--------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00137 Date: 04/17/98 From: MARTYN HARRISON Time: 05:59pm \/To: BARTON PAUL LEVENSON (Read 1 times) Subj: BB theory BPL> MH> stars, there wouldn't be a bright star (or cluster of dim stars just a BPL> MH> bright) in every direction. We can't eve see the centre of our own BPL> MH> galaxy due to dense clouds of (?) dust. BPL>With infinite amounts of time available, or even very large amounts of time BPL>any dust or dead objects in the way would have heated up to the same BPL>temperature as the surface of a star. Dust in the way thus does not BPL>effectively answer Olbers's Paradox. This was investigated extensively n BPL>19th century. But surely, in an expanding universe, energy density can rise or fall or obey distribution patterns, etc etc, rather than everywhere reaching infinitely high temperatures? It's irrelevant anyhow, I'm not arguing for a steady state universe because there are major problems with those anyway, not least being the notion that we'd have been colonised an infinite number of times already. --- * OLX 2.1 TD * Oh, you're using a PC! No wonder you can't find it... * Origin: Ooh! London. [Free E-Mail + UseNet] 0181-395-3108 (2:254/233) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00138 Date: 04/17/98 From: MARTYN HARRISON Time: 06:07pm \/To: BARTON PAUL LEVENSON (Read 1 times) Subj: A 5th force? BPL> MH> way, but at the moment it's another pointer away from the standard big BPL> MH> bang model. BPL>No it isn't. The Big Bang doesn't depend on the rate of increase being eit BPL>increasing or decreasing. Sure it does, that's why the big bang is a big bang. It has to be a massive outpouring of energy in order to still be expanding all these years later. The whole hubble value thing is based on the assumption that the universe has been expanding since the big bang at a gradually slowing rate. In reverse, the expansion is faster and faster as you approach the high speeds of the early periods. To find that expansion is speeding up invalidates the model entirely. Here's the analogy. If you draw a graph of arctan(x), by measuring the curve at some point and inferring the curve of arctan(x), you discover that at the origin, you tend towards a vertical line. This would be the very hot and very dense big bang, implied by the curve and the present slope angle. You calculate the position of the origin relative to where you are now and derive an age, and then you go looking for secondary evidence to support your theory that the graph tends towards a vertical line at the origin. However, if you find the curve is going the wrong way, a completely different curve emerges, and you no longer have the vertical line at the origin. In fact, you might end up with a curve which tends towards zero at the negative maximum, i.e. a horizontal line. Someone might want to work on that analogy for me, it doesn't sound very visual. :) --- * OLX 2.1 TD * You can't teach an old mouse new clicks * Origin: Ooh! London. [Free E-Mail + UseNet] 0181-395-3108 (2:254/233) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00139 Date: 04/17/98 From: MARTYN HARRISON Time: 06:14pm \/To: BILL GODFREY (Read 1 times) Subj: Big Bang BG> MH>> minimum size, yes? In other words, you cannot take the works of BG> MH>> Shakespeare and compress them to a file of a single bit. BG>Indeed you can... BG>void compress(char *indata, char *outdata) BG>{ BG> if (strcmp(indata,COMPLETE_WORKS_OF_SHAKESPERE) == 0)) BG> strcpy(outdata,"0"); BG> else if (strcmp(indata,COMPLETE_WORKS_OF_DIKENS) == 0)) BG> strcpy(outdata,"1"); Yeah yeah, point taken. The clever part is in deriving all the text from this initial single digit (or lack of complexity in the starting properties of the big bang). I bet you can't write the unpacker so quickly :) --- * 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: F5G00140 Date: 04/19/98 From: SIGHARD SCHRAEBLER Time: 08:43pm \/To: MIKE ROSS (Read 1 times) Subj: Z-Machine Hi MIKE ROSS@1:167/133, Du schriebst am 17.04.98 zum Thema "Large Asteroid": MR> > PHYSICS NEWS UPDATE MR> > The American Institute of Physics Bulletin of Physics News MR> > Number 366 April 9, 1998 by Phillip F. Schewe and Ben Stein MR> > MR> > IN SANDIA'S "Z" MACHINE millions of amps of current are MR> > passed through a tiny spool of tungsten wires, producing a flood of MR> > x rays. Essentially the most powerful terrestrial producer of x MR> > rays, the Z device recently achieved the following milestones during MR> > a test shot: temperatures of 1.8 million K, a power output of 290 MR> > terawatts, and an energy release of 2.0 megajoules. The researchers MR> > believe nuclear fusion could be attained inside the device (by MR> > bombarding a fuel pellet with x rays) if the conditions were pushed MR> > further, to temperatures of 3.5 million K and power levels of 1000 MR> > terawatts. Sandia officials have encapsulated these ideas in a MR> > proposal for a larger machine, to be called X-1. (Sandia press MR> > release, April 9.) Are you shure thats not an april-joke? What size should this z-machine be and how is is thermically shielded? How many femtoseconds should wires (!!!) resist an power output of 290 terawatts. And why is an inductor spool producing gamma-rays in spite of magnetic fields. There are some april-jokes to be uncovered since Windows 95 :_) cu Sighard --- CrossPoint v3.11 * Origin: Lebbe geht weiter (2:244/1124.22) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00141 Date: 04/20/98 From: BARTON PAUL LEVENSON Time: 07:09pm \/To: SID LEE (Read 1 times) Subj: Asteroid passing close to SL> Mass of rock = 1.38x10^15 kg SL> Kinetic Energy = 0.5mv^2 SL> = 6.22x10^23 joules SL> = 1.49x10^23 cal SL> Specific heat of air = 0.21 cal/gm (approx) SL> The strike puts most of the energy into the ground but a large SL> fraction of that "ground" immediately goes into the atmosphere SL> and the heat with it so in reality much of the heat goes into SL> the atmosphere after first heating the "ground". Lets assume SL> it all does. You are assuming: A) That all the energy is thermal energy. This is incorrect. Some of it will be released as visual energy and TV-wavelength, and this will leave via the atmosphere, which is transparent to those wavelengths. Some will go into mechanical deformation of the material at the impact point. B) That transmission of heat to the atmosphere is perfect. You haven't accounted for optical thickness or water vapor content, both of which are likely to be extremely high in the vicinity of the blast. C) That the energy just kinds of stays there. A lot will radiate away as the heated air expands (and of course the energy of expansion will also take some energy). I reiterate that the air antipodal to the impact will not be significantly heated. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00142 Date: 04/20/98 From: BARTON PAUL LEVENSON Time: 07:12pm \/To: MIKE ROSS (Read 1 times) Subj: Re: Are atoms expanding? [1/2] BPL> I'm not kidding. According to relativity theory BPL> the speed of light in BPL> vacuo is constant for all inertial frames of reference. MR> Theory today does not say that the speed of light is constant. It says MR> that it is "a constant of free space". This is a big difference in MR> meaning. Because the moment one introduces another component in that MR> "free space" the speed of light is affected by it. A number of MR> phenomema have been observed which confirm it and are fundamental to MR> QED. Cite a source which said the speed of light in vacuo as observed from an inertial frame of reference was ever observed to vary. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00143 Date: 04/20/98 From: BARTON PAUL LEVENSON Time: 07:13pm \/To: TIM EDWARDS (Read 1 times) Subj: Re: Are atoms expanding? BPL>I'm not kidding. According to relativity theory BPL>the speed of light in vacu BPL>constant for all inertial frames of reference. It BPL>does not vary with local BPL>gravity, and the article you posted doesn't say anywhere that it does. TE> Acording to Einstein, it does... his theory was verified by observation TE> _long_ time ago. Durring a solar eclipse, the positions of stars seen TE> past the solar limb are "moved away from the edge" because the part of No, it's according to Einstein that it doesn't! Who do you think invented relativity theory? TE> the wave closer to the Sun is slowed relative to the more distant TE> portions of the wavefront. Gravitational refraction also is involved in TE> the spreading of a quasar image into a ring around a intervening galaxy, TE> the effect is termed an Einstein Lens. Neither of these effects involve changes in the speed of light in vacuo. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00144 Date: 04/20/98 From: BARTON PAUL LEVENSON Time: 07:16pm \/To: TONY DUNLAP (Read 1 times) Subj: Capital punishment TD> Maybe. OTOH, a good dose of hysteria might be exactly TD> what we need! Those in the 1800's who were hanged for TD> stealing horses never stole any more horses, and I'd TD> bet that the people who saw the hanging never stole any TD> horses either! You'd be wrong. Every empirical study ever done of the phenomenon has concluded that capital punishment is not a deterrent. In England pickpockets used to work the crowds of people gathered to see pickpockets hanged. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00145 Date: 04/20/98 From: BARTON PAUL LEVENSON Time: 07:18pm \/To: MIKE ROSS (Read 1 times) Subj: Neutron stars >> electron-positron stellar wind. MR> ^^^^^^^^^^^^^^^^^ MR> "Yes, Virginia", there are electrons in neutron stars. No, there aren't. There is pair production in the neutron stars' atmospheres, however. --- Maximus 3.01 * Origin: SoundingBoard, Pittsburgh PA (1:129/26) --------------- FIDO MESSAGE AREA==> TOPIC: 180 ASTRONOMY Ref: F5G00146 Date: 04/21/98 From: ARNOLD G. GILL Time: 09:49am \/To: SID LEE (Read 1 times) Subj: Asteroid passing close to Hello Sid! On 18 Apr 98, Sid Lee wrote to Barton Paul Levenson: SL> Volume of rock = 5.24x10^11 m^3 SL> Mass of rock = 1.38x10^15 kg SL> Kinetic Energy = 0.5mv^2 SL> = 6.22x10^23 joules SL> = 1.49x10^23 cal SL> Specific heat of air = 0.21 cal/gm (approx) SL> it takes 210 cal to raise 1 gm of air 1000 deg C. So this SL> amount of energy will heat 7.08x10^17 kg of atmosphere 1000 SL> deg C. SL> How much is that? Lets simplify and assume the atmosphere is SL> at constant sea level pressure of 14 psi and it is 8 km SL> thick A simpler method uses surface pressure times the surface area of the Earth. This gives you the weight of the atmosphere, and thus the mass. Now, there is a small change in the gravitational constant as altitude increases, but this effect is minimal. The errors introduced would be less than the approximation you used. So, with a pressure of 101,300 Pa, an average radius of 6370 km, gives a weight of 5.2 x 10^19 N, or a mass of 5.3 x 10^18 kg (about one millionth the mass of the whole Earth). Using your energy values, the atmosphere of the Earth would be raised by an average 135 degrees, assuming isotropic distribution, no cooling, no external sources of heat, c. Your mileage may vary. Arnold G. Gill - astrophysician at play --- GoldED 2.41 * Origin: Got a sick star? Call the Astrophysician! (FidoNet 1:153/6.5)