Chp. 2 - Early History of Astronomy
The Greeks
Geocentric
- earth centered
Wanderers - planets
-
sun
-
moon
-
Mercury
-
Venus
-
Mars
-
Jupiter
-
Saturn
on the
celestial sphere
Aristotle
(384 - 322 BC)
-
Astronomy - spherical earth
-
Chemistry - 4 Basic elements
-
Physics - motion
Aristarchus
(312 - 230 BC)
-
sun centered
-
calculated dist to sun and moon
-
calculated sizes of sun and moon
he was wrong but on the right track
Eratosthenes
(276 - 194 BC)
-
calculated circumference of earth - ~2% error
Hipparchus
(~100 BC)
-
star catalog ~ 800 stars
-
determined brightness of stars - 6 magnitudes
-
calculated length of year within 4 minutes
-
predicted eclipses w/in hrs.
Ptolemy
( 141 ) -
Almagest
-
earth centered
-
circles for orbits
a.
deferents
b.
epicycles
-
retrograde motion
Accepted for ~13 centuries -> the power of the Roman C.C.
Why did astronomy change? $$$$$$$$$$$$$$$$$$$$$$
what is happening in the world at this time?
Nicolas Copernicus
(1473 - 1543)
Polish
Cleric -> religious man
Politically correct - thought his book would cause trouble so he dedicated
it to the Pope
De
Revolution
ibus, Orbium Coelestium
On the
Revolution
of the Heavenly Sphere
-
Earth was a planet
-
sun was in the center -
heliocentric
the most talked about but least read book in history?
it still used:
-
circles for orbits
-
epicycles
-
does not really explain retrograde motion
But it does:
-
determine the distance to the planets
-
determine the period of the planets
1600 - Giordano Bruno -> burned at the stake
Tycho Brahe
(1546 - 1601)
-
Best naked eye astronomer of all time
-
built the best instruments
-
used research teams -> get the best help & give it the hardest problems
-
He can't find stellar parallax
-
ultimate party animal -> Can you really have to much
FUN
? --> no nose & real jerk
Johannes Kepler
(1571 - 1630) Last astrologer/astronomer - celestial harmonies
God as mathematician
Kepler's 3 Laws of Planetary Motion
Ellipses
Equal Areas
p2 = d3 needs the
Astronomical Unit (AU)
1 AU = dist from Earth to sun 150 x 106 km
Galileo Galilei
(1564 - 1642)
Thought vs. experiment
Falling objects - LT of Pisa
Using a telescope -> he did NOT invent it, so who did?
-
4 satellites (moons) of Jupiter -
I Eat Cream Gravy
a. determined their period
b. dispelled belief that Earth would leave the Moon behind
-
Planets are disks - Earth like?
-
Venus has phases like the moon
phases indicate an orbit inside the Earth's
-
Moon is not smooth
a. mountains
b. craters
c. plains - mare - seas
-
Sunspots - sun is not "pure"
a. determined rotational period
In 1616 the RCC declares the Copernican system illegal! (Yes, this will
work)
Wrote Sidereus Nuncius ( The Starry Messenger ) b/c it
didn't discuss philosophical implication and was in Latin the RCC let it
slide
Wrote Dialogue of the Great World Systems in Italian
He was exonerated by the RCC* in 1992 -> so they issued a stamp! Anything
for a buck
*Really Cash Crazy
What else and who else is around at this time?
Pascal, the Ninja Turtles
What is the Rest of the world doing?
Isaac Newton
(1643 - 1727)
-
Laws of Motion
Inertia
F = ma
Action = Reaction
-
Law of Universal Gravitation
F m1m2/d2
FG = G m1m2 / d2
m FG
d FG
mass vs. weight
moon 1/6 Earth
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