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I'm a grad student working on cosmology, and while I agree there is a lot of work still to do (we don't know what 95% of the matter that makes up the universe i

I'm a grad student working on cosmology, and while I agree there is a lot of work still to do (we don't know what 95% of the matter that makes up the universe is!), I disagree with a lot of what the author says. > Another recent probe found galaxies inconsistent with the theory of dark matter, which posits this hypothetical substance to be everywhere. We have found evidence of a few galaxies without DM. But most galaxies provide strong evidence for DM - https://en.wikipedia.org/wiki/Galaxy_rotation_curve https://en.wikipedia.org/wiki/Galaxy_rotation_curve > For a crucial function of theories such as dark matter, dark energy and inflation, which each in its own way is tied to the big bang paradigm Big bang was only the accepted paradigm from the 60s (post CMB observations). We have had DE since Einstein in 1917 and DM since Zwicky in the 30s. > Historically, Newton's physical laws made up a theoretical framework that worked for our own solar system with remarkable precision. Both Uranus and Neptune, for example, were discovered through predictions based on Newton's model. But as the scales grew larger, its validity proved limited. Actually some of the earliest evidence for GR came from the orbit of mercury https://en.wikipedia.org/wiki/Tests_of_general_relativity https://en.wikipedia.org/wiki/Tests_of_general_relativity > It is of course entirely plausible that the validity of general relativity breaks down much closer to our own home than at the edge of the hypothetical end of the universe. And if that were the case, today's multilayered theoretical edifice of the big bang paradigm would turn out to be a confusing mix of fictional beasts invented to uphold the model This is something that people are working on! This is a hypothesized source of DE. However, disproving GR does nothing to disprove the big bang. > Today's space telescopes provide no direct view of anything I have no idea what that means. They literally observe the sky... There is a ton of work to do: finding what DM is, finding what DE is, finding whether GR is correct. But I'm not sold that the author knows what he is talking about...

scrozart 7y ago
> > Today's space telescopes provide no direct view of anything > I have no idea what that means. They literally observe the sky... Seriously! At this point they're just spitballing.
- astro123 7y ago
  I was maybe a bit too cavalier here. I think I understand what the author means - the data that they gather is understood in the context of the model that we think is best. But, it isn't as if cosmologists are rigidly holding to the model. Here's a paper looking at extensions to lambda CDM https://arxiv.org/abs/1512.05356 https://arxiv.org/abs/1512.05356. As I mentioned, changing GR is being looked at as an alternative to DE http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen/koyama-1.pdf http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen... People aren't challenging some things though - I don't think anyone is seriously working on cosmologies that don't include a big bang, because without one I can't imagine how you explain the CMB.
  - eaim 7y ago
    Sorry but I’d have to disagree: There are plenty of people working on cosmologies that don’t include the Big Bang, or that do include it but only as one facet of a larger theoretical framework. As for not being able to imagine how you explain the CMB without the Big Bang, well, there are plenty of good arguments being made here that put to paid that “limitation.” As well, think of the Michelson-Morley experiment. In that era, no one could imagine how light could propagate through space without the presence of a medium permeating that space. I’ll venture one step further. Dark Matter is to current cosmology what the aether was to 19th century cosmology.
astro123 7y ago
For some reason edits are silently failing, but an addendum to > Big bang was only the accepted paradigm from the 60s (post CMB observations). We have had DE since Einstein in 1917 and DM since Zwicky in the 30s. Admittedly the DE from Einstein is for very different reasons than the DE today, but we again had the big bang and no DE from the 60s until the 90s (observations from https://en.wikipedia.org/wiki/Supernova_Cosmology_Project https://en.wikipedia.org/wiki/Supernova_Cosmology_Project) so they don't go hand in hand.
FakeComments 7y ago
> > Today's space telescopes provide no direct view of anything > I have no idea what that means. They literally observe the sky... They mean you can’t look into the telescope and see the object, eg like going into my backyard and observing Mars or Venus, that you need to do elaborate post processing to resolve the target object from other collected signals and shift it into a visible form. This is contrasted with early astronomy, where you could literally just look at objects. I don’t know that this is a deeply significant point, but it’s at least understandable: if it’s not something you can look at, then you might be assuming your theory to interpret the evidence which supports your theory — that you’ve just begged the question. I think the comment speaks to the breakdown in science education, but it’s a valid observation about failures in complex human endeavors.
petschge 7y ago
The fact that SOME galaxies are inconsistent with the theory of Dark Matter actually strengthens that theory. If the difference in rotation curves, the usual signature of dark matter at the galaxy level, from what GR predicts based on the mass of luminous objects was due to a modification in the way gravity works, then that should apply to ALL galaxies. Modified Newtowian Dynamics (MOND) (or the relativistic TeVeS models) should work the same for all galaxies, at least all of roughly same mass and same depth of the gravitational potential. The fact that we can find similar sized and aged galaxies that behave like they have different amounts of dark matter is therefore NOT caused by the way gravity works. The next best explanation is that most galaxies contain dark matter, but some loose it through their evolution history, e.g. due to interaction with other galaxies.
- whatshisface 7y ago
  To be clear, they're not inconsistent with the theory of dark matter, they're inconsistent with those galaxies specifically having dark matter. The author was wording that in a confusing way.
  - Koshkin 7y ago
    The way I understood it, they are not inconsistent with anything, they just happen to have no DM in them.
  - petschge 7y ago
    That's right they are inconsistent with the combination of 1.) dark matter is the correct theory and 2.) they have the usual amount of dark matter for a galaxy of that size. Surprisingly this is does not make the theory of dark matter (#1) less likely, but actually makes it more likely. Because the alternative is #1b "gravity works differently than we think". But that would have to hold for all galaxies.
  - slowmovintarget 7y ago
    To be even more clear, "dark matter" isn't a theory. It is a name for something we need theories about. I wish the article had made that apparent.
scott_s 7y ago
I found the authors' points about reports from the past several months disingenuous, since he's advertising a book that was clearly written and edited well before those announcements. It's valid to talk about those points in the context of arguments from the book, but leading with those points implies those arguments are a result of those points.
mnl 7y ago
I've rarely seen more spectacular agreements with a theory than those of a Lambda-CDM fit of Planck's 2015 data. That can't be wrong (but as I've never worked on it, this statement is just some guy's personal impression based on his physics instinct). What's your take on those results?

scrozart 7y ago

> > Today's space telescopes provide no direct view of anything > I have no idea what that means. They literally observe the sky... Seriously! At this point they're just spitballing.

astro123 7y ago
I was maybe a bit too cavalier here. I think I understand what the author means - the data that they gather is understood in the context of the model that we think is best. But, it isn't as if cosmologists are rigidly holding to the model. Here's a paper looking at extensions to lambda CDM https://arxiv.org/abs/1512.05356 https://arxiv.org/abs/1512.05356. As I mentioned, changing GR is being looked at as an alternative to DE http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen/koyama-1.pdf http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen... People aren't challenging some things though - I don't think anyone is seriously working on cosmologies that don't include a big bang, because without one I can't imagine how you explain the CMB.
- eaim 7y ago
  Sorry but I’d have to disagree: There are plenty of people working on cosmologies that don’t include the Big Bang, or that do include it but only as one facet of a larger theoretical framework. As for not being able to imagine how you explain the CMB without the Big Bang, well, there are plenty of good arguments being made here that put to paid that “limitation.” As well, think of the Michelson-Morley experiment. In that era, no one could imagine how light could propagate through space without the presence of a medium permeating that space. I’ll venture one step further. Dark Matter is to current cosmology what the aether was to 19th century cosmology.

astro123 7y ago

For some reason edits are silently failing, but an addendum to > Big bang was only the accepted paradigm from the 60s (post CMB observations). We have had DE since Einstein in 1917 and DM since Zwicky in the 30s. Admittedly the DE from Einstein is for very different reasons than the DE today, but we again had the big bang and no DE from the 60s until the 90s (observations from https://en.wikipedia.org/wiki/Supernova_Cosmology_Project https://en.wikipedia.org/wiki/Supernova_Cosmology_Project) so they don't go hand in hand.

FakeComments 7y ago

> > Today's space telescopes provide no direct view of anything > I have no idea what that means. They literally observe the sky... They mean you can’t look into the telescope and see the object, eg like going into my backyard and observing Mars or Venus, that you need to do elaborate post processing to resolve the target object from other collected signals and shift it into a visible form. This is contrasted with early astronomy, where you could literally just look at objects. I don’t know that this is a deeply significant point, but it’s at least understandable: if it’s not something you can look at, then you might be assuming your theory to interpret the evidence which supports your theory — that you’ve just begged the question. I think the comment speaks to the breakdown in science education, but it’s a valid observation about failures in complex human endeavors.

petschge 7y ago

The fact that SOME galaxies are inconsistent with the theory of Dark Matter actually strengthens that theory. If the difference in rotation curves, the usual signature of dark matter at the galaxy level, from what GR predicts based on the mass of luminous objects was due to a modification in the way gravity works, then that should apply to ALL galaxies. Modified Newtowian Dynamics (MOND) (or the relativistic TeVeS models) should work the same for all galaxies, at least all of roughly same mass and same depth of the gravitational potential. The fact that we can find similar sized and aged galaxies that behave like they have different amounts of dark matter is therefore NOT caused by the way gravity works. The next best explanation is that most galaxies contain dark matter, but some loose it through their evolution history, e.g. due to interaction with other galaxies.

whatshisface 7y ago
To be clear, they're not inconsistent with the theory of dark matter, they're inconsistent with those galaxies specifically having dark matter. The author was wording that in a confusing way.
- Koshkin 7y ago
  The way I understood it, they are not inconsistent with anything, they just happen to have no DM in them.
- petschge 7y ago
  That's right they are inconsistent with the combination of 1.) dark matter is the correct theory and 2.) they have the usual amount of dark matter for a galaxy of that size. Surprisingly this is does not make the theory of dark matter (#1) less likely, but actually makes it more likely. Because the alternative is #1b "gravity works differently than we think". But that would have to hold for all galaxies.
- slowmovintarget 7y ago
  To be even more clear, "dark matter" isn't a theory. It is a name for something we need theories about. I wish the article had made that apparent.

scott_s 7y ago

I found the authors' points about reports from the past several months disingenuous, since he's advertising a book that was clearly written and edited well before those announcements. It's valid to talk about those points in the context of arguments from the book, but leading with those points implies those arguments are a result of those points.

mnl 7y ago

I've rarely seen more spectacular agreements with a theory than those of a Lambda-CDM fit of Planck's 2015 data. That can't be wrong (but as I've never worked on it, this statement is just some guy's personal impression based on his physics instinct). What's your take on those results?