<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>People keep bringing up MOND, but it simply does not work. They can get it to work for certain things, but when you try to extend its application it utterly fails. I took a few classes with the third author of the Bullet Cluster paper where they found observational evidence of "dark matter", and it seems to be well understood as far as its dynamics, we just don't know what it's made of...he went through a detailed explanation of all the reasons MOND is a failed theory, yet people still bring it up. I'd argue that the name "dark matter" is a place holder, but when we discover what it actually is, it will still be the same thing we are studying, we'll just have a more clear definition of what it is and by extension have a better way to study it further. <br />Posted by UFmbutler</DIV></p><p>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.</p><p>I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /></p> <div class="Discussion_UserSignature"> </div>
- Status
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>People keep bringing up MOND, but it simply does not work. They can get it to work for certain things, but when you try to extend its application it utterly fails. I took a few classes with the third author of the Bullet Cluster paper where they found observational evidence of "dark matter", and it seems to be well understood as far as its dynamics, we just don't know what it's made of...he went through a detailed explanation of all the reasons MOND is a failed theory, yet people still bring it up. I'd argue that the name "dark matter" is a place holder, but when we discover what it actually is, it will still be the same thing we are studying, we'll just have a more clear definition of what it is and by extension have a better way to study it further. <br />Posted by UFmbutler</DIV></p><p>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.</p><p>I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /></p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /> Posted by DrRocket</DIV></p><p>I agree, I was just saying that I believe we are observing the effects of dark matter, whatever it is. So when we do figure it out, we'll certainly approach it from a different perspective, but we'd still be studying the underlying cause of the same phenomena. </p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /> Posted by DrRocket</DIV></p><p>I agree, I was just saying that I believe we are observing the effects of dark matter, whatever it is. So when we do figure it out, we'll certainly approach it from a different perspective, but we'd still be studying the underlying cause of the same phenomena. </p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /> Posted by DrRocket</DIV></p><p>I agree, I was just saying that I believe we are observing the effects of dark matter, whatever it is. So when we do figure it out, we'll certainly approach it from a different perspective, but we'd still be studying the underlying cause of the same phenomena. </p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I am not surprised that MOND is difficult to extend. Of course you can get it to work for certain things -- it is just a curve fit. I would be personally distressed if it ever goes anywhere, it is the ugliest possible physical theory.I would also argue that if and when dark matter is identified it will not be just the same thing that we are studying. If and when it is identified there will come with that identification a set of properties, either based on known matter or based on research into whatever the new stuff might be. Those properties ought to provide a basis for understanding why dark matter is distributed in whatever manner in which we ultimately find out that it is distributed, with what forces of nature it interacts and why, how it interacts with the matter that we understand now, and why it is apparently not detectable except by gravitational effects. Given that it seems to be most of the matter in the universe, there ought to be something of a revolution in our understanding of particle physics at that point. If it turns out that dark matter feels the gravitational force and nothing else that would be rather startling, would it not ? But maybe that is the problem. Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces. We have no quantum theory for gravity. If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories. <br /> Posted by DrRocket</DIV></p><p>I agree, I was just saying that I believe we are observing the effects of dark matter, whatever it is. So when we do figure it out, we'll certainly approach it from a different perspective, but we'd still be studying the underlying cause of the same phenomena. </p> <div class="Discussion_UserSignature"> </div>
<p>See "Mysterioud Source of HE Cosmic Rays "discovered" thread.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
<p>See "Mysterioud Source of HE Cosmic Rays "discovered" thread.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
<p>See "Mysterioud Source of HE Cosmic Rays "discovered" thread.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
<p>See "Mysterioud Source of HE Cosmic Rays "discovered" thread.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
<p>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales.</p><p> </p>
<p>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales.</p><p> </p>
<p>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales.</p><p> </p>
<p>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales.</p><p> </p>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV></p><p>I don't think I agree, but this is just a matter of personal taste. Newton's inverse square law not only works, it is elegant. General relativity which manages to explain gravity in terms of geometry, is perhaps more elegant. Both qualify as beautiful theories. </p><p>MOND is a curve fit, nothing more. There is no particular rhyme or reason to the curve fit, no basic principle. It is hideous.</p><p>There is quite a long history in physics suggesting that correct theories are beautiful. Even when found to require revision both the original theory and the successful refinement have been aesthetically pleasing. MOND is not.</p><p>I am not overly wild about a particle that responds only to gravity either. Unless, perhaps that is explainable via some elegant piece of work in quantum field theory -- but if that is the case no one as any inkling what piece of work might be.</p><p>Personally, I like "none of the above" at the moment. But that is just a hope, without any good basis, and I am probably wrong. I have a guess, and it is nothing more than a guess. The problem with our understanding of gravity has its roots in the behavior at very small scales, not large ones. I think general relativity is pretty good at large scales. We know that it is at odds with quantum theory, and quantum theory is very accurate at small scales. But again that is just a guess, no data, and no suggestions as to how to increase our understanding. <br /></p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV></p><p>I don't think I agree, but this is just a matter of personal taste. Newton's inverse square law not only works, it is elegant. General relativity which manages to explain gravity in terms of geometry, is perhaps more elegant. Both qualify as beautiful theories. </p><p>MOND is a curve fit, nothing more. There is no particular rhyme or reason to the curve fit, no basic principle. It is hideous.</p><p>There is quite a long history in physics suggesting that correct theories are beautiful. Even when found to require revision both the original theory and the successful refinement have been aesthetically pleasing. MOND is not.</p><p>I am not overly wild about a particle that responds only to gravity either. Unless, perhaps that is explainable via some elegant piece of work in quantum field theory -- but if that is the case no one as any inkling what piece of work might be.</p><p>Personally, I like "none of the above" at the moment. But that is just a hope, without any good basis, and I am probably wrong. I have a guess, and it is nothing more than a guess. The problem with our understanding of gravity has its roots in the behavior at very small scales, not large ones. I think general relativity is pretty good at large scales. We know that it is at odds with quantum theory, and quantum theory is very accurate at small scales. But again that is just a guess, no data, and no suggestions as to how to increase our understanding. <br /></p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV></p><p>I don't think I agree, but this is just a matter of personal taste. Newton's inverse square law not only works, it is elegant. General relativity which manages to explain gravity in terms of geometry, is perhaps more elegant. Both qualify as beautiful theories. </p><p>MOND is a curve fit, nothing more. There is no particular rhyme or reason to the curve fit, no basic principle. It is hideous.</p><p>There is quite a long history in physics suggesting that correct theories are beautiful. Even when found to require revision both the original theory and the successful refinement have been aesthetically pleasing. MOND is not.</p><p>I am not overly wild about a particle that responds only to gravity either. Unless, perhaps that is explainable via some elegant piece of work in quantum field theory -- but if that is the case no one as any inkling what piece of work might be.</p><p>Personally, I like "none of the above" at the moment. But that is just a hope, without any good basis, and I am probably wrong. I have a guess, and it is nothing more than a guess. The problem with our understanding of gravity has its roots in the behavior at very small scales, not large ones. I think general relativity is pretty good at large scales. We know that it is at odds with quantum theory, and quantum theory is very accurate at small scales. But again that is just a guess, no data, and no suggestions as to how to increase our understanding. <br /></p> <div class="Discussion_UserSignature"> </div>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV></p><p>I don't think I agree, but this is just a matter of personal taste. Newton's inverse square law not only works, it is elegant. General relativity which manages to explain gravity in terms of geometry, is perhaps more elegant. Both qualify as beautiful theories. </p><p>MOND is a curve fit, nothing more. There is no particular rhyme or reason to the curve fit, no basic principle. It is hideous.</p><p>There is quite a long history in physics suggesting that correct theories are beautiful. Even when found to require revision both the original theory and the successful refinement have been aesthetically pleasing. MOND is not.</p><p>I am not overly wild about a particle that responds only to gravity either. Unless, perhaps that is explainable via some elegant piece of work in quantum field theory -- but if that is the case no one as any inkling what piece of work might be.</p><p>Personally, I like "none of the above" at the moment. But that is just a hope, without any good basis, and I am probably wrong. I have a guess, and it is nothing more than a guess. The problem with our understanding of gravity has its roots in the behavior at very small scales, not large ones. I think general relativity is pretty good at large scales. We know that it is at odds with quantum theory, and quantum theory is very accurate at small scales. But again that is just a guess, no data, and no suggestions as to how to increase our understanding. <br /></p> <div class="Discussion_UserSignature"> </div>
<p>Well, good Dr. I bow to exceedingly superior knowledge in the matter and join you in my distaste for "all of the above".</p><p>The recent flurry of extraplanet discoveries leads me to wonder if harder to spot "normal" matter (such as brown dwarfs and cool star remenants) may be more prevelant tha estimated and thus may mitigate a larger share of "missing matter" than thought (not that I would venture that is the answer in and of itself). Is that at all plausible?</p>
<p>Well, good Dr. I bow to exceedingly superior knowledge in the matter and join you in my distaste for "all of the above".</p><p>The recent flurry of extraplanet discoveries leads me to wonder if harder to spot "normal" matter (such as brown dwarfs and cool star remenants) may be more prevelant tha estimated and thus may mitigate a larger share of "missing matter" than thought (not that I would venture that is the answer in and of itself). Is that at all plausible?</p>
<p>Well, good Dr. I bow to exceedingly superior knowledge in the matter and join you in my distaste for "all of the above".</p><p>The recent flurry of extraplanet discoveries leads me to wonder if harder to spot "normal" matter (such as brown dwarfs and cool star remenants) may be more prevelant tha estimated and thus may mitigate a larger share of "missing matter" than thought (not that I would venture that is the answer in and of itself). Is that at all plausible?</p>
<p>Well, good Dr. I bow to exceedingly superior knowledge in the matter and join you in my distaste for "all of the above".</p><p>The recent flurry of extraplanet discoveries leads me to wonder if harder to spot "normal" matter (such as brown dwarfs and cool star remenants) may be more prevelant tha estimated and thus may mitigate a larger share of "missing matter" than thought (not that I would venture that is the answer in and of itself). Is that at all plausible?</p>
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV><br /><br />As Dr Rocket said, with no real understanding of the root cause, it is all a matter of preferences. I prefer that gravity works as we understand...it sure works well for navigating around our neck of the woods.</p><p>At this point, it is all a rather entertaining mystery that we scientists are investigating with extreme effort. I hope some answers will be forthcoming within the next decade, so that I'll live long enough to gain some understanding.</p><p>After all, the moniker "Dark Matter" means we don't know enough about the properties of whatever it is to understand at this point.</p><p>I like having some unknowns out there! 
</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div><p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV><br /><br />As Dr Rocket said, with no real understanding of the root cause, it is all a matter of preferences. I prefer that gravity works as we understand...it sure works well for navigating around our neck of the woods.</p><p>At this point, it is all a rather entertaining mystery that we scientists are investigating with extreme effort. I hope some answers will be forthcoming within the next decade, so that I'll live long enough to gain some understanding.</p><p>After all, the moniker "Dark Matter" means we don't know enough about the properties of whatever it is to understand at this point.</p><p>I like having some unknowns out there! </p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div><p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The concept of a particle that is only(?) affected by gravity is a less palatable theory to me than the idea that we may have a basic misunderstanding of how gravity works on larger scales. <br />Posted by Doc_Grey</DIV><br /><br />As Dr Rocket said, with no real understanding of the root cause, it is all a matter of preferences. I prefer that gravity works as we understand...it sure works well for navigating around our neck of the woods.</p><p>At this point, it is all a rather entertaining mystery that we scientists are investigating with extreme effort. I hope some answers will be forthcoming within the next decade, so that I'll live long enough to gain some understanding.</p><p>After all, the moniker "Dark Matter" means we don't know enough about the properties of whatever it is to understand at this point.</p><p>I like having some unknowns out there! </p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>- Status
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