Aucbvax.6326 fa.space utcsrgv!utzoo!decvax!ucbvax!space Sun Feb 28 03:52:36 1982 SPACE Digest V2 #117 >From OTA@S1-A Sun Feb 28 03:46:17 1982 SPACE Digest Volume 2 : Issue 117 Today's Topics: quasars Shuttle News Quasars as spaceships re: quasars quasar beliefs quasar redshifts ---------------------------------------------------------------------- From: CARLF@MIT-AI Date: 02/27/82 15:54:34 Subject: quasars CARLF@MIT-AI 02/27/82 15:54:34 Re: quasars To: space-enthusiasts at MIT-MC In the most recent (or perhaps last week's) issue of Nature there are two articles on Arp's theory of the nearness of quasars, both unfavorable. The first article considers Arp's assertion that a survey of the sky in the vicinity of nearby galaxies shows a higher than average density of quasars, and thus that the quasars must be associated with the nearby galaxies. Arp claims that the data have one chance in 10^17 of happening by chance, but the article disagrees with this. It states that the probability of the data occuring by chance are about 1/2. The article's description of Arp's method of analysis makes it seem dubious even to me, though I know little of statistical analysis. The second article is of a statistical nature, and examines Arp's claim that several sets of three quasars lie almost on straight lines, and yet have very different redshifts, showing that redshifts must not correlate with distance. The article disputes Arp's claim that these alignments are immensely improbable. It argues that Arp has incorrectly analyzed his data. The suggestion that quasars might be interstellar spaceships going away from us makes me wonder why we don't see any coming toward us. Are we so frightening that everyone is running away, or is something ghastly going to happen to this part of the galaxy that we haven't noticed yet? -- Carl ------------------------------ Date: Sat Feb 27 08:22:09 1982 To: Space at MIT-MC From: ucbvax!ihnss!cbosg!harpo!npois!rabbit!sjb at Berkeley Subject: Shuttle News Source-Info: From (or Sender) name not authenticated. The unloading of supercold hydrogen and oxygen fuels went well, just as their loading did, leading the way for the last major step before the shuttle's countdown begins. Also tested out well were the three fuel cells and APU #1. The fuel cell that caused the problems during STS-2 had been replaced and all three overhauled to prevent a recurrence of that problem. If all goes on schedule now, loading of highly volatile fuels into the Columbia's maneuvering system will start next week. It was this loading of nitrogen tetroxide and liquid hydrazine that spilled during the pre-flight work of STS-2 and subsequently delayed its launch while workers fixed the tiles that were loosened during that accident. As of now, the work for STS-3 is still a bit ahead of schedule, giving a nice cussion if anything should go wrong. ------------------------------ Date: 27 Feb 1982 1722-PST From: Hans Moravec Subject: Quasars as spaceships To: space at MIT-MC One of the features of efficient rockets is a tightly collimated exhaust. A rocket that converted a high mass fraction of its fuel to energy (near photon drive) would emit mostly photons frequency shifted by the motion of both the photon source and the acceleration of the exhaust reflector/nozzle, and these photons would be like a searchlight beam streaming from the rear of the ship. This beam would be so bright compared to any other emission that it is probably safe to say that we could see the ship only when the exhaust is pointed straight at us. We would see a blue shift only if a ship was using its engines to decelerate along our line of sight. There may be better ways of decelerating than using mass quantities of fuel, things like an interstellar hydrogen parachute, or interaction with the galactic magnetic field, and these would render the ship invisible to our feeble sensors in the only blue shift case. Another, maybe significant, effect is relativistic beam angle aberration. A source with a given beam angle seems to have a narrower beam when it is coming at you and a wider angle when moving away. Thus we have a greater chance of seeing a red shifted receding beam source than a blue shifted approaching one. ------------------------------ Date: 28 Feb 1982 00:24:14-PST From: decvax!utzoo!utcsrgv!dudek at Berkeley To: utzoo!decvax!ucbvax!space@Berkeley Subject: re: quasars Cc: decvax!utzoo!utcsrgv!ings@Berkeley Is this where to send space disgest stuff? There was an article in the Canadian Journal of Physics about 2 years ago (I'll try & find it) postulating that quasars could be accounted for as a statistical anomaly in the way spectral data was identified. Essentially, I think the thesis was that the "supposed" red shifts were identified by matching observed spectral lines with known arrangements and then finding out how much the familiar configuration was shifted up the spectral scale. The author claimed that a number of spurious random matches could account for "quasars", and in fact the number of known quasars jived with this explanation. Gregory Dudek UNIX. of Toronto ..decvax!utzoo!utcsrgv!dudek ------------------------------ Date: Fri Feb 26 16:14:44 1982 To: Space at MIT-MC From: ucbvax!decvax!utzoo!henry at Berkeley Subject: quasar beliefs Source-Info: From (or Sender) name not authenticated. I know nothing about the facts of the particular case of the astronomer who may lose his observing time because of unconventional beliefs about quasars. But it is worth remembering that just because somebody holds unconventional beliefs about some sacred cow does NOT mean that his research is well-organized, properly thought out, and deserving of observing time. If his observing time is imperiled BECAUSE of his views, that is deplorable. But don't forget that there may be a simpler and less dramatic explanation. I confess to a strong suspicion myself that the standard "cosmological" explanation of quasars is incorrect, but that does not blind me to the possibility that people who agree with me may not be organizing their work well enough to deserve time on scarce and expensive facilities. ------------------------------ Date: Fri Feb 26 16:44:01 1982 To: Space at MIT-MC From: ucbvax!decvax!utzoo!henry at Berkeley Subject: quasar redshifts Source-Info: From (or Sender) name not authenticated. The two possible explanations of the quasars given a few days ago missed a third: that the red shifts really are Doppler effect, but this does not correlate with distance the way it does for galaxies. In other words, you can eliminate the need for a non-Doppler redshift mechanism if you can devise a way of accelerating starlike objects to substantial fractions of c (interactions with the magnetic field of an exploding galactic core?). At one time this was a respectable theory; I don't know its current status. One problem is that one should then see some blueshifted objects as well, although one can fend this off by claiming that we aren't looking at the right wavelengths to see the major emissions of a massively blueshifted object. How this explanation stands in the presence of increasing astronomy efforts in the UV and X-rays, I don't know. Any attempt to avoid the "cosmological" explanation of quasars also needs to bear in mind that things like the recent case of double images of a quasar being formed by gravitational lens effects of a distant galaxy DO put a lower bound on the distance of SOME quasars. ------------------------------ End of SPACE Digest ******************* ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. 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