Like addicts racing to get their overdue fix, my students raced to the computers this afternoon after having had to survive all day without power and without the internet. I’ll confess that I felt the same urge, but was able to restrain it. Until now.
We usually don’t have internet access during our immersions, but then it’s expected and students are not inside needing to refer to the study guides to figure out their assignments. At the beginning of the year I gave everyone paper copies of the study guides, but now there are just a core few who request them.
Fortunately, we had a couple of smart-phones so one student would look up the reading assignment and post the page numbers on the whiteboard. Fortunately, the reading assignments were out of the book.
We weren’t quite surviving without technology, but it was close, and students were getting innovative.
We’ve had storms every few days for the last couple of weeks, which is typical for Memphis at this time of year. Over the last few days a frontal system has just been pushing back and forth over us. When it pushes south we get a cold front with thunderstorms and rain, but clear skies afterward. When the front pushes north it gets warm and humid, and the sky goes overcast for most of the day.
Weather map for Wednesday, April 20th. The blue and red line passing through the southeastern U.S. show the mixed warm and cold fronts that have been oscillating past Memphis for days. Image from the National Weather Service.
This line of fronts marks the general location of the sub-polar low, which is moving north with the spring. But more on that tomorrow.
Jonas Bendiksen has an amazing website of photos, sounds and stories from life in slums in South America, Africa and Asia. It’s quite a poignant. You get wide-angled photos from far away and then the photographer steps closer to his subjects until you’re in a panorama of someone’s small apartment, hearing their story.
If learning is not for its own sake, it isn’t liberal learning. It’s a utilitarian calculus for material self-advancement. The important things are not worth knowing because they are useful. They are worth knowing because they are true. [my italics]
This quote, feeds off a plea by Freddie DeBoer against our constantly putting things in terms of dollars, cents and economic value. It argues against much of the premise of behavioral economics (and much of environmental economics too), which tries to better understand human nature by translating everything into money.
The economists themselves will tell you that this remains just one part of the story, and the work brings us to a better understanding of how humans behave and what they really value, but, living in a very capitalist society, it’s easy to lose track.
Talk about a long day! (“What an understatement,” she says.)
The 'before' picture.
We moved about 45 tons of sand, gravel and compost today, filling in the moat we dug last week. We were lucky enough to have the help of a backhoe for the digging, but all the filling in today was done by hand, with shovels and wheelbarrows.
Digging the moat.
Despite rumors about it being a first line of defense against the Cordovan barbarian hordes, the moat was actually intended to become a rain garden, which was designed by the Rhodes College Hydrogeology class to intercept some of the runoff slope that funnels water directly down toward the school during the intense rainfall that we get with our spring and fall mid-latitude cyclones.
So we had to get rid of the heavy, dense, silty-loam soil that is really slow to let water seep through, and makes it hard to grow anything on the Memphis side of the Mississippi River. The fine grained silt was blown over from the Mississippi River floodplain about 20,000 years ago when the ice-age glaciers were melting and all their ground up rock flour was being washed down the Mississippi. This type of wind-blown sediment is called loess. I like the sound of the word because if you stretch out the “oe” properly it does something to the back of your throat that feels distinctly German; however, if you ask someone from the deep south to pronounce it, you’ll hear the name of Clark Kent’s girlfriend.
Middleschooler pushing a wheelbarrow full of silty-loam.
The backhoe dug two trenches, each about 2 m wide, 6 m long, and about 60 cm deep, and piled the soil up next to the holes. Moving this stuff is not trivial. My middle-school students gave it a try on Friday afternoon and though they made a small dent, there is an awful lot more to do (my students also helped figure out how long it would take to finish pumping out Friday morning’s collected rainwater from the trenches).
Five cubic yards of pea gravel.
Then, on Saturday, with large piles of the old soil still sitting there, we replaced the impermeable loam with a fifty-fifty mix of sand and compost, underlain by five centimeters of pea-sized gravel on top of five centimeters of crushed limestone. This material was delivered by dump truck on Friday afternoon, while school was still in session. It was loud, exciting, and according to one member of the pre-school aged audience, “the best day ever!”
Enjoying the 'best day ever.'
I have to agree. It was kind-of exciting. Although for me, the bright, brown pile of pea gravel evoked fond memories of pyramids of powdered curry, saffron and tummeric sitting on the spice-seller’s stall in a market in Morocco .
Rhodes students slacking off (after lugging soil and gravel all day).
For others the pea gravel was a more tactile experience: snuggling into it, after a hard day’s work, appeared to be quite therapeutic.
Girl Scouts taking a well earned break.Middle school students slacking off (after ...?).Hauling silty clay.Dr. Jen raking in the first of the gravel in the not yet drained pit.Wagon team.Team Z. on the top of the mound.Gravel tossing.It begins.Mixing soil.More mixing.Grading.The last of the pile. Job well done.
My students and I had a great chance to use the our recent geometry work when we figured out how long it would take to drain the new moat in front of the school.
It’s not really a moat, it’s going to be a flower bed that will soak up some of the runoff that tries to seep into the school’s doors every time a spring or fall thunderstorm sweeps through.
The hole was dug on Thursday evening and filled with rainwater with water, half a meter deep, by Friday morning’s rain. At least we know now that the new beds are in the right place to attract runoff.
But to fill the trenches with gravel, sand and soil, we needed to drain the water. With a small electrical pump it seemed like it would take forever; except that we could do the math.
The pump emptied water through a long hose that runs around the back of the building where the topography is lower. I sent two students with a pitcher and a timer (an iPod Touch actually) to get the flow rate.
They came back with a time of 18.9 seconds to fill 4 liters. I sent them back to take another measurement, and had them average the to numbers to get the more reliable value of 18.65 seconds.
Then one of the students got out the meter-stick and measured the depth of the moat at a few locations. The measurements ranged from 46 cm to about 36 cm and we guesstimated that we could model the moat as having two parts, both sloping. After measuring the length (~6 m) and width (2 m), we went inside to do the math.
Rough sketch of the volume of water in the moat.
With the help of two of my students who tend to take the advanced math option every cycle, we calculated the volume of water (in cm3) and the flow rate of the pumped water (0.2145 cm3/s). Then we could work out the time it would take to drain the water, which turned out to be a pretty large number of seconds. We converted to minutes and then hours. The final result was about 7 hours, which would mean that the pump would need to run until 10 pm.
I’ve been helping my wife model the fluid flow through her apparatus, and she has some really neat results from some experiments where two chemicals react and block off the regular, symmetrical flow.
The streamlines look a bit like butterfly wings to me, so I modified the image a little. The original flow paths through the circular apparatus are below. I’m not sure which image I like better.
Flow paths through a circular cell. Mineral precipitates (not shown) are blocking flow through the middle.
P.S. The other thing I learned from this little exercise is how to write Scalable Vector Graphics (svg) files (W3C has an excellent reference). With svg’s, like other vector graphics formats, no matter how big you blow them up you never loose resolution like you would do with a regular, rasterized image. Unfortunately, I still have to figure out how to include the svg files on this blog, so these png images will have to do for now.
Just in time for the standardized testing season, Gillum and Bello have a damning article on irregularities in the testing at some Washington D.C. schools. NPR has a good summary of the situation and the investigation.
Sadly, with the fates of their schools and their jobs depending on the outcome, the faculty and staff administering these tests to their own students face an unfortunate conflict of interests and are placed in a serious moral hazzard. It’s also not hard to imagine the potential for ramped-up pressure on the students.
Standardized tests can play an important role in maintaining quality in the vast network of schools that make up the US’s educational system. They also help maintain consistency, of which a certain amount is probably good, but can be awfully restrictive. But the most unfortunate aspect about the way they’re actually used, is that they create intense pressure on students and faculty that is deleterious to student performance on the tests themselves, and severely restricts the way students think about what it means to learn.
The big black thing in the foreground is part of a water-filled dyke that was deployed against the flooding of the Red River in North Dakota. Image Source: MPR Photo/Ann Arbor Miller.
One of the key advantages of free market economies over strict socialist ones, is the much greater incentive to innovate. NPR has a wonderful case study in free enterprise in this article on the use of new water-filled tubes instead of sandbags to prevent flooding.
The design of the water-filled dykes, from the page of the company, Aquadam.
NPR’s interview the inventor of the AquaDam and talk about how he came up with the idea (playing with water balloons), how the water-filled dykes work, who are using them, and how much they costs.
The only things that were a little difficult to understand, was the description of the tubes themselves, and the explanation of why they don’t move. The idea is pretty simple, but an image helps.
