Think Ahead

Posted on August 9, 2009 by swansont

Yes, because people do the wrong analysis.

The authors give a simple example of how this could play out: Imagine two routes to a destination, a short but narrow bridge and a longer but wider highway. Let’s also imagine that the combined travel times of all the drivers is shortest if half take the bridge and half take the highway. But because each driver is selfishly trying to seek the shortest route for himself, this doesn’t happen. At first, everyone will go for the bridge because it’s shorter. But then, as the bridge becomes backed up, more drivers start taking the highway, until the congestion on the bridge starts to clear up. At that point more drivers go back to the bridge, which then becomes backed up again. Eventually, the traffic flow settles into what’s called the Nash equilibrium (named for the beautifully minded mathematician), in which each route takes the same amount of time. But in this equilibrium the travel time is actually longer than the average time it would take if half of the drivers took each route.

Note that this still happens even if – indeed, especially if – all the drivers have perfect information about what all the other drivers are doing, such as with a GPS that gives real-time traffic updates.

The problem here is similar to the one of feedback, as anyone who has designed and tested gain/feedback circuitry can attest. There is an oscillation to the signal — an ebb and flow of traffic density. There is a delay in the time between the signal and the feedback, and at some point the delay is 180º out of phase, so you add to the problem rather than subtracting from it.

Note that the last quoted sentence is actually incorrect — the real-time traffic update information tells you where traffic is, not where it is going. If you knew that a lot of drivers were heading to the bridge and would be there in 15 minutes — about when you would arrive — you wouldn’t take the bridge. But all you know is how many are on the bridge right now. The information you are missing is how many drivers have made the decision to use the bridge.

Death to Exponential Growth

Posted on August 7, 2009 by swansont

Your body wasn’t built to last: a lesson from human mortality rates

What do you think are the odds that you will die during the next year? Try to put a number to it — 1 in 100? 1 in 10,000? Whatever it is, it will be twice as large 8 years from now.

This startling fact was first noticed by the British actuary Benjamin Gompertz in 1825 and is now called the “Gompertz Law of human mortality.” Your probability of dying during a given year doubles every 8 years. For me, a 25-year-old American, the probability of dying during the next year is a fairly miniscule 0.03% — about 1 in 3,000. When I’m 33 it will be about 1 in 1,500, when I’m 42 it will be about 1 in 750, and so on. By the time I reach age 100 (and I do plan on it) the probability of living to 101 will only be about 50%. This is seriously fast growth — my mortality rate is increasing exponentially with age.

This is News?

Posted on August 6, 2009 by swansont

Tyrannosaurus rex ‘picked on baby dinosaurs and ate them whole’

Research into the predatory habits and diet of the biggest of the dinosaurs has concluded that T.rex and other members of its carnivorous theropod family preferred to dine on juveniles, preferably small enough to eat whole.

It shatters the notion that the giant battled with animals of a similar or even larger size, an image reinforced by its portrayal in Steven Spielberg’s 1993 film Jurassic Park.

Really? Jurassic Park, a work of fiction wherein the T. rex never battled anything of similar, much less larger, size? And why would anyone expect T. rex to behave any differently than modern carnivores, who prey on the young and weak? Certainly not the researchers:

Dr Hone, who works at the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, said: “Modern predators mainly attack vulnerable, young animals as they are inexperienced in evading predators, and this was probably the same in dinosaurs. Young prey are easier to bring down and the risk of injury to the predator is much lower.

Eye of Newt and Toe of Frog

Posted on August 6, 2009 by swansont

Ingredients: What’s in the stuff we buy?

A project started by the question, “Why is there salt in my shampoo?”

There are thousands of chemical compounds in the ingredients lists of products we buy every day. Knowing what each one is doing in the product has obvious benefits in comparison-shopping. However, it also provides a sneaky way of teaching simple chemistry to people who had no idea they would find it so interesting. I am always looking for ways to make science more interesting to people who think it is only for people who use masking tape on their eyeglasses.

Here’s part of an example —

Sodium benzoate is used in acidic foods and products to control bacteria, mold, yeasts, and other microbes. It interferes with their ability to make energy.

Because it only converts to benzoic acid in acidic environments, it is not used for its anti-microbial action unless the pH is below about 3.6. In the food industry, it is used in items such as jams, salad dressing, juices, pickles, and carbonated drinks.

One Other Thing

Posted on July 31, 2009 by swansont

… about the new camera. It’s not just a (high speed) video camera, it also takes stills, though it doesn’t do all the things that an SLR does.

damselfly

This is a damselfly, which are related to dragonflies. The main difference to my eye (not being a biologist) is wings open vs. closed when resting. There are other differences, too, though rectal tracheal gills was a phrase I didn’t need to see. Oops. Spoiler alert.

A great, or at least pretty good, blue heron.

blueheron

A monarch butterfly and caterpillar

before-and-after

Some bug on Queen Anne’s Lace
bug-1224

Putting Your Thermoregulation Where Your Mouth Is

Posted on July 24, 2009 by swansont

Toucan Beak Is New Kind of ‘Heating Bill’

[U]sing infrared thermography, a type of temperature-sensing video originally developed by the U.S. military, scientists have tracked the pattern of heat distribution across the toucan’s body under changing outside temperatures. When the bird got too hot, it released heat by sending blood to its highly vascular but uninsulated beak. In cooler weather, the toucan constricted blood vessels in its beak to conserve heat and stay warm.

On the Case

Posted on July 20, 2009 by swansont

Cocktail Party Physics: NEW VOICES: georgie boy

Dr. Cheadle has never heard of vitamins. Their discovery is decades in the future. But he understands that diet is the issue here, although many colleagues disagree. Dr. Cheadle argues in his 1878 paper against the various other theories about scurvy, including that it is caused by humid and/or cold climates, excess salt in the diet, lack of exercise, and ptomaine poisoning. “There is, however, an invariable factor, without the presence of which all other casual and irregular factors are powerless to set up the disease. This essential factor, it has been proved over and over again, is the absence of certain elements in food. If the body is deprived of these elements, [scurvy] is produced. What these elements are has not yet been absolutely settled with scientific precision, but we know positively that they exist in fresh vegetables, in lime-juice, in milk, and in less considerable degree, perhaps, in some other fresh animal foods.”

Pass Me the *@#%ing Aspirin

Posted on July 14, 2009 by swansont

Or acetylsalicylic acid, generic. You can get six hundred tablets of that for the same price as three hundred of a name brand.

Why the #$%! Do We Swear? For Pain Relief

Although cursing is notoriously decried in the public debate, researchers are now beginning to question the idea that the phenomenon is all bad. “Swearing is such a common response to pain that there has to be an underlying reason why we do it,” says psychologist Richard Stephens of Keele University in England, who led the study. And indeed, the findings point to one possible benefit: “I would advise people, if they hurt themselves, to swear,” he adds.

Not clear to me how swearing differs from just yelling something random, though.

There is a catch, though: The more we swear, the less emotionally potent the words become, Stephens cautions. And without emotion, all that is left of a swearword is the word itself, unlikely to soothe anyone’s pain.

Oh, shit.