1. When & why is it hot and cold - Section 2.2
Seasons
When & why is it hot and cold - Section 2.2
CHECK THE STUDENT NOTES – THEY NEED TO BE UPDATED TO CORRESPOND TO THESE NEW TEACHER NOTES

2. 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.
Developing a working knowledge of the scientific method and how to apply it to real world situations.
Critically analyzing and evaluating information, scientific or otherwise
Learn some simple astronomical nomenclature/terminology.
Develop a sense of what scientists know about the overall universe, its constituents, and our location
Explain the causes of seasonal variations in the length of the day, the direction of sunrise and sunset, and the amount of solar heating.

3. Overarching questions
What causes it to be hot and cold?
What things could cause temperature differences?
What causes Earth summer / winter?
How is the Earth’s tilt related to seasons, if at all?
What info would you need to know to predict “seasons” on other planets?
What is precession?

4. REMINDER: Planet temperature
Depends on two things:
___________________________________

5. Absorption of visible light
Which absorbs more sunlight? Air or water/ground? How do you know?
Things that affect amount of light absorbed:
_____________________
_____________________________
Look at the map on page 40. Which is better at absorbing _______ light - Water or ground?
(technical note IR “color” is important too. Why?)
We won’t talk about color anymore. Climate models need to account for it; we don’t.
___________________________________

6. Distance
Many people think seasons are caused by the distance to the Sun.
We’re good scientists now, so what should we do?
Let’s __________________!
BESIDES temperature, predict an observation we could make from Earth associated with the distance to the Sun
Predict what we would observe.
The Sun will ____________ during _______ and ….
Write your prediction down in a place you can cover up. Again, leave a place for the correct answer that you can cover up.

7. Movie – coming soon to web page

8. Distance to Sun Closest to Sun = ____________________
Furthest from Sun = __________________
________________________
On EARTH, difference between nearest and furthest is _________________________
(__________ miles or ______________ km)
________________________________ Not without.
Compare that to the size of the entire Earth:
Radius of Earth is ___________.
Lecture tutorial, pages 91-92

9. Time absorbing visible light
Is it true that there is __________________ _____________________________? Why?
At night, is the Earth heating or cooling? How?
Does the _______time difference strengthen or weaken the idea that summer is hot because of __________________?
We’ll focus on daytime from now on. Nighttime arguments yield the same results.

10. Daytime length Our next question:
Why are daytime and nighttime lengths different at different places?

11. Daytime / nighttime & seasons
It appears we have a good explanation. Our temperature observations are explained.
Daytime length also explains why ______________________________.
_________________________________________________. You may already have heard the tilt causes the seasons.
Before we draw our conclusion, a good scientist will do what to their newly considered hypothesis?
____________________________________
Is there anyplace on Earth that gets __________________________ ______________________________________________________
What’s the temperature like there?
Is the daytime length the only important effect for hot/cold?
_____________________________. But _____________________ _______________________________________________________!

12. Season causes – what’s dominant?
So, we’ve ____________________________ as the dominant effect!?!?!
Earth-Sun _________________________ for people in US
Earth’s ___________________________ month-to-month
_________________ doesn’t explain _________________________ at any time of year, but …
___________________________________________________.
RECALL: the different day/night times were caused by …
Obviously we’ve missed something if we want a complete picture – why it’s hot and cold at different places at different times….
Let’s observe carefully as we travel to other parts of the world during different seasons.
Let’s look at the Sun from the north pole, LA, and the equator. *demo*
Aside from “always” being up, what do we notice about Santa’s Sun?
In LA, how is that different?

13. California Elementary School Science Standards for seasons
From California Science Standards, grade 3
Students know the position of the Sun in the sky changes during the course of the day and from season to season.
Students know the patterns of stars stay the same, although they appear to move across the sky nightly, and different stars can be seen in different seasons.

14. Sun location & temperature
Why does Sun location affect the amount of sunlight we absorb? Let’s examine…
Imagine a light bulb in the center of the room & your paper = ground. Make your ground catch the most sunlight.
Standing on this ground, which direction is the Sun?
Conclusion:
When __________________________________________!
Is this going to be a big effect or small effect? Why?
Work on Lecture Tutorial, page 93 ONLY

15. shade your Earth appropriately
Sun is _________________
shade your Earth appropriately
Is ground A directly facing the Sun?
Is the Sun high in the sky, midway, or low?
Will ground A be hot, medium, or cold?
Is ground B directly facing the Sun?
Will ground B be hot, medium, or cold?
Put a dot on the ground directly facing the Sun?
What would weather be like there?
Which is hotter, C or the equator?
Which hemisphere is hotter: north or south? (Clicker) A B
Earth

16. Ask your neighbor: Which hemisphere is hotter?
23°
night
day
Earth NP SP
Equator
North
South
Cannot be determined 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

17. Two pictures
The next slide shows how the Earth looks on 2 important dates.

18. Looking from one side This date is ________ This date is __________
NEIGHBOR: On this drawing, which hemisphere has summer? How can you tell?
Copy this drawing into your notes
Sun
NEIGHBOR: On this drawing, which hemisphere has summer? How can you tell?
This date is ________
This date is __________

19. Lecture Tutorial
Work on Pages

20. Season start dates & what happens
Look at the previous pictures. You should be able to convince yourself that the seasons are _______________________________________. You should also understand why.
____ (6/21)= ______. In LA = _____________. How about in Australia?
______________________ (in north)
Where is the Sun straight up?
What happens inside the Arctic circle? Antarctic circle?
Dec 21 = __________. In LA = ____________. How about in Australia?
________________________ (in north)
___________________. In LA = _____. (Vernal ________)
_________________________ (in north)
Where is the Sun straight up?
Why do you think it’s called an equi-nox?
______________________. In LA = _____ (Autumnal _______).
__________________________
See also pages _________.

21. Now you’re ready for the test
But just in case…
Try the Seasons Ranking Tasks handout for practice (outside of class).

22. Precession
See pages in textbook for this topic. (chapter 2)
You’ve probably noticed that the sky has changed a little __________ ______________________ The ancients knew about this, but it did take several hundred years of observations to figure it out.
As we’ve discussed before, the Earth’s rotation axis is tilted ________ away from its revolution axis around the Sun.
The __________________________. _________________________, however, _____. It ________ in a circle ____________________.
Over 2000 yrs this slow wobble causes a slight change in the zodiac constellations. This is why your “sign” is probably 1 earlier.
_______________________________________________. _________________________________! _________________________________!

23. What’s Your Sign? Then & Now
Constellation 2000 yrs ago Now Days Sun in the sign
CapricornUS Dec 22 - Jan 19 Jan 19 - Feb
Aquarius Jan 20 - Feb 18 Feb 16 - Mar
Pisces Feb 19 - Mar 20 Mar 12 - Apr
Aries Mar 21 - Apr 20 Apr 19 - May
Taurus Apr 21 - May 21 May 14 - June
Gemini May 22 - June 23 June 21 - July
Cancer June 23 - July 22 July 21 - Aug
Leo July 23 - Aug 23 Aug 10 - Sep
Virgo Aug 24 - Sep 22 Sep 17 - Oct
Libra Sep 23 - Oct 23 Oct 31 - Nov
ScorpiUS Oct 24 - Nov 22 Nov 23 - Nov 30 7
Ophiuchus Not part of zodiac Nov 30 - Dec
Sagittarius Nov 23 - Dec 21 Dec 18 - Jan
 Info from Wikipedia's article about the Zodiac, subtopic: Precession of the Equinoxes. This info will be on the course website.

24. Overarching questions
What causes it to be hot and cold?
What things could cause temperature differences?
What causes Earth summer / winter?
How is the Earth’s tilt related to seasons, if at all?
What info would you need to know to predict “seasons” on other planets?
What is precession?