--------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00037 Date: 04/21/98 From: JOAN KELLY Time: 12:03am \/To: ALL (Read 1 times) Subj: This Echo Hello All! On April 24, our board will go Mail Only, and cease accepting callers. Since we are going to be taking echoes for ourselves alone, because of reading-time constraints, we're doing serious culling. This echo will be one of the casualties, unfortunately. I want to take this opportunity to thank the most helpful astronomy buffs here for continuing to help out the newbies. Special thanks to Jim Van Nuland, Sid Lee and Mark Kaye. All the best, folks. Joan --- timEd/386 1.10 * Origin: TNC - (860) 963-1187 - 2.4kbps-33.6kbps! (1:320/2112) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00038 Date: 04/19/98 From: TONY DUNLAP Time: 11:01pm \/To: MIKE ROSS (Read 1 times) Subj: Re: Planetary Alignment Hi MIKE, In a message to Martyn Harrison you wrote: MR> I've read/heard a news report of some statistical study of the Moon MR> triggering earthquakes question claiming a small though not MR> insignificant correlation. I think it was something like 15% though I MR> can't find the report now. That's certainly possible, since the moon is so close (it's responsible for 85-90% of tides). Later Tony Dunlap, (tdunlap@odot.dot.ohio.gov) --- * Origin: "There is no such things as a free variable." (1:2220/30.1) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00039 Date: 04/22/98 From: CURTIS JOHNSON Time: 01:53am \/To: BARTON PAUL LEVENSON (Read 1 times) Subj: White dwarfs -=> Quoting Barton Paul Levenson to Curtis Johnson <=- CJ> Now, the diagram is probably of *observed* closest stars. CJ> Because of their intrinsic low luminosity, white (not to mention CJ> brown) dwarfs are not easily visible. In fact, the nearest white CJ> dwarf (system) is the second-closest star (Barnard's star, BPL> I'm fairly sure Barnard's Star is of spectral and luminosity M5Ve, BPL> which would make it a young red dwarf. Of the stars within five BPL> parsecs, which we can be reasonably sure are a fairly complete list, 5 BPL> of 66 are white dwarfs (Sirius B, Procyon B, Van Maanen's Star, 40 BPL> Omicron-2 Eridani B and L145-141), at least according to Bishop (1988, BPL> The Observer's Handbook 1989, Toronto: The Royal Astronomical Society BPL> of Canada, p. 183). Aargh, you're correct, and I'll have to cease relying so much on my memory. And I did track down a second error in that statement (my mentioning it as a system) to having read in an old astronomical dictionary that it was an _optical_ double. My memory had dropped the optical. Because Barnard's has the greatest proper motion of any star, even that's probably not true. Aah, if only I'd gone ahead and read _Rocheworld_ by Robert L. Forward, a physicist, I wouldn't have made the blunder. It's about an expedition to Barnard's Star, which encounters a planet subject to an unusually strong tidal force. . . CJ> IIRC, Sirius B, a mere 8 LY away, was known--until recently, CJ> anyway--only through it's gravitational effects. BPL> True if you define "recently" appropriately -- it was photographed by BPL> Alvin Clark in 1862. Relative to Sirius A. BPL> The fraction of stars off the main-sequence is given as 10% by Allen BPL> (1973, Astrophysical Quantities, London: The Athlone Press). It is BPL> repeated in Lang (1992), but this is probably just repeating Allen's BPL> data. But then nearly all of Allen's is compiled from some other source. Oooh, you _have_ an Allen's? I once was able to leaf through one when I'd sneaked into a university library. --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00040 Date: 04/22/98 From: CURTIS JOHNSON Time: 02:17am \/To: ARNOLD G. GILL (Read 1 times) Subj: White dwarfs CJ>> New stars are also being created. And the greatest number CJ>> of stars are white dwarfs, which have a lifetime greater than CJ>> the age of the universe. BPL>> You were doing okay until you came to this point. According to BPL>> HR diagrams of the 10,000 or so closest stars, about 90% of BPL>> stars are on the main sequence, 9% are white dwarfs and 1% are BPL>> red giants. This doesn't count invisible stars, e.g. neutron CJ> I just flipped through three astronomy textbooks, without CJ> finding any answer. AGG> Barton is correct with his statistics. This has a lot to do with AGG> the finite age of the universe, the initial mass function, and the AGG> main sequence lifetime. By far the vast majority of stars (like 96% AGG> or so) on the Main Sequence (MS) are stars less massive than the Sun. AGG> However, these stars also have lifetimes on the Main Sequence of 10+ AGG> billion years - most have MS lifetimes longer than the age of the AGG> universe. Thus, by far the vast majority of stars are stars that have AGG> not yet evolved off of the Main Sequence, and so are not even close to AGG> becoming white dwarfs yet. I do believe I had "white dwarf" confused with "will become white dwarf" when I was trying to recall approximate population frequency. Been too long since I studied this stuff, I guess. --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00041 Date: 04/22/98 From: CURTIS JOHNSON Time: 04:32am \/To: MARTYN HARRISON (Read 1 times) Subj: BB theory CJ> Could I ask that right-hand margins be pulled in a bit by CJ> both parties? It creates problems when text is requoted. MH> Mine is fixed at 77, i.e. 80 columns less formatting. Being a dos MH> package this isn't alterable except to other terminal types beside MH> vt220, and is the VGA standard. I've no idea how to change it. :) Nothing to do with DOS--I'm using pure DOS myself. The setting would be in whatever text editor you're using with your OLR (off-line reader), and that should be changeable. I see that you're using a "test drive" OLR, and the text editor may not have this function, but it very well may. Most OLRs also let you use your own text editor, which will involve rather more fiddling. MH> HST, is anyone else having trouble? On usenet I tend to live with the MH> most atrocious formatting. If there are options, they will be to MH> pick 40 column or 132 column instead. HST = Hubble Space Telescope? 8-) 80 columns is the usual choice for screen width for monospaced characters--which is not usually the same as text margin any more than 8 1/2" is the right-hand margin for nearly all typewritten material. I didn't rework the material below. You should either see some atrocious formating (broken lines) or truncated lines. CJ> What Barton is referring to is known as "Olber's Paradox." MH> Indeed. My version of the paradox is that if the universe had been MH> around in it's present form for eternity, (a) it would already have MH> been colonised by space aliens an infinite number of times, (b) it MH> would consist of a series of orbiting super massive black holes and MH> nothing to provide gravitational drag (or a single, fat hole), or (c) MH> all the stars which had burned out during eternity would clutter up the MH> whole thing. A is sort of a restatement of a restatement of the Fermi paradox ("Where are they?"); a variant was proposed by Tipler who proposed self-reproducing machines. There's various possible resolutions; two are that intelligence does not automatically translate into space-faring technology, and cosmic catastrophes of various types (supernovae, etc.) keep things in equilibrium. (Also, dust clouds make near-light speeds rather difficult.) CJ> No difficult calculations required, just the realization that the CJ> intensity of light fades only with the square of distance, whereas CJ> the volume of space increases with the square of distance. Yes, CJ> stars will appear dimmer with distance, but the increased number CJ> of stars will more than make up for this. MH> Assuming none of them are occulted by dead stars. Doesn't really matter--dead stars would also be occulted by live stars. MH> stars, there wouldn't be a bright star (or cluster of dim stars just MH> as bright) in every direction. We can't eve see the centre of our own MH> galaxy due to dense clouds of (?) dust. The dust would still eventually heat up and glow (at a temperature far higher than the 2.7 K of the microwave background). And there is not enough dust to block out galaxies we can see that seem to be in the first stages of formation. CJ> BPL>MP> 4. The universe has too much large scale structure (interspersed CJ> BPL>MP> "walls" and voids) to form in a time as short as 10-20 billio CJ> BPL> MH> Yep, I agree with this one. CJ> BPL>I don't. Neither do most of the astrophysicists who worked with the CO CJ> MH> Have you done a survey? Anyway, since COBE was designed to prove the CJ> COBE was designed to gather data. Ignore data at your peril. There's an example of why R-hand margins should be brought in. MH> Sure, but nobody knows everything there is to know about everything, MH> and when you set out to prove things, evidence which is circumstantial MH> can be made to look supportive. This is where Occam's Razor comes in. MH> The analogous situation is like this: MH> MH> (Lengthy "analogy" deleted. . . there was no tie-in I could see to the actual situation that would make it an analogy.) Rather, it strikes that the analogous situation would be the jury attempting to determine whether an explosion has taken place. Convened on the site, they still see fragments flying radially away (red-shifted galaxies), a fading flash of light (microwave background), and the unmistakable smell of oxidized nitrate compounds (the hydrogen/helium ratio). --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00042 Date: 04/22/98 From: CURTIS JOHNSON Time: 06:39am \/To: BARTON PAUL LEVENSON (Read 1 times) Subj: Asteroid passing close to -=> Quoting Barton Paul Levenson to Curtis Johnson <=- CJ> There would most definitely be effects on the other side CJ> of the globe at the anti-impact point, in the form of considerable CJ> earthquakes. A good example of this is the chaotic terrain on CJ> Mercury opposite the Caloris Basin. CJ> Just to add to the above, some of the scientists working CJ> with the K/T meteorite scenario have contended that the fireball's CJ> heat would creat significant quantities of nitrous and nitric CJ> acid--resulting in acid rain. BPL> 1. Mercury is 1/20 the mass of the Earth and whatever hit it was a BPL> lot larger than a 1-km. asteroid. The "Weird Terrain" antipodal to the Caloris Basin (yes, dieters, Mercury is low in Caloris) is just an extreme example of the effect. The postulated K/T asteroid is more in the neighborhood of 10 km than one, and energy of impact would vary according to the *cube* of the diameter. The impressive lava flows of the Deccan Traps (about a kilometer deep) which have been proposed by Officer and Drake as an alternative to the K/T asteroid, are interpreted by K/T asteroiders as being caused by the antipodal effect. BPL> 2. Acid rain will be local, it will not travel as far as the BPL> antipodes. The effect would undoubtedly be greatest nearby. However, there is no question that material would jet up into the stratosphere and above and thereby be more widely distributed. Compare the dust (as opposed to NOx gas) distribution of the much smaller Krakatoa event. --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00043 Date: 04/22/98 From: CURTIS JOHNSON Time: 10:38am \/To: SID LEE (Read 1 times) Subj: Asteroid passing close to MR> I think it would produce some sort of radiation though not likely the MR> alpha and gamma stuff. The high speed plasma is sure to result in MR> powerful electromagnetic disturbances akin to EMP as the electrons are MR> stripped from the atmosphere's atoms. For example astronauts go SL> All true of course but electromagnetic disturbances are not SL> generally regarded as "radiation" in the nuclear or "atomic" SL> sense. X-Rays are part of the electromagnetic spectrum but since SL> they arise from energetic transitions of electrons rather than SL> the fission or fusion of nucleii they "don't count" either SL> though of course they are dangerous/lethal in sufficient SL> strengths ;-) Semantics police here: gamma, X-ray, and even the short end of UV are considered "ionizing radiation." There'd be X-rays from the bremsstahlung ("braking radiation") of the created plasma. Of course, that would be just icing on the cake of the local effects. --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00044 Date: 04/22/98 From: BARTON PAUL LEVENSON Time: 05:03pm \/To: SID LEE (Read 1 times) Subj: Asteroid passing close to BPL> B) That transmission of heat to the atmosphere is perfect. You BPL> haven't accounted for optical thickness or water vapor content, both BPL> of which are likely to be extremely high in the BPL> vicinity of the blast. SL> Perfectt or imperfect, it doesn't matter. It is in the system SL> and over time it is distributed throughout the system. The SL> "imperfection" simply stretches the time required. If the 1. It matters. 1% of the atmosphere, on average, at any given time, is water vapor. Water vapor has a much higher specific heat than air, so the temperature of the whole air mass will go up by less. 2. If it happens over time, as opposed to instantly, a lot of heat will be lost to radiation into space. The longer it takes, the lower the peak temperature attained. SL> atmosphere. Some indeed does radiate out into space but the SL> fraction which remains within the atmosphere is quite large and SL> easily within the range required to superheat the entire SL> atmosphere. Quantitative estimate, please. BPL> I reiterate that the air antipodal to the impact will not be BPL> significantly heated. SL> You are simply incorrect here. Read any of the many excellent SL> "popular" books and articles on the subject by people like SL> Shoemaker, Levy, Gibbons etc. The professional literature is SL> also filled with learned descriptions of the effect of impacts SL> of this size. I'm familiar with the professional literature on the subject. Having a degree in physics also helps, not to mention having studied astronomy and planetary sciences intensively for the last quarter century. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00045 Date: 04/22/98 From: MIKE ROSS Time: 05:02pm \/To: ARNOLD G. GILL (Read 1 times) Subj: Re: Big Bang Arnold G. Gill said the following to MIKE ROSS on the subject of Big Bang (21 Apr 98 10:00:16) AGG> Hello MIKE! AGG> On 19 Apr 98, MIKE ROSS wrote to Arnold G. Gill: MR> The oscillations I mentioned... Harmonic quakes in the crystal-like MR> solid outer neutronium crust? I wonder what geometric arrangement MR> results from the nucleic forces? AGG> There have been lotsa of ideas floated around of starquakes on AGG> neutron star surfaces, as the surface crystal readjusts itself to AGG> changes in stress due to, for example, slowdown of rotation, weakening AGG> of the magnetic field, crystal defects, etc. Unfortunately, neutron AGG> star conditions cannot be duplicated in the lab. It would be AGG> interesting to get a closer look at such an environment. Could the diameter continue to oscillate from a larger to a smaller value after the collapse of the electron orbits? For example if the density never quite makes it to the Black Hole criterion the collapse rebounds back and forth as an acoustic resonnance wave. How long could such an elastic oscillation persist? --- Blue Wave/DOS v2.30 * Origin: Juxtaposition BBS. Lasalle, Quebec, Canada (1:167/133) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00046 Date: 04/21/98 From: MARTYN HARRISON Time: 06:39pm \/To: EARL TRUSS (Read 1 times) Subj: Re: Physics News Updates ET>MH>And it's bound to occur to at least one of the "lots of species" that ET>MH>galactic conquest is a more lasting monument to the Q'in Thargg ET>MH>Dynnasty than a small colony of peaceful cohabitees, isn't it? ET>The above is an economically unfeasible concept. Please read "The ET>Forever War" by Joe Haldeman. I dunno, seems to me economics allows colonisation, after all it's a question of cost. Costs can be saved up. If one planet can colonise another, fifty thousand can colonise fifty thousand more. What's his main objection? --- * OLX 2.1 TD * What boots up, must come down * Origin: Ooh! London. [Free E-Mail + UseNet] 0181-395-3108 (2:254/233)