Tues, 3-12 Look for the comet tonight!

Due Monday, 3-15:  Both optional assignments
AND
HMWK read p. 223-237; p. 229# 1-3, 5-7 and Compare / Contrast the Mars Curiosity mission with the Spirit and Opportunity rovers.  AND P. 237#1-6.
Work on this early before the break and you won't have it hanging over your head this Sunday please!

Today in class: most classes got to some demonstrations on why the sky is blue (at least during the day it appears so) and why the sun looks yellow, why sunrise/set and moonrise/set and lunar eclipses look yellow, orange, or red... scattering of light that takes place first on the violet end of the spectrum, but if light passes through more atmosphere, then more scattering takes place with other colors.  
The sky is blue and not violet because:
1) we can't see violet very well with our eyes; it is violet... at least at high altitudes it looks close.
2) by the time light reaches the Earth's surface, much of the violet has been scattered so much that it has been absorbed by the atmosphere.
The sun looks red because: 
If the blue light is scattered into the atmosphere, we see (white - blue ) = yellow.  I will verify this with some artificial lights when we study waves at the end of the semester.
The sunrise/set and moonrise/set look orange because:  
As light comes in at an angle to Earth's surface at these times, it passes through a much larger layer of atmosphere (think of cutting a loaf of bread straight down vs. an angle; the angle cut results in a much longer cut).  The greater distance results in greater interaction and scattering, leaving less blue and green light, leaving mostly red.  This can be enhanced by more particles in the air (smog) or after a big volcanic eruption.
The eclipsed moon appears red or orange because as light passes through the Earth's atmosphere, it is turned red... again with the scattering.   Light also is bent due to slowing down as it moves into the atmosphere, acting as a lens to move light around the Earth, illuminating the otherwise shadowed moon.

We also used liquid crystal thermal - sheets to simulate seasons in most classes and started a demonstration or two about the Doppler Effect, which is the shortening or lengthening of wavelengths based on velocity of an object emitting any type of wave.  (we can only do it with water and sound in class, but things moving really fast relative to us (stars) can do it with light).