Showing posts with label galilean telescope. Show all posts
Showing posts with label galilean telescope. Show all posts

Wednesday, May 26, 2010

Galileo's Starry Messenger in Curl web-content markup

Over at http://phil.aule-browser.com/ there is now a text of Galileo's Starry Messenger complete with marginal glosses.

The page requires the Curl plugin for your browser, which is available at http://www.curl.com/download/rte.

Galileo's text, also known as Sidereal Messenger or Sidereus Nuncius, recounts his construction of his telescope, his noting the surface of the moon, some nebula as themselves stars, the Milky Way as stars and the 4 great satellites of Jupiter.

I was able to find two other text versions on the internet, but both had deficiencies.

The marginal glosses had disrupted the OCR scan of the PDF images: they were restored manually using a custom Curl text procedure. Documentation on these can be found at the Curl site of Cambridge, MA. Curl Corporation, a subsdiary of Sumisho or by visiting an SCS web site.

Each marginal gloss is wrapped simply in {gloss } and placed before the text, itself wrapped in {para }.
Here is the gloss definition used at this time:
{define-text-proc public {gloss ...}:any
  {return {paragraph font-size = 12pt,
    font-family = "serif",
    paragraph-left-indent = 8pt,
    text-preserve-whitespace? = true, {italic {splice ...}}}}
}
which is found in the top-level curl file which includes the Galileo text as an scurl file. A reference to the top-level Curl file is embedded as an OBJECT in a regular HTM page at http://phil.aule-browser.com/messenger.htm

My versions of Hannah Arendt in The Human Condition on Galileo and his telescope can be found at http://phil.aule-browser.com/
Mention of a telescope is in Eugen Fink's Conversations with Husserl. For Husserl on Galileo, see his Krisis. For Heidegger on science and the instrument makers, see his Technik lecture. For excellent telescopes at fair prices, see http://www.astronomics.com/

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