If you look at a population of stars and see lots of blue or UV light, it must be coming from very hot, massive stars. We also know that these stars don't live very long, so they must have formed recently --- this area must then be a region of star formation. The degree to which the overall spectrum is skewed towards the blue gives a rough indication of the star formation rate.
This doesn't make any sense. Galaxies don't expand, the Universe does. What does 'tearing' spacetime mean? How does this create (or use?) energy? We don't need anything so esoteric --- it is fairly well-accepted now that the early galaxies were probably small and vigorous centers of star formation, later merging into the flavors we see closer around us today. We are now seeing confirmation of these ideas.
Even if, at first, it is a way of simply defining what we mean by taking the square root of a negative number, the truly wonderful thing is the deep connection that is revealed between the complex numbers and "ordinary" functions through Euler's formula. Also, it means that we can now solve *any* algebraic equation, as well as a number of equally beautiful relationships in complex analysis. You might argue it was "defined", but I look at it as being "discovered".
...they eventually figured out that stars work with nuclear processes...
There is also the fact that the sun's mass is not enough to gravitationally oppose the huge outward pressures generated by a thermonuclear reaction at the needed temperatures. Gravity is simply too weak to overcome the strong nuclear and electrical forces that would have to be present in such a thermonuclear reaction furnace.
What? Balancing the pressure equation of state is how we numerically predict the structure of the Sun in the first place. Where did you hear that?
Then there is the missing neutrino problem. From thermonuclear fusion experiments and bombs, we know what the production rate of associated neutrinos should be for the sun IF it were indeed powered by fusion, as theorized. However, the actual neutrino flux from the sun is only a tiny fraction of what should be measured if fusion were the energy source of the sun. At this point scientists really are back to square one in determining the power source of the sun and similar sized stars.
This was a problem before 10 or so years ago, though (a) the solution was guessed at 30 years ago, and (b) it's not a "tiny" fraction, it was about a third. Neutrinos change species. There is no more mystery
There is also radar evidence that the sun is not a big gas ball, but actually has a solid iron core, similar to the earth, surrounded by an atmosphere of seething plasma kept hot by an as yet unknown external electrical power grid, in the same way as a metal arc lamp here on earth. There is some evidence that the sun, along with other stars in the spiral arms of our galaxy, is part of a galactic scale electrical power distribution system powered from the center of our galaxy.
A solid iron core??? Where are you getting this stuff? The central density is around 15 times higher than iron! Chemical reactions cannot power the Sun at its current luminosity for billions of years. Can I recommend to you a nice introductory astronomy (science) book?
Well, I really meant the cutting/pasting within the document, like joining a few lines together with repeated 'J's and then doing a 'gq' on the unsightly text. But point taken.
A good partner to the indenting keystroke "=" is "gq", to automatically format highlighted text that is messy from copy/pastes. I use the pair all the time to save headaches.
A simpler issue is that of the "butterfly" ballot, a layout confusing to many elderly voters in Broward county. In this predominantly *Jewish* precinct, Pat Buchanan (!) received a disproportionate spike of votes intended for Gore. How disproportionate? The odds that this neighborhood voted for Buchanan accurately turns out to be a **62-sigma** event if you suppose that the votes were representative of the voters' wishes. We usually reject the validity of 62-sigma events. Even supposing that the precinct had a makeup similar to the Florida average (there was a slight Democratic majority) enough votes swing from Buchanan to Gore to tip the state to Gore.
What?? Where in the field equations is there an anomaly? If it *were* some anomaly in the field equations, we'd see really bizarre effects everywhere else there are strong gravitational fields. We don't.
The point is that it's not a strange theoretical solution, but a real, physical deflection of light by a gravitating mass. It is certainly evidence of unseen matter --- were there a cloud of unseen matter, this is exactly the effect it would have on passing light. To attribute it instead to a non-specific flaw in a theory we know *very* well is far more speculative than what you criticize others for.
I don't think "uncomfortable" is the right word. Certainly there is a huge upside to overturning the standard way of thinking, but also a huge risk in supporting ideas that seem untenable.
Dark matter is inferred from a number of observations and calculations, including
excess rotation speed of stars around galactic centers, excess speed of members of clusters of galaxies, and lensing of background galaxies not associated with luminous matter.
While one may fiddle with MOND to possibly fit the first two phenomena (for a specific case, moreover --- one adjustment to Newton's laws had better account for *all* rotation curves), the last group of observations really seem to argue strongly against any reasonable form of MOND.
If you google the Bullet Cluster image and description, you'll note that the blue region (most lensing of background) is tracing the highest density of matter, where the pink traces the density of luminous (here, X-ray cluster gas) matter. It is clear that there is a huge component of matter not identified with luminous matter. To account for this with MOND, it is not enough to increase the *strength* of the gravitational field, but also now the *direction*, since we observe the lensing in a direction roughly perpendicular to the axis of the cluster. Writing down such a gravitational law to account for this case would make any astrophysicist uncomfortable indeed.
Now, especially since we can work backwards and calculate the distribution of dark matter needed to cause each observation, dark matter seems to be the *much* simpler explanation. Besides, we already have examples of matter that interact only gravitationally (and possibly weakly) --- neutrinos. As hard as it is to detect them, there may well be others we don't know about yet.
I am appalled at the acrimonious nature of so many posts when a subject like this comes up. Is Darwinism so sacrosanct that it can never be questioned?
Of course not. It's a question of authority. Evolutionary biology is questioned hundreds of times per day in the relevant literature and amongst the professionals who spend their lives working in the field. The salient point is that now the way is cleared for the theory to be questioned ignorantly by lawyers, elementary teachers, and others who raise inane and simple objections that are quickly rebutted by any specialist. I strongly oppose science education curriculae set by those with little or no science education.
There are questions that Darwinism cannot answer. Intelligent Design is about a search for the answers to those questions. Intelligent design theory does not say that the universe is too complex to be explained by evolution.
I think that's exactly what it says. ID, and its adherents, are not interested in a "search" for the answer. They are committed to asserting the solution to questions about unknowns via postulating unknowns (what is the nature of "intelligence", anyway?). If they were *really* interested in the questions, they'd be doing science.
Many things are very complex. A pile of sand is complex, for instance.
In what way?
And a pile of sand might evolve if more sand were dumped on the pile every day. What separates one type of complexity (such as a pile of sand) from another type of complexity (such as a living organism) is that one type seems to require some kind of intelligence.
There is far more to the idea of "complexity" than this arbitrary and shallow distinction. Natural phenomena are perfectly capable of generating complex behaviors and structures. The onus is on the IDer --- what about the complexity of living things places them outside the *possible* domain of natural laws?
In that respect, the universe and a good book seem to have more in common than a sand pile has to either of them.
What a crazy argument. The Universe is surely more subtle and wonderful than we can presently understand, and maybe possibly understand. The only avenue for understanding the fundamental workings of the Universe is science.
The majority of cost for me to go to a community college here in California is the books, and it is such a scam by the book companies, which also left me wondering "does the teacher get a kick back?"
Yes, teachers do get a kick back. One of my professors told our post grad class (during one of the much loved 'pub lectures') how they could stand to make $1000s from recommending the 'right' books.
I'm a physics/astronomy professor, and this is news to me. In fact, there is a state law (OK) that prevents us from receiving *any* financial incentive from textbook reps. In fact, it is even illegal for us to sell our evaluation copies. There are always unethical people on both sides of the street, I suppose.
The basis for every response here is - the study suggests this is a basic, fundamental, empirical fact of astronomy that a century of viewing galaxies has managed to overlook.
Well, overlook might be too strong a word. With the availability of modern databases, these new statistical studies can revise old estimates --- in this case, the old mass/light estimate for some galaxies.
In order to establish your upper limit, astrophysicists had to postulate exotic, undetectable forms of matter.
It didn't work out quite that way. Observations strongly suggest a flat universe, and Big Bang nucleosynthesis, deuterium/lithium observations, and cosmological surveys all pointed to a total mass density of about a third necessary for flatness, with only 4-5% or so contributed by baryons. The realization that the matter was somehow exotic was slowly revealed as we tried to study its properties. Of course its not "undetectable", since it is clearly manifest in the rotation curve anomalies of galaxies, the dynamics of clusters, and the lensing effects on cosmological scales.
Even then, all their calculations couldn't agree with cosmological data, so they had to bring up dark energy - which they can barely begin to agree on, much less explain.
I think pretty much everyone agrees with the concept and dynamic effect of "dark energy" (horrible name!), but you are right that no one has a good explanation for it as of now. It's a very exciting time in cosmology.
Occam's razor, combined with articles like this, offers a strong suggestion to those of us not versed in your particular specialty, that you're simply missing out on some fundamental observation. Perhaps in 2031 a physicist will smack themselves over the head and go "But of course WMAP came out even, the intergalactic dust that we'd always assumed was trivial ended up diffusing the CMB!!" or some other obvious-in-retrospect observation, and the entire need for 'dark energy' and 'dark matter' will cease to exist... Myths that helped astronomers of their day reason out what they observed much as the Zodiac did millenia earlier.
It is too true that whatever model we construct to explain nature today will be refined, and perhaps overturned, in the future. But we can't just throw up our hands and wait for those relevations to happen. On the contrary, the spirit of Occam is alive and well in cosmology. Is there a simpler explanation that will unify the above phenomena? (rotation curves, cluster dynamics, lensing) If so, a legion of astrophysicists would like to follow your lead. I'd be very surprised if something like dark matter were not to exist. It's very hard to imagine something that acts *exactly* like clouds of weakly-interacting matter that is *not* clouds of weakly-interacting matter.
One question - could this observation (that there exists a larger-than-expected galactic halo of interstellar dust (rather than dark matter)) at least be used to explain the galactic rotation rate problem?
No --- the anomalous curves exist for almost all sampled spirals (in fact, there was a recent report that there was one interesting spiral that did *not* exhibit such a curve), and notably, for *ours*. Such an enhanced ring of dust would obscure observations of the outskirts of our own galaxy in a striking and obvious way, and it would be easily seen in neighboring galaxies as well. Further, the rotation problem is such that an amount of mass equal to about 8-9 times the stellar mass of galaxies has to be postulated. There is no evidence of anywhere near that much dust even in this latest survey.
I wouldn't think so, unless, for some reason, someone's distance methods only used a biased sample of edge-on galaxies. Also, I'm a little puzzled why this is surprising, since it's usually pretty easy to tell when an object's light has been absorbed by intervening dust ("reddened"). Dust preferentially absorbs/scatters shorter-wavelength light, so a standard technique when observing is to "de-redden" the data --- we know, based upon quantum probabilities, the ideal ratio of, say, H-alpha to H-beta. If there isn't as much H-beta as we expect, based upon the H-alpha, we associate this with dust. We can even calculate the column density of dust in this way. Surely this has been done for most of these galaxies.
But, this newly found dust, which blocks light, must do something with that energy - either gain mass or re-radiate it, right? Could not that re-radiation be a part of the CMB, which would in turn have an affect on the calculated amount of baryonic dark matter. If it's not part of the CMB, where is this lost energy accounted for? Nope. As stated in the article, dust that absorbs starlight re-radiates it in the infrared. The CMB is, as given by the name, microwave radiation, which corresponds to a temperature of about 3K. Any emission from dust that is warmer than the background universe must emit at a wavelength shorter than the CMB.
What matters most in the calculation of baryonic upper limits is the variation of the CMB with position in the sky. The size of these fluctuations gives us a way to measure the interior angles of "triangles" across the universe to get a sense of the overall geometry of the universe, much like measuring the interior angles of triangles on a sphere reveals its curved geometry. The observed size of the fluctuations tells us very precisely that the universe, globally, has a flat geometry.
As said in the article, this only adds maybe 20% to the existing estimate of 4-5% of baryonic matter, so it won't change things much. Also, this dust should be emitting in the IR, so I'd be interested to see if this has been seen already by IR observations, and if not, why not.
What you mean to say is that the theory of life, the universe and everything which you subscribe to breaks if there is no exotic dark matter. There is no proven "upper limit on the amount of baryonic mass in the universe," there are only theories and hypothesis which make that claim as part of their model. I won't try and prove a negative by saying that theory is necessarily wrong, but the onus is on you to prove that portion of it correct by finding some of this imaginary non-baryonic mass. Myself, I'll claim that the Flying Spaghetti Monster plays with the gravitational "constant" to fool with us. Prove me wrong.
Your circular logic fails to prove that dark matter exists. You might have a point if, in science, we were in the habit of proving things. Nothing is ever "proved" in science. Nobody cooked up the idea of "dark matter" and went out trying to find supporting observations; rather, the anomalies in a number of different phenomena leads one to this idea. "Dark Matter" is the simplest explanation we can imagine for these many different observations. Altering the gravitational constant in a specific, scale-dependent way may allow you to solve the galactic rotation curve problem, for a particular galaxy, but you'd need to invent an entirely new change of the constant at galactic cluster scales, where the dark matter effects are also observed. Worse still, the Bullet Cluster observations imply a lensing effect of the dark matter halo, so not only do you need to fiddle with the *magnitude* of the gravitational constant, but also its *direction* in a way to precisely fit the data. We (I am an astrophysicist) tend to think that the Bullet Cluster, for all practical purposes, ends the viability of various modified gravity hypotheses. Some people still work on them, but they're getting harder and harder to justify in general.
The upper limit on the amount of baryonic matter is computed with increasing precision based upon WMAP and other CMB observations. It's something like 4-5% of the total mass of the universe. You should avail yourself of the procedure used to get the result. It's a beautiful calculation.
Probably in all those schools that currently don't allow discussion on anything that's disagreed with. (This doesn't just go for evolution. Try being a liberal with a conservative professor, or try being a conservative in a class with a liberal professor.) Often the case any discussion is far less about discussion and more so about intimidation. Either you've had terrible schooling, or have heard some horror stories. I am a professor, I've been in *lots* of classrooms on both ends, and such blanket statements are completely misrepresentative.
"Um... because evolution can be observed"
Really, I have yet to see any evolution be observed in my can of peanut butter. And heck, I've given it the advantage of tons of organic matter. You've picked an odd example, because peanut butter is an interesting anhydrous medium. Indeed, it is hard to get peanut butter to spoil or grow much bacterial life.
Oh wait...it's supposed to be observed over millions of years. Even though we constantly have discovered where x variant of animal is thought to have been derived from y. But then we later find y concurrent or even before x. Can you point to even one example of this?
But then again, survival of the fittest dictates that in the end there will be only one species within the environment. You exhibit a startling lack of education in biological science. There are many possible environments and different resources that cannot all be exploited by one species.
If you look at the genetic code, the similarities the re-use of design patterns. It is not surprising that descendants will inherit those traits from their parents that enabled them to successfully procreate, or at least didn't *keep* them from procreating.
In truth, I think scientists are afraid. *All* of them? There are thousands of biologists and zoologists. Where in their schooling do they pick up this fear? Is is spoken of publicly between them, or is it a closeted shame? I know lots of these cowardly scientists, and they seem to bear the cross of this secret fear cheerfully well.
It is a good attitude to maintain skepticism about assertions and ideas --- you are in a prime position to actually learn about evolution and other areas of science.
But please, I'm begging you, steer wide of websites like Answers in Genesis and the ilk. You will find little honest science there, only phantom plastic arguments that sound like real science. You should challenge presuppositions in the strongest way --- which is to become a scientist yourself. Can you imagine how famous you'd be by overturning the life's work of thousands of very smart people over the last hundred years or so? But don't fall for the easy, grade-school arguments of the charlatans. There are so many subtle and important errors in the page you referred to that you'll never claw your way back out into the world of clear thinking.
Our effect on the asteroid is still probably smaller than the error bars in the projected orbit. Which means that we could be as likely to push it *into* a collisional path as *out* of one.
Don't get me wrong, I am a HUGE fan of linux, I use it on all my computers. However, there is no point in releasing drivers for this in Linux because the only use would be physics accelerated games, which won't be ported to Linux anyway.
The *only* use?? Geez, I'd like to get my hands on the API to write some physics educational/demonstration software. Or just create physically accurate simulations for kicks. We don't *have* to rely on others to write software for us.
It's pretty easy to tell the difference between a true cosmological redshift, where all the spectral lines are shifted by some scale percentage, and red light from a star in our own galaxy that does not have redshifted spectral lines. Red stars look red because most of their light in the visible part of the spectrum is red, not because the spectral lines have been shifted.
Slashdot Mirror
If you look at a population of stars and see lots of blue or UV light, it must be coming from very hot, massive stars. We also know that these stars don't live very long, so they must have formed recently --- this area must then be a region of star formation. The degree to which the overall spectrum is skewed towards the blue gives a rough indication of the star formation rate.
This doesn't make any sense. Galaxies don't expand, the Universe does. What does 'tearing' spacetime mean? How does this create (or use?) energy? We don't need anything so esoteric --- it is fairly well-accepted now that the early galaxies were probably small and vigorous centers of star formation, later merging into the flavors we see closer around us today. We are now seeing confirmation of these ideas.
Even if, at first, it is a way of simply defining what we mean by taking the square root of a negative number, the truly wonderful thing is the deep connection that is revealed between the complex numbers and "ordinary" functions through Euler's formula. Also, it means that we can now solve *any* algebraic equation, as well as a number of equally beautiful relationships in complex analysis. You might argue it was "defined", but I look at it as being "discovered".
...they eventually figured out that stars work with nuclear processes...
There is also the fact that the sun's mass is not enough to gravitationally oppose the huge outward pressures generated by a thermonuclear reaction at the needed temperatures. Gravity is simply too weak to overcome the strong nuclear and electrical forces that would have to be present in such a thermonuclear reaction furnace.
What? Balancing the pressure equation of state is how we numerically predict the structure of the Sun in the first place. Where did you hear that?
Then there is the missing neutrino problem. From thermonuclear fusion experiments and bombs, we know what the production rate of associated neutrinos should be for the sun IF it were indeed powered by fusion, as theorized. However, the actual neutrino flux from the sun is only a tiny fraction of what should be measured if fusion were the energy source of the sun. At this point scientists really are back to square one in determining the power source of the sun and similar sized stars.
This was a problem before 10 or so years ago, though (a) the solution was guessed at 30 years ago, and (b) it's not a "tiny" fraction, it was about a third. Neutrinos change species. There is no more mystery
There is also radar evidence that the sun is not a big gas ball, but actually has a solid iron core, similar to the earth, surrounded by an atmosphere of seething plasma kept hot by an as yet unknown external electrical power grid, in the same way as a metal arc lamp here on earth. There is some evidence that the sun, along with other stars in the spiral arms of our galaxy, is part of a galactic scale electrical power distribution system powered from the center of our galaxy.
A solid iron core??? Where are you getting this stuff? The central density is around 15 times higher than iron! Chemical reactions cannot power the Sun at its current luminosity for billions of years. Can I recommend to you a nice introductory astronomy (science) book?
Cool --- I'm another former Boyd student. Had many of his classes. One of the best lecturers I've ever had.
Well, I really meant the cutting/pasting within the document, like joining a few lines together with repeated 'J's and then doing a 'gq' on the unsightly text. But point taken.
A good partner to the indenting keystroke "=" is "gq", to automatically format highlighted text that is messy from copy/pastes. I use the pair all the time to save headaches.
Thanks for the great layout and design!
The point is that it's not a strange theoretical solution, but a real, physical deflection of light by a gravitating mass. It is certainly evidence of unseen matter --- were there a cloud of unseen matter, this is exactly the effect it would have on passing light. To attribute it instead to a non-specific flaw in a theory we know *very* well is far more speculative than what you criticize others for.
and perhaps weakly. Why is that of concern? It would be composed of neutral particles of small cross-section.
Why do you suppose DM violates all known properties of matter (save one)?
In case you don't get my response above, google for Bullet Cluster. There you'll see the lensing.
Dark matter is inferred from a number of observations and calculations, including excess rotation speed of stars around galactic centers, excess speed of members of clusters of galaxies, and lensing of background galaxies not associated with luminous matter. While one may fiddle with MOND to possibly fit the first two phenomena (for a specific case, moreover --- one adjustment to Newton's laws had better account for *all* rotation curves), the last group of observations really seem to argue strongly against any reasonable form of MOND.
If you google the Bullet Cluster image and description, you'll note that the blue region (most lensing of background) is tracing the highest density of matter, where the pink traces the density of luminous (here, X-ray cluster gas) matter. It is clear that there is a huge component of matter not identified with luminous matter. To account for this with MOND, it is not enough to increase the *strength* of the gravitational field, but also now the *direction*, since we observe the lensing in a direction roughly perpendicular to the axis of the cluster. Writing down such a gravitational law to account for this case would make any astrophysicist uncomfortable indeed.
Now, especially since we can work backwards and calculate the distribution of dark matter needed to cause each observation, dark matter seems to be the *much* simpler explanation. Besides, we already have examples of matter that interact only gravitationally (and possibly weakly) --- neutrinos. As hard as it is to detect them, there may well be others we don't know about yet.
I am appalled at the acrimonious nature of so many posts when a subject like this comes up. Is Darwinism so sacrosanct that it can never be questioned?
Of course not. It's a question of authority. Evolutionary biology is questioned hundreds of times per day in the relevant literature and amongst the professionals who spend their lives working in the field. The salient point is that now the way is cleared for the theory to be questioned ignorantly by lawyers, elementary teachers, and others who raise inane and simple objections that are quickly rebutted by any specialist. I strongly oppose science education curriculae set by those with little or no science education.
There are questions that Darwinism cannot answer. Intelligent Design is about a search for the answers to those questions. Intelligent design theory does not say that the universe is too complex to be explained by evolution.
I think that's exactly what it says. ID, and its adherents, are not interested in a "search" for the answer. They are committed to asserting the solution to questions about unknowns via postulating unknowns (what is the nature of "intelligence", anyway?). If they were *really* interested in the questions, they'd be doing science.
Many things are very complex. A pile of sand is complex, for instance.
In what way?
And a pile of sand might evolve if more sand were dumped on the pile every day. What separates one type of complexity (such as a pile of sand) from another type of complexity (such as a living organism) is that one type seems to require some kind of intelligence.
There is far more to the idea of "complexity" than this arbitrary and shallow distinction. Natural phenomena are perfectly capable of generating complex behaviors and structures. The onus is on the IDer --- what about the complexity of living things places them outside the *possible* domain of natural laws?
In that respect, the universe and a good book seem to have more in common than a sand pile has to either of them.
What a crazy argument. The Universe is surely more subtle and wonderful than we can presently understand, and maybe possibly understand. The only avenue for understanding the fundamental workings of the Universe is science.
The majority of cost for me to go to a community college here in California is the books, and it is such a scam by the book companies, which also left me wondering "does the teacher get a kick back?"
Yes, teachers do get a kick back. One of my professors told our post grad class (during one of the much loved 'pub lectures') how they could stand to make $1000s from recommending the 'right' books.
I'm a physics/astronomy professor, and this is news to me. In fact, there is a state law (OK) that prevents us from receiving *any* financial incentive from textbook reps. In fact, it is even illegal for us to sell our evaluation copies. There are always unethical people on both sides of the street, I suppose.
In order to establish your upper limit, astrophysicists had to postulate exotic, undetectable forms of matter.Well, overlook might be too strong a word. With the availability of modern databases, these new statistical studies can revise old estimates --- in this case, the old mass/light estimate for some galaxies.
Even then, all their calculations couldn't agree with cosmological data, so they had to bring up dark energy - which they can barely begin to agree on, much less explain.It didn't work out quite that way. Observations strongly suggest a flat universe, and Big Bang nucleosynthesis, deuterium/lithium observations, and cosmological surveys all pointed to a total mass density of about a third necessary for flatness, with only 4-5% or so contributed by baryons. The realization that the matter was somehow exotic was slowly revealed as we tried to study its properties. Of course its not "undetectable", since it is clearly manifest in the rotation curve anomalies of galaxies, the dynamics of clusters, and the lensing effects on cosmological scales.
Occam's razor, combined with articles like this, offers a strong suggestion to those of us not versed in your particular specialty, that you're simply missing out on some fundamental observation. Perhaps in 2031 a physicist will smack themselves over the head and go "But of course WMAP came out even, the intergalactic dust that we'd always assumed was trivial ended up diffusing the CMB!!" or some other obvious-in-retrospect observation, and the entire need for 'dark energy' and 'dark matter' will cease to exist... Myths that helped astronomers of their day reason out what they observed much as the Zodiac did millenia earlier.I think pretty much everyone agrees with the concept and dynamic effect of "dark energy" (horrible name!), but you are right that no one has a good explanation for it as of now. It's a very exciting time in cosmology.
One question - could this observation (that there exists a larger-than-expected galactic halo of interstellar dust (rather than dark matter)) at least be used to explain the galactic rotation rate problem?It is too true that whatever model we construct to explain nature today will be refined, and perhaps overturned, in the future. But we can't just throw up our hands and wait for those relevations to happen. On the contrary, the spirit of Occam is alive and well in cosmology. Is there a simpler explanation that will unify the above phenomena? (rotation curves, cluster dynamics, lensing) If so, a legion of astrophysicists would like to follow your lead. I'd be very surprised if something like dark matter were not to exist. It's very hard to imagine something that acts *exactly* like clouds of weakly-interacting matter that is *not* clouds of weakly-interacting matter.
No --- the anomalous curves exist for almost all sampled spirals (in fact, there was a recent report that there was one interesting spiral that did *not* exhibit such a curve), and notably, for *ours*. Such an enhanced ring of dust would obscure observations of the outskirts of our own galaxy in a striking and obvious way, and it would be easily seen in neighboring galaxies as well. Further, the rotation problem is such that an amount of mass equal to about 8-9 times the stellar mass of galaxies has to be postulated. There is no evidence of anywhere near that much dust even in this latest survey.
I wouldn't think so, unless, for some reason, someone's distance methods only used a biased sample of edge-on galaxies. Also, I'm a little puzzled why this is surprising, since it's usually pretty easy to tell when an object's light has been absorbed by intervening dust ("reddened"). Dust preferentially absorbs/scatters shorter-wavelength light, so a standard technique when observing is to "de-redden" the data --- we know, based upon quantum probabilities, the ideal ratio of, say, H-alpha to H-beta. If there isn't as much H-beta as we expect, based upon the H-alpha, we associate this with dust. We can even calculate the column density of dust in this way. Surely this has been done for most of these galaxies.
What matters most in the calculation of baryonic upper limits is the variation of the CMB with position in the sky. The size of these fluctuations gives us a way to measure the interior angles of "triangles" across the universe to get a sense of the overall geometry of the universe, much like measuring the interior angles of triangles on a sphere reveals its curved geometry. The observed size of the fluctuations tells us very precisely that the universe, globally, has a flat geometry.
As said in the article, this only adds maybe 20% to the existing estimate of 4-5% of baryonic matter, so it won't change things much. Also, this dust should be emitting in the IR, so I'd be interested to see if this has been seen already by IR observations, and if not, why not.
The upper limit on the amount of baryonic matter is computed with increasing precision based upon WMAP and other CMB observations. It's something like 4-5% of the total mass of the universe. You should avail yourself of the procedure used to get the result. It's a beautiful calculation.
But please, I'm begging you, steer wide of websites like Answers in Genesis and the ilk. You will find little honest science there, only phantom plastic arguments that sound like real science. You should challenge presuppositions in the strongest way --- which is to become a scientist yourself. Can you imagine how famous you'd be by overturning the life's work of thousands of very smart people over the last hundred years or so? But don't fall for the easy, grade-school arguments of the charlatans. There are so many subtle and important errors in the page you referred to that you'll never claw your way back out into the world of clear thinking.
Our effect on the asteroid is still probably smaller than the error bars in the projected orbit. Which means that we could be as likely to push it *into* a collisional path as *out* of one.
The *only* use?? Geez, I'd like to get my hands on the API to write some physics educational/demonstration software. Or just create physically accurate simulations for kicks. We don't *have* to rely on others to write software for us.
It's pretty easy to tell the difference between a true cosmological redshift, where all the spectral lines are shifted by some scale percentage, and red light from a star in our own galaxy that does not have redshifted spectral lines. Red stars look red because most of their light in the visible part of the spectrum is red, not because the spectral lines have been shifted.