Maunder's perception experiments

RH says..... Since Christie is away on his Easter holidays, and since I am working on a lecture on pre-space age observations of Mars, I thought I would briefly return to the theme of E. Walter Maunder's experiments on perception with the boys of Royal Hospital Schools in Greenwich (see my previous entry for background). Since the scan of his 'Experiments as to the Actuality of the "Canals" observed on Mars' available online has very unclear images, I thought I would rescan them and put them up here. The first shows (top) a photograph of a drawing based on an original by Giovanni Schiaparelli - but with the controversial straight canals replaced by "a number of small irregular markings ... inserted at haphazard" and "river-like marks". This drawing was shown to the boys, and the second image shows photographs of six of their drawings, produced from observations at varying distances from the original. Despite the absence of straight lines, most of the boys - especially those sitting in the middle rows - produced canal-like markings that agreed closely with the schematic Key Map shown at the bottom of the first image. Three boys, in addition, included a short line where Schiaparelli did not - "which we have here called from the name of its disocverer, 'Allen's Canal.'"

Maunder on Mars

RH says..... Time to return to Mars, this time focusing on the views of E. Walter Maunder, the head of the Royal Observatory's Photographic and Spectroscopic Department. Maunder seems to have become involved with the debates about the nature of Mars's surface through meetings of the Royal Astronomical Society and the British Astronomical Association, which he had founded in 1890. Since 1877, discussions had tried to account for the differences between the maps produced in that year's heliostatic opposition (the best possible viewing conditions for Mars) by Giovanni Schiaparelli and Nathanial Green.


















Green, an amateur astronomer but a professional artist and longtime Mars observer with a powerful telescope, had apparently seen something very different from Schiaparelli, the director of Milan's Brera Observatory but a first-time Mars viewer. Maunder essentially sided with his compatriot and initially agreed that it was most likely that the lines seen by Schiaparelli were the boundaries of differently shaded regions. He became interested in how such optical effects might be produced and, in 1902-03 went to the extent of experimenting on the boys of the Royal Hospital Schools, Greenwich (now the buildings of the National Maritime Museum) to see if images of "canals" could be produced when images without lines were viewed at various distances. His 'Experiments as to the Actuality of the "Canals" observed on Mars' concluded that in most cases,

"the canals of Mars ... are simply the integration by the eye of minute details too small to be separately and distinctly defined. It would not therefore be in the least correct to say that the numerous observers who have drawn canals on Mars during the last twenty-five years have drawn what they did not see. On the contrary they have drawn, and drawn truthfully, that which they saw; yet for all that, the canals which they have drawn have no more objective existence than those which our Greenwich boys imagined they saw on the drawings submitted to them."

Observations of Mars in 1894

RH says..... 1894 was a significant year in astronomy for observations of Mars. While the Royal Observatory Greenwich, was not initially involved, E. Walter Maunder, who headed Greenwich's Photographic and Spectroscopic Department, was later to join the Martian 'canals' debate sparked by the observations of Percival Lowell. Influenced by the observations of Giovanni Schiaparelli, who had named certain features on Mars 'canali' (meaning a natural water channel, but mistranslated as 'canals'), and the popular writings of Camille Flammarion, Lowell set out to study the solar system from his observatory in Arizona. In May 1894 he said:

Speculation has been singularly fruitful as to what these markings on our next to nearest neighbor in space may mean. Each astronomer holds a different pet theory on the subject, and pooh-poohs those of all the others. Nevertheless, the most self-evident explanation from the markings themselves is probably the true one; namely, that in them we are looking upon the result of the work of some sort of intelligent beings. . . . [T]he amazing blue network on Mars hints that one planet besides our own is actually inhabited now.

He began observing the same month and saw what he hoped, or expected, to see - and created these iconic maps of the Martian surface. See this chapter on Lowell of William Sheehan's The Planet Mars: a History of Observation and Discovery for more, and I will return to Maunder's response in a later post.....