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Transcript
ISP205 Section 2, Section ID: 577649
My notes: Lecture #3 on Tuesday 1-16-01 12:40pm – 2:00 pm
Handouts:



Quiz Kepler
Bubble sheet
Bring: Syllabus and schedule
Topics:
1. Review previous lecture
1. Homework: dont need paper
2. Ecliptic: path of the sun along the celestial shpere (west to east)
3. Planets and Moon move on or close to the ecliptic. Planets show retrograde
motion.
4. Milky way (galactic equator) almost vertical
5. Precession: North celestial pole moves around every 26000 years.
2. Example for scientific method – evolution of heliocentric model of solar system
go through history.
1. Aristotele (384 BC - 322 BC)
Work based on a priori philosophical speculation, not observation, but
mixed in observations
(earth is not moving, heavier bodies fall faster, but earth is a sphere as
everything tends to move towards its center and observation of lunar
eclipses which show bend shadow !!!)
2. Aristarchos of Samos 310 BC – 230 BC
DEMO: show picture from Redshift (the Greeks, Pg. 5,6)
pull sun forth and back to show dependence, say need distance to
moon - later
determined distance to the sun measuring angle between moon and sun at
exactly first quarter (sun-moon and moon-earth axis perpendicular). Moon
distance known from parallax across earth.
First heliocentric model of solar system (maybe because he knew from
distance of sun that it has to be so much bigger and can therefore not
revolve around something much smaller). Result: 6 times to close !
3. Eratosthenes 276 BC - 196 BC
skip( mention briefly and point to book) but say- greeks new how big
earth and how far away from sun …
(would be the Greeks, Pg 14,15,16,20 in Presentation)
determined circumference of earth by using difference of angle of sunlight
at 2 different places – at one place deep well – perpendicular sun rays –
then at Alexandria stick showed 7 degree. So know that its 7 degree
latitude difference !
so Columbus could have known how far it is to India the other way around
the earth – and in fact some people at the time could have told him
probably.
4. Claudius Ptolemy (100AC – 160AC)
Almagest: foundation of theory of solar system for next centuries
Tetrabiblios: foundation of astrology. Integration of planet astrology of
Babylonians with zodiac astrology of Egyptians.
Epicycles explained movements of planets by preserving the circle as the
standard shape. Earth centered because of absence of parallax – scientific
argument !!!
Redshift demo: Ptolemy:
Epicycles: The greeks, Pg24
Parallax:
Student demo, (SKIP ! The greeks Pg 11)
5. Nicolas Copernicus (1473 – 1543) picture
Redescovered Aristarchos idea of heliocentric solar system as a quote in
Archimedes writings. Noticed that all observations could be explained
much easier and that calculations of solar system movements, also
calendars, would be much simpler. Still needed a few epicycles as he still
used circles as planetary orbits. Published it as a simplification scheme –
not truth – and only banned 70 years later by catholic church because
written in Latin.
6. Galileo Galilei (1564-1642) picture
Founded modern scientific method of careful observations to test a
hypothesis. First man to use a telescope to look into the night sky. Found
phases of Venus ahich proved that venus orbits the sun.
Found hints that Copernicus ideas could be correct
a. Milky Way individual stars
b. Moon not some heavenly thing, but an object with a landscape like
earth - Redshift Presentation: C&G Pg. 9
c. Sunspots (not helio centr. Model – maybe skip) Redshift C&G
Pg. 10
d. Moons of Jupiter (saw 4 of them, there are 16). Proves that
something can orbit around an object that itself is orbiting another
object without being left behind Redshift C&G Pg. 11
e. Phases of Venus
First Proof that Prolemy’s model is wrong (but Brahes compromise
could still work)
Redshift C&G Pg 14: original observation
Scanned image for origin of phases of venus
ask: which one heliocentric, which one earth centered (vote ?)
Point: sometimes venus between earth and sun, but sometimes not.
Wanted to promote heliocentric model, but could not explain lack of
parallaxe. Used his wrong theory of tides to prove that earth is moving
around the sun (could not explain 2 tides !!!). Pope Urban VIII was well
educated man and admirer of Galileo and argued with him about tide
theory. Galileo wrote his “Dialogue” bashing the church not buying his
arguments for a heliocentric model – pope Urban VIII happened to be
away when manuscript was sent to him and his chief censor did not
understand it and let it pass. Pope was angry and banned book (doing
Galileo a favor because it prevented embarassment with wrong theory of
tides) arguing that there is no evidence for it and that tide theory is wrong
– so he did not want to reinterpret bible based on that. Galileo did not
revoke – lifelong house arrest.
Other things Galileo found: foundation of mechanics (discussed later)
(with Newton)
7. Tycho Brahe (1546-1601) picture
Most accurate observer of his time, without telescope but nice observatory
of an Danish island Hveen (picture) . Countless observational data of
movements of planets and positions of stars (1004 star positions published
in a catalog).
Thought if Copernicus is right he must find a parallaxe. Didn’t find it –
assumed earth is center and sun moves around earth. BUT he accepted the
simplifications in Copernicus idea and assumed all other planets move
around sun. This compromise was accepted by catholic church, which had
point of view that reinterpretation of bible was ok if enough evidence was
presented. Purely scientific arguments !!
Dec 10, 1566 he gets into an argument with a danish noble man Manderup
Parsberg about who’s the best mathematician. At Dec 29 Tycho loses part
of his nose in a duel with Parsberg. He then wore a silver replacement for
the rest of his life.
His death is also debated – some rumours say he had a rupture of his
bladder after a too large meal (others mercury poisoning)
8. Johannes Kepler (1571-1630)
Astrologer and Mathematician. Sought employment with Brahe because of
his bad eye sight, because of his strong interests in stars he wanted to use
his observational data. But Brahe was difficult character and after another
fight with Danish King he left Denmark and whent to Prague. There
Kepler managed to become hi sassitant, but he did not let him use the data.
When Brahe died, papers had to go to legal heirs, but Kepler stole the
papers.
Discovery: After 10 years trying he found Keplers Laws about the Planets
a. The orbit of the planets around the sun is an ellipse, with the
sun being at one focus. Show picture of ellipse
b. The straight line joining a planet and the Sun sweeps out equal
areas in space in equal amounts of time Show picture
First: Redshift Presentation: Keplers Laws, pg 6
Means: at shorter distance planet moves faster !!!
Then show picture of areas
c. The orbital period of a planet is related to the semi major axis
of its elliptical orbit. If we measure period P in years and the semi
major axis in AU (average distance earth-sun) then simple:
(semi major axis)3 = (period)2 or A3=P2
- the further away the planet the slower (remember Redshift demo
Do an example: Jupiter 5.2AU then
P2 = 5.23 therefore P=11.86 years !!!
9. Summary evidence for heliocentric solar system
a. Simpler, and with Kepler only accurate description of planet
motions
(epicycles had still small deviations !!!)
b. Landscapes on Moon: Earth could be a celestial object as well
(so far some claimed that celestial bodies are something
completely different than the earth)
c. Moons around Jupiter: something that moves can still have other
objects orbiting around it (Moon is not left behind my
moving earth !!!)
d. Phases of Venus: other planets orbit sun. Why not earth ??
But final proof had to wait until:
1. James Bradley 1728:
found Abberration (final proof of moving earth) (starlight comes under
angle when earth moves, but angle is opposite if opposite direction, so
stars describe ellipse on sky (~20.48’’ diameter) bigger effect than
parallax !!!
10. F.W. Bessel 1838
First detection of stellar parallax (additional proof of moving earth) from
star 61 Cygni (0.29 arc sec) – 66 trillion miles
Material:

Board and pen for aberration demo
Backup:
To do:
Overview History of Astronomy:
2. Aristotele (384 BC - 322 BC)
Work based on a priori philosophical speculation, not observation, but
mixed in observations
(earth is not moving, heavier bodies fall faster, but earth is a sphere as
everything tends to move towards its center and observation of lunar
eclipses which show bend shadow !!!)
3. Aristarchos of Samos 310 BC – 230 BC
determined distance to the sun measuring angle between moon and sun at
exactly first quarter (sun-moon and moon-earth axis perpendicular). Moon
distance known from parallax across earth.
First heliocentric model of solar system (maybe because he knew from
distance of sun that it has to be so much bigger and can therefore not
revolve around something much smaller). Result: 6 times to close !
4. Eratosthenes 276 BC - 196 BC
determined circumference of earth by using difference of angle of sunlight
at 2 different places – at one place deep well – perpendicular sun rays –
then at Alexandria stick showed 7 degree. So know that its 7 degree
latitude difference !
5. Hipparcos 190 BC – 120 BC
discovered precession by comparing his star catalogue to observations
made 150 years earlier. Also established magnitude system
6. Claudius Ptolemy (100AC – 160AC)
Almagest: foundation of theory of solar system for next centuries
Tetrabiblios: foundation of astrology. Integration of planet astrology of
Babylonians with zodiac astrology of Egyptians.
Epicycles explained movements of planets by preserving the circle as the
standard shape. Earth centered because of absence of parallax – scientific
argument !!!
7. Nicolas Copernicus (1473 – 1543)
Redescovered Aristarchos idea of heliocentric solar system as a quote in
Archimedes writings. Noticed that all observations could be explained
much easier and that calculations of solar system movements, also
calendars, would be much simpler. Still needed a few epicycles as he still
used circles as planetary orbits. Published it as a simplification scheme –
not truth – and only banned 70 years later by catholic church because
written in Latin.
8. Tycho Brahe (1546-1601)
Most accurate observer of his time, without telescope but nice observatory
of an Danish island Hveen. Countless observational data of movements of
planets and positions of stars (1004 star positions published in a catalog).
Thought if Copernicus is right he must find a parallaxe. Didn’t find it –
assumed earth is center and sun moves around earth. BUT he accepted the
simplifications in Copernicus idea and assumed all other planets move
around sun. This compromise was accepted by catholic church, which had
point of view that reinterpretation of bible was ok if enough evidence was
presented. Purely scientific arguments !!
Dec 10, 1566 he gets into an argument with a danish noble man Manderup
Parsberg about who’s the best mathematician. At Dec 29 Tycho loses part
of his nose in a duel with Parsberg. He then wore a silver replacement for
the rest of his life.
His death is also debated – some rumours say he had a rupture of his
bladder after a too large meal (others mercury poisoning)
9. Johannes Kepler (1571-1630)
Astrologer and Mathematician. Sought employment with Brahe because of
his bad eye sight, because of his strong interests in stars he wanted to use
his observational data. But Brahe was difficult character and after another
fight with Danish King he left Denmark and whent to Prague. There
Kepler managed to become hi sassitant, but he did not let him use the data.
When Brahe died, papers had to go to legal heirs, but Kepler stole the
papers.
Tried several shapes and after 10 years of study found the ellipse. Could
explain all of Brahes observations ! 3 Laws of Kepler !
10. Galileo Galilei (1564-1642)
Founded modern scientific method of careful observations to test a
hypothesis. First man to use a telescope to look into the night sky. Found
phases of Venus ahich proved that venus orbits the sun. Wanted to
promote heliocentric model, but could not explain lack of parallaxe. Used
his wrong theory of tides to prove that earth is moving around the sun
(could not explain 2 tides !!!). Pope Urban VIII was well educated man
and admierer of Galileo and argued with him about tide theory. Galileo
wrote his “Dialogue” bashing the church not bying his arguments for a
heliocentric model – pope Urban VIII happened to be away when
manuscript was sent to him and his chief censor did not understand it and
let it pass. Pope was angry and banned book (doing Galileo a favour
because it prevented embarassement with wrong theory of tides) arguing
that there is no evidence for it and that tide theory is wrong – so he did not
want to reinterpret bible based on that. Galileo did not revoke – lifelong
house arrest.
11. Isaac Newton (1643-1727)
3 laws of Newton explain all Keplers laws
12.