Light & Earth’s atmosphere. Chapters 5 and 10 (Hints of chapter 2, more later). Learning Outcomes, Objectives, & Goals. Appreciating science in general, and astronomy in specific. Understanding how knowledge is gained and be critical of what you see and hear.
Chapters 5 and 10
(Hints of chapter 2, more later)
Textbook combines “reflect” & “scatter” together.
See figures 5.2 & 5.3 on pages 151-152.
Why is the sky blue? Scattering! See pages 304-305 (not on your test)
Depends on two things:
Seven types of light, in order (see page 155). Sun emits ALL of them!See percentages below for what hits the ground.
(Highest frequency smallest wavelength)
(Lowest frequency longest wavelength)
Speed of light = (light wavelength) x (light frequency)
Constant number = ONE OF THESE GOES UP, OTHER GOES DOWN
For the rest of this course, we’ll focus on:
For OUR solar system, that means focusing on:
The worst damage, by far, occurs over seasonsAntarctica.Ozone Hole over Antarctica
Fortunately nobody lives there! There are also precious few animal species there. How lucky!
Equally fortunate is that we found this problem and its cause in time! Here is a more recent map of the ozone layer. It’s not as good as we’d hoped.
Production of CFCs were banned worldwide in 1988. Look at the chart after 1990. CFCs are dropping! Predictions were that the worst damage to the ozone layer would occur by 2000, and then it would start “healing”. BUT: in 2007, the hole got bigger. Hopefully the healing will (re-?)start soon! EXPECTED TO BE BACK TO NORMAL LEVELS IN 2065-2070.
Important point: international effort was necessary and seems to be working.
What would happen if we wrapped the Earth in a seasonsvisible-light transparent but infra-red blocking substance? Talk to your neighbor. I’ll solicit answers from you.
From James Hansen’s PowerPoint downloaded from his NASA –Goddard web page. The next slide’s graphs are from an article he wrote a few years ago. This graph was SET to zero for a specific year. The century-long change is the important idea here.
The temperature of the Earth is clearly rising (middle graph).
We see: average temperature of Earth has increased about 0.5 ˚C = 0.9 ˚F in the past 30 years. This is much faster than scientists can explain without human influence.
Coincides with huge increase in CO2 from burning fossil fuels. Levels now higher than any level seen in past 400,000 years and rising. (Was 280 ppm in 1850; in 2009 it’s 387 & rising 2.4/yr. In 1980’s rose 1.4 ppm/yr, <1ppm/yr before then)
Other changes: sea level has risen, carbonation in the oceans increased (i.e. oceans are storing much of our CO2).
Global warming IS NOT RELATED TO THE OZONE LAYER.
You’ve probably heard about the “controversy” surrounding global warming.
Here are facts:
EVERYONE who understands the data agrees that the Earth’s temperature is rising.100% of scientists agree the temperature is rising in the long term (over many decades).
The only “controversy” was WHAT IS CAUSING the temperature to rise.
If we continue to do what we are doing now, we are in deep trouble. - Ogunlade Davidson, IPCC
But if we separate the US into states…
China has now (in 2008) overtaken the US in total CO2.
China’s rate is growing faster than the US, largely due to coal and cement plants. But they have a lot of catching up to do.
Bottom line: Most scientists predict several degrees
of additional warming during the coming century,
mostly caused by human emissions.