Question: where in Krisis does Husserl indicate that he was aware that Galileo was looking through a spyclass at Venus and Jupiter and not through a Keplerian-style inverting refractor telescope? My copy and the English translation are packed away in a box until that day when I again have some office space ...
Fernglas?
Teleskop?
The former was of particular value to artillery officers prior to the calculus; see Galileo and the geometry of canon shots for best distance; see Husserl's naive stance on war during the early years of WWI (cp: B. Russell, same period)
See the use of optical transit with howitzer altititude and azimuth positioning through both Korea and Vietnam.
Transit and land surveying versus the forester's compass for the German managed woodlot: example, Marburg Lahntal opposite the old university in der naehe von Cappel.
Compare: GPS and digital alt-az encoders.
Google books Krisis
Google books Crisis
Historical note: Kepler's "observations" are not chiefly with a telescope. Cf: later use of "zenith telescope" and the last precision US Navy zenith telescope and its reliance on mechanics for its optical precision.
vide perspicillum
Showing posts with label keplerian telescope. Show all posts
Showing posts with label keplerian telescope. Show all posts
Sunday, November 7, 2010
Friday, May 21, 2010
Arendt, Venus and Telescopes: Galileo or Kepler or Newton?
In Chapter VI of The Human Condition Hannah Arendt makes no distinction between the refracting telescope of Galileo and that of Kepler (let alone the Newtonian reflector.)
There is, of course, a world of difference. Galileo's "telescope" was an improved "glass" or "tube" - a spyglass - such as an artillery officer might use. He likely first constructed one using spectacle lenses.
Heidegger - when he first taught on science and instrument-makers - was not wearing spectacles.
What Galileo was reporting to Castelli was that Venus had the phases of the moon. This was a crucial defeat for geocentrism as a theory (as a fact - as opposed to mere theory - the Earth and Sun move approximately about their common center of mass - which happens to be within the radius of the Sun.)
What Kepler predicted was the transit of Venus across the face of the Sun (but it was not in fact visible in Europe that year of 1631 (and Kepler already dead) - but the transit of Mercury was.)
The next transit of Venus is June 6, 2012 after which there will not be another for more than 100 years.
What Arendt soft-pedals is that these phases of Venus and transits of the Sun were phenomena in the very sense in which that word was used by Greeks speaking of the night sky. But in Kepler's case, his telescope was not a mere spyglass: the "image" was not the "normal" view of a spyglass. Kepler used a subjective lens with a short focal length and an objective lens with a long focal length; Galileo's subjective lens was concave; Kepler's was not. Kepler's "image" was inverted - but the field of view was wider and provided eye relief - essential to those wearing spectacles. But Kepler's view of Venus would have been plagued by false colors (unlike Newton's.)
Heidegger would have noted that an early telescope maker was none other than an instrument maker. But was Galileo's inclined plane an instrument distorting the things as given?
And those who sought to be the first to name the moons of Venus?
Some of these remarks I will add as annotations at http://phil.aule-browser.com/arendt.htm
cf: Heidegger, "Die Frage nach der Technik" in Vortraege u. Aufsaetze
There is, of course, a world of difference. Galileo's "telescope" was an improved "glass" or "tube" - a spyglass - such as an artillery officer might use. He likely first constructed one using spectacle lenses.
Heidegger - when he first taught on science and instrument-makers - was not wearing spectacles.
What Galileo was reporting to Castelli was that Venus had the phases of the moon. This was a crucial defeat for geocentrism as a theory (as a fact - as opposed to mere theory - the Earth and Sun move approximately about their common center of mass - which happens to be within the radius of the Sun.)
What Kepler predicted was the transit of Venus across the face of the Sun (but it was not in fact visible in Europe that year of 1631 (and Kepler already dead) - but the transit of Mercury was.)
The next transit of Venus is June 6, 2012 after which there will not be another for more than 100 years.
What Arendt soft-pedals is that these phases of Venus and transits of the Sun were phenomena in the very sense in which that word was used by Greeks speaking of the night sky. But in Kepler's case, his telescope was not a mere spyglass: the "image" was not the "normal" view of a spyglass. Kepler used a subjective lens with a short focal length and an objective lens with a long focal length; Galileo's subjective lens was concave; Kepler's was not. Kepler's "image" was inverted - but the field of view was wider and provided eye relief - essential to those wearing spectacles. But Kepler's view of Venus would have been plagued by false colors (unlike Newton's.)
Heidegger would have noted that an early telescope maker was none other than an instrument maker. But was Galileo's inclined plane an instrument distorting the things as given?
And those who sought to be the first to name the moons of Venus?
Some of these remarks I will add as annotations at http://phil.aule-browser.com/arendt.htm
cf: Heidegger, "Die Frage nach der Technik" in Vortraege u. Aufsaetze
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