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The Reason We Haven’t Directly Detected Dark Matter

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Re: The Reason We Haven’t Directly Detected Dark Matter

#191

Post by wheels »

jpfed wrote: post #85
gmjoe wrote: post #63

Earlier quoted context omitted.

Agreed 100%. Indeed, this is one of the best articles I've come across which covers several of the reasons we believe dark matter exists, as opposed to us just needing to modify the theory of gravity. For whatever reason, dark matter seems to repeatedly rub people the wrong way today, more so than any other scientific concept I can think of. I actually wonder if it's something psychological -- if the universe is only…

I think one reason may be that people are used to the "completeness" of physics; it's the science that people seem historically most ready to declare "done", and it does explain a lot very well. This may make it particularly unsettling to learn about this vast frontier of ignorance.

Really? Who are these people that consider physics to be complete? I'm kind of skeptical that there's a large body of folks that know enough about physics to even ponder its completeness, but who also are unaware of the discrepancies between general relativity and quantum mechanics.

Re: The Reason We Haven’t Directly Detected Dark Matter

#192

Post by acqq »

jccalhoun wrote: post #126
gmjoe wrote: post #63

Earlier quoted context omitted.

Agreed 100%. Indeed, this is one of the best articles I've come across which covers several of the reasons we believe dark matter exists, as opposed to us just needing to modify the theory of gravity. For whatever reason, dark matter seems to repeatedly rub people the wrong way today, more so than any other scientific concept I can think of. I actually wonder if it's something psychological -- if the universe is only…

>For whatever reason, dark matter seems to repeatedly rub people the wrong way today, more so than any other scientific concept I can think of. I think that it is because it is so hard to understand. You can't see it or touch it but it is supposed to make up the majority of mater in the universe. So what is it then? For a lot of people that's a hard thing to get and it would be easier if the answer was something we u…

> Of course dark matter "deniers" don't have the same religious convictions of creationists.

Can you support that "of course"? I'm not so sure that there is no correlation. E.g. it is known that the same persons who tried to convince us that the "smoking is not dangerous" try to convince us that the "global warming doesn't exist, or at best it's beneficial." There are definitely the circles that immediately welcome and use any way to raise the doubt in the relevance of the majority of the scientific claims. It is intentional, it is supported by a lot of money, and it comes not only from one political direction. It is complex, it's not only a single ideology or a single religious group, but there are multiple correlations.

See the books: "The War on Science" by Shawn Otto and "Merchants of Doubt" by Oreskes and Conway.

Re: The Reason We Haven’t Directly Detected Dark Matter

#193

Post by amluto »

walrus1066 wrote: post #186
dogma1138 wrote: post #168

Earlier quoted context omitted.

I think you misunderstand the threads. Dark Matter isn’t a thing it’s a place holder it has many candidates some more probable than others it might be that there is only one class of dark matter it might be that there are multiple classes of dark matter. It might be that all the dark matter will be new forms of matter it might be that some or all of it will end up being baryonic matter. It also might be that we won’t…

It can't be baryonic matter, because baryons are made of quarks, which carry electric charge, and therefore interact with light, xrays etc. But we don't see dark matter scattering or absorbing the x-rays & whatnot emitted by stars, nebulae etc. Hence the 'dark' in dark matter. So it has to be made of particles which have no electric charge. The only such longlived particle we know of is the neutrino, but these guys t…

Neutrons are uncharged baryons. The problems with baryonic dark matter have little to do with the charge of quarks.

Re: The Reason We Haven’t Directly Detected Dark Matter

#194

Post by GeekyBear »

When your observations of the universe don't match up with what your theory predicts, it may just be possible that like Issac Newton, you just haven't gotten everything figured out yet.

There may just be more going on in the universe over the largest scales than you've figured out so far, and we're waiting for an Einstein to come along to add to what we already know.

Which is not to say that our inability to detect most of the matter in the universe means that dark matter is impossible.

It just seems odd to write off the other possibility given the history of science.

Re: The Reason We Haven’t Directly Detected Dark Matter

#195

Post by CydeWeys »

bordercases wrote: post #118
CydeWeys wrote: post #93

Earlier quoted context omitted.

Gravity behaving like that would be a lot weirder than there simply being some types of mass we aren't able to detect yet. Physics has had a long history of predicting particles that hadn't been detected yet, and then actually going out and finding them. See neutrinos, the Higgs boson, etc. General relativity being wrong would be waaaay weirder.

> General relativity being wrong would be waaaay weirder. It only got empirical confirmation recently, it should still be open to disconfirmation.

That's a common urban legend. General relativity has been tested and confirmed many, many, many times, dating back to soon after it was first proposed.

Re: The Reason We Haven’t Directly Detected Dark Matter

#196

Post by dogma1138 »

gmjoe wrote: post #187
dogma1138 wrote: post #182

Earlier quoted context omitted.

>It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. No it's not known, it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. Only Siths deal in absolutes. >Only for completely useless definitions of the “concensus.” Do you have a more useful definition of consensus for th…

By definition it's not baryonic, because we aren't detecting it and we would be detecting it if it were. "Dark" in this context means, in and of itself, non-baryonic. And please don't bring silly Star Wars references here, they don't help and this particular one is basically offensive. HN isn't reddit.

No Dark didn’t mean non baryonic at first when DM was conceived and still does not mean that today dark was just that dark as it wasn’t emitting any light we could detect which is why CBM, rogue brown dwarfs and primordial black holes were all a candidate for dark matter at some point.

And thanks for the advice I’ll keep using my SW references when they are fitting and this one is fitting indeed.

Here is another one just for you began the dark matter war has.

Re: The Reason We Haven’t Directly Detected Dark Matter

#197

Post by dogma1138 »

acqq wrote: post #189
dogma1138 wrote: post #182

Earlier quoted context omitted.

>It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. No it's not known, it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. Only Siths deal in absolutes. >Only for completely useless definitions of the “concensus.” Do you have a more useful definition of consensus for th…

> it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. That "highly" in "highly unlikely" is the key here, that highly is "immensely huge" e.g.: http://iopscience.iop.org/article/10.3847/2041-8205/824/2/L3... "While future observations will determine the strength of the constraints from Eri II, existing data from Eri II and fro…

I think you have very big problem with reading comprehension and you are strawmaning.

At no point have I said that MACHO, cold baryionic matter or any of the other baryionic candidates are sufficient to explain dark matter, the point is that while we have more and less likely candidates we are no where closer today at singling our a good candidate that we can back up via observations or experiments than we were at the 70s.

Dark Matter cannot be explained by elimination alone there is absolutely no single consensus on what it actually is or what the best candidate should be it doesn’t have to be 100% but it’s not 80%, or 60% either.

But sure go ahead and continue to argue without actually adding anything of value.

Re: The Reason We Haven’t Directly Detected Dark Matter

#198

Post by mnl »

krapp wrote: post #56

I like how we have an article explaining the rationale behind dark matter and the scientific principles that lead to the conclusion that it exists, but most of the threads here are simple declarations that no, they must all simply be wrong or not considering some simple alternative. Can people maybe, just maybe not assume that scientists are idiots or, as once dead commenter puts it, charlatans? If you disagree with…

This happens all the time here when it comes to physics. Other greatest hits are bickering endlessly about interpretations of QM deeming unacceptable the shut-up-and-calculate approach that 90% of physicists have no problem with and to a minor extent the failure of the LHC to make up new physics ex nihilo.

People should be able to recognize they haven't put the effort to learn the basics of what they're talking about and that maybe there are very good reasons for all this they can't be aware of because of it and should ask about... and start from there.

Re: The Reason We Haven’t Directly Detected Dark Matter

#199

Post by dogma1138 »

walrus1066 wrote: post #188
dogma1138 wrote: post #180

Earlier quoted context omitted.

WIMPs are just a whole class of placeholder particles, there is no consensus on anything currently everyone has their own pet theory or theories depending on their field.

Ultimately this is because we can't yet prove by experiment, which theory is the correct one. We need to observe these guys being produced in a particle collider to definitively know what dark matter is made of.

It’s not just that say we find wimps in the lab we need to have some sort of a model that would explain how they are or were produced in the universe and more importantly that they were produced in the correct ratio to be the single explanation for dark matter.

It’s quite possible that we will find WIMPs in a particle accelerator but then be stuck with the fact that at best they’ll only account for 3% of the dark matter we observe and then it’s again back to the drawing board.

Re: The Reason We Haven’t Directly Detected Dark Matter

#200

Post by dogma1138 »

walrus1066 wrote: post #186
dogma1138 wrote: post #168

Earlier quoted context omitted.

I think you misunderstand the threads. Dark Matter isn’t a thing it’s a place holder it has many candidates some more probable than others it might be that there is only one class of dark matter it might be that there are multiple classes of dark matter. It might be that all the dark matter will be new forms of matter it might be that some or all of it will end up being baryonic matter. It also might be that we won’t…

It can't be baryonic matter, because baryons are made of quarks, which carry electric charge, and therefore interact with light, xrays etc. But we don't see dark matter scattering or absorbing the x-rays & whatnot emitted by stars, nebulae etc. Hence the 'dark' in dark matter. So it has to be made of particles which have no electric charge. The only such longlived particle we know of is the neutrino, but these guys t…

Cold baryonic matter, MACHOs, primordial black holes etc were all candidates for dark matter at some point, yes they aren’t likely candidates at this point because we have much better telescopes and more complete surveys but the search for DM isn’t a process of elimination you can’t prove what is it by eliminating possible candidates you can only show where we might more likely to find a good candidate.
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