Order of Kilopi
I have to disagree. There are observations that strongly suggest the existence of dark matter and dark energy is a solid inference to make - but the inferred DM and DE has not been directly observed. What is the DM? What is the DE? We would know if these entities of Lamda CDM cosmology were in fact observed.Originally Posted by korjik
Keep in mind that you have proposals for alternatives to DM such as MOND. Such alternatives would not get published in the journals if the DM was observed.
Order of Kilopi
Inference: the existence of Neptune was inferred from the discrepancy between expected and observed orbits of the planets; the existence of the neutrino was an hypothesis introduced to keep the principle of conservation of energy.
Why do you never address the other points of my posts?
Bad Post-Doc
I'm sorry--how do you observe and measure without numbers?
_____________________________________________
Gillian
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Order of Kilopi
The existance of both is only because of observations. Wether we have seen them directly or not is irrelevant. no one has seen an atom, but no one doubts they exist (electron microscope images arent seeing). My point is is that neither was predicted by theory, actually both went very much against the theory of the time, but they had to be added because observation demanded it. That is something that is frequently forgotten here, that DM and DE are not artifacts of theory, but artifacts of observation, and theory had to be changes to account for them
Established Member
I beg to differ, but the math was correct for what was known at the time. Tyey did not have an understanding of how Wing shape worked, and assumed that like fan's, the air impacting the underside of the wing pushed a bird upwards.
They had no idea that the curved shape of both a birds wings presented at angel to the air caused a low pressure area (vacume) that pulled the bird upwards, more so then the air compressed under the wing pushed.
One you account for both effects the same math that disproved it, worked for proving it.
However the wing shape wasn't inspired from Math or Physics, it was copied from nature. The Math was worked out on the pressure varients later, after curved wings demonstrated flight was possible.
Order of Kilopi
The inferred existence of both is because of observations.
It certainly is relevant. If we haven't seen them they are not observed - they remain an inference. I'm not disputing that they are a scientifically well supported inference, but there are alternatives proposed - especially where DM is concerned. Its pretty difficult to propose a scientifically viable alternative to something that is in fact observed. MOND proponents would be ridiculous if we had in fact observed the DM. What we observe (as one example) is that spiral galaxy rotation curves do not drop off in a keplerian fashion but generally remain flat to the last measured point. We infer the presence of DM because of this. But others infer that gravity needs to be modified (MOND for example).Wether we have seen them directly or not is irrelevant.
There is a big difference between "no one doubts" atoms exist and "atoms have been observed". No one doubts atoms exist because our theories to explain atomic behavior in chemistry and physics are very successful at explaining what we are able to observe. The success of those models does not make atoms observed.no one has seen an atom, but no one doubts they exist (electron microscope images arent seeing).
Observation alone did not demand it. Observations interpreted in the context of current theory demanded it. DM is the interpretation of the flat rotation curves in the context of Newtonian dynamics. Modifying Newtonian dynamics in the fashion suggested by Milgrom is an alternative interpretation that does not demand DM. Thus DM is not an observation.My point is is that neither was predicted by theory, actually both went very much against the theory of the time, but they had to be added because observation demanded it.
I would disagree with that too. You have some people suggest that DM is a patch to fix theory, because - they say- observations are inconsistent with theory. So they argue DM is one way to keep current theory consistent with the observations. I don't recall anybody saying that DM started as a theory based on no observations and scientists have since been seeking observations to justify it. That makes no sense. Theories are proposed as a means of explaining what is observed. Then scientists seek to observe new phenomenon that the theory predicts which have not been previously observed.That is something that is frequently forgotten here, that DM and DE are not artifacts of theory, but artifacts of observation, and theory had to be changes to account for them
Administrator
Hmmm. I was going to close this thread because of Sani5's departure, but I see there is an interesting thoughtful discussion going on here.
One note about MoND, it can be used to explain the rotation rate in medium-sized Spiral galaxies, but doesn't work for low surface brightness galaxies, or to explain lensing in galactic clusters. So far as I know only dark matter gives a consistant explanation for all of these phenomena.
Forming opinions as we speak
Order of Kilopi
I'll have to check, but I believe you are right that lensing in clusters is a difficulty for MOND. But the situation with LSB galaxies is actually the opposite of what you said. LSB galaxies work very well for MOND and are difficult for CDM models. See de Blok & McGaugh and McGaugh & de Blok . One of the major difficulties facing CDM is the tight coupling between the observed distribution of luminous mass and the required distribution of CDM. The problem with this coupling is that it contradicts the properties expected for collisionless CDM.
There is a tremendous amount of literature detailing this observational problem for CDM and what I find curious about it is that the prevailing Lamda CDM cosmology which WMAP results are consistently argued to support is based upon a significant hypothesized component (CDM) that has properties inconsistent with the observational results on the scale of individual galaxies.
Yet this CDM problem seems to be ignored in all the Lamda CDM modeling. I don't understand that because a close look at the literature on galaxy scales clearly suggests that collisionless CDM has been falsified. The alternative DM candidates that have been proposed to deal with this problem (Warm DM, Self-interacting DM ...) have their own problems.
The answer of course is that astronomers feel CDM is sucessful on large scales and therefore are willing to assume that the small scale problems will work themselves out. But these problems were known 20 years ago and better data has not erased the problem, but solidified it.
Order of Kilopi
I have an idea where you're coming from, Korjik, but I've got to agree with dgruss that you're just overstating the case. Like practically everything in science, DM and DE are provisional explanations. If our theories of gravity are accurate, which we have every reason to believe they are, then the observed rotation speeds of galaxies are way too fast and they should be flying apart; therefore we need something to explain what keeps galaxies together. The simplest and seemingly most reasonable answer is that there must be a lot of mass spread throughout each of the galaxies that we have yet to detect -- that is, dark matter. It is inferred from what appears to be its gravitational effect. The gravitational "effect" is observed, but there is a possibility that there is some other explanation for this observation.
Well, the problem is that they are not tightly coupled. I guess that is what you're saying. Beyond the fact that galaxies don't seem to be showing enough mass to keep them together, galactic rotation curves do not behave as would be expected from the observed distribution of luminous matter, which is: lots at the center and less and less as you move away from the center. Judging from the orbits of all the stars within a galaxy, the hypothesized dark matter must be fairly uniformly spread throughout the galaxy and extend well beyond the visible edge of the luminous disk. But if dark matter is gravitationally "active", why hasn't it bunched up more in the center and thinned out at the edges like the luminous matter? Especially when nonbaryonic dark matter is being put forward as a possible explanation for structure formation in the very early universe. If it was "clumping" even before the universe cooled enough to allow hydrogen and helium to form, one would (naively?) think it would be pretty tightly packed into the centers of the galaxies by now. But the observed orbits imply it must be spread evenly throughout. This appears to be a problem.
Everyone is entitled to his own opinion, but not his own facts.
Banned
This is not just a problem for CDM, but a major problem for current thinking on all galaxy formation!
http://www.narrabri.atnf.csiro.au/pu...mages/ngc2915/
http://www.xs4all.nl/~carlkop/backyard.html
Where are the already formed stars in clusters that are supposed to merge to form galaxies?
Also, if you look at the ghost galaxy, it already has a galactic core that has spun the "Gas" into spirals with no stars in it, so that should indicate that the SMBH is much more instrumental in the galaxy rotation curves than anyone has even come close to calculating, and thats before trying to calculate how long it has been "spinning" it!
Also, I think that one of Sani's points was saying that just because the math might show that something is plausible, doesn't mean it is proven, and that there is an inherent danger in putting to much stock in the math. For example, there is a ton of math that shows mainstream that "Inflation" is possible, but if the universe did not start out with that, then of course, it is meaningless.
Order of Kilopi
I don't follow. Obviously there were hundreds of billions of regions dense enough to form "normal" galaxies. Why would it be surprising that some regions would not be quite dense enough?
Everyone is entitled to his own opinion, but not his own facts.
Banned
Quote:
Originally Posted by RussT
This is not just a problem for CDM, but a major problem for current thinking on all galaxy formation!
http://www.narrabri.atnf.csiro.au/pu...mages/ngc2915/
Where are the already formed stars in clusters that are supposed to merge to form galaxies?
Cougar, did you click on the link and look at the galaxy in question?
Order of Kilopi
Yes.
This question seems a bit confused. I'm not sure what you're asking. By the way, I believe large-scale structure formation is still one of the great unsolved problems in astrophysics.
Everyone is entitled to his own opinion, but not his own facts.
Banned
[I believe large-scale structure formation is still one of the great unsolved problems in astrophysics.]
I agree wholeheartedly, and galaxy formation is the key to solving that as well as a host of others.
What I am asking is simply this. Galaxies are 'supposed' to form thru star systems merging, right? So, where are the already formed stars merging to form this galaxy?
Order of Kilopi
This is how galaxies evolve -- for example ellipticals form from merging spirals -- but to me it looks like galaxies initially form from very early black holes, which appear to us as young quasars. There is then a long evolution of change into more normal spiral galaxies. Remember the early universe was much more dense with hydrogen and helium, and it was much more crowded.
Everyone is entitled to his own opinion, but not his own facts.
Established Member
Your examples are weak.
Math and reality are not separable. When a small child is picked on by a big bully and finally decides to return a strong blow in return, he or she has unconsciously calculated the existence of momentum and knows that more is needed than what was delivered in order to overcome and knock the bully back. We understand trigomometry when we first complete a pass in football and Michael Jordan had to understand how to adjust his center of mass in order to create "hang time" when gliding toward a basket. Math is not subordinate to physics. Math is physics. Math is observation. When we see the blue sky our eyes are making a mathematical computation. When math coordianted with tools allowed radio telescopes to "see" something our eyes cannot, did we make some conclusion that their measurements are wrong just because our eyes are "reality" from our perspective? Just as Earth was shown not to be an Aristotelian "special place" in the universe, so our eyes are no longer the final arbitrators they once were. Human chauvanism is hard to shake loose. The math of Ptolemy was very crude and is an example of "shortened" measurement.
Sani5, Maria Montessouri redesigned her elementary schools to reflect what you sense to be true. She did her thesis watching construction workers going through their apprenticeships and noticed that they were introduced to tools and material while vocabulary and math was something that was not memorized, but merely associated to the objects they held and worked with. They did not have to cram to understand what a hammer was. But they knew what a ruler was.They would not take words and try to make the world fit those words but would make words associate to their work experience.If you visit a Montessouri school, you will see the children arranged into work stations rather than sitting at desks listening to lectures. But it only goes so far.
This introduction to carpentry (and elementary schooling) led them right away to the failure waiting when continuing down such a dead end. Excess material would lie around and cause pile ups. Math was needed to straighten out those messes. Bad measurements led to things that didn't fit right and had to be redone.
The needed to make lists of material to buy and to know the meanings of the words on the lists to communicate with the lumber yard. That is why apprentices are not allowed to run the business.
If math was subordinate to our experience with tools (which were mathematically designed), then the family garages in blue collar neighborhoods would be where all the inventions would be eminating from..They aren't. A few neat motor cycles have been built in those settings (I used to tear apart and rebuild one of these)
http://www.angelfire.com/sc/BOBBYNVE...E/history.html
but when it comes to electronics you run into a wall. From garages come only a few experiments. Fermilab does one billion repititions of an experiment and doesn't claim discovery until they get mathematically predicted results in 99.999% of those one billion runs.
Math today has too many of its roots based on valid experiment whereas yesterday's math did not.The screen in front of you would not be there without relativity and quantum physics and the math associated with them. The world of objectivism has given way to the world of subjectivism.
Go rent "October Sky". Without math those rockets were failing. The more the math got involved, the more accurate the flights resulted.
Established Member
You want to say – if something is predicted by math , it is possible experimentally too.
It depends on assumption you have taken in your math.
1.Ptolomeo thought the planets orbits along a circle , because the circle is a perfect movement – bad math – he did not know a gravity.
2.Kepler thought the planets orbits along an ellipse , because the Newton gravity – bad math – he did not know General Relativity
3.Schwarzschild thought a photon can not leave a Black Hole – bad math – he did not know Hawking Radiation.
4.A present mainstream think there is a infinite dense singularity in the Black Hole centre – bad math – they do not know what is the space and what is the Quantum Gravity (developed still).
Established Member
Isn't the mainstream view more like GR breaks down at the singularity of a black hole precisely because it predicts infinite density?
Banned
Not exactly...see post # 66 and # 79 Sani5's math thread.
Banned
czeslaw, how can you keep refering to Hawking Radiation, when you don't even think black holes exist? You can't just equate eveything that is said about black holes (that you like) and then convert it to "Your" concept of what you want to happen in the vicinity of where a black hole would be.
Light (photons) cannot escape a black hole...Hawking Radiation (is theory) and is when particle pairs are created and one goes in the black hole and the other doesn't.
See the above post #'s for your answer to "Infinite Density" as far as black holes go.
Established Member
Yes. the newest mainstream says - we do not know what the singularity is and how dense it is.
Established Member
Black Hole may evaporate by Hawking Radiation.
Isn't it your idea the singularity produces a matter ?
Black Hole does not work according to General Relativity only. Let you go in the XXI century science. Quantum Mechanic and Quantum Gravity avoids such a superdense singularities.
unexpected discovery means that a black hole could behave as a good quantum computer and be used to perform useful calculations -- if only we knew how to program it (Phys. Rev. Lett. 96 061302). http://physicsweb.org/articles/news/10/3/1/1
Banned
[but to me it looks like galaxies initially form from very early black holes, which appear to us as young quasars.]
This is appears to be partially correct (Young Quasars), but how does that explain this, and the one I already linked for you (Ghost Galaxy)?
http://www.xs4all.nl/~carlkop/backyard.html
Established Member
And another nit to pick.
Kepler didn't know Newtonian laws.
He thought the planets orbit along an ellipse because that fitted
the observations the best.
He definitely wasn't expecting to find anything like that.
Later Newton based his laws in part on Kepler's Laws.
Established Member
Is inconvienent. You discuss unpleasant aspect of realityInference: the existence of Neptune was inferred from the discrepancy between expected and observed orbits of the planets; the existence of the neutrino was an hypothesis introduced to keep the principle of conservation of energy.
Why do you never address the other points of my posts?
Established Member
Of course, Newton lived after Kepler but both of them thought the Kepler's law's is a good math.
It was good for their time only.
Anyway the MATH is changed with a time. It is not an independent truth.
Order of Kilopi
I've been waiting for you to tell us what's wrong with Kepler's laws.
Established Member
A Mercury orbit around the Sun.
We need GR math to describe it precisely.
Established Member
Math is actually only a language, or tool , which we use to attempt to describe "reality". In this respect, it is essentially no different from that other language, or tool, which we call "English", without which you wouldn't have been able to make the points you have made and I wouldn't be able to respond to you.Your examples are weak.
Math and reality are not separable. When a small child is picked on by a big bully and finally decides to return a strong blow in return, he or she has unconsciously calculated the existence of momentum and knows that more is needed than what was delivered in order to overcome and knock the bully back. We understand trigomometry when we first complete a pass in football and Michael Jordan had to understand how to adjust his center of mass in order to create "hang time" when gliding toward a basket. Math is not subordinate to physics. Math is physics. Math is observation. When we see the blue sky our eyes are making a mathematical computation. When math coordianted with tools allowed radio telescopes to "see" something our eyes cannot, did we make some conclusion that their measurements are wrong just because our eyes are "reality" from our perspective? Just as Earth was shown not to be an Aristotelian "special place" in the universe, so our eyes are no longer the final arbitrators they once were. Human chauvanism is hard to shake loose. The math of Ptolemy was very crude and is an example of "shortened" measurement.
Sani5, Maria Montessouri redesigned her elementary schools to reflect what you sense to be true. She did her thesis watching construction workers going through their apprenticeships and noticed that they were introduced to tools and material while vocabulary and math was something that was not memorized, but merely associated to the objects they held and worked with. They did not have to cram to understand what a hammer was. But they knew what a ruler was.They would not take words and try to make the world fit those words but would make words associate to their work experience.If you visit a Montessouri school, you will see the children arranged into work stations rather than sitting at desks listening to lectures. But it only goes so far.
This introduction to carpentry (and elementary schooling) led them right away to the failure waiting when continuing down such a dead end. Excess material would lie around and cause pile ups. Math was needed to straighten out those messes. Bad measurements led to things that didn't fit right and had to be redone.
The needed to make lists of material to buy and to know the meanings of the words on the lists to communicate with the lumber yard. That is why apprentices are not allowed to run the business.
If math was subordinate to our experience with tools (which were mathematically designed), then the family garages in blue collar neighborhoods would be where all the inventions would be eminating from..They aren't. A few neat motor cycles have been built in those settings (I used to tear apart and rebuild one of these)
http://www.angelfire.com/sc/BOBBYNVE...E/history.html
but when it comes to electronics you run into a wall. From garages come only a few experiments. Fermilab does one billion repititions of an experiment and doesn't claim discovery until they get mathematically predicted results in 99.999% of those one billion runs.
Math today has too many of its roots based on valid experiment whereas yesterday's math did not.The screen in front of you would not be there without relativity and quantum physics and the math associated with them. The world of objectivism has given way to the world of subjectivism.
Go rent "October Sky". Without math those rockets were failing. The more the math got involved, the more accurate the flights resulted.
In any language, there are terms which some people believe to describe reality and which others don't. In what way, for example, is the word "God" (or "Gott", 'Dieu", etc. in other languages) essentially different from a term such as "cosmological constant" invented by Einstein, whose meaning or simple existence is similarly a mere matter of faith (fervently upheld by some, fiercely disputed by others)? Idem for DE and DM, of course...
The apparent objectivity of math should not lead us to believe that it actually and necessarily describes reality. Math-inspired FAIRIE DUST ("Fabricated Adhoc Inventions Repeatedly Invoked in Efforts to Defend Untenable Scientific Theories") is essentially no different from the FAIRY-TALES (e.g. "The Emperor's Clothes") we were told as kids.
Banned
Cougar...? And what about Dwarf Galaxies?
Last edited by RussT; 2006-Mar-30 at 11:31 PM.
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