Aristarchus of Samos Hipparchus Nicholas Copernicus Galileo Galilei Johannes Kepler Sir Isaac Newton Edmond Halley Sir James Jeans Tycho Brahe
Aristarchus of Samos (c. 300- 250BC):
A Greek astronomer and mathematician who live from 310 BC to 230BC, was said to have first proposed the heliocentric (the sun being at the centre of the solar system) theory of the universe. The only writing of his that remains, ‘The Sizes and Distances of the Sun and Moon' followed highly original procedures, however his calculation of the Moon’s distance was incorrect due to the lack of accurate instruments, but had a more correct value of the solar year. The writing does not mention his conclusion that the Earth moves around the sun and that the sun is stationary, but statements by Archimedes and Copernicus indicate that he held this theory. Another theory of his is that the Sun is larger than the Earth, that the Earth rotates upon its axis causing day and night and that the ecliptic axis of the Earth causes the change of the seasons.
Hipparchus (c. 190-120 BC):
Hipparchus lived from 190BC to 120BC and was the most important Greek astronomer of his time. Born in Nicaea, Bithynia (modern day Iznik, Turkey), Hipparchus was extremely accurate in his research, which is recorded in the Almagest the scientific treatise by the astronomer Ptolemy who was greatly influenced by Hipparchus. By comparing his studies with that of Earlier astronomers, Hipparchus discovered the precession of the equinoxes (elliptical orbit). His calculation of the tropical year (the length of the year determined by the seasons) was within 6.5 minutes of modern measurements. Hipparchus invented a method of locating geographical positions by using latitudes and longitudes and also catalogued, charted and calculated the brightness of up to 1000 stars. Hipparchus also compiled a table of trigonometric chords that became the bases for modern trigonometry.
Nicholas Copernicus (1473-1543):
Nicholas Copernicus was a Polish astronomer who set the foundation of modern astronomy based on his system, the Copernican system. The Copernican system was the first modern European theory of planetary motion that places the sun at the centre of the solar system with all of the planets revolving around it in perfect circles, as opposed to traditional Ptolemaic system which stated that all of the planets and the sun revolved around the Earth. This system was developed in the sixteenth century from the analysis of ancient astronomical record however this particular theory of Copernicus, was not received well in the church at all and so was suppressed after an ecclesiastical trial. However, there still remained many followers of the Copernicus system which gradually took over the original theory that the sun and other planets revolved around the Earth.
Galileo Galilei (1564-1642):
Italian astronomer, mathematician and physicist Galileo Galilei contributed greatly to astronomy. With his construction of astronomical telescope he enlarged the vision of human kind and enabled a new understanding of universe. The astronomical telescope was constructed after he heard a magnifying instrument being put together in Holland in 1609. With this new instrument Galileo discovered that the surface of the moon is not smooth but indeed an uneven, mountainous surface and that the Milky Way is made up of numerous separate stars. The four largest satellites of Jupiter were discovered in 1610, which were first satellites of the other planets (excluding the moon and the Earth) to be detected. Due to his adherence of the Copernicus system, he was forced to stand trial in the Vatican, publicly renounce his views and spent the rest of his life under house arrest.
Johannes Kepler (1571-1630):
Kepler’s laws were three mathematical statements created by the German astronomer Johannes Kepler. His laws explain the revolution of planets around the sun. The first law expresses that the orbit shape of the planets is eclipse and the distance from the sun of each planet differs from another as it shift through one orbit. The second law of Kelper states that as the planets distance themselves away from the sun their speed decreases. The third law conveys a relationship between the average distance of the planet from the sun and the time to finish one revolution around the sun. Kepler's first and second laws were published in 1609 in ‘Commentaries on the Motions of Mars? The third law appeared in 1619 in ‘Harmony of the Worlds?
Sir Isaac Newton (1642-1727):
Sir Isaac Newton could be considered as one of the greatest scientists that ever lived. He formulated the theory of gravitation (as commonly depicted after an apple fell on his head), and the discovery that white light consists of multiple colour spectrums. These breakthroughs are considered as significant contributions to astronomy and science as a whole. His discoveries in terrestrial and celestial mechanics in his ‘Philosophiae naturalis principia mathematica' published in 168 are one of the fundamental highlights in science. The first part of principia is dedicated to dynamics and his famous laws of motions.
Edmond Halley (1656-1752):
Edmond Halley was an English astronomer and mathematician born in London and educated in the University of Oxford. He was fascinated by the theories of Isaac Newton and encouraged him to write the famous ‘principia' and also published it at his own expense. Halley’s most important scientific work was the ‘Astromiae Cometica Synopsis' which was published in 1705. This book used Newton’s Law of motion to mathematically demonstrate that comets move in elliptic orbits around the sun. He is famous for the prediction of the return of a comet in 1758, now known as Halley’s Comet which validated his theory that comets are a part of the solar system.
Sir James Hopwood Jeans (1877-1946):
James Jean was an English mathematician, physicist and astronomer who lived from 1887 to 1946, a professor of applied mathematics at Princeton University (1905-1909), later lecturing at Cambridge and Oxford being knitted in 1928. Devoting himself to mathematical physics he was involved in the dynamical theory of astrophysics and cosmogony, later solving the problem of the behaviour of certain nebulae, the origins of binary stars and the evolution of gaseous stars (Problems of Cosmogony and Stellar Dynamics). With Harold A. Jeffreys he developed a hypothesis of the origin of the Earth. In 1929 Jeans abandoned research and became an outstanding populariser of science and the philosophy of science, writing many works including The universe around us (1929), The Mysterious Universe (1930) and The Growth of Physical Science (1947).
Tycho Brahe (1546-1601):
Danish astronomer, Tycho Brahe, was an outstanding astronomer in the late sixteenth century. His improvement of instruments and his nearly precise location of planets and stars made the approach easier for future discoveries in that Kepler’s laws were developed from Tycho Brahe’s observation of the planets. The various accomplishments of Tycho Brahe include the first observation of supernova in the constellation Cassiopeia in 1572 and the discoveries of the inclination of the lunar orbits. Also in 1572 he was given funds by the Danish King Frederick II to build a castle, Uranienborg (‘fortress of the heavens), and an observatory, Stjarneborg, on the island of Hven. Frederick’s successor, Christian IV withdrew Brahe’s benefits in 1688. Even so, in 1597 Brahe was invited by to Bohemia by the Holy Roman Emperor; Rudolf II, who have him a pension of 3000 ducats as well as an estate near Prague where a new observatory could be built, however Brahe died in 1601 before his observatory could be completed. Brahe never fully accepted the Copernican system of the universe although he combined it with the old Ptolomeic System as a compromise. In Brahe’s system, the five planets revolved around the sun, which, with the planets, circled the Earth each year.