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About Martin

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    I really like this quote from Colin Powell: What is the greatest threat facing us now? People will say terrorism. But are there any terrorists in the world who can change the American way of life or our political system? Only we can change ourselves.

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  1. Simon, welcome. Sisyphus and Mr.Skeptic are explaining things in words but you might also need to get some mental imagery. So I suggest you google "wright balloon analogy" and watch it for 3 or 4 minutes as the two 2D universe expands Then type a number 2 into the URL and get the second version "Balloon2", that has light in it. Little wigglers representing photons, that move across the 2D surface while it is expanding. Also you mentioned the special relativity (1905) speed limit. That does not govern the rate that distances can expand in the improved (1915) theory called genera
  2. Sometimes a user will refuse to admit they made an error and continue arguing. Not listen to what they are told. Misinterpret what is being said, take issue with strawmen, and so on. It gets to seem like they are arguing just for argument's sake. We need a place for posts that might arise this way, so we can move them here and take some time to think about it---see if the post might have merit, or arises from honest misunderstanding, or is just arguing for its own sake. So here's a thread for that kind of thing, so we can move posts here and check them out. And in some cases move them
  3. These links are old. The thread is dated. I will move it to the speculations trash and think what new resource links for QC and QG to post.
  4. As DH said, stop putting words in our mouths. Nothing wrong with isotopes being formed in iron core supernova. Didn't say there was. You seem more interested in arguing than in learning. DH already called troll. I have to reluctantly go along.
  5. ===quote DH== ... In fact, they produce quite a bit of iron. The iron is produced by the supernova event in the case of a pair instability supernova or a Type 1a supernova. ... ==endquote== I have been reading the first of those two references in post #25---the one about SN 2007bi. An important PISN (pair instab. SN) signature was the large amount of Nickel-56. Predicted by the PISN model. 56 is divisible by 4. 14 helium nuclei come together. Energetically favored. Ni-56 is made at the time of the explosion and decays over a few days to iron. I gather the PISN mode
  6. Steevey, you aren't listening. Please read post #17 again. When a high enough temperature is reached the gamma radiation is no longer efficient at supporting outer layers. And the hotter it gets the less effective fusion becomes at supporting outer layers. That is why your reasoning just now is bad. Your reasoning in this post is bad. A typical "non-metallic" core in this case might be primarily oxygen and around 100 solar masses. (star more massive, core say 100 solar). All that oxygen is potential fusion fuel. But the fusion energy is now being bled off into the pair creation
  7. I should have spoken more precisely. As I understand it they found that amount of patterning can occur randomly. As one paper said, to the extent that Penrose found concentric circles you could just as well find triangles or squares. There will always be randomly occurring patterns but it does not mean anything. So the papers contested the claim that the findings were significant. ==================================================================== I may be mistaken. PENROSE AND GURZADYAN posted a second paper today, answering their critics and maitaining that the observed pattern
  8. http://arxiv.org/abs/1012.1268 A search for concentric circles in the 7-year WMAP temperature sky maps I. K. Wehus, H. K. Eriksen http://arxiv.org/abs/1012.1305 No evidence for anomalously low variance circles on the sky Adam Moss, Douglas Scott, James P. Zibin Sean Carroll pointed these out. Looks like Penrose circles not confirmed. http://blogs.discovermagazine.com/cosmicvariance/2010/12/07/penroses-cyclic-cosmology/
  9. Thanks for the correction. Should have said wavelength. Since neutrinos are massive particles I'll just think of them as slowing down as they lose momentum, in contrast to light.
  10. Short answer is YES neutrinos lose momentum--from the standpoint of observers at rest relative to primordial light (CMB). Since neutrinos have mass, losing momentum means losing speed. An article I read a couple of years ago said that STEVEN WEINBERG in his textbook COSMOLOGY goes through the math for a general particle with mass, traveling over long period of time in expanding space and shows how it loses momentum (so speed) due to expansion. The author provided what he said was a more concise proof. It is not too surprising. People use this fact when they run simulations of
  11. In part your questions show me my understanding is inadequate. So I looked around and didn't find much. I did find this: http://www.scholarpedia.org/article/Accretion_discs I may find more later. You sound like you have it pictured in mind at least as well as I do, or did until reading the Scholarpedia on Accretion discs. My intuitive picture is based on the ideas of conservation of energy and of angular momentum. I know that around a BH there is a minimum circular orbit size, where stuff is circling at near the speed of light. I haven't done a back-of-envelope calculation to es
  12. Be careful about dismissing people if you don't always know what you are talking about, Steevey. Nobody knows it all (not me anyway.) Arch gave a fairly clear (if very brief) mention of the pair-instability hypernova mechanism. Indeed it is believed to proceed by a kind of chain reaction which in effect traps increasing numbers of gamma photons once they reach a certain threshhold energy---so they no longer help to support the outer layers by radiation pressure. The gamma photon reacts with an atomic nucleus to produce an electron positron pair. The particles and antiparticles in the
  13. You know an asteroid falling towards some other body when it hits can release enough heat to melt rock. It can melt part of the asteroid and part of the crater---even vaporize. That is just a small conversion of gravitational energy. How much energy depends (among other things) on the square of the escape velocity at the surface of the target body. The grav. energy in this context is what does the heating. It isn't just a "fancy talk" equivalence---it is a meaningful straight-talk equivalence. Nuclear fusion only gets you on the order of 1% of the mass converted to energy (gamma radiati
  14. Nice! Did you do the labeling on that diagram? Ned Wright's cosmology tutorial had some basic diagrams like that, but last time I looked it did not have the labeling with words like "distant galaxy" and "Milkyway". Ned Wright's diagrams had the teardrop shape lightcones, and the worldlines with little local forward lightcones along them. A light ray worldline passing one of those has to be running parallel to one side or the other of the small local triangle. The plot is with proper time and proper distance. It's a really good tutorial and the diagrams are a great help. But I haven't
  15. I defer to Spyman and only comment in support of his explanation, but yes and you can figure for yourself that since the redshift z = 8.6 the surrounding galaxies were about 10 times closer than today on average. The relevant ratio is z+1 = 9.6 or about 10. You are talking about the universe at redshift 8.6 when it was already about 600 million years into its expansion history (correct me if you mean something else.) So the CMB radiation would have a temperature 10 times hotter. Today it is about 2.75 Kelvin. So back then the microwave soup around you would be 27.5 Kelvin. Still
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