position while the stars remained motionless. Though he eventually discovered Pluto this way on February 18, 1930, Tombaugh found many asteroids in the meantime. The first one he found he named after his daughter, Annette. He was fond of naming asteroids after members of his family.

Besides the hundreds of asteroids Tombaugh discovered, he also discovered variable stars, which change in brightness over time. He also found clusters of stars and galaxies and at least one supercluster of galaxies. He also claimed to have seen UFOs in New Mexico. Though he prided himself on his scientific objectivity, he could not rule out the possibility that these UFOs had an extraterrestrial origin. He became part of a project that searched for near-earth satellites, but claimed that the search, in the end, was unsuccessful.

Naming Pluto

Though he discovered it, Tombaugh actually did not name the planet Pluto. Before it was discovered it was given the placeholder name of Planet X. The name Pluto was suggested by an 11-year-old English girl named Venetia Burney. The name fit because Pluto is the name of the Roman god who rules the underworld. The name was also a tribute to Percival Lowell’s initials. The name became official on the May 1, 1930. Tombaugh’s wife Patricia claimed he would have been disappointed by Pluto’s demotion, but would have accepted it eventually.

Death and Launch into Space

Tombaugh died in Las Cruces, New Mexico, on January 17, 1997. He was 90 years old. But this is not the end of his story. He was cremated and a container holding some of his ashes is in the New Horizons spacecraft, which was launched on January 19, 2006, with the goal of surveying Pluto and five of its moons. The spacecraft is supposed to reach the Pluto system around July 14, 2015.

Edmund Halley


Born: Nov 8, 1656 in Haggerston, Shoreditch, London, England
Died: Jan 14, 1742 (at age 85) in Greenwich, London, England
Nationality: English, British
Famous For: Halley’s Comet

Edmund Halley was an English astronomer and mathematician who was brought up in a wealthy family. His father was a soap maker from the Derbyshire family at a time when the demand for soap was increasing in Europe. Although the father lost a lot in the 1666 Great Fire of London, he could still afford his son’s education and also pay a private tutor. After joining St. Paul’s School, Halley’s true astronomical talent started showing.

Halley’s Early Years

At the age of 17, Halley joined Queens College in Oxford with astronomical expertise practiced by the assortment of instruments his father had bought him. He reinforced his talent by working with John Flamsteed, who was the Astronomer Royal in 1675. His work encompassed observations at Greenwich and Oxford.

During his Oxford studies in June 1676, Halley observed an occultation of Mars and since then proposed to move to the Southern Hemisphere to carry the same observations. This idea was modestly financed by his father as well as King Charles II.

The King personally issued a letter to the East India Company to take Halley and an assistant to St. Helena. Also the president of the Royal Society, Brouncker, and the founder of Royal Observatory, Jonas Moore, supported Halley’s endeavors. This marked the start of his road to success.

Halley’s Astronomical Works

At the Island of St. Helena, Halley recorded celestial latitudes and longitudes. When he returned back home in 1678, he had observed up to 341 stars including a passage of Mercury along the sun’s disk. His published catalogue was the first one to contain southern stars with telescopically locations. As such, he was promoted to be a fellow of the Royal Society. In his service, he was sent to Danzig to resolve a dispute between Havelius and Hooke concerning observation accuracy. Hooke sued Havelius for making inference without using the telescope. Halley’s verdict was that the observations were accurate.

Nevertheless, Halley’s chief motive was to explain planetary motion using celestial mechanics extended from Isaac Newton’s studies. Together with Robert Hooke, they made impressive progress, but with no solid observed orbits that could support their findings.

Halley’s Work with Comets

In 1704, Edmund Halley was appointed the professor of geometry at Oxford, but he still persistently studied astronomy. In 1705, his book, A Synopsis of the Astronomy of Comets, was published and it described an observation of parabolic orbits of 24 comets that were observed between the years 1337 and 1698.

Halley’s careful observations with many separate years reveled that comets travelled in similar orbits. Particularly, he saw that the comets of the years 1531, 1607, and 1682 were similar and thus same. In fact, he further predicted that the comet would return in the year 1758 and when it did, it was named Halley’s Comet to honor his discovery.

In a nutshell, Halley’s transition from theoretical to applied astronomy has made him iconic and a symbol of inspiration to young astronomers. In his time, he also devised methods of accurately measuring the distance of the earth from sun. In 1720, he took over as the Astronomer Royal of Greenwich until his death in 1742.

Edwin Hubble


Born: Nov 20, 1889 in Marshfield, Missouri, U.S.
Died: Sep 28, 1953 (at age 63) in San Marino, California
Nationality: American
Famous For: Hubble sequence
Awards: Legion of Merit 1946, Gold Medal of the Royal Astronomical Society 1940, Franklin Medal 1939, Bruce Medal 1938

Edwin Hubble was an American astronomer who played a vital role in the establishment of extragalactic astronomy. He is regarded as one of the valuable observational cosmologists of the 20th century. He is specifically known for illustrating that recessional velocity in a galaxy increases with the distance from the earth, which implies that the universe is constantly expanding.

Edwin Hubble’s Early Life

Edwin Hubble was born in 1889. During his early years, he was noted more for his prowess in athletics than in his intellectual capabilities. He was a gifted athlete who played football, basketball, baseball and track. In fact, he ran track in both college and high school. He went to school at the University of Chicago and concentrated mainly on math, philosophy, and astronomy. These earned him a bachelor’s degree in science in 1910.

He was married to one wife, Grace Hubble.

Hubble’s Career

Hubble’s father wanted him to study law. As a result, Edwin studied law at the University of Chicago and then later at Oxford. Since he did not have a passion for law, he began teaching physics, math, and Spanish at the New Albany High School after his father died. At the age of 25, he gave up his teaching career and became a professional astronomer.

Hubble’s Contribution to Astronomy

In 1923, Hubble trained a Hooker telescope on a patch of the sky by the name of Andromeda Nebula. He discovered that it had stars similar to the ones in the galaxy, only dimmer. From the discovery, Hubble deduced that Andromeda Nebula was not a star nearby but rather an entire galaxy, which has subsequently been named the Andromeda Galaxy.

Hubble went on with his discoveries and by the end of those ten years, he found galaxies to compare with each other. He made a system that classified galaxies into spirals, barred spirals, and elliptical. This system is now known as the Hubble tuning fork diagram and it is still used today, but in an evolved form.

Hubble’s major discovery was when he studied spectra of 46 galaxies. He studied the Doppler velocities of the galaxies that were similar to the Milky Way. He discovered that the farther apart the galaxies are, the faster they move apart from each other.

Hubble also wrote two books – The Observational Approach to Cosmology and The Realm of the Nebulae.

The Hubble Telescope

Hubble has a telescope named after him: the Hubble Space Telescope. It was launched in 1990 with a main goal of pinning down the Hubble constant. The telescope helped discover that the universe is not only expanding, but that the expansion is accelerating as well.

Hubble’s Death

After his long career at Mt. Wilson Observatory, Hubble died in 1953 following a heart attack in 1949 and a blood clot in his brain four years later. There was no funeral for him and his wife did not reveal his burial site.

Fritz Zwicky


Born: Feb 14, 1898 in Varna, Principality of Bulgaria
Died: Feb 8, 1974 (at age 75) in Pasadena, California, USA
Nationality: American, Swiss
Famous For: Dark Matter, Supernovae, Galaxies, Neutron stars
Awards: President’s Medal of Freedom (1949), Gold Medal of the Royal Astronomical Society (1972)

Fritz Zwicky was a Swiss astronomer who worked most of his life at the California Institute of Technology. He is known for his many important contributions in theoretical and observational astronomy.

Zwicky’s Early Life

Zwicky was born on February 14, 1898, in Bulgaria to Swiss parents. He was the oldest of three children. At an early age of six, he was sent to live with his grandparents in Glarus, Switzerland. While there, he studied commerce. But later, his interest shifted to math and physics. At Swiss Federal Institute of Technology, he received his advanced education in mathematics and experimental physics.

Zwicky’s Work and Career

Zwicky migrated to the United States in 1825. After receiving the International Fellowship from the Rockefeller Foundation, he worked at the California Institute of Technology with Robert Millikan. In this institute, he was responsible for the positioning of several cosmological theories that had a great impact on the general understanding of the universe. In 1924, he was appointed Professor of Astronomy and he also worked as a consultant for the Aerojet Engineering Corporation.

Major Contributions to Astronomy

Zwicky was fascinated with cosmic rays. With the help of his colleague, Walter Baade, he pioneered the use of the very first Schmidt telescope that was used in mountaintop observations in 1935. He personally carried the lens from Germany which had been polished by Bernard Schmidt, an optician.

In 1934, together with Baade, he came up with the term “supernova” and hypothesized that this was the transformation of the normal stars into the neutron stars and the origin of the cosmic rays. Zwicky later started hunting for supernovae and he was able to find a total of 120.

Other Contributions to Astronomy

In addition to coining the word “supernova,” Zwicky and Baade suggested the use of supernovae as standard candles that can be used to estimate distances in the deep space. In addition, Zwicky also hypothesized that the galaxy clusters could actually act as gravitational lenses, which was by the previously discovered Einstein effect. This effect was later confirmed in 1979 by Twin Quasar observation.

After discovering neutron stars, Zwicky considered nuclear goblins. According to him, goblins could move within a given star and then explode violently as they get to a less dense region towards the star’s surface. This served to explain the eruptive phenomena like flare stars. He also produced the artificial meteors and even considered the possibility of rearranging the universe.

Zwicky and Dark Matter

While studying Coma galaxy cluster in 1933, Zwicky was the first person to use the viral theorem to deduce the existence of the unseen matter. This was referred to as the ‘dark matter’. After calculating gravitational mass of galaxies within the cluster, he obtained a value that was 400 times greater that than expected luminosity. He concluded that most of matter must be dark.

Later Years and Death

In 1949, Fritz Zwicky was awarded the Presidential Medal of Freedom for his work on rocket propulsion during the Second World War. He was also awarded the Gold Medal of Royal Astronomical Society in 1972, which is the most prestigious award an astronomer can receive.

Zwicky died in California on February 8, 1974, at the age of 75. His body is buried in Switzerland.

Galileo Galilei


Born: Feb 15, 1564 in Pisa, Duchy of Florence, Italy
Died: Jan 8, 1642 (at age 77) in Arcetri, Grand Duchy of Tuscany, Italy
Nationality: Italian
Famous For: Kinematics, Dynamics, Telescopic observational astronomy, Heliocentrism

Galileo Galilei was born on February 15 1564, in Pisa, Italy. When he was 17 years old, his parents sent him to the University at Pisa to pursue medicine.

Galileo’s Pendulum Study

While he was in a service in the cathedral one day, he was distracted by a bronze lamp hanging from the ceiling. He noticed that the lamp was drawn aside so as to light the room better. When it was released, the lamp oscillated back and forward gradually with decreasing amplitude.

Galileo used the pulse of his heart to keep the time and was surprised to discover the lamp’s oscillation period was unaffected by the arc’s size of oscillation. He later proved through an experiment that the period taken by a swinging pendulum did not depend on the bob’s weight. He proved that the period is dependent only on the pendulum’s length.

The pendulum was what formed his interest in astronomy and science. When he later got the chance to attend a lecture in geometry, this further fueled his interest in astronomy. Galileo then changed from medicine and decided to study science, philosophy, and mathematics. These were subjects in which he believed he possessed a strong natural talent.

Galileo’s Career

In 1589, Galileo was appointed the mathematics professor at Pisa. In 1591, his father, Vincenzo Galilei, died and as the eldest son, Galileo had to take up the position of the bread winner. Since he was not well paid as the mathematics professor, he looked for a much better post.

In 1952, Galileo become the mathematics professor at the University of Padua. He was able to secure a job with a salary that was almost three times more than the one he received at Pisa. He held this position until 1610 and described this period as the happiest time of his life. He focused on a number of experiments, such as the speed of fall of various objects, the pendulum effect, and mechanics.

Contributions to Astronomy

In 1609, Galileo heard of the telescope invention in Holland. Having not seen the telescope, he made a superior version which he used to make many astronomical discoveries. He was able to discover that there were valleys and mountains on the moon’s surface. He could track sunspots, observe the planet Venus and its phases, and even see that Jupiter had four large moons. His discoveries made him popular and he was later appointed to the court mathematician of Florence.

Controversy with the Church

In 1614, Galileo was accused of heresy because he supported the infamous Copernican theory which stated that the sun was the central part of the solar system. This went against what the Catholic Church said, which was that the earth was the center of the universe. In 1616, the church went so far as to forbid him from teaching or pursuing such theories.

Galileo’s Punishment

In 1632, Galileo was condemned of heresy after he published his book Dialogue-Concerning-the-Two Chief World Systems. In his book, he used a dialogue between two men to argue facts that were in support and against the Copernican theory.

Galileo was called to present himself before the Inquisition at Rome where he was convicted and sentenced to a life of imprisonment. The sentence was later minimized to permanent house arrest in his home in Arcetri after being forced to publically withdraw his views and beliefs of the discredited Copernican theory.

Later Years and Death

By 1638, he was starting to lose his eyesight, but he still continued writing. He published a book called Discourses Concerning Two New Sciences which included his ideas on motion laws and principles of mechanics. Galileo died in his home in Arcetri on January 8, 1642.