You are currently browsing the category archive for the ‘teaching’ category.

On my recent flight to Florida I took a break from reading Moby-Dick and switched to my favorite Hemingway book, The Old Man and the Sea. Maybe it was because I was on my way to the warm, sunny Gulf of Mexico, but after Melville’s overblown descriptions of the deep, dark sea and the deep, dark creatures that dwell within it, Hemingway’s terse yet elegant description of the waters of the Gulf stream were a joy, flowing through my mind like those very waters I approached. I read non-stop during the flight and finished the book (ok, it’s pretty short) just before we landed.

I think there’s a lot to be learned in comparing these two books – not an accident, I think, as Hemingway wrote to a publisher that Melville was one author he was still trying to beat. Did he? Hmmm . . .

Santiago is the eponymous Old Man (I’ve always wanted to use the word eponymous), an aging fisherman who has struck a run of bad luck – 84 days without a fish. His luck has been so bad that he’s lost his helper and his student, a boy named Manolin. Manolin’s father insists the boy join another boat, and so he does so, though he still takes care of the old man each morning and each evening. Once the boats sail, there is nothing Manolin can do to help the old man. For over a month Santiago has gone out alone, with only his oars, his sail, his meager fishing gear – and a lifetime of experience.

Today, a lovely day on a lovely warm ocean in the month of September (“The month when the great fish come – anyone can be a fisherman in May”), Santiago’s luck changes. He hooks a great fish – not just any fish, but the largest marlin the old man has ever seen. If only he had the boy, Santiago could bring this great fish in and change everything. But Santiago doesn’t have the boy. He has only himself.

old man and the sea

Santiago is a romantic:

“Fish,” he said, “I love you and respect you very much. But I will kill you dead before this day ends.”

But he’s also a realist:

“He is a great fish and I must convince him, he thought. I must never let him learn his strength nor what he could do if he made his run. If I were him I would put in everything now and go until something broke. But, thank God, they are not as intelligent as we who kill them; although they are more noble and more able.”

To me this passage carries all the weight and all the difference between The Old Man and the Sea, which I love, and Moby-Dick, which still haunts me. Santiago does what he does out of love of life, love of the sea and his part in it, love of the act of living. He realizes that the fish is neither good nor evil – the fish merely is. The fish’s strength comes with no malice, no evil intelligence, no conspiracy with the fates. The fish simply is. Nature simply is. Nature is indifferent to our suffering – and in the end, that in some sense makes nature even scarier, and makes our struggle that much sweeter. We bring meaning into this world. We depend on ourselves, our will, our intelligence, our ability to think through our pain, to overcome our adversity, to remain resolute in the face of defeat. We willingly take on the struggle that the indifferent universe poses. We choose.

By contrast, Ahab wants vengeance – vengeance on an animal that was only trying to defend itself. I’m still torn on the issue of how Melville characterizes Moby Dick. I believe, I think this is true, that Moby Dick is made a monster in the secondhand tales and hearsay, but in the actual flesh (remember we don’t meet the whale in person until the final three chapters of this long and complex book), Moby Dick seems like an animal – clever, yes, but hardly malicious, and graceful, like Santiago’s fish – until finally (out of, I believe, desperation to end the persecution) Moby Dick crushes himself against the Pequod, both sinking the boat and almost certainly killing himself.

If this is really Melville’s opinion of the whale, then Ahab is sadly deranged, and in an interesting way the mirror opposite of Santiago. Ahab sees evil intent where only indifference lies. Ahab, who comes so close to self-realization, self-actualization, self-choice, falls back on the ideas of fate and destiny, God and prophesy, and we as mere pawns in a game whose outcome is already decided. Melville refuses to choose. I simply can’t come to grips with this failure. It haunts me.

Santiago seems at first glance to fail nearly as completely as Ahab. Yes, Santiago does finally kill his fish (hope I didn’t give anything away there), but then the fish is devoured by sharks on the way back home. Santiago ends his journey with nothing but a skeleton, a boatful of ruined gear, and an old and devastated body. But Santiago has won. The boy, Manolin, upon spotting the great skeleton, upon seeing Santiago’s wrecked boat, upon finding the old man exhausted and starved, makes a choice. He will stay with the old man. He will fish with the old man. The old man will teach Manolin all he knows: about fishing; about life; about the struggle against indifferent nature, the struggle to know and test and experience our own selves. And what more could any of us ask for?

Santiago, a great fan of “the baseball” asks Manolin to “think of the great DiMaggio”. I say, think of the great Santiago.

Jacob Bronowski died when I was just six years old, soon after completing his 13-part series The Ascent of Man. I remember as a child seeing this series as VHS tapes on the library shelves. As this was in the days before VCRs became commonplace, I never took these tapes off the shelf. I didn’t know what I was missing.

Bronowski was an extraordinary human being. A mathematician, a poet, a biologist, a chess champion, and most of all an artist in words. I just finished his very short book, Science and Human Values.

Bronowski begins in Nagasaki, shortly after the destruction of that city by the plutonium bomb that finally convinced Japan to surrender and so end World War II. Bronowski asks if science has become a monster poised to break all our necks. He then proceeds to show how science, like art, reflects the fundamental problem of being human; that is, the struggle between individual and society, and the search for balance, a place where society functions as a collection of individuals.

The most moving parts for me reflect on my experiences as a teacher and a learner. Bronowski describes the act of creation, so similar in both science and art, where the artist and the scientist each discover a connection never before seen.

“The discoveries of science, the works of art are explorations – more, are explosions, of a hidden likeness.” – Jacob Bronowski, Science and Human Values

This explosion doesn’t end with the creator, however. The true beauty of art and of science is that the discovery is experienced again and again, as each individual encounters it. When I look at Michelangelo’s David, when I read of Einstein’s General Relativity, when I watch a performance of Macbeth, I experience the explosive joy of discovery first felt by the artist, the scientist, the writer. And when I, as a teacher, gently guide a learner toward these things, I experience again some of the joy of my own re-discovery. We each of us construct these things for ourselves, created anew within each individual – and, if we’re faithful to the true value of teaching, maybe even improved upon.

And this is the value that Bronowski so elegantly expresses in his book. We humans, individual beings forever separated from our fellows, are able to connect with one another through the common act, the human joy, of discovery, of creation, of progress.

There are only a few people I wish I could have known in my life. Jacob Bronowski is one of them.

Though he is gone, we can know him, at least a little. The Ascent of Man, that series I never watched as a child, is now readily available without even getting out of your chair. Here’s one excerpt about art and science. Enjoy.

I wrote a while ago about Darmok, one of my favorite Star Trek episodes (second only, I think, to the finale, “All Good Things”, though “The Inner Light” and “I, Borg” are awfully close). I’m writing about Darmok again for two reasons. One, in this week’s Cosmos Neil de Grasse Tyson told the story of Gilgamesh. That made me want to watch Darmok again. And two, there’s something I almost wrote last time, but didn’t quite make it there.


I know many people hate this episode. I know they say the premise is ridiculous. But here is where I think the critics are missing something crucial.


We are the Children of Tama. We understand the world through metaphor. This is precisely what Piaget says about how we learn. We build on our prior knowledge and experience to come up with new understanding.

When a child learns the concept of “dog”, a new structure is built in her brain. When, next, the child sees a cat, she may say “dog”, trying to make a connection to what she already knows. A cat is a dog. Metaphor! Later, the child expands her understanding to see that cat is a new category, something like dog, but different, as well. Metaphors are beautiful because of course they are only almost true.

This will sound crazy, but what if the aliens depicted in this episode actually don’t communicate through metaphor? What if it’s us? What if our brains are so different from theirs that the universal translator simply gives us everything in a form it thinks we might understand? Everything for us is so tied to metaphor – “The Tamarians are aliens, the metal contraption they ride in is a spaceship, the person in charge is their captain.” All of these are models we build in our minds to help us understand a never-before-experienced situation. Also, all are metaphors.

I mentioned the last time I wrote about Darmok my favorite scene, in which the Tamarian captain Dathon pidgins his own language to help Picard understand, and to communicate back to him. Now I have a close second. Near the end, as the new Tamarian captain receives Dathon’s log from Picard, he says “Picard and Dathon at El-Adril”.

Darmok Story

He’s just created a new metaphor! We’ve just witnessed the language grow. Note that this metaphor does not have the same meaning as “Darmok and Jilad at Tenagra.” Dathon died. This story has a new meaning – sacrifice for a noble cause.

So that blows my theory about we being the Children of Tama, right? No. Who is watching the show? Not the Tamarians. We are. Why? For the same reason we watch any program, or read any book, or listen to any song. Stories change us. We grow by adding metaphors. Over the course of this extraordinary episode, Dathon and Picard have taught us something: about life; about communication; about understanding, about sacrifice. Picard and Dathon at El-Adril. And we will never be the same.


I’m often reminded of the importance of teaching gently – usually when I’m on the receiving end of less-than-gentle teaching myself. It makes me want to explain (gently, of course) why such teaching is so destructive, and to redouble my own efforts to teach gently myself.

I remember myself in far too much less-than-gentle teaching. Science teachers are trained from the crib to hate and detest that most evil of memes, the misconception. I’ve been just as evangelical as anyone else at times. But I see the world differently now. Misconceptions are models of the world, and all our models are imperfect. We are always at the beginning of infinity.

Think about what that means! It means that every time we teach, of necessity we teach misconceptions. They are unavoidable, because all our knowledge is filled with them. Every time we teach, we are helping our learners to create castles of the mind, structures that never before existed, structures that are as unique and individual as each of our learners. This act of creation, imperfect and messy, is to be celebrated.

And sure, much of learning involves un-learning our misconceptions (and replacing them with better misconceptions). This is as true for the Kindergartner as it is for the practicing physicist.

Science teaching (and maybe all teaching, I’ll have to give that one some more thought) is all about metaphor. We link the unknown to the known, we build on existing (imperfect) knowledge. Too often, I think, the fear of misconception prevents the exploration of metaphor. Too often, metaphors are loaded down with caveats and equivocations. If all teachers would embrace the fact that no matter what they teach they are teaching misconceptions, and if we imbued our learners with this knowledge, and a deep skepticism as well, think of how far we might go.

Embrace misconception! It is the path to even better misconception.

Light is something the universe does.


I wanted to use that statement in an article I wrote a long time ago, but the editor didn’t allow it. What ever could I have meant by such an odd statement? Just this.

Light is ubiquitous. We know what happens when we enter a dark room and flip on a light switch. Suddenly (and it does seem to be sudden) objects in the room become visible. A flashlight can do something similar, and we can even direct the beam of the flashlight at particular objects and not at others.

I remember being puzzled by the car’s rearview mirror. I’d ask an adult what the mirror was for and learn that it gave a view behind and outside the car. Not from my vantage point, though. Apparently the light entering another’s eyes could be different than the light entering my own.

I also remember standing outside on a warm summer day, feeling the heat of the Sun on my face, my hands, my back. Light bulbs that had been on were hot to the touch, and a crayon positioned under a lamp would melt into a waxy puddle. Light could do things.

But what was it?

Another early memory is of my dad building for me an electromagnet from a battery and some wire. Pressing on the wire over the battery brought the wire into contact with the button at the top, completing the circuit and allowing the whole thing to pick up paper clips, screws, and so on. How was it that completing a circuit could turn wire and a battery into a magnet?

What I didn’t know was that every time I completed that circuit, I was sending electrons streaming along the wire, and those electrons were sniffing out the space all around. The way that electrons sniff involves spreading electric (if the electrons are still) or both electric and magnetic (if the electrons are moving) fields, and the ability to sniff in a particular medium (air, say, or water, or rubber, or anything else in the space) is called the permittivity (for electric fields) or permeability (for magnetic fields) of the medium.

What if there is no medium? What if the circuit is just surrounded by pure vacuum? Even here there is a permittivity, as well as a permeability. In fact, these are constants of nature, known as ε(read as epsilon zero, the permittivity constant) and µ(read as mu zero, the permeability constant). These values show up in the most interesting places; for instance εappears in the formula stating how strongly two electrically-charged objects feel each other when separated by some distance r:

\ F_C = \frac{1} {4 \pi \varepsilon_0} \frac{q_1 q_2} {r^2}

Meanwhile an analogous formula for magnetic field strength includes µ0


(Note that magnetic fields are about electric current I, while electric fields are about electric charge q, indicating that it’s moving electrons that cause magnetic effects).

What does all this have to do with light? Just this. Around 1861 Scottish physicist James Clerk (pronounced “Clark”) Maxwell was fiddling around with the equations for electric and magnetic fields. What happened next changed our understanding of the universe forever. Maxwell found that his equations predicted that electric and magnetic fields could propagate through empty space, one producing the other on and on. That propagation would take the form of a varying electric and magnetic field moving in a particular direction. The speed of that propagation came out as a constant number, dependent only on the electric and magnetic constants εand µ0.


Even more amazing, though, was the number Maxwell got when he plugged those numbers into the equation. The value of c came out suspiciously close to the measured value for the speed of light! Put the equations of electricity and magnetism together, and the speed of light comes flying out of your math, unbidden and unexpected, but undeniably there.

We now know that any time electrons jiggle, whether it’s in the radio transmitter of your cell phone, in the awesome accelerated motion of an x-ray machine, or even in the hot filament of a flashlight, the result is light. Some of that light you can see, like a small portion of the light from a hot light bulb filament. Much of it you can’t see, like the radio light flying away from your cell phone or the x-ray light bouncing off your dental fillings, or the infrared light that does much of the work in heating your face in the Sun or your crayons under a lamp. Yet every bit of it is light, an electrical and magnetic vibration in the very fabric of the universe.

Light is something the universe does.

It’s dark this morning, but I spot four figures in brightly-colored clothing already on the beach just to the south of the fishing pier. A little annoyed that anyone beat me to the beach, I decide to go north. As I get closer, though, I realize that what I thought were human figures were actually just tied-up beach umbrellas, left in place overnight. I change my mind and head south, instead.

I walk a long way in the darkness, watching the sand for movement. All I see are coquina clams – lots and lots of them. Whole beds of coquinas, washing along in the swash zone. As I watch them, I notice something peculiar.


The coquinas near my feet do the expected thing: when the surf rolls back, they dig into the sand and disappear. However, the coquinas further down the beach slope don’t dig themselves in. As I watch, these clams dig themselves out! In a moment I have a guess as to why.

It’s around 6:00 am. Low tide was around 4:00, so this is an incoming tide. Of course, I realize with a start. The coquinas can’t only dig in. If they did, they couldn’t move with the changing tides. Instead, they must dig in only when they reach the top of the swash zone, and dig out when lower. That lets the incoming wave wash them up the beach.

I watch a few more beds of coquinas to see if my guess matches with their behavior. Yes! Every time I see a bed of coquinas down low, they dig out of the sand as the wave recedes. Then, when those same coquinas get washed up higher by the next wave, they dig into the sand and disappear beneath my feet. Amazing.

Next I realize that this behavior must change as the tides change. They can’t only let themselves be washed up the beach. They must also let themselves be washed down the beach during a receding tide! On Friday, when I’ll be on the beach all day long, I’ll test this guess against reality.

Of course, I know this isn’t some great discovery. It’s almost just common sense, and I’m certain if I studied the literature on coquina clams and the swash zone this behavior will be well-known and well-studied. But to me, it’s a new discovery, deep, beautiful, and exciting.

Like all such discoveries, it suggests far more questions than answers. I wonder next, how to the clams do it? How do they know when to alter their behavior? How can they tell if the tide is swelling or receding? I can’t tell, not without the internet in my pocket (or at least a tide table). How do these tiny mollusks know?

Are they programmed to their specific beach? If I took coquinas from this beach and placed them on another with very different tide times, would they ever adjust? Or is their internal clock independent of outside influence? How could so much knowledge reside in this tiny shelled creature?

Mysteries are wonderful things; I can’t wait to explore this one some more.

This long barrier island just south of Clearwater Beach is relatively litter-free; even so, I do come across the occasional thoughtlessly-left bit of trash on the beach. Now I find a gall0n-sized zippered plastic bag, and I decide to grab it. Plastic bags are the mortal enemies of sea turtles, who eat them thinking they are jellyfish.

Humans are remarkable creatures, I think as I carry the wet bag up the beach toward a trash can. We’re capable with our brains and our technology of utterly transforming an environment, making it totally unsuitable for the natives. We are also the only creatures that try in any way to mitigate their impact. Maybe I just saved a sea turtle’s life.

I decide to sit on a bench just there and watch the ocean for a while. The Sun is coming up behind me now and the gulf is turning green. Such a lovely sight. I will miss this when I’m gone.


Later, I’m lying on a boat ramp into the Boca Ciega Bay, trying to get a picture of a shy fiddler crab. The crabs scurry into their holes on my approach, but if I sit very still, they will eventually forget about me and come out. I get them to reappear, but only then think to take a picture. My movement to get my phone out spooks them, and they disappear. I prepare to wait once again, this time with camera aimed. Unfortunately, those clouds in the picture above are moving west to east, and as soon as they hit the cool morning air over the land, the skies open up and the rain starts pouring down.

I’m not concerned about myself, as the rain is just cool enough to offset the heat of the rising Sun. But I am worried about my phone, so I head for some shelter. There’s a trash can there, and ironically inside is a plastic grocery bag. I pull it out – still clean – and wrap up my phone. Now I can head back out, and I’m excited to do so, because I know enough geometric optics to realize what’s coming next. The Sun is in the east, where the sky is clear. The rain is coming in from the west. I’m about to see a rainbow on the beach!

As I head down the nearest public access, there’s the rainbow. Beautiful, and I immediately start thinking what I always think when I see this marvel. Does understanding the rainbow really make it less beautiful? Of course not. I think again about the coquinas, and my “discovery” earlier that morning.

The first person to understand where a rainbow would appear in the sky must have gotten an enormous thrill, the same thrill I received from my coquina realization. And just as with my coquina discovery (as Richard Dawkins pointed out in his book on the subject), learning one truth about the rainbow didn’t just answer questions, it raised them. Studying rainbows led to the discovery of the true composition of light, its various wavelengths and frequencies. This led in time to the connection between frequency and energy, which in turn led directly to quantum mechanics, the structure of the atom and, eventually, to the age, size, and birth of the universe itself. Not bad.

Between all this reverie and the plastic bag protecting my phone from the rain, by the time I got a picture taken the rainbow was just about gone. Who knows, maybe it wouldn’t have shown up, anyway; I’m still very new at this whole photography thing. But even without a visible rainbow (trust me, it was there just in the left part of the shot), I still think I managed a pretty picture. What do you think?



(Yes, that’s a sea turtle nest – though not “my” nest, it’s further off to the left – in the center of the photo.)

Only two more beach walks, and then it’s back to landlocked Ohio. Oh, dear.

Yesterday, I wrote about why I teach, and how my reasons are not the reasons most teachers discuss. Their reasons are beautiful and moving, but they are not my own.

When I look at my own reasons to teach, however, I recognize that there are connections to more conventional reasons for teaching. I thought they were interesting:

1) I don’t want to change the world


The world is changing. The world is getting better – less violent, less polluted, smarter, healthier, more long-lived, and more conscious of the individual – and those changes owe a great deal to science and science education. Whether I want to or not, I believe that I do make the world better when I teach the values and principles of science.

2) I don’t believe I have a calling


I am the sum of my experiences. I have been influenced all my life by great teachers. I am carrying on their work through my own. Their ideas live on through me. That is maybe not a calling, but it is a connection that stretches beyond my own boundaries. Perhaps, if I am passionate and energetic and very lucky, I will inspire other teachers myself. And so it goes on.

3) I don’t believe in learning science because it’s important


The truth is that science is our only hope for survival. Life on Earth will someday come to an end, unless people with good explanations decide otherwise. By doing what I love, I perhaps can help the world survive.

Interesting. I’m happy that it works out that way – but it doesn’t change why I teach. When you’re in love, you want to tell the world.

Lots of people have lots of reasons for teaching. Some are so beautifully stated that they bring tears to my eyes. But as I read them I realize that none of them are me. Their reasons are not my reasons.

I don’t want to change the world. When I’m really honest with myself, I’m not interested in this world-changing business. Joseph Campbell said, “When we talk about settling the world’s problems, we’re barking up the wrong tree. The world is perfect. It’s a mess. It has always been a mess. We are not going to change it. Our job is to straighten out our own lives.”

And yet. Andyetandyetandyet. I love the starfish story. The star thrower isn’t trying to change the world. Yet we the readers recognize that she is changing the world, one starfish at a time. This to me is the essence of teaching. The world might be burning down, the barbarians might be pounding at the gate, but I, as a teacher, will stop, catch a breath, help that one student understand that algebra problem, show that one kid some amazing effect, give that one person one more experience they didn’t expect to have. Maybe it matters later, maybe it doesn’t. I don’t care. In that one moment, that moment of connection, that moment of shared effort for a common goal, there is beauty, and elegance, and poetry.

I don’t believe I have a calling. I believe we make our own destiny. I don’t believe I have a God-given gift, because I don’t believe in God. That’s more than an existential question for me, it’s a philosophy. I believe we create our own meaning. If I’m a good teacher, and I believe that I am, it’s because I’ve chosen to become so. I own my choice. In a powerful sense, my choice is me.

I don’t think people need to understand science. Again, Joseph Campbell – “Go on, live your life, it’s a good life, you don’t need this. I don’t believe in being interested in a subject because it’s said to be important or interesting. But, I believe, with the proper introduction, this subject may just catch you.” I believe science is a joy and a pleasure. Certainly it’s useful, but that’s incidental. And, incidentally, the usefulness comes down to joy and pleasure itself, if you follow it far enough. For what is life for, if not for joy and pleasure?  The process of learning, of building explanations, of building castles in my mind, and the process of building a world from bricks and metal are one and the same. If you disagree, well then, go on and live your life. Find your own passions. I’m not trying to change the world. Even if, along the way, I do.

Whitman said, “What good amid these, O me, O life? Answer. That you are here, that life exists, and identity; that the powerful play goes on and you will contribute a verse.” My verse is my work, my teaching, the starfish I’ve tossed and will continue to toss. Where do they go after I’ve tossed them? That I do not know, but in that moment of that connection, that act based on blind belief that one moment really does matter, therein you will find my story. Carl Sagan said it best. “When you’re in love, you want to tell the world.” I’m in love. And so I teach.

ln2 bubbles

Today I watched a little girl discover.

Her name was Gabby. She was maybe 2 years old. I was at my science museum job, watching tumbleweeds roll through the hallways (school is back in this week). There was Gabby, approaching an exhibit called the vortex. She saw the colorful balls under the table, grabbed one, and let it go. Her eyes lit up with wonder and delight, and she watched, transfixed by the motion of the ball around and around the table.

When the ball disappeared down one of the table’s two holes, Gabby reached under the table and grabbed another. This one she threw a little differently, and it bounced around before falling down a hole. Another ball, and this time Gabby tried to get closer, closer, by inching up on the table. That’s how I learned her name, as the adults with her told her, “Gabby, no.”

Undaunted, she tried approach after approach with the balls. One bounced off the table and away. “Uh oh,” Gabby said, then joyously chased down the bounce-bounce-bouncing ball. Again, Gabby tried to get closer, only to be rebuffed by her adults. I wanted to scream, “Let her explore!” but I held back.

Finally, the inevitable happened. The adults got bored. “Come on, Gabby, let’s go.” Gabby didn’t want to go. She was exploring, discovering amazing new things with each ball she rolled. What more could one want from a visit to the science museum? But the adults were insistent. “Gabby, now,” and Gabby, reluctantly, moved on. Later I saw her trying to crawl under the barrier to the Foucault Pendulum, then discovering, with that same joy, the model pendulum alongside it, swinging the ball around and around and around.

It was painfully beautiful to watch, and it reminded me of how the simplest things, if they’re real, if they’re true, are anything but boring when looked at the right way. And it reminded me to try, and try, and try so hard to remember what it was like to see the world through Gabby’s eyes.

I think I was Gabby’s starfish.

I love connections. To me, they are what learning and understanding are all about. Plus they’re really cool. For instance, yesterday I learned something cool and amazing about fish and swim bladders.

OK, a little background. I was reading something about discrepant events – you know, those science demonstrations that make you go, whoa! I believe they are the key to creating disequilibrium in learners’ minds, forcing them to accommodate their world views . . . I’m losing you, aren’t I?

Anyway, while reading a list of discrepant events to discuss with learners, I came across one item that struck me as just wrong. The author was claiming that a fish’s swim bladder is a discrepant event. Most learners will think that a fish adds air to its swim bladder in order to float higher. In fact, claims the author, just the opposite is true. The fish expels air to swim higher, because the vacuum created has less mass than the air. This struck me as almost certainly wrong, so I did some research.

Sure enough, the author was mistaken. Fish do add air to the swim bladders to increase their buoyancy. But . . . how?

Think about it for a moment and it’s a great puzzle. Fish can’t have had that air inside them to begin with (unless it was compressed, and I couldn’t see how a fish could be holding compressed air in). Do they “breathe” in a bunch of air very quickly to rise? This seems impractical, as often fish need to change their buoyancy quite quickly. So what do they do? We’ll come back to it.

Have you ever been exercising and felt that painful burning in your muscles? That good ache that lets you know you’re working hard? That pain is from lactic acid. When you exercise, your muscles burn lots of glucose by combining it with oxygen, thereby releasing its stored-up energy (energy that came from the Sun via photosynthesis of the plant that made the glucose, but that’s another connection story). However, if you run low on oxygen, your muscles start to convert glucose to lactic acid. This releases energy, too, but not as efficiently as the glucose plus oxygen reaction. And the side-effect is that the lactic acid starts to make your muscles ache as it turns the tissue acidic.

Fortunately, your body has a built-in defense mechanism against lactic acid damage. When tissue starts to turn acidic, the blood feeding that tissue becomes acidic, too. And when blood becomes more acidic, hemoglobin (red blood cells) start to release more dissolved oxygen. Oxygen, of course, is exactly what your muscles are screaming for, and so everyone is happy again.

Fish, with whom we share a common ancestor (we are, in fact, highly-modified, bicycle-riding fish – apologies to Gloria Steinem), have this same physiological response, but in fish the response is even stronger. Fish blood is extremely sensitive to changes in pH, so that a little lactic acid can cause a large release of oxygen. And fish use this response in an amazing way.

Lining the fish’s swim bladder are cells that are specially adapted to produce lactic acid. When they do, instantly the blood near these cells dumps lots and lots of dissolved oxygen. Much of that oxygen goes into the bladder as gas, and that gas makes the swim bladder expand. The fish carefully controls the amount of gas going into and out of the swim bladder so that as a whole the fish remains neutrally buoyant in the water. Lactic acid as a buoyancy control! Amazing!

But it gets even better. Why do we produce lactic acid at all? Because we all evolved from bacteria that used this method to eat! Before there was much free oxygen in the atmosphere (which, after all, came from plants), all the creatures on the Earth used this non-oxygen (anaerobic) method of eating. Many bacteria still do, of course, and they can be found anywhere food is abundant but oxygen is not. It was only when the plants “poisoned” the atmosphere with this volatile, fire-supporting waste gas that evolution found the more efficient pathway of burning glucose with oxygen to release energy. We might get annoyed at this scar of evolution every time our muscles start to ache, but for fish, it’s the very scar that keeps them afloat!

And that, dear readers, is what makes life cool.

My first book, called The Turtle and the Universe, was published by Prometheus Books in July 2008. You can read about it by clicking on the link above.
My second book, Atoms and Eve, is available as an e-book at Barnes and Noble. Click the link above. You can download the free nook e-reader by clicking the link below.
August 2020
A blog by Stephen Whitt

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 96 other followers