famous cosmologists and astronomers

Galileo Galilei (1564-1642)

  • Was a great Italian mathematician and astronomer .  The Pendulum Clock  was invented by him . Galileo made his own telescope to look at the Moon, Venus and Jupiter. He described his observations of space in a book " The Starry Messenger , published in 1610.  Through his telescope Galileo discovered that Jupiter has four moons. He also saw that Venus has phases. Galileo supported the Copernican theory . Galileo's experiments with balls rolling down slops laid down the basis for our understanding of how gravity makes things accelerate (Speed Up)   

Ptolemy (CE 90 to CE 1680)

  • The most famous of the ancient astronomers was Ptolemy . He lived and worked in the city of Alexandria .Ptolemy followed Hipparchus in believing that the earth was at the centre of the Universe ,and this Ptolemaic viewpoint lasted until the Copernican Revolution overthrew it .He also believed that the Sun, Stars and Planets were embedded in series of concentric transparent crystal spheres that surrounded the Earth. He extended Hipparchus' star catalog to include a total of 1022 stars and defined 48 of the constellations .

Nicolaus Copernicus (1473-1543)

  • Was the astronomer who first suggested that the Sun the centre, and that the Earth went around the Sun ,  Copernicus had an extensive education at the best universities in Poland and Italy. He studied astronomy , astrology , medicine and law. He described his ideas is his book , De revolutionibus orbium coelestium(On the Revolutions of the Heavenly Spheres ) . His book was banned by Roman Catholic Church for almost 140 years.  His theory proof certified when Galileo saw through a telescope, moons revolving around Jupiter. His Idea known as Copernican Revolution.

Edwin Hubble (1889-1953)

  • Was an American who trained in law at the Universities of Chicago and Oxford, and was also a great boxer before he turned to astronomy . In 1920s,Hubble showed that the fuzzy patches of light once thought to be nebulae were in fact other galaxies far beyond the Milky Way . In 1929 he measured the distance of 20 galaxies and showed that they were all moving away from the Earth.  In 1930s , Hubble showed that the Universe is isotropic ( the same in all directions ) , The Hubble space telescope is able to see space objects , such as planetary nebulae , in great detail . The ratio of a galaxy 's distance to the speed it is moving away from Earth is now known as Hubble's Law. 


Edmond Halley (1656-1742)

  • Was an English astronomer , geophysicist, mathematician , meteorologist and physicist . He worked at the University of Oxford's Royal Observatory , in Greenwich. In 1675 hally became an assistant to John Flamsteed , the Astronomer Royal at the Greenwich Observatory. In 1705 , he published the Synopsis Astronomia Cometica . In this  , he stated his belief that comet sightings of 1456 ,1531,1607, and 1682 related to the same comet and he predicted it would return in 1758.  He did this by applying historical astronomy methods. But when it returned , the comet became generally known as Halley's Comet.

Johannes Kepler (1571-1630)

  • German astronomer discovered the basic rules about the way in which the planets move.  He got his ideas from studying the movement of Mars. Kepler discovered that the shape of the planets' orbits is elliptical (oval). This is Kepler's first law. His second law is that the speed of a planet through space varies according to its distance from the Sun .  Kepler lost his eyesight and use his hands through smallpox at the age of 3 . He became an assistant to the great Danish astronomer Tycho Brahe , and took over his work when Brahe died.  Kepler's third law states that the square of a planet's period is proportional to the cube of its average distance from the Sun. 

Giovanni Cassini (1625-1712)

  • Born on June 8, 1625 in Perinaldo, Republic of Genova, this Italian man was the first to come up with an estimation of the Solar System's Dimension. He was also the one to observe the four moons of Saturn and together with Robert Hooke, the discovery of the Great Red Spot on the planet, Jupiter. His observation of Sidera Lodoicea or the four moons of Saturn, including lapetus has exposed and make him known in Astronomy.In recognition to this observation, it is known as Cassini Regio. The Cassini Division was also named after him as he was able to discover the four rings of Saturn. In 1690, he also was the one to observe the differential rotation within Jupiter’s atmosphere. He made measurements of longitude by the use of an alternative clock, eclipses of Jupiter's satellites. 

Christiaan Huygens (1629–1695)

  • Christiaan Huygens played an essential role in some of the most incredible discoveries in math, astronomy and physics. His role in scientific history touches everything from what we now understand about the theory of light waves in three dimensions, to the concept of centrifugal force, to even basic things that are now learned in elementary school classes, such as astronomy behind the rings of Saturn. Huygens's creative and scientific processes were intertwined from an early age through simple actions like throwing a rock into the water and watching the emanating pattern of waves and playing with windmills. These actions ultimately led to a life of experimentation and observation across multiple scientific disciplines. 

Sir Isaac Newton (1643–1727)

  • Isaac Newton was an English astronomer discovered the force of gravity and the three basic laws of motion . His ideas were inspired by seeing an apple fall from a tree in the garden of his home . Newton also discovered that sunlight can be split into a spectrum made of all the colors of the rainbow. Newton was  made Lucasian professor of mathematics at Cambridge University in 1669, where he studied how and why things in our Universe move .  Newton's three laws of motion showed that every movement in the Universe can be calculated mechanically.  

Charles Messier (1730–1817)

  • The French astronomer Charles Messier was born in Lorraine on June 26, 1730. As a boy he developed a very keen interest in astronomy after seeing the brilliant six-tailed comet of 1744. Even though Messier came from a poor family and had limited schooling he was hired at the age of 21 as a draftsman by Joseph-Nicholas de l'Isle, an astronomer to the French Navy. Edmund Halley had predicted that the comet of 1682 would return in late 1758 or early 1759. Using charts that de l'Isle had incorrectly prepared, Messier began searching for the comet with a small reflector. On January 21, 1759 he located the comet but de l'Isle initially refused to let Messier announce his discovery. (As fate would have it the comet was first sighted on Christmas Night of 1758 by a German farmer and amateur astronomer named Palitzch.) Undaunted by the embarrassment of the late announcement, Messier from that time onwards devoted himself to searching for comets. In the coming years he held a near monopoly on comet discoveries claiming to have found 21 by 1798.  

William Herschel (1739–1822)

  • Was a German musician who became the King's astronomer in England and built his own powerful telescopes.  With the help of his sister, Caroline , he discovered Uranus in 1781 . He later identified two of the moons of Uranus and two of Saturn. he build huge extremely powerful telescope at his home in Bath , England .  His sister , Caroline (1750-1848) ,was a great astronomer who discovered eight comets and produced catalogs of stars and nebulae.  John, Hershel's son , catalogued the stars of the Southern Hemisphere.  Herschel wanted to name the planet George, after King GeorgeIII, but Uranus was eventually chosen , after the ancient Greek god of the sky. 

Henrietta Swann Leavitt (1868–1921)

  • Henrietta Swan Leavitt was an American astronomer who discovered the relation between the luminosity and the period of Cepheid variable stars. A graduate of Radcliffe College, Leavitt started working at the Harvard College Observatory as a "computer operator " in 1893, examining photographic plates in order to measure and catalog the brightness of stars. Though she received little recognition in her lifetime, it was her discovery that first allowed astronomers to measure the distance between the Earth and faraway galaxies. She explained her discovery: "A straight line can readily be drawn among each of the two series of points corresponding to maxima and minima, thus showing that there is a simple relation between the brightness of the variables and their periods." After Leavitt's death, Edwin Hubble used the luminosity–period relation for Cepheids together with spectral shifts first measured by fellow astronomer Vesto Slipher at Lowell Observatory to determine that the universe is expanding.  

Harlow Shapley (1885–1972)

Carl Sagan (1934–1996)

Frank Drake (born 1930)

William K. Hartmann (born 1939

Genius of Our Time

Albert Einstein

Albert Einstein (1879-1955)

  • The great scientist Einstein is known for uncovering the two theories of relativity . Einstein 's theory of general relativity was proved right in 1919 , when light rays from a distant star just grazing the Sun were measured during an eclipse and shown to bent. Einstein overturned  the idea that time is the same everywhere, He was the first to show that time is relative . 


Stephen Hawking (1942-2018 )

  • Stephen William Hawking CH CBE FRS FRSA is an English theoretical physicist , cosmologist , author and Director of Research at the centre for Theoretical Cosmology within the University of Cambridge . Hawking suffers from a rare , early onset , slow-progressing form of amyotrophic lateral sclerosis (ALS)  This has gradually paralysed him over the decades .  He also lost the use of his vocal chords . he currently communicates by using a single cheek muscle attached to a speech -generating device . Hawking collaborated with Roger Penrose on gravitational singularity theorems in the framework of general relativity. He made the theoretical prediction that black holes emit radiation . This is called Hawking radiation .  Hawking was the first to set forth a cosmology explained by a combination of the general theory of relativity and quantum mechanics. 

Neil DeGrasse Tyson (1958 -Live )

  • An American astrophysicist , cosmologist , author and science communicator . He was born in Manhattan and raised in Bronx. He obsessively studied astronomy in his teens . He gained some fame in the astronomy community because of his lectures on the subject at the age of 15 . Astronomer Carl Sagan tried to recruit Tyson to Cornell for undergraduate studies while he was a faculty member there.  From 2006 to 2011 , Tyson hosted the educational science television show "NOVA Science Now " on PBS. Tyson's research focuses on observations in cosmology , stellar evolution, galactic astronomy , bulges and stellar formation .  He is published author and also very popular on social media . His tweets often focus on urban myths and religious mythology in the context of science .  In 2004 . he served on the Presidents's Commission on the implementation of United States Space Exploration Policy . This is better known as the " MOON MARS, and BEYOND " commission.