Astronomy

Attachments:

• earth

1. solstices
   1. summer

      Annotations:

      • jun 21st
   2. winter

      Annotations:

      • dec 21st
2. equinoxes
   1. vernal

      Annotations:

      • march 20th
   2. autumnal
3. equation of time

   Annotations:

   • days are sometimes longer or shorter than others due to non circular orbit of earth
4. types of day

   Annotations:

   • sidereal: 23 hrs 56mins                  time to rotate 360 degrees
   • solar: 24 hrs             time for sun to get to same position in sky
5. aurorae

   Annotations:

   • spectacular light shows near north and south poles
   • caused by particles in solar wind interacting with earth's magnetic field
6. Eratosthenes

   Annotations:

   • On summer solstice in Syene, sun was at zenith
   • also, at same time in Alexandria, sun was 1/50th of a circle south of zenith
   • as Alexandria was due north of Syene, the arc from Alexandria to Syene must be 1/50th circumference of earth
   • distance from alexandria to syene was about 790km so circumference of earth must have been about 39500km

1. diameter
   1. 1.4 million km
2. distance to earth
   1. 150 million km
3. orbital period
   1. at poles
      1. 36 days
   2. at equator
      1. 25 days
4. photosphere
   1. 5,800K
5. Atmosphere
   1. Chromosphere + corona
   2. 2 million K
6. Nuclear fusion
   1. Hydrogen nuclei fuse
      1. into helium
   2. reaction
      1. tritium + deuterium --> helium + a neutron (+ energy)
   3. Heavier elements are formed in supernovae
7. Solar wind
   1. charged particles ejected from upper atmosphere
   2. enough energy to escape sun's gravity
   3. reaches heliosphere at edge of solar system
   4. partially deflected by earth's magnetic field
   5. can damage satellites and electrical transformers
   6. causes aurorae

1. Features
   1. Seas
      1. Sea of Crises
      2. Sea of Tranquility
      3. Ocean of storms
      4. Formed by large craters that filled with lava and solidified
   2. Highlands
      1. Apennine Mountain range
   3. Craters
      1. Tycho
      2. Copernicus
      3. Kepler
2. Rotational period
   1. 27.3 days
3. Orbital period
   1. "
4. Diameter
   1. 3500km
5. Distance from earth
   1. 380,000km
6. Far side
   1. more craters
   2. more highlands
   3. fewer seas
7. Giant Impact Hypothesis (GIH)
   1. Theia collided with young earth
   2. Evidence
      1. relative abundances of oxygen isotopes are almost identical to earth's
      2. it was once molten
      3. moon has iron core like earth
      4. observed similar collisions in other systems
      5. computer simulations support hypothesis