Wednesday, August 18, 2010

More poop Mommy; I'm hungry!

A few years ago, a cousin of mine told me the story of the time she was at a public swimming pool (in Utah, I believe) when her infant son demanded to be fed. She did what came naturally: she began to breastfeed her son. This act didn't go over very well with at least one of the pool's patrons, who came over to my cousin and sneered "That's disgusting! I have young children and they don't need to see that!" My cousin mused on how curious it was that this lady wasn't bothered by her children seeing dozens of women and girls of various ages walking around the pool in scant string coverings, but a mother breastfeeding her infant was disgusting. (For the record, The Science Pundit is okay with both breastfeeding mothers and scantily string-clad bathers.)

What is or isn't disgusting is a matter of subjective opinion, but breastfeeding--or more generally, lactation--is a natural process for all mammals. Many animals don't care for their young, but those that do have evolved a variety of strategies for feeding and protecting their progeny. Lactation is the strategy that mammals have evolved for that purpose. The "most primitive" mammals, the monotremes such as the duck billed platypus, give us a clue as to how lactation might have evolved. Suckling probably started as young proto-mammals liking their mother's skin to gain moisture and nutrients from the oils and perspiration exuded from the pores. Something similar to this (but more evolved) is seen today in the platypus. The most highly developed lactators (by which I mean the most developed mammary glands) are the placental mammals (which includes we humans). The milk we feed our youngest contains not only nutrients, but antibodies to help with immunity development. I wouldn't dream of calling this disgusting.

When I think disgusting, I think of something that promotes the gag reflex, in other words: puking. This brings me to the next strategy for feeding one's young. The simplest and most obvious strategy is for the parents to go get food and put it into their offspring's mouth. This strategy is also practiced by many species of mammal during a period known as weaning. This strategy does have some shortcomings, though.

For one, it can be quite cumbersome carrying around food. Also, infants or hatchlings often need time for their digestive systems to fully develop, particularly if the animal relies on gut microbes to help digest its food. So what could be a good way for a mother or father to help its young digest food, while introducing beneficial microbes to its system, and making the journey easier? If you're thinking of vomitting, then you get a cigar (which curiously enough creates a smoke which triggers the gag reflex in some people). Personally, I think that when it comes to disgusting, regurgitation beats breastfeeding hands down.

So do we have a champion? Not by a long shot. Let's not forget that there is another way for the body to release nutrients which is intimately tied to the digestive system. I am of course speaking of excrement.
Eating excreta is a time honored tradition in the animal kingdom. The most famous coprophages are green fly larvae and the esteemed dung beetle. And some animals even eat their own droppings. Rabbits, for example, unlike their grass eating cousins the ungulates, have only one stomach and so can't adequately digest their meals in a single pass. Bugs is left with little choice but to consume his own cecotropes.

But is there an animal out there that actually craps out a partially digested meal to feed its young? Behold Ctenocephalides felis, the common cat flea!

The cat flea is the most common flea found biting pets and people. Even though there is a dog flea (Ctenocephalides canis) and human flea (Pulex irritans), the fleas you are most likely to find sucking away human or canine blood are cat fleas. So let's talk a little about our friend's life cycle.

Let's get a couple things clear. The male cat flea is a blood sucking and pooping machine (as evidenced in the picture to the left EDIT: The flea in the picture is female; thanks Christine.), and the female cat flea is a blood sucking, egg laying, and pooping machine. Adult fleas are constantly shedding eggs and doodies. The flea dingleberries naturaly outnumber the eggs since (a) only females lay eggs, and (b) the nutrition required to produce a single egg results in several berries. It is also worth noting that female fleas will lay eggs even if they haven't mated, and mated females will lay non-viable as well as viable eggs.

While adult fleas have hooked barbs on their feet and legs to keep them attached to their host (not to mention mouth parts), eggs and scat don't avail of such adhesives. So what happens is that eggs and turds drop off the animal with the largest concentration (as statistically expected) falling off where the pet spends most of its time. The viable eggs then hatch into worm like larvae, a good proportion of which will find themselves surrounded by huevos and caca. This is a veritable smorgasbord for the larvae since that is what they eat.

ResearchBlogging.orgIt seems that the larval diet shifts from primarily feeding on stools in the first stage to actively seeking out eggs and sucking out their yolks in the third. I suppose that this is an improvement since being told to go suck an egg isn't quite as insulting as being told to eat shit. But this raises the interesting question: are fleas not only blood suckers and shit eater, but also cannibals? As long as you don't consider eating non-viable eggs as cannibalism, it seems the answer is yes, but they keep it to a minimum. There is some evidence that non-viable eggs are stickier than viable eggs and so easier for a larva to latch on to, but I think that the primary explanation is one of statistics. Viable eggs hang out for a limited period of just a few days, while non-viable eggs hang around until either they're eaten or sucked up by the pet owner's vacuum cleaner (I was taught that if you have fleas, you should put moth balls in your vacuum cleaner bag. That makes sense now.)

So which is the more important part of the flea larva diet: eggs or droppings? That's the question Drs. Hsu, Hsu, and Wu looked into back in 2002. The flea larvae were divided into five groups based on diet. The MF group was fed exclusively adult male feces. The FF group was fed exclusively adult female feces. The NE group was fed exclusively non-viable eggs. The FF+NE group was fed a mix of adult female feces and non-viable eggs. And the control group PBCP group was fed exclusively porcine blood curd product (The Science Pundit hereby renames the control group "bacon eaters"). There were thirty larvae in each group, which is large enough to see patterns, but The Science Pundit (that's me) would like to see a larger more comprehensive study. The FF+NE and bacon eaters both did fairly well with 90% & 83% survival to adulthood, respectively. The MF group did a bit more poorly with a 13% survival rate, but both the FF and NE groups were completely wiped out.

I guess the lesson here is that if you're a cat flea larva you should eat shit and suck eggs, but if you can only do one, then eat your daddy's poop.

Hsu, M., Hsu, Y., & Wu, W. (2002). Consumption of flea faeces and eggs by larvae of the cat flea, Ctenocephalides felis Medical and Veterinary Entomology, 16 (4), 445-447 DOI: 10.1046/j.1365-2915.2002.00388.x

Tuesday, August 17, 2010

Guerrilla Cinema

I've been a fan of guerrilla theatre for quite a while now. The very idea of an acting troupe showing up unexpected (and often uninvited) to a public location to do a surprise performance for their unsuspecting audience is both clever and intriguing. Seeing a performance live is even better. After the initial surprise, it's lots of fun and turns into something you'll remember.

However, up until I saw the clip below, I had never heard of it being done for cinema. The trailer below is absolutely brilliant! The plot seems mundane and ordinary enough, but it's not really the plot that makes it so great. I have to wonder how long they were able to record each scene before getting kicked out (or did they?). I would imagine that they probably rehearsed the scenes to death, then went on location and tried to shoot each scene in a single take (unless something went wrong--like getting kicked out). Obviously the bed scene was done in multiple takes since they're in different beds with practically every change in camera angle. I don't know whether that was intentional or the result of being constantly chased out by management, but either way: Bravo!

Saturday, May 29, 2010

Wednesday, May 26, 2010

Roy Zimmerman house concert

Last night my sister Lali and I went to the Roy Zimmerman house concert at the lovely home of Freethought Society president Margaret Downey. I have to give Margaret a thousand thanks for putting on such a wonderful event. The accomodations were great and Roy was fantastic. He played mostly songs from his new album Real American, many of which I was hearing for the first time. He certainly hasn't lost his touch. I think that songs like The Orange County Rolling Acres Senior Center Cannabis Club and Buddy, Can You Spare a Trillion Dollars? will be fan favorites for years to come. And of course he played several of his classics; his final encore was Defenders of Marriage, which he nailed. If you're unfamiliar with the song, here it is

After the show, we got a chance to sit around and have a conversation with Roy about politics, his music, freethinkers, and other topics. I again must thank Margaret for being such a gracious host. It was really nice. And we even got to pose with Roy for a couple of pictures.

As you can see, we're all wearing our towels (if you remember from yesterday's post, it was Towel Day). Roy was quite tickled to finally meet a couple of the people involved the collaboration video covering his song Creation Science 101 (see Roy sing it here)

Our part begins at around 1:12 and we sing the line "which means they must have been incestuous". Roy appreciated the joke, but I must confess that I am not in fact incestuous--although that will come as a shock to all of my family members that I've hit on. (For those of you who've never seen Roy play live before, he will often introduce one of his songs with the joke "I'm not gay, although that will come as a shock to several members of the audience who I've been hitting on.")

Anyway, the concert was great and if you ever get a chance to see Roy Zimmerman perform, do it!

Tuesday, May 25, 2010

Happy Towel Day!

Happy Towel Day everyone!

Last night I went to see Roy Zimmerman perform and tonight I will be going again with my sister Lali. The shows are sponsored by the Freethought Society. Full report to follow tomorrow.

Friday, April 16, 2010

Air friction myths

1. Drag

Ever since I was a young kid, I remember people telling me how air friction slows objects moving through the atmosphere. The problem with this claim is that it's wrong. Well, technically it's partially right: there is a friction force at play and it does have a slowing effect. The thing is that the effect of air friction is so negligible compared to what is really slowing moving objects down that it can safely be ignored in just about all cases. The claim that air friction is what slows moving objects down is akin to saying that the recoil of a rifle is due to the backward force of your finger upon the trigger.

So what is this force that really slows flying objects? It is called aerodynamic drag. When I correct people about this, I often hear the excuse that when they say air friction, that's just shorthand for aerodynamic drag. I don't buy it! Air friction exists and is quite distinct from drag. So what exactly is aerodynamic drag? I shall attempt to explain it here.

A moving object displaces air as it moves through its gaseous medium. In other words, it pushes air out of the spot where it's going and leaves emptiness in the spot where it has been. Air immediately rushes in to fill the void left behind the moving object in much the same way that air or liquid rushes to fill the vacuum within a syringe when you pull back on the plunger. Of course it takes time for this void to fill in and reach equilibrium with the surrounding air. This leaves a region—called the slipstream—of relatively low pressure behind the moving object. The farther from the moving object within the slipstream, the more air which has been replenished and the closer to equilibrium with the atmosphere that it is. Naturally, the faster an object is moving, the larger the size and lower the pressure of its slipstream.

The pressure difference between the air in front of a moving object and the air behind it creates a force upon the object that is against the direction of motion. The faster the object is moving, the stronger this force is (in fact, the force is proportional to the square of the velocity of the object). This repulsive force is what is known as aerodynamic drag.

Racers know about aerodynamic drag and are able to use it to their advantage. Drafting is the technique where a racer will move into the slipstream of another racer in order to lessen the pressure difference between fore and aft, therefore lowering the drag force resulting in energy savings for the racer.

So the next time somebody tries to tell you that flying objects are slowed down due to air friction, be sure to correct them and tell them all about aerodynamic drag.

2. Shock

A very bright meteor was recently captured on video out in the mid-west. Greg Laden pointed out how the CNN report of the event said that air friction caused the meteor to heat up. This reminded me of the old Tom Glazer/Dottie Evans song What is a Shooting Star?

A shooting star is not a star, is not a star at all.
A shooting star's a meteor that's heading for a fall.

A shooting star is not a star; why does it shine so bright?
The friction as it falls through air produces heat and light.

You might recognize this song from the cover version by They Might Be Giants on their recent album Here Comes Science. Unfortunately, the last time that TMBG covered a Tom Glazer/Dottie Evans song, they picked one with a major scientific inaccuracy.

The sun is a mass of incandescent gas,
A gigantic nuclear furnace.

They were forced to write a new song (titled Why Does The Sun Really Shine?) to correct the falsehood.

The sun is a miasma of incandescent plasma,
The sun's not simply made out of gas. No, no, no!

So will TMBG need to write a new retraction song about why a meteorite really gets hot and bright? Alas, I'm afraid that they will. Once again, air friction exists and does indeed produce heat, but is so negligible that it can be ignored. In fact, at subsonic speeds, the dominant heat exchange effect on (warmer than air) objects is wind chill. Warmer than air objects radiate heat into the surrounding air creating an insulating "blanket" around them slowing heat loss. But if the object and the surrounding air are moving relative to each other, then this layer of warm air is stripped away causing the object to radiate heat faster, ergo the familiar chilling effect. However, at supersonic speeds, a new effect comes into play.


As an object moves through the air, it displaces the air in its path by pushing it forward and aside. The air moves away from the object as a series of compression waves (similar to the waves that a boat creates as it moves through the water). Now if you remember back to science class, you'll know that compression waves have another name: sound. So what happens when the object is moving faster than the speed of sound? Aha!

What happens is that the air gets pushed forward and aside faster than it can naturally escape. As long as the object is moving slower than sound, the compression waves outrace it and take most of their energy with them. But at supersonic speeds, the air keeps getting compressed and compressed and compressed as the object pushes it forward faster than the air can get away. So similarly to the freon in a refrigerator's compressor or the fuel mixture in the cylinder of a diesel engine, the leading air gets superheated by the crushing force of the supersonic object.

Basically, the supersonic object creates its own oven by compressing the air in front of it. Furthermore, if the object is made of an oxidizable material (such as iron, aluminum, or carbon) and the air is oxygen rich (such as the earth's atmosphere), then the object may quite literally burn up.

So the next time somebody tries to tell you that air friction causes a meteorite to burn up in the atmosphere, be sure to correct them and tell them all about supersonic shock.

Sunday, April 04, 2010

Happy Zombie Day!

Simon Pegg (star and cowriter of Shaun Of The Dead) has written an interesting article delving into the debate between slow zombies and fast zombies. As expected, he takes the side of slow zombies--"Zombies don't run!" he opines--and I must agree with him. The fast zombies just aren't as scary as the traditional ones. If zombies can run and jump, what makes them unique? How are they different from other movie monsters? It's that slow, plodding, neverending approach of rotting corpses that makes zombies so creepy and scary.

Pegg brings up all these points in his essay, but he also raises one that I hadn't really thought of before: the zombie as metaphor for death.

Where their pointy-toothed cousins are all about sex and bestial savagery, the zombie trumps all by personifying our deepest fear: death. Zombies are our destiny writ large. Slow and steady in their approach, weak, clumsy, often absurd, the zombie relentlessly closes in, unstoppable, intractable.

However (and herein lies the sublime artfulness of the slow zombie), their ineptitude actually makes them avoidable, at least for a while. If you're careful, if you keep your wits about you, you can stave them off, even outstrip them - much as we strive to outstrip death. Drink less, cut out red meat, exercise, practice safe sex; these are our shotguns, our cricket bats, our farmhouses, our shopping malls. However, none of these things fully insulates us from the creeping dread that something so witless, so elemental may yet catch us unawares - the drunk driver, the cancer sleeping in the double helix, the legless ghoul dragging itself through the darkness towards our ankles.

Exactly right! And that only begins to scratch the surface of why the metaphor is perfect. This is also why the zombies must always win in the end. You can cheat death--for a while--but the horde of walking dead have time on their side. And those trying to cheat death damn well know it!

Enjoy Zombie Day by watching some good zombie movies. You owe it to yourself.

Saturday, March 20, 2010

Friday, February 12, 2010

Happy Darwin Day!

And if you happen to live in Broward County FLA, here's something you can do tomorrow to celebrate.