HDTenEightyP/NetNews huggingface dataset:
From: craycrof@ruchbah.rtp.semi.harris.com (Bob Craycroft x629)
Subject: Re: Bright Green Fireball
Date: Mon, 12 Oct 1992 16:02:40 GMT
Distribution: na
Organization: Harris Semiconductor, Research Triangle Park, NC

In article <1992Oct12.085326.1@scivax.stsci.edu> gliba@scivax.stsci.edu writes:
>
>   A bright green fireball was seen over several states on friday night.
>It was said to be nearly as bright as the moon. I did not see it, but
>several witnesses that I talked to described it as quite spectacular.

The reports I've heard say it was seen from SC to NY and west to KY.
Reports had it moving generally south to north, which would seem to
eliminate the Draconids.

>One witness, a naturalist for the Audubon Naturalist Society, saw it
>at about 7:50 EDT when he was leading a night walk on the C&O Canal on
>Maryland. He said it was traveling northern sky, was bright green in
>color, and broke up into eight pieces. One report from Ohio said the
>fireball was video taped during a local football game.

The event was *definitely* taped by WRAL-TV in Raleigh, NC, by a crew
that was out taping high school football games.  The footage was aired
during Friday night's news broadcast.  The fireball appeared greenish
with yellowish flames and a long trail.  Several pieces, maybe half a
dozen pieces 10% to 20% of the angular size of the main body, were
clearly visible.  I wish I had gotten the VCR going in time to tape
this and study it in more detail.

>                                                       As luck would have
>it, I was suppose to go on the above stated night walk friday, but because
>it was full, I was scheduled for the next night. Did anyone else see this
>barn burner.

I'm sure I would have been out under the spectacularly clear skies if
not for that #!$@! moon!
-- 
Bob Craycroft
Harris Semiconductor - RTP, NC
Internet:  craycrof@rtp.semi.harris.com		Phone: (919) 549-3629
From: rabjab@golem.ucsd.edu (Jeff Bytof)
Newsgroups: sci.astro
Subject: Re: Mars Observer and the "Face"
Date: Mon, 12 Oct 1992 16:41:16 GMT
Organization: ucsd
NNTP-Posting-Host: lutherlab.ucsd.edu

>Mars Observer and the Martian "face"?: 
>Does NASA even have an opinion on this? Is any hi-res coverage planned? There
>are all kinds of rumors flying, including "the hi-res camera isn't easily
>pointable, so no hi-res coverage is planned"... how about clarification?

I'm not from NASA, but it's my understanding that the cross-track pointing 
error of the hi-res camera is greater than the width of a swath (2.8 km).
This is due to uncertainty in the orbit.   The Mars Observer project
is not required to do precise pointing with the hi-res, though it certainly 
would be desireable.  Some effort may be made to use optical navigation
to improve the knowledge of the orbit so that certain critical images
can be acquired (i.e. imaging a Viking lander on the surface).  I
heard that an attempt to image the "face" would be made also.

---------------------
rabjab@golem.ucsd.edu
Newsgroups: sci.astro,sci.space
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Date: Wed, 14 Oct 1992 23:08:21 GMT
Organization: U of Toronto Zoology

In article <NICKH.92Oct14161614@VOILA.VENARI.CS.CMU.EDU> nickh@CS.CMU.EDU (Nick Haines) writes:
>What's the solar wind pressure at 1AU?

Negligible compared to the photon pressure.  (Now that's small...)
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry
From: elliottb@cnsvax.uwec.edu
Newsgroups: sci.astro
Subject: days of the week
Date: 9 Oct 92 14:19:01 GMT
Organization: University of Wisconsin Eau Claire


exit
From: mock@space.mit.edu (Patrick C. Mock)
Newsgroups: sci.astro
Subject: Re: Discrete Red Shifts
Date: 11 Oct 92 22:25:26 GMT
Reply-To: mock@space.mit.edu (Patrick C. Mock)
Organization: MIT Center for Space Research
Originator: mock@benz


In article <Bvz65y.E73@well.sf.ca.us>, metares@well.sf.ca.us (Tom Van Flandern) writes:
> 
> shade@chdasic.sps.mot.com (Douglas Shade) writes:
> 
> > I heard a lunch discussion today which had to do with the recent
> > conclusions that all known red shifts are falling into discrete regions.
> > (i.e. quantum levels?)
> >
> > Does any body out there have a reasonable (or humorous) explanation for
> > this?
> 
>      As I reported here recently in my meeting summary for the conference
> "Progress with New Cosmologies" last month, the reported "quantization" of
> cosmological redshift of galaxies at about 37 km/s intervals out to at least
> 2000 km/s redshift (first reported by Tifft) has recently been confirmed by
> Napier and colleagues, who set out originally to show that it was a
> statistical fluke or sampling problem.  They used a completely independent
> sample which showed the same effect that Tifft had reported a decade earlier.
> There is now little room to doubt the reality of the effect.
> 
I think there is a lot of room for doubt yet.

I read the Guthrie and Napier paper and the Sky & Telescope article and
discussed these with one of our local xray pulsar experts.  He noted the 
following problems.

1)  In Figure 2, the peak value is I=18.1.  My local expert used the same
    power spectrum analysis (PSA) technique to analyze xray pulsar data. 
    When looking for pulsar periodicities he considers anything less than I=30
    uninteresting and often saw values of I=20 or so from nonperiodic sources.

2)  Galaxy clustering is well established but not well understood.  Thus
    galaxy redshifts should be correlated.  The PSA assumes these correlations
    are due to underlying periodicities even if that is not the case.

In summary the PSA is notorious for false alarms and it can be fooled by
nonperiodic correlations.  It is most useful when you independently know your
data is periodic and you want to accurately determine the period.  It is
not a good tool for determining if the data is periodic.

A better method for analyzing data for periodicity is described in detail by
Gregory & Loredo.  They present a general method for detecting and measuring
periodicity based on Bayes Theorem.  I will remain skeptical of these results
until Tifft, Guthrie, Napier, etc. use better tools to analyze their data.

REF: 	Sky & Tel, Aug92, p128; 
	Guthrie & Napier, MNRAS 253, p533
	Gregory & Loredo, ApJ, 398, p146

Pat
From: dsc@gemini.tmc.edu (Doug S. Caprette Bldg. 28 W191 x3892)
Newsgroups: sci.astro
Subject: Re: Meteoryite hits car in New York state
Date: 15 Oct 92 20:29:55 GMT
Organization: NASA GSFC CDP VLBI

In article <92288.29126.L629159@LMSC5.IS.LMSC.LOCKHEED.COM> L629159@LMSC5.IS.LMSC.LOCKHEED.COM writes:
>1. Assume the meteorite described in this thread is
>approximately spherical with a diameter of 30 cm, and
>that it has a mass of 13000 gm (given in original
>post).
>
>2. Compute density.
>
>3. Laugh.
>
>Al Moore

One gm/cc is certainly the right order of magnitude for the density of a 
stony meteorite.  It at least appeared to be a stony meteorite on TV.  It
also appeared to be rather nonspherical.  I'd say that a better rough model
for its shape would be a right triangular prism, with:
base ~ 15cm
height ~ 25cm
hypotneuse ~ 30cm
thickness ~ 15cm

This yields a density closer to 5 gm/cc.   How does this compare with the
density of a typical stony meteorite.

If you were to model a cow, would you begin by assuming it's a sphere?
(:-)
Newsgroups: sci.astro,sci.space
From: hbeniker@lonestar.utsa.edu (Herbert D. Beniker)
Subject: looking for books on telescope making
Organization: University of Texas at San Antonio
                                 -Dan B
Distribution: usa
Date: Fri, 9 Oct 1992 18:29:10 GMT
From: mal11@po.CWRU.Edu (Matthew A. Lewis)
Newsgroups: sci.astro
Subject: rumor concerning Saturn's rings
Date: 13 Oct 1992 02:27:21 GMT
Organization: Case Western Reserve University, Cleveland, OH (USA)
Reply-To: mal11@po.CWRU.Edu (Matthew A. Lewis)
NNTP-Posting-Host: slc5.ins.cwru.edu



Could someone please tell me when the rings around Saturn were
discovered????

I heard an rumor that people in ancient times could see them (and
a whole lot of other stuff) with the naked eye.....

thanx in advance

-- 
maThiEu a. LeWis    
cyber-mercenary         This sentnce has threee errors. 
Thieves Like Us      
mal11@Po.cwru.edu
From: steinly@topaz.ucsc.edu (Steinn Sigurdsson)
Newsgroups: sci.astro
Subject: Re: A 100 Billion?
Date: 13 Oct 92 11:40:43
Organization: Lick Observatory/UCO
NNTP-Posting-Host: topaz.ucsc.edu
In-reply-to: harmons@mithril.wv.tek.com's message of 13 Oct 92 17:49:13 GMT

In article <1959@shaman.wv.tek.com> harmons@mithril.wv.tek.com (Harmon Sommer) writes:


   A local newspaper article on SETI mentioned that there are 100 Billion stars
   in our solar system. How is this quantity arrived at? 

Through profound ignorance.
There is one star in our solar system.

|  Steinn Sigurdsson	|I saw two shooting stars last night		|
|  Lick Observatory	|I wished on them but they were only satellites	|
| steinly@lick.ucsc.edu |Is it wrong to wish on space hardware?		|
| "standard disclaimer"	|I wish, I wish, I wish you'd care - B.B. 1983	|
From: edb@hpgrla.gr.hp.com (Ed Beshore)
Date: Tue, 13 Oct 1992 14:56:29 GMT
Subject: Re: read-write optical drives
Organization: Hewlett-Packard, Greeley, CO
From: carl@SOL1.GPS.CALTECH.EDU (Carl J Lydick)
Newsgroups: sci.astro,sci.research,ca.earthquakes,sci.geo.geology,sci.geo.meteorology,sci.archaeology
Subject: Re: THE TRUE CAUSE & ORIGIN OF EARTHQUAKES (AND THEIR PREDICTION)
Date: 16 Oct 92 22:14:28 GMT
Reply-To: carl@SOL1.GPS.CALTECH.EDU
Organization: HST Wide Field/Planetary Camera
NNTP-Posting-Host: sol1.gps.caltech.edu

In article <1992Oct16.204731.2374@pony.Ingres.COM>, kevinq@Ingres.COM (Kevin Quinn) writes:
>In article <1992Oct16.180329.7282@athena.mit.edu> pat@mtl.mit.edu (Patricia E. Varley) writes:
>>A Ted Holden clone for all of us!
>   ^^^^^^^^^^
>
>Do *not* invoke this name - he may hear you and come back!!!!!!!!

At least he didn't use the G-word.
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: CARL@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL

Disclaimer:  Hey, I understand VAXen and VMS.  That's what I get paid for.  My
understanding of astronomy is purely at the amateur level (or below).  So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it.  If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.
Newsgroups: sci.astro
From: hbeniker@lonestar.utsa.edu (Herbert D. Beniker)
Subject: looking for books on telescope building
Organization: University of Texas at San Antonio
Distribution: usa
Date: Fri, 9 Oct 1992 18:15:41 GMT

                        -Dan B
From: jbatka@desire.wright.edu
Newsgroups: sci.astro
Subject: Re: Again: What makes Fireballs green
Date: 15 Oct 92 17:59:15 GMT
Organization: Wright State University

In article <92289.102357K3032E0@ALIJKU11.BITNET>, Herbert Raab <K3032E0@ALIJKU11.BITNET> writes:
> 
> Sure enough, the forbidden lines of Oxygene are NOT responsible for the
> green color. *Sorry*

Spectroscopy is not balliwick, so I'm not arguing.  However, I am curious
both of the Oxygen lines were dismissed based upon them being *forbidden*
ionizations (based upon gas density).  Does anyone have any information
on the altitude (thus density) at which these fireballs floresce (sp?)?
You can also get atmospheric composition data based upon altitude and
if it is high enough, I believe there are relatively high concentrations
of ionized Ox and NOx species previously existing.

> But I do not think the composition of the meteoride is very important for
> the color of the fireball. Meteors from Streams (coming from comets) should
> have different colors than "ordinary" stony meteors or even irons, if that is
> true.
> By the way, copper is quite rare in meteorites, even in iron meteorites.
> The light you see is mostly the ionized trail of the meteor in the upper
> atmosphere, the glowing body itself is hardly (or probalbly not at all)
> visible. So it's probably  OI emmisson...?
> 
> Greetings
>   Herbert Raab
-- 

   Jim Batka  | Always remember ...                        | Buckaroo
   Modemman   |    No matter where you go, there you are!  |   Bonzai
--------------+--------------------------------------------+--------------
It is very    | Work Email:  BATKAJ@CCMAIL.DAYTON.SAIC.COM | Elvis is
often easier  | Home Email:  JBATKA@DESIRE.WRIGHT.EDU      |   DEAD!
to get for-   |--------------------------------------------+--------------
giveness then | 64 years is 33,661,440 minutes ...         | Beatles:
permission.   |    and a minute is a LONG time!            |   Yellow Submarine
Newsgroups: sci.astro
From: higgins@fnalo.fnal.gov (Bill Higgins-- Beam Jockey)
Subject: SF cookbook & Jupiter Jello (was Re: SF Food)
Followup-To: sci.astro,rec.arts.sf.misc,alt.fan.pern
X-Newsgroups: rec.arts.sf.misc,alt.fan.pern
Organization: Fermilab, Batavia, IL
Date: Wed, 14 Oct 1992 01:12:14 GMT
X-From: higgins@fnalo.fnal.gov (Bill Higgins-- Beam Jockey)

X-Xref: linac rec.arts.sf.misc:3381 alt.fan.pern:2104
X-Sender: daemon@linac.fnal.gov (The Background Man)
X-Nntp-Posting-Host: fnalo.fnal.gov
X-Organization: Fermi National Accelerator Laboratory
X-Date: Wed, 14 Oct 1992 01:05:39 GMT

In article <1b7sulINN25j@werple.apana.org.au>, kat@werple.apana.org.au (Kathryn Andersen) writes:
> 
> Hello you knowledgable persons - can you help me?
> I am looking for SF-related food, for a party
> with an SF theme.  

I know a good place to get some ideas...

Mary Lynn Johnson, a multitalented artist in this vicinity, put
together an SF fannish cookbook a couple of years ago called
*Adventures in Thyme and Spice*. Fans and pros contributed recipes,
and the pages are graced with black-and-white illustrations by many
artists. It's comb-bound in 8.5 x 11-inch format.

Cost is US$15.00 (postage and handling included if you're in the US).
She says she'll send it to Australia for US$17.00. It might not arrive
in time for your party, though!  All profits from the book go to
charity.

Write to:

Mary Lynn Johnson
PO Box 965
Aurora, IL 60507 USA

> - real food with an SF theme
> e.g. Space Food Sticks, Space Noodles

One of my favorites from the book is Jupiter Jello.  (I can't remember
who came up with this, but it might have been Bob Trembley of Detroit
fandom.) It's not much work, but you have to make it on a day when
you're home for a long stretch of many hours.  Get various flavors of
Jello and a big, hemispherical bowl. Mix up a little, oh, orange
Jello-- just enough to make a centimeter or so at the bottom of the
bowl.  Allow it to set in the fridge until firm.  Then mix up a larger
amount of lemon Jello, another centimeter's worth (the bowl is
widening).  Let it set.  Repeat until you're near the top of the bowl.  

Scoop out a little bit of Jello at the edge of the bowl using a
spoon.  Mix up a tiny amount of strawberry Jello and pour it into the
cavity.  That's your Great Red Spot.  Finish up with one or two more
layers of orange, lemon, or lime.  Flip the whole assembly onto a
plate covered with lettuce.  Now you have a hemisphere of Jupiter,
complete with Red Spot and latitudinal weather bands.

Maybe I shoulda cross-posted this to sci.astro...

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     HIGGINS@FNAL.BITNET
   -   -       Internet:  HIGGINS@FNAL.FNAL.GOV
     ~         SPAN/Hepnet:      43011::HIGGINS 
From: wayne@hpfcso.FC.HP.COM (Wayne Covington)
Date: Wed, 7 Oct 1992 18:48:00 GMT
Subject: Re: The color violet?
Organization: Hewlett-Packard, Fort Collins, CO, USA
Newsgroups: sci.astro

In <1992Oct1.175712.7404@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes in part:

> As we age our eyes become less relatively sensitive to violet light due to
> degradation of the transmission of the lens. Some people who have had

This is true.  The loss happens so slowly that people don't notice it.

> prosthetic lenses implanted report restored vision in the ultraviolet (the
> ability to see more Balmer lines has been reported).

This also is true.  With just one implanted lens, things have a slightly
yellowish patina when seen through a "normal" eye as compared to the other
eye.  Your night vision is better through the implanted lens, and you don't
have the little starlike radials around a point light source at night. :-)

Wayne
Newsgroups: sci.astro,sci.space
From: dietz@cs.rochester.edu (Paul Dietz)
Subject: Re: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Organization: Computer Science Department University of Rochester
Date: Wed, 14 Oct 1992 10:52:30 GMT

In article <1992Oct14.013809.1@fnalc.fnal.gov> higgins@fnalc.fnal.gov (Bill Higgins-- Beam Jockey) writes:

> I doubt whether 3 microns is enough to be reasonably opaque, let alone
> a nearly perfect reflector (which you want when building a solar
> sail.)  I don't have a handbook handy, but I think you need dozens of
> microns of aluminum to make a good reflector.

I believe the skin depth of aluminum at optical wavelengths is in
the tens of nanometers.  You can reduce the mass still further by
drilling holes << 1 wavelength in diameter.

	Paul F. Dietz
	dietz@cs.rochester.edu
From: steinly@topaz.ucsc.edu (Steinn Sigurdsson)
Newsgroups: sci.astro
Subject: Re: UFO EVIDENCE VS. Carl Sagan
Date: 16 Oct 92 11:29:13
Organization: Lick Observatory/UCO
	<1992Oct16.010531.8396@mcshub.dcss.mcmaster.ca>
NNTP-Posting-Host: topaz.ucsc.edu
In-reply-to: fischer@physun.physics.mcmaster.ca's message of Fri, 16 Oct 1992 01:05:31 GMT

In article <1992Oct16.010531.8396@mcshub.dcss.mcmaster.ca> fischer@physun.physics.mcmaster.ca (Phil Fischer) writes:

   In article <1992Oct14.104249.18835@kth.se> TordM@VanA.PhySto.SE writes:

   >In article <1992Oct13.175901.1730@cnsvax.uwec.edu>, mcelwre@cnsvax.uwec.edu
   writes:

   >
   >>          Incident.) 
   >
   > AND the COUNTRIES that DON'T HAVE any MILITARY ??


   Just out of curiosity, which are these?

Costa Rica and Iceland for sure, maybe San Marino and Andorra,
Liechtenstein doesn't quite make it, I think they have 20 soldiers...

|  Steinn Sigurdsson	|I saw two shooting stars last night		|
|  Lick Observatory	|I wished on them but they were only satellites	|
| steinly@lick.ucsc.edu |Is it wrong to wish on space hardware?		|
| "standard disclaimer"	|I wish, I wish, I wish you'd care - B.B. 1983	|
From: pcl@oxford.ac.uk (Paul Leyland)
Newsgroups: sci.astro
Subject: Re: Observing Venus in daylight
Date: 7 Oct 92 07:35:30 GMT
Organization: Oxford University Computing Service, 13 Banbury Rd, Oxford, OX2
	6NN
In-reply-to: frank@hsr.no's message of 6 Oct 92 09:21:57 GMT

In article <1992Oct6.092157.10785@hsr.no> frank@hsr.no (Frank A Stevenson) writes:

] Venus now as a solar elongation of more than 30 degrees, and a visual
] magnitude of app. -3.3. I have been trying to observe Venus in broad daylight
] with 12x50 binoculars and after sunset. I live 59 degrees north and Venus has an
] altitude of only 3.9 degrees at sunset, and sets 30 minutes after the Sun. I
] think that conditions are unfavourable for observing after sunset.

] 	I would like to hear from people who have observed Venus in daylight
] under similar conditions in order to find out what I am doing wrong. Have I
] simply overlooked Venus or is the apperature to small. Any help would be
] appreciated.

I have seen Venus with the naked eye at 1pm local time from a latitude
of 53 North.  It isn't your aperture which is too small. Your problem
is almost certainly that you're overlooking it.  The best advice I can
give you is to calculate precisely where Venus should be at a
particular time; position yourself so that position appears to be very
close to a convenient object like a flagpole, church steeple or
whatever, and then look just there.  You might find it advisable to
test your calculations by first attempting this method (at twilight)
on a bright star easily visible to the naked eye.  Perhaps Vega, Deneb
or Altair at this time of year.

(If nothing else, it will give you good practice in converting from
RA/Dec to Alt/Az at a particular time, and in discovering the layout
of your surroundings 8-)

On the occasion I saw Venus, it had just come out of lunar
occultation; the close proximity of the moon to tell me precisely
where to look was absolutely vital.  The occultation itself was
clouded out.

Best of luck; let us know if you succeed.

Paul
--
Paul Leyland <pcl@oxford.ac.uk>          | Hanging on in quiet desperation is
Oxford University Computing Service      |     the English way.
13 Banbury Road, Oxford, OX2 6NN, UK     | The time is come, the song is over.
Tel: +44-865-273200  Fax: +44-865-273275 | Thought I'd something more to say.
From: ronnie@cisco.com (Ronnie B. Kon)
Newsgroups: sci.astro
Subject: Re: Response to PUTTING VENUS IN AN ORBIT ...  and  TIME HAS INERTIA
Date: 11 Oct 92 03:35:48 GMT
Organization: cisco Systems, Incorporated

In article <abian.718045416@pv343f.vincent.iastate.edu>, abian@iastate.edu (Alexander Abian) writes:
|>    
|>    My statements concerning PUTTING VENUS IN AN ORBIT SIMILAR TO THE ORBIT
|> OF THE EARTH  and  TIME HAS INERTIA need no further elucidation, justifi-
|> cation or proof.  They are explicit, self-explanatory and self-evident.
|> 

These are brilliant ideas, and you are absolutely right--they are so 
obvious that your present postings have fully explained them.  Any 
further postings on them would be entirely wasted: either people are
open-minded and accept your conclusions, or they are close-minded and
will just ridicule you (some more subtly than others).  Do not give
into them.  Your time could be much better spent doing more research.
Please resist the temptation to post more articles for the "guardians"
of "truth" and "reality."

You might wish to correspond with Hannu Kaarlo Juhani Poropudas
(hporopudas@tnclus.tele.nokia.fi) whose posts strike me as demonstrating
a kindred soul to yours.

-------------------------------------------------------------------------------
Ronnie B. Kon           | "Boy, they were big on crematoriums, weren't they?"
ronnie@cisco.com        |
(415) 688-4592          |           -- George Bush at Auschwitz, Sept 1989
-------------------------------------------------------------------------------
From: carroll@cs.uiuc.edu (Alan M. Carroll)
Newsgroups: sci.astro
Subject: Re: Diesen sphere or Strungen Sphere
Date: 12 Oct 92 23:08:43 GMT
Article-I.D.: m.1992Oct12.230843.19014
Organization: Technophiles Inc. - Engineers with Attitude

In article <Bw0poC.E4z@Novell.COM>, steve_olson@npd.novell.com writes:
> Does anyone know any thing about a Diesen sphere or a Strungen Sphere? 
> It is supposed to be a sphere with a star in the middle. 

Named after Freeman Dyson, who postulated it would be built by a
civilization that needed all the energy of their star. They would
therefore enclose their star in artifact in order to capture the
energy. Note that the original Dyson sphere's were not necessarily
solid - they could consist of huge numbers of small objects in
overlapping / staggered orbits. Dyson proposed them as part of a SETI
discussion involving what sort of observable signatures advanced
civilizations would have.

Larry Niven had a good article entitled "Bigger Than Worlds" that
discusses Ringworlds (of course!), Dyson spheres, Alderson disks, and
other macro-engineering projects.  Dyson spheres are reasonably common
among science fiction stories.

-- 
Alan M. Carroll          "Weren't there yams involved, too?" - J. Ockerbloom
Epoch Development Team   
Urbana Il.               "I hate shopping with the reality-impaired" - Susan
Xref: sparky sci.astro:10824 sci.space:14489