Test 1 - 2025

Bring a calculator (not a calculator on your phone, not a calculator on your tablet) and writing instruments. I will provide for you any formulas needed.

Material covered

• Class notes that we've covered--not including atoms.
• Labs 1,2,3 - graphs, slopes, why warm around equator, seasons (not Temperature)
• Readings - Collapse: Preview and Montana
• Homework problems and readings assigned for homework.

Chapter 1 of Hobson - Our place in the universe

• How the behavior of planets and constellations in the night sky differ.
• The North Star and latitude.
• Evidence for a round Earth.
• Specialness of Zodiac constellations.
• The remarkable observation that all planets circle the sun in very nearly the same plane (close to the "ecliptic"), and move around the sun in the same direction.
• Earth's direction of rotation. Apparent rotation of stars in the sky.
• Describing the positions of things in the sky: elevation angle and azimuthal angle. Relation of these to the "horizon".
• The Greek model of the solar system, vs our heliocentric model.
• The Heliocentric model: The history starting with Copernicus and continuing with Tycho Brahe's experiments, followed by Johannes Kepler's insight about elliptical rather than circular orbits.
• Explanations for the apparent "retrograde motion" of planets.
• Galileo's observations of the phases of Venus, and other observations he made with a telescope.

Electromagnetic waves / light

• Shaking/vibrating atoms emit light waves $\leftrightarrow$ light absorption makes atoms vibrate
• Higher temperatures = higher frequency
• The E-M spectrum:
  • lower frequency than visible light: Radar, radio, microwaves, infrared (IR)
  • visible light
  • higher frequency than visible light: ultraviolet (UV), x-rays, gamma rays
• Possible ways (and examples) for light to interact with matter:
  • Transmission
  • Absorption - this causes heating
  • Reflection
• Connection with the greenhouse effect, a trap for light energy:
  Transmission of sun light through atmosphere (which is transparent to visible light) -> Absorption of visible light (by dark things on Earth's surface, like parking lots) -> Absorption of light results in heating up -> hot things give off IR radiation -> atmosphere partially opaque to IR.
• Natural greenhouse effect: If there were no greenhouse gases in Earth's atmosphere, the average temperature would be about 0${}^\circ$ F. But even in pre-industrial times there was enough $CO_2$ and other greenhouse gases to warm Earth to an average temperature of ~59${}^\circ$ F.
• Using $\lambda\cdot f = c$: $\lambda$=wavelength, $f$=frequncy (cycles/sec), $c$=speed of the wave.
• Uses for IR cameras / detection.

Lab activities

1. Labs 1, 2, 3: Rates of change. Best fit line: slope is *average* rate of change. Units of slope. The reason it's warmer when the sun is directly overhead, the seasons. Consequences of Earth's tilt as it orbits the sun: seasons; some parts (close to the poles) have days when the sun never sets, and days when the sun never rises; The tropic of Cancer and Capricorn.
2. Graphing lab: calculating slopes; positive/negative correlations
3. Why it's warmer at the equator. Angle of light relative to surface. Brightness or intensity as light energy per square meter.
4. How Earth's tilt out of its orbital plane leads to seasons.

Format of the test

• Mostly multiple choice, multiple answer (more than one true answer), true/false, short answers
• A small number of open ended questions for you to write about.
• A slope calculation.
• Even with multiple choice questions, it's *still* a fine idea to jot a note about how you're solving a problem. Sometimes that can lead to partial credit.
• Formulas: I'll give you any needed--you don't need to memorize formulas. For this exam: speed ($c$) of a wave is wavelength ($\lambda$) times frequency $$c=\lambda f$$ Slope of a line, which is also the average rate of change: $$\text{slope of a line}=\frac{\Delta y}{\Delta x}.$$