Dark Matter...WTH?

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I think it is definitely a place holder.&nbsp; I don't think it is shorthand for "here there be dragons".&nbsp; But we don't have a particularly good idea of what it is, where it is concentrated, or why it would be distributed in any of the hypothesized ways.</p><p>I don't think it is quite like trying to figure out what is in a present without opening it either.&nbsp; We seem to lack the box, let alone the pretty bow.&nbsp; Even being able to exhibit the box would be a giant step forward.&nbsp; Then maybe we could rattle it and weigh it.&nbsp; We are close to wondering if there is a Santa Claus or not.</p><p>You have to admit that it is pretty embarassing to have a conjecture that most of the universe consists of something that we seem to know nothing about.&nbsp; We know a lot more about what it isn't than what it is.&nbsp; The only thing that I am sure of is that the search for an explanation is legitimate science.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
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DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I think it is definitely a place holder.&nbsp; I don't think it is shorthand for "here there be dragons".&nbsp; But we don't have a particularly good idea of what it is, where it is concentrated, or why it would be distributed in any of the hypothesized ways.</p><p>I don't think it is quite like trying to figure out what is in a present without opening it either.&nbsp; We seem to lack the box, let alone the pretty bow.&nbsp; Even being able to exhibit the box would be a giant step forward.&nbsp; Then maybe we could rattle it and weigh it.&nbsp; We are close to wondering if there is a Santa Claus or not.</p><p>You have to admit that it is pretty embarassing to have a conjecture that most of the universe consists of something that we seem to know nothing about.&nbsp; We know a lot more about what it isn't than what it is.&nbsp; The only thing that I am sure of is that the search for an explanation is legitimate science.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
D

DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I think it is definitely a place holder.&nbsp; I don't think it is shorthand for "here there be dragons".&nbsp; But we don't have a particularly good idea of what it is, where it is concentrated, or why it would be distributed in any of the hypothesized ways.</p><p>I don't think it is quite like trying to figure out what is in a present without opening it either.&nbsp; We seem to lack the box, let alone the pretty bow.&nbsp; Even being able to exhibit the box would be a giant step forward.&nbsp; Then maybe we could rattle it and weigh it.&nbsp; We are close to wondering if there is a Santa Claus or not.</p><p>You have to admit that it is pretty embarassing to have a conjecture that most of the universe consists of something that we seem to know nothing about.&nbsp; We know a lot more about what it isn't than what it is.&nbsp; The only thing that I am sure of is that the search for an explanation is legitimate science.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
D

DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.</p><p>I suggest that this thread be moved to either Physics or Ask the Astronomer. <br /></p> <div class="Discussion_UserSignature"> </div>
 
D

DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.</p><p>I suggest that this thread be moved to either Physics or Ask the Astronomer. <br /></p> <div class="Discussion_UserSignature"> </div>
 
D

DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.</p><p>I suggest that this thread be moved to either Physics or Ask the Astronomer. <br /></p> <div class="Discussion_UserSignature"> </div>
 
D

DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, I'd argue that Dark matter isn't just a place holder or a fancy way of saying "here there be dragons".&nbsp; There is a lot of work in the field trying to figure out the 'properties' of dark matter.&nbsp; Mostly it's making lots of observations, lots of models to figure out what sort of matter is required to produce what we see.Basically, it's like trying to figure out what's in a present without opening it.&nbsp; You shake it, listen to it, weigh it, examine the shape of the box, etc, etc, etc, so that you might be able to figure out what it is.&nbsp; Hopefully so that when you do open the present, you go "that makes perfect sense!".&nbsp; Hopefully :) <br />Posted by Saiph</DIV></p><p>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.</p><p>I suggest that this thread be moved to either Physics or Ask the Astronomer. <br /></p> <div class="Discussion_UserSignature"> </div>
 
A

a_lost_packet_

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.I suggest that this thread be moved to either Physics or Ask the Astronomer. Posted by DrRocket</DIV></p><p>I would agree as well. </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>
 
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a_lost_packet_

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.I suggest that this thread be moved to either Physics or Ask the Astronomer. Posted by DrRocket</DIV></p><p>I would agree as well. </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>
 
A

a_lost_packet_

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.I suggest that this thread be moved to either Physics or Ask the Astronomer. Posted by DrRocket</DIV></p><p>I would agree as well. </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>
 
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a_lost_packet_

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I have a somewhat unusual request.&nbsp; The queston of this thread really does relate to real mainstream astrophysics.&nbsp; It does not belong in The Unexplained.I suggest that this thread be moved to either Physics or Ask the Astronomer. Posted by DrRocket</DIV></p><p>I would agree as well. </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>
 
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why06

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<p>I don't think that dark matter in earnest should even be named dark matter. For all that I can figure out is that they don't even know for sure if it is matter. I believe it should be termed "dark force" or "missing gravity".... but thats just me.</p><p>Nevertheless I have heard of some physicist looking for some crazy particle that supposed to play an important role in "quantum chrono-dynamic" or something or the other (which is just a really big word to me). I forgot what the particle was called though and why they think it fits the description of dark matter. </p> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>
 
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why06

Guest
<p>I don't think that dark matter in earnest should even be named dark matter. For all that I can figure out is that they don't even know for sure if it is matter. I believe it should be termed "dark force" or "missing gravity".... but thats just me.</p><p>Nevertheless I have heard of some physicist looking for some crazy particle that supposed to play an important role in "quantum chrono-dynamic" or something or the other (which is just a really big word to me). I forgot what the particle was called though and why they think it fits the description of dark matter. </p> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>
 
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why06

Guest
<p>I don't think that dark matter in earnest should even be named dark matter. For all that I can figure out is that they don't even know for sure if it is matter. I believe it should be termed "dark force" or "missing gravity".... but thats just me.</p><p>Nevertheless I have heard of some physicist looking for some crazy particle that supposed to play an important role in "quantum chrono-dynamic" or something or the other (which is just a really big word to me). I forgot what the particle was called though and why they think it fits the description of dark matter. </p> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>
 
W

why06

Guest
<p>I don't think that dark matter in earnest should even be named dark matter. For all that I can figure out is that they don't even know for sure if it is matter. I believe it should be termed "dark force" or "missing gravity".... but thats just me.</p><p>Nevertheless I have heard of some physicist looking for some crazy particle that supposed to play an important role in "quantum chrono-dynamic" or something or the other (which is just a really big word to me). I forgot what the particle was called though and why they think it fits the description of dark matter. </p> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>
 
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Saiph

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<p>From what I've run into, many astronomers at least claim to know a decent amount about the behavior, properties and distribution of dark matter.&nbsp; That's why I likened it to shaking a present.&nbsp; The only big problem is we don't know the specifics, we don't really know the "why" of it all, and we don't know what objects/particles whatever actually fit the bill.</p><p>&nbsp;</p><p>why06:&nbsp; The reasoning behind the name is pretty solid IMHO.&nbsp; It gives off no light, as a matter of fact it's posited to be completely inert to the electromagnetic forces, thus the "dark".&nbsp; It's also supposed to be a source of gravity, of which the only known source is matter.&nbsp; Thus dark matter.</p><p>Now, there are those who argue that it isn't matter, or just matter, that's causing this extra gravity, but an actual misunderstanding of how gravity works.&nbsp; That's primarily the MOND group DrRocket mentioned.&nbsp; So far, they haven't produced satisfactory models. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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Saiph

Guest
<p>From what I've run into, many astronomers at least claim to know a decent amount about the behavior, properties and distribution of dark matter.&nbsp; That's why I likened it to shaking a present.&nbsp; The only big problem is we don't know the specifics, we don't really know the "why" of it all, and we don't know what objects/particles whatever actually fit the bill.</p><p>&nbsp;</p><p>why06:&nbsp; The reasoning behind the name is pretty solid IMHO.&nbsp; It gives off no light, as a matter of fact it's posited to be completely inert to the electromagnetic forces, thus the "dark".&nbsp; It's also supposed to be a source of gravity, of which the only known source is matter.&nbsp; Thus dark matter.</p><p>Now, there are those who argue that it isn't matter, or just matter, that's causing this extra gravity, but an actual misunderstanding of how gravity works.&nbsp; That's primarily the MOND group DrRocket mentioned.&nbsp; So far, they haven't produced satisfactory models. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
S

Saiph

Guest
<p>From what I've run into, many astronomers at least claim to know a decent amount about the behavior, properties and distribution of dark matter.&nbsp; That's why I likened it to shaking a present.&nbsp; The only big problem is we don't know the specifics, we don't really know the "why" of it all, and we don't know what objects/particles whatever actually fit the bill.</p><p>&nbsp;</p><p>why06:&nbsp; The reasoning behind the name is pretty solid IMHO.&nbsp; It gives off no light, as a matter of fact it's posited to be completely inert to the electromagnetic forces, thus the "dark".&nbsp; It's also supposed to be a source of gravity, of which the only known source is matter.&nbsp; Thus dark matter.</p><p>Now, there are those who argue that it isn't matter, or just matter, that's causing this extra gravity, but an actual misunderstanding of how gravity works.&nbsp; That's primarily the MOND group DrRocket mentioned.&nbsp; So far, they haven't produced satisfactory models. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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Saiph

Guest
<p>From what I've run into, many astronomers at least claim to know a decent amount about the behavior, properties and distribution of dark matter.&nbsp; That's why I likened it to shaking a present.&nbsp; The only big problem is we don't know the specifics, we don't really know the "why" of it all, and we don't know what objects/particles whatever actually fit the bill.</p><p>&nbsp;</p><p>why06:&nbsp; The reasoning behind the name is pretty solid IMHO.&nbsp; It gives off no light, as a matter of fact it's posited to be completely inert to the electromagnetic forces, thus the "dark".&nbsp; It's also supposed to be a source of gravity, of which the only known source is matter.&nbsp; Thus dark matter.</p><p>Now, there are those who argue that it isn't matter, or just matter, that's causing this extra gravity, but an actual misunderstanding of how gravity works.&nbsp; That's primarily the MOND group DrRocket mentioned.&nbsp; So far, they haven't produced satisfactory models. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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UFmbutler

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People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <div class="Discussion_UserSignature"> </div>
 
U

UFmbutler

Guest
People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <div class="Discussion_UserSignature"> </div>
 
U

UFmbutler

Guest
People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <div class="Discussion_UserSignature"> </div>
 
U

UFmbutler

Guest
People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <div class="Discussion_UserSignature"> </div>
 
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DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <br />Posted by UFmbutler</DIV></p><p>I am not surprised that MOND is difficult to extend.&nbsp; Of course you can get it to work for certain things -- it is just a curve fit.&nbsp; I would be personally distressed if it ever goes anywhere,&nbsp; 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.&nbsp; 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.&nbsp; 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.&nbsp; 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 ?&nbsp; But maybe that is the problem.&nbsp; Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces.&nbsp; We have no quantum theory for gravity.&nbsp; If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
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DrRocket

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>People keep bringing up MOND, but it simply does not work.&nbsp; They can get it to work for certain things, but when you try to extend its application it utterly fails.&nbsp; 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.&nbsp; 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.&nbsp; <br />Posted by UFmbutler</DIV></p><p>I am not surprised that MOND is difficult to extend.&nbsp; Of course you can get it to work for certain things -- it is just a curve fit.&nbsp; I would be personally distressed if it ever goes anywhere,&nbsp; 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.&nbsp; 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.&nbsp; 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.&nbsp; 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 ?&nbsp; But maybe that is the problem.&nbsp; Our knowledge of "ordinary" matter is based on quantum theories of the strong, weak and electromagnetic forces.&nbsp; We have no quantum theory for gravity.&nbsp; If dark matter responds only to gravity, it is not amenable to modeling with current quantum field theories.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
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