Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from holmes.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests) ID ; Mon, 29 May 89 05:17:20 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 29 May 89 05:17:12 -0400 (EDT) Subject: SPACE Digest V9 #465 SPACE Digest Volume 9 : Issue 465 Today's Topics: Re: Magellan update "it's been light years . . ." Re: SPACE Digest V9 #453 - Asteroids and Dinosaurs Re: Space telescope delays Re: Private Space Companies Magellan Status of 05/26/89 (Forwarded) Re: Private Space Companies Oort cloud (was: Re: The late NEMESIS Theory) Re: asteroid almost hits earth Neptune pix Re: Meteorite impact in Soviet Union in 1947. ---------------------------------------------------------------------- Date: 26 May 89 02:29:13 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Magellan update In article <890525120657.00001E562B1@grouch.JPL.NASA.GOV> PJS@GROUCH.JPL.NASA.GOV (Peter Scott) writes: [several K of mindless drivel via DASnet ] I dunno about other folks but I am *SO GLAD* we are bridging to other nets!!! :-) -- Tom Neff UUCP: ...!uunet!bfmny0!tneff "Truisms aren't everything." Internet: tneff@bfmny0.UU.NET ------------------------------ Date: 25 May 89 18:40:03 GMT From: thorin!lhotse!symon@mcnc.org (James Symon) Subject: "it's been light years . . ." In article <5657@lynx.UUCP>, neal@lynx.uucp (Neal Woodall) writes: > In article <14345@bfmny0.UUCP> tneff@bfmny0.UUCP (Tom Neff) writes: > > >>I am never so frustrated and morose about our prospects for the future as > >>when I find someone misunderstanding science. Phrases like "it's been > >>light-years since I saw home" (_Hard Time on Planet Earth_) ... > . . . > It seems to me that the original poster made a misinterpretation of the > phrase he posted....I don't really see what is "wrong" about describing > a journey in terms of distance rather than time, or vice-versa. > I see. They meant it the way some story's trucker-hero would say, "It's been five hundred miles since I saw home." Come on. You're being overly generous, especially since this is a common mistake, and we're talking about a throw away line in a typically dimwitted TV show designed for the masses! Besides, even if the writers WERE waxing poetic, my cynicism convinces me the usage was lost on 97% of the audience and it just reinforced their misconception. Reminds me of A&W Root Beer's ad campaign that said, "Wet your appetite!" Aargh! Even if I could believe the writer intended the mistake as cute irony, it was still a disservice. jim symon@cs.unc.edu {decvax uunet}!mcnc!unc!symon ------------------------------ Sender: "John_A_Kostecki.WBST207V"@Xerox.COM Date: 25 May 89 05:31:43 PDT (Thursday) Subject: Re: SPACE Digest V9 #453 - Asteroids and Dinosaurs From: "John_A_Kostecki.WBST207V"@Xerox.COM Cc: "John_A_Kostecki.WBST207V"@Xerox.COM Reply-To: "John_A_Kostecki.WBST207V"@Xerox.COM In article The extinctions of the dinosaurs was one and about 300 million years later, >the extinction of pre-historic mammals another. Before then, the >geological record shows extinction after extinction at roughly 300 million >year intervals. It's been a while since I've been actively involved in the geology "game" so I'm not 100% familiar with all the literature. There are some problems with the numbers you mentioned. I accept that you were doing it from memory, so I don't want to act picky. Anyway, about those extinctions: 1) the final dinosaur extinctions occured about 110 - 90 million years ago. This is coincidental with what we call the Cretaceous/Tertiary Event. The event was marked not only by the passing of the last "dinosaurs", but also marked the demise of several hundred marine plankton species. Since the study of marine phytoplankton (one-celled plants) was one of my areas of concentration, I had to do some work on this stuff once. The main points are that dinosaurs weren't the only organisms effected by the environment at the end of the Cretaceous, but also that this last major extiction occured at about 90 mypb (mil yrs before present). 2) the last major extinction prior to to Cretaceous/Tertiary was the Permo/Triassic Event, which I think was about 450 mybp. Prior to that, there were other minor extinctions which might have wiped out classes of species or entire phyla, but in most cases there are still living decendents of these species. One theory of the mass extinctions is that there was some other factor in the environment which caused these mass deaths. Something which we also need to understand is that we, ie, mankind, has been around for only a few tens of millions of years. When you consider that our accurate records have only been kept back to biblical times (a span of 5000 years at best), and the major portion of the fossil record goes back only to the Pre-Cambrian (Archeozoic), which is 600+ mybp, our own records and recollections and comparisons of time are somewhat warped. What I mean is that a "mass extinction" in the fossil record may represent 10s of millions of years in the older strata, and maybe several hundred thousand years in the most recent events. How do we compare the extinctions of present day animal species with those which occured at the Permo/Triassic Event? Anyway, there were some other theories posed based on less spectacular causes. One is that the sea-floor spreading and continental drift which are a major part of modern theories of plate tectonics and mountain building, may also be the cause of major climatic or at least environmental changes. Lets look at the events occuring in the Mesozoic (450 - 90 mybp). During the begining of this era, the Triassic strata in the US shows evidence on the east coast of the initial stages of the breakup of a major continent. As we go into the Jurassic, there is evidence of large shallow seas in the US midcontinent. These shallow seas would have opened millions of square miles of continental shelf to the species living at that time and caused the vast "flowering" of species we see in the record. The reason for the shallow seas is interesting. When I participated in a cruise sponsored by the Deep Sea Drilling Project in 1980, one of the chief scientists had proposed that this might have been caused by the increase in sea-floor spreading rates seen at this time, ie, with all the lava pushing up at the mid-ocean ridges, there was an increase in ocean floor volume and thus the oceans were "pushed" upon the plains areas of all the continents. These shallow seas did one other thing in that they caused a more temperate climate and added more warm waters to the seas. As the end of the Mesozoic (Cretaceous) started to arrive, the spreading decreased, thus the volume of the sea-floor decreased, therefore, the shallow seas were no longer there - now only the thin continental shelves we see today. This caused a major ecological disaster because of the loss of this environment, greater competition in the food chain, and only the strong or more biologically successful survived. The evidence of the asteroid/meteorite might be convincing as a means of explaining the "last gasp" of the dinosaurs, but I'm not particularly convinced that it was the ultimate cause. Most of the similar types of events in the past century, such as the explosion of the island of Krakatoa, did lead to localized killings, but did not have much of a world-wide impact, except for lowering average temperature a little and prolonging the twilight times of the day for several years. If we look at Mt. St. Helens, the forrests denuded by the explosion are now growing back. The question which this raises is what would the size of the asteroid have to be to cause a mass extinction, but only be selective? Remember, mammals survived the Event, but most of them were small, just as some dinosaurs species, so what was it that could have caused the problem? Well, enough for now. John A. Kostecki Xerox Corp. Webster, NY ------------------------------ Sender: "Dennis_C._Brantly.WBST129"@Xerox.COM Date: 25 May 89 04:46:56 PDT (Thursday) Subject: Re: Space telescope delays From: Brantly.WBST129@Xerox.COM Cc: Brantly.WBST129@Xerox.COM For those interested in the process by which time is to be allocated for observational use of the Space Telescope, and/or how the Space Telescope is to operate (blockage of large areas of viewing by the earth/sun, warm-up of selected instruments, locking on a designated viewing area, etc.), I would recommend an article in the June 89 issue of Astronomy magazine: "From Idea to Observation: The Space Telescope at Work"; an astronomer's request for observing time on the Hubble Space Telescope sets off a complex sequence of scheduling, observing, and data analysis, by Ray Villard. Dennis... Brantly:WBST129:Xerox Webster, NY ------------------------------ Date: 26 May 89 12:52:29 GMT From: prism!ccoprmd@gatech.edu (Matthew DeLuca) Subject: Re: Private Space Companies In article reddy@uts.amdahl.com (T.S. Reddy) writes: >> > I doubt that Boeing can develop a new space vehicle given that it >cannot even build a new airliner from scratch without collaborating with >another company or without government aid. Er, what planes, what company, and what government? I don't know about all of their planes, but I don't recall the government subsidizing the development of the 757 and 767, and I don't know what you mean by collaboration; Boeing is 'borrowing' workers from Lockheed, here in Atlanta, and they do contract some of their work out ,butI don't think that qualifies as collaboration. I have to agree with Henry (I think it was Henry...); Boeing is probably the only company that can develop it's own launch system. -- --------------------------------------------------------------------------------Matthew DeLuca : Georgia Institute of Technology : [This space for rent] ARPA: ccoprmd@hydra.gatech.edu : -------------------------------------------------------------------------------- ------------------------------ Date: 26 May 89 22:27:03 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: Magellan Status of 05/26/89 (Forwarded) MAGELLAN STATUS May 26, 1989 After today, the Magellan status reports will be available only once a week, unless warranted by spacecraft activity. The twice daily momentum wheel desaturations and the daily star calibration were performed routinely Thursday. Analysis of last Sunday's trajectory correction maneuver indicates an achieved velocity of 2.967 meters per second, versus a desired 2.935 meters per second. The execution error was less than 1.1 percent. The final spacecraft parameters for Cruise-3, the next spacecraft computer command sequence, have been given to the spacecraft team's Upload Preparation Group. Cruise-3 will be uploaded next Tuesday afternoon, May 30. SPACECRAFT Distance From Earth (mi) 3,192,936 Velocity Geocentric 5,674 mph Heliocentric 60,213 mph One Way Light Time 17.5 sec ------------------------------ Date: 26 May 89 15:51:41 GMT From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!henry@handies.ucar.edu (Henry Spencer) Subject: Re: Private Space Companies In article reddy@uts.amdahl.com (T.S. Reddy) writes: > I doubt that Boeing can develop a new space vehicle given that it >cannot even build a new airliner from scratch without collaborating with >another company or without government aid. I'm not aware that it's ever had government aid for airliner development. (Once or twice it has developed airliners that were related to, or descended from, government projects. Contrary to popular misconception, the KC-135 and the 707 are **not** the same aircraft -- they don't even have the same fuselage cross-section -- although they share a common [privately funded] ancestor.) As for collaboration with other companies, certainly Boeing prefers to spread the investment and risk around as much as it can -- who wouldn't? -- but there is no question that Boeing has the resources to go it alone if necessary. Boeing's current commercial order backlog is over 1500 airliners. That's over 75 BILLION dollars. And you can bet they're making a profit on it. -- Van Allen, adj: pertaining to | Henry Spencer at U of Toronto Zoology deadly hazards to spaceflight. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 26 May 89 23:40:48 GMT From: usc!csun!solaria!ecphssrw%afws.csun.edu@bloom-beacon.mit.edu (Stephen Walton) Subject: Oort cloud (was: Re: The late NEMESIS Theory) In article <13217@ut-emx.UUCP>, nather@ut-emx (Ed Nather) writes, in response to Bill Wyatt (wyatt@cfatst.harvard.edu): >Apparently you know of observational evidence that I don't -- would you >please cite it, bearing in mind that the theory was devised to explain the >origin of comets, so their presence is not evidence the theory is correct? I was going to summarize a bunch of arguments here, but just re-read the section of the text I used this year for intro astro (Abell, Morrison, and Wolff, _Realm of the Universe_, 4th edition). An excerpt: "Observationally, the aphelia of new comets typically have values near 50,000 AU. This clustering of aphelion distances was first noted by Dutch astronomer Jan Oort, who proposed in 1950 a scheme for the origin of the comets that is still accepted today." This passage was written by the second author, David Morrison, a very well informed planetary astronomer of my acquaintance (I'm a solar physicist, and thus not really qualified to pass judgement). However, Morrison goes on to write: "Just because most new comets have _aphelia_ near 50,000 AU, we should be careful not to conclude that the Oort cloud consists of billions of comets in roughly circular orbits at this distance, like a shell around the Sun. There may be some comets in nearly circular orbits, but if so, we have no evidence of them." He then notes that a passing star can cause only small perturbations in an orbit, so that a new comet with perihelion 1 AU cannot have had a perhelion of more than a few AU on its previous orbit. On the other hand, this means that there must be many, many comets in the outer solar system for every one which we observe; Object Chiron is a possible example, though a large one: occultation measures give its diameter as at least 100 km. So, both Bill and Ed are partly right, I guess. There is no evidence for the spherical shell which is the picture most of us have of the Oort cloud, but there are still many more comets in the outer solar system. -- Stephen Walton, Dept. of Physics & Astronomy, Cal State Univ. Northridge RCKG01M@CALSTATE.BITNET ecphssrw@afws.csun.edu swalton@solar.stanford.edu ...!csun!afws.csun.edu!ecphssrw ------------------------------ Date: Fri, 26 May 89 10:41:49 PDT From: Peter Scott Subject: Re: asteroid almost hits earth agate!shelby!Portia!hanauma!joe@ucbvax.Berkeley.EDU (Joe Dellinger) writes: > Incidentally, some geophysicists are waiting quite impatiently >for another mag 9 mega-quake. This is a great source of comfort to all of us in Southern California... Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: Fri, 26 May 89 12:07:31 PST From: Peter Scott Subject: Neptune pix X-Vms-Mail-To: EXOS%"space@andrew.cmu.edu" The latest issue of the JPL _Universe_ (in-house newspaper) has a couple of pictures of Neptune, showing about the detail you get of Mars from a small amateur scope (say, 6"). Unfortunately I can't reproduce them here, but the caption is interesting nevertheless: NEARING NEPTUNE -- These Neptune images by Voyager 2 on April 26 were from 176 million kilometers (109 million miles). The picture at right was taken five hours after the left, during which time the planet rotated 100 degrees. The dark spot visible in the left photo was in images obtained three months earlier [said dark spot is about the size and latitude of North Africa if the disk were Earth's]. A brighter white spot, prominent earlier, has apparently faded. The white spot near the south pole in the right picture is new [looks slightly smaller than Greenland, by the same analogy, tho' at the other end of the planet]. It was visible faintly in a picture 18 hours earlier at the same longitude. Can't wait for us to get close enough to resolve the 90-mile high statue of Elvis which we *know* must be there :-) Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 26 May 89 20:34:48 GMT From: megatest!ivan@decwrl.dec.com (Ivan Batinic) Subject: Re: Meteorite impact in Soviet Union in 1947. If memory serves me, this was known as the "Tingustu Event" (or something close to that). Witnessed by many from afar, there were reports of extremely high-intensity light from the horizon. An enormous circular section of forest was flattened and flash- burned. However, NO CRATER nor evidence of any crater exsists. Dr. C. Sagan speculated that this could be explained by the advent of a "piece" of comet material (methane ice) impacting the earth, causing a huge gas-explosion. I believe there are actual documents reporting the incident, however I have no idea how to locate them. I hope I have not confused two separate events here. It would be amusing if "lightning" (as it were) did strike twice in one place! Ivan ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DISCLAIMER: Blah-blah, Woof! Woof! ------------------------------ End of SPACE Digest V9 #465 *******************