speed

toc Read here about speed and its importance to studies of scale.

=Overview= Speed is the ratio of a length span to a time span.

=Units= Speed is distance divided by time.

Consider the cases where the units are from different orders of magnitude. An extremely tiny distance will almost by definition result in a slow speed; similarly, and extremely large distance will be a high speed. This may account for the large speeds we see in the macrocosm of planetary bodies and galaxies, as compared with the slow speeds we see in the realm of life and the nanocosm.

=Speed and the Nanoscale= Bacteria only appear to move quickly, a distortion of the magnification: they move exceedingly slowly. =Speed and Life= Bonner wrote, "everything seems to be rushing around at amazing speed, both galaxies and elementary particles. It is the nexus of life and molecules where things are the slowest. The three phase states solid, liquid, gas, are defined by movement of molecules, and this movement carries the diffusion and entropy pumping essential to life. The smaller the molecule, the faster it moves. The largest molecules form the smallest living creatures.

Brownian Motion
Bonner on Brownian Motion, from "Why Size Matters":

In this region of minimal speed of the material world we are in the realm of Brownian motion."

Bonner, "Size and Speed from the Cosmos to elementary Particles", Why Size Matters pp. 144-146:

In this region of minimal speed we are in the realm of Brownian motion.In 1827 Robert Brown, an English botanist, was looking inside some plant poHen and saw small bodies bouncing about, He correctly pointed out that the movement could not be a manifestation of life because the pollen was at least one hundred years old and therefore totally dead. With the rise of physical chemistry that followed as the century progressed, it became evident that molecules in the solution were bombarding the small visible particles in the liquid. Those molecules were too small to be seen in a light microscope, but their effect could be observed in the movement of larger visible bodies that were being rammed into, giving them a drunken, zigzag motion.The subject culminated in a paper by Albert Einstein published in 1905 in which he estab lished the theoretical basis of the phenomenon.

In terms of size and speed, large molecules are more or less in the same league with living bacteria, but from an evolution ary point of view the gap is enormous.The long, slow origin of life must have spanned many millions of years. However, here we are only concerned with speed and size, and large molecules and small bacteria move at roughly the same pace, a pace that is the slowest of everything that moves in the uni verse. Bacteria move, as was discussed earlier, by an elaborate and clever rotary propelling of flagella; molecules, on the other hand, do not have a motor but are propelled by inner energies that are part of their fundamental makeup.The larger the molecule becomes, the slower it moves. Motile organisms are just the opposite, for as we have seen, the bigger they are, the faster they travel.

What came first: did the invention of a means of propelling the organism come first and cause the evolution of size increase, or the reverse? Selection for size changes had to come first and become the prime mover, for if the selection for movement followed size increase, then one would expect different mechanical Ways of dealing with a particular size, and that is exactly what has happened.The smallest motile beasts, namely bacteria, have the extraordinary minirotary motor that can effectively move in the world of extremely low Reynolds numbers; in larger singlecell organisms, flagella do not rotate but contain contractile proteins that allow them to become active whips; in larger unicells, cilia beat like oars to move the cell; this is followed by the invention of muscle and bones to deal with running, swimming, and flying in larger animals.The progression of size during the course of evolution leads to a series of different inventions for locomotion, each appropriate for the dimensions of the organism. Obviously, this effect of size only applies to organisms that move, and there are many that do not: many species of bacteria, algae, fungi, many invertebrates such as sponges and corals, and all vascular plants.

For more information see Allometry.

=Speed and the Architectural Scale= The human eye can distinguish about 3 objects or features per second. A pedestrian steadily walking along a 100-foot (30-meter) length of department store can perceive about 68 features; a driver passing the same frontage at 30 mph (13 m/s or 44 ft/s) can perceive about six or seven features. Auto-scale buildings tend to be smooth and shallow, readable at a glance, simplified, presented outward, and with signage with bigger letters and fewer words.

For more information see human scale.

=Links and References= For other articles on the human scale, click here: include component="pageList" hideInternal="true" tag="human scale" limit="100"