--------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4B00013 Date: 04/06/98 From: JIM VAN NULAND Time: 10:12pm \/To: JOHN PAZMINO (Read 1 times) Subj: Where? >JV> You need to get in touch with your local astronomy club. They may be >JV> running a beginner's class! Hit your library and look for the back-file >JV> of Sky & Telescope magazine, or of Astronomy. They used to have have >JV> lists of clubs: the May issue of Astronomy, and the September issue of >JV> S&T. [...] >A bit out of date. The two zines dropped their club rosters two years >ago! But you do note the ebsites, which do continue the roster. Yes, I know they'd dropped the ball, er, club rosters. But since this is Fidonet, it's quite possible that the reader may not have access to the web sites. So I give both, in the hope that the library would have a few years of back-files. * SLMR 2.1a * What astronomers see is out of this world! --- Maximus/2 3.01 * Origin: [PC-TIE BBS] (1:143/11) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4B00014 Date: 04/06/98 From: MARTYN HARRISON Time: 11:24am \/To: JONATAN T. ALLIK (Read 1 times) Subj: A 5th force? [1/2] JTA> MB> A mysterious force is NOT needed to explain the acceleration, or JTA> MB> deceleration, of the expansion of the universe. Einstein thought JTA> MB> the universe was static - neither expanding nor contracting - and JTA> MB> thought there must be a fifth cosmological constant for the niverse JTA> BPL> This is dead wrong. If lambda is non-zero there is a fifth force JTA> BPL> driving it. JTA>Lambda? Just getting into the topic... Jargon. The universe "should" follow Newtonian laws of motion with adjustments for Relativity where these are significant. However, this requires a Big Bang so that as the universe expands, the rate at which this expansion takes place should be gradually slowing down due to the force of gravity between the various objects. It starts of expanding very fast and gradually slows down, yes? The new information suggests that rather than a faster expansion rate in the past, it was actually slower and that the rate is increasing rather than decreasing. This is consistent with various recent-ish reports, such as the age of some specific types of star being easy to determine but as older than the universe was thought to be. It's not consistent with the Big Bang model of creation, though, and so will require significant changes to cosmology in order to be incorporated, or the new findings are not right after all. Nobody here knows, most likely. JTA>I think you mean that more speed means a fifth force. I just heard about th JTA>faster expansion yesterday, I couldn't belive it. I get surprised when I re JTA>it here. Even a desacceleration may be possible (take this as a cuestion JTA>also), let's say some big black hole is hidden besides something in the mid JTA>of the expansion and points the center of it... and it atracts all galaxies JTA>Is that possible? Sure, and should happen. Once you have mass in a universe it's expansion is hindered by the gravitation potential energy you have to pump in in order to pull the various components apart. In the standard model, this energy comes from the huge initial kinetic energy coming from the explosion of space-time. If not, then a new energy source must be located. People are talking about a fifth law of nature analgous to anti-gravity, but what they do not seem to appreciate is that the force is *doing real work* i.e. supplying energy to fuel expansion. This isn't plausible with a "cosmological constant" because it has no energy source to draw upon. JTA>I used to think (obviusly with my leak of knowledge in mind) that some day, JTA>all the mass going out from the starting point, being atracted with time, a JTA>then, when all were there again, another big bang came. The neverending sto JTA>Of course: OR NOT, a forever expansion. For now I'll wait to someone for JTA>answer this. The "stuff" may crunch again, but entropy marches on with time. When all the material combines again it will have (much) less energy than it is supposed to have started with, and will not reboot the universe again. JTA>Excuse my english, not a speaking one. You're doing well. JTA> MB> It does no such thing at all. JTA> BPL> It sure does. If the expansion is accelerating Einstein was wrong JTA> BPL> to take out the cosmological constant, lambda. JTA>So, that's lambda! :) Nah, lambda adjusts the universe to a non-expanding steady state. It's obviously expanding even in the past. JTA> MB> There is no reason to think that the matter of our observable JTA> MB> universe has more power than the matter in the part of the universe JTA> MB> we cannot see. If the universe we observe was a BB (a little JTA> BPL> Excuse me, a hyper-large attractor can't be powering a uniform JTA> BPL> expansion in all directions, which is what we see with the Hubble JTA> BPL> shift. JTA>It's that for sure? So, the big bang point is known? Nope. Some will tel you so, but it's only a theory (in academic tests, best to quote the standard model. In research, best to question it. The big bang is gospel truth, as it were, in the same way that not all of the gospels are true but they are when the Inquisition asks you). JTA> MB> galaxies - they are not looking at what is happening "now". This JTA> MB> is why their basic conclusions are not acceptable in their JTA> MB> current form - and it is why the writer of this article is JTA> MB> speculating. JTA> BPL> The writer of the article knows what he's talking about. I'm JTA> BPL> sorry to say that, from what you've written here, you don't. JTA>Well... I agree with what we are getting from the space. The more far the JTA>object is, the more time we take to see it in a specific moment. Yep. Looking back in time the further away we look. This is why the expansion rate "in the past" can be measured and compared with the expansion rate "in the present". The results may be questioned, but the logic of the findings is 100% accurate rather than speculation. This is not to say that there is a problem with the big bang just yet, merely that the measurements do point to a different cosmology instead of the big bang. When someone starts suggesting dropping relativity in favour of retaining the big bang, you can start to accept the measurements as accurate, IMO. JTA>Is there any news about what's going on with the speed of the galaxies? Hanging about on usenet gets you lots of information, but lots of it is misleading. I daresay Hawking will cover it in his next book? --- * OLX 2.1 TD * C:\ is the root of all evil * Origin: Ooh! London. [Free E-Mail + UseNet] 0181-395-3108 (2:254/233) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4B00015 Date: 04/06/98 From: MARTYN HARRISON Time: 11:31am \/To: JONATAN T. ALLIK (Read 1 times) Subj: where? JTA>I have recently read some of the echos in the area, and some discussion wer JTA>definetly out of my reach. I uso some time on the web, and get more trouble Probably not out of your reach. JTA>So, where do I find good and somehow easy info about astronomy on internet? JTA>And, what books will be good to star with? I'm not intersted in getting JTA>something like a telescope if I don't know in what use it. Well this is an astronomy echo, rather than cosmology, but there's a lot in common. JTA>I guess some phisics book will have some info, I'll start with them. But JTA>definitely don't know how this topic is taken over in diferent books and JTA>authors. Stephen Hawking writes well-known books, and is easy to get hold of copies (A Brief History of Time, f'rinstance) but he's quite a speculator and it's tought stuff for the novice. A better source is an american lecturer who's name escapes me but will surely be mentioned by others. There are quite a lot of books on the market with "black hole" in their title, which tend to be good science as people after sensationalism are put off by black holes. Avoid anything with the word "pyramid" in the title, unless you are good at wrangling :) Other good sources are (not surprisingly) reference books published recently or online. For instance, the Encyclopedia Brittanica is remarkably current and comes on CD rom. It has the added advantage of being reasonably conventional and covers a whole load of things on top of cosmology. --- * OLX 2.1 TD * Please register! Evaluated for 37,923 days and counting * Origin: Ooh! London. [Free E-Mail + UseNet] 0181-395-3108 (2:254/233) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4B00016 Date: 04/07/98 From: MIKE ROSS Time: 12:30am \/To: BARTON PAUL LEVENSON (Read 1 times) Subj: Re: ASTEROID PASSING CLOS Barton Paul Levenson said the following to Lance Reynolds on the subject of ASTEROID PASSING CLOS (05 Apr 98 06:15:04) BPL> Say the asteroid is 1,000 meters in diameter and roughly spherical, BPL> with a density equivalent to that of surface rocks on the Earth (about BPL> 2,800 kilograms per cubic meter). The volume of a sphere is (4/3) pi BPL> r^3, or here about 5.236 x 10^8 m^3, giving it a mass of around 1.4661 BPL> trillion kilograms. With the velocity cited earlier, the kinetic BPL> energy is 6.5974 x 10^20 Joules. A difference of 3.9584 x 10^17 BPL> Joules must be made in its kinetic energy. By the conversion factor BPL> cited, this is about 94 megatons of explosive energy. BPL> Assuming no conversion of the bombs into shaped charges, the BPL> efficiency of transfer would probably be low, perhaps 10%. Therefore BPL> 940 1-megaton bombs would be needed. Since we and the Russians BPL> between us have about 50,000 warheads available, many in that yield BPL> range, deflecting the asteroid is well within our capabilities. Under the old (Dr.Strangelove) doomsday philosphy of MAD (Mutually Assured Destruction) each side had something like 1,000 times overkill (before SALT and SALT-II). The then best cobalt devices were in the 60+ megaton range. Today's state of the art probably double or triple that old figure. It thus requires much less than 940 devices. Maybe 10 or so. However, quite obviously it's much too risky to launch such a dangerous payload. The safer solution is either solar powered ion engines or atomic rockets. --- Blue Wave/DOS v2.30 * Origin: Juxtaposition BBS. Lasalle, Quebec, Canada (1:167/133) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00000 Date: 04/06/98 From: BARTON PAUL LEVENSON Time: 05:33pm \/To: CHRISTOPHER GREAVES (Read 1 times) Subj: ASTEROID PASSING CLOS LR>able to make the roid into pieces small enough to not hurt when they LR>hit. I didn't think of just knocking it off its path. CG> I have a small problem with this. There is a big blob of energy, CG> in the form of rock, coming straight at me. You are going to ADD CG> energy to it (40 Nukes?) and then it will be LESS harmful? If it isn't headed straight for us, and it's unlikely that it will be, most orbits being curved, adding to the velocity will change the orbit, and is as likely to make it miss the Earth entirely as retarding the velocity. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00001 Date: 04/06/98 From: CURTIS JOHNSON Time: 08:37am \/To: MARTYN HARRISON (Read 1 times) Subj: BB theory BPL>This is wildly wrong. These calculations were carefully done in the 9th BPL>century and show that an old Universe should have a sky full of stars -- ev BPL>path in every direction eventually ends at the surface of a star. The BPL>microwave background is the echo of the Big Bang. It ain't starlight. Could I ask that right-hand margins be pulled in a bit by both parties? It creates problems when text is requoted. MH> An old universe won't have skies filled with stars because a star has MH> a given lifespan. Also, the distribution of material in the universe is MH> structured such that we cannot look in any direction without us MH> looking at a star, just that most of them are so dim that we can't see MH> them. Come to that, if you point in any direction, chances are you are MH> pointing at a galaxy much less a star. What Barton is referring to is known as "Olber's Paradox." No difficult calculations required, just the realization that the intensity of light fades only with the square of distance, whereas the volume of space increases with the square of distance. Yes, stars will appear dimmer with distance, but the increased number of stars will more than make up for this. New stars are also being created. And the greatest number of stars are white dwarfs, which have a lifetime greater than the age of the universe. BPL>MP> 4. The universe has too much large scale structure (interspersed BPL>MP> "walls" and voids) to form in a time as short as 10-20 billion BPL>MP> years. BPL> MH> Yep, I agree with this one. BPL>I don't. Neither do most of the astrophysicists who worked with the OBE BPL>data. MH> Have you done a survey? Anyway, since COBE was designed to prove the MH> big bang, it's hardly likely that they would try to dispute their own MH> belief on speculative grounds. COBE was designed to gather data. Ignore data at your peril. --- Blue Wave/DOS v2.30 [NR] * Origin: Nerve Center - Where the spine is misaligned! (1:261/1000) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00002 Date: 04/07/98 From: ARNOLD G. GILL Time: 03:08pm \/To: MIKE ROSS (Read 1 times) Subj: Are atoms expanding? Hello MIKE! On 06 Apr 98, MIKE ROSS wrote to A.G.G.: >> New scientist 28 March 1998 reports that a group of scientists have >> reported possible time-dependence of the fine structure constant >> after studying the spectra of quasars. Thanks for the report. If verified, it would make some very interesting changes in fundamental physics. Arnold G. Gill - astrophysician at play --- GoldED 2.41 * Origin: Got a sick star? Call the Astrophysician! (FidoNet 1:153/6.5) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00003 Date: 04/07/98 From: ARNOLD G. GILL Time: 03:17pm \/To: MARTYN HARRISON (Read 1 times) Subj: Stay on target.... Hello Martyn! On 01 Apr 98, Martyn Harrison wrote to Arnold G. Gill: MH> I get these about a week after they are posted. That's one of the problems of FIDO. MH> Is cosmology ok, i.e. shapes of universes as opposed to looking at ars? This is at the border of a gray area. Generally OK, but try to avoid pure philosophical arguments. Add in observational evidence, and I won't complain too much. :-) Arnold G. Gill - astrophysician at play --- GoldED 2.41 * Origin: Got a sick star? Call the Astrophysician! (FidoNet 1:153/6.5) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00004 Date: 04/07/98 From: ARNOLD G. GILL Time: 03:21pm \/To: MARTYN HARRISON (Read 1 times) Subj: A 5th force? Hello Martyn! On 02 Apr 98, Martyn Harrison wrote to Paul M. Davis: MH> Einstein was wrong, and his presumption that the universe was steady MH> state is still wrong. His fudge factor is wrong. MH> Whoever invented this notion that the fudge factor is equivalent to MH> the fifth force is also wrong, they're two entirely different fudge MH> factors, one is designed to "correct" maths which point towards an MH> expanding universe, the other is in response to the finding that the MH> expansion rate is being added to, not merely draining away due to MH> gravity. The motivation may be different, but mathematically, it is quite likely that they take the same form in the general relativity equations. At least, at this point in time. Arnold G. Gill - astrophysician at play --- GoldED 2.41 * Origin: Got a sick star? Call the Astrophysician! (FidoNet 1:153/6.5) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F4C00005 Date: 04/06/98 From: MARK KAYE Time: 09:25am \/To: ALL (Read 1 times) Subj: Skyline for 1998-04-03 Sky and Telescope's SKYLINE for 1998-04-03 Astronomers say that a picture taken by the Hubble Space Telescope's Wide Field and Planetary Camera 2 shows the youngest planetary nebula yet imaged. Dubbed the Stingray Nebula (Hen 1357), the sphere of glowing gas lies about 18,000 light years away in the southern hemisphere constellation Ara. The nebula is some 130 times the size of our solar system, but this is only about one tenth the size of other known planetary nebulae. Hubble has been the first telescope to provide a close look at this small nebula. Amid the complex structure that includes a ring and bubbles of gas, the image reveals that the central star is binary. Recently, astronomers have suggested that the presence of a companion is key in the creation of varied shapes of planetary nebulae. Another Hubble image, coupled with radio observations, show for the first time a complete Einstein ring. This phenomenon arises when the light from a background galaxy is bent around a foreground object by gravitational lensing. A precise lineup is required to form a complete circular "mirage" around the intervening galaxy. British researchers announced the finding at this past week's UK National Astronomy Meeting at the University of St. Andrews. They note that they used Hubble imagery and data from the UK's 200 kilometre wide MERLIN radio array to capture the remarkable sight. The Einstein ring is only about 1 arcsecond across. Results will be published in the April 1st Monthly Notices of the Royal Astronomical Society. For a ring of another sort, astronomers have found evidence for a previously unknown 1.1 million km wide ring of dust around Jupiter. Joshua Colwell (University of Colorado at Boulder) and his colleagues used data from dust detectors aboard the Galileo spacecraft to determine the quantity and motions of the particles. Computer models showed they the material formed a torus or doughnut shape. Perhaps the most curious aspect of the dust particles is that they orbit the planet retrograde or the reverse way from the other moons of Jupiter's satellite system. Details of the study appear the April 3th issue of Science. According to two University of Southampton astronomers, the Milky Way galaxy is not as big as previously thought. Michael Merrifield and Robert Olling examined studies of the motions of stars and conclude that the Sun is located some 23,000 light years from the centre of the galaxy and moving at about 185 km per second. These values are at the lower ends of the range of estimates from various studies. Such galactic depreciation could have wider consequences in the sizing of the universe. Amateurs continue to follow the supernova discovered on March 2nd in the galaxy NGC 3877 in Ursa Major. Supernova 1998S, an unusual Type IIn supernova, has been holding steady at 12th magnitude. The 11th magnitude galaxy is located just 0.3 degree due south of the star Chi Ursae Majoris. Supernova 1998S is 14" west and 46" south of the elongated galaxy's centre. Observers report that the supernova is easier to see than the galaxy itself. That is all for this week. MK --- Maximus 2.02 * Origin: http://www3.sympatico.ca/mark.kaye/ (1:249/109.1)