7 ms·

Trust me this is a straw man picking at a hole of a yet incomplete theory to claim the whole deck of cards is invalid. AFAIK none of these alternatives offer a

by rob_c 4y ago

Trust me this is a straw man picking at a hole of a yet incomplete theory to claim the whole deck of cards is invalid. AFAIK none of these alternatives offer a serious explanation of gravitational lensing for instance (yet, I'm happy for someone to make a theoretical breakthrough that explains away the need for an unknown new particle, but that just opens more questions around CP violation and so on)

pdonis 4y ago
> Trust me Why? Who made you an infallible authority? > none of these alternatives The basic point I described is not proposing an alternative to dark matter, and I'm not asking for a refutation of Kroupa's well-known preference for alternative gravity theories. I'm just pointing out that Kroupa has described a prediction of the dark matter hypothesis that does not appear to match observations. I'm wondering if any proponent of the dark matter hypothesis has a counter argument to this: either an explanation of why the dark matter hypothesis doesn't make the prediction Kroupa is describing, or an explanation of why that prediction does match observations after all. This seems to me to be a perfectly reasonable question that does not require any discussion of alternative theories at all.
- rob_c 4y ago
  > Who made you an infallible authority? I'm not infallible but I do have a PhD in the study of CPV in particle physics so I understand this at a level enough to pass a doctoral viva. Alternate gravity theories struggle with gravitational lensing. This is a proven observable optical phenomena in the study of the universe. Kroupa is still trying to explain the rotational differences between observation and "normal" Newtonian/Einstein gravity. This is colloquially referred to as Dark Matter. A gravitational (matter like) effect, which doesn't interact optically via standard EM as we can see the galaxies and stars. Hence the name Dark Matter.
  - pdonis 4y ago
    > Alternate gravity theories Are not what I'm asking about here. I know Kroupa pushes them, but that's not the part of Kroupa's work that I'm asking about. > Kroupa is still trying to explain the rotational differences between observation and "normal" Newtonian/Einstein gravity. Not in the specific item I'm asking about. In that specific item, he's not talking about any alternative theories of gravity at all. He's pointing out what he claims is a conflict between the predictions of the dark matter hypothesis and actual observations. I've already explained what a counter argument to that would look like. Do you have one?
    - rob_c 4y ago
      Unfortunately you are getting a little crossed from your perspective. You're asking a question that to experts is structured oddly because you can't disentangle things you're trying to separate. I'll try to explain. Again dark matter is an attempt to explain a collection of observations that don't match current accepted theoretical models. There "classical dark matter hypothesises" is just that. That these observations can be explained by a quantizable matter candidate of some form with some yet to be determined properties. The only non particle descriptions of "dark matter phenomena" is a modified gravity framework. These attempt to address the "classical dark matter phenomena" whilst disentangling it from the "CPV phenomena". This is fine but breaks the big bang model at the stage of baryogenesis (matter formation from pure energy). There is the possibility that you can explain "classical dark matter phenomena" without demanding it also be responsible for CPV. However, if you do that the CPV step of the big bang model demands additional particle candidates which then raises the problem of what do they look like and where are they and do they interact with the Higgs field and therefore have mass. There are no counter arguments to "classical dark matter phenomena" because they are just that. Observed natural phenomena which do not fit into our current understanding of the universe. A "complete dark matter theory" tends to explain CPV+DM. These again don't make many testable predictions other than a (potentially TeV scale) weekly interacting particle candidate. So the testable prediction is that a dark matter candidate exists and we can observe it. > I've already explained what a counter argument to that would look like. Do you have one? I'll choose to read that in a relaxed manner, albeit it's a bit direct. There is no counter argument to natural phenomena. The main 2 theories are that dark matter particles exist and we can find them or we can't. MOND et al make few predictions and struggle to observe defined "gravitational phenomena", hence why there is little interest in them. There are differences between DM particle models but almost all agree that the major premise is that we might/should be able to see certain particle types given how they interact.

by rob_c 4y ago

pdonis 4y ago

> Trust me Why? Who made you an infallible authority? > none of these alternatives The basic point I described is not proposing an alternative to dark matter, and I'm not asking for a refutation of Kroupa's well-known preference for alternative gravity theories. I'm just pointing out that Kroupa has described a prediction of the dark matter hypothesis that does not appear to match observations. I'm wondering if any proponent of the dark matter hypothesis has a counter argument to this: either an explanation of why the dark matter hypothesis doesn't make the prediction Kroupa is describing, or an explanation of why that prediction does match observations after all. This seems to me to be a perfectly reasonable question that does not require any discussion of alternative theories at all.

rob_c 4y ago
> Who made you an infallible authority? I'm not infallible but I do have a PhD in the study of CPV in particle physics so I understand this at a level enough to pass a doctoral viva. Alternate gravity theories struggle with gravitational lensing. This is a proven observable optical phenomena in the study of the universe. Kroupa is still trying to explain the rotational differences between observation and "normal" Newtonian/Einstein gravity. This is colloquially referred to as Dark Matter. A gravitational (matter like) effect, which doesn't interact optically via standard EM as we can see the galaxies and stars. Hence the name Dark Matter.
- pdonis 4y ago
  > Alternate gravity theories Are not what I'm asking about here. I know Kroupa pushes them, but that's not the part of Kroupa's work that I'm asking about. > Kroupa is still trying to explain the rotational differences between observation and "normal" Newtonian/Einstein gravity. Not in the specific item I'm asking about. In that specific item, he's not talking about any alternative theories of gravity at all. He's pointing out what he claims is a conflict between the predictions of the dark matter hypothesis and actual observations. I've already explained what a counter argument to that would look like. Do you have one?
  - rob_c 4y ago
    Unfortunately you are getting a little crossed from your perspective. You're asking a question that to experts is structured oddly because you can't disentangle things you're trying to separate. I'll try to explain. Again dark matter is an attempt to explain a collection of observations that don't match current accepted theoretical models. There "classical dark matter hypothesises" is just that. That these observations can be explained by a quantizable matter candidate of some form with some yet to be determined properties. The only non particle descriptions of "dark matter phenomena" is a modified gravity framework. These attempt to address the "classical dark matter phenomena" whilst disentangling it from the "CPV phenomena". This is fine but breaks the big bang model at the stage of baryogenesis (matter formation from pure energy). There is the possibility that you can explain "classical dark matter phenomena" without demanding it also be responsible for CPV. However, if you do that the CPV step of the big bang model demands additional particle candidates which then raises the problem of what do they look like and where are they and do they interact with the Higgs field and therefore have mass. There are no counter arguments to "classical dark matter phenomena" because they are just that. Observed natural phenomena which do not fit into our current understanding of the universe. A "complete dark matter theory" tends to explain CPV+DM. These again don't make many testable predictions other than a (potentially TeV scale) weekly interacting particle candidate. So the testable prediction is that a dark matter candidate exists and we can observe it. > I've already explained what a counter argument to that would look like. Do you have one? I'll choose to read that in a relaxed manner, albeit it's a bit direct. There is no counter argument to natural phenomena. The main 2 theories are that dark matter particles exist and we can find them or we can't. MOND et al make few predictions and struggle to observe defined "gravitational phenomena", hence why there is little interest in them. There are differences between DM particle models but almost all agree that the major premise is that we might/should be able to see certain particle types given how they interact.