1-5
Solar System, Milky Way Galaxy & the Universe.
cosmic environment
Planetary sciences: study of planets, moons & minor bodies (asteroids and comets)
Atmospheric properties, composition, history & formation.
1 x 10^-5.
Geocentric model of anaximander
“Celestial sphere” (think about a planetarium). ~600 B.C.
Retrograde motion on the sky because
B) Planets orbit with different velocities around the Sun, resulting in apparent reversals of their motion if observed from one of the planets.
Technology that enables true scientific us very recent
<100 year
Biology occupies almost every niche on Earth.
Extremophiles
Observed movement of planets, moon, sun. Used these movements to keep track of time, seasons, & mark dates for agricultural importance. Knew solar & lunar eclipses. The sky was a clock, calendar, map, & book of stories. Attributed the motions and events to arbitrary acts of supernatural beings.
Ancient People
How do we know the Earth is round?
Round Earth was known by 500BC.
2. IN A PLANETARY SYSTEM THERE ARE 3 PLANETS: A, B, & C. THE INNERMOST PLANET A ORBITS FASTEST, WHILE THE OUTERMOST C ORBITS THE SLOWEST. YOU ARE AN ASTRONOMER ON PLANET B OBSERVING THE OTHER PLANETS FOR YEARS. WHAT WILL YOU SEE?
A. Neither A or C shows retrograde motion.
B. Both A and C show retrograde motion.
C. A shows retrograde motion but C does not.
D. C shows retrograde motion but A does not.
How do we search for life in the universe?
Earth life is diverse, yet it is strikingly similar on its most fundamental levels - yet that may not be universal.
Carbon-based life. Complex organic molecules found in the universe - interstellar clouds, meteorites, in atmospheres of moons.
Earth
Many civilizations realized periodicity & patterns in celestial event
Babylonians: (modern-day Iraq) recorded eclipses & by 2500 BC recognized a periodic pattern, kept accurate astronomical diaries for long period.
Planets moved on the sky
“Wanderer” in Greek move differently from the stars…
But his model is not accepted because - Observed stellar parallaxes appear to be zero. Philosophical “Platonic” bias for heavenly perfection of spheres.
Aristarchus propose heliocentric mode
Recent discoveries that motivate search
1) Solar System Exploration: some planets & moons offer conditions that may allow primitive, microbial life.
2) In addition to stars the Universe also harbors a great number of planets.
3) Deeper understanding of biology & advances in analytical / remote sensing technology allows search in ways unimaginable a few decades ago.
Evidence that organic molecules form easily & naturally. Evidence that life appeared early in the history of the Earth. Evidence that Earth life can survive under a wide range of conditions.
Biology may be common in the universe
~150 BC capable of predicting lunar phases (month, day, hour), planet positions, eclipses, & calculated the dates of the Olympic.
Machine From
How many spheres did the Greeks need to account for the visible celestial bodies?
Ptolemaic system continued to dominate for
1,800 years!
Astronomy
Earth in the Solar System (geocentric vs heliocentric), cosmic structures, history & evolution of the universe. Multitude & diversity of stars, planets, and moons.
Scientific notation - human population 7,726,610,00 (7.7 billion)
7.73 x 10^9.
Not yet "modern science" but the key elements are there
1. Trying to understand nature without supernatural explanations. Process: suggest & debate new ideas & improve on them.
2. Greeks developed mathematics (as geometry) & applied it engineering and scientific problems, but also realized its independent value.
3. Experiments & observations can test ideas - if the explanations contradict the observations, it should be discarded.
Apparent motion of a planet moving in the opposite direction of the rest of the planets in that system for a brief period of time.
Retrograde motion
Fall of the Western Roman Empire (376-476 CE). Europe fragmented to many kingdoms engaged in constant battles. Princes, priests, and peasants. Feudal Lords: controlling land and life. Church: controlling spiritual life and afterlife
Dark Ages