S

Figure 3.25. The "man in the moon" depends on the inability of the human eye to discern features smaller than the maria on the Moon's surface.

aperture. He also mentions that the image of an eclipsed Sun can be seen through foliage or lattice. The frst clear description of the device appears in the Book of Optics of Alhazen [Islamic astronomer, d. Egypt, 1038], reproduced by Vitello [Polish philosopher, b. 1230] in his own work on optics. Roger Bacon [Franciscan scientist, b. ~1214] also discusses it in his Perspectiva (1614), in combination with a "specula." Maurolycus [mathematician, Messina, ~1521] applied it to observational study of the Sun. On a large scale, light from an illuminated scene may be passed through a narrow aperture into a darkened room where it may fall on a far wall and appear magnified in the process. The result can be spectacular. In a large congress hall in New Delhi in 1985, EFM witnessed scenes of the brightly lit lobby projected onto a large white screen at the front of the darkened hall whenever the door was just opened or had nearly shut. In Edinburgh, Scotland, near the top of the Royal Mile, there is a camera obsura projecting a magnificent view. It has been suggested that similar means was used to create a Jaguar (the Pleiades) map on the floor of a building at Teotihuacan in Mesoamerica in the early centuries a.d. (see §12.22), but experimental verification is desirable, because the greater the magnification, the lower the surface brightness of the image. If a lens is inserted at the aperture, magnification and a brighter image can be achieved. The camera lucida, a device that employs prisms to reproduce a virtual image superposed on a draughtsman's field of view, was not invented until the 19th century (by W.H. Wollaston).

We conclude this chapter with a question, previously raised by Schlosser et al. (1991/1993, p. 116). The influences on the pace of technological development of human societies have been the topics of many learned discussions. What would have been the consequences for such development if our eyes had just slightly better acuity ? (See Figure 3.25 for a deresolved photo of the Moon, to match normal human vision.) Perhaps Megalithic observers would have noticed such phenomena as the disks of some of planets—and the Venerian crescent, lunar mountains, and the brightest moons of Jupiter. Perhaps a scientific age would have dawned not merely centuries ago but several millenia before that. Or would it have?

From the spatial domain of human perception, we now proceed to the temporal.

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