Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Tue, 24 Apr 90 02:05:43 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 24 Apr 90 02:05:12 -0400 (EDT) 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!eugene@ames.arc.nasa.gov (Eugene N. Miya) Subject: Re: Titan (Questions about the Voyagers) In article <1990Apr18.205337.3482@ux1.cso.uiuc.edu> davies@uicsrd.csrd.uiuc.edu 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, eugene@orville.nas.nasa.gov {uunet,mailrus,other gateways}!ames!eugene ------------------------------ Date: 23 Apr 90 17:14:43 GMT From: deimos.cis.ksu.edu!uafhp!bmccormi@uunet.uu.net (Brian L. McCormick) Subject: Re: Dyson spheres? In article <24257@usc.edu>, robiner@oberon.usc.edu (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 bmccormi@uafhp.uark.edu University of Arkansas or st20314@uafsysb.uark.edu ---------------------------------------------------------- The opinions presented herein are subject to disclaimation ---------------------------------------------------------- ------------------------------ Date: 23 Apr 90 19:01:37 GMT From: hplabsb!dsmith@hplabs.hp.com (David Smith) Subject: Re: Our galaxy In article wmartin@STL-06SIMA.ARMY.MIL (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 dsmith@hplabs.hp.com (415) 857-7898 ------------------------------ Date: 24 Apr 90 00:09:01 GMT From: ogicse!blake!scameron@ucsd.edu (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 | _____(*)_____ scameron@toby.acs.washington.edu | My opinions, not theirs | WingNut ------------------------------ Date: 23 Apr 90 20:00:48 GMT From: convex!ewright@uunet.uu.net (Edward V. Wright) Subject: Re: Dyson spheres? robiner@oberon.usc.edu (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!henry@ucsd.edu (Henry Spencer) Subject: Re: Dyson spheres? In article <24257@usc.edu> robiner@oberon.usc.edu (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 henry@zoo.toronto.edu ------------------------------ Date: 23 Apr 90 16:35:55 GMT From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (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 | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | ------------------------------ Date: 23 Apr 90 12:09:43 GMT From: rochester!rit!cci632!lmm@rutgers.edu (Lance Michel) Subject: Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things) In article HIGGINS@FNAL.BITNET (Bill Higgins-- Beam Jockey) writes: >vsi1!hsv3!mvp@apple.com (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..." | lmm@cci632.UUCP | |___________________________________________C._Lauper____|__________________| (Song stuck in my head at the moment) ------------------------------ Date: 23 Apr 90 14:41:00 GMT From: sdd.hp.com!apollo!rehrauer@ucsd.edu (Steve Rehrauer) Subject: Re: Fermi paradox In article <101660@convex.convex.com> schumach@convex.com (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) rehrauer@apollo.hp.com "Spontaneous human combustion - what luck!"| Apollo Computer (Hewlett-Packard) ------------------------------ Date: Mon, 23 Apr 90 11:02:57 CDT From: steve@ncsc.navy.mil (Mahan) >Date: 20 Apr 90 17:45:14 GMT >From: nuchat!steve@uunet.uu.net (Steve Nuchia) >Subject: Re: Drake Equation (was Re: Interstellar travel) > >In article <3619@minyos.xx.rmit.oz> rxtajp@minyos.xx.rmit.oz (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 steve@ncsc.navy.mil ------------------------------ Date: 23 Apr 90 09:33:10 GMT From: bfmny0!tneff@uunet.uu.net (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 *******************