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 itWas logical and made senseUnchallenged for centuries
3 Retrograde MotionAs 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 astronomyNicolaus 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 modelRevolved 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 measurementsHad 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 motion1 - orbits are ellipses around sun2 - planets sweep equal areas in equal time…faster and slower3 - 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 telescopeGave support to CopernicusDisc 4 moons of JupiterPlanets are real objectsPhases of VenusSunspots and rotation
9 Isaac Newton 1650 - 1725 The law of inertia The law of universal gravitationCloser = more gravityBigger = more gravity
10 Earth - Moon - Sun 3 motions of earth 2 types of days Rotation – once/dayRevolution – once/yearPrecession – once/26,000 yrs2 types of daysSolar – 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 = perihelionFarthest on July 4th = aphelionEcliptic = earth/sun rotation plane
12 Earth - Moon System Moon has ellipse orbit also Perigee – closestApogee – farthestHas phases from reflecting sunlightFull – far side of earth/sunNew – between sun and earthWaning – shrinking (getting less full)Waxing – growing (getting more full)
13 Lunar Orbit About 240,000 miles away ½ is always lit… Crescent moon < ½ showingGibbous moon > ½Waning/waxing crescent/gibbous1st quarter = ½ moon after new moon2nd quarter = full3rd quarter = ½ moon waxing4th quarter = new moon
14 Lunar Orbit Synodic month = moon through all its phases = 29½ days Sidereal month = 27⅓ days… same reason for a sidereal dayOrbit and rotation are the same (27⅓)Same side always faces earthHot on lit side (260º F)Cold on dark side (-280º F)
15 EclipsesMoon between sun/earth…casts shadow on earth and blocks out sun = solar eclipseMoon on other side of earth/sun…casts shadow on moon only = lunar eclipseDon’t occur every month
16 Eclipses… Don’t occur every month! Moon’s orbit not in ecliptic…5º Moon’s shadow usually misses EarthUmbra = full shadowPenumbra = partial shadowCorona = bright outline of sunTotal eclipse is rare…Aug, 21, 2017 in USA
29 The MoonMost 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 = mariaLight highlandsNo atmosphere = no weathering…also means constant bombing of small debris…rocks get rounded.Its biggest features are craters from impactsSome craters have rays = bright lines from impact.
31 HighlandsMost of the lunar surfaceCover far side of the moon
32 Maria Dark and relatively smooth Are beds of basaltic lava from meteor impactsMare = singular, maria = plural
33 Regolith Most of surface covered by a layer of debris Is soil-like and called lunar regolithComposed of ig rx, glass beads, and fine lunar dust from impactsApprox 3 meters thick!
34 Lunar HistoryMost 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.