Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_2/V11_279.TXT

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Subject: SPACE Digest V11 #279

SPACE Digest                                     Volume 11 : Issue 279

Today's Topics:
       Re: Drake Equation (was Re: Interstellar travel)
             Fermi Paradox: Deadly Probes
              Re: Israeli Space Program
              Re:  SPACE Digest V11 #268
              Re: Fermi Paradox
           Re: The effects of decompression
      Re: Listening to the Star (was RE: Drake Equation)
              Re: Arecibo (sp?) message
            National Space Society debate
          Re: Earthbound Asteroid.....trying again!
----------------------------------------------------------------------

Date: 17 Apr 90 16:26:06 GMT
From: att!cbnewsl!moss![e-mail]  (Forrest Gehrke,2C-119,7239,ATTBL)
Subject: Re: Drake Equation (was Re: Interstellar travel)

In article <[e-mail]>, [e-mail] (Dan Tilque) writes:
>
> Since we've been listening to the sky at radio frequencies for > 40
> years now and haven't discovered any alien generated signals, it's
> probably safe to say that there are no civilizations like ours within
> that 50 ly radius.  This seems to be better limiting data than the
> results of the Drake equation.

Who is this "we" that has been listening?  And with what?  These
signals are not going to be picked up on a boombox with the
announcement the signal is from outer space.

I have seen these postings saying that our radio signals have been
going out for 40 or 50 years.  That puts us back to 1940 or 1950.
Anyone heard of Heinrich Hertz or Marconi?  80 or 90 years would
be more accurate.  But the point is, we really haven't been
listening.  It is only in the last decade or two that there have
been sufficiently sensitive receivers and antennas available to
listen.  But if these installations picked up such a signal it
would be mostly accidental.

On another tack--let's assume there is an intelligent life out
there about 50 ly.  Let's also even assume their evolution was on
the same time track.  So they discover radio. The easiest wavelength
is the same as with us: long waves.  Who is listening below 200
meters?  Besides which, our earth's atmospheric racket would
drown out any signals that might possibly be on those frequencies.
(Assuming these signals were coming at us straight on so that
there would be a minute chance of getting through our ionosphere).

But even at UHF and microwave frequencies (which can make it through
our ionosphere), this is a dauntingly wide spectrum to be
attempting to cover simultaneously (let alone doing it in all
directions).  It is also a daunting problem to discriminate against
the signals being caused to be transmitted by ourselves.

I don't believe it has been proved there is no intelligent
life within a radius that our radio signals have been going
out, simply because we haven't heard anything come back we
could identify as non-earth related.  I pick this time period
only because we would have to have been detected by some
intelligent life for this life to direct its antennas at us.

We really haven't been listening.

Forrest Gehrke [e-mail]

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

Date: 18 Apr 90 00:25:50 GMT
From: vsi1!hsv3![e-mail]  (Mike Van Pelt)
Subject: Fermi Paradox: Deadly Probes

In article <[e-mail]> [e-mail] (Tom Neff) writes:
>One possible explanation for the Fermi paradox that nobody can disprove
>is that when you achieve interstellar travel, somebody comes and kills
>you.  Let's hope that's not it.

Or, when you achieve radio somebody comes and kills you.  I think Dr.
Benford did an analysis of this possibility (plus a novel or three):
Some really paranoid BEM out there decides that allowing other
technological life forms to develop is an Unacceptable Risk.  So they
build self-replicating robots which listen for radio signals of
intelligent origin, and when they detect them, go and destroy the
senders.

Of course, the BEMs had better be *real* sure the technology of their
"deadly probes" is sufficient to deal with said technological life
forms when they finally get there, because an unsucessful attempt at
planetcide is bound to get the victims upset -- and they might come
looking for the perpetrators.

If so, what should we look for?

(My random signature of the day seems especially appropriate...)
--
Mike Van Pelt          | What happens if a big asteroid hits Earth?
Headland Technology    | Judging from realistic simulations involving a
(was: Video Seven)     | sledge hammer and a common laboratory frog, we
...ames!vsi1!v7fs1!mvp | can assume it will be pretty bad. -- Dave Barry

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

Date: 16 Apr 90 23:59:02 GMT
From: voder!nsc![e-mail]  (Amos Shapir)
Subject: Re: Israeli Space Program

In article <[e-mail]> [e-mail] (Ben Burch) writes:
>
>They demand-launched a satellite a week or so ago in response to some
>Iraqi saber-rattling.  I was a bit amazed that they were able to do
>this.  Either they have the kind of "Go and do it" attitude that NASA
>once had, or they were almost ready to launch in the first place.

I don't think Iraq's saber-rattling had anything to do with it.  By the
little that I know of the Israeli space program, launches are as prone
to delays and as unpredictable as any other program's, especially since this
is only the second satellite ever launched.

--
    Amos Shapir
National Semiconductor, 2900 semiconductor Dr.
Santa Clara, CA 95052-8090  Mailstop E-280
[e-mail] or [e-mail]

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

Date: 17 Apr 90 17:15:47 GMT
From: snorkelwacker!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re:  SPACE Digest V11 #268

In article <[e-mail]> [e-mail] writes:
>> Exploring from a central point, this would be true.  But it shouldn't
>> take more than a thousand years at most for a major colony to become
>> a starfaring civilization itself.
>
>Take for example the human outpost on the planet Earth. After a recorded
>history of nearly fifty thousand years, after a developmental stage that
>may have been as long as 3,000,000 years, the human race is no closer to
>interstellar travel than was Og, neanderthal stone-user...

Colonies started by a starfaring, technological race do not have to build
themselves up from the stone-tool stage.  They would start with most or all
of the parent civilization's technology.  Barring major problems, the only
delay would be building up the industrial infrastructure needed to make
that technology work, and growing enough to be wealthy enough to contemplate
building starships.

Most of our civilization's infrastructure and wealth has grown up in the
last century or less.  There are people alive today who remember a time
when man could not fly, radio did not exist, and two-way intercontinental
travel was a luxury available only to the rich.

And I don't recall seeing many design studies for starships dating from
Og's time, while there are plenty around today...  Some of them might be
buildable (although probably too expensive) within a few decades.
--
With features like this,      |     Henry Spencer at U of Toronto Zoology
who needs bugs?               | uunet!attcan!utzoo!henry [e-mail]

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

Date: 17 Apr 90 21:09:19 GMT
From: zephyr.ens.tek.com!tektronix!sequent!mntgfx![e-mail]  (Kendall Auel)
Subject: Re: Fermi Paradox

In article <[e-mail]> [e-mail] (Mark Gellis) writes:
>
>My own candidates for the solution to the Fermi Paradox are as follows:
>
>1) We actually are alone.  (Or at least, we are the first technically
>advanced civilization in the galaxy.)
>
>2) There is no way around the lightspeed limit and intelligent civilizations
>are fairly uncommon.
>
Imagine how life on Earth would appear to Neptunians.  Very hot, fast-moving,
short-lived creatures, stuck on a tiny rock whipping around the sun.  In
contrast, the Neptunians would be large, nebulous, drifting globs of liquified
gases.  Earth life reproduces at a blinding rate, and no single individual
lives very long at all.  Even the oldest tree on Earth is just a few dozen
Neptunian years old.  So, it makes sense that life on Earthlike planets
will develop much more quickly than on the large gas giants or their moons.

We may not be alone, but it is not too hard to imagine that we are among
the first intelligent life forms in the galaxy.  Also, we may be blinded
by our assumptions about what intelligent life looks like and how it
behaves.  Humans are very Chauvinist when it comes to carbon and water.

--
Kendall Auel       |   Mentor Graphics Corporation  |  Ich bin ein Berliner
[e-mail]   |   Silicon Design Division      |  "I am a pastry"

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

Date: 17 Apr 90 15:21:30 GMT
From: zaphod.mps.ohio-state.edu!samsung!umich!ox.com!itivax!vax3.iti.org![e-mail]  (Allen W. Sherzer)
Subject: Re: The effects of decompression

In article <[e-mail]> [e-mail] (Brian or James) writes:

> I believe that tests exposing humans to a soft vacuum were done
>by Nazi Germany.

Yep. Goering wanted information on the effects of high altitude
on unprotected pilots. Goering also wanted information on the effects
on pilots who ditch in cold water to see what sort of protection they
would need. This lead to the hyperthermia experiments. There is an account
of this in "The Rise and Fall of the Third Reich". Pretty gruesom chapter.

>The impression I have is that these tests were
>done to destruction of the human subject,

Sometimes. More often, it was just done over and over to the same person.
Many survived the experiments but all were killed afterwards.

What a swell bunch of guys.

  Allen
-----------------------------------------------------------------------------
| Allen W. Sherzer         |         If guns are outlawed,                  |
|   [e-mail]            |         how will we shoot the liberals?        |
-----------------------------------------------------------------------------

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

Date: 17 Apr 90 05:06:55 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Listening to the Star (was RE: Drake Equation)

In article <[e-mail]> [e-mail] (Philip Nettleton) writes:
>The point that people are forgetting is the impracticality of advanced
>civilisations using radio signals, especially if they're technologically
>advanced enough to have colonised other worlds and thereby need to keep in
>contact. We are acting like American Indians a couple of hundred years ago
>looking for smoke signals from a neighboring tribe to indicate they're
>presense when they're using CB radios.

If those Indians were sitting in the forest today looking for smoke
signals as a sign of "they're presense" [good thing we have Universities
on the net isn't it] they would not catch our CB radios...  but they'd
see our contrails!

The point is that civilization tends to add new media, not eliminate old
ones.  We will surely still be emitting RF of identifiably sentient
origin many centuries from now.

In fact the only reason I can think of that we'd stop emitting radio
would be DELIBERATELY, to avoid cluttering up the aether with our
noise... perhaps for the sake of astronomy, perhaps out of some highly
advanced sense of environmental awareness... or perhaps to HIDE from
something NASTY out there!! :-)

--
War is like love; it always      \%\%\%   Tom Neff
finds a way. -- Bertold Brecht   %\%\%\   [e-mail]

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

Date: 17 Apr 90 15:53:24 GMT
From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Arecibo (sp?) message

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>   My question: why wasn't the message sent to closer stars, since cost
>couldn't have been an object? Was it fear of space invaders? ...

It was basically a symbolic gesture as part of the ceremonial commissioning
of some new equipment, as I recall, and so optimizing the choice of target
wasn't important.  Also, bear in mind that Arecibo is not steerable to any
great extent, so they needed a target that would be in the field of view
during the ceremony.
--
With features like this,      |     Henry Spencer at U of Toronto Zoology
who needs bugs?               | uunet!attcan!utzoo!henry [e-mail]

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

Date: 17 Apr 90 14:31:02 GMT
From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!IDA.ORG!pbs![e-mail]
Subject: National Space Society debate


     I feel the ongoing "discussion" about the National Space Society could use
some background information at this point.  This organization is the result of
a merger of the National Space Institute and the L5 Society.  Some of the
original L5ers were not particularly happy with this development and came
kicking and screaming into the expanded organization.  Besides disinformation
campaigns launched by a few disgruntled diehards from that quarter, NSS has
also been subjected to some snipping from the PLANETARY SOCIETY chiefly over
the question of manned vs. unmanned exploration of the cosmos.  Just as NSS has
sometimes been closely linked with NASA HQ because of the geographical location
of its main offices, so too can the Planetary Society be linked with JPL and
CalTech on similar grounds.
    All of this factionalism is missing a big point.  I don't care if you
belong to NSS, but I do hope you belong to SOME group.  There is much work to
be done if we are to move out into the vast ocean of stars around us.   We all
need to work together and yes, even NASA has a role to fulfill in this venture.
Wernher von Braun himself founded NSI in the early 70's to further a rational
discussion about the future course of space exploration.  The work ahead of us
is not going to be easy, why make it harder on ourselves creating turf wars?
There is a galaxy waiting to be explored.  Let us get on with it.
    Now, the first practical question in light of the current concern over the
national budget.
       Given $100 how would you divide it among the following projects?
a) Space Commercialization; b) Automated Science Missions; c) Advanced Launch
System; d) Mission to Planet Earth; e) SETI research; f)National Aerospace
Plane; g) Moonbase; h) Space Station Freedom; i) Solar Power Satellites; j)
Mars Outpost

[for point of reference, my answers were: a) $3; b) $10; c) $10; d) $12; e) $7;
f) $12; g) $15; h) $12; i) $7; j) $12]

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

Date: 17 Apr 90 21:30:26 GMT
From: thorin!homer![e-mail]  (Jonathan Leech)
Subject: Re: Earthbound Asteroid.....trying again!

In article <[e-mail]> [e-mail] (Brian E. Alber) writes:
>I had heard that sometime last year or the year before that a large asteroid
>or some other LARGE (I mean really BIG) object nearly hit the Earth.  It
>supposedly came within 250,000 miles and scientists (astronomers?) here on
>Earth only knew of its existence after it had passed us.
>
>Questions:
>
>    1.) Is there any truth to this?

    Yes.  I vaguely recall (almost certainly wrong, but someone will
correct me, I'm sure) that the asteroid was designated 1989XA.

>    2.) When did this happen (where is it documented)?

    Check recent issues of _Astronomical Journal_.  There's probably
an article on it out by now.  Or look in Science Citation Index under
'Asteroids,' 'Earth-Crossing,' and 'Apollo Objects'.

>    3.) How large was it?

    Several km is typical for an earth-crosser, I don't know about
this one.

>    4.) What would have happened if it hit?

    Nuclear winter without the nuclear, but far worse than anything
the TTAPS crowd came up with.  If it was an ocean strike, vast
quantities of water would be vaporized, increasing the Earth's albedo
and perhaps setting off an ice age.  A land strike would be like a
multiteraton H-bomb.  There is a not-so-controversial anymore theory
suggesting that an event like this killed the dinosaurs and other
major historical extinction events were also due to cometary impacts.
There's a good deal of geophysical evidence to support this.

    If you can get to the NY museum of natural history, they have a
rather lurid artists conception of what would happen if the Barringer
meterorite (that made the km-diameter Meteor Crater in Arizona) would
do if it hit lower Manhattan.  Eliminate it, essentially.  That object
is tiny compared to an Earth-crosser which can actually be observed.

>    5.) Why didn't we see it coming?

    Because it's very hard to see tiny objects that are far away,
especially when they're approaching nearly head-on.  Also because it
takes time to analyze plates, detect potential asteroids, and compute
their orbits.

>    6.) How often do things this big come our way?

    Fairly often, even on a human time scale.  However, they don't hit
very often (thankfully).

>    7.) etc...

    Get Gehrels, _Asteroids_ (U.  of Az.  Press).  A good collection
of important papers in the area, though gradually becoming obsolete.
Read up on Apollo-type asteroids in general (refers to a class of
orbits that cross the Earth's orbit).

--
    Jon Leech ([e-mail])    __@/
    "Student Activism 1968-69 Oct 23: 15 students picket the Circus
     Room to protest the poor quality of UNC sandwiches."
    _The Daily Tar Heel_, 11/15/89

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

End of SPACE Digest V11 #279
*******************