5 Jun 2009

Bateson, We Only Sense Differences, in Mind and Nature: A Necessary Unity

by Corry Shores
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We Only Sense Differences

Gregory Bateson

Mind and Nature:

A Necessary Unity


Multiple Versions of the World

3. The Case of Planet Pluto

Human sense organs can receive only news of difference, and the differences must be coded into events in time (i.e., into changes) in order to be perceptible. Ordinary static differences that remain constant for more than a few seconds become perceptible only by scanning. similarly, very slow changes become perceptible only by a combination of scanning and bringing together observations from separated moments in the continuum of time.

An elegant (i.e., an economical) example of these principles is provided by the device used by Clyde William Tombaugh, who in 1930, while still a graduate student, discovered the planet Pluto.

From calculation based on disturbances in the orbit of Neptune it seemed that these irregularities could be explained by gravitational pull from some planet in an orbit outside the orbit of Neptune. The calculations indicated in what region of the sky the new planet could be expected at a given time.

The object to be looked for would certainly be very small and dim (about 15th magnitude), and its appearance would differ from that of another objects in the sky only in the fact of very slow movement, so slow as to be quite imperceptible to the human eye.

This problems was solved by the use of an instrument which astronomers call a blinker. Photographs of the appropriate region of the sky were taken at longish intervals. These photographs were then studied in pairs in the blinker. This instrument is the converse of a binocular microscope; instead of two eyepieces and one stage, it has one eye piece and two stages and is so arranged that by the flick of a lever, what is seen at one moment on one stage can be replaced by a view of the other stage. Two photographs are placed in exact register on the two stages so that all the ordinary fixed stars precisely coincide. Then, when the lever is flicked over, the fixed stars will not appear to move, but a planet will appear to jump from one position to another. There were, however, many jumping objects (asteroids) in the field of the photographs, and Tombaugh had to find one that jumped less than the others.

After hundreds of such comparisons Tombaugh saw Pluto jump. (81a.82a)

Bateson, Gregory. Mind and Nature: A Necessary Unity. London: Wildwood House, 1979.

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