Tuesday, April 23, 2013

It might be hard, but...

The result of blowing bubbles in my backyard
While reading a textbook* aimed at first year science students, deep in a chapter, I came across this passage:

 “... because a mathematical description of the coriolis deflection involves vector equations and, hence, is difficult to grasp, we will rely on a more general and somewhat inaccurate explanation of the concept.” 

Now, the author did put the technical stuff in an appendix, which began with: “Although few understand the coriolis effect...” 

The author's right, vector calculus can be hard, but, that’s beside the point. All sorts of things are ‘difficult to grasp’ yet we do them anyway. This textbook is for students in a first year science course. We should be inspiring them to go on and study more science, not scare them off because of perceived difficulty. Why even mention concepts are ‘difficult’ or that ‘few understand’?

Reminds me of an old article in the Onion about how science is hard (here).

We are doing ourselves a disservice when we set up things as hard - if you are interested, hard things are doable and should be tackled. I don’t think people aim to be a professional dancer or lawyer thinking they are on an easy path. Science is the same. The fact that there is so much complexity in the world around us is fascinating and we’ll never run out of new things to learn.

Why not present information in a science textbook without judgement on how difficult the concepts are? I’ve never come across another textbook that did. Unfortunately, there was more:

“Unfortunately, the concept of vorticity is difficult to grasp without a background in physics and mathematics ...” 

And that was the end of the discussion of vorticity.

On a tangent... some time ago, I rushed into the living room to catch a science story on the news about how a particle was clocked traveling faster than light (which has since been shown not to be the case). At the end, the anchor (Peter Mansbridge) questioned why we should care about this result and the science correspondent (Bob McDonald) gave a good answer. Then the next story was about the auction of Elizabeth Taylor’s jewels and no one ever questioned why we should care. Interesting...

*the textbook is Invitation to Oceanography by P.R. Pinet. Over all, it reads well, has nice figures and is easy to follow.

Friday, April 12, 2013

Tilting Isopycnals (the simplified version)

Sunset over Cumberland Sound
One of the things I’m attempting to determine is if the Baffin Island Current*, which passes outside of the mouth of Cumberland Sound, bends into the sound. Last summer, we were able to conduct two rounds of CTD** casts at regular intervals across the sound's mouth. Unfortunately, I wasn’t actually there as I was too pregnant to be at sea. I doubt I would have fit in the bunk as the ship we used is a particularly cramped research vessel (picture here).

Even though it was cramped, the ship had a hull-mounted current meter. Unfortunately, the instrument wasn’t turned on. No one on board had the knowledge to fiddle with it, so I missed out on that data (that’s the way it goes sometimes). Without measured currents, how does one infer water flow from CTD data?

The Baffin Island Current is geostrophic, that is, the pressure gradient force is balanced by the Coriolis force. In this case, friction and tides become unimportant and can be ignored when calculating current flows.

The pressure gradient force is the weight of water as the sea surface height is not at the same everywhere. This force is always directed from areas with high pressure to areas of low pressure. Without a balancing force, a parcel of water will move from the area of high pressure to the low one. But, there is another force out there to balance with - the Coriolis force.

Actually, the Coriolis force isn’t a real force; instead it is like an imaginary friend that shows up to solve a problem. It pops up when we treat our rotating planet as though it’s an inertial frame of reference to use Newton’s laws. Newton's laws form the base of ocean physics - and most other things that aren't moving too fast or are too small. Now, we’ll move on to pretending the Coriolis force is real. This force acts in different directions depending on the hemisphere, since I work in the northern hemisphere, I’ll take it as acting to the right.

As soon as the parcel of water from above starts to move because of the pressure gradient force, it will be acted upon by the Coriolis force and deflected to the right. The result will be a current that flows along an isobar (line of constant pressure) - a geostrophic flow.

In the ocean, pressure is difficult to measure. Fortunately, pressure is related to density and density depends on salinity and temperature which I measured. In the Arctic, where Cumberland Sound is, density depends mostly on the salinity, however, since I measured both I used both. I’ve calculated density and plotted up lines of constant density, which are called isopycnals. From plotting a cross-section of density, isopycnal slopes tell us if water flows in or out of the section, which is exactly what I’m looking for (note: isobars and isopycnals have opposite slopes).

From isopycnal slopes, a relative velocity can be calculated as currents move faster where the isopycnal slopes are steeper. Actual velocities would have been nice to get, leaving me wishing I had been on the ship to turn on the current meter. However, relative velocities still answer my question of whether the Baffin Island Current bends into my site. The answer is yes it does.

*The Baffin Island Current is the official name of this current which passes along the coast of Baffin Island (a nice diagram showing it can be found in this paper). Many currents have assigned names, the Gulf Stream and Kuroshio are perhaps more familiar examples. 

**CTD stands for Conductivity Temperature Depth. From conductivity, salinity is calculated. This instrument samples the water as it descends directly down from the ship resulting in profiles of these properties with depth.

Tuesday, April 9, 2013

Urban Nature

diversity in the garden
Why should you cultivate dandelions in sidewalk cracks, spiders in the attic and mushrooms in lawns...

Now that spring has fully arrived, I’m spending time weeding my garden. Volunteer plants have sprung up everywhere, like, well, weeds. I’m not pulling everything out - much to the annoyance of my neighbor who claims my few dandelions are an eyesore even though millions are in the park across the street.

Even in an urban environment (like where I live), we’re still part of nature. Urban living doesn't have to mean surrounding ourselves with a concrete jungle; we can still make room for diversity in nature. Even the dandelion that takes root in a tiny crack in the pavement and the moss that grows on your roof counts as diversity.

Diversity is important because it adds a complexity that makes an ecosystem stable. A single change that destroys one species is not a big deal if many species fill that niche, but a very big deal if it was the only species. For this reason, any ecosystem with only a few species is vulnerable. Consider a lawn containing a single species of grass - soon weeds will move in or nutrients will be used up, forcing the owner to take drastic action like applying herbicides or fancy synthetic fertilizers. Or, consider diversity in relation to our food crops: using a single variety can result in crop failures and no back-up to turn to. A sad example is the potato famine that occurred in Ireland between 1845-1852 (from wikipedia article here). Even though there are many varieties of potatoes on this planet, the Irish only planted a select few species and blight wiped them out - bad, bad news.

A diverse ecosystem, in contrast, acts to buffer the effects of change. No one goes out into an old growth forest and sprays the dandelions (although, exotic plants can still invade). My garden, which I pack full off as many different crops into my tiny yard as I can, will always produce me something.

Taken as a whole, the Earth is an example of a diverse ecosystem and can be considered a biosphere. People have dabbled in creating artificial biospheres since at least Victorian times. On a small scale, you can go out and buy an 'ecosphere' which is a sealed glass ball filled with water. Inside the sphere is a little ecosystem consisting of shrimp, algae and bacteria, which isn’t very diverse. In 1986, Carl Sagan wrote a glowing article about these ecospheres called, 'The world that came in the mail'. Their makers say these glass worlds can last up to 10 years, but critics say the shrimp are slowly being poisoned by their own waste while starving. Perhaps a bigger biosphere is needed.

Biosphere 2 (earth is Biosphere 1) is a 3.14 acre sealed greenhouse in Arizona that is broken up into several different types of ecosystems. Each ecosystem included several species that filled the same ecological niche, and soils were seeded with micro-organisms in an effort to enhance diversity. In the early 90's, an experiment was conducted by sealing in eight volunteers to simulate using a biosphere for space colonization. I remember seeing the ad for volunteers and being fascinated with the idea; however I had other commitments at the time and couldn't apply - which is perhaps for the better.

These eight people to be were sealed into Biosphere 2 for two years where they grew their own food. Their atmosphere was also enclosed, so the only oxygen available came from the plants within the biosphere. It turns out the biosphere wasn't a stable system: carbon dioxide levels fluctuated widely and oxygen levels couldn't be maintained. All the pollinating insects died, while cockroach and ant populations overran the place. The people sealed inside couldn't grow enough produce, forcing them onto calorie restricted diets.

One result of this experiment was to demonstrate that creating a stable biosphere is currently outside our capabilities. Since we haven’t successfully made a new biosphere, Biosphere I is all we have. So don't get rid of all the diversity that pops up or moves in. Keep a little diversity at home.

Monday, April 8, 2013

Reading, thinking, writing

I love dandelions when they've gone to seed
I spend most of my time doing one of three things - reading, thinking or writing. All are activities done alone. I hope the end result will be something creative and I’ve read that solitude is necessary for creativity.

Right now I’m reading Quiet, The Power of Introverts in a World That Can’t Stop Talking by Susan Cain. I bought the book last week when I found out my local book shop didn’t have this one in yet (a book I’m very much looking forward to).

I’m about half-way through Quiet, which means I’ll be done in a couple of days. I’m finding the book fascinating, especially since I’m an introvert. I’ve always known I’m an introvert and I’ve always counted that as one of my strengths, even when others have not.

Quiet is about the value of introverts in our extrovert-centric society, especially around creative work. It is clear from research that brilliant ideas often come from people who mostly work alone, where group work typically results in ideas that came from the one that spoke the loudest - not necessarily the smartest.

She writes about how brainstorming in theory produces better ideas that individuals working alone - an idea that many team-building sessions glom on to. However, the actual research shows the opposite is true. When brainstorming and working in solitude are subjected to an actual test, more and better ideas are generated when working alone. Perhaps, I’ll point that out next time I’m forced into a brainstorming session (more likely, I’ll simply endure it).

In another interesting study she found, violin players were compared who all spent the same amount of time practicing. The best musicians were the ones that spent the most time working alone in ‘deliberate practice’ - which translates to working specifically on a nuance or skill where the musician struggles. The idea of a ‘deliberate practice’ intrigues me.

I’m looking forward to reading the rest of the book

As a tangent, the author describes herself this way: “I’m prone to wild flights of self-doubt, but I also have a deep well of courage in my own convictions. I feel horribly uncomfortable on my first day in a foreign city, but I love to travel. I was shy as a child, but have outgrown the worst of it.” - a description that would also apply well to me.