Why do I get cold when I get out of the pool?

Sonny boy is taking swimming lessons again. His lips turn purple when he gets out of the pool, and he is sometimes unable to stop shivering. So, yesterday, he asked me "why do I get cold when I get out of the pool?"

Good question.

First of all, as you all know that water on your skin is evaporated away into the dry air. For water to change phase from liquid to gas requires input of energy (this is called the latent heat of vaporization). If your body is covered in water and the vapor pressure of water in the atmosphere is low enough, the water will want to evaporate. The evaporation requires heat input. The film of water on your body draws that heat from...your body, primarily. The air is, of course, another source, but most of the heat required to change the water to gas comes from your body.

Water has a latent of vaporization of 2441 kJ/kg at 25 degrees Celsius (by the way, centigrade is a meaningless term. There are no degrees centigrade.).

Let's say that a 6-year-old with a height of about 137 cm (4.5 feet for you weirdos) and a weight of about 25 kg (55 pounds...) has a volume of about 25 liters (average human density is about 1010 kg/m^3). Now, as all good physicists do, let's approximate this 6-year-old as a sphere with a volume of 25 liters. That gives us a surface area of .4 m^2 and a radius of 18 cm. Let's assume that there is a 1 mm layer of water on this spherical child. That's a volume of 409 milliliters or .409 kg.

It takes approximately 1000 joules to cause the phase change of this water. A completely unmeasured guess at how quickly Sonny lost heat is that he was shivering within a few seconds of exiting the pool. He had more than 1 mm of water on him, most of which was dried off with a towel. So, let's say he lost about 1000 joules in about 30 seconds. That's about 120kJ joules per hour.

This article talks about heat loss in sedentary people at various temperatures. The average heat loss due to evaporation was about 62 kJ/m^2/hour. Corrected for Son's surface area of 0.4 m^2, we get 300 kJ/m^2/hour, or about five times the sedentary rate of cooling.

You are more likely to lose body temperature (due to evaporation) in a warm, dry place such as AZ than in a cool, wet place like WA. The relative humidity in Flagstaff, AZ in June in the morning is 54% and 21% in the afternoon, but is 83% and 53%, respectively in Seattle. This is why it's easier to get heat exhaustion from 80 degree temperatures in Atlanta (84% and 56% in June) than from 110 degrees in Tucson, AZ (32% and 13% in June); your sweat isn't as effective at removing heat from your body because it's more difficult for it to evaporate.

Wind will cause what's called "forced convection" in which heat is whisked away by the movement of the air around your body (it's more complicated, but that's for another day, perhaps).

So, is there any way to stop kiddo from having purple lips and looking like a goth at 6? Not really. If the pool area had higher humidity, that would slow the evaporation, but people would probably complain about it. Similarly for keeping the pool area warmer (this would allow more heat to come from the air rather than the body). The best way is to dry the kid off as quickly as possible.

Why do dalmations have spots?

This was from Son's Highlight's magazine, but it's an interesting question to me because it involves evolution, though not exactly as Darwin imagined it nor exactly as it works over eons to produce humans from mice. As you read this, remember that I am not a biologist.

Basically, because people like the genetic mutation that make some dalmations spotted, people breed spotted dalmations more than dalmations with splotches. Aside: Of course, such inbreeding eventually leads to excessive genetic problems. In the case of dalmations, "purebreds" are very likely to experience the dog equivalent of kidney stones.

So, what does this have to do with evolution. This is basically microevolution.

In this case, we have a particular genetic mutation (spots vs. splotchs) and a particular desire for spots by would-be purchasers, the "environmental stress" is effected by the breeders choosing to breed only those dogs with desirable spot patterns. Over time, in the population of dalmations that are bred in this way, there will be fewer and fewer dalmations born with splotchs rather than spots.

This is a very simplified example of evolution, with a million problems. Get over it. Evolution is fact.

I've been somewhat combative in my recent posts, including this one. I should (and do) apologize to you few loyal readers.

Paper Money

This is a rant.

The conversation went something like this:

Son: "Dad, we should stop buying things because they cut down trees to make money."

Dad (thinking): "Damn straight. We should stop buying things for that and many, many other reasons."

Dad (saying): "Well, we usually spend money through computers, so we don't use very much paper money. But, you're right, we should not buy as much as we do."

The point is that my six-year-old son is more concerned about the future of his planet that the morons who are ruining it. And, while I usually directly relate childishness with big businesses and their cronies in DC, this time it seems even a child has more forethought. "Go shopping" indeed.

So, now that we allowed eight years of obstructionism by the big energy lobby and short-sightedness by the rest of the Senate during Clinton's administration and eight years of head-in-the-sand myopia by the Bush administration, we've got less than ten years to decrease our CO2 production by 80%. Ten years, and we haven't even begun to agree on its necessity.

"I'm sorry, son. We thought it was more important that people be able to continue shopping like they always have."

I want to end this post on a higher note, so I'm linking to a blogger who is doing her little bit by writing to her congresscritters.

Livestock as Industry: No Way To Make it Work

I've been reading a lot about various global climate change causes and implications recently because I've been asked to talk to a local high school chemistry class about energy and sustainability. Most of what I want to talk about I can't because of time limitations. I'm going to rant here instead.

In looking at dust storm activity in the US Southwest, I came across this paper (PDF).

It discusses the impacts of multi-decadal grazing on soil properties in southeast Utah. Basically, the point is that over-grazing does a few things to the soil:

1. It destroys the cyanobacteria, lichens, and mosses in the upper part of the soil. This causes loss of nitrogen in the soil. As you all know, nitrogen fixing is necessary for the generation of proteins and DNA, and is therefore necessary for life. When the nitrogen fixing stops, the soil loses its life-sustaining capabilities. Nitrogen levels in the grazed soils vs. the ungrazed soils was 60-70% less.
   
2. Carbon, another essential ingredient for life is decreased by 60-70% as well.
3. The loss of life on these soils allows wind erosion to increase dramatically, which reduces the amount of Mg, Na, P, and Mn by 14-51% (different for the different elements).
4. Silts are decreased by 38-43%.

Basically, nutrients of all kinds are lost from these grazed lands. It's been 30 years since the last cow was grazed there, and the lands have not recovered; cyanobacteria takes at least 100 years to recover.

What does this mean for climate change? Well, for one, the loss of nutrients to erosion makes the drylands of Utah more sensitive to small variations in moisture variability. What was once considered a dry spell will be a drought. Higher sensitivity to rainfall will also quickly cause decreases in plant life. Plants, bacteria, mosses, lichen, etc. are what keep the nutrients available to...feed life. A decrease in one causes a positive feedback loop that eventually causes a loss of both.

What happens once the plant life is mostly gone? Winds remove the nutrients. You get massive dust storms as seen here. So, what? It's just a little wind, it's not like that has ever hurt anyone.









































So what happens is you get this:

Aww... The poor skiiers have to ski on dirty snow. So, what?

Dirty snow is darker snow. Darker snow absorbs more sunlight and melts earlier. Early melting of snow can have many affects, but most importantly, it changes the timing of when meltwater is available to downstream plants and animals. If the plants are not yet ready to receive the water, they'll die off.

Here's a great article on how changing climate and specifically changing of timing in the climate affects creatures in differing ways. Go read it now. I'll wait. Seriously. Go!



Basically, it turns out that some plants and animals time their various activities based on temperature while others time their activities on available sunlight. So, some creatures/plants will peak earlier than they used to while their migratory predators show up late to the party because their sunlight- or other time-based clocks are out of sync with the climate.

Early meltwater running (and necessarily less on-time meltwater) will dramatically affect the creatures that depend on it and the creatures that depend on them, and the creatures that depend on... ad nauseum.

So, can't they just evolve to deal with it? Sure, if they have several tens of thousands of years.

This is the entire problem with human-induced climate change. Things are changing too quickly for most life to adapt. Sure, eventually it'll figure itself out, with likely only a few surviving species and a few new, unrecognizable species, but it's going to be a bleak, bleak place if we don't get our heads out of our asses soon.

2 degrees C of warming is going to push us to the tipping point with no room for error after that; we have less than a decade to figure that out and to do something about it.

What does all of this have to do with livestock? They're unsustainable. The only way eating beef makes sense is if you own 80 or 100 acres of grassland (that's nowhere in the southwest--those are not grasslands, they're drylands.) and have a single cow and calf. Then, it still doesn't make sense to eat the cow when you can get dairy from it. Eating beef from large (in number of head) ranches doesn't make sense at all, whether they're grassfed or cornfed. Grazing livestock (beef) in the way we've been doing for the last 100 years or so is simply not sustainable and it is killing the drylands of the mid- and southwest.

How far can a Dandelion Spore Travel?

When I arrived home from work, my son was raiding the dandelions in the back yard. He was doing what we all did at six: blowing the spores off and making a wish when he cleared the stem. Of course I joined him. After watching the spores float around the yard, he asked me how far can one of them go.

Happily, the intertubes were not too clogged that evening and I managed to find a few research articles on this very subject (yay, Google Scholar!). I have the sneaking suspicion that the scientists who do this work are just looking for excuses to lay on the grass making wishes with their children. Here's a likely manuscript title (Tackenberg et al): "Dandelion Seed Dispersal: The Horizontal Wind Speed Does Not Matter for Long-Distance Dispersal - it is Updraft!" The conclusion in this paper is that for a dandelion seed to go 100 meters or more (long distance by their definition), updraft is the dominant factor. In slight contrast, some (PDF, Stephenson et al.) other (Greene) authors report that the wind speed required to remove similar seeds from the stalk is an important factor. The Stephenson article also considers 100 meters to be a long distance for seeds to travel, so while I suspect that some 4- or 5-sigma seeds can travel into the upper troposphere and thus very long distances it seems that most seeds of this type only travel 100 meters or so.

I had expected that the seeds would make it further than that.

Merck, Elsevier and Dishonesty in Science

The drug giant Merck and the publishing giant Elsevier apparently colluded to defraud the public by publishing a fake journal that only contained "articles" that were summaries of or full "papers" that cast Merck in a positive light.

I don't think there's much that can be said that hasn't already.

I'll be doing my best not to publish in any Elsevier journal from now on; I don't know if I can avoid it (they're everywhere), but...ugh. What disgusting behavior.

Why you Should be Concerned but Should not Panic About A(H1/N1) (Swine Flu).

The western media are at it again, pushing the panic and the apathy buttons all at once.

Here are some informed, well-written, intelligible discussions on what the WHO was calling swine flu and is now calling A(H1/N1):

1) Interview with the US CDC virus chief.
2) Explanation of the WHO's pandemic scale
3) More intelligent discussion of the epidemic
4) Science Insider look at the activity of health agencies around the world

What should you do?

Stop reading or listening to NBC, CBS, CNN, etc. Seriously.

Start reading the posts on the CDC's site:
http://www.cdc.gov/h1n1flu/index.htm

the WHO's site:
http://www.who.int/csr/disease/swineflu/en/index.html

The US government site set up just for this:
http://www.pandemicflu.gov/

Seriously, stop using the major cable and broadcast agencies for news; they're for entertainment, not news.

Here are some reasons for concern:
1) This particular strain has not been seen in humans. Therefore, no humans have built an immunity (although there may be unexpected sources of an immunity in random people). There are many reasons this lack of immunity would not cause every infected person to die.
2) The spread of this virus is faster than we've seen before.
3) In the US, if this does go pandemic (which seems to be the expectation), we don't have the health care infrastructure to handle a lot of sick people all at once.
4) H1N1 has started migrating between humans. If it is or becomes efficient enough in transferring, we may be too far behind the curve to do more than mitigate its effects.
5) Relatively young, healthy people are succumbing to this. Usually only the elderly, the already ill, and the very young die from influenza.
6) The people most likely to get sick (low income workers, part-time workers, and mothers of school-aged children, etc.) are also the least likely to have any paid sick-leave. Therefore, they're the most likely to continue to go to work (and send their children to school) even if they are sick. Guess who is at the very bottom of the paid sick leave ladder...food service workers.


Here are some reasons for hope:
1) Cleanliness is the best prevention, and cleanliness is easy.
2) The CDC in the US and the WHO and its member states are as aware and on top of this as they can be.
3) Most cases outside of Mexico have been relatively mild. It's not clear why.

Some Dos and Don'ts:
Do:
Wash thoroughly; keep clean.
Stay home if you feel sick.
Stock up at least two weeks worth of food and water. Seriously.
Make sure your prescriptions have recently been filled.
Make sure you are stocked on other medications.
Learn how you can help in a public health emergency. Contact your local/county/state health agency if you think you might have anything at all to contribute.

Don't:
Don't listen to Joe Biden.
Don't panic about pork. If you like pork, cook it well and eat it.
Don't rush out to buy antibacterials. Influenza is a virus, antibacterials won't do anything to stop it.
Don't panic. Prepare.