Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V16_0/V16NO056.ZIP/V16NO056

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

Date: Sun, 17 Jan 93 04:59:57
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #056
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 17 Jan 93       Volume 16 : Issue 056

Today's Topics:
                        ** BUSSARD RAMSCOOP **
                        averting doom (2 msgs)
            Broadcasting shuttle audio over the Internet?
                      Carbon-carbon heat shields
                      Cooling re-entry vehicles.
  Engineers, read this. Re: Galileo Stuck Ribs / Remote Manipulator?
                           Goldin's future
                     Handling Antimatter (2 msgs)
                    IP address for space shuttle?
                            Parting Words
                Solar sail (was: ** BUSSARD RAMJET **)
                    Soviet space disaster (2 msgs)
              Subjective Safety Measure(Re: man-rating)
         What's it like at the edge of the universe? (2 msgs)

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: Sat, 16 Jan 93 09:39:22 EST
From: John Roberts <[e-mail]>
Subject: ** BUSSARD RAMSCOOP **

-From: [e-mail] (Lynne K Wahl)
-Subject: Re: ** BUSSARD RAMSCOOP **
-Date: 15 Jan 93 05:13:39 GMT
-Organization: Kansas State University

[e-mail] (Jason Cooper) writes:

->Just been talking to Lynn Wahl over in my mailbox, and came up with an
->idea for using a light sail to bring the thing into orbit.  The plan is
->this:

->1. Laser-assist out of earth orbit
->2. Close approach to sun with sail edge-on to sun (for minimum drag)
->3. Sail up to orbit sequence out of the solar system

->It was broken into a lot more categories in my mail, but I _believe_ that
-[some stuff deleted] [CAUTION: Wild-Eyed Kansas Ranting Follows  PG-13] :)

-Actually, I proposed about an X step interplanetary probe.
- 1. Laser/maser boost out of Earth orbit (Come on, Solar Power Sats :)

That's definitely possible if you use the laser to heat propellant, as you
would for a laser launch.

-    Probe is now traveling *faster* than Earth orbit and is in a highly
-    eccentric elipse, with perihelion being just out/inside
-    Mercury orbit, and apogee being around Mars somewhere.  (had to look
-    them up)
- 2. Coast until perihelion, edge on to the sun.
- 3. Use solar sail for boost, and H collection out to apogee (around
-    planetoid belt ?)

If you're going to use any onboard propellant for your initial boost out of
the solar system, you'll get the greatest velocity change by expending it
close to the sun. To get close to the sun without too much fuel expenditure
before that point, you might want to do a gravitational slingshot around
Jupiter to kill most of your solar orbital velocity. If you're not in too
much of a hurry, you might use slingshots around Venus and Earth to build
up enough velocity to get out to Jupiter (like Galileo and Cassini). Perhaps
you could expend a batch of propellant just as you pass the sun, and deploy
your solar sail shortly thereafter. I don't know how much the sun could
contribute to useful interstellar velocity, since you'd better be leaving
the solar system pretty fast.

- 4. Possible use of Earth orbit Laser/Maser boost.

Using a laser from Earth to boost a solar sail is theoretically possible,
but the quantities of energy are staggering. For instance, to accelerate
a 1000000 kg interstellar spacecraft by 10^7 m/s (about 40% of the
velocity needed to get to Alpha Centauri in 50 years), and assuming 100%
efficiency, you need to expend about 1.5E21 Joules (~10-20 trillion dollars
at current electric rates). Antimatter is pretty expensive to produce in
terms of energy use too, so I don't know what the tradeoff would be likely
to be. Clearly, we need to come up with a really large, cheap power supply
before either of these options can be implemented. :-) Henry has mentioned
huge solar power collectors near Mercury as an example.

It's probably not practical to plan for a 1000-year mission to a nearby star -
the odds are that a more advanced spacecraft would be developed and get there
long before the slow probe arrived.

- 5. Use whatever fuel/power supply you want to get up to .? C.  We discussed
-    an antimatter triggered fusion ramscoop with the solar sail acting as
-    H collector. You may substitute your own here.  Please keep the light-
-    sail, it gets used later.
- 6. Use solar sail to brake into new solar system.  Possible use of ramscoop
-    as brake.  It seems to make a *much* better brake.
- 7. Put-put around the new solar system and explore.

-Needless to say, this is a LONG way in the future.  The closest
-interplanetary probe I see will probably be a bunch of super-light
-maser boosted one-shot probes talked about in the (L5 news?) called
-StarWisps or something like that.  If Henry Spencer, John Roberts or the
-equivalent would like to comment, please feel free.  I don't really have
-enough facts to do more than dream on phospor dots. :-)

---Lynn Wahl   [e-mail]           | The meek will inherit the
-Kansas State University Student                | earth, the rest of us are
-Soil Conservation Service Computer Specialist  | going to the stars. ----*

It sounds like you have some interesting ideas. One thing to think about -
the design requirements of an interplanetary probe and an interstellar
spacecraft are so different that you might consider separating out the
two functions - as your interstellar spacecraft approaches the stellar
system, deploy a planetary probe (which has to decelerate and stay in the
system), while the main spacecraft goes on to another star.

This is speculative - most likely, the first interstellar probes will
pass through star systems without slowing. You can get a lot of information
even with a flyby, and it saves the time and expense of slowing down enough
for stellar capture. An option if you find (uninhabited) planets or other
solid bodies is to deploy very small probes to impact those bodies. The
interstellar velocity of those probes would result in spectacular explosions,
and you could conduct a remote spectrographic analysis.

John Roberts
[e-mail]

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

Date: Sun, 17 Jan 93 05:34:57 GMT
From: Joshua Bell <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics,sci.environment

In article <[e-mail]> [e-mail] (Patricia C. Vener-Saavedra) writes:
>Hi there. As I recall, in about a billion years the sun will have
>about twice the luminosity it presently has. The average surface of
>Earth will be about 100 degrees C. Some lakes and rivers will have
>begun to boil. It will not be pleasant for homo sapiens.:-)

I would say that if Homo sapiens is still on Earth in a billion
years, it deserves it. :)

Joshua
|         A shimmering net undulating like an infinite borealis.             |
|                                                  - Chapterhouse: Dune      |
|                                                                            |
| [e-mail]  Academic Computing Services, University of Calgary |

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

Date: 17 Jan 1993 06:50:40 GMT
From: Nobody of Importance <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics,sci.environment

In article <[e-mail]> [e-mail] (Joshua Bell) writes:
]In article <[e-mail]> [e-mail] (Patricia C. Vener-Saavedra) writes:
]>Hi there. As I recall, in about a billion years the sun will have
]>about twice the luminosity it presently has. The average surface of
]>Earth will be about 100 degrees C. Some lakes and rivers will have
]>begun to boil. It will not be pleasant for homo sapiens.:-)
]
]I would say that if Homo sapiens is still on Earth in a billion
]years, it deserves it. :)

Finally! A kindred spirit. Besides, 1 billion years is a bit far down
the road anyway. I wouldn't worry about that quite yet anyway. I'd
worry more about getting large groups of humanity offplanet before
people like McGowen realize it is a "technocratic" solution. ;*)

]Joshua
]|         A shimmering net undulating like an infinite borealis.             |
]|                                                  - Chapterhouse: Dune      |
]|                                                                            |
]| [e-mail]  Academic Computing Services, University of Calgary |

Hit 'n' now to avoid an obnoxious sig thingie.

Subject: Patrick Chester            |Words to live by:
Age: NOYB                           |"Military action is important to the
Address: A place                    |nation--it is the ground of death and
Email:[e-mail]    |life, the path of survival and destruction
Political Views: Somewhere in orbit |so it is important to examine it."
Blackmarks: Politically Incorrect   |Famous Last Words:
(hobbies)   Anime Otaku/Trekker     |--If you cut me down, I will only become
            Technocentric           |more powerful...
            Netrekker (claypigeon)  |--Shhh!! There it is again....
            Whole bunch of -isms    |--Use the bazooka to open the door...
   (not worth shoot-on-sight orders)|--I cut the red wire...
--
<***** INSERT LAWSUIT DEFLECTION TEXT*****>

I speak (type actually) for myself only. Even if I did decide to
speak for UT, no one would listen.

Flame away, I don't bleedin' care...

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

Date: 16 Jan 93 15:52:07 GMT
From: Marshal Airborne Perlman <[e-mail]>
Subject: Broadcasting shuttle audio over the Internet?
Newsgroups: sci.space.shuttle,sci.space,comp.protocols.misc,comp.protocols.tcp-ip

messages always help to have text attached to them..
--
|o| Marshal Perlman                             Internet: [e-mail] |o|
|o| Florida Institute of Technology                              IRC: Squawk |o|
|o| Melbourne, Florida                                   Private Pilot, ASEL |o|
|o| 407/768-8000 x8435                            Goodyear Blimp Club Member |o|

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

Date: Sat, 16 Jan 93 20:47:15 EST
From: John Roberts <[e-mail]>
Subject: Carbon-carbon heat shields

-From: [e-mail] (Gary Coffman)
-Subject: Re: Let's be more specific (was: Stupid Shut Cost arguements)
-Date: 14 Jan 93 08:25:35 GMT
-Organization: Destructive Testing Systems

-NASP reportedly
-uses carbon-carbon composite honeycombs for strength and heat resistance.
-Apparently they've found some way to passivate them against oxidation at
-high temperatures.

The Shuttle uses carbon-carbon for the leading edges of the wings, with the
outer layers chemically converted to silicon carbide.

John Roberts
[e-mail]

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

Date: Sat, 16 Jan 1993 17:47:26 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Cooling re-entry vehicles.
Newsgroups: sci.space

In article <2402@snap> [e-mail]-mrc (Paul Johnson) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>Even the SR71 uses fuel to help cool it's titanium skin, and it travels
>>more than four times slower than a re-entry vehicle.
>
>Why not use a total-loss cooling system in a re-entry vehicle?  I
>gather that ablative cooling works on this principle: as the shield
>reaches its maximum temperature it ablates, leaving fresh, cooler
>shield underneath.  So would a titanium skin with cooling pipes
>underneath it work?  The coolant would be used once and then dumped
>behind the vehicle.

The problem with this approach is the mass of cooling liquid you'd
need to carry to orbit in order to dump it cooling the vehicle on
re-entry would significantly impact payload you could carry to orbit.
If you could fill the cooling tanks from sources in orbit, it might
work out.

>Alternatively I gather that JPL has looked into aerobraking manouvers
>that involve flying engine-first into the atmosphere and running the
>motors at "idle".  Because the engine exhaust is already moving with
>the vehicle, it streams back around the vehicle and keeps the
>atmosphere at a safe distance.  So you could use an SR71-style fuel
>cooling system, dump the hot fuel into an engine in the nose and then
>use the resulting exhaust to protect the vehicle still more.  Am I
>making sense.

Yes, this *sounds* plausible. There are probably practical difficulties.
One I see right away would be in trying to keep the engines "idling"
smoothly against a hypersonic flow of air trying to enter the bells.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     | emory!ke4zv![e-mail]

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

Date: Sat, 16 Jan 1993 09:59:46 GMT
From: David Knapp <[e-mail]>
Subject: Engineers, read this. Re: Galileo Stuck Ribs / Remote Manipulator?
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (SCOTT I CHASE) writes:
>In article <[e-mail]>, [e-mail] (justin sullivan) writes...
>>In <[e-mail]> [e-mail] (Henry Spencer) writes:
>>
>>>Bear in mind that the Galileo malfunction is of a fairly unusual type.
>>>Most failures are subtle things ailing in the innards of the boxes.
>>
>>One could always argue that it wasn't an unusual problem that caused
>>Galileo to have a crippled antenna, but an oversight of hoardes of fine
>>engineers. Nobody's perfect, but when you get so many superbrains together
>>and give them piles of money, they're expected to deliver a perfectly
>>functioning piece of hardware. If they're so damn smart (I believe they are..)
>>things like this shouldn't happen. Either way, 40bps means that my great
>>grandchildren will have to analyze the data.
>
>That's at least a little unfair.  The way I understand it, Galileo
>only lost it's lubricant because it had to make an extra cross-country
>round trip to and from the launch site due to a launch delay and the
>need to store it during the interrum.  This caused vibration that the
>engineers did not design for.  I don't think you can hold the designers
>particularly responsible that the device failed when used in a way
>that did not comply with the original design specifications.
>
>-Scott

Scott.

IMHO, you are both right and wrong.  The engineers, heck, *all* the
people that worked on that s/c were challenged to build a craft to go
to Jupiter and collect data. Yes, it as put through rigors not planned
for but those engineers had the luxury of inspecting that craft
before launch to ensure it was flight worthy. It was not and they
didn't fix it before the launch.

I know that this is a rather bizarre situation since that same antenna has
worked quite well on other satellite missions, but really, it is
important that responsibility be taken for not fully understanding and/or
not taking action on something that has seriously jeopardized the mission.


NASA engineers are some of the brightest, most inginuitive folks I've ever met
and read about.  These guys fixed a s/c that was 20 au out on a mission!
(voyager and it's sticky camera and post launch decisions on low light
level objects)  They do rather incredible things there.  Having
foresight to make sure the lubricant was there is not so incredible.

We should give credit when it is due (and it is due there *often*)
but also not be afraid to admit failure when it happens.

(all IMHO)


Personally, I think NASA engineers and scientists have a very good chance
of fixing this problem en route, if they keep in mind:

illegitimus non carborundum est.





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

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

Date: Sat, 16 Jan 1993 18:45:04 GMT
From: Dave Michelson <[e-mail]>
Subject: Goldin's future
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Jeffrey David Hagen) writes:
>Besides, catch a clue about JPL. It is widely considered to be the single most
>bloated, pig-headed, and inefficient part of NASA among industry folks I have
>dealt with. Having spent some time as a student at Caltech myself, I can
>certainly see were they get that impression.
>Jeff Hagen
>Rice University

Sad but true, that impression certainly exists.  I toured a well-known radio
observatory several years ago.  The assistant director made a comment about
a project.  A colleague on the tour offered that at JPL, they're doing such and
such in connection with a similar project.  The assistant director replies
(somewhat annoyed), "JPL spends most of their time doing PR.  Here, we do
science."

I'm not in much of a position to judge whether that impression is correct,
however.

---
Dave Michelson                             University of British Columbia
[e-mail]                                  Antenna Laboratory

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

Date: Sat, 16 Jan 93 21:00:23 EST
From: John Roberts <[e-mail]>
Subject: Handling Antimatter

-From: [e-mail] (Kevin W. Plaxco)
-Subject: Re: Handling Antimatter
-Date: 15 Jan 93 21:23:09 GMT
-Organization: California Institute of Technology, Pasadena, CA

-In article <[e-mail]> [e-mail] (Thomas Clarke) writes:

->up my pet scheme for handling the stuff.
->Imagine a molecular cage, say a buckminsterfullerene.  The cage has a
-...
->could then be trapped in the center of the cage where it would
->only "contact" and be repelled by the orbital electrons.  Since
->electrons and antiprotons don't annihilate, this arrangement should
->be stable as long as the cage is intact.

-The molecular weight of C60 plus antiproton is >721 daltons.
-Proton-antiproton annihilation would convert 2/721 or 0.28%
-of this into energy.  The energy/mass ratio of this rocket
-fuel would, unfortunately, be no better than that of U-235.

For launches and for interplanetary travel, such an energy density would
be spectacularly good - in fact, you'd use many parts of normal reaction
mass to each part of antimatter-containing material. Proposed antimatter
rockets use a matter-antimatter ratio of millions to one.

John Roberts
[e-mail]

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

Date: Sun, 17 Jan 1993 03:30:31 GMT
From: Thomas Clarke <[e-mail]>
Subject: Handling Antimatter
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Kevin W. Plaxco) writes:
>In article <[e-mail]> [e-mail] (Thomas Clarke) writes:
>
>>up my pet scheme for handling the stuff.
>>Imagine a molecular cage, say a buckminsterfullerene.  The cage has a
>
>"Pet", "cage"... very funny.
>
>>could then be trapped in the center of the cage where it would
>>only "contact" and be repelled by the orbital electrons.  Since
>>electrons and antiprotons don't annihilate, this arrangement should
>>be stable as long as the cage is intact.
>
>The molecular weight of C60 plus antiproton is >721 daltons.
>Proton-antiproton annihilation would convert 2/721 or 0.28%
>of this into energy.  The energy/mass ratio of this rocket
>fuel would, unfortunately, be no better than that of U-235.
>
No better than U235?!  We should be able to do so well. :-)
 if something like this would work it would be the equivalent
of being able to dissolve U235 salts in water and then running
 a rocket engine by simply spraying the solution into the
engine.


Your calculation may  scotch my tank destroying rifle bullet
scenario, however.  A good thing too!-)







--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
[phone], FAX: [phone], [e-mail]

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

Date: Sat, 16 Jan 93 10:11:19 EST
From: John Roberts <[e-mail]>
Subject: IP address for space shuttle?

-From: [e-mail] (Gene Kochanowsky)
-Subject: IP address for space shuttle?
-Date: 15 Jan 93 22:33:21 GMT
-Organization: Associated Electronic Engineers

-    I had heard that when the Shuttle is in orbit it is on the internet. Is
-this true and if so, does anyone know what it's IP address is?

The Shuttle was linked to another network on an experimental basis, but the
address became widely known, and the astronauts were flooded with hundreds
of trivial messages, which they couldn't spare time to read anyway. After
that, it's highly unlikely that there's a public network connection.

If you want to contact the Shuttle, your best bet is to get involved with
amateur radio - there's an ongoing series of amateur radio experiments,
with an automatic responder device, and sometimes (I think) brief voice
communications.

Mir is also involved in amateur radio, when the cosmonauts can spare time
for it.

John Roberts
[e-mail]

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

Date: Sat, 16 Jan 93 18:42:30 EET
From: [e-mail] (F.Baube x554)
Subject: Parting Words

> "God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
>        -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

Are these perhaps the *last* words spoken on the moon ?
If not, what *were* the last ?

--
* Fred Baube         ..when you think your Toys  you hear Laughter
* Optiplan O.Y.           * have gone Berserk    cracking through the Walls
* [e-mail]       * it's an illUsion     you're sent Spinning
* GU/MSFS                 * you Cannot Shirk     you Have No Choice
* #include <disclaimer.h> *                 -- Sioux proverb

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

Date: 15 Jan 93 14:23:22 GMT
From: Jason Cooper <[e-mail]>
Subject: Solar sail (was: ** BUSSARD RAMJET **)
Newsgroups: sci.space

Just curious...  Does anybody out there know how much acceleration a
solar sail could offer, and how big it would have to be in area?  With
the solar sail stage figured in, the following stages are now what we
seem to want to use:

-Solar Sail
-Antimatter-heated, Carbon-Catalyzed Fusion
-Carbon-Catalyzed Fusion
-Antimatter-heated p-p fusion
-p-p Fusion

The solar sail being the long string of events leading to a deployed
solar sail pushing the craft away from the sun at an angle from the
ecliptic, and the antimatter heating being the previously discussed
antimatter creation and injection into the system.  Can anybody correct
me as to a better way to get the effect of the solar sail, or a better
order or something?

                                                Jason Cooper

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

Date: 15 Jan 93 22:12:00 GMT
From: Bill Edwards <[e-mail]>
Subject: Soviet space disaster
Newsgroups: sci.space

[e-mail] (Tom A Baker) wrote:

TA>Ahhhhh.  During the Sixties there were indeed many persistant rumours
TA>about heartless Communist space scientists launching cosmonauts in
TA>unsafe capsules, and dead Soviets orbiting forever.  These rumours
TA>never could be verified for my taste.

I take your view; it seems very unlikely.

But - and correct me if I'm wrong - the Soviets said that they never
intended going to the moon.  And now we have seen film of the booster
that would have taken them there and and pictures of the spacecraft
they would have travelled in.

Just playing devil's advocate.

Bill / Usenet: [e-mail]
---
 . DeLuxe./386 1.25 #9224 .


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

Date: 17 Jan 93 04:11:37 GMT
From: Tom A Baker <[e-mail]>
Subject: Soviet space disaster
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Bill Edwards) writes:
B.E|[e-mail] (Tom A Baker) wrote:
B.E|TA>Ahhhhh.  During the Sixties there were indeed many persistant rumours
B.E|TA>about heartless Communist space scientists launching cosmonauts in
B.E|TA>unsafe capsules, and dead Soviets orbiting forever.  These rumours
B.E|TA>never could be verified for my taste.
B.E|But - and correct me if I'm wrong - the Soviets said that they never
B.E|intended going to the moon.  And now we have seen film of the booster
B.E|...
B.E|Just playing devil's advocate.

Understood, and certainly I agree with you.  Notice I never said the
rumors were NOT true.
                       *8)
As has been true with many things about the former Soviets, I have accepted
the fact of "not knowing", and will just have to be patient until any
definate answer comes, if it ever does.  I know that's not as popular a
position, on the Net, as claiming certainty one way or the other, but
I'm not letting that bother me.  (I enjoy Devil's Advocates.)

tom

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

Date: 16 Jan 93 22:40:48 GMT
From: Pat <[e-mail]>
Subject: Subjective Safety Measure(Re: man-rating)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Bruce Watson) writes:
>In article <[e-mail]| [e-mail] (Pat) writes:
>|In article <[e-mail]| [e-mail] (Robert Turner) writes:
>||
>||Isn't the elevator considered the safest mode of transportation meeting both the
>||"if I get in, I get out" and "deaths per passenger mile".
>||
>|
>|a
>|Ah, this guy has never heard of elevator accidents?
>|While kinda uncommon they do occur.  mostly due to improper door opening.
>
>Contrary to all the movies we've seen, there has never been an elevator
>fatality since Otis designed the safety features of the modern elevator
>in the late 19th century.
>

Semantic argument, chief.

While, In the last 100 years, the number of fatalities due to failure of the
prime mover  Motors, cables and lift ram has been negligible,  there
have still been numerous elevator fatalities.  Mostly due to improper
door opening.  Most public housing authorities have been sued for this.
the door opens, and there is no car.  while certainly there is a
great deal of passenger negligence,  that still counts.  WE also
just had a case here in DC.  the elevator jammed, the passengers
went out the roof hatch, and forced a floor door.  while debarking
the car moved and one woman fell fatally.   once again a door related
accident.

Elijah otis certainly did a lot ofr elevator safety, but as mary shafer
says, life aint perfect.

pat

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

Date: 17 Jan 93 01:24:31 GMT
From: Keith Allan Schneider <[e-mail]>
Subject: What's it like at the edge of the universe?
Newsgroups: sci.space

[e-mail] (Tom A Baker) writes:

>In article <[e-mail]> [e-mail] (robert.f.casey) writes:
>>I remember reading in (I think) Sky & Telescope some years ago an
>>article about the universe, and some theories on it's origin (big
>>bang, and such).  One theory said something to the effect that our
>>universe was expanding, and was surrounded by a larger area of some
>>sort of superdense material.  As if the universe was a bubble of
>>mostly empty space expanding inside this superdense material.
>>Which leads to the question: Is there a boundry, where you can
>>stand right next to the "surface" of the universe bubble, and
>>touch with your spacesuited hand the wall of superdense material?
>.....
>>I suspect that I'm only half remembering an analogy in a discription
>>of some theory of multiple universes.
>...
>>But is there even any connection with reality to this?

>One (predicted) corrolary (sp?) of the expanding universe paints a picture
>that is not too different from this.  Remember "space dilation", from
>special relativity?  Things change shape when they move fast (relative
>to you) ... they get "squashed".

>So, (almost) all the galaxies are flying away from us.  Therefore,
>they get squashed too.  The farther away the galaxy is, the more
>squashed it seems (to us).  You can think of some very, very far away
>galaxies that might be flat as a pancake, 60,000 light years across,
>but unbelievablyt thin.

>Think of the matter that flew out of the Big Bang the fastest.  Still
>zipping away at about the speed of light, it forms a thin, thin,
>tenous shell, maybe of very thin galaxies, all around us -- the "edge
>of the universe".

Okay, this is all wrong and points to a conceptual error about the nature
of the universe and the big bang itself.  The big bang was not some giant
firecracker that sent shells of matters off with various speeds (the
earlier the faster, as you seem to be saying).  Instead, the big bang
was actually the origin of space-time.  That is, it could be thought of
as a simultaneous explosion of all points of space -- it is the fabric of
space time that is expanding, not just shells of matter expanding from some
common center.  There is NO center, or, more accurately, every point of the
universe is the center.

The reason that galaxies are moving away from us (and the further ones are
faster) is because space-time, the metric for measurement, is expanding.
That is, the coordinate system is expanding.  Think of the universe as
a two dimensional cartesian coordinate system, with the Milky Way at the
origin and various galaxies at each integer coordinate.  Then, expand
the coordinate system uniformly (multiply the coordinates by some
number, say 2).  That is, (1,1)-->(2,2) and (2,2)-->(4,4).  Now, you
see that the galaxy located at (2,2), twice the distance from us as the one
located at (1,1) has moved twice as far in the same amount of time?
Yes, the velocity is proportional to the distance.  This is Hubble's Law,
and it shows that space-time is expanding uniformly.

And, there is no "edge" of the universe.  Sure, the universe on the whole
is expanding, but it isn't expanding into some medium...  it is expanding
into another dimension.  Again, there is no edge.  The universe is certainly
finite in size, but it has no edges or boundries.  Depending on its mass,
it may fold back on itself.  Then, it would be like the surface of the
Earth.  It is certainly a finite area, but you can't "fall off" the Earth,
as some early seamen had feared.  The universe is like this.  Finite, but
no edge.

Hope this helps.

>Now, your question ... to someone *in* that region of space,
>everything looks normal, because it is at rest w.r.t. them.  To them,
>we in the Milky Way are at the edge of the Universe and are
>unbelievably thin.

>So goes the theory.

Ooops.  Maybe you did know what you were talking about.  It just sounded
funny.  I suppose you could think of the edge of the universe as sort of
a sphere with radius 15 billion (or whatever) light years.  Was this
what you were saying?  I couldn't tell...

keith

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

Date: 17 Jan 93 00:18:46 -0600
From: [e-mail]
Subject: What's it like at the edge of the universe?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (robert.f.casey) writes:
> I remember reading in (I think) Sky & Telescope some years ago an
> article about the universe, and some theories on it's origin (big
> bang, and such).  One theory said something to the effect that our
> universe was expanding, and was surrounded by a larger area of some
> sort of superdense material.  As if the universe was a bubble of
> mostly empty space expanding inside this superdense material.
> Which leads to the question: Is there a boundry, where you can
> stand right next to the "surface" of the universe bubble, and
> touch with your spacesuited hand the wall of superdense material?

In a way, every point in our Universe is at the edge.  This is difficult
to imagine due to our 3-dimensional perceptions.  I would recommed two
books that really help to illustrate the concepts of more than three
physical dimensions and the expanding Universe.  The books are:

"Flatland; a romance of many dimensions" by Edwin Abbott and
"Sphereland; a fantasy about curved spaces and an expanding Universe" by
Dionys Burger.

--
Dale Karsten
Internet: [e-mail]

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End of Space Digest Volume 16 : Issue 056
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