science

1. ASTRONOMERS WHO HAS CONTRIBUTIONS ABOUT THE EARTH AND
BEYOND
Persian astronomer Abd al-Rahman al-Sufi (903-
986), known as Azophi to Westerners, made the first
known observation of a group of stars outside of the Milky
Way, the Andromeda galaxy.
In 16th century Poland, astronomer Nicolaus
Copernicus (1473-1543) proposed a model of the
solar system that involved the Earth revolving
around the sun. The model wasn't completely
correct, as astronomers of the time struggled with
the backwards path Mars sometimes took, but it
eventually changed the way many scientists viewed
the solar system.
Using detailed measurements of the path of planets
kept by Danish astronomer Tycho Brahe, Johannes
Kepler (1571-1630) determined that planets
traveled around the sun not in circles but in ellipses.
In so doing, he calculated three laws involving the
motions of planets that astronomers still use in calculations today.
Born in Italy, Galileo Galilei (1564-1642) is often
credited with the creation of the optical telescope, though
in truth he improved on existing models. The astronomer
(also mathematician, physicist and philosopher) turned
the new observational tool toward the heavens, where he
discovered the four primary moons of Jupiter (now known
as the Galilean moons), as well as the rings of Saturn.
Though a model of the Earth circling the sun was first
proposed by Copernicus, it took some time before it
became widely accepted. Galileo is most widely known for
defending the idea several years after Kepler had already

2. calculated the path of planets, and Galileo wound up under house arrest at the end of
his lifetime because of it.
Dutch scientist Christiaan Huygens (1629-1695) proposed the earliest theory about the
nature of light, a phenomena that puzzled scientists for hundreds of years. His
improvements on the telescope allowed him to make the first observations of Saturn's
rings and to discover its moon, Titan.
Building on the work of those who had gone before him, English astronomer Sir Isaac
Newton (1643-1727) is most famous for his work on forces, specifically gravity. He
calculated three laws describing the motion of forces between objects, known today as
Newton's laws.
In the early 20th century,
German physicist Albert
Einstein (1879-1955) became of of the
most famous scientists ever after
proposing a new way of looking at the
universe that went beyond current
understanding. Einstein suggested that
the laws of physics are the same
throughout the universe, that the speed
of light in a vacuum is constant, and
that space and time are linked in an
entity known as space-time, which is
distorted by gravity.
At the same time Einstein was expanding man's view of the universe, American
astronomer Edwin Hubble (1899-1953) calculated that a small blob in the sky existed
outside of the Milky Way. Prior to his observations, the discussion over the size of the
universe was divided as to whether or not only a single galaxy existed. Hubble went on
to determine that the universe itself was expanding, a calculation which later came to be
known as Hubble's law. Hubble's observations of the various galaxies allowed him to
create a standard system of classification still used today.
American astronomer Carl Sagan (1934-1996) may not have been great
scientists in comparison to some on this list, but he is one of the most famous
astronomers. Sagan not only made important scientific studies in the fields of planetary
science, he also managed to popularized astronomy more than any other individual. His
charismatic teaching and boundless energy impacted people around the world as he
broke down complicated subjects in a way that interested television viewers even as he
educated them.
Stephen Hawking (born
1942) has made many
significant insights into the field
of cosmology. He proposed
that, as the universe has a
beginning, it will likely also end.
He also suggested that it has
no boundary or border. Despite

3. being viewed as one of the most brilliant minds since Einstein, many of Hawking's
books and lectures are steered toward the general public as he seeks to educate
people about the universe they live in.
Italian astronomer Giovanni Cassini (1625-1712)
measured how long it took the planets Jupiter and Mars
to rotate, as well as discovering four moons of Saturn
and the gap in the planet's rings. When NASA launched
a satellite to orbit Saturn and its moons in 1997, it was
fittingly dubbed Cassini.
Edmond Halley (1656-1742) was the British
scientist who reviewed historical comet sightings
and proposed that the comet which appeared in
1456, 1531, 1607, and 1682 were all the same,
and would return in 1758. Although he died before
its return, he was proven correct, and the comet
was named in his honour.
French astronomer Charles Messier(1730-1817)
composed a database of objects known at the time as
"nebulae," which included 103 objects at its final
publication, though additional objects were added based
on his personal notes. Many of these objects are often
listed with their catalogue name, such as the Andromeda
Galaxy, known as M31. Messier also discovered 13
comets over the course of his lifetime.
British astronomer William Herschel (1738-
1822) catalogued over 2,500 deep sky objects. He
also discovered Uranus and its two brightest
moons, two of Saturn's moons, and the Martian
ice caps. William trained his sister, Caroline
Herschel (1750-1848), in astronomy, and she
became the first woman to discover a comet,
identifying several over the course of her lifetime.

4. Henrietta Swann Leavitt (1868-1921) was one of
several women working as a human "computer" at
Harvard College, identifying images of variable stars on
photographic plates. She discovered that the brightness
of a special flashing star known as a Cepheid variable was
related to how often it pulsed. This relationship allowed
astronomers to calculate the distances of stars and
galaxies, the size of the Milky Way, and the expansion of
the universe.
American astronomer Harlow Shapley (1885-
1972) calculated the size of the Milky Way galaxy and
general location of its center. He argued that the
objects known as "nebula" lay within the galaxy,
rather than outside of it, and in 1920 participated in
the "Great Debate". He also incorrectly disagreed with
Edwin Hubble's observations that the universe
boasted galaxies other than the Milky Way.
Frank Drake (born 1930) is one of the
pioneers in the search for extra-terrestrial
intelligence. He was one of the founders of the
Search for Extra-terrestrial Intelligence (SETI) and
the deviser of the Drake equation, a mathematical
equation used to estimate the number of extra-
terrestrial civilizations in the Milky Way galaxy able to
be detected.
American astronomer William K. Hartmann (born
1939) put forth the most widely accepted theory on
the formation of the moon in 1975. He proposed that, after a collision with a large body
scooped, debris from the Earth coalesced into the moon.
SOURCE: http://www.space.com/16095-famous-astronomers.html