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#21
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Galaxies without dark matter halos?
Phillip Helbig---remove CLOTHES to reply
wrote in message ... In article , greywolf42 writes: I think there is some confusion here. Yes, Omega (matter) is 0.3 or so. If you count galaxies, you count matter. You count apparent luminosity, not matter. And you convert that apparent luminosity to absolute luminosity based upon a theory of distance-vs-redshift. If your theory is wrong, so is your absolute luminosity. (The absolute-luminosity vs morphology relation is also based on the assumption of the big bang.) If your absolute luminosity is wrong, then so is your mass estimate (which may have other errors, as well). No. Estimating the density by measuring luminosity One cannot 'measure luminosity.' It's simply not possible without first making several assumptions. We *can* measure 'brightness' or 'apparent luminosity.' To measure 'luminosity' (which for your uses means 'absolute luminosity'), one must first determine the distance and net extinction of the source. This requires at least two theoretical models. and assuming a mass-to-light ratio (such as that of our galaxy), also known as Oort's method, takes place in the LOCAL universe. I'm not discussing multiple-universe theories. "Local" in true distance-measuring systems only extends to 300 light-years or so (after Hipparcos). Beyond that, we make theoretical assumptions. Redshift-based distances don't play much of a role here. You are incorrect. There are about a couple of dozen galaxies where we have the ability to resolve Cepheid variables -- which are our only reliable distance "standard candles" (pre-supernovae -- which is another bag of worms). All distances to other galaxies are measured by assuming the BB and Hubble constant. (The fact that one gets the same result as with more global methods is another argument in favour of the (current, but probably relatively robust) standard model.) What are the 'more global methods' to which you refer? Other observations (CMB) indicate that the universe is flat. If you start with some versions of the BB theory, yes. The CMB may have other meanings if you assume different theories. Yes, the heavens could be full of angels with flashlights emitting microwaves. The point is that CMB measurements only indicate 'flatness' for the BB. No matter how you denigrate competing theories. That implies 0.7 in lambda. OK, take these values and the value of H, independently found to be 71 from the CMB and the HST key project (which agrees well with the value from gravitational-lens time delays), and calculate the age of the universe. Using what theory? What's the point of assuming an 'age of the universe' that requires BB, if the point is to determine the BB? The point, here, was to show that all is consistent. If I have a theory in which different lines of investigation lead to the same result within that theory, without inserting this result from the start, then that is an argument in favour of that theory. True. However, there are no 'independent' lines of investigation here. If the BB theory is incorrect, then the masses used are incorrect. And the 'dark matter' amounts are incorrect. And the 'dark energy' amounts are incorrect. Historically, every one of these 'new' additions to the theory are ad hoc -- to avoid another 'problem' with the BB. It is somewhat older than the age of the oldest objects we know. What numbers do you come up with? The 10-15 billion years required by the (post Hipparcos) Hubble shift is significantly younger than the 18 billion year old globular clusters. This estimate for globular-cluster ages is obsolete. What's your reference? It is not sufficient merely to claim an observation is 'obsolete,' and then avoid my question entirely. Again, what specific numbers to you come up with for age of the universe and age of globular clusters? All is quite consistent. This "standard model" is also compatible with the m-z diagram for supernovae. Only if you assume 'dark energy' as an additional ad hoc assumption. It's not an assumption, it's an observation. "Dark Energy" may not be observed. The observation is that the Hubble constant is not linear at far distances. "Dark Energy" is the ad hoc rationale to account for the observation (the new epicycle). Suppose someone gives me a paper bag, and I don't know if it is full of air or lead. If it feels heavy, I can say that there is something inside other than air, even if I don't know what it is. Who said that it only held air or lead? 10 pounds of air is the same as 10 pounds of lead. Or a microgram of air and a microgram of lead. "Dark energy" is just a modern sexy name for the cosmological constant (with the possibility that the equation of state is perhaps different than that of a pure cosmological constant). You make it sound like ANY observed m-z diagram could be made compatible with the data. This is not true. No need to distort my position with a strawman argument. I simply note that the "amount" and 'characteristics' of "dark energy" are backfit to the observed m-z diagram. (In addition, it looks like the equation of state is that of a pure cosmological constant.) Equations of state are theoretical constructs. The observation is simply that the "Hubble constant," isn't constant. See above. They don't have to explain it. They point out that THERE IS NO REASON TO EXPECT IT TO BE FLAT. Their book is concerned mostly with measuring Omega (matter). At the time, there was no strong evidence for a cosmological constant, so they favoured a model with lambda=0, pointing out even then that lambda=0.7 also fits the data and would be a viable choice. The universe doesn't have to be flat, but it CAN be flat, or close to it, as current observations seem to indicate. I thought that GUTs require omega = 1.0. Are they all wasting their time? Are you taking it as an established fact that GUTs are true---in contrast to the big bang? Give me some evidence that I should believe that a GUT---in particular, one requiring omega = 1.0---is true. Another strawman argument. No, I'm not assuming GUTs are true. But they are popular. Frankly, since the all predicted the decay of the proton -- and protons have not been seen to decay -- I conclude that GUTs are false. (Someday I may be proved wrong. But after three major theoretical 'revisions' to get out from under observation, I'm not holding my breath.) And why did the 'big bang' efforts of 20 years ago all focus on the necessity of 'flatness.' Because it was perceived to be a problem. That's why Coles and Ellis wrote their book, to set the record straight. Excellent. Another physics myth torpedoed. We all agree that Omega (matter) is 0.3. BUT WE DON'T KNOW WHAT MOS OF THIS MATTER IS. Then there's little basis for the agreement, don't you think? No. If the lights go out, we all agree that it is dark, though we might not know the cause, and our best guesses might disagree. Then there's little basis for the agreement as to the cause of the blackout. All we know is that there is something wrong. Most astronomers agree that lambda is 0.7. What lambda "IS" is a separate question. It's not seperate at all. If you don't know what it 'IS', then you can't know what the measurement of that unknown is. Rubbish. If I weigh a container, I know its weight, even if I don't know what is inside. If you don't agree on the theory used to 'weigh' the container, you don't even know that much. See any of a number of papers on "cosmic concordance". I meant the observations to which *you* were referring. I don't insist on a complete list. Just a few examples. Those ARE the observations to which I am referring. *What* are the observations to which you are referring, specifically? It's kind of like the measurement of Avagadro's number a hundred years ago; more than any one observation, this proof that atoms are real came mostly from several independent methods giving the same result. Actually, atomic theory was fought tooth-and-nail by the positivists. And they lost. And yet "modern physicists" continued to apply the positivistic method. Equations are all. That depends on which 'Big Bang' theory you refer to when you say "THE" big-bang theory. "THE" (most popular) BB theory contains inflation. Which makes statements of the values of omega and lambda. At most, it would claim that the sum is 1. However, even if it is ruled out, the evidence for the big bang still stands. To which specific 'Big Bang' theory(ies) are you referring? So Coles and Ellis do not share the commonly-accepted view that there really *was* a 'flatness problem.' However, everyone understands what the 'classical flatness problem' *was.* Even if Coles and Ellis believe that this 'problem' was more 'myth' than 'problem.' It is no longer "commonly accepted" except among those who have not followed the progress of science in this field. But you still understand what the perceived problem was. Hence, there is no need to imply that there never was a perception of the problem. And no need to denigrate others for addressing the 'problem.' greywolf42 ubi dubium ibi libertas |
#22
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Galaxies without dark matter halos?
In article , greywolf42
writes: One cannot 'measure luminosity.' It's simply not possible without first making several assumptions. We *can* measure 'brightness' or 'apparent luminosity.' To measure 'luminosity' (which for your uses means 'absolute luminosity'), one must first determine the distance and net extinction of the source. This requires at least two theoretical models. OK, we count photons at the lowest level (or measure a current proportional to the number of photons---or measure a voltage which, given a resistance is related to the current: whatever). What assumptions do you think are wrong? Sure, any measurement is a long chain from the actual measurement to the quantity of interest, but that in itself is not a criticism. Russell and Whitehead once wrote a book on mathematics where they tried to justify everything explicitly. It took them a large number of pages before they got to 1 + 1 = 2. Useful, perhaps, for the philosophy of mathematics, but not for buying potatoes at the market. (The fact that one gets the same result as with more global methods is another argument in favour of the (current, but probably relatively robust) standard model.) What are the 'more global methods' to which you refer? For H_0: the HST key project is relatively local, gravitational-lens time delays are more global, and the CMB is very global. The point is that CMB measurements only indicate 'flatness' for the BB. No matter how you denigrate competing theories. Show me another theory with adjustable parameters which, when these parameters are varied within some pre-CMB-knowledge ranges, is compatible with the CMB data for only some combinations of parameters. If the CMB is compatible with none, it's ruled out by the CMB. If it is compatible with the whole range of parameters, it's not (yet) testable. This estimate for globular-cluster ages is obsolete. What's your reference? It is not sufficient merely to claim an observation is 'obsolete,' and then avoid my question entirely. You made the claim first. Give me a reference and I'll give you a newer, better reference showing it to be wrong. "Dark Energy" may not be observed. The observation is that the Hubble constant is not linear at far distances. "Dark Energy" is the ad hoc rationale to account for the observation (the new epicycle). The point is that the non-linearity is NOT completely arbitrary, but is easily explained by an idea which has been around for decades. Equations of state are theoretical constructs. The observation is simply that the "Hubble constant," isn't constant. You are displaying extreme lack of knowledge here. The term "constant" in "Hubble constant" means that, at a given time, it is constant everywhere in the universe. Another strawman argument. No, I'm not assuming GUTs are true. But they are popular. Creationism is popular in much of the U.S. And your point is? Excellent. Another physics myth torpedoed. True science is self-correcting. But you still understand what the perceived problem was. Hence, there is no need to imply that there never was a perception of the problem. And no need to denigrate others for addressing the 'problem.' Only if the problem has long since been solved. Galileo was wrong about the tides, but there is no point in coming up with some theory other than the differential attraction of the moon to explain his fault. |
#23
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Galaxies without dark matter halos?
In article , greywolf42
writes: One cannot 'measure luminosity.' It's simply not possible without first making several assumptions. We *can* measure 'brightness' or 'apparent luminosity.' To measure 'luminosity' (which for your uses means 'absolute luminosity'), one must first determine the distance and net extinction of the source. This requires at least two theoretical models. OK, we count photons at the lowest level (or measure a current proportional to the number of photons---or measure a voltage which, given a resistance is related to the current: whatever). What assumptions do you think are wrong? Sure, any measurement is a long chain from the actual measurement to the quantity of interest, but that in itself is not a criticism. Russell and Whitehead once wrote a book on mathematics where they tried to justify everything explicitly. It took them a large number of pages before they got to 1 + 1 = 2. Useful, perhaps, for the philosophy of mathematics, but not for buying potatoes at the market. (The fact that one gets the same result as with more global methods is another argument in favour of the (current, but probably relatively robust) standard model.) What are the 'more global methods' to which you refer? For H_0: the HST key project is relatively local, gravitational-lens time delays are more global, and the CMB is very global. The point is that CMB measurements only indicate 'flatness' for the BB. No matter how you denigrate competing theories. Show me another theory with adjustable parameters which, when these parameters are varied within some pre-CMB-knowledge ranges, is compatible with the CMB data for only some combinations of parameters. If the CMB is compatible with none, it's ruled out by the CMB. If it is compatible with the whole range of parameters, it's not (yet) testable. This estimate for globular-cluster ages is obsolete. What's your reference? It is not sufficient merely to claim an observation is 'obsolete,' and then avoid my question entirely. You made the claim first. Give me a reference and I'll give you a newer, better reference showing it to be wrong. "Dark Energy" may not be observed. The observation is that the Hubble constant is not linear at far distances. "Dark Energy" is the ad hoc rationale to account for the observation (the new epicycle). The point is that the non-linearity is NOT completely arbitrary, but is easily explained by an idea which has been around for decades. Equations of state are theoretical constructs. The observation is simply that the "Hubble constant," isn't constant. You are displaying extreme lack of knowledge here. The term "constant" in "Hubble constant" means that, at a given time, it is constant everywhere in the universe. Another strawman argument. No, I'm not assuming GUTs are true. But they are popular. Creationism is popular in much of the U.S. And your point is? Excellent. Another physics myth torpedoed. True science is self-correcting. But you still understand what the perceived problem was. Hence, there is no need to imply that there never was a perception of the problem. And no need to denigrate others for addressing the 'problem.' Only if the problem has long since been solved. Galileo was wrong about the tides, but there is no point in coming up with some theory other than the differential attraction of the moon to explain his fault. |
#24
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Galaxies without dark matter halos?
Phillip Helbig---remove CLOTHES to reply
wrote in message ... In article , greywolf42 writes: I thought that GUTs require omega = 1.0. Are they all wasting their time? No GUT ever required Omega_matter = 1 in any meaningful sense. (As I said before, at most one could argue that inflation---which might be the consequence of some GUT---could point to Omega_matter + lambda = 1.) What used to happen is that the GUT guys would come up with their particle du jour and suggest it as a dark matter candidate, suggesting that its predicted mass would be about right to explain the "missing mass", or even make Omega_matter = 1. (Of course, my feeling is that they looked up the answer in the back of the book to get the numbers to come out right.) This is brilliantly described he http://www.astro.umd.edu/~ssm/mond/flowchart.html Ten years ago, I was as critical of the confidence of many cosmologists in the then standard model as greywolf is at present. I'm not critical as a matter of course, but only when I think something is wrong. My own view is that, in the last 10 years, driven primarily by data but also by arguments such as those of Coles and Ellis, the amount of dogma has decreased and, partly as a result, the current standard model looks quite promising. Again, the difference is that today's standard model is driven primarily by data, while 10 years ago the then standard model was driven primarily by theoretical prejudice. Well, we have something in common, then. However, what I have seen is not an increase in data supporting the 'theoretical prejudice,' but in theoretical prejudice 'creating' and 'correcting' data to match the theoretical prejudice. I consider the probability minimal that the dogma 'just happened to be correct.' greywolf42 ubi dubium ibi libertas |
#25
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Galaxies without dark matter halos?
Phillip Helbig---remove CLOTHES to reply
wrote in message ... In article , greywolf42 writes: I thought that GUTs require omega = 1.0. Are they all wasting their time? No GUT ever required Omega_matter = 1 in any meaningful sense. (As I said before, at most one could argue that inflation---which might be the consequence of some GUT---could point to Omega_matter + lambda = 1.) What used to happen is that the GUT guys would come up with their particle du jour and suggest it as a dark matter candidate, suggesting that its predicted mass would be about right to explain the "missing mass", or even make Omega_matter = 1. (Of course, my feeling is that they looked up the answer in the back of the book to get the numbers to come out right.) This is brilliantly described he http://www.astro.umd.edu/~ssm/mond/flowchart.html Ten years ago, I was as critical of the confidence of many cosmologists in the then standard model as greywolf is at present. I'm not critical as a matter of course, but only when I think something is wrong. My own view is that, in the last 10 years, driven primarily by data but also by arguments such as those of Coles and Ellis, the amount of dogma has decreased and, partly as a result, the current standard model looks quite promising. Again, the difference is that today's standard model is driven primarily by data, while 10 years ago the then standard model was driven primarily by theoretical prejudice. Well, we have something in common, then. However, what I have seen is not an increase in data supporting the 'theoretical prejudice,' but in theoretical prejudice 'creating' and 'correcting' data to match the theoretical prejudice. I consider the probability minimal that the dogma 'just happened to be correct.' greywolf42 ubi dubium ibi libertas |
#26
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Galaxies without dark matter halos?
Phillip Helbig---remove CLOTHES to reply
wrote in message ... In article , greywolf42 writes: {replacing an 'invisible' snip, because of a later statement} ============================ [Phillip] I think there is some confusion here. Yes, Omega (matter) is 0.3 or so. If you count galaxies, you count matter. [greywolf42] You count apparent luminosity, not matter. And you convert that apparent luminosity to absolute luminosity based upon a theory of distance-vs-redshift. If your theory is wrong, so is your absolute luminosity. (The absolute-luminosity vs morphology relation is also based on the assumption of the big bang.) If your absolute luminosity is wrong, then so is your mass estimate (which may have other errors, as well). [Phillip] No. Estimating the density by measuring luminosity ============================ One cannot 'measure luminosity.' It's simply not possible without first making several assumptions. We *can* measure 'brightness' or 'apparent luminosity.' To measure 'luminosity' (which for your uses means 'absolute luminosity'), one must first determine the distance and net extinction of the source. This requires at least two theoretical models. {replacing another 'invisible' snip} =================================== and assuming a mass-to-light ratio (such as that of our galaxy), also known as Oort's method, takes place in the LOCAL universe. I'm not discussing multiple-universe theories. "Local" in true distance-measuring systems only extends to 300 light-years or so (after Hipparcos). Beyond that, we make theoretical assumptions. Redshift-based distances don't play much of a role here. You are incorrect. There are about a couple of dozen galaxies where we have the ability to resolve Cepheid variables -- which are our only reliable distance "standard candles" (pre-supernovae -- which is another bag of worms). All distances to other galaxies are measured by assuming the BB and Hubble constant. =================================== OK, we count photons at the lowest level (or measure a current proportional to the number of photons---or measure a voltage which, given a resistance is related to the current: whatever). OK, I believe we have corrected your misunderstanding (or sloppy terminology) about the difference between brightness (or apparent luminosity) and absolute luminosity. What assumptions do you think are wrong? The ones contained in the portions of my post that you snipped. So, I've replaced them. Sure, any measurement is a long chain from the actual measurement to the quantity of interest, but that in itself is not a criticism. It is if you use a chain of assumptions that contain one theory, then attempt to use the results of the chain to 'disprove' a different theory. Russell and Whitehead once wrote a book on mathematics where they tried to justify everything explicitly. It took them a large number of pages before they got to 1 + 1 = 2. Useful, perhaps, for the philosophy of mathematics, but not for buying potatoes at the market. What's with the strawman argument? The point is simply the assumptions and theories that are contained in the distance 'measurements' that you are using. (The fact that one gets the same result as with more global methods is another argument in favour of the (current, but probably relatively robust) standard model.) What are the 'more global methods' to which you refer? For H_0: the HST key project is relatively local, gravitational-lens time delays are more global, and the CMB is very global. Again, what are the 'more global *methods*' to which you refer? {another 'invisible' snip replaced} ================================= Other observations (CMB) indicate that the universe is flat. If you start with some versions of the BB theory, yes. The CMB may have other meanings if you assume different theories. Yes, the heavens could be full of angels with flashlights emitting microwaves. ================================= The point is that CMB measurements only indicate 'flatness' for the BB. No matter how you denigrate competing theories. Show me another theory with adjustable parameters which, when these parameters are varied within some pre-CMB-knowledge ranges, is compatible with the CMB data for only some combinations of parameters. If the CMB is compatible with none, it's ruled out by the CMB. If it is compatible with the whole range of parameters, it's not (yet) testable. It's not necessary to match your long list of limitations. It is quite obvious that if the BB requires the CMB to indicate 'flatness', this does not affect what the CMB means to other theories. {the final portion of another 'invisible' snip replaced} ================================= The point, here, was to show that all is consistent. If I have a theory in which different lines of investigation lead to the same result within that theory, without inserting this result from the start, then that is an argument in favour of that theory. True. However, there are no 'independent' lines of investigation here. If the BB theory is incorrect, then the masses used are incorrect. And the 'dark matter' amounts are incorrect. And the 'dark energy' amounts are incorrect. Historically, every one of these 'new' additions to the theory are ad hoc -- to avoid another 'problem' with the BB. ================================= {another 'invisible' snip replaced} ================================= It is somewhat older than the age of the oldest objects we know. What numbers do you come up with? The 10-15 billion years required by the (post Hipparcos) Hubble shift is significantly younger than the 18 billion year old globular clusters. ================================= This estimate for globular-cluster ages is obsolete. What's your reference? It is not sufficient merely to claim an observation is 'obsolete,' and then avoid my question entirely. {another 'invisible' snip replaced} ============================== Again, what specific numbers to you come up with for age of the universe and age of globular clusters? ============================== You made the claim first. Give me a reference and I'll give you a newer, better reference showing it to be wrong. Um, no. *You* began with the statement (which you snipped, above) "It is somewhat older than the age of the oldest objects we know." So, please back up your statement. Then I'll be happy to find a competing reference for you. {another 'invisible' snip replaced} =============================== All is quite consistent. This "standard model" is also compatible with the m-z diagram for supernovae. Only if you assume 'dark energy' as an additional ad hoc assumption. It's not an assumption, it's an observation. =============================== "Dark Energy" may not be observed. The observation is that the Hubble constant is not linear at far distances. "Dark Energy" is the ad hoc rationale to account for the observation (the new epicycle). The point is that the non-linearity is NOT completely arbitrary, but is easily explained by an idea which has been around for decades. 'Dark energy' has not been around for decades. It was not even floated until the observations of supernovae disproved the linear Hubble assumption. The m-z diagram for supernovae could as easily be explained by the modified QM theory of JP Vigier. Which really *has* been around for decades. The m-z curve is in fact a curve of the type predicted by Vigier's theory. So Vigier's theory covers the Hubble shift in it's entirety. It's still 'ad hoc', but it's only one ad hoc. The BB theorists have had to create yet another new ad hoc form of physics to 'explain' the new observations: 'dark energy' (wich has negative gravitation, unlike any other prior form of energy or matter) . {another 'invisible' snip replaced} ================================ Suppose someone gives me a paper bag, and I don't know if it is full of air or lead. If it feels heavy, I can say that there is something inside other than air, even if I don't know what it is. Who said that it only held air or lead? 10 pounds of air is the same as 10 pounds of lead. Or a microgram of air and a microgram of lead. "Dark energy" is just a modern sexy name for the cosmological constant (with the possibility that the equation of state is perhaps different than that of a pure cosmological constant). You make it sound like ANY observed m-z diagram could be made compatible with the data. This is not true. No need to distort my position with a strawman argument. I simply note that the "amount" and 'characteristics' of "dark energy" are backfit to the observed m-z diagram. (In addition, it looks like the equation of state is that of a pure cosmological constant.) ================================ Equations of state are theoretical constructs. The observation is simply that the "Hubble constant," isn't constant. You are displaying extreme lack of knowledge here. The term "constant" in "Hubble constant" means that, at a given time, it is constant everywhere in the universe. The Hubble constant was defined in the 1920's to mean the relation between the distance of a galaxy (containing a resolvable Cepheid variable) and the redshift of the light from the galaxy. There is -- and was -- no additional theoretical baggage about being constant 'at a given time'. {another 'invisible' snip replaced} =============================== See above. They don't have to explain it. They point out that THERE IS NO REASON TO EXPECT IT TO BE FLAT. Their book is concerned mostly with measuring Omega (matter). At the time, there was no strong evidence for a cosmological constant, so they favoured a model with lambda=0, pointing out even then that lambda=0.7 also fits the data and would be a viable choice. The universe doesn't have to be flat, but it CAN be flat, or close to it, as current observations seem to indicate. I thought that GUTs require omega = 1.0. Are they all wasting their time? Are you taking it as an established fact that GUTs are true---in contrast to the big bang? Give me some evidence that I should believe that a GUT---in particular, one requiring omega = 1.0---is true. =============================== Another strawman argument. No, I'm not assuming GUTs are true. But they are popular. Creationism is popular in much of the U.S. And your point is? My point is contained in the rest of the paragraph that you 'invisibly' snipped: {another 'invisible' snip replaced} =============================== Frankly, since the all predicted the decay of the proton -- and protons have not been seen to decay -- I conclude that GUTs are false. (Someday I may be proved wrong. But after three major theoretical 'revisions' to get out from under observation, I'm not holding my breath.) And why did the 'big bang' efforts of 20 years ago all focus on the necessity of 'flatness.' Because it was perceived to be a problem. That's why Coles and Ellis wrote their book, to set the record straight. =============================== Excellent. Another physics myth torpedoed. True science is self-correcting. It's too bad we don't have more 'true science.' {another 'invisible' snip replaced} =============================== We all agree that Omega (matter) is 0.3. BUT WE DON'T KNOW WHAT MOS OF THIS MATTER IS. Then there's little basis for the agreement, don't you think? No. If the lights go out, we all agree that it is dark, though we might not know the cause, and our best guesses might disagree. Then there's little basis for the agreement as to the cause of the blackout. All we know is that there is something wrong. Most astronomers agree that lambda is 0.7. What lambda "IS" is a separate question. It's not seperate at all. If you don't know what it 'IS', then you can't know what the measurement of that unknown is. Rubbish. If I weigh a container, I know its weight, even if I don't know what is inside. If you don't agree on the theory used to 'weigh' the container, you don't even know that much. See any of a number of papers on "cosmic concordance". I meant the observations to which *you* were referring. I don't insist on a complete list. Just a few examples. Those ARE the observations to which I am referring. *What* are the observations to which you are referring, specifically? [Again, *what* are the observations to which you are referring?] It's kind of like the measurement of Avagadro's number a hundred years ago; more than any one observation, this proof that atoms are real came mostly from several independent methods giving the same result. Actually, atomic theory was fought tooth-and-nail by the positivists. And they lost. And yet "modern physicists" continued to apply the positivistic method. Equations are all. That depends on which 'Big Bang' theory you refer to when you say "THE" big-bang theory. "THE" (most popular) BB theory contains inflation. Which makes statements of the values of omega and lambda. At most, it would claim that the sum is 1. However, even if it is ruled out, the evidence for the big bang still stands. To which specific 'Big Bang' theory(ies) are you referring? So Coles and Ellis do not share the commonly-accepted view that there really *was* a 'flatness problem.' However, everyone understands what the 'classical flatness problem' *was.* Even if Coles and Ellis believe that this 'problem' was more 'myth' than 'problem.' It is no longer "commonly accepted" except among those who have not followed the progress of science in this field. =============================== But you still understand what the perceived problem was. Hence, there is no need to imply that there never was a perception of the problem. And no need to denigrate others for addressing the 'problem.' Only if the problem has long since been solved. A series of 1997 "lecture notes" does not constitute "long since solved!" Even if it is published in a book by Cambridge University Press. Galileo was wrong about the tides, but there is no point in coming up with some theory other than the differential attraction of the moon to explain his fault. Another strawman argument. greywolf42 ubi dubium ibi libertas |
#27
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Galaxies without dark matter halos?
Phillip Helbig---remove CLOTHES to reply
wrote in message ... In article , greywolf42 writes: {replacing an 'invisible' snip, because of a later statement} ============================ [Phillip] I think there is some confusion here. Yes, Omega (matter) is 0.3 or so. If you count galaxies, you count matter. [greywolf42] You count apparent luminosity, not matter. And you convert that apparent luminosity to absolute luminosity based upon a theory of distance-vs-redshift. If your theory is wrong, so is your absolute luminosity. (The absolute-luminosity vs morphology relation is also based on the assumption of the big bang.) If your absolute luminosity is wrong, then so is your mass estimate (which may have other errors, as well). [Phillip] No. Estimating the density by measuring luminosity ============================ One cannot 'measure luminosity.' It's simply not possible without first making several assumptions. We *can* measure 'brightness' or 'apparent luminosity.' To measure 'luminosity' (which for your uses means 'absolute luminosity'), one must first determine the distance and net extinction of the source. This requires at least two theoretical models. {replacing another 'invisible' snip} =================================== and assuming a mass-to-light ratio (such as that of our galaxy), also known as Oort's method, takes place in the LOCAL universe. I'm not discussing multiple-universe theories. "Local" in true distance-measuring systems only extends to 300 light-years or so (after Hipparcos). Beyond that, we make theoretical assumptions. Redshift-based distances don't play much of a role here. You are incorrect. There are about a couple of dozen galaxies where we have the ability to resolve Cepheid variables -- which are our only reliable distance "standard candles" (pre-supernovae -- which is another bag of worms). All distances to other galaxies are measured by assuming the BB and Hubble constant. =================================== OK, we count photons at the lowest level (or measure a current proportional to the number of photons---or measure a voltage which, given a resistance is related to the current: whatever). OK, I believe we have corrected your misunderstanding (or sloppy terminology) about the difference between brightness (or apparent luminosity) and absolute luminosity. What assumptions do you think are wrong? The ones contained in the portions of my post that you snipped. So, I've replaced them. Sure, any measurement is a long chain from the actual measurement to the quantity of interest, but that in itself is not a criticism. It is if you use a chain of assumptions that contain one theory, then attempt to use the results of the chain to 'disprove' a different theory. Russell and Whitehead once wrote a book on mathematics where they tried to justify everything explicitly. It took them a large number of pages before they got to 1 + 1 = 2. Useful, perhaps, for the philosophy of mathematics, but not for buying potatoes at the market. What's with the strawman argument? The point is simply the assumptions and theories that are contained in the distance 'measurements' that you are using. (The fact that one gets the same result as with more global methods is another argument in favour of the (current, but probably relatively robust) standard model.) What are the 'more global methods' to which you refer? For H_0: the HST key project is relatively local, gravitational-lens time delays are more global, and the CMB is very global. Again, what are the 'more global *methods*' to which you refer? {another 'invisible' snip replaced} ================================= Other observations (CMB) indicate that the universe is flat. If you start with some versions of the BB theory, yes. The CMB may have other meanings if you assume different theories. Yes, the heavens could be full of angels with flashlights emitting microwaves. ================================= The point is that CMB measurements only indicate 'flatness' for the BB. No matter how you denigrate competing theories. Show me another theory with adjustable parameters which, when these parameters are varied within some pre-CMB-knowledge ranges, is compatible with the CMB data for only some combinations of parameters. If the CMB is compatible with none, it's ruled out by the CMB. If it is compatible with the whole range of parameters, it's not (yet) testable. It's not necessary to match your long list of limitations. It is quite obvious that if the BB requires the CMB to indicate 'flatness', this does not affect what the CMB means to other theories. {the final portion of another 'invisible' snip replaced} ================================= The point, here, was to show that all is consistent. If I have a theory in which different lines of investigation lead to the same result within that theory, without inserting this result from the start, then that is an argument in favour of that theory. True. However, there are no 'independent' lines of investigation here. If the BB theory is incorrect, then the masses used are incorrect. And the 'dark matter' amounts are incorrect. And the 'dark energy' amounts are incorrect. Historically, every one of these 'new' additions to the theory are ad hoc -- to avoid another 'problem' with the BB. ================================= {another 'invisible' snip replaced} ================================= It is somewhat older than the age of the oldest objects we know. What numbers do you come up with? The 10-15 billion years required by the (post Hipparcos) Hubble shift is significantly younger than the 18 billion year old globular clusters. ================================= This estimate for globular-cluster ages is obsolete. What's your reference? It is not sufficient merely to claim an observation is 'obsolete,' and then avoid my question entirely. {another 'invisible' snip replaced} ============================== Again, what specific numbers to you come up with for age of the universe and age of globular clusters? ============================== You made the claim first. Give me a reference and I'll give you a newer, better reference showing it to be wrong. Um, no. *You* began with the statement (which you snipped, above) "It is somewhat older than the age of the oldest objects we know." So, please back up your statement. Then I'll be happy to find a competing reference for you. {another 'invisible' snip replaced} =============================== All is quite consistent. This "standard model" is also compatible with the m-z diagram for supernovae. Only if you assume 'dark energy' as an additional ad hoc assumption. It's not an assumption, it's an observation. =============================== "Dark Energy" may not be observed. The observation is that the Hubble constant is not linear at far distances. "Dark Energy" is the ad hoc rationale to account for the observation (the new epicycle). The point is that the non-linearity is NOT completely arbitrary, but is easily explained by an idea which has been around for decades. 'Dark energy' has not been around for decades. It was not even floated until the observations of supernovae disproved the linear Hubble assumption. The m-z diagram for supernovae could as easily be explained by the modified QM theory of JP Vigier. Which really *has* been around for decades. The m-z curve is in fact a curve of the type predicted by Vigier's theory. So Vigier's theory covers the Hubble shift in it's entirety. It's still 'ad hoc', but it's only one ad hoc. The BB theorists have had to create yet another new ad hoc form of physics to 'explain' the new observations: 'dark energy' (wich has negative gravitation, unlike any other prior form of energy or matter) . {another 'invisible' snip replaced} ================================ Suppose someone gives me a paper bag, and I don't know if it is full of air or lead. If it feels heavy, I can say that there is something inside other than air, even if I don't know what it is. Who said that it only held air or lead? 10 pounds of air is the same as 10 pounds of lead. Or a microgram of air and a microgram of lead. "Dark energy" is just a modern sexy name for the cosmological constant (with the possibility that the equation of state is perhaps different than that of a pure cosmological constant). You make it sound like ANY observed m-z diagram could be made compatible with the data. This is not true. No need to distort my position with a strawman argument. I simply note that the "amount" and 'characteristics' of "dark energy" are backfit to the observed m-z diagram. (In addition, it looks like the equation of state is that of a pure cosmological constant.) ================================ Equations of state are theoretical constructs. The observation is simply that the "Hubble constant," isn't constant. You are displaying extreme lack of knowledge here. The term "constant" in "Hubble constant" means that, at a given time, it is constant everywhere in the universe. The Hubble constant was defined in the 1920's to mean the relation between the distance of a galaxy (containing a resolvable Cepheid variable) and the redshift of the light from the galaxy. There is -- and was -- no additional theoretical baggage about being constant 'at a given time'. {another 'invisible' snip replaced} =============================== See above. They don't have to explain it. They point out that THERE IS NO REASON TO EXPECT IT TO BE FLAT. Their book is concerned mostly with measuring Omega (matter). At the time, there was no strong evidence for a cosmological constant, so they favoured a model with lambda=0, pointing out even then that lambda=0.7 also fits the data and would be a viable choice. The universe doesn't have to be flat, but it CAN be flat, or close to it, as current observations seem to indicate. I thought that GUTs require omega = 1.0. Are they all wasting their time? Are you taking it as an established fact that GUTs are true---in contrast to the big bang? Give me some evidence that I should believe that a GUT---in particular, one requiring omega = 1.0---is true. =============================== Another strawman argument. No, I'm not assuming GUTs are true. But they are popular. Creationism is popular in much of the U.S. And your point is? My point is contained in the rest of the paragraph that you 'invisibly' snipped: {another 'invisible' snip replaced} =============================== Frankly, since the all predicted the decay of the proton -- and protons have not been seen to decay -- I conclude that GUTs are false. (Someday I may be proved wrong. But after three major theoretical 'revisions' to get out from under observation, I'm not holding my breath.) And why did the 'big bang' efforts of 20 years ago all focus on the necessity of 'flatness.' Because it was perceived to be a problem. That's why Coles and Ellis wrote their book, to set the record straight. =============================== Excellent. Another physics myth torpedoed. True science is self-correcting. It's too bad we don't have more 'true science.' {another 'invisible' snip replaced} =============================== We all agree that Omega (matter) is 0.3. BUT WE DON'T KNOW WHAT MOS OF THIS MATTER IS. Then there's little basis for the agreement, don't you think? No. If the lights go out, we all agree that it is dark, though we might not know the cause, and our best guesses might disagree. Then there's little basis for the agreement as to the cause of the blackout. All we know is that there is something wrong. Most astronomers agree that lambda is 0.7. What lambda "IS" is a separate question. It's not seperate at all. If you don't know what it 'IS', then you can't know what the measurement of that unknown is. Rubbish. If I weigh a container, I know its weight, even if I don't know what is inside. If you don't agree on the theory used to 'weigh' the container, you don't even know that much. See any of a number of papers on "cosmic concordance". I meant the observations to which *you* were referring. I don't insist on a complete list. Just a few examples. Those ARE the observations to which I am referring. *What* are the observations to which you are referring, specifically? [Again, *what* are the observations to which you are referring?] It's kind of like the measurement of Avagadro's number a hundred years ago; more than any one observation, this proof that atoms are real came mostly from several independent methods giving the same result. Actually, atomic theory was fought tooth-and-nail by the positivists. And they lost. And yet "modern physicists" continued to apply the positivistic method. Equations are all. That depends on which 'Big Bang' theory you refer to when you say "THE" big-bang theory. "THE" (most popular) BB theory contains inflation. Which makes statements of the values of omega and lambda. At most, it would claim that the sum is 1. However, even if it is ruled out, the evidence for the big bang still stands. To which specific 'Big Bang' theory(ies) are you referring? So Coles and Ellis do not share the commonly-accepted view that there really *was* a 'flatness problem.' However, everyone understands what the 'classical flatness problem' *was.* Even if Coles and Ellis believe that this 'problem' was more 'myth' than 'problem.' It is no longer "commonly accepted" except among those who have not followed the progress of science in this field. =============================== But you still understand what the perceived problem was. Hence, there is no need to imply that there never was a perception of the problem. And no need to denigrate others for addressing the 'problem.' Only if the problem has long since been solved. A series of 1997 "lecture notes" does not constitute "long since solved!" Even if it is published in a book by Cambridge University Press. Galileo was wrong about the tides, but there is no point in coming up with some theory other than the differential attraction of the moon to explain his fault. Another strawman argument. greywolf42 ubi dubium ibi libertas |
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Galaxies without dark matter halos?
On Mon, 15 Sep 2003, greywolf42 wrote:
You are incorrect. There are about a couple of dozen galaxies where we have the ability to resolve Cepheid variables -- which are our only reliable distance "standard candles" (pre-supernovae -- which is another bag of worms). All distances to other galaxies are measured by assuming the BB and Hubble constant. -This- -is- -just- -flat- -wrong-. Measurements to 'all'' other galaxies are -not- made using the Hubble constant. Several other methods are used. One of the more common types involves measuring rotation curves for local galaxies with cepheid & RR-lyre distances, say by measureing the width of the 21cm line and obtaining a relationship with luminousity (Large galaxies tend to have more stars - they're brighter + they're heavier so things tend to orbit faster. And yes, they do pay attention to the type of galaxy.). This relationship is compared with that of a distant galaxy to get an estimate of the absolute luniousity which is compared with the appearant luninousity to get a distane. (See Tully-Fischer, Faber-Jackson, cosmological distance ladder). It is sooooooo easy to find out about these other measurements that to not know about them borders on willfull. I mean, box 14.2 in shu*: Local distance indicators Classical Cepheids Novae RR Lyae W Virginis Intermediate distance indicators Brightest nonvariable stars of a galaxy Brightness of globular clusters Diameters of giant HII complexes Global distance indicaters Fischer-Tully relation Brightness of Sc I galaxies Supernovae Three brightest galaxies of a cluseter Diameters of bright galaxies Baldwin relation for QSOs The list is dated but it does seem to indicate that other methods are used. Support your ideas, ok, but don't shovel up a load of dingo's kidneys. 3ch *Frank Shu _The Physical Universe_. A nice intro book & reference. |
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Galaxies without dark matter halos?
On Mon, 15 Sep 2003, greywolf42 wrote:
You are incorrect. There are about a couple of dozen galaxies where we have the ability to resolve Cepheid variables -- which are our only reliable distance "standard candles" (pre-supernovae -- which is another bag of worms). All distances to other galaxies are measured by assuming the BB and Hubble constant. -This- -is- -just- -flat- -wrong-. Measurements to 'all'' other galaxies are -not- made using the Hubble constant. Several other methods are used. One of the more common types involves measuring rotation curves for local galaxies with cepheid & RR-lyre distances, say by measureing the width of the 21cm line and obtaining a relationship with luminousity (Large galaxies tend to have more stars - they're brighter + they're heavier so things tend to orbit faster. And yes, they do pay attention to the type of galaxy.). This relationship is compared with that of a distant galaxy to get an estimate of the absolute luniousity which is compared with the appearant luninousity to get a distane. (See Tully-Fischer, Faber-Jackson, cosmological distance ladder). It is sooooooo easy to find out about these other measurements that to not know about them borders on willfull. I mean, box 14.2 in shu*: Local distance indicators Classical Cepheids Novae RR Lyae W Virginis Intermediate distance indicators Brightest nonvariable stars of a galaxy Brightness of globular clusters Diameters of giant HII complexes Global distance indicaters Fischer-Tully relation Brightness of Sc I galaxies Supernovae Three brightest galaxies of a cluseter Diameters of bright galaxies Baldwin relation for QSOs The list is dated but it does seem to indicate that other methods are used. Support your ideas, ok, but don't shovel up a load of dingo's kidneys. 3ch *Frank Shu _The Physical Universe_. A nice intro book & reference. |
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Galaxies without dark matter halos?
"g" == greywolf42 writes:
g There are about a couple of dozen galaxies where we have the g ability to resolve Cepheid variables -- which are our only reliable g distance "standard candles" (...). All distances to other galaxies g are measured by assuming the BB and Hubble constant. I feel obliged to point out that the distance to the galaxy NGC 4258 has been determined by triangulation (i.e., parallax) of the water masers in its core. There are of course assumptions in this method as well, e.g., what is the lifetime of the maser spots and are the same spots being measured from epoch to epoch. Nonetheless, if one makes reasonable assumptions, one ends up with a distance of something like 7 Mpc. -- Lt. Lazio, HTML police | e-mail: No means no, stop rape. | http://patriot.net/%7Ejlazio/ sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html |
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