Azaleas and Dogwoods at the National Arboretum


The best-known of the flowering plant collections at the US National Arboretum is probably the Azalea Collection, which I mentioned a few years ago. Back when I was in high school, my parents took me to see them several times—my previous post included some photos from 2002—but I hadn’t seen them since I left for college. This June, two Caltech friends and I went to the Arboretum and I got a chance to take more photos of them, though we were only able to see part of the collection, since much of the hill they’re on is closed off to protect bald eagles nesting there.

One question for biologists who may be reading this: I noticed several azaleas with small sections of the plant that had flowers a different color than the rest. My initial thought was that it might have to do with local variations in the soil pH affecting some roots but not others. However, it seems that I was confused and soil pH affects flower color for hydrangeas, not azaleas. Anyone have a guess as to what is happening?

After seeing the azaleas, we wandered deeper into the Arboretum and saw the Dogwood Collection, which was also in bloom. We also headed down the slope to the banks of the Anacostia River. I do need to get my bike fixed and actually bike along the lower part of the Anacostia, which now has bike trails. Eventually, they’re supposed to extend along its whole length, but I have no idea when that might happen.

Hydraulic Jumps In Your Kitchen Sink


A while ago, someone at MIT claimed that the ring-shaped phase change one sees between fast-moving and slower-moving water one sees on the bottom of a kitchen sink when water is running was due to the water dropping below the speed of sound. I initially believed this, until the Tall Kitty convinced me that there was no way the water could be moving at near the speed of sound. More recently, I came across a physics blog post explaining what’s actually happening. It turns out that this is a related phenomenon I’d never heard of called a hydraulic jump. In fact, this is the same phenomenon as one sees at the beach when water moving inland from a crashed wave seems to flow over the receding water from the previous wave with a visible discontinuity at the edge of the inland-moving wave: the only difference is the frame of reference.

A hydraulic jump is in fact similar to a shock wave, in that both involve fluids flowing faster than waves can travel in the fluid. In a shock wave, such as is produced in an explosion, a front of moving fluid moves into a region of stationary fluid faster than sound—compression—waves can travel in the stationary fluid. This prevents the stationary fluid from “knowing” that the moving fluid is approaching and thus prevents a gradual increase of pressure as the front compresses the fluid in front of it.

However, the critical speed in a hydraulic jump is not the speed of sound, but the speed of surface waves in the liquid, (g h)^(1/2), where g is the local gravitational acceleration (9.8 m/s^2) and h is the depth of the liquid. For the water in your sink, which might be an eighth, this is about half a mile an hour. While I don’t know enough fluid mechanics to have a good understanding for why this is the speed of surface waves in a liquid, it is in face the same formula that gives the natural speed of a ship hull as a function of its length. I suppose the overall lesson from this is that I need to sit down and read a fluid dynamics textbook at some point. Not that I actually ever seem to read science textbooks for fun….

Status Update: Walking to Wheaton along University Boulevard

A map of my walk, with mile markers.

A map of my walk, with mile markers.

This last weekend was a bizarre exception to normal DC summer weather. On Saturday, it rained two inches steadily all day, without any thunder or lightning. And Friday through Sunday the high temperatures were in the seventies. Finally, on Sunday, I decided I had to take advantage of the nice weather to go for a long walk. However, when I started out, I was only planning on walking five or six miles: that it turned into a nine-and-a-half mile walk was purely an accident of my misunderstanding of local geography.

I started out my walk by walking two miles west through the University of Maryland campus to the confusing intersection of Campus Drive (which runs roughly east-west through campus), Adelphi Road (which runs north-south), and University Boulevard (MD-193), which makes a nearly ninety-degree turn here, from running south along the western side of campus to running nearly due west. Here, I started west along University Boulevard, which I followed for the remainder of my walk.

The next three miles of my walk were the most interesting, as I followed University Boulevard through the border between Takoma Park and Langley Park, a three-mile stretch known as the “International Corridor”, which is to be served by three stations on the Purple Line if it ever gets built. It certainly could use a more transit-oriented and walkable retrofit: right now, it consists of a six-lane highway lined by shopping malls whose parking lots connect to form de facto service lanes. Despite this, there was very heavy foot traffic on the narrow sidewalks and quite frequent bus service that seemed to be heavily used. I passed by the construction site where the Takoma-Langley Transit Center is being built, as well as an incredible number of tasty-looking Mexican, Salvadoran, and Indian restaurants. I also got asked the time in Spanish by an old lady who presumably saw my watch. Unfortunately, my Spanish sucks, but I hope that my answer (tres y cuarenta for 3:40 pm) was understood correctly. I really need to practice more.

At the end of the International Corridor, I should have followed the planned Purple Line route west along Piney Branch Road. Instead, I decided to keep going west on University Boulevard, convinced that I would reach the Red Line along Georgia Avenue fairly quickly. However, I didn’t realize just how far north University Boulevard runs from this point on, and it turned out to be a four-and-a-half mile walk through residential areas of single-family homes fronting on University Boulevard. After passing through the small and—after the International Corridor—anticlimactic commercial district of Four Corners, there was nothing else of note until I finally reached Georgia Avenue in downtown Wheaton, where University Boulevard, Georgia Avenue, and Viers Mill Road meet.

The last time I’d been to downtown Wheaton was about seven years ago, when I passed through on a bike ride up Sligo Creek to Wheaton Regional Park. I was surprised by how much more urban and vertical it seemed than last time. And a little jealous of the twenty-four-hour Safeway grocery store adjacent to the Metro station. My legs were too sore from walking nearly ten miles for me to look around much, though, so I descended the longest escalator in the Western Hemisphere into the Wheaton Metro Station to ride back to College Park.

Old Photos from High School


Besides taking a camera—disposable because my mom was afraid a real camera would be stolen—to graduation and grad night, I also took a camera—also disposable—to the last day of school, including “Donut Day”, the end-of-the-school-year celebration in my calculus 3 and differential equations class. A number of people brought friends who weren’t in the class to Donut Day, so those photos include a number of people who weren’t actually in the class.

High school graduation was a decade ago!

My high school graduation in the basketball arena of the University of Maryland.

My high school graduation in the basketball arena of the University of Maryland.

It is a little terrifying to realize that my high school graduation was a decade ago. Actually, at this point, it’s more like a decade and a month ago: I’d forgotten until being reminded by people on Facebook that we actually graduated at the end of May, even though school normally didn’t let out until mid-June. Anyway, I almost didn’t go to the ceremony. It seemed a bit absurd and somewhat irrelevant—getting into Caltech seemed like a bigger achievement, and I never felt that socially connected to my high school—and it was a massive production in the University of Maryland’s basketball arena because there were six hundred and sixty of us. It also ended up being really unpleasantly loud. There were people in the stands with airhorns, and because the people with high GPAs were seated in front, I ended up being right next to a huge loudspeaker that gave me a headache even with my ears covered.

The evening after graduation was an event called “grad night”, where they locked everyone into a community center from dusk until dawn to keep us from getting drunk or doing drugs or whatever normal teenagers do after graduating. I didn’t want to go to this either, but my mom talked me into it by arguing that I’d miss people even if I didn’t realize it. She also wouldn’t let me take my yearbook to get people to sign it (someone might steal it), but instead gave me a packet of stapled-together papers for people to sign.

Status Update: Applying for Community College Adjunct Jobs


It’s now been about a week since I’ve made progress on my Master’s thesis. As I mentioned in my last Status Update post, a lot of this break was due to having friends visiting and then being exhausted afterward. However, today and yesterday were consumed by applying for chemistry and physics adjunct teaching jobs at three local community colleges, in PG County, Howard County, and Anne Arundel County. I’m not really clear on how much of a chance I have, since my Master’s Degree won’t be official until after the Fall semester begins, and they also don’t say when the deadline for applying for the Fall is: I just applied to the general pool they use each semester.

For those of you who aren’t familiar with what adjunct professors are, or how the American university system treats them, the answer is roughly “poor” and “poorly”. From Wikipedia’s article on the topic:

Adjuncts are not funded to maintain currency in their fields of expertise. Often, adjuncts will work for several universities simultaneously, trying to come up with an adequate compensation package. They have been called part of the “working poor”.[22] In 2014, a national news story described the situation of adjuncts as “Juggling multiple part-time jobs, earning little-to-no benefits, depending on public assistance: This is the financial reality for many adjunct professors across the nation.”[23] In 2015, an adjunct professor stated that he taught five courses but made less than a pet sitter.[24]

Even if I do manage to get some of the jobs I applied for, the pay appears to be $700 for each “credit-hour” (an hour per week of classroom time) for a fifteen-week semester. Assuming two hours of grading, lesson prep, and office hours per hour of classroom time, that comes out to about $15/hour: what several cities have been increasing their minimum wages to. And this is with no benefits: no sick leave or health insurance, though I should qualify for Medicaid if there isn’t a rule that you can’t have savings. With luck, I can find some freelance tutoring to make ends meet, but even if I do, this isn’t a viable long-term plan, given that there’s no guarantee of continually getting enough classes to even cover rent, and I’ll only be getting paid during semesters, anyway. I have to hope that somehow I’ll be preparing students to be more economically successful than it seems I will be.

In happier news, I did get to have dinner with the Violinist yesterday. I hadn’t seen her in months because work has been so busy: she works for a biotech firm and has had to work sixty to eighty hours a week even though she doesn’t get paid for overtime and only gets paid about $30.000/year. However, she’s finally quitting at the end of this month to go back to grad school for a PhD from the University of Pennsylvania. I hope it will go better for her than grad school went for me. In any case, it was nice to get to spend some time with her, and to see what Franklin’s General Store—where we ate—has become. When I was an epsilon, my mom took me there a couple of times for Christmas shopping and it had a little deli counter where I got hot chocolate. Now it’s a sort of absurd and terrifying two-story gourmet restaurant where I wouldn’t’ve considered eating if she wasn’t paying.

Estimated US Energy Use in 2014

A plot of US energy production and consumption in 2014 from Lawrence Livermore National Lab:

A plot of US energy production and consumption in 2014 from Lawrence Livermore National Lab:

The Eldritch Kitty recently made me aware of this chart of energy production and consumption in the US and I thought it was interesting enough to share. Some observations that surprised or interested me:

  • I wouldn’t have guessed that almost a quarter of electricity production in the US is nuclear: I thought it was closer to ten percent. I also didn’t realize that almost half percent of electricity in the US comes from coal, though I guess it isn’t surprising, since coal is cheap and we have a lot of it.
  • I also didn’t realize that two-thirds of the energy spent on electricity production is wasted. It’s not clear to me how much of this is transmission loss versus waste heat in power plants but, basically, electricity is expensive compared to other sorts of energy.
  • I am a bit surprised to find out that we have geothermal power plants in the US: for some reason I’d been completely unaware of that. On the other hand, apparently no residential customers still use coal heating, but some commercial ones do?
  • Interestingly, some hydro gets used industrially without being converted into electricity. Are there still water-powered sawmills or something somewhere?
  • The main lesson from the transportation section of this seems to be that internal combustion engines are really inefficient. Close to four-fifths of the energy used for transportation (mostly gasoline and diesel internal-combustion engines) is wasted. Of course, while electric cars don’t produce huge amounts of waste heat, electricity production is still fairly inefficient, and about half of it comes from fossil fuels.

Status Update: Visitors, Paping, and Exhaustion


Over the past two weekends, four different friends from Caltech visited me. I’m not entirely sure how this happened other than coincidence, since two of them were visits I only had a couple of days’ notice of. In any case, it was nice to get to see people I hadn’t seen in a long time, but by the end of it I was quite exhausted. Since people left on Sunday afternoon, I haven’t managed to get any thesis work done, and I’ve spent a lot more time sleeping than I should.

The weekend before the most recent one, the Dog came to visit from Princeton. It was a fairly short visit, but we managed to do a number of things. We started by going on a several-mile walk that terminated in him buying a whole watermelon, which he ended up eating more than half of in two days. We then went downtown to see some museums and had dinner with my parents at the swimming pool. Then, on Sunday, we got up early and hiked Section A of the Billy Goat Trail at Great Falls. It was a neat trail, and I don’t think I’ve ever hiked on anything quite like it before: it was incredibly rocky and included having to boulder down a forty-foot rock face. (There will be a blog post with a bunch of photos once I get them off my camera.) However, it was also really hot, and while wearing synthetic pants and underwear did help a bit with keeping me from being too soaked, I was still horribly sweaty afterward. I also ended up being incredibly exhausted and out of breath: it was a good reminder of just how out-of-shape I’ve gotten.

This last weekend was even busier with visitors. The Broken Frosh, the Papist, and the Library Frosh all visited from Thursday through Sunday. This was perhaps too much visiting for one weekend, honestly: all the sight-seeing and socializing we did (including my first trip to the National Arboretum by bus) exhausted me. It didn’t help that I managed to get a cold on Friday, which I’m still recovering from. I’m feeling better now, but still coughing a lot and sleeping more than I should be.

On Sunday, right before the Papist and the Library frosh left, we and Odin went to Mass at the Basilica of the National Shrine of the Immaculate Conception. I was impressed by how pretty it was, and took a number of photos that will appear in a later blog post. It was also the first time I’d been to Mass since my grandmother’s funeral twelve years ago. It was an interesting experience and, unsurprisingly, was much more high church than the couple of services at Old Cambridge Baptist Church that the Medieval Grad Student got me to go to when I was at MIT.

Cherry Blossoms at the National Arboretum


Since the Boston friends who visited me in April had come to see the cherry blossoms, I suggested that if they wanted to see even more trees, I could take them to the National Arboretum the next morning before they headed back to Boston. They were quite excited about it, especially when they realized that the National Bonsai and Penjing Museum was there. We ended up spending about an hour and a half wandering around the museum before rushing back to the car so I could get them to Metro in time for their trip back. While most of the collections weren’t in bloom yet, we did see a number of cherry trees in bloom, and also went on a nice walk through Fern Valley.

Status Update: Got Internet, and a Respiratory Infection


I’ve been off the internet for the most part for the last three days because my internet in my apartment was down. It’s finally back. However, I also seem to have acquired some sort of cold or similar respiratory infection, complete with a sore throat and really clogged up nasal passages. I hope I’ll recover a bit soon…


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