Glenn Morton wrote:
> George Wrote:
> <<<
> In 1853 there were proponents of the idea that some of the nebulae were
> galaxies external to our own, but no compelling evidence for this view. At
> that time it wasn't possible to resolve individual stars in M31 (Andromeda)
> or other spirals and there was no way of measuring the distances to these
> objects. Thus it was quite reasonable to argue, as many astronomers did,
> that they were within the Milky Way. This situation continued for some
> time, & there seemed to be strong arguments against the extragalactic
> character of these nebulae. E.g., in ~1889 there was what we now know to be
> a supernova in M31, but since astronomers didn't know about SNs they thought
> it was an ordinary nova & greatly underestimated its distance. The
> extragalactic character of nebulae like M31 wasn't firmly established until
> the early 1920s. So on this point I'm not sure one can be too critical of
> Whewell. >>>
>
> I had always heard that also, but then I read in Whewell about the Nebula:
>
> "It was conceived that they were not stars, but Stellar matter in the course
> of formation into stars,; and it was conceived, further, that by the gradual
> concentration of such matter, whirling round its centre while it
> concentrated, not only stars, that is, suns, might be formed, but also
> systems of planets, circling round these suns; and thus this Nebular
> Hypothesis, as it has been termed, gave a ckind of theory of the origin and
> formation of systems such as the solar system. But the great telescope which
> Lord Rosse has constructed, and which is much more powerful than any optical
> instrument yet fabricated[is was 6 feet in diameter], has been directed to
> many of the nebulae, whose apearance had given rise to this theory; and the
> result has been, in a great number of cases, that the nebulare are proved to
> consist entirely of distict stars; and that the diffused nebulous appearance
> is discovered to have been an illusion, resulting from the accumulated
> light of a vast number of small stars near to each other. In this manner, we
> are led to regard every nebulae, not as an imperfectly formed star or system
> but as a vast multitude of stars, and, for aught we can tell, of systesm;
> for the apparent smallness and nearness of these stars are, it is thought,
> mere results of the vast distance at which they are placed from us." p. 12
>
> I reassert my claim, that knowing of a impressive point of data against the
> view he was advocating, he still advocated it. Indeed, he even talks about
> linear wisps of nebula being resolved into stars. But then he turns around
> and calls them mere dots of light and goes into his comet claim. The point
> is even with today's telescopes most stars are mere points of light and all
> were that way for Whewell yet he treats points of light in the galaxies
> differently than points of light not in the nebula.
You've read Whewell & I only summaries of him, & I don't want to dispute
your basic point about the tendentious character of his argument.
But in the mid-18th century "the nebulae" included a number of different
kinds of objects. There were some objects that did indeed consist of individual
stars with or without other "nebulosity"
that are within the Milky Way, like the Orion Nebula. But there were others
like M31 that we now know to be external galaxies but that couldn't be resolved
into stars at that time. The latter are the ones that had been hypothesized to
be "island universes" by some, but this claim was disputed by others. It's
really this "island universe" idea that was being debated &, as I noted, the
debate wasn't settled till ~70 years after Whewell wrote.
I'll be out of touch for ~1week. (Some will say I have been for a long
time!)
Shalom,
George
George L. Murphy
http://web.raex.com/~gmurphy/
"The Science-Theology Interface"
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