Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO381.TXT

Internet Message Format | 1993-07-13 | 33KB

Date: Thu,  5 Nov 92 05:08:29
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #381
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu,  5 Nov 92       Volume 15 : Issue 381

Today's Topics:
                          astronauts voting
                           Comet Collision
                         Gravitational assist
                          Light sails again
               MS Windows Shareware Progs via Anon. FTP
                        NASA Coverup (5 msgs)
                      Russian Engines for DC-Y?
                   Scenario of comet hitting Earth
              Space coverage on television, authenticity
            Swift-Tuttle Comet a threat to earth? (3 msgs)
                           U.N. Moon Treaty
                              Why Vote?

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
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----------------------------------------------------------------------

Date: 5 Nov 92 01:55:47 GMT
From: Patricia Gellert <[e-mail]>
Subject: astronauts voting
Newsgroups: sci.space

Do any readers know if the shuttle astronauts voted by absentee ballot?

I hope this is not considered non-topical for this newsgroup.

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

Date: 4 Nov 92 23:43:04 GMT
From: Wayne Harvey <[e-mail]>
Subject: Comet Collision
Newsgroups: sci.space,alt.sci.planetary

>In <[e-mail]> [e-mail] (John Black) writes:

>>Maybe a near comet approach could be a good thing. I did a rough calculation
>>and estimated that there must be something of the order of 10 to the power 11
>>metric tonnes of water. Maybe in 130 years time somewhere on the Earth could
>>do with some water,  <et cetera>

Here's something that people seem to be missing, that has been bandied about
by SF writers for a long time: 10^11 tonnes of water (and associated other
shit), if we could capture it and place it in Earth orbit, would provide
us with an awful lot of fuel for rockets. Perhaps we could even have fusion
rockets when the comet comes back in 130 years, and that would make for
some pretty inexpensive colonisation fuels.

Has anybody read Arthur C. Clarkes' 2051: Oddessey 3?

Cheers.
W.

--
+________________________________+ 'Life is long, and love is          _______+
|  Wayne Harvey                  | Always over in the morning'                |
|  [e-mail]   |       The Sisters of Mercy.                |
|________________________________|____________________________________________|

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

Date: Thu, 5 Nov 92 00:57:21 EST
From: John Roberts <[e-mail]>
Subject: Gravitational assist

-From: [e-mail] (Nick Haines)
-Subject: Re: Query Re: pluto direct/ o
-Date: 3 Nov 92 21:07:27 GMT
-Organization: School of Computer Science, Carnegie Mellon University

-In article <[e-mail]> [e-mail] (Del Cotter) writes:
-   >While I'm here, anyone know if a gravity assist trajectory can be used to
-   >*reduce* speed?

-   There's no end to the fun you can have playing interplanetary snooker; I
-   think the fundamental limit for any single encounter (confirmation, please?)
-   is the vector sum of spacecraft and accelerating body beforehand.

Another important factor is the maximum angle of deflection of the trajectory
of the spacecraft. This is a function of the density of the body being used
for gravitational assist - if it's very dense, the spacecraft can get
relatively close to the center of gravity of the body, and can thus make
a tighter turn.

-As I understand it, a gravity assist trajectory is simply a hyperbolic
-path around the relevant body. Such a path is characterised as
-follows:

>- the departure speed is the same as the arrival speed
>- the change in direction is larger for a closer approach
>- the higher the speed, the smaller the change in direction.

-Work out the path in the frame of the planet, then add the planet's
-velocity to all the results.

That's one kind of gravitational assist. You can also greatly increase your
delta-V by burning your fuel at closest approach on a flyby trajectory.
The quickest way to get out of the solar system using a conventional
chemical rocket is to go out to Jupiter, use a slingshot around Jupiter to
kill almost all of your solar orbital velocity, fall in toward the sun on a
very close flyby, then burn the remainder of your fuel as you pass the sun.
There's a long-term proposal for such a mission.

John Roberts
[e-mail]

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

Date: 5 Nov 92 00:06:29 GMT
From: David Goldschmidt <ida@atomic>
Subject: Light sails again
Newsgroups: sci.space

I know this has been hashed around before, but there was no mention in
the FAQL, so...

  A light sail works by light pressure (I calculate F = Power/C,=
4.66 E -6 /m^2 at 1 AU)  My question comes from what happens if you tilt
the sail.  It will red or blue shift the light just as much as a nontilted
sail, so the force on it should be the same, but is it applied in the same
direction as the light, or perpendicular to the sail?
   force            force
     | /               \  /
     |/         or      \/________>  light path
     /_____>            /|
    /|                 / |
   / | <light         /  |
  ^mirror            ^mirror

  If possible could somebody explain why it happens whichever way.  Its not
clear to me why the energy lost or gained in red or blue shifting the light
has to go into kinetic energy  (couldn't it just heat up the sail?)

  Dave Patterson,

      I'm a guest on this account, so please don't send me any flame-mail
     unless doing so will bring you eternal bliss.

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

Date: 5 Nov 92 01:51:18 GMT
From: Eric Bergman-Terrell <[e-mail]>
Subject: MS Windows Shareware Progs via Anon. FTP
Newsgroups: sci.astro,comp.os.ms-windows.apps,comp.os.ms-windows.misc,sci.edu,comp.sys.ibm.pc.misc,sci.space

Folks:

My Microsoft Windows shareware programs were recently uploaded to
simtel20 and are available for anonymous ftp:

Program Name    Filename     Ver.  Description          Req'd

Astronomy Lab   ALW113.ZIP   1.13  Astronomy program    MS Win 3.x
Anim8           ANIM8.ZIP    1.02  Animation program    MS Win 3.x
Astronomy Clock ACLOCK.ZIP   1.12  Clock for astronomy  MS Win 3.x
                                   enthusiasts
Bog             BOG.ZIP      1.05  Word search game     MS Win 3.X
FracView        FRACVIEW.ZIP 1.03  Fractal viewer       MS Win 3.x
Hangman         HANGMAN.ZIP  1.01  Hangman game         MS Win 3.x
Puzzle-8        PZL8.ZIP     1.02  8 tile puzzle        MS Win 3.x
RCALC           RCALC103.ZIP 1.03  Talking RPN          MS Win 3.1
                                   calculator
Stopwatch       SW.ZIP       1.02  Clock/stopwatch      MS Win 3.x
Talking Clock   TCLK_106.ZIP 1.06  Talking clock        MS Win 3.1

They are stored in the simtel20/windows3 directory.

If you don't have ftp access, feel free to send me a 3 1/2" or 5 1/4"
high density floppy disk in a self-addressed POSTPAID POSTPAID POSTPAID
mailer and I'll send you the programs (please include a cover letter
telling me what you want).

Eric Bergman-Terrell
Personal MicroCosms
8547 E. Arapahoe Rd.
Suite J-147
Greenwood Village, CO  80112 USA

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

Date: 5 Nov 92 00:10:14 GMT
From: Steve Linton <[e-mail]>
Subject: NASA COVERUP
Newsgroups: sci.space

The most likely explanation is that the definition of neutral point has changed, perhaps
from a stationary geocentric frame of reference to a rotating  frams locked to Earth and
Moon, oir perhaps in some other way. In this, as in most other fields of science,
notations and definitions do change with time, and often vary between authors as well.

The incidental evidence that the Moon's surface gravity is roughly 1/6 of that of the
Earth is overwhelming, and that for the inverse-square law of gravity even more so.

Also, what would be the motivation of this supposd conspiracy?

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

Date: 5 Nov 92 01:43:20 GMT
From: Anson Kennedy <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

snarfy,

You should have read the rest of Abell's book.

Your reasoning is flawed on at least two counts.

First, your math is based on a two-body problem.  The problem of
the "neutral point" is actually the "restricted three-body problem."
Your error is assuming that the only forces at work are the
gravitational forces of the Earth and the Moon.  There is another.
It's not the gravitational force of the spaceship (its mass is
so small in comparison to the Earth and Moon that it can be neglected,
which is why the problem is "restricted").  The third force is
the centrifugal force of the spaceship.  Neglecting this will
significally change the calculated mass of the Moon.

BTW, there are five points in a two body system where these forces
balance.  They are called Lagrangian points in honor of their
discoverer.  But I digress.

Second, you are thinking one-dimensionally.  You assume that the
figure given by Time magazine and Von Braun is colinear with the
line drawn from the center of the Earth to the center of the Moon.
This is probably not the case.  A spacecraft travelling from the
Earth to the Moon does not traverse a straight line.  Its path
is hyperbolic, so the "revised" neutral point you quoted will
*not*, in any case, correspond to the Lagrangian Point (normally
called L2) you attempted to base your calculations on.

Back to the drawing board for you..
--

Anson Kennedy                                                  [e-mail]
Secretary of the Georgia Skeptics (but don't even THINK I speak for them!)

"If you don't watch the violence,   \           "If I had been the Virgin Mary,
you'll never get desensitized to it." \                I would have said 'No.'"
-Bart Simpson                           \  -Margaret "Stevie" Smith (1902-1971)

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

Date: 4 Nov 92 06:20:53 GMT
From: [e-mail]
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

>>   No  they  don't  .  Abell's lunar gravity figure of 1/6 assumes the earth
>>   and moon rotate around a common barycenter. The neutral point  figure  is
>>   a direct derivation of that result.
>>
>>   My  calculations  assume the neutral point to be motionless with respect
>>   to the earth and moon . What do your calculations assume?
>>
>> snarfy
>>

   In   message-ID:  <[e-mail]>  Dennis,  University  of
      Alabama in Huntsville comments :

  >A very easy way to blow this one up is to  look  at  the  weight  of  the
  >Apollo  LM  and  the  thrust of the engine. The rocket equation says that
  >there must be at least a 1.141 thrust to weight ratio.  Remember  the  LM
  >only  had  one Ascent stage.

   Dennis ,recall my earlier comment :

>>  The issue is not necessarily whether we landed on the moon , but  how  we
>>  did it.

   I'm not trying to suggest that we didn't land on (and  return  from)  the
   moon. What I doubt is that we could have done it all with rockets.

 >  Also  remember  that the Astronauts suits and baggage were set up for 1/6
 >  g and not .6 gee.

   So  we  made  them extra heavy so the astronauts couldn't jump too high ,
   or wander off too far, right ? (see my most recent post.)

 > Henry can probably provide the numbers.

   Who's Henry?

  > If any of you out there know Buzz Aldrin, there is no way he  would  keep
  > something like this covered up.

   Probably not , sorry , gee, I guess you're right . Do you think there's a
   chance I might get to talk with your good buddy Buzz? Over the ol' modem?
   Us investigative types just like to get told off by those in  a  position
   to know , y'know ?

  >So there snarfy.

   Yeah , don't rub it in O.K.?  I'm very sensitive.

   Now  that  you  mention Buzz Aldrin, didn't I read somewhere that he went
   through severe depression and "therapy" after  his  one  moon  excursion?
   What  was  this all about?  Was he confused or upset about anything after
   this experience?

  >Also the pertubations of  Lunar  orbits  by  the  Earth  and  Sun  become
  >significant  at altitudes above 800 km and dominate above 22,000.

   Where did you read this ?  Was this a paper based on theory or the actual
   flight trajectories of real spacecraft ? If it's true , I'll be the first
   to admit that it shoots my theory ...but I'd like to see for myself.

   snarfy

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

Date: 4 Nov 92 17:25:05 GMT
From: [e-mail]
Subject: NASA Coverup
Newsgroups: alt.conspiracy,sci.space

   Dillon Pyron writes:

  >Basically, when you start on the premise that people are  lying  to  you,
  >any  argument  beyond  that  point  is  circumspect, at best.  If you had
  >stated "I've been doing some looking, and something ain't right", I'd  be
  >willing to look at your calculations with a scientific interest.  Instead
  >you  shout  that  NASA is lying and ramble on with some calculations that
  >start in mid-air and land ???

   You  don't  like  my  attitude  .   I  see  .   Not enough groveling.  My
   calculations are invalidated by my attitude. Math  has  changed  since  I
   went to school, I guess.

  > To  the point.  Your calculations assume that the earth and moon have the
  > same density, and that it is homogenous.

   Which body does your pronoun "it" refer to ?  My  calculations are  taken
   right  out  of  Abell's  pre- Apollo  astronomy  text "Exploration of the
   Universe" (Holt Reinhart, 1964) and Beiser's "Physics" (Cummings) ,1973.

   Beiser states , on page 118 , "A spherical object behaves  gravitationally
   as  if  it's  mass  were concentrated at it's center" . He also states,on
   page 119, that  the  earth's  gravitational  pull  on  an  object  varies
   inversely  with the square of it's distance FROM THE CENTER OF THE EARTH.
   I also assume that a similar rule applies to the moon.

    If  you run the computer program I wrote to facilitate the neutral point
   calculation, you can start by simply making a guess as to the minimum and
   maximum distances from the moon's center that the neutral point might be.
   The  program simply figures the relative "pulls" exerted on the object
   by both the earth and moon at increments of 50  miles  in  the  direction
   Earth -> moon. When the moon pull exceeds earth pull , the program prints
   out  the  relative  forces  in  pounds  ,and the distance from the moon's
   center where these forces exist,thereby locating the neutral point within
   50 miles. The figures derived by  the program, when a gravity  of  .1667
   (1/6)  is  entered for the pull at the moon's surface ,AGREE with the pre
   Apollo published estimates for the location of the  neutral  point.  Time
   Magazine  ,and  Werner  von Braun ,AFTER Apollo however give us a Neutral
   point figure consistent with a Lunar gravity of .64 earth.

   >Second, while you do allow for a point of zero influence, what you call a
   >barycenter does not hold up. It just doesn't move, and in  real  life  it
   >does.

    You  lost  me here. So what if the barycenter moves ? That doesn't alter
    the inverse square law for gravitational effect at a given distance.

  >Finally,  you  still  haven't  addressed  the  issue  of  the   so-called
  >conspiracy.  Why?   What  is  the  motive.   Unlike  the CIA/Mafia hit on
  >Kennedy, there is no gain in it?   And  there  are  multiple  governments
  >involved.  The Soviets (at the time) would have delighted in pointing out
  >an  error  from  NASA.

   I'll get to all this ,be patient .I'm trying to first build a  case  that
   the  gravity of the moon is about .64 at the moment . If I can't do this,
   other assertions relative to conspiracies are not supported.

  > And  I  don't understand your comments about the
  > Nipponese.

    It's not that important - forget it.

  >BTW,  who  are  you?   Do  you  have  any credentials or is astro a hobby
  >(that's not a knock) or did this come up at the local conspiracy club  (I
  >know  you  guys  meet  somewhere)?   And maybe a real name, unless you're
  >ashamed of who you are.

   I'm R&D electronics technician with bad experimental physics habit.

   I'm generally happy with and unashamed of the identity  given  me  by  my
   parents.   However  ,  given  the  possible  danger and ridicule that one
   opens oneself to when attempting to expose conspiracies on this planet  ,
   I prefer the pseudonym snarfy, at least for the time being.If this sounds
   paranoid, so be it.

   snarfy

In message-ID: <[e-mail]> ,someone else writes:

>I (and a couple others on this list that I know of) have met several of the
>people who have been there (Luna). I myself have spent time over rum and cokes
>and/or dinner with some of them. I will take first hand accounts of people
>whom I respect over any imaginative "theories". Ie, my experimental data is
>right from the mouths of those who been there. You can't get any better than
>that.

   What  I'm  alleging  is  that  ,given the astronauts not having any prior
   experience with 1/6 gravity, they may not have been able to  discriminate
   between  1/6  and  .6  ,given the suits they were wearing were of unknown
   mass.  The other problem , how the lunar liftoff was accomplished  at  .6
   gravity  , I allege that a secret technology was used, and the core proof
   of this is the neutral point distance figure, which is a direct  function
   of the earth - moon radius/distance/assumed gravity numbers.

   I  cited  two sources of this apparently revised figure ,Werner Von Braun
   and Time Magazine. If you are aware of  other  sources  giving  different
   figures , I'd like to know them.

   Also,  I  note that someone on the net has viewed a video of an astronaut
   on the moon dropping a hammer and a feather  simultaneously.  This  video
   would  be extremely pertinent in proving or disproving my allegations. If
   we knew the approximate height and fall times of  the  objects,  assuming
   the  video  was  played back in real time, we'd know the acceleration,and
   the argument would be over.

>As to your difficulties, I'm sure Paul Deitz (yet another source of respected
>opinion) can answer it if he is in a good mood and isn't overly busy.

   Great! Can I get in touch with him over the net?

   snarfy

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

Date: Tue, 03 Nov 92 17:30:53 PST
From: [e-mail]
Subject: Nasa Coverup
Newsgroups: sci.space,alt.conspiracy

   Message-ID: <[e-mail]> (David Rowland)

   <Invalid Stuff Deleted>

>I agree with the statement about the JFK files, however, know the
>"cold war" seams to be over, this does not mean we will all live
>"happy ever after".  When a super power becomes unstable, this causes
>waves throughout the world which can have more need for the NSA then
>previously.

    This is about the last sort of opinion I would expect from someone  from
   New  Zealand ,of all places. When did you get to vote on what agencies we
   need in MY government? If you want a National  Security  Agency  in  YOUR
   government  in charge of keeping embarrassing information hidden from the
   general public , you are more than welcome to start lobbying for one over
   there. None of my business.  I suggest you mind yours.

     As  far  as  "Invalid  Stuff  Deleted"  goes , I think I when one cites
   something as being invalid , it is incumbent upon that person  to  assert
   reasons  , arguments , etc detailing just what it is he feels is invalid.
   Otherwise what you end up with amounts to nothing more than an insult.

     If you'd like to trade insults I think you've just bitten off more than
     you might be willing to chew ,MATE.

   snarfy

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

Date: Thu, 5 Nov 1992 00:43:12 GMT
From: Bruce Dunn <[e-mail]>
Subject: Russian Engines for DC-Y?
Newsgroups: sci.space

> Brad Whitehurst writes:
>
>         Av. Week had a second article on the NPO RD-701, a tri-fuel
> engined which burns kerosene, LOX, and LH2, with continuously variable
> fuel transition from kerosene to LH2.  Is this to customize the rocket
> performance as a function of altitude, load, etc.?  The thrust figures
> for all kerosene were significantly higher than with pure LH2.


        This makes the RD-701 a "tripropellant" engine.  Numerous design
studies done in the US have shown that using a tripropellant engine can lower
the dry mass of SSTO vehicle by a modest amount.  The engine uses mainly
kerosene/LOX during the early part of the flight, when specific impulse is
not so important, and thrust and propellant density is very important.  Later
in the flight, the engine switches to LH2/LOX because specific impulse
becomes more important than thrust level and propellant density.
      The upper stages of multi-stage vehicles or the later parts of SSTO
flights are critically dependant on specific impulse, because all the
propellant for these sections of the flight has to be boosted to several
thousand meters per second before use.  If a given lower stage can only boost
say 100 tons of propellant to say 6000 meters per second, then it is far more
useful to have 100 tons of LH2/LOX than 100 tons of kerosene/LOX at this
velocity.  Propellant burned however at the beginning of a flight does not
have to be boosted through any great velocity increment and its specific
impulse therefore is not too important.  However for an SSTO vehicle, the
tank for the early-burn propellant still has to be boosted all the way to
orbit, therefore it pays to have a dense propellant combination.  In this
case, kerosene/LOX wins over LH2/LOX.
        The design studies generally show about a 20 to 25% reduction in dry
mass by using a tripropellant engine in an SSTO.  However, this reduction
comes at the price of a 50% increase in the number of propellant tanks,
piping systems, valves, and turbopumps, as well as the need for a complicated
combustion chamber and/or nozzle arrangement to handle the two fuels.  The
Aerojet Corp. did a number of design studies on a "dual expander"
propane/LH2/LOX engine, but to my knowledge never built such an engine.





--
Bruce Dunn    Vancouver, Canada   [e-mail]

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

Date: Wed, 04 Nov 92 14:43:04 GMT
From: Cameron Newham <[e-mail]>
Subject: Scenario of comet hitting Earth
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:

 >
 > [e-mail] (Cameron Newham) writes:
 > >So, we nuke the comet which in turn would cause lots of radioactive
 > >debris to fall to earth over a large area.
 >
 > Wrong.  There would be very little induced radiation, and most of the
 > radioactive material from the bomb would expand in space and miss the Earth.

Wrong.  Do you know what fallout is?  It is dust sucked up at the hypocenter
of a nuclear explosion that becomes radioactive and later falls to earth.

I think you would find pieces of your comet to be tainted with radioactivity
also.

 > As has been pointed out, yes and no.  They aren't going to outgas (so no
 > trick shots) but they'll hold together under a significantly firmer "push"
 > (so you could detonate the nuke quite close for a larger delta-V).

I get the feeling that there has been a serious over-estimate of the ability
of a nuclear warhead to significantly change the delta-v of an asteroid.
Project Icarus (from what I remember) suggested exploding a device at
the aphelion point so as to move the asteroid away from the earths orbit.
I can't recall anything about doing it "near" the earth.  Anyway, this
would only work if the object was small.

Also, has anyone addressed the problem of guiding such a device to the
precise point at short notice?  What if the object is travelling
retrograde?  A doubt you could lob a nuclear device at an asteroid/comet
with sufficient accuracy.  Especially if we are talking combined
velocities of >30 Km/s.

(and before you point it out - yes, I know asteroids all appear to be
travelling prograde.  There are, without doubt, exceptions.  Just a matter
of finding them. ;)


- cameron.

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

Date: Wed, 4 Nov 92 23:07:56 EST
From: John Roberts <[e-mail]>
Subject: Space coverage on television, authenticity

-From: [e-mail] (Bill Higgins-- Beam Jockey)
-Subject: Re: NASA Coverup
-Date: 4 Nov 92 15:22:43 GMT

-In article <[e-mail]>, [e-mail] () writes:
-> Gravity can be mathematically derived
-> from physical observations.  Case in point:
->
-> Monday night on PBS, there was a special on Space Exploration which showed an
-> interesting experiment.  One of the astronauts dropped a hammer and feather
-> at the same time to show that Galieo was right.
-[...]
-> d = Distance object travels
-> a = acceleration due to gravity
-> t = time it takes to drop.
->
->     d = 1/2at**2   or    a = 2d/t**2

-Hidden assumption:  this film is playing back on your TV set at the
-same speed it was photographed.  (Or is it video?)  In any case, you
-need to know the correct frame rate to get an accurate value for t, and
-even then you will have some irreducible error in the measurement,
-thanks to the discrete time resolution of film and video.

It was video, which many people remember as being broadcast live. Looking at
the video at full speed and a frame at a time, it looks pretty realistic.
Assuming for the moment that the video is authentic, the release appears to
be from very close to four feet up, and the fall from release to impact is
~36-37 frames (at a presumed 30 frames/second for NTSC standard). That
works out to lunar gravity of around 1/5.8 to 1/6.1 Earth gravity. I
suppose it would have been possible to film it in a large vacuum chamber
on Earth, with movie film running at 75 frames/second (or maybe 150 - my
VCR doesn't advance half-frame), then transcribe it slowed down onto video,
but it would be very difficult to get the astronaut to move at 2.5 times
normal rate and to sync the voice to the body movements.

Some of the lunar rover video would essentially be impossible to film
on the Earth.

By the way, "Space Age" is a great television series. Some of the nitpickers
might complain that their particular viewpoint didn't get full coverage,
but they seem to try to have pretty good representation of the the views
they do cover. There's plenty that the general public doesn't generally
see (at least those who don't have NASA Select :-), including some really
spectacular video. (I've been meaning to post a summary of what's been

shown, but there's so much to include that it will be a major undertaking.)

With this six-part series running now, and "Inside Space" on the Sci-fi
Channel, this is really a great time for space coverage on TV. (The Thursday
episode of "Good Morning America" is scheduled to show an item on NASA
selection of a rover for use on Mars.)

John Roberts
[e-mail]

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

Date: Thu, 5 Nov 1992 00:53:25 GMT
From: Paul A Daniels <[e-mail]>
Subject: Swift-Tuttle Comet a threat to earth?
Newsgroups: sci.astro,sci.space

long this thread all sorts of figures have been mentioned, does anyone
have an estimate of how much kinetic enery would be required to actually
shatter the earths crust? Yes I do mean major doom and gloom, and a few
more continents.
    Geologists belive that the earth originally had a super continent
don't ask me to spell it's name. I'm just curious, could it have broken
up due to a meteor stike?

Paul.

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

Date: Thu, 5 Nov 1992 00:36:37 GMT
From: Paul Dietz <[e-mail]>
Subject: Swift-Tuttle Comet a threat to earth?
Newsgroups: sci.astro,sci.space

In article <pad.720924805@probitas> [e-mail] (Paul A Daniels) writes:

>long this thread all sorts of figures have been mentioned, does anyone
>have an estimate of how much kinetic enery would be required to actually
>shatter the earths crust? Yes I do mean major doom and gloom, and a few
>more continents.
>
>    Geologists belive that the earth originally had a super continent
>don't ask me to spell it's name. I'm just curious, could it have broken
>up due to a meteor stike?


Um, it's already shattered, in many places.  Rock on the scale of
a planet does not act like an eggshell.

It is thought that continents break up because of upwellings in
the mantle which pull the plates apart.  This process, rifting,
continues today (near the Red Sea, for example).

The supercontinent to which you are refering is only the latest of
many.  The cycle that assembles and dissassembles the continents is
thought to have gone through tens of cycles since the earth was
formed.

    Paul F. Dietz
    [e-mail]

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

Date: 5 Nov 92 02:24:55 GMT
From: Tarl Neustaedter <[e-mail]>
Subject: Swift-Tuttle Comet a threat to earth?
Newsgroups: sci.astro,sci.space

In article <pad.720924805@probitas>, [e-mail] (Paul A Daniels) writes:
> does anyone have an estimate of how much kinetic enery would be required
> to actually shatter the earths crust?

The crust isn't exactly a solid. It's more akin to some light scum floating
on top of the semi-fluid mantle. The convection currents in this underlying
mantle drag along the light silicate scum that makes up the continents.

For comparison in terms of size, think of the earth being about the size
of a basketball. The continents (at that scale) are less than a millimeter
thick. Rocks (i.e., planetary crust) are plastic at the large scales
(distance and time) used in planetary geology, and behave pretty much like
silly putty. So, the term "shatter" doesn't apply.
--
         Tarl Neustaedter    [e-mail]
         Marlboro, Mass.    Stratus Computer
Disclaimer: My employer is not responsible for my opinions.

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

Date: 4 Nov 92 15:41:52 CST
From: [e-mail]
Subject: U.N. Moon Treaty
Newsgroups: sci.space

   There is susposed to be something in international law about any country
over which the Moon passes directly (plumb) has some kind of claim but I'm
having a hard time tracking the particulars.

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

Date: 4 Nov 92 22:07:10 GMT
From: Bob Blackshaw <[e-mail]>
Subject: Why Vote?
Newsgroups: talk.abortion,soc.motss,sci.space

In <[e-mail]> [e-mail] (David Knapp) writes:

>In article <[e-mail]> <[e-mail]> writes:
>>                              WHY VOTE?
>>
>>The reward of a thing well done
>>is to have done it.
>>          --Emerson
>>                                      One never notices what has been done;
>>                                      One can only see what remains to be done.
>>                                                      --Marie Curie

Well, quite apart from being able to express my opinion in the
most forceful way available, there was the reward of knowing
that the control freaks must have been gnashing their teeth
last night as the returns came in on Maryland's Question 6.
Even greater was the satisfaction that in some small way we
had given our womefolk their due. [62% for, 38% against]

>Etc.

>Voting is really only useful for getting those people off your back who
>believe that if you *don't* vote, you shouldn't complain about the
>current state of goverment.

>Clearly, an individual's vote doesn't matter at all as evidenced by the
>way the election turns out whether they vote or not. Voting is a symbolic,
>not a functional, act.

Interesting thought - suppose we had *all* stayed away yesterday,
who would have won? As long as people feel this way, the entrenched
groups can lead us about by the nose. Incidentally, I also voted
against term limits, mainly because I think Alexander Hamilton and
James Madison, and John Jay were smarter than George Will.

>Until we get rid of the electoral college, the individual vote will *always*
>be discounted and we will not be living in a democracy.

Odd? I thought Clinton and Gore won the popular vote too? Did I
read the numbers wrong? :-/

>It is very true that we live in a _democratic republic_, but which do *you*
>value more, the democratic part, or the republic part?

Well, both kinda. Yes, its a wierd form of government, but it
seems to work pretty good. As Bill Bairnsfather's Old Bill would
have said "if yer knows a better 'ole lad, go to it".




>--
>David Knapp                                      University of Colorado, Boulder
>Perpetual Student                                   [e-mail]

Sorry for the digs David, but its only old men like me that
are supposed to be so cynical and jaded in outlook. :-)

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End of Space Digest Volume 15 : Issue 381
------------------------------