[Beowulf] Stroustrup regarding multicore

Lux, James P james.p.lux at jpl.nasa.gov
Wed Sep 3 06:44:44 PDT 2008

On 9/3/08 2:04 AM, "Greg Lindahl" <lindahl at pbm.com> wrote:

> On Thu, Aug 28, 2008 at 11:54:05AM -0400, Peter St. John wrote:
>> I think a physicist programming is like an astronomer grinding lenses (maybe
>> nobody does that anymore). Some astronomers (in the old days) ground their
>> own lenses and ended up contributing to optics; others never looked through
>> telescopes, they do math on the measurements taken by others.
> This is the 2nd funniest posting in this thread. Did you notice that
> ground-based telescopes recently started being much, much bigger?
> These new lenses were invented and made in Arizona by an astronomer,
> who figured out how to spin molten glass into roughly the right shape,
> instead of taking a huge, flat, thick piece of glass and grinding it
> into the shape of a mirror.
> http://www.npr.org/templates/story/story.php?storyId=4773461
> ----
Ahem.. Reflectors, not lenses

And, actually, the fact that a spinning body of liquid assumes a parabolic
shape has been known for centuries (Kepler?), and, in fact, as early as
1850, an
astronomer (Ernesto Capocci) proposed and built a telescope using liquid
metal (e.g. Mercury) for a reflector.  He probably wasn¹t unique, as there
are mentions of a Mr. Buchan in notes by Brewster (as in Brewster angle)
about the same time.  There¹s a fascinating thesis by Brad Gibson from Univ
of Vancouver that gives a dozen or so pages of all the problems faced with
liquid metal telescopes (ripples, etc.)
 What Dr Angel and the folks in Arizona have done is build an enormous
spinning oven and worked out the process controls (more of an engineering
task than a science, one, I might add.. Being an Engineer, I think these
distinctions are important, not that new science isn't being done here).
They also still have to do a conventional polishing step, but, at least the
general figure of the mirror¹s surface is already close to what it needs to
be.  (Interestingly, there¹s apparently an article about this in Science
News back in Feb 1985, which is when the latest work in LMTs got going at

Jim Lux

More information about the Beowulf mailing list