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# 2020-09-15

- Only need to recognize Orion and the Big Dipper
- Constellations
- You can use the Big Dipper to find Polaris

- Angular size, distance, separation
- Apparent motion of the stars
- Star motion impossible to see on a daily basis because they are so far away
- Perpendicular to the horizon --> equator
- Parallel to the horizon --> North Pole

- Early Greek and Roman cosmology
- What they knew ~2500 years ago
- Earth was a sphere
- Shadow shape, changing stars as you move south

- Sun is farther from Earth than the Moon
- Eclipses

- Stars seem to slowly move in regular pattern
- Precession (Earth) wobbling

- Thought Earth was stationary (they were wrong but moving in the right direction)
- No parallax

- Ranking system for magnitude of stars
- Based on brightness

- Goals
- Distinguish among categories of numbers
- Describe positional notation
- Convert numbers in other bases to base 10
- Convert base-10 numbers to numbers in other bases
- Describe the relationship between bases 2, 8, and 16
- Explain the importance to computing of bases that are powers of 2

- Convert binary --> decimal
- Convert real decimal --> binary
- Perform binary addition/subtraction
- Two's compliment
- Number Theory
- Grace Hopper