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Subject: SPACE Digest V11 #309

SPACE Digest                                     Volume 11 : Issue 309

Today's Topics:
           Re: Titan (Questions about the Voyagers)
              Re: Dyson spheres?
                Re: Our galaxy
                Re: Our galaxy
              Re: Dyson spheres?
              Re: Dyson spheres?
              Magellan Update - 04/17/90
Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things)
              Re: Fermi paradox
              Re: Dyson spheres?
----------------------------------------------------------------------

Date: 24 Apr 90 00:53:31 GMT
From: amelia!wilbur.nas.nasa.gov![e-mail]  (Eugene N. Miya)
Subject: Re: Titan (Questions about the Voyagers)

In article <[e-mail]>
[e-mail] writes:
>At the time Titan was considered to be a good candidate for the
>most interesting body in the solar system (other than Earth, of course)
>since it was known to have an atmosphere, wasn't a gas giant, etc.
>In fact, it turned out to be relatively bland and featureless.

Titan is still regarded as "interesting."  This flyby began the proposal
for a candidate Titan imaging radar fly by.  It just depends on who's
interest you have.  Now whether this proposal ever gets funded is
another matter.  (Doubtful.) I think Mike would rather go up an a payload
specialist on another SIR (Shuttle Imaging Radar) mission.  Limited time.

--e. nobuo miya, NASA Ames Research Center, [e-mail]
  {uunet,mailrus,other gateways}!ames!eugene

------------------------------

Date: 23 Apr 90 17:14:43 GMT
From: deimos.cis.ksu.edu!uafhp![e-mail]  (Brian L. McCormick)
Subject: Re: Dyson spheres?

In article <[e-mail]>, [e-mail] (Steve Robiner) writes:
>
> A civilazation that advanced would surely not need a star as an energy source.
> In order to move that much mass around you would have to have a very advanced
> energy source already.  And since such a sphere would have no 'gravity' or
> other centripital forces at its poles, and no 'night' anywhere on the surface,
> the simple creation of another planet would be far more preferable.
>
> If they were that advanced, they'd surely contruct the sphere out of materials
> which fully absorbed all the energy from the star in *every* wavelength.  We
> would never see it even if they did exist.

I agree that a civilization that advanced would not need a star as an energy
source, but would quibble with some of the points made above.  First of all,
if a civilization needed a Dyson sphere, another planet simply wouldn't
do.  It wouldn't provide enough living space.  Secondly, a Dyson sphere
would have to radiate.  If it didn't, the energy it trapped by it would
quickly bake the inhabitants.  It might be possible to use a small black
hole orbiting inside the sphere as a heat sink, but this probably wouldn't
be as simple as just radiating the heat from the outside.

Actually, I think that the best solution would be to build large numbers
of solar orbiting space cities.  On this scale, it is possible to get the
total living space of the Dyson sphere, without having to create an
enormous solid structure, or developing non-centrifugal artificial
gravity (something that I think is somewhat improbable).  It also has the
advantage that no single disaster (except a supernova) would affect all
of the system's inhabitants.

----------------------------------------------------------
Brian McCormick                    [e-mail]
University of Arkansas         or [e-mail]
----------------------------------------------------------
The opinions presented herein are subject to disclaimation
----------------------------------------------------------

------------------------------

Date: 23 Apr 90 19:01:37 GMT
From: hplabsb![e-mail]  (David Smith)
Subject: Re: Our galaxy

In article <[e-mail]> [e-mail] (Will Martin) writes:
>The radio program "Stardate" that was aired on Sunday, April 22, described
>our galaxy as a spiral like Andromeda.
> Or was this "Stardate" based on obsolete data?

Well, recent articles in Sky&Tel, Astronomy, and Odyssey say that some new
results indicate that the Milky Way is a mildly barred spiral.  Still a
spiral, but "like Andromeda" may be inappropriate.

>In a related topic, is there any "better" name for our galaxy than "the
>Milky Way"?  Something that sounds more like a proper name and is more
>dignified?  ... "number 1 in the local group" ... perhaps ... Latinized...

I don't think "Milky Way" is undignified, or any less dignified than its
name in any other language.  I don't see that a number is particularly
dignified.  Besides, if we changed the name of the Milky Way, we'd
also have to change the name of the nearby Snickers galaxy.  :-)

Maybe we'll have to change it when the feared grzhqlons from Snickers
show up demanding a change.  But then, they might object if we claimed to
be #1, too.
--
    David R. Smith, HP Labs
    [e-mail]
    [phone]

------------------------------

Date: 24 Apr 90 00:09:01 GMT
From: ogicse!blake![e-mail]  (Scott Cameron)
Subject: Re: Our galaxy

> Is there *any* Earth language that has a name for the planet that is
> different than the word for "soil" or "ground"?

If I remember my frosh Russian correctly, when Lenin and Co. remodeled the
language, the word for Earth became "Mir" -- same as the word for "peace".

(Corollary:  What does Mikhail *really* mean when he says that all he wants
is "peace"? ;] )

>
--
S.D. Cameron   | "...the right of the PEOPLE to keep and bear  |  AOPA | 50 yrs
Univ. of Wash. | arms shall not be infringed." -- U.S. Const.  |      -+-
Seattle WA     | "I know I promised, but ... " -- Geo. Bush    | _____(*)_____
[e-mail] |   My opinions, not theirs   |    WingNut

------------------------------

Date: 23 Apr 90 20:00:48 GMT
From: convex![e-mail]  (Edward V. Wright)
Subject: Re: Dyson spheres?

[e-mail] (Steve Robiner) writes:

>If they were that advanced, they'd surely contruct the sphere out of materials
>which fully absorbed all the energy from the star in *every* wavelength.  We
>would never see it even if they did exist.

Only if they had found some way to cirumvent the laws of thermodynamics.
Otherwise they have to radiate at *some* frequency to get rid of waste
heat.

(Of course, if they were trying to hide from someone, they might find a
way to do this directionally, a la David Brin's "refrigerator laser," in
order to minimize the probability of detection.)

------------------------------

Date: 23 Apr 90 17:34:23 GMT
From: swrinde!zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Dyson spheres?

In article <[e-mail]> [e-mail] (Steve Robiner) writes:
>A civilazation that advanced would surely not need a star as an energy source.

Um, just what would it use for an energy source?  Stars are actually fairly
convenient as such things go.

>In order to move that much mass around you would have to have a very advanced
>energy source already...

A small fraction of the star's output, applied well, would suffice.

>And since such a sphere would have no 'gravity' or
>other centripital forces at its poles, and no 'night' anywhere on the surface,
>the simple creation of another planet would be far more preferable.

If the surface area of a single planet will satisfy you, sure.  You only
build a Dyson sphere if you want lots more than that.

Incidentally, you can't build a Dyson sphere as a solid object, at least
not without some really wild materials.  Dyson's original proposal specified
a shell of roughly planet-sized plates in independent orbits rather than a
solid object.

>>    Dyson  recognized that an Earth-based observer would  see  a  very
>>    bright infared source with no visible component.
>>
>If they were that advanced, they'd surely contruct the sphere out of materials
>which fully absorbed all the energy from the star in *every* wavelength.  We
>would never see it even if they did exist.

The infrared is not from the star.  Unless they've repealed the second law
of thermodynamics, they *will* have waste heat and will have to radiate it.
--
If OSI is the answer, what on |     Henry Spencer at U of Toronto Zoology
Earth could be the question?? | uunet!attcan!utzoo!henry [e-mail]

------------------------------

Date: 23 Apr 90 16:35:55 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 04/17/90



                   MAGELLAN STATUS REPORT
                       April 17, 1990


          The Magellan spacecraft is 104 million miles from
Earth and 34 million miles from Venus today and continues its
cruise with all subsystems performing nominally.

          The spacecraft is traveling at 63,320 mph relative
to the sun and closing on Venus at 35,415 mph relative to
that planet.

          Last week ended with a successful Attitude
Reference Unit Calibration (ARUCAL), the first of the mission
after two previous aborted attempts. The tape recorded ARUCAL
data will be analyzed later this week.

          All star calibrations during the week were successful with
an average attitude update of 0.04 degrees. Two Deep Space
Network readiness tests were successfully supported.

          SPACECRAFT
          Distance from Earth (mi)             103,621,828

          Velocity Heliocentric                64,233 mph

          One-way light time                   9 mins, 16 secs

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

------------------------------

Date: 23 Apr 90 12:09:43 GMT
From: rochester!rit!cci632![e-mail]  (Lance Michel)
Subject: Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things)

In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
>vsi1!hsv3![e-mail]  (Mike Van Pelt) wrote:
>
>>Nope, "Silent Running" goofed, too.  The nuclear explosions, though
>>visually very good, made noise -- the "bang" *BEFORE* the flash!  I
>>could accept some kind of tenuous shock wave hitting the ship some time
>>after the explosion, but *BANG*FLASH* is just stupid.

Whoa!  Hold on there.  I have this movie on tape (It's my absolute favorite),
and my version has ZERO noise which is why I like it so much.  Several other
technical "pit-falls" like robots with too many human qualities was another
area they dealt with very well.  They only thing they didn't handle well was
gravity.  (Where did it come from?)

Well enough rambling, this probably doesn't belong in this group at this point.
Take this to another group and I'll be happy to post more.

 ___________________________________________________________________________
|                                                        |  Lance Michel    |
|   "If you fall I will catch you, I will be waiting..." |  [e-mail] |
|___________________________________________C._Lauper____|__________________|
          (Song stuck in my head at the moment)

------------------------------

Date: 23 Apr 90 14:41:00 GMT
From: sdd.hp.com!apollo![e-mail]  (Steve Rehrauer)
Subject: Re: Fermi paradox

In article <[e-mail]> [e-mail] (Richard A. Schumacher) writes:
>Of course the simplest answer is that They don't exist.
>
>Consider recent computer simulations of impactors on earth-sized
>bodies. Most planets that would have been earthlike either end
>up like Venus (too few/too small impacts) or Mars (too many
>impacts): they have the wrong kinds of atmospheres to evolve
>organic life. Earth may well be unique in this galaxy.

Again I ask: Why does everyone seem to assume that life inevitably
leads to a technological society?  The vast majority of our planet's
inhabitants get along quite well without styrofoam, 60Hz power or
radio astronomy, thanks.  Doesn't it seem more likely that the
galaxy is fairly thick with planets populated with nought but algae
and bacteria; has a smaller number of systems that evolved complex
multicell forms; and may well have only a handful of places in which
creatures have the capacity to wonder where everyone else is?
--
   >>"Aaiiyeeee!  Death from above!"<<     | (Steve) [e-mail]
"Spontaneous human combustion - what luck!"| Apollo Computer (Hewlett-Packard)

------------------------------

Date: Mon, 23 Apr 90 11:02:57 CDT
From: [e-mail] (Mahan)

>Date: 20 Apr 90 17:45:14 GMT
>From: nuchat![e-mail]  (Steve Nuchia)
>Subject: Re: Drake Equation (was Re: Interstellar travel)
>
>In article <[e-mail]> [e-mail] (Andrew Pettifer) writes:
>>What about all those 50Hz power grids?
>>They would cause some beat frequencies, and i'm sure that the phase
>>relationships are drifting all the time, which would help to make the signal(?)
>>seem more random.
>
>The 10 Hz beat would be interesting.  The phase relationship
>probably doesn't change very much, since most grids are phase-locked
>to a coordinated time base.  The time bases are stable enough that
>a simple AC line-synchronous mechanical clock is more accurate than
>most quartz crystal time bases (ie, watches).  As long as they don't
>lose power.

     The power grids in the US do NOT maintain an exact frequency of 60 hz.
The generators are allowed to change speed in response to changing loads and
the frequency is typically slightly below 60 Hz.  The heavier the load the
slower the system runs.  In the eastern intertie (eastern US and part of
Canada) the missing cycles are made up between midnight and 1 AM eastern time
by running the system slightly fast.  The Pacific system makes up the
difference during the first ten minutes of each hour, starting on the hour.  I
never did find out what the Texas grid did.

     As long as there are 5,184,000 cycles per day a synchronous clock will
maintain good long term average time.  However, tracking the power grid can be
10-15 seconds off at various times during the day.

     An attempt was made many years ago to make the eastern intertie
isochronous by frequency locking a master generator.  The master station was
somewhere near Tennessee.  The attempt was a failure and was abandoned in favor
of the previously used (and still current) system.

     50 Hz 220 V power is almost optimal to cause cardiac fibrillation.
Voltages in the thousands and above tend to cause localized burning and
charring of tissue, which insulates and stops the current flow.  Lower voltages
(low tens and below) generally do not push enough current into the body to be
dangerous.  However, there is NO THEORETICAL MINIMUM on the amount of
energy necessary to disrupt the cardiac rythom if it is applied in the
right place at the right time.

     3 to 4 PSI is enough to rupture the alveoli and force air out into the
chest cavity (pneumothorax).  From there it can do many unpleasant things.


Stephen Mahan
US Navy certified diver
Electrical Engineer
Naval Coastal Systems Center
Panama City, FL   32408
[e-mail]

------------------------------

Date: 23 Apr 90 09:33:10 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Dyson spheres?

One Dyson sphere might radiate visible infrared, but build enough
concentric Dyson spheres and little waste might escape.

--
Perestroika: could   \O\     Tom Neff
 it happen here?      \O\    uunet.uu.net!bfmny0!tneff

------------------------------

End of SPACE Digest V11 #309
*******************