Universe:
     Universe: about 14 billion years old (plus or minus a couple billion):  hard to estimate
        age determined by searching for oldest light coming to Earth, and using the "light version" of the Doppler effect
            Doppler effect:  when a train or car passes by, honking its horn, the tone changes
                the change in tone is caused by the train moving towards you or away from you, changing the frequency
                the more the train moves away, the greater the Doppler effect, the greater the change in tone
        use the same principle with light coming from distant galaxies
            the more change in frequency, the more "red shift", the farther away and the greater the age
        one task of the new space-based Hubble telescope is to detect very ancient light.
 
     Universe started from Big Bang, when all matter was condensed down into a ball the size of our present solar system
        Universe is expanding in all directions, all objects moving away from everything else, no "center"
 
Solar System
     includes Sun, the major planets, the moons of the planets, the asteroids and some comets
    4.55 billion years old (4,550,000,000 years old), age well constrained (see below)
    formed from a giant spinning ball of solar dust and gases
        dust particles and chemicals attracted to each other due to gravity, collapsed down into solar system
            called "condensation model", Sun and other objects condensed out of dust and gases
        can see the various stages of condensation in outer space

Earth as a Planet, the "Third Stone from the Sun"
      Earth:  oldest Earth rock 4.1 billion yrs old (older rocks recycled or hiding deep down)
          oldest rocks found on continents; ocean rocks all very young (< 200 million years)

Meteorites:  rocks that fall out of space onto Earth.  while still in space, called "meteors"
    3 major sources of meteorites
        1.  asteroid belt, between Mars and Jupiter, main source of meteorites (see below)
        2.  Lunar meteorites from the Earth's moon
            regular meteorite smacks into The Moon, bits of Moon are rocketed into space, wander around, crash to Earth, collected
            about a half dozen known meteorites have come from the Moon
                we know they are lunar meteorites because we have Moon samples to compare to, from the Apollo missions
        3.  Martian meteorites from Mars
            same story.  for example, meteorite AH00081, collected in Antartica
                asteroid hit Mars millions of years ago, 16000 years ago meteorite fell on Antarctic glacier, collected in 1984.
                NASA announced that AH84001 had fossilized Martians clinging to it, small rodlike objects
                    now believed they are NOT Martians, instead formed by chemical processes

Meteorites from the Asteroid Belt
    Asteroid belt between Mars and Jupiter is a "failed planet", should be a planet there, but collection of bits into planet didn't happen
        broken pieces of planetesimals occupy asteroid belt; early phases of planet formation that did not get big enough
    3 major types of meteorites come out of the asteroid belt
        A.  "irons":  meteorites made from iron and nickel alloy, about 6% of meteorites
            represent "cores" of small planetesimals, where heavy elements settled out under gravity
            have characteristic triangular Widmanstatten pattern formed in these giant crystals of iron and nickel
        B.  "stony irons":  about 1%.  transitional between irons and stones
        C.  "stones", divided into two groups
            C1:  chondrites, called because of the round little blebs ("chondrules") found in these meteorites, about 86%
                most primitive of meteorites, have composition very similar to Sun, reflect earliest Solar System history
                have the oldest ages as well, about 4.55 billion years old.
            C2:  achondrites, very similar to common Earth rocks, about 7%
                some achondrites are Lunar and Martian meteorites
 
 

go to top of page