Sharks!

My good friend Mr. Dylan McKeever recently posted a comment regarding SHARKS. Now, as any real child will tell you, sharks can smell a drop of blood from miles away (you'll be able to spot the nerds--they'll say that sharks can detect "one part per million"). Sharks possess nature's most deadly nostrils, but it gets better. Just like our ears can detect the general location of a sound source, i.e. you turn your head when you hear your name called from over there, sharks' "nares" (noses) can do the same. They have STEREO smell!

Let's consider stereoscopic sensing for a second. We can see in 3D because of our brain's understanding of the differences between the two images received from our two eyes. We hear in stereo because our ears are spaced six or so inches apart and rotated away from each other, which leads to slightly different sounds entering each ear. Now let's pretend I just received a new boombox for Christmas. If I place the two speakers right next to each other, the sound all seems to come from one place, and all the instruments seem squashed together, packed into a narrow corridor of sound. But if I space them twenty feet apart from each other, it sounds like the band is spread out really wide! It's easy to tell where each instrument is coming from within the stereo "image." NOW, lets apply this concept to our favorite swim team mascot, the Hammerhead Shark. What at first seems like merely a good aesthetic decision becomes a hell of a tool. Because the nares are spread to the tips of the hammer (up to a meter wide), they create a more pronounced image of the smell, and they are able to track their prey with great accuracy. Don't you wish you could smell in stereo?!

ACTIVITY: Hammerhead Kids
"Smell in Stereo!"

materials:
bike helmet
wooden dowel, 1 meter long
aquarium filter tubing ~1.5 meters
electrical tape

1. Attach wooden dowel to bike helmet using electrical tape

2. Cut aquarium tubing in half, attach the end of each half to the ends of the dowel, tape thoroughly

3. Insert free ends of tubing into nostrils.

4. Explore your new world!

First In a Series: The Seven African Powers

Name: The Seven African Powers

Cost: 50 cents for 22 sticks
Verdict: B+

As Xmas approaches lets not forget that two out of three of the original gifts were smells. Frankincense and Myrrh are two sappy resins and the main ingredient of certain high-quality perfumes and incense. In Ancient Rome, Myrrh was worth more than its weight in gold (it can now be found in mouthwash and "gargles"). Although I would like to review these two luxury scents, I don't have the means. But I won't let simple poverty stop me from giving the gift of smell!

I crossed the street to my neighborhood 99 cent store and picked up a box of "The Seven African Powers" incense. The purple bilingual package features an image of Jesus on the cross, surrounded by seven catholic patron saints. A smorgasbord of symbolic imagery is littered at his feet, although I could only make out a few of the more prominent items including a spear, a ladder balanced on air, and a chicken on a pedestal.

The sticks are a brilliant purple color, matching the box. In the bag, they smell soapy, crisp, and clean. Once lit, the burning wood combines with the aromatics to form a surprisingly palatable log-cabin-fireplace meets old-man's-aftershave blend. The ash takes forever to drop and ends up in a Chinese snake banana. It leaves a nice little aftersmell: when I left the room and came back a few minutes later I was pleasantly surprised. It is certainly not of highest quality, but an inoffensive incense is rare in itself and it is a bang for the buck. B+.

The Speed of Smell

We all remember Hippolyte Fizeau's famous 1849 speed-of-light experiment from sixth-grade science lessons. Through some byzantine combination of a mirror, a cigarette lighter, and a zoetrope he calculated that light must travel at 313,000 kilometers per second, remarkably close to the accepted measurement of 299,792.458 kmps. William Derham calculated the speed of sound in the early 1700's using a shotgun and a stopwatch (343 meters per second). But smells seem to be difficult measurement subjects. Children's television host Bill Nye attempts to explain:

The speed with which a smell travels depends on how fast the molecules are going, how massive they are, the relative temperature of the molecules making the smell, and how many molecules there are in a given volume, their density. We express all this mathematically as a gas's temperature and pressure.

Not good enough, Mr. Nye! I want numbers! PSI's vs. FPS's PDQ! Over at Yahoo Answers we find a more convincing explanation:

Smells are just chemicals. The speed that chemicals diffuse in the air is predicted by Graham's Law when you compare two gases.

Use oxygen as your standard gas.

The ratio of the speed of diffusion on the smell compared to oxygen is equal to the square root of the inverse of the mass of the oxygen molecule divided by the mass of the molecule of the smell.

The molecule of sulfur has 8 atoms of sulfur in each molecule, oxygen has two atoms per molecule. The mass of sulfur is 32 and oxygen is 16. The mass of their respective molecules are 8x32 and 2x16 or 256 and 32. Take the ratio of the two, oxygen over sulfur is 32/ 256 or 2^5/2^8 or 1/8. Take the square root of 1/8 is 0.354.
smell is about 1/3rd of the average speed of the molecules of oxygen in the air.
the speed of smell is smell is about 1/3rd of the average speed of the molecules of oxygen in the air.

YES! I'm generally willing to hedge my bets on the reliability of Yahoo Answers, typos and all, but what is the average speed of oxygen molecules in the air? I traipsed over to http://www.newton.dep.anl.gov to investigate:

There's a really neat mathematical equation based on a theorem called the "equipartition theorem" which states that the energy of a gas system (equal to 1/2*mv^2) is equal to the temperature of the gas (equal to 3/2*kT). If we rewrite this equation to solve for velocity we get:

sqrt(3*T*k/m) = v

where T is the temperature in Kelvin, k is the Boltzman constant = 1.3805*10^-23 J/K and m is the mass of the gas particle.

If we assume that the average mass of air (since it is a mixture of different gases) is 28.9 g/mol (or each gas particle is around 4.799*10^-26), and room-temperature is 27C or 300K, we find that the average velocity of a single air particle is around 500 m/s or 1100 miles per hour!

So, if we take a 27° C room (a balmy 80.6° Fahrenheit), with air molecules moving at 500 m/s, the smell of a rotten egg travels at 166.66 meters a second! Is that FAST or WHAT!