The American philosopher Abraham Kaplan (1918-1993) describes
scientific observation as follows;
An observation in science is first of all something done, an act performed by the scientist; only thereby is it something seen, a product of the process in which the scientist is engaged … Scientific observation is deliberate search, carried out with care and forethought, as contrasted with the casual and largely passive perceptions of everyday life.
This type of deliberate and careful observation became a
distinctive part of the natural sciences during the early modern era of western science (roughly 1490 -1730).
Christoph Scheiner (1573 - 1650) was a Jesuit physician,
astronomer and mathematician who was a contemporary of Galileo. He was a first
rate scientific observer. Early in his career, Scheiner invented the Pantograph, built his own telescope and
drew a map of the moon's surface. He is best known for the brilliant observations
of sunspots he made in March 1611.
Scheiner's major work is Rosa
Ursina (1630), in which he describes and plots dozens of sunspot
observations and criticises some of Galileo's calculations. In common with
Galileo, Christoph Scheiner vigorously argued for the primacy of
observation in natural science.
In Rosa Ursina, he asserts that: Against a single,
true, observed fact a
thousand hair-splitting arguments
are without any
value at all.
In 1619 Scheiner published Oculus
hoc est: Fundamentum opticum. This
is a thorough investigation of the optical properties of the human eye,
including its anatomy, refraction of light by the eye and the role of the
retina in vision. Throughout the book, Scheiner describes his observations,
experiments and experiences, not a set of theoretical conjectures. Many of
Scheiner's investigations include elegant experiments with pinholes, that show how light, optical phenomena and the eye work.
The simplest of all image forming devices is a small, clean,
pinhole punched through an opaque sheet of material. Even without a lens of any
sort, a pinhole can produce a rudimentary image of a well-lit scene. Although
these images are inverted, faint and somewhat blurred, they are recognisably
images. The earliest record of a pinhole image is the Mo Ching, a text by the Chinese scholar Mo Ti (also known as Mo Tzu)
from about 400 BCE. Since Mo Ti, a small image forming hole has been variously
known as a stenopeic disk, pinhole camera, camera
ottica or camera obscura. This knowledge was developed and used by the
early medieval Chinese statesman and philosopher Shen Kua (c.1031 - 1095) who described the inverted and reversed image which
forms on a wall opposite a small hole in a dark room.
This illustration from Oculus
hoc est summarises Scheiner's experimental investigation of what happens to
the light rays that have been reflected from an object as they pass through a
pinhole. The inferential step made by Scheiner using this experimental
apparatus is clear; the observed left-right image inversion seen through a
pinhole is not found on the far side
of the pinhole, but only on this side, and thus the conclusion is that it has
been caused by the pinhole itself.
This simple experiment provides evidence of how the pinhole works as an optical
element and illustrates that light travels in straight lines: I-H-L and K-H-M.
Two of the practical uses that Scheiner found for pinholes;
the Pinhole occluder and the Scheiner disk, are still used by
ophthalmologists and optometrists as diagnostic tests.
Book available HERE.
References
Daston, L. & Lunbeck, E. (eds.) (2011). Histories of
Scientific Observation. University of Chicago Press.
Daxecker, F. (1994). Further studies by Christoph Scheiner
concerning the optics of the eye. Documenta
Ophthalmologica. 86 pp. 153-161.
Kaplan, A. (1964). The
Conduct of Inquiry: Methodology for Behavioral Science. Chandler Publishing
Company, San Fransisco.
Needham, J. (1986). Science
and Civilization in China: Volume 4, Physics and Physical Technology. CUP,
Cambridge.
Scheiner, C. (1626 - 1630). Rosa Ursina, sive sol ex admirando facularum & macularam suaram
phoenomeno varius. Bracciano.
