So-called Canal Research Articles

Contour-crossing statistics for small scale structure on radio polarized intensity maps of the interstellar medium

The applicability of contour-crossing statistics to radio polarized intensity maps of the interstellar medium is discussed with the aim of extracting physical information on interstellar turbulence. We determine to what extent contour-crossing statistics is right for the description of narrow regions of low polarization (so-called canals), whose existence has been discussed recently by some researchers. Contour-crossing statistics can yield the characteristic sizes of small scale structures on the maps, and be used to estimate the scale of fluctuations in the interstellar medium.

Erratum: Faraday ghosts: depolarization canals in the Galactic radio emission

Narrow, elongated regions of very low polarized intensity -- so-called canals -- have recently been observed by several authors at decimeter wavelengths in various directions in the Milky Way, but their origin remains enigmatic. We show that the canals arise from depolarization by differential Faraday rotation in the interstellar medium and that they represent level lines of Faraday rotation measure RM, a random function of position in the sky. Statistical properties of the separation of canals depend on the autocorrelation function of RM, and so provide a useful tool for studies of interstellar turbulence.

On the Role of Marketing Theory

Theory in Popular Language Words mean different things to different people and there is little point in arguing definitions. But meaningful discussion is only possible if the connotation of a word is the same to all who employ it. This has not been the case in the use of the word theory, which means one thing to the layman and something entirely different to the theorist. As a result, the public has a distorted view of the goals and methods of research. In common parlance theoretical is taken to be a contradictory either of factual or of practical. A theory is the term often used to denote an allegation of fact for which no evidence has been presented. Unverified statements about the chemical composition of some compound, or about the behavior of some group of Australian aborigines, or about the nature of the so-called canals on Mars are all likely to be labeled theories. However, in

Geological interpretations of the markings on Mars.

view Abstract Citations (10) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Geological interpretations of the markings on Mars. Tombaugh, C. W. Abstract The increased knowledge of the physical conditions on Mars during the past two decades warrants an attempt to explain the nature of the surface markings as being of geologic origin. It appears likely that Mars has always had a thin atmosphere, very little water, and a very dry climate. The lower temperature prevailing there would greatly retard the process of oxidation, so that the reddish-ochre desert areas may not have robbed the atmosphere of its oxygen to the degree which has commonly been supposed. There is evidence that the deserts consist of rhyolitic igneous rock, little altered by chemical action. The color of the Martian deserts compares well with the natural color of rhyolite samples. The known physical and geological conditions on Mars are consistent with the planet S size and distance from the sun. The distribution of the maria and the desert areas conforms well with tetrahedral deformation of a globe which suffered shrinkage in volume after a thick crust had formed. There is a striking similarity to the earth in this respect. There is good evidence that the maria are the lowest regions on the planet, and they occupy the faces of the tetrahedral figure. The vertices fall in the middle of the great expanses of desert. The eccentric position of the south polar cap remnant suggests that the fourth vertex lies near the south geographical pole in the general longitude of 00. The juxtaposition of the high Hellas plateau with the very low altitude Syrtis Major, represents a diastrophic situation frequently found on the earth. The lack of water erosion on Mars would permit the surface to retain a visible record of the major events that happened during the planet's entire separate existence, similar to that on the moon. The round "oases are depicted as the sites of impact craters caused by the collisions of small asteroids. Great dust clouds on Mars are observed occasionally. They indicate some wind erosion, which if extended over long geologic ages would mitigate the abrupt slopes of the craters. The dark color and seasonal behavior are undoubtedly due to the growth of vegetation, perhaps similar to our lichens, which finds a favorable environment in the pulverized igneous rock and shelter offered by the crater. It is noted that the oases of Mars are much less numerous than lunar craters of corresponding size. This may indicate that the craters on the moon were formed mainly by the infall of large planetesimals produced by the birth-of-the- moon process, while those of Mars may have been produced entirely by collisions with asteroids. The invocation of intelligence to explain the extra-terrestrial characteristics of the so-called canals was a reasonable hypothesis in its day. But stern geological considerations of the planet's natural resources is highly unfavorable to the economics required for such a civilization. The canals cannot be entirely relegated to the realm of illusions, in spite of the unfortunate misrepresentation given by the drawings of some observers nor by the doubts of those who do not know how to see fine planetary detail. The radial pattern of the canals with respect to the oases is attributed to fracturing of a thick crust under strain by the impact of asteroids which created the oases. The fractured zones could give haven to a hardy vegetation in regions of unfavorable environment. The seasonable behavior of the canals can be explained by the growth of vegetation capable of absorbing the slight moisture from the air after the polar caps melt and evaporate during each Martian year. Las Cruces, N. Men. Publication: The Astronomical Journal Pub Date: October 1950 DOI: 10.1086/106434 Bibcode: 1950AJ.....55Q.184T full text sources ADS |

The Minor Details of the Planet Mars

IN the issue of NATURE for April 8, p. 518, a note appears on an article on Mars by Mr. H. B. Brydon, in which particular reference is made to my recent volume on the planet and my conclusions as to the illusory nature of the so-called canals. In order that readers of NATURE should not be misled by the article, I hasten to reply to Mr. Brydon's statements.

The Optical and Psychological Principles Involved in the Interpretation of the So-Called Canals of Mars.

The Optical and Psychological Principles Involved in the Interpretation of the So-Called Canals of Mars.