Scientists and Astronomy
I. Ancient
views and notions of the skies
A. Ancients paid closer attention to the skies
at night
1. There was little
else to distract them from it -- electric lighting, TV, computers,
phones, etc.
2. Likely people
would have been outdoors at night, especially in warmer seaons and
climates.
B. They identified particular characteristic
groupings of stars that we identify as constellations
1. Some of these
constellations were found in the sky at particular times of the year,
and functioned almost like a calendar
a. example: Taurus, Orion, Gemini
2. The appearance of
certain constellations in the night sky tended to indicate time to
plant, harvest, hunt certain animals.
C. This generally led many to ascribe
supernatural properties to celestial bodies in the skies, because
failure to plant, harvest, or hunt successfully was the difference
between life and death.
II.
Ancient scientists
A. Eratosthenes, Greek 2nd-3rd century BC
1. Librarian at
Alexandria
2. Determined the
size (circumference) of Earth by measuring sun angle at two places on
June 21, and knowing the distance between those two places.
B. Ptolemy, Greek 2nd century BC
1. Proposed
geocentric universe, Earth at the center, everything else orbiting it.
2. Explained retrograde
motion as
occurring because of loops in a planet's orbit, called epicycles.
a. Retrograde motion is the apparent temporary backward motion
that occurs as Earth passes up a planet in an outer orbit.
3. Ptolemy's was one
of the most enduring scientific ideas, and it was wrong.
4. Ptolemy's model
was very appealing to Christian religious leaders up through the
Renaissence, because it placed Earth at the center and focus of God's
universe.
III.
Renaissance scientists
A. Nicoli Copernicus, 15th
century, Polish
1. Proposed a
heliocentric universe, in which all the planets orbited the Sun,
instead of Earth.
2. Idea was not
widely known until after his death.
B. Johannes Keppler, 16th-17th
century, German
1. Trained as a
mathematician in religious schools.
2. Collaborated with
Tycho Brahe to derive equations to predict a planet's position.
3. Originally
struggled with the problem because he assumed planets had circular
orbits. When his assumption didn't work out, he had a personal
religious crisis of sorts, because it went against his notion that the
circle would was a perfect shape for a celestial object.
4. Once he figured
out that planets actually had elliptical orbits, he went on to propose
three laws of planetary motion:
a. Planets move about the Sun in elliptical orbits, with the Sun
located at one of the foci
b. Planets sweep out equal areas in equal periods of time
c. Planet's period of orbit is related to its distance from the
Sun
C. Galileo Galilei, 17th century,
Italian
1. First major
scientist to use telescope to study the heavens.
2. Discovered
a. Four largest moons of Jupiter
b. Saturn's rings
c. Sunspots on the Sun
d. Phases of Venus
e. Rough irregular surface of the Moon
3. He was censured
by the Church in Rome because, among other things, he supported
Copernicus model that Earth went around the Sun, not Sun around Earth.
D. Isaac Newton, 17th-18th
century, British
1.
Proposed the universal law of gravitation. Noted that the laws of
gravity that we observe here one Earth are the same laws of gravity
that occur between planets and celestial bodies.
2.
Invented calculus
3. Made
these and other important scientific discoveries in his early 20's.