Transcript Slide 1

Fact vs. Theory
A fact is something
that is proven to be
true.
The atomic number of
Hydrogen is 1.
A theory is something
believed to be true. It
is based on facts.
Continental Drift Theory
Heliocentric vs. Geocentric
The SUN is the
center of the solar
system.
The EARTH is the
center of the Universe.
Thales of Miletus
• Born:
– about 624 BC in
Miletus, Asia Minor
(now Turkey)
• Died:
– about 547 BC in
Miletus, Asia Minor
(now Turkey)
Thales of Miletus
• Thales believed that
the Earth floats on
water and all things
come to be from water.
• For him the Earth was
a FLAT DISC floating
on an infinite ocean.
Thales of Miletus
• It has also been claimed that
Thales explained earthquakes
from the fact that the Earth floats
on water.
• Again the importance of Thales'
idea is that he is the first recorded
person who tried to explain such
phenomena by rational rather
than by supernatural means.
Aristarchus of Samos
• Born: about 310 BC in Greece
• Died: about 230 BC in Greece
He is the first person we
know of to believe in the
HELIOCENTRIC model of
the solar system.
Eratosthenes of Cyrene
• Born: 276 BC in Cyrene, North Africa
(now Shahhat, Libya)
• Died: 194 BC in Alexandria, Egypt
1. Calculated the circumference of
the Earth by comparing noon
shadows at two different cities.
2. Calculated the tilt of the Earth's
axis.
Hipparchus of Rhodes
• Born:
– 190 BC in Nicaea
(now Iznik)
• Died:
– 120 BC in
probably Rhodes,
Greece
Hipparchus of Rhodes
•Hipparchus believed in
the geocentric model of
the Universe.
•Hipparchus calculated
the length of the year
with great accuracy.
(only 6.5 minutes off)
Claudius Ptolemy
• Born:
– about 85 in Egypt
• Died:
– about 165 in
Alexandria, Egypt
Claudius Ptolemy
• Ptolemy believed in a
geocentric model of the
Universe.
• He based much of his
work on that of
Hipparchus.
• He believed that the Earth
did NOT move in any way.
•He wrote the book ALMAGEST.
Claudius Ptolemy
• In order to explain
why the planets
seemed to move
backwards he said
that the planets
move on little circles
moving on bigger
circles.
Why do you think
the Ptolemic System
stayed the same
for 13 centuries? Think
of at least 2 reasons.
Nicolaus Copernicus
• Born: 19 Feb 1473
in Torun, Poland
• Died: 24 May 1543
in Frombork,
Poland
Nicolaus Copernicus
• Copernicus developed a
heliocentric model of the
solar system.
• He gave the Earth many
new motions. Rotation &
Revolution
• He made one mistake
though; he said that the
planets orbited the sun in
perfect circles.
Nicolaus Copernicus
• He did write his theory in a book
called On the revolutions of the
heavenly spheres.
• But it was not published until the
end of his life. He saw the first copy
on his deathbed.
Tycho Brahe
Born:
14 Dec 1546 in Knudstrup,
Denmark
Died:
24 Oct 1601 in Prague,
Bohemia (now Czech
Republic)
•Tycho was a supporter of the
Ptolemic system.
•He believed the Earth was the
center of the solar system and
that it wasn’t moving.
Tycho Brahe
•Tycho made the most
accurate observations
of the stars and planets
to date.
•He was doing this in
support of the Ptolemic
system.
•His observations were
eventually used to
prove Copernicus’
heliocentric model.
Johannes Kepler
• Born:
– 27 Dec 1571 in Weil der
Stadt, Württemberg, Holy
Roman Empire (now
Germany)
• Died:
– 15 Nov 1630 in Regensburg
(now in Germany)
Johannes Kepler
• He began as a Ptolemic
system believer but during
college converted to the
Copernican system of the
solar system.
• He worked for Tycho Brahe
for a short period helping to
make observations.
• He wrote 3 Laws of Planetary Motion
1. Planets move in elliptical orbits.
2. Planets in elliptical orbits move
faster when closer to the sun.
3. There is a definite relationship
between a planet’s distance from
the sun and the time it takes to
complete an orbit.
Galileo Galilei
• Born:
15 Feb 1564 in Pisa
(now in Italy)
• Died:
8 Jan 1642 in Arcetri
(now in Italy)
Galileo Galilei
• Galileo supported the
Copernican model.
• He wrote to Kepler in 1598
and stated he believed this;
but did not publicly state
this for years.
Galileo Galilei
In support of the Copernican model, he
found that Venus went through phases
similar to that of our moon.
Galileo
Galilei
In support of the
Copernican model, he
also found that Jupiter
had four ‘stars’ orbiting
it.
Galileo Galilei
• Galileo was tried by the Inquisition in
1633 and was found guilty of heresey.
He was placed
under house
arrest for the
remainder of his
life.
Sir Isaac Newton
• Born:
– 4 Jan 1643 in
Woolsthorpe,
Lincolnshire,
England
• Died:
– 31 March 1727 in
London, England
Sir Isaac Newton
• Newton wrote the Universal Law of
Gravitation.
…all matter attracts all other matter
with a force proportional to the
product of their masses and
inversely proportional to the square
of the distance between them.
Sir Isaac Newton
• Newton also concluded that
INERTIA and GRAVITY combine to
keep planets in orbit around the sun.
• Inertia keeps them moving.
• Gravity attracts them to the sun.