Date: Mon, 27 Jul 92 05:01:19 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #041 To: Space Digest Readers Precedence: bulk Space Digest Mon, 27 Jul 92 Volume 15 : Issue 041 Today's Topics: Antimatter (was propulsion questions) Methods for meteor avoidance Whales (SETI) (2 msgs) Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: Sun, 26 Jul 1992 23:26:23 GMT From: James Davis Nicoll Subject: Antimatter (was propulsion questions) Newsgroups: sci.space In article mikew@kpc.com writes: >jdnicoll@watyew.uwaterloo.ca (James Davis Nicoll) writes: >> Given that one can mix the antimatter-reaction mass ratio to get >>the Vexhaust one wants, the dangers of standing in the vicinity of the >>exhaust of an antimatter powered ship could be *identical* to that of >>standing inthe vicinity of a conventional ship. >Actually there is one piece of information missing here. In a conventional >rocket most of the exhaust is being used to push more fuel closer to orbit. >In an antimatter rocket, you have a much higher payload/fuel ratio, so for >the same payload, there will be much less exhaust. Odds are the antimatter will be the expensive component of the reaction-mass/'fuel' mix, and so the am-reaction-mass ratio will be such that the am is used as efficiently as possible. The mass ratio is smallest if there is a 50% am, 50% matter mix, but that uses much more am then a mixture of am/m which is mostly matter. I would bet the population of Gary, Indiana that if antimatter energised propulsion systems are used from Earth's surface to reach orbit, the exhaust velocity will be in the 10 km/s range, rather than close to C. Also, 'pure' photon drives tend to produce oodles of nasty hard radiation which could very well fall outside the allowable ranges of todday's litigation prone society, plus they suck up power like a mad fiend. James Nicoll ------------------------------ Date: Mon, 27 Jul 1992 00:37:24 +0000 From: Andrew Haveland-Robinson Subject: Methods for meteor avoidance Newsgroups: sci.space In article brendan.woithe@f820.n680.z3.fido.zeta.org.au writes: >After the meteor from last year passed withinn 4 minutes of the earth (the >large one), I was wondering if we have any system of avoiding these >large beasts??!! I read that if it hit the earth, millions could have died. > >With a problem like this, surely there must be some defence!!! > One idea springs to mind if you know the time and direction of impact, get to the other side of the Earth PDQ! Or live in a polar climate, the chances of getting a direct hit should be a bit less, although similarly catastrophic to a perpendicular strike. I don't try to lie awake worrying about it though... Andy. +-------------------------------------------------------------------------+ | Haveland-Robinson Associates | Email: andy@osea.demon.co.uk | | Pine Cottage, Osea Island, Essex | ahaveland@cix.compulink.co.uk | | CM9 8UH England. 0621-88756 | Also: 081-800 1708 081-802 4502 | +-------------------------------------------------------------------------+ ------------------------------ Date: Sun, 26 Jul 1992 23:25:20 GMT From: russell wallace Subject: Whales (SETI) Newsgroups: sci.space In <9207251435.AA15413@cmr.ncsl.nist.gov> roberts@CMR.NCSL.NIST.GOV (John Roberts) writes: >-From: rwallace@unix1.tcd.ie (russell wallace) >-Subject: Re: Whales (SETI) >-Date: 23 Jul 92 21:10:39 GMT >-Organization: Trinity College, Dublin >-Whales are _not_ intelligent in any significant sense of the word. If >-they were, they could prove it in about 30 seconds, by any number of >-means (e.g. whistle the prime numbers, *-* *-*-* *-*-*-*-* etc. - for >-that matter just whistle the numbers from 1 to 10). In fact, if they >-were intelligent, since they were physically quite a lot tougher than >-the whaling ships of the 18th and 19th centuries, they could have >-developed tactics to defeat them (e.g. several whales surround a whaling >-ship and clobber it, rather than all the whales trying to dive, and the >-ship gets one of them). >Again, one shouldn't expect all whales to have the same level of intelligence. >It has been reported that there was once a group of killer whales that >cooperated with a family of Australian whalers over the course of several >generations. They would help to round up the big whales to be killed, then >eat the leftovers. Rival whalers encroaching in the territory were driven off >by the killer whales. A better explanation might be that the whalers trained the killer whales to do this, in the same way that humans can train dogs to help them hunt on land. Killer whales can certainly be trained to do the sort of things that dogs can be trained to do. >Whales clearly lack some of the intellectual capabilities of humans (for >instance, humans don't appear to be prone to mass beachings). It would be >interesting to find out what capabilities they do have, for instance in the >area of abstract reasoning. It certainly would. As I said, I think that so far there is no evidence that they have any reasoning abilities at all. -- "To summarize the summary of the summary: people are a problem" Russell Wallace, Trinity College, Dublin rwallace@unix1.tcd.ie ------------------------------ Date: Sun, 26 Jul 1992 23:19:22 GMT From: russell wallace Subject: Whales (SETI) Newsgroups: sci.space In <13691@mindlink.bc.ca> Nick_Janow@mindlink.bc.ca (Nick Janow) writes: >rwallace@unix1.tcd.ie (russell wallace) writes: >> Whales are _not_ intelligent in any significant sense of the word. If they >> were, they could prove it in about 30 seconds, by any number of means (e.g. >> whistle the prime numbers, *-* *-*-* *-*-*-*-* etc. - for that matter just >> whistle the numbers from 1 to 10). In fact, if they were intelligent, since >> they were physically quite a lot tougher than the whaling ships of the 18th >> and 19th centuries, they could have developed tactics to defeat them (e.g. >> several whales surround a whaling ship and clobber it, rather than all the >> whales trying to dive, and the ship gets one of them). >That doesn't prove that they are not intelligent. They could have reasons for >letting men kill them; reasons that they understand but we don't. Look at all >the absurd things humans do in the name of religion. Aliens judging humans by >a few religious fanatics might decide that humans aren't intelligent. :) By that argument, you could suggest that chairs are intelligent, but for reasons we do not understand choose not to reveal that intelligence, and instead let humans sit on them and push them around. I would suggest that there is absolutely no reason to believe whales are intelligent, and that furthermore they definitely do not do certain things that can reasonably be regarded as showing intelligence, such as using it to preserve their lives (when humans evolved intelligence, this was the *first* thing we use it for), and that therefore it is reasonable to conclude that whales are not intelligent, unless and until we find some evidence that they are. (You make suggestions about aliens judging humans by a few religious fanatics. It isn't just a few whales that have been killed by whaling ships, it's thousands of whales, of many different species, in areas separated by thousands of miles.) -- "To summarize the summary of the summary: people are a problem" Russell Wallace, Trinity College, Dublin rwallace@unix1.tcd.ie ------------------------------ End of Space Digest Volume 15 : Issue 041 ------------------------------