There are few pleasures in life that exceed the simple joy of devouring home-cooked pancakes on a Sunday afternoon. I’m not much of a cook, but brunch is by far my favorite meal. So I decided that it’s time to take matters into my own hands, and improve my pancake making skills. Oddly enough, the first job I ever had as a college freshman was as a breakfast chef in my dorm. Back then, I’d make pancakes from a box, using Aunt Jemima’s pancake mix. I’ve since realized that it’s not much harder to make pancakes from scratch, and it’s a whole lot more gratifying. The quest for the perfect pancake is something of a lifelong journey. But unlike other boring journeys, this one is delicious, and served with syrup. Mmmm.

So where do we begin? I favor buttermilk pancakes myself, for their light and fluffy texture. If you go online and look for recipes, you’ll find plenty that claim to be the BEST buttermilk pancakes. Are these recipes really all that different? What sets them apart? And what’s the essence of a truly excellent buttermilk pancake?

Like any scientist worth their salt (sorry), I decided to answer this question with a graph. After all, the whole is just the interaction of its parts. So let’s take apart what the web thinks of as the perfect pancake.

Above, I plotted the ingredients that go into a buttermilk pancake, according to eight highly rated online recipes. I normalized the recipes so that they all have the same amount of flour. You’ll see that there are certain essentials that you just don’t mess with. You definitely need one egg for every cup of flour. And there isn’t much variation in how much salt or baking soda you put in. On the other hand, these recipes vary widely in how much butter or sugar they include. Presumably, the excellence of a pancake is less sensitive to variations in these other ingredients. But which recipe do you follow? What’s a good empiricist to do?

I decided to take the average of these recipes, and build a pancake that strikes a balance between the excesses of its online progenitors. In so doing, I’m following the idea behind Jeff Porter’s ‘Eigen Pancakes’, from Cooking for Geeks.

So here are the ingredients for my eigen-pancakes. The quantities turned out fairly close to this trustworthy recipe from Serious Eats. And it tastes pretty darn good. But don’t take my word for it, try it out yourself.

Dry ingredients:

• 2 cups flour
• 2 tablespoons of sugar
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• 1 teaspoon salt

Wet ingredients:

• 2 cups buttermilk
• 2 eggs
• 4 tablespoons of butter (melted)

And here’s the recipe:

1. Combine the dry ingredients in a large bowl.
2. In a separate bowl, whisk together the wet ingredients
3. Pre-heat a griddle over medium heat. If you flick water onto the surface and it sizzles, it’s ready.
4. Pour the wet ingredients into the dry mix. Stir until just combined. There should be lumps in the mixture. Resist the temptation to over stir.
5. Butter the pan very lightly, and scoop the batter on to the griddle. Once bubbles form, carefully flip the pancakes. Cook until golden brown.

With a little practice, this recipe makes a reliably delicious stack of pancakes.

I like playing with my food, and prodding beneath the surface. One aspect of cooking that’s always bothered me is the seeming arbitrariness of recipes. What do the various ingredients do, and why do we need them all? In a way, every recipe hides a story of reactions that create new flavors and textures.

So here’s the science behind your breakfast. A pancake is the result of a pretty incredible transformation. The magic begins when you mix the flour with the wet stuff. If you look through a microscope, flour contains two different kinds of proteins called glutenin and gliadin. When moistened and mixed, these proteins link together to form a sticky molecular mesh known as gluten. Next, you need to add a leavening agent. This is something that fills the gluten with air. Without it, leavened breads like cakes, muffins and loaves of breads would be pretty inedible.

Traditionally, people used biological agents like yeast for this purpose. The yeast munches on sugars, and excretes carbon dioxide, making thousands of little air pockets in the gluten. Put the dough in the oven, and these air pockets expand. The gluten transforms from a gooey, sticky mess into a dry and spongy substance that we call bread.

But yeast is slow to act, and so we rely on a quick chemical reaction instead. Baking soda is really an alkaline powder called sodium bicarbonate – it’s a base. Buttermilk is acidic (hence the sour, tart taste). Mix the two together, and the laws of high school chemistry tell you that you’re going to get salt, water and carbon dioxide gas. These are the bubbles that rise up as you stir the batter. You’ll want to quickly cook your pancakes, so as not to lose these precious bubbles.

This reactions works because buttermilk is acidic. Regular milk isn’t. So if you were making pancakes with milk, you’d want to use baking powder instead, which is baking soda with a powdered acid in the mix. When dry, the mixture is completely inert. Add water, and the two compounds react to give out bubbles. No acid necessary.

Modern baking powders are double acting, which means they give out a second round of bubbles when heated, thanks to an additional acid that is activated by heating. This helps the overworked chef, because you don’t have to cook the batter immediately after mixing. It also makes for fluffier bread. But it’s not a good idea to rely on the second round of bubbles. You can see why in this picture.

Now comes the most complex and interesting part of the process. This is the Maillard Reaction, and it’s the step that gives pancakes their aroma, and that gorgeous golden brown colour. When you raise the heat on your pancake mix, the amino acids that make up the proteins begin to chemically bond with carbon and oxygen atoms from sugars. The end result is a complex brew of hundreds of different aromatic flavor inducing molecules, that give your food a distinctive and rich palette of flavors. The Maillard reaction is behind the bold flavor of roasted coffee, the malty flavor of certain beers and malt whiskey, that brown crust on a perfectly cooked steak, the nutty notes of maple syrup, or the delightful aroma of freshly baked bread.

What’s more, the Maillard Reaction works best in an alkaline environment (i.e. a less acidic one). So the secret to getting that golden brown color is to add more baking soda. Once you’ve added enough to neutralize the acidity of the buttermilk, anything left over will add to the browning.

That sounds a little weird – how can a totally white powder help a pancake turn brown? See for yourself. Here are five batches of pancakes made with a cup of flour and all the usual ingredients, including baking powder as a leavening agent. They’re identical, except for one tiny difference. The pancake on the left has no baking soda. Every successive pancake has 1/8th of a teaspoon more baking soda, all the way up to a full half teaspoon on the right. Seems like a small change, but take a look at the effect.

In the words of  J. Kenji Lopez-Alt, a MIT graduate and chef who conducted this experiment:

The pancake all the way on the left is inordinately acidic, due to the un-neutralized buttermilk. It cooked up pale and bland. It was also under-risen with a flat, dense texture. The one all the way on the right, with a full half teaspoon of baking powder had the opposite problem. It browned far too quickly, lending it an acrid burnt flavor tinged with the soapy chemical aftertaste of unneutralized baking soda. Interestingly enough, this pancake was also flat and dense—the inordinate amount of baking soda reacts too violently when mixed into the batter. The carbon dioxide bubbles inflate too rapidly, and like an overfilled balloon, the pancake “pops,” becoming dense and flaccid as it cooks.

The best pancake was the one right in the center with 1/4 teaspoon of baking soda. It cooked to a beautiful golden brown with a tender, well-risen crumb and had a clean buttermilk flavor.

And there you have it, science being put to use to answer one of the big questions in life: what’s for breakfast?

Buttermilk Pancake References:

I learnt all my pancake science from this excellent writeup by J. Kenji Lopez-Alt at Serious Eats. Here’s the recipe to go along with it.

I also enjoyed this post by Carolyn Tepolt, a Biology PhD student at Stanford who blogs about food science.

And this post by sprinklefingers is quite interesting and has some helpful tips.

If you’re unfamiliar with Open Lab, it’s an annual print compilation of some of the best science writing on the web. Scientific American books has agreed to publish this edition, and it will hit bookstores sometime next fall. The editors Jennifer Oullette and Bora Zivkovic faced the daunting task of winnowing down 720 submissions to 51 finalists. The complete list of their selections is available here, and you can read about their selection criteria in Jennifer’s wonderful defense of the blogging form.

I’m incredibly humbled to be included, especially along such a star studded blogging cast. I’m stunned that I’ll be sharing a book with some of the names on that list. I started this blog less than a year ago, because I couldn’t quite contain my excitement about science. This selection means that I must be doing something right!

But it means more than that. The online science writing community is a group of crazily passionate people. They have families and busy day jobs. Yet they manage to find the time to build something beautiful, something they care deeply about. It’s an incredible meritocracy where the biggest names tirelessly plug the work of the newcomers. The only thing that matters is that what you create is interesting.

My blogging has slowed down to a standstill of late. But rather than offer a lame excuse about being busy, I’m instead going to take inspiration from my fusion powered blogparents. Everyone’s busy. Regardless, I’m going to strive to work harder, to stay up later, and most importantly, to stay interesting. And of course, I won’t forget to have a lot of fun along the way.

P.S. I WON I WON I WON I WON…

Watching these bees through my camera lens, I could see something quite interesting. As they landed on the flowers, they would kick up grains of pollen that would rise up like dust. And then the bees would do something quite odd – they would fiddle with their knees. I zoomed in to see what was going on.

There’s something quite peculiar about this photograph. What’s that fleshy appendage stuck to the knees of the honeybee? It looks, to me, somewhat like a human ear. And even stranger – the bees don’t have it when they arrive on the flower. But in a few minutes this thing begins to grow, and in about 15 minutes it’s as engorged as you see in the picture.

In addition to collecting nectar from flowers, honey bees also collect pollen. And what you’re seeing in these photographs is an incredible adaptation that helps bees go about their business of collection. It’s called a pollen basket, and here is how it works.

Bees are hairy creatures, and they get covered in pollen. They rake themselves clean with combs that are built into the inner surfaces of their hind legs. Next, they move all this collected pollen to a joint between the segments of their legs – their knees. This joint functions as a pollen press, and it squeezes the pollen into handy little pellets. But these pellets need to be stored somehow. And so, here is the next adaptation. The outer surface of the hind leg is concave, and it is covered in many small hairs. It’s a basket! This is where the bees store these compressed pollen pellets, and that’s what you see in the above picture. The basket is actually transparent, and so the fleshy color in the pictures above is the color of pollen.

The weird thing about this is that the basket is open at the bottom. So why doesn’t the pollen fall out? That’s because there’s a single strong hair that prevents this from happening, which functions as the lid of the basket.

Although I couldn’t quite make out the details, watching this elaborate packing process through the zoom lens was quite mesmerizing and I was merrily snapping away. The bees didn’t seem to notice me at all, but I realized that I was getting odd looks from my neighbors, so I decided it was time to take my leave.

Update: Added discussion on launch angle at the end of the post.

Edit: The final numbers in this post went through a few rounds of revision. What is the world coming to, when you have to track down missing factors of 2 in your blog posts?!

This week, I’m looking at the strategies and mechanisms by which different animals solve the problem of getting around. I started off by writing about how birds and aquatic animals conserve energy on-the-go. This post is another spinoff on the theme of locomotion.

Here’s a clip from one of my favorite documentaries, David Attenborough’s Life of Mammals. It shows the incredible sifaka lemur of Madagascar, a primate that has a really remarkable way of getting around. (If the embed doesn’t work, you can watch it here)

As they launch out from the trees, they almost look like they’re defying gravity. And so, taking inspiration from Dot Physics, I thought it might be interesting to put physics to use and analyze the flight of the sifaka.

I loaded the above video into Tracker, a handy open source video analysis software. I can then use Tracker to plot the motion of the sifaka. I chose to analyze the jump at about 21 seconds in. I like this shot because it isn’t in slow motion (that messes up the physics), the camera is perfectly still (we expect no less from Attenborough’s crew), and the lemur is leaping in the plane of the camera (there are no skewed perspective issues that would be a pain to deal with). The whole jump lasts under a second, but at 30 frames per second, there should be plenty of data points.

This is what it looks like when you track the sifaka’s motion:

The red dots are the position of the sifaka at every frame. That’s the data. In order to analyze it, we need to set a scale on the video. I drew this yellow line as a reference for 1 unit of size (call it 1 sifaka long). And how big is that?

If we believe this picture that I found on the National Geographic website, then a sifaka is about half the size of this folded arms dude.

Now, to the physics..

While the sifaka flies through the air, the only force acting on it is gravity, which points downwards. So the acceleration of the lemur should also be downwards. (I’m ignoring air resistance. We’ll find out if this is a good idea.)

If we plot its horizontal motion, it should be moving at a fixed speed, with no acceleration. But its vertical motion will give away its acceleration.

This is what we get if we plot at the horizontal position of all the points with respect to time.

The squares are the data points, and the line is a plot of the equation of a straight line

I was amazed by how well they agree, since I expected air resistance to matter a little more. I guess ignoring air resistance is a pretty good approximation.

We find that there’s a straight line relationship between position and time, which implies that the sifaka moves at a constant speed in the horizontal direction. The slope of this line () has units of meters/second (or in our case sifaka/second) and is the speed of the sifaka.

What about the vertical direction? Well, it certainly can’t be a straight line relationship with time, because at some point the sifaka turns and comes back down. Here is what the plot looks like:

The small squares are the vertical positions of the dots plotted versus time, and the red curve is the plot of an equation for a parabola

Here is the vertical launch speed, is acceleration, and is time.

So, over time, the vertical position traces out a parabola, which is a characteristic shape for motion under a fixed acceleration (in this case, the earth is accelerating the lemur downwards). The nice thing about analyzing motion is that we can analyze the horizontal and vertical motion independently of each other.

The fit to the parabola is not great, but it’s not too shabby either. I suspect the main reason for the discrepancy is that its hard to track the center of mass of the sifaka, and if you choose any other place on the sifaka, you’ll also be tracking the spin of the sifaka about its center of mass.

By solving for the values of , and that best match the data, we get the launch speed and acceleration of the lemur.

To be a little more empirical about things, I did this analysis twice, and averaged the results. Here’s what I got:

Horizontal launch speed:
Vertical launch speed:
Vertical acceleration:

The negative sign on the acceleration indicates that gravity is pulling the sifaka downwards  (in the negative y direction). So far things look good qualitatively, but do the numbers work out?

Well, according to National Geographic, the tail of a sifaka monkey is 46 cm, whereas according to wikipedia it is 50 to 60 cm. Let’s go with 50 cm on average. The length scale I drew in Tracker is about the length of the Sifaka’s tail. So we can set 1 sifaka = 0.5 meters.

That gives us a value of for the acceleration caused by gravity, which is within 16% of the known result of . I think that’s pretty darn good for a first stab at video analysis, especially as the sifaka was a blur in each frame and often obscured by trees.

Next, we can use Pythagoras’ theorem in the above velocity triangle to solve for the total launch speed

where and are the horizontal and vertical components of velocity.

This gives a launch speed of 4.25 meters per second or 9.5 miles per hour (15.3 km/h). This speed sounds reasonable to me, as it’s about how fast your typical bicycle moves. If we include a fudge factor that fixes our acceleration to the known result, then the launch speed is actually faster by 16%.

Update: added discussion on launch angle.

We can also solve for the launch angle of the sifaka, by using some high-school trigonometry on the triangle:

Solving for the angle gives 34.7 degrees.

Is this angle correct? Fortunately, Tracker has a handy built in protractor, so we can check it. Marking out the initial leap for both runs, I get an average launch angle of 34.5 degrees.

Which agrees to within half a percent of our result inferred from the physics!! Eerily accurate..

It’s a bit of a coincidence that the result is as close as it is, given the many possible sources of error. However, one reason why this result is so accurate is that the angle comes from a ratio , and so common sources of error (such as error in estimating the length of a sifaka) end up cancelling out. This is also why physicists prefer to measure ratios, rather than numbers that have units (they call such quantities dimensionless).

And there you have it folks, SCIENCE being put to use to answer the burning questions that keep you up at night.

If you want to read more about how the sifakas glide, Darren Naish has a detailed post describing research on the physics of this.

It’s a gorgeous shot on aesthetic grounds. Perfect lighting and composition, a beautiful subject, and a strikingly dramatic moment. And seen another way, it’s a metaphor for what Empirical Zeal is all about: diving beneath the surface, and looking at things from a different point of view.

It turns out that this photograph is a neat illustration of two interesting physical phenomena. Can you guess what they are? And here’s another (admittedly odd) question. Can we use this photograph to work out the density of this woman?

(Answers below the fold)

Well, the first principle that this photo demonstrates is the idea of buoyancy. Objects that are submerged in a fluid (in this case water) experience a force that helps them float. Why does this happen? Imagine that instead of the woman, you had a woman shaped hole in the water. The water would try to rush in and fill the cavity. So even when the woman is underwater, the water is constantly pushing against her.

Mostly, she doesn’t feel this because the pushes cancel out. The water is pushing her to the left just as much as it is to the right, and she moves neither left nor right. But here’s the kicker – the water under the woman is at a slightly higher pressure than the water above her (water pressure increases with depth). In other words, the water below her is pushing harder than the water above her. The net result is an upwards force provided by the water, and this is called the buoyant force.

If this buoyant force of the water matches her weight, then she will float. If her weight exceeds it, she will sink. That’s why rocks sink, and beach balls don’t.

But how can we workout her density? To do this we need to recall two things from high school physics.

1. The weight of an object is its mass multiplied by g = 9.8 N/kg
2. The buoyant force is equal to the weight of the fluid displaced by the object (in this case the weight of water that the lady has pushed out of her way)

And now we can start cooking. The first thing you do in any physics problem is draw a picture.

We see that there are two force acting on the woman. The first force is her weight, pulling her down.

We can then rewrite this as

where is her density, and is her volume.

The second force is the buoyant force, which is given by the weight of water that she displaces.

where is the mass of water displaced by the lady (the shaded region in the above figure)

Like before, we can write this in terms of density, so that

where  is the density of water and  is the volume of the lady that is submerged in water.

Now, for the woman to remain stationary as she is in the photograph, the two forces must balance each other out:

or

Rearranging this equation gives us the density of the lady:

Happily, the answer doesn’t depend on her shape. It also doesn’t depend on the value of gravitational acceleration , which means that if you were to repeat this photo shoot on a lake on the moon, it would look essentially the same.

In words, this equation tells us that the density of the lady is the density of water multiplied by the percentage of the lady that is submerged underwater.

The photo was taken in a place called Weeki Wachi Springs in Florida, so this must be fresh water, whose density is 1 kilogram per liter. Looking at the picture, it seems like only half her head is above the water. Assuming that a head takes up 10% of the body’s volume, this means that 95% of the lady is submerged. So her density is 95% that of water, or 0.95 kilograms per liter.

If we wanted, we could also work out her mass. To do this we need to estimate her volume. I have no idea what this is, but it’s a number between 50 and 100 litres. Her mass is then her density (0.95 kg/L) multiplied by her volume.

The second physics principle in this photograph comes from the field of optics. If you look at the surface of the water, you can see that it behaves like a mirror, reflecting the light from her dress. Water is usually transparent, so why is it reflecting light?

What’s going on here is a phenomenon known as total internal reflection. This happens because light rays bend outwards as they go from water to air. Depending on the angle, some rays can make it out, while others are trapped and they bounce back.

You can see this happen if you stand underwater in clear water and look up. You’ll be able to see the sky inside a circle above your head, but outside that circle, the rest of the water surface becomes a mirror, reflecting whatever is under it.

And so, here we are. We’ve dissected a beautiful photograph and arrived at some grotesque caricatures. While they may not be much to look at, they represent  conceptual shifts in our understanding of the world. And we enrich our world by getting to know them better.

What comes next is utterly surprising. Take a look at the video:

It looks like a dangerous situation, but these geese appear to be in control.

Seemingly effortlessly, they glide over to center of the river and catch the wave. They have incredible skill and control as they guide themselves right into the wave, while facing backwards. And they manage to surf it without being swept over. It looks like they are making a determined effort to stay there. You can even watch one of the geese that doesn’t quite make it, and it starts flapping its wings to get further upstream.

I did some cursory googling around, and I couldn’t find an example of this behavior being documented before. So what I’d like to know is, what is going on here? Are they in any real danger here? Maybe they are trying not to get separated from the young ones in the rapid, by collecting together at surfable waves. Or perhaps by surfing a wave, they can catch fish that are being swept up in the backflow. My friend Deepak pointed out that fly fisherman often fish near rapids, so there might be something to this idea.

However, I don’t see them feeding in this video. And if they judged a wave to be truly threatening, I would imagine that they could just as easily try to swim out of the way, or fly over it (although this may pose a new set of problems.)

But there is another explanation for their behavior, one that’s harder to verify empirically. Maybe, just maybe, what you are seeing are these geese having fun.

It could be that they’re just enjoying playing in the wave. And in doing so, they’re teaching the kayakers a thing or two about their sport.

What do you think is going on in the video? I’m curious to know. Post your thoughts in the comments below.

While looking around for interesting Arduino projects, I came across this incredible video via Make magazine. It’s an episode from a show hosted by Sylvia, a 9 year-old tinkerer and Arduino hacker.