Soupy1957 Posted January 11, 2018 Report Share Posted January 11, 2018 (edited) I’m one of those folks we never paid attention in science class back in school. Now at 61 years of age, I have been inspired by the likes of people such as Neil Degrasse Tyson. I suppose over the years I have paid attention to scientific concepts and principles, but I haven’t tried to dissect or decipher them. I HAVE spent a certain amount of time studying the stars, at least as far as being able to identify constellations and so forth, but that’s about the extent of my cosmic journey. I could show somebody the big dipper and Orion and maybe even the Little Dipper if I’m lucky. I could point someone towards M31, where the nearest galaxy is to ours, if I recall correctly. I’m only up to page 52 of Neil’s book “astrophysics for people in a hurry” ( which says something about the kind of “hurry“ I am in..........lol), And he continues to talk about the precisely measured temperature of microwaves. He says and I quote, “if you’re numerically lazy, nobody will fault you for rounding the temperature of the universe to 3°.“ he’s talking about CMB (Cosmic Microwave Background), But I can’t tell you that I know anymore about THAT, then I did a half an hour before I read it. Because I’m not a scientist and I don’t fully understand, is he saying that if an astronaut was floating out in space and happened to be exposed to space, It would feel like 3°F? Just wondering… Edited January 11, 2018 by Soupy1957 Quote Link to comment Share on other sites More sharing options...
exchemist Posted January 11, 2018 Report Share Posted January 11, 2018 (edited) I’m one of those folks we never paid attention in science class back in school. Now at 61 years of age, I have been inspired by the likes of people such as Neil Degrasse Tyson. I suppose over the years I have paid attention to scientific concepts and principles, but I haven’t tried to dissect or decipher them. I HAVE spent a certain amount of time studying the stars, at least as far as being able to identify constellations and so forth, but that’s about the extent of my cosmic journey. I could show somebody the big dipper and Orion and maybe even the Little Dipper if I’m lucky. I could point someone towards M31, where the nearest galaxy is to ours, if I recall correctly. I’m only up to page 52 of Neil’s book “astrophysics for people in a hurry” ( which says something about the kind of “hurry“ I am in..........lol), And he continues to talk about the precisely measured temperature of microwaves. He says and I quote, “if you’re numerically lazy, nobody will fault you for rounding the temperature of the universe to 3°.“ he’s talking about CMB (Cosmic Microwave Background), But I can’t tell you that I know anymore about THAT, then I did a half an hour before I read it. Because I’m not a scientist and I don’t fully understand, is he saying that if an astronaut was floating out in space and happened to be exposed to space, It would feel like 3°F? Just wondering…Well not 3F, but 3K. If you were shaded from any nearby stars. 3K means 3 degrees Celsius above absolute zero, which is the temperature at which there is no heat energy left in a body. So 3C above that is -270C, or -454F. Space itself, being a vacuum and not made of matter, can't really be said to have a true temperature in the strict sense. But the cosmic background radiation that pervades space is the same as the heat radiation from a body at about 3K. So if a piece of matter (a piece of rock for example) were exposed only to that radiation, that is the temperature it would end up at, once it had reached thermal equilibrium with the radiation. If it were not for the big bang, one would not expect there to be any such radiation. So people in the past would have expected that a shaded body in space would radiate heat away until its temperature had dropped to absolute zero itself. The fact that there is this radiation rattling around the universe and apparently coming from everywhere, not from any identifiable source, is a key piece of evidence for the big bang hypothesis. Edited January 11, 2018 by exchemist sanctus and studentgary 2 Quote Link to comment Share on other sites More sharing options...
Soupy1957 Posted January 11, 2018 Author Report Share Posted January 11, 2018 Thank you “exchemist” For the detailed explanation. At the risk of pushing a Forum “no-no” boundary, but since you opened the doorway, I will admit to being a creationist, who happens to believe that the “big bang” is completely logical, (imho) and merges (for me) the findings of science, with the limitless Omnipotent character of a Superior Being, (God) who did it all. I realize I’m probably a rare breed, but it is what it is. Anyway, back on topic, -400+ degrees, is pretty darn cold!! Quote Link to comment Share on other sites More sharing options...
exchemist Posted January 11, 2018 Report Share Posted January 11, 2018 Thank you “exchemist” For the detailed explanation. At the risk of pushing a Forum “no-no” boundary, but since you opened the doorway, I will admit to being a creationist, who happens to believe that the “big bang” is completely logical, (imho) and merges (for me) the findings of science, with the limitless Omnipotent character of a Superior Being, (God) who did it all. I realize I’m probably a rare breed, but it is what it is. Anyway, back on topic, -400+ degrees, is pretty darn cold!!Yes, well creationists are practically never scientists. I've met one, I think, who was both. But funnily enough, one of the concerns among scientists when the CMBR was discovered was that it might give an impetus to creationism. It certainly strikes me as not wholly unreasonable to make some metaphysical speculations about what, if anything, could have caused the big bang. A lot more reasonable than trying to argue that life could not have arisen without supernatural intervention. For that proposition, I have no time whatever. Quote Link to comment Share on other sites More sharing options...
bangstrom Posted January 31, 2018 Report Share Posted January 31, 2018 Space itself, being a vacuum and not made of matter, can't really be said to have a true temperature in the strict sense. But the cosmic background radiation that pervades space is the same as the heat radiation from a body at about 3K. So if a piece of matter (a piece of rock for example) were exposed only to that radiation, that is the temperature it would end up at, once it had reached thermal equilibrium with the radiation. If it were not for the big bang, one would not expect there to be any such radiation. So people in the past would have expected that a shaded body in space would radiate heat away until its temperature had dropped to absolute zero itself. The fact that there is this radiation rattling around the universe and apparently coming from everywhere, not from any identifiable source, is a key piece of evidence for the big bang hypothesis. People in the past did not expect a shaded body to radiate its heat away until its temperature dropped to absolute zero. Any attempt to shade a body would eventually fail once the temperature of the shade reached the equilibrium temperature of that point in space and then the shade would become a radiant body itself. A shade would only work if it were a perfect insulator, in which case, the body (rock) would never cool. Astronomers had several predictions about the absolute lowest possible temperature in deep space and their estimates centered around 3K until 3K was identified as as the CBR from the BB which should be a second source of energy for a total background temperature of 6K. So how could a universe with more than 200 billion galaxies have a background temperature of absolute zero if one subtracts the temperature of the CBR?Where is the energy from the galaxies going? https://www.ifi.unicamp.br/~assis/Apeiron-V2-p79-84(1995).pdf Quote Link to comment Share on other sites More sharing options...
exchemist Posted February 1, 2018 Report Share Posted February 1, 2018 (edited) People in the past did not expect a shaded body to radiate its heat away until its temperature dropped to absolute zero. Any attempt to shade a body would eventually fail once the temperature of the shade reached the equilibrium temperature of that point in space and then the shade would become a radiant body itself. A shade would only work if it were a perfect insulator, in which case, the body (rock) would never cool. Astronomers had several predictions about the absolute lowest possible temperature in deep space and their estimates centered around 3K until 3K was identified as as the CBR from the BB which should be a second source of energy for a total background temperature of 6K. So how could a universe with more than 200 billion galaxies have a background temperature of absolute zero if one subtracts the temperature of the CBR?Where is the energy from the galaxies going? https://www.ifi.unicamp.br/~assis/Apeiron-V2-p79-84(1995).pdfYes fair comment indeed about the idea of a "shaded" body. I suppose I was trying to make a simple explanation without thinking it through carefully enough and hence glossed over the difficulties. But regarding the question of "Where does the energy go?", surely if you have a pre-Big Bang model in which the universe is unbounded, then that energy can dissipate indefinitely, can't it? So there is no reason for it come "back" from anywhere, once emitted. Furthermore the radiation of these bodies does not have the observed microwave black body spectrum. I see that, in the paper you quote, a (now discredited) "tired light" hypothesis is invoked, in an attempt to explain the conversion from a stellar radiation spectrum to a microwave spectrum. The paper, I see, was published in a now defunct, crank, on-line journal called "Apeiron", to which it seems this Assis person, who is one of the authors of the paper, was a regular contributor: http://redshift.vif.com/Apeiron_Home.htm Edited February 1, 2018 by exchemist Quote Link to comment Share on other sites More sharing options...
bangstrom Posted February 1, 2018 Report Share Posted February 1, 2018 (edited) But regarding the question of "Where does the energy go?", surely if you have a pre-Big Bang model in which the universe is unbounded, then that energy can dissipate indefinitely, can't it? So there is no reason for it come "back" from anywhere, once emitted. Furthermore the radiation of these bodies does not have the observed microwave black body spectrum. I see that, in the paper you quote, a (now discredited) "tired light" hypothesis is invoked, in an attempt to explain the conversion from a stellar radiation spectrum to a microwave spectrum. In any model having an unbounded surface, the CMB radiation should be the first to go. Our universe appears to be internally curved so whatever energy that was there in the beginning should still be around in some form. It is hard to imagine that any form of early energy could remain in its primal state without having been absorbed and re-emitted by cold, non-luminous matter such as hydrogen atoms or dust particles so little radiation from the early and denser universe should maintain its original spectral signature. The energy behind the CMB is thought to have been generated by an intensely hot body of hydrogen plasma which is also the major part stellar radiation and neither radiation should have an ideal black body spectrum when first emitted but all radiations tend to flat line and become indistinguishable below about 10K so a 3K radiation may be a mixture of radiation sources and all radiations approach the ideal black body radiation at 3K. The old “tired light” theories based on Compton scatter etc. have been discredited but D. W. Sciama proposed a form of tired light theory in 1952 based on General Relativity that remains viable Edited February 1, 2018 by bangstrom Quote Link to comment Share on other sites More sharing options...
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