Store Is Closed
May 31 2011 1:33:00 pm ESTTopics:
Regarding flight, D’Arcy Wentworth Thompson expresses the unique requirements to remain aloft, and the effect these requirements have on the structure of an organism. From On Growth and Form:
The bird’s case is of peculiar interest. In running, walking or swimming, we consider the speed which an animal can attain, and the increase of speed which increasing size permits of. But in flight there is a certain necessary speed—a speed (relative to the air) which the bird must attain in order to maintain itself aloft, and which must increase as its size increases. It is highly probable, as Lanchester remarks, that Lilienthal met his untimely death (in August 1896) not so much from any intrinsic fault in the design or construction of his machine, but simply because his engine fell somewhat short of the power required to give the speed necessary for its stability (41).
Photo of the Day
May 31 2011 10:53:51 am ESTTopics:
An 1888 lenticular truss iron bridge, built by the Berlin Iron Bridge Co. that was donated by Washington County to the Town of Malta.
May 30 2011 3:15:38 pm EST
To my good fortune, I had an insightful kindergarten teacher. We made a personal time capsule to open at graduation. Forgetting about it completely, I was very much excited to happen upon it as a young adult.
I wasn’t sure what to do about the contents after I perused them. I decided to put everything away to read again; so it sat for a while.
After some time, I acquired things of interest: letters of gratitude from strangers, brilliant birthday cards, pictures, and other such novelties that I typically lose or throw away over time. Out of guilt, I put these things in the time capsule, lest they be lost forever.
Over time, I accumulated quite a collection of memories, and I had to transfer the contents from an envelope, to a box. I decided not to open the box until I reach a ten year mark in my life. In other words, the next time I’ll open the box is 30, then, 40, 50, and so on.
Every time I add things to the box, I wonder about the things I forgot. I look forward to op
May 30 2011 11:51:43 am ESTTopics:
Walking and running has evolved to generate as much thrust as possible while using the least amount of energy. The process of human walking recovers approximately sixty per cent of the energy used due to pendulum dynamics and ground reaction force. However, the legs are not simple straight poles that swing uniformly like the pendulum in a clock; a leg swings and thrusts at the hip, knee, ankle, and toes, utilizing a dizzying array of muscles, ligaments, tendons, bones, and other tissues.
Looking at a human gait cycle, it consist of 60% stance, 40% swing. In other words, the leg spends more time thrusting than it does swinging forward to the next step. Yet one foot has to always be in contact with the ground. In order to maximize thrust while minimizing swing time, the leg is extended while it is in contact with the ground, while the various levers are contract
May 29 2011 12:43:36 pm ESTTopics:
Giovanni Alfonso Borelli (1608-1679) was a Renaissance Italian physiologist, physicist, and mathematician. He was a pioneer in the field of biomechanics, publishing De Motu Animalium I and De Motu Animalium II, which explored the mechanical nature of biological systems.
D’Arcy Wentworth Thompson frequently sites Borelli’s work, and explores an interesting phenomenon in which a similarly constructed organism, regardless of size, will jump to the same height. In other words, a flea and a grasshopper, despite their differences in size, end up jumping to the same height. Consider the following passage in On Growth and Form (36-37):
Such problems as that presented by the flea’s jumping powers, though essentially physiological in their nature, have their interest for us here: because a steady, progressive diminution of activity with increasing s
Heat loss in an organism is proportional to the surface area, or the square of its linear dimensions; the larger the surface area, the greater the heat loss. If the tissues of all homeotherms were to generate heat uniformly, the overall generation of heat would be proportional to the mass of the organism, or the cube of its linear dimensions. In other words, the larger the organism, the more tissue to generate heat, and the more heat generated overall.
However, this is not the case. Smaller mammals must overcome the effects of a larger surface area by generating more heat per unit of mass. Consider the following passage in On Growth and Form:
The tissues of one mammal are much like those of another. We can hardly imagine the muscles of a small mammal to produce more heat (caeteris paribus) than those of a large ; and we begin to wonder whether it be not nervous excitation, rather than quality of muscular
May 21 2011 1:43:20 pm ESTTopics:
Unlike land animals, aquatic animals evolve under different constraints. The crushing weight of gravity is counterpoised by the buoyancy of the water. A neutrally buoyant organism is effected differently by increasing mass.
The available energy for an organism depends on its mass, or the cube of its linear dimensions, while the resistance to motion is opposed not by gravity, but by skin-friction against the water, which varies with the square of its linear dimensions.
However, the rate of supply of kinetic energy depends on the surface area of the lung. In other words, the rate of work tends to vary with the square of the linear dimensions.
Under these constraints, the muscles are able to exert a force proportional to the cube of the linear dimensions, while the supply of energy is proportional to the surface area of the lungs or the square of the linear dimensions.
Consider the following passage in On Growth and Form (30-33):
...As Galileo also saw,
May 19 2011 12:14:03 pm EST
I am in the May 19th edition of Spotlight News for My Travels with Eos.
If, ten years ago, I could look into the future, and only see the title of the article published about me in Spotlight News: ‘Living with Aliens,” I might have submitted myself to a mental institution…
However, if I was able to actually read the article, I would probably have been pretty happy, though I would probably consult a psychologist…
In any case, the article was well written and covered all the bases pretty well. Thank you Alyssa Jung and Spotlight News for featuring me.
Click image to view hi-rez jpeg of article:
May 19 2011 11:18:14 am ESTTopics:
It’s a cold an lonely world without a star to orbit, and recent observations indicate that there may be twice as many orphaned planets than there are stars in the galaxy.
From Scientific American: Two astronomical collaborations report in the May 19 Nature that they have located a population of 10 celestial objects, each with about the mass of Jupiter, with no detectable host star. By extrapolation, the study’s authors, from the Microlensing Observations in Astrophysics (MOA) collaboration and the Optical Gravitational Lensing Experiment (OGLE) collaboration, calculate that there should be almost twice as many such objects in the Milky Way as there are stars. Some of the newfound objects may simply orbit a star at a distance so great that their host star is not apparent, but the researchers estimate that most of them are indeed free-floating.
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