'aristotlle 384 BC
Geocentric model by Aristotle
In aristotle's view, the one adopted by the Church, the Earth is at the center of the universe. All the planets are prefect spheres
orbiting along perfect circles. Stars are plastered in a celestial sphere. All the spheres are nested into one another.
There is no use to observe the heavens because we will never reach reality but just an distorted view of it. Planets move along crystal spheres. (they didn;t know about gravity so they were try to explain why they didn't fly out). Not that for the Greek spheres and circle were perfect shapes.
Ptolemy born 90AD in Egypt
Geocentric model reviewed by Ptolemy
The solar of system as explained by Aristotle
didn't fit the observed motion of planets as view from the Earth. Ptolemy introduces epicycles, orbits on top of orbits. Then more epicycles were added. It became very messy.
Ptolemy was a great mathematician and
his system was a computational trick to be able to predict the positions of the planets.
However, he thought that we human can't only reach an imperfect reflection of a perfect reality. Sciences was not to be based on observations and experiences. He kind of introduced Fourrier analysis showing that any periodic motion can be described by a serie of sines and cosines.
Nickolaus Copernicus (February 19,
1473 – May 24, 1543) The heliocentric model
or Giordano Bruno
The statue of Giordano Bruno at the very
same place he was burnt at stake (Campo de' Fiori in Rome).. He is he 1st martyr for science. click the image. to know more.
Heliocentric system introduced by Copernicus. Uranus,
Neptune and Pluto were not known yet. source, to learn more.
Galileo Galilei (15 February 1564 – 8 January 1642)
This is the "Galileo lamp" in the Duomo in Pisa. Galileo was 17 years old when he discovered the laws upon which a pendulum is built. The legend said he was using this swinging lamp in the church, using his pulse to find the period. This is not true as the lamp was hanged after the death of Galileo.
Galileo worked a lot with inclined planes. His experiments showed
the principle of inertia and the laws of falling body.
If you neglect friction, an incline plane dilutes gravity but you
still get an uniformly accelerated motion. Galileo showed that in free-fall, bodies fall at the same rate, regardless of their mass.
He shows that without friction the motion lasts for ever. (without
any force needed to keep the motion going). He showed that
the distance covered is proportional the the time squared.
He published his work while in house arrest.
He also used inclined planes to show that all body fall at the same rat
regardless of their mass. (if we neglect air resistancE)
Galileo in front of the inquisition.
He supported the heliocentric system of Copernicus but had to retract himself to save his life. He was considered as an heretic by the Catholic church of the time. This was the bad time to challenge the church as the counter reformation was going on/
Here some irony. In Italy, remains of saints are exhibited in churches. But this is not the
finger of a SAint, it is the middle finger of Galileo, maybe a message to those who condemned him to home arrest for the rest of his life. This finger can be seen in Florence.
History of Science Museum
In 2000 the pope jean Paul II appologied for the mistake
of the church.
The tower of Pisa and behind the Duomo. It is said that Galileo drops different objects from the top and find out that any body, regardless of its mass, falls at the same rate. This legend is probably not true either.
Galielo improved the refractive telescope built by a dutch
optician (Hans Lippershey in 1608) It was a toy and he made it an intrument to study the heavens. He saw the mountains on the Moon, the ring of Staturn (he called it handles or ears), the phases of VEnus, the moons of Jupiter. Newtons later invented the reflective telescope.
|DISCOVERIES of Galileo that upset the ROman Catholic Church|
phases of Venus can not be explained by Ptolemy system of epicycles. Only Copernicus 's view can explain the phases/
A student of Galileo suggested him to look at the phases of vEnus to decide which system was the best. (Copernicus or Ptolemy). SEE BELOW for
more images .
wash study of GAlielo 1609 (museum of Florence)
Moons of Jupiter. Io, Europa, Ganymede and Callisto
So Earth is not the only planet to have Moon. It is not in a privileged position after all. Plus if was thought that the Earth can not rotate around the sun because we would fly off. But the moons
of Jupiter stay around while Jupiter is moving. So Galileo reasoned that there must be something keeping us on earth and the moon around the planets while the planets orbit the Sun.
ring of Saturn. Galielo could to resolve the whole
ring sohe described the ring as handles. But he
was the first one to see it.So the planets were not
perfect spheres after all. (Church's view).
mountains and valleys on the Moon. The moon is
not a perfect sphere either.
sunspots on the Sun . He observed the spots
moving around so he reasoned that the Sun was
spinning about its axis. So the EArthwas probably
spinning too.Also the Sun is not perfect either.
see text above,
from the textbook used for my class.
Kepler (December 27, 1571 – November 15, 1630)
Kepler. Galileo, Shakespeare, Queen Elizabeth were all contemporaries of Kepler.
Kepler was protestant and had to leave his Catholics country (Germany) to Prague in 1600. It was the 30 years war in Europe. Protestants and Catholics were fighting. It was a very bloody period.
In Prague Kepler was hired by Tycho Brahe as a mathematician. He was in charge of processing all the data collected by Tycho. Tycho Brahe was
a very gifted observer but Kepler was a better mathmatician.
The 2 men could not stand each others . But they needed each other.
Tycho was a weird guy. One day he had a duel with a student over who was the
best mathematician. The student's sword cut Tycho's nose when he was 20.
Tycho had to wear a fake nose made of copper for the rest of his life.
the nose was found in his tomb in Prague. During meals Tycho had a dwarf
under the table and fed him like a pet.
The picture on the left shows tycho collecting data from the planets. He collected these data in a room without ceiling, in his castle in Denmark. He lived on an island given by the king of Denmark. The King has been impressed by the discovery of Tycho of a Supernova
(1562). When the king died Tycho had to leave Denmark for Praque. (he was not in favor anymore). He was the first astronomer able to collect very high quality data. Only using his naked eyes. Kepler wanted these data badly.
Kepler discovered 3 laws regarding the motion of planets. The second law is a consequence of the conservation of angular momentum we are studying now. In equal time, planets sweep the same area.
Kepler got the data of Tycho after his death. He figured out his 3 laws after years of work. He wrote a book called harmony of the world. It is a mystic about music and the motions on planets. Newtons found the 3 laws and used them for his work. Since the force of gravity was not know, Kepler thought the planets had to moved on geometric shape embedded in each other. He was very good in geometry and the ratio between the the shapes were matching the ratio between the planets distance from the Sun. This paper was an addition to his first publication. Know more.
There is a statue of Sir Isaac Newton in the chapel
of Trinity College, Cambridge.
When translated from the Latin, the inscription at its base reads
click on the image. Piece of an apple tree
from Newton's garden. Can be seen
source : NASA website. click image
A replica of Newton's 6 inch reflecting telescope
of 1672 for the Royal Society.
CLICK IMAGE : Halley's comet/
Halley was a good friend of Newton. He convinced Newton to publish his work about the universal gravitational law.
Newton found why the planets stay in orbit around the EArth (Inertia principle + force of gravity) but never published his work.
The comet is named after Edmond Halley. He observed the comet in 1682 and realized it was the same object observed by Kepler in Prague and in 1531 by Apianus. The period is 76 years.
Robert Hooke disagree with Newton about the nature of light.
Newton saw light as particles called corpuscles. Newton could not stand criticism and hated Hooke. It seems Hook was short and hunchback and Newton wrote these famous words to Hooke:
If I have seen further it is by standing on the shoulders of giants
Newton developed his infinitesimal calculus between 1664 and 1666 when he was temporarily con-fined to his estate in Woolsthorpe, quarantined from an outbreak of Bubonic plague in England. However, Newton did not publish his mathematics. Years later Leibniz published his own infinitesimal methods in a recently established scholarly journal circulated around Europe, the Acta Eruditorum. Leibniz's methods appeared in the Acta in two different articles, one in 1682 and the other in 1684. Thus, while Newton's techniques were developed first, Leibniz was the first to publish. Newton had this fight with Leibniz about who came with Calculus first. Newton didn't like
competition but he didn't publish his work.
The poet Alexander Pope, who lived at the same time as Newton, wrote
Newton didn't have a happy childhood. His father , an illiterate farmer, has died 3 months before his birth. His mother remarried when he was 3 and left Newton
Nature and Nature's laws lay hid in night;
God said, 'Let Newton be!' and all was light.
But a English humorist added: It did not last; the devil howling "Ho!The 3 laws of Newton based on calculus could explain and predict any nature's phenomena given the initial conditions.
Let Einstein be!" restored the status quo.
In formulating his physical theories, Newton had developed a field of mathematics known as calculus. However, the language of calculus was largely left out of the Principia. Instead, Newton recast the majority of his proofs as geometric arguments.
There was a fight between Newton and Leibniz, both of them having invented Calculus. The notations we use now are Leibniz's one.
Over his life, Newton suffered of depression. He could not stand criticism. He hated Hooke and tried to destroy his documents from the Royal Academy after Hooke's death.
At the end of his life, Newton moved to London to take up the post of warden of the Royal Mint in 1696, a position that he had obtained through the patronage of Charles Montagu, 1st Earl of Halifax, then Chancellor of the Exchequer. He took charge of England's great recoining, somewhat treading on the toes of Master Lucas (and securing the job of deputy comptroller of the temporary Chester branch for Edmond Halley). Newton became perhaps the best-known Master of the Mint upon Lucas' death in 1699, a position Newton held until his death. These appointments were intended as sinecures, but Newton took them seriously, retiring from his Cambridge duties in 1701, and exercising his power to reform the currency and punish clippers and counterfeiters.
In 1703 he was elected president of the Royal Society and was re-elected each year until his death. He was knighted in 1705 by Queen Anne, the first scientist to be so honored for his work. However the last portion of his life was not an easy one, dominated in many ways with the controversy with Leibniz over which had invented the calculus.He lived for 85 years and died in agony from stones in his bladder. He refused the last sacrament on his deathbed, but is buried in state in Westminster Abbey.
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