5 ms·

Same reason cars stop when they hit a brick wall. Most of the mass of galaxies isn't in their stars (which, for the most part, keep moving with the dark matter

Same reason cars stop when they hit a brick wall. Most of the mass of galaxies isn't in their stars (which, for the most part, keep moving with the dark matter) it's in gas clouds and dust formations. When two galaxies collide, the gas and dust effectively halts. What we see when galaxies collide is that most of the mass of the galaxies move straight through each other without appreciably decelerating. And most of the matter, the gas clouds and star forming regions, halt in the middle. MOND was taken seriously as a theory from its inception in the '70s through the end of the 20th century, but because of the bullet cluster, it is effectively dead. MOND is falsified by observational evidence. For this article to discuss MOND so thoroughly, but not mention the bullet cluster once... It doesn't pass the smell test. This is pseudo-scientific trash. There's other evidence against MOND and various alternative-gravity models (there are several of them, it's a large umbrella) but most of them do a very poor job at explaining the edge cases, such as the bullet cluster and ultra diffuse galaxies. Some ultra diffuse galaxies have a conspicuous absence of gravitational lensing and stars which orbit extraordinarily slowly; ie, they have very little dark matter. If the explanation for dark matter was that we had the laws of physics wrong, the newly revised gravitational theories should apply equally well to these galaxies- which they don't.

manquer 6y ago
While the article is perhaps not written as well it could have been, alternative gravity is probably indeed bust, the point that other theories need to be funded and studied is valid. it is not a either/or scenario. The argument the article makes is that just because emergent gravity or many alternative candidates potentially cannot explain all of evidence that dark matter can , does not mean it should be thrown out completely and rejected, it could be still funded and studied to see if it can explain some of it. The real issue is given the way modern academic funding works we have been tending more and more towards narrower research with main line theories and lesser riskier proposals perhaps being incentivised. This is not just limited not dark matter , this phenomenon is evident in string theory research and many other fields as well.
- narrator 6y ago
  How about we fund somebody like a George Church to just a have a lab and pursue whatever he feels like in cosmology instead of such a narrow "school of thought" picked by a donor?
  - rob74 6y ago
    Maybe, if the donor feels like it... I mean, even if dark matter is the theory most likely to be correct, it's not as if further research along that path will yield any kind of monetary "return on investment" in our lifetime, so researching alternative theories is no more or less a waste of money :)
- Misdicorl 6y ago
  No, the conclusions are not valid. This person doesn't know the most important experimental results in the field, doesn't understand why modified gravity is both theoretically and experimentally unsound, doesn't understand that dark matter research is already not a mono culture, doesn't understand that detailed investigations of gravity potentially diverging from the inverse square law already exist and that new studies are planned. This is the equivalent of someone reading some nasty things about C and claiming we need to investigate python for kernel development.
- Misdicorl 6y ago
  As an aside, you've put the cart before the horse here. When you have multiple competing theories, you don't study them separately. You design experiments which will (hopefully) measure different results depending on which theory is true. This is exactly what is happening in cosmology. The experiments have ruled out MOND and their like. New results will rule out more dark matter candidates. Surprising results will lead to new theories.
autokad 6y ago
the problem is, so much is based on circular assumptions of theories, most of which is bullocks. cosmology was convinced that the universe is homogeneous and isotropic (the universe is about the same everywhere). they we learn that the rotation of galaxies is not random... the universe is flat, and then its not. the expansion of the universe is the same everywhere... and then it might not be... we had one way of measuring the age of the universe with method a, and another with method b, and they use to have overlap. and now they dont... https://youtu.be/cnn_5YMpo3Q?t=876 https://youtu.be/cnn_5YMpo3Q?t=876 Honestly, if we agreed that we know 10% of what the heck is going on out there, that is probably being way too optimistic. so to blindly parroting "that's pseudoscience' to cast doubt on something that hasn't been observed in 60 years despite supposed to be representing the majority of the universe... that feels like religion, not science
- throwaway_pdp09 6y ago
  > the problem is, so much is based on circular assumptions of theories What specific circular assumptions are you suggesting?
- throwaway2048 6y ago
  OP isn't calling the concept of MOND or alternate gravity theories pseudo-scientific, they are calling the article pseudo-scientific.
- bad_user 6y ago
  Such opinions show a lack of understanding for how science works. Yes, scientists come up with hypotheses all the time, with the only requirement being for them to be falsifiable. And the theories themselves can't be proven as true, since this isn't math but empirical science, but we can get an idea about how well they predict natural phenomena and we can disprove them by empirical evidence, observations that show these theories don't predict the universe well. Scientific theories are a dime a dozen and in the presence of empirical evidence that falsifies them, we should consider such theories as falsified and move on. When people continue believing in theories that are non-falsifiable or that have been falsified, that's pseudo-science.
roystonvassey 6y ago
Off-topic, would you have any recommendations for introductory reading on these topics? I’d be very interested to learn more
loxias 6y ago
Hi, you sound like you know what you're talking about. Can you elaborate with more details (my "reading comprehension" is such that I enjoy/comprehend academic papers more than watered down (and sometimes wrong) "pop-science" simplifications) about the counter-evidence against MOND? You've given me some great topics to google search for, and it's much appreciated! (somehow I missed hearing about the bullet cluster. reading about it now... including the rebuttal: https://web.archive.org/web/20160721044735/http://www.astro.umd.edu/~ssm/mond/moti_bullet.html https://web.archive.org/web/20160721044735/http://www.astro....) Can you perhaps drop a few more links to things I can dig into that provide counter evidence for MOND? MOND has been sort of a ... romantic crush ... of mine since I first learned of it 20 years ago. :)
lostmsu 6y ago
I think the fact, that most of the galaxy mass is in dust and gas clouds is the most important bit here I didn't know.

manquer 6y ago

While the article is perhaps not written as well it could have been, alternative gravity is probably indeed bust, the point that other theories need to be funded and studied is valid. it is not a either/or scenario. The argument the article makes is that just because emergent gravity or many alternative candidates potentially cannot explain all of evidence that dark matter can , does not mean it should be thrown out completely and rejected, it could be still funded and studied to see if it can explain some of it. The real issue is given the way modern academic funding works we have been tending more and more towards narrower research with main line theories and lesser riskier proposals perhaps being incentivised. This is not just limited not dark matter , this phenomenon is evident in string theory research and many other fields as well.

narrator 6y ago
How about we fund somebody like a George Church to just a have a lab and pursue whatever he feels like in cosmology instead of such a narrow "school of thought" picked by a donor?
- rob74 6y ago
  Maybe, if the donor feels like it... I mean, even if dark matter is the theory most likely to be correct, it's not as if further research along that path will yield any kind of monetary "return on investment" in our lifetime, so researching alternative theories is no more or less a waste of money :)
Misdicorl 6y ago
No, the conclusions are not valid. This person doesn't know the most important experimental results in the field, doesn't understand why modified gravity is both theoretically and experimentally unsound, doesn't understand that dark matter research is already not a mono culture, doesn't understand that detailed investigations of gravity potentially diverging from the inverse square law already exist and that new studies are planned. This is the equivalent of someone reading some nasty things about C and claiming we need to investigate python for kernel development.
Misdicorl 6y ago
As an aside, you've put the cart before the horse here. When you have multiple competing theories, you don't study them separately. You design experiments which will (hopefully) measure different results depending on which theory is true. This is exactly what is happening in cosmology. The experiments have ruled out MOND and their like. New results will rule out more dark matter candidates. Surprising results will lead to new theories.

autokad 6y ago

the problem is, so much is based on circular assumptions of theories, most of which is bullocks. cosmology was convinced that the universe is homogeneous and isotropic (the universe is about the same everywhere). they we learn that the rotation of galaxies is not random... the universe is flat, and then its not. the expansion of the universe is the same everywhere... and then it might not be... we had one way of measuring the age of the universe with method a, and another with method b, and they use to have overlap. and now they dont... https://youtu.be/cnn_5YMpo3Q?t=876 https://youtu.be/cnn_5YMpo3Q?t=876 Honestly, if we agreed that we know 10% of what the heck is going on out there, that is probably being way too optimistic. so to blindly parroting "that's pseudoscience' to cast doubt on something that hasn't been observed in 60 years despite supposed to be representing the majority of the universe... that feels like religion, not science

throwaway_pdp09 6y ago
> the problem is, so much is based on circular assumptions of theories What specific circular assumptions are you suggesting?
throwaway2048 6y ago
OP isn't calling the concept of MOND or alternate gravity theories pseudo-scientific, they are calling the article pseudo-scientific.
bad_user 6y ago
Such opinions show a lack of understanding for how science works. Yes, scientists come up with hypotheses all the time, with the only requirement being for them to be falsifiable. And the theories themselves can't be proven as true, since this isn't math but empirical science, but we can get an idea about how well they predict natural phenomena and we can disprove them by empirical evidence, observations that show these theories don't predict the universe well. Scientific theories are a dime a dozen and in the presence of empirical evidence that falsifies them, we should consider such theories as falsified and move on. When people continue believing in theories that are non-falsifiable or that have been falsified, that's pseudo-science.

roystonvassey 6y ago

Off-topic, would you have any recommendations for introductory reading on these topics? I’d be very interested to learn more

loxias 6y ago

Hi, you sound like you know what you're talking about. Can you elaborate with more details (my "reading comprehension" is such that I enjoy/comprehend academic papers more than watered down (and sometimes wrong) "pop-science" simplifications) about the counter-evidence against MOND? You've given me some great topics to google search for, and it's much appreciated! (somehow I missed hearing about the bullet cluster. reading about it now... including the rebuttal: https://web.archive.org/web/20160721044735/http://www.astro.umd.edu/~ssm/mond/moti_bullet.html https://web.archive.org/web/20160721044735/http://www.astro....) Can you perhaps drop a few more links to things I can dig into that provide counter evidence for MOND? MOND has been sort of a ... romantic crush ... of mine since I first learned of it 20 years ago. :)

lostmsu 6y ago

I think the fact, that most of the galaxy mass is in dust and gas clouds is the most important bit here I didn't know.