20, April 2007 ARSC 011 Lab No. 10 Lab No. 10 Earth's Seasons and Lunar Cycles 1. A Reason for the Seasons When it's summer here in Milwaukee, WI, it's actually winter in Buenos Aries, Argentina, and vice versa in the winter. This is because seasons are based on temperature changes, not the calendar year. For example, the warmest part of the year is known as summer, whether it's July or December, depending on which hemisphere one is in. In order to explain why we experience four different seasons in Milwaukee, an explanation of these temperature changes must be given; for only then can we discover the reason for the seasons here in Milwaukee. Figure 1.1 shows an "outer space" view of the Earth's orbit and tilt around the sun during each season's peak month. For example, the "summer solstice" shows Earth's tilt and orbit during July/January and the "winter solstice," January/July. Daily temperatures, which regulate particular seasons, vary depending on the amount of sun that remains above the horizon for a certain amount of time. Then we must ask, what regulates how long the sun is above the horizon? And what regulates the amount of sun in the sky? The answer to both questions is the same: the tilt of the Earth. The tilt of the Earth remains a constant 23.5 degrees. Because of the Earth's orbit around the sun and its own 1 revolution/24 hrs., combined with its relatively permanent tilt, different parts of Earth are tilted towards and away from the sun during different times of the year. In Figure 1.1, Milwaukee [and the rest of the Northern Hemisphere, are tilted towards the sun. Thus, the sun is directly above Milwaukee for the longest period of time and its rays are strongest and most direct during this time. Therefore, when a particular hemisphere is tilted
towards Earth, it will experience summer. Also, when one hemisphere is pointed towards the Earth, the other is not. This explains why places like Buenos Aries in the Southern Hemisphere experience winter during our Milwaukee summers. Figure 1.2 is an excellent illustration of the northern hemisphere's seasons according to temperature. You can see that the northern hemisphere is hottest in the summer and coolest in the winter and that the southern hemisphere is just the opposite. As far as autumn and spring are concerned, think of it as Earth's "transitioning period." In the spring, Earth's tilt is beginning its shift towards the sun where it will soon become summer. This is why spring in Milwaukee is warmer than fall and winter, but cooler than summer. The same is true for autumn. When the Earth begins to tilt away from the sun, there are less direct rays and the days become shorter because the sun spends less time above the horizon. Those less direct rays cause shorter, colder days to surface and soon enough, winter arrives as the particular hemisphere is tilted away from the sun. Some people believe that since Earth's hottest average temperature occurs in July, Earth must be closest to the sun during this time. However, this is another scientific myth. The Earth is actually farthest from the sun in July, but because there are more land masses that absorb and retain heat in the northern hemisphere during this month, it is recorded as the Earth's hottest month-of-the-year. This data most closely resembles data from our class' lab. In exercise #1, we saw how the sun hit certain parts of the Styrofoam ball, but not others. The same is true for Figure 1.2's data. It shows how the sun heats the Earth and creates different seasons depending on Earth's tilt!
Figure 1.1
source: http://www.madison.k12.wi.us/planetarium/seasons_diagram.gif Figure 1.2
http://sofia.fhda.edu/gallery/geography/images/seasons_insolation2.gif During our pre-lab knowledge assessment, I knew that Earth's seasons were influenced by its tilt and our area's relation to the sun, but I did not know much about the tilt itself or how it "creates" seasons. Also, I wrote "These tilt patterns change the Eath's proximity to the sun," when in actuality, the tilt affects a particular hemisphere's relation to the sun. Also, I could ot elaborate on the vernal and autumnal equinoxes as I did in our post lab quiz. All I said was "fall
and summer land somewhere in between," which is a vague statement I clearly did not know what I was talking about.
2.) Lunar Phases
Heidi, for this part of the lab, our hard copies weren't returned to us and my Ocean Lab isn't stored on my computer so I chose a new tidal pattern to analyze and explain. Sorry for any inconvenience re: grading, etc.
In the Ocean Lab, I explained that tides are the alternating changes in sea level in relation to land that occur in the Earth's bodies of water because of the sun and moon's gravitational attraction. Lab no. 10 helped develop a deeper understanding of that idea. Table 2.1, below, shows the tidal pattern for seven days at Elliott Bay in Seattle, Washington.
Table 2.1
Tides for Seattle (Madison St.), Elliott Bay starting with June 1, 2007.
Day
High 1 /Low 1 1 1 2 2 2 2 3 3 3 3 Low High Low High Low High Low High Low High Low High
Tide Time 12:13 4:30 11:49 7:39 12:53 5:03 12:27 8:15 1:34 5:39 1:07 8:52 AM AM AM PM AM AM PM PM AM AM PM PM
Height Feet 8.0 9.9 -2.1 11.5 8.1 9.8 -2.3 11.6 8.1 9.6 -2.4 11.6
Sunrise Sunset 5:16 AM 8:59 PM
Moon
Time
% Moon Visible
99
F
Set 5:06 AM Rise 10:30 PM
Sa
5:15 AM 9:00 PM
Set 5:56 AM Rise 11:21 PM
99
Su
5:15 AM 9:01 PM
Set
6:59 AM
96
Table 2.1 represents a tide table for June 1, 2007-June 3, 2007. In the farthest right hand column, there is data that shows what percent of the moon was visible. The number are near 100 percent. Also, notice the highest tide for the day, they are nearly 12 feet. Now, look at figure 2.1, this is the lunar calendar for June 2007.
figure 2.1
June
Mo Tu We Th Fr Sa Su
22 23 24 25 26
2 4 5 6 7 11 12 13 14 18 19 20 21 25 26 27 28 29
3
9 10 16 17 23 24
It shows that during the first three days of June (when the tide table says 98-99 percent of the moon was visible), the moon was in its "full moon phase." Spring tides occur during full moon and new moon phases. This means that because of the moon's rotational position on the opposite side of Earth than the sun, the sun is able to reflect off nearly the entirety of the moon's surface and we see a "full moon." This also means that because the moon's orbit is in the shape of an ellipsis, the moon is closer to Earth and thus, its gravitational force is greater and we experience higher tides than at any other time of the month. During this time, and because of the planetary alignments, both the sun and the moon's gravitational forces are greater, which is why we see such similar patterns during the full moon and new moon phases. The same is true for the other phases of the moon, re: its distance from Earth and the correlation between how much of the moon is visible and what the tides are. 3.) Metacognitive Skills and Lab 10 [information is from lecture unless otherwise noted] Metacognition is an important part of education. It influences how students learn and how teachers instruct. It refers to self-thought, self-responsibility for learning, and initiative. Metacognitive skills enable us to reflect and improve both our learning styles and our teaching techniques. For this particular lab, I developed a few metacognitive skills such as plan development and monitoring. The pre-lab questions gave me a goal to work towards: I wanted to understand the answers to these questions and thus, was able to play closer attention when topics were discussed that directly related to my lack of knowledge. In a sense, the pre-lab questions guided and focused my learning during lab. Also, I was able to stop and ask myself whether I
was positively working towards my knowledge goal for the day. In lab this week, I stopped to check both the mini-lab questions and the pre-lab assessment questions. If I felt as if I were drifting or that I didn't understand something, I asked questions and made more of an attempt to understand the material. For example, when we were discussing the seasons in lab, I was a bit lost at times. However, I asked questions about the material I wasn't sure of. In the past, I probably would have just thought "If I don't understand it now, I can always look it up later.". As result, writing this lab was easier than the others because I feel as if I knew the information more thoroughly than in the past. I will admit, it does help having the lab questions at the end of the labs because that focuses a lot of my learning and I know what I need to take more thorough observations of. I also developed my reflective thinking skills in this lab because the more you practice reflection, the easier it is and someday, it'll be second nature to reflect on activities, decisions, etc. Post-lab reflection: I thought that this lab was probably the least stressful and most successful out of all the labs we've completed. I made an honest attempt to understand the concepts of each exercise and tried to comprehend the information instead of referring to an outside source, such as the internet. My course of thinking in lab 10 produced better results than I would have expected. For example, writing the lab was much easier and I felt like I knew the information I was analyzing well enough that I referred more to my lab notes than I did an electronic source. If I were to re-do this lab, I probably would have chosen to draw more illustrations and show how they directly relate to the concepts. I had a hard time remembering how things looked in lab, such as the demonstration of the moon's phases. Overall, though there were some stumbling blocks, I'd say
this was one of my more successful labs because not only did I understand the concepts more clearly, I came away with a different way of thinking about problem solving, etc.
Sources: Tide Table: Table 1.1 http://www.saltwatertides.com/cgi-local/nwsource10.cgi Lunar Calendar: Figure 2.2 http://kalender-365.de/lunar-calendar.php?yy=2007 Metacognition: Lecture