Ray Davis/John Bahcall:

In 1964 Bahcall and Ray Davis Jr of Brookhaven published back-to-back papers in Physical Review Letters that essentially defined what became known as the solar neutrino problem. In the decades that followed Davis consistently measured less than half the flux of solar neutrinos that had been predicted by Bahcall. Either Bahcall's theory or Davis' experiment was wrong, or possibly both, or else neutrinos behaved in unexpected ways.

It turned out that both Bahcall and Davis were right - the electron neutrinos produced by the Sun were oscillating into muon neutrinos that did not show up in Davis' detector. In 2002 Davis and Masatoshi Koshiba of the University of Tokyo shared the Nobel Prize for their work on solar neutrinos. It was widely expected that Bahcall would share a subsequent prize for the discovery of neutrino oscillations.

Sources:http://www.worldbookonline.com/advanced/search?st1=Ray+Davis&x=41&y=13&searchprop=atk

S. Chandrasekhar: (1910-1995)

American astrophysicist, shared the 1983 Nobel Prize in physics with William A. Fowler for research on the evolution and death of stars. Chandrasekhar is best known for his work on white dwarf stars—the compact final state in the evolution of certain stars.

Chandrasekhar discovered that white dwarfs with a mass 1.4 times greater than the mass of our sun collapse as a result of their own gravitation. Eventually, they become neutron stars—stars with the density of an atomic nucleus—or collapse even further to become black holes. A black hole is so dense that not even light can escape from its powerful gravitation. The maximum mass a white dwarf star can have before it begins to collapse is known as the Chandrasekhar mass.

Sources:http://www.worldbookonline.com/advanced/article?id=ar105960&st=chandrasekhar

Arno Penzias/Robert Wilson: (1933-...)Penzias
German-born American astrophysicist, discovered and studied cosmic microwave background radiation. In 1978, he won the Nobel Prize for physics, sharing it with his American colleague Robert Wilson
(1936-...)Wilson
American radio astronomer. He shared half of the 1978 Nobel Prize for physics with fellow American Arno Penzias for their discovery and study of cosmic microwave background radiation.
Sources: http://www.worldbookonline.com/advanced/article?id=ar725808&st=robert+wilson

Annie Cannon:(1863-1941)
leading American female astronomer of her generation. In 1896, she joined the staff of the Harvard Observatory. Working with other astronomers there, Cannon developed a system of classifying stars by the spectra of their light and applied the system to over 350,000 stars. She discovered 300 variable stars, five novae (types of exploding stars), and a binary star. In 1925, Cannon became the first woman awarded an honorary doctorate of science by Oxford University.
Sources:http://www.worldbookonline.com/advanced/article?id=ar091720&st=annie+cannon

Clyde Tombaugh:(1906-1997)

American astronomer. He discovered Pluto, a dwarf planet that orbits far from the sun, in 1930 while he was examining some photographic plates with a blink microscope at the Lowell Observatory. Percival Lowell had predicted the general location of Pluto 15 years earlier. Tombaugh became engaged in ballistics research at White Sands (New Mexico) Missile Range in 1946. He was born in Streator, Illinois.
Sources: http://www.worldbookonline.com/advanced/article?id=ar723410&st=clyde+tombaugh

Johannes Kepler: (1571-1630)

German astronomer and mathematician, discovered three laws of planetary motion. The English scientist Isaac Newton later used these laws to arrive at his law of gravitation

Sources: http://www.worldbookonline.com/advanced/article?id=ar298000&st=johannes+kepler

Albert Einstein:(1879-1955)
Some of Einstein's most famous ideas make up parts of his special theory of relativity and his general theory of relativity. For example, the special theory describes an entity known as space-time. This entity is a combination of the dimension of time and the three dimensions of space—length, width, and height. Thus, space-time is four-dimensional. In the general theory, matter and energy distort (change the shape of) space-time; the distortion is experienced as gravity.

Sources:http://nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-bio.html
http://www.worldbookonline.com/advanced/article?id=ar175340&st=albert+einstein

Edwin Hubble:(1889-1953)
Edwin Hubble (1889-1953) expanded our view of the universe. At the dawn of the 20th century, most astronomers thought that the Milky Way Galaxy was the universe, and it measured only a few thousand light-years across.

Sources: http://www.pbs.org/wnet/hawking/cosmostar/html/cstars_hubble.html

Isaac Newton:(1643 - 1727)
Newton made a huge impact on theoretical astronomy. He defined the laws of motion and universal gravitation which he used to predict precisely the motions of stars, and the planets around the sun. Using his discoveries in optics Newton constructed the first reflecting telescope.

Sources: http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Newton.html
http://www.lucidcafe.com/library/95dec/newton.html

Galileo Galilei:(1564 - 1642)
Italian scientist who formulated the basic law of falling bodies, which he verified by careful measurements. He constructed a telescope with which he studied lunar craters, and discovered four moons revolving around Jupiter and espoused the Copernican cause.
Without a doubt, Galileo made many important contributions to observational astronomy. Historians disagree, however, about Galileo's role as a founder of modern experimental science. In fact, some of them doubt the importance of experiment in Galileo’s scientific development. These historians maintain that Galileo's real originality lay in the way he approached scientific problems. First, Galileo reduced those problems to very simple terms on the basis of everyday experience and common-sense logic. Then he analyzed and resolved the problems according to simple mathematical descriptions. The success with which Galileo applied this technique to the analysis of physics, especially the physics of motion, opened the way for the development of modern mathematical physics.

Galileo also pioneered the presentation of scientific findings to the widest possible audience. He wrote in clear, witty Italian rather than Latin, the scholarly language of his time. The broad public appeal of his Dialogue most likely contributed to Galileo’s condemnation by the church.

Sources: http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Galileo.html
http://www.worldbookonline.com/advanced/article?id=ar215300&st=galileo+galilei

Tycho Brahe:(1571-1630)
With generous royal support, Tycho constructed there a domicile and observatory which he called Uraniborg, and developed a range of instruments of remarkable size and precision which he used, with the aide of numerous assistants and students, to observe comets, stars, and planets.

Sources: http://www.hps.cam.ac.uk/starry/tycho.html
http://www.hps.cam.ac.uk/starry/tycho.html

Copernicus: (1473 - 1543)

Copernicus is said to be the founder of modern astronomy.
He made his celestial observations from a turret situated on the protective wall around the cathedral, observations were made "bare eyeball," so to speak, as a hundred more years were to pass before the invention of the telescope. In 1530, Copernicus completed and gave to the world his great work De Revolutionibus, which asserted that the earth rotated on its axis once daily and traveled around the sun once yearly: a fantastic concept for the times. Up to the time of Copernicus the thinkers of the western world believed in the Ptolemiac theory that the universe was a closed space bounded by a spherical envelope beyond which there was nothing.

Sources: http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Copernicus.html
http://www.blupete.com/Literature/Biographies/Science/Copernicus.htm

Henrietta Leavitt: (1868-1921)

Humanity's understanding of the relative brightness and variability of stars was revolutionized by the work of Henrietta Swan Leavitt (1868-1921). Working at Harvard College Observatory, Leavitt precisely calibrated the photographic magnitudes of 47 stars to which all other stars could be compared. Leavitt discovered and cataloged over 1500 variable stars in the nearby Magellanic Clouds. From this catalog, Leavitt discovered that brighter Cepheid variable stars take longer to vary, a fact used today to calibrate the distance scale of our universe.

Sources: http://apod.nasa.gov/apod/ap981027.html
http://apod.nasa.gov/apod/ap981027.html

James Van Allen: (1914-2006)
Van Allen's career took an important turn in 1955 when he and several other American scientists developed proposals for the launch of a scientific satellite as part of the research program conducted during the International Geophysical Year (IGY) of 1957-1958. After the success of the Soviet Union with Sputnik 1, Van Allen's Explorer spacecraft was approved for launch on a Redstone rocket. It flew on 31 January 1958, and returned enormously important scientific data about the radiation belts circling the Earth.


Sources:http://history.nasa.gov/sputnik/vanallen.html
http://history.nasa.gov/sputnik/vanallen.html

Albert Michelson (Michelson-Morley experiment): 1852-1931

Michelson did not see how he had helped physics by shattering the belief of the mysterious "aether." Nevertheless, he calculated one of the most accurate values for the speed of light in 1923. His initial value was 299,798 km/s for the speed of light. His final results were completed in 1933 after his death and were 299,774 km/s which differed from the accepted value of 1970 by only 2 km/s. In 1907, for his work on determining the speed of light, Albert Michelson became the first American to win a Nobel Prize for Physics. Michelson's interferometer had different applications as well. For example, he used a modified version of his interferometer attached to a telescope for making the first successful measurement of a star’s diameter (Betelgeuse) in 1920.

Sources:http://www.aip.org/history/gap/Michelson/Michelson.html
http://www.usd.edu/phys/courses/phys300/gallery/clark/mich.html

Pope Gregory XIII: (1502-1585)

He is perhaps best known for creating the Gregorian calendar, which is the calendar still in use in the West today. According to the Julian calendar, the year is 365 days 6 hr, a bit long. By the 16th century all of this accumulated time had moved the vernal equinox to March 11 from March 21. So, in 1582 Gregory simply "deleted" 10 days from the new calendar, which now included "leap days" in order to make up for more accumulated time in the future. By 1585, it had replaced the older Julian calendar in most Catholic countries. Protestant countries adopted it only gradually and some Eastern Orthodox countries did not do so until the 20th century.
Sources: http://www.nndb.com/people/130/000094845/
http://atheism.about.com/library/glossary/western/bldef_gregoryxiii.htm

Stephen Hawking: (1942- present)
British theoretical physicist. He has made what are regarded as the most important discoveries about gravity since the German-born physicist Albert Einstein invented general relativity, the modern theory of gravity, in 1915. Hawking's work supports the theory that the universe began in a big bang. Hawking is probably best known for his theories about black holes—invisible bodies in space with such strong gravitational force that not even light can escape them (see Black hole). Hawking has used the field of physics called quantum mechanics to show that a black hole nevertheless gives off particles and radiation until it eventually explodes and disappears. He continues to work on combining quantum mechanics and gravity in a single theory that would explain the origin and structure of the universe (see Quantum mechanics). Hawking's books A Brief History of Time: From the Big Bang to Black Holes (1988) and The Universe in a Nutshell (2001) became best sellers.


Sources: http://www.worldbookonline.com/student/article?id=ar248880&st=stephen+hawking

Carl Sagan: (1934- 1996)

American astronomer, author, and educator. He gained fame as a leading popularizer of science. Sagan wrote several books, numerous magazine articles, and many scientific papers. He was the chief writer and narrator of "Cosmos," a popular public television series. The series dealt with a wide variety of scientific issues. Sagan's writings reflect his broad interests. In his works, he discussed the nature of the planets and their atmospheres, the origin and evolution of life on the earth, and the possibility of life on other planets.


Sources: http://www.imdb.com/name/nm0755981/
http://www.worldbookonline.com/student/article?id=ar481745&st=carl+sagan

Ptolemy: (87 -150 AD)

He was an astronomer, mathematician and geographer. He codified the Greek geocentric view of the universe, and rationalized the apparent motions of the planets as they were known in his time.
Ptolemy synthesized and extended Hipparchus's system of epicycles and eccentric circles to explain his geocentric theory of the solar system. Ptolemy's system involved at least 80 epicycles to explain the motions of the Sun, the Moon, and the five planets known in his time. He believed the planets and sun to orbit the Earth in the order Mercury, Venus, Sun, Mars, Jupiter, Saturn . This system became known as the Ptolemaic system. It predicts the positions of the planets accurately enough for naked-eye observations This is described in the book Mathematical Syntaxis (widely called the Almagest), a thirteen book mathematical treatment of the phenomena of astronomy. It contains a myriad of information ranging from earth conceptions to sun, moon, and star movement as well as eclipses and a breakdown on the length of months. The Almagest also included a star catalog containing 48 constellations, using the names we still use today.

Sources: http://obs.nineplanets.org/psc/theman.html

Hipparchus: (64 BC-24 AD)

Based on Babylonian observations, he improved the accuracy of the length of the lunar, solar and sidereal years. He estimated the solar year with an accuracy which is only 6 1/2 minutes different from the current value. For the lunar month he obtained a value of 29 days, 12 hours, 44 minutes and 2 ½ seconds, only less than 1 second from the current value!
The tropical (solar) year is the period of the Sun's apparent revolution from an equinox to the same equinox again (The time reference that we use in everyday life), and the sidereal year is the period of the Sun's apparent revolution from a fixed star to the same fixed star.
Hipparchus discovered the precession of the equinoxes and was influential in the development of trigonometry, redefined and formalized the projection as a method for solving complex astronomical problems without spherical trigonometry and probably proved its main characteristics.
Hipparchus produced until 129 BC a catalogue of 850 stars after observing 134 BC a new star in the sky. This catalogue was of high precision and used even by the astronomer Edmund Halley. Hipparchus compared his star positions with those of Timocharis and Aristillus. He could not find any stars that had appeared or disappeared in the last 150 years but all the stars seemed to have changed their places with reference to that point in the heavens where the ecliptic is 90° from the poles of the earth i.e. the equinox. He found that this could be explained by a motion of the equinox in the direction of the apparent diurnal motion of the stars. He found the precession of the equinoxes, which takes place at the rate of 52",1 every year due to a steady revolution of the earth's pole round the pole of the ecliptic once in 26000 years in the opposite direction to the planetary revolutions.

Sources:http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Hipparchus.html

http://www.mlahanas.de/Greeks/Hipparchus.htm

Aristotle: 384-322BC

His encyclopedic works covered many subjects, including ethics, logic, metaphysics, politics, rhetoric, poetry, biology, zoology, physics, and psychology. His thought greatly influenced philosophers of the Middle Ages (A.D. c. 450–c. 1500) and in some areas of knowledge his ideas are still considered important.

Sources: http://www.philosophypages.com/ph/aris.htm
http://www.enotes.com/history-fact-finder/philosophy/why-aristotle-considered-one-greatest-minds