Presentation on theme: "Ancient Greeks Golden Age of Astronomy - in Greece - 600 BC to 150 BC - said earth was round - estimated earths circumference - cataloged stars."— Presentation transcript:
Ancient Greeks Golden Age of Astronomy - in Greece BC to 150 BC - said earth was round - estimated earths circumference - cataloged stars
Geocentric Model Believed by Greeks…all Earth was center of universe and everything revolved around it Was logical and made sense Unchallenged for centuries
Retrograde Motion As the planets passed by at night, it appeared they stopped, reversed direction, and then headed back on their original way!
Modern Astronomy Almost nothing new for 1500 years! age The of enlightenment begins a new day in astronomy Nicolaus Copernicus was the 1 st but other followed
Copernicus 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!
Tyco Brahe Had an observatory…woweee Made extremely precise measurements Had an amazing assistant… Johannes Kepler
Johannes Kepler 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
Galileo Galilei Described moving objects Redesigned telescope Gave support to Copernicus Disc 4 moons of Jupiter Planets are real objects Phases of Venus Sunspots and rotation
Isaac Newton The law of inertia The law of universal gravitation Closer = more gravity Bigger = more gravity
Earth - Moon - Sun 3 motions of earth 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)
Rotation of Earth Rotates in an ellipse Sun not at exact center Closest on Jan 3 rd = perihelion Farthest on July 4 th = aphelion Ecliptic = earth/sun rotation plane
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)
Lunar Orbit About 240,000 miles away ½ is always lit… Crescent moon < ½ showing Gibbous moon > ½ Waning/waxing crescent/gibbous 1 st quarter = ½ moon after new moon 2 nd quarter = full 3 rd quarter = ½ moon waxing 4 th quarter = new moon
Lunar Orbit Synodic month = moon through all its phases = 29½ days Sidereal month = 27 days… same reason for a sidereal day Orbit and rotation are the same (27) Same side always faces earth Hot on lit side (260º F) Cold on dark side (-280º F)
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 Dont occur every month
Eclipses… Dont occur every month! Moons orbit not in ecliptic…5º Moons shadow usually misses Earth Umbra = full shadow Penumbra = partial shadow Corona = bright outline of sun Total eclipse is rare…Aug, 21, 2017 in USA
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
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.
Most of the lunar surface Cover far side of the moon Highlands
Dark and relatively smooth Are beds of basaltic lava from meteor impacts Mare = singular, maria = plural Maria
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! Regolith
Lunar History Most widely accepted model for formation is impact from a mars sized body early in earths history. It dates to about 4.5 billion years old, about the same as earth.