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Ancient Greeks Golden Age of Astronomy - in Greece BC to 150 BC

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Presentation on theme: "Ancient Greeks Golden Age of Astronomy - in Greece BC to 150 BC"— Presentation transcript:

1 Ancient Greeks Golden Age of Astronomy - in Greece - 600 BC to 150 BC
- said earth was round - estimated earth’s circumference - cataloged stars

2 Geocentric Model Believed by Greeks…all
Earth was center of universe and everything revolved around it Was logical and made sense Unchallenged for centuries

3 Retrograde Motion As the planets passed by at night, it appeared they stopped, reversed direction, and then headed back on their original way!

4 Modern Astronomy Almost nothing new for 1500 years!
age The of enlightenment begins a new day in astronomy Nicolaus Copernicus was the 1st but other followed

5 Copernicus 1475 - 1550 HELIOCENTRIC model
Believed that Earth was just an ordinary planet… Not the center of the universe… HELIOCENTRIC model Revolved around the sun in perfect circles like the rest… This was a huge break in thinking!

6 Tyco Brahe 1550 - 1600 Had an observatory…woweee
Made extremely precise measurements Had an amazing assistant… Johannes Kepler

7 Johannes Kepler 1575 - 1625 Used Brahe's measurements
Close but no cigar… Orbits not circles, but ellipses! 3 laws of planetary motion 1 - orbits are ellipses around sun 2 - planets sweep equal areas in equal time…faster and slower 3 - distance of a planet to the sun and time to go around the sun are related

8 Galileo Galilei 1550 - 1650 Described moving objects
Redesigned telescope Gave support to Copernicus Disc 4 moons of Jupiter Planets are real objects Phases of Venus Sunspots and rotation

9 Isaac Newton 1650 - 1725 The law of inertia
The law of universal gravitation Closer = more gravity Bigger = more gravity

10 Earth - Moon - Sun 3 motions of earth 2 types of days
Rotation – once/day Revolution – once/year Precession – once/26,000 yrs 2 types of days Solar – noon to noon (24 hrs) Sidereal - 360º around (23h 56m 4s)

11 Rotation of Earth Rotates in an ellipse Sun not at exact center
Closest on Jan 3rd = perihelion Farthest on July 4th = aphelion Ecliptic = earth/sun rotation plane

12 Earth - Moon System Moon has ellipse orbit also
Perigee – closest Apogee – farthest Has phases from reflecting sunlight Full – far side of earth/sun New – between sun and earth Waning – shrinking (getting less full) Waxing – growing (getting more full)

13 Lunar Orbit About 240,000 miles away ½ is always lit…
Crescent moon < ½ showing Gibbous moon > ½ Waning/waxing crescent/gibbous 1st quarter = ½ moon after new moon 2nd quarter = full 3rd quarter = ½ moon waxing 4th quarter = new moon

14 Lunar Orbit Synodic month = moon through all its phases = 29½ days
Sidereal month = 27⅓ days… same reason for a sidereal day Orbit and rotation are the same (27⅓) Same side always faces earth Hot on lit side (260º F) Cold on dark side (-280º F)

15 Eclipses Moon between sun/earth…casts shadow on earth and blocks out sun = solar eclipse Moon on other side of earth/sun…casts shadow on moon only = lunar eclipse Don’t occur every month

16 Eclipses… Don’t occur every month! Moon’s orbit not in ecliptic…5º
Moon’s shadow usually misses Earth Umbra = full shadow Penumbra = partial shadow Corona = bright outline of sun Total eclipse is rare…Aug, 21, 2017 in USA













29 The Moon Most of our info comes from the Apollo missions of 69 – 72 (Apollo 11 – 17) Its density is like mantle rock. We think it has a small iron core. It has 1/6 the gravity of earth

30 Dark lowlands = maria Light highlands No atmosphere = no weathering…also means constant bombing of small debris…rocks get rounded. Its biggest features are craters from impacts Some craters have rays = bright lines from impact.

31 Highlands Most of the lunar surface Cover far side of the moon

32 Maria Dark and relatively smooth
Are beds of basaltic lava from meteor impacts Mare = singular, maria = plural

33 Regolith Most of surface covered by a layer of debris
Is soil-like and called lunar regolith Composed of ig rx, glass beads, and fine lunar dust from impacts Approx 3 meters thick!

34 Lunar History Most widely accepted model for formation is impact from a mars sized body early in earth’s history. It dates to about 4.5 billion years old, about the same as earth.

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