The Reason We Haven’t Directly Detected Dark Matter • Hacker News Board

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

#181

Post by delecti » Sat, Oct 13, 2018, 6:52 PM UTC

gbrown wrote: post #86

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…

People somehow feel uniquely qualified to speculate wildly about theoretical physics. It's bizarre in a forum full of technical-minded people.

I don't know what it is about us technically minded people that makes us so confident in our knowledge in so many fields like that (note that I'm including myself in that generalization). It seems to go beyond your garden variety Dunning–Kruger effect.

My personal supposition is that most people don't know very much if anything about most subjects, and tech people tend to know a bit more than that quite low average (though still not anywhere near expert level) in an above average number of subjects, and that "novice polymath" status amplifies the Dunning-Kruger effect. Of course it's entirely possible that demonstrating the Dunning-Kruger effect by even thinking we tend to have an above average exposure to an above average number of fields.

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

#182

Post by dogma1138 » Sat, Oct 13, 2018, 6:54 PM UTC

acqq wrote: post #173

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 might be that some or all of it will end up being baryonic matter It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. > There isn’t a consensus amongst scientists Only for completely useless definitions of the “concensus.”

>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 this matter? if so please share it.

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

#183

Post by vbezhenar » Sat, Oct 13, 2018, 6:58 PM UTC

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…

That's why it's dangerous to pretend like really complex things actually are not that complex. Laymen think that they understand something about it and they are starting to have opinion which usually is wrong, because complex things are actually complex and opinion based on limited interpretation is wrong.

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

#184

Post by marcosdumay » Sat, Oct 13, 2018, 7:01 PM UTC

cygx wrote: post #166

TangoTrotFox wrote: post #159

Earlier quoted context omitted.

That's really the problem here though. You cannot falsify dark matter, and you cannot prove a negative. Imagine I say there is a 5 headed green deer that weighs 2000 pounds and can speak Gaelic, but it's really good at avoiding being spotted - so good in fact that you can even look at right at it and might not see it. And you can even touch it and not even know you're touching it! What would you could consider an exh…

The idea of non-visible matter as a fix for stellar motion dates back to the 19th century, when our knowledge about the cosmos was far more limited (remember, we only learned about other galaxies in the 1920s - it post-dates general relativity!). That the hypothesis is still viable today with our more elaborate understanding of the universe does validate the idea to some degree: Our cosmological models cut have kille…

Yes, it dates to the XIX Century, and alternative types of it have been proven right or wrong at times.

Postulating unobservable things is still not a good way to do science. The one good thing of the dark matters theories was that physicists were clear in that it's not a done model, just a map of what's wrong with our understanding. This seems to have changed lately.

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

#185

Post by dcow » Sat, Oct 13, 2018, 7:03 PM UTC

TangoTrotFox wrote: post #146

jccalhoun wrote: post #126

Earlier quoted context omitted.

>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…

Consider something. What is it that makes god did [x] an improbable hypothesis? The fundamental reason is that there is no direct evidence of said god. There is indirect evidence and logical arguments that can favor a god, but that means nothing when you cannot observe a god, you cannot measure a god, and there is no direct evidence for that god. Dark matter still holds more in common with the divine than the practic…

I get what you’re saying. I think you could be way more clear and articulate (took me about 3 reads to understand that you’re just agreeing with the well received parent, I think). I hope that is the reason for the downvotes and not simply people not wanting to hear that rationalism is just as dogmatic as anything it has displaced. Sure it’s better (in the more pragmatic sense), but it still depends on sets of axioms regarded as truth and fails to present explanations for plenty of observed phenomena. It also is strictly not philosophic so it can’t answer “Why?” nor can it yield any sort of ethical/moral framework(s) for understanding reality.

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

#186

Post by walrus1066 » Sat, Oct 13, 2018, 7:06 PM UTC

dogma1138 wrote: post #168

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…

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 travel at nearly the speed of light, so can't clump together to form the concentrated blobs of dark matter we observe from gravitational effects.

So dark matter cannot be explained by the particle we know about.

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

#187

Post by gmjoe » Sat, Oct 13, 2018, 7:14 PM UTC

dogma1138 wrote: post #182

acqq wrote: post #173

Earlier quoted context omitted.

> it might be that some or all of it will end up being baryonic matter It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. > There isn’t a consensus amongst scientists Only for completely useless definitions of the “concensus.”

>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.

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

#188

Post by walrus1066 » Sat, Oct 13, 2018, 7:16 PM UTC

dogma1138 wrote: post #180

gpderetta wrote: post #178

Earlier quoted context omitted.

Isn't some weakly interactive massive subatomic particle pretty much the consensus?

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.

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

#189

Post by acqq » Sat, Oct 13, 2018, 7:16 PM UTC

dogma1138 wrote: post #182

acqq wrote: post #173

Earlier quoted context omitted.

> it might be that some or all of it will end up being baryonic matter It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. > There isn’t a consensus amongst scientists Only for completely useless definitions of the “concensus.”

>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 from the sample of compact ultra-faint dwarfs appear sufficient to rule out dark matter composed exclusively of MACHOs for all masses above ~10e−7 mass of the Sun."

And if your definition of the "consensus" is 100.0000% then I do consider it useless.

https://www.merriam-webster.com/dictionary/consensus

If you use Merriam-Webster's: "the judgment arrived at by most of those concerned" then yes, there is a consensus because "most" begins for me at "more than 60%." And I accept only those that are actually "in the field" and not those that studied something completely different but "have a strong opinion." Sorry, that's automatically useless. I know personally the Ph.Ds who believe nonsense as soon as they are out of the area they have researched personally. It's simply a https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect as in "I was successful while studying X my whole life and therefore I believe I can 'understand' Y better than those who studied Y their whole life." And I'm talking here only about the natural sciences.

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

#190

Post by thx4allthestuff » Sat, Oct 13, 2018, 7:18 PM UTC

Super weird food for thought, but I used to think about the universe a lot as a kid, and back then we were under the assumption that the expansion of the universe was slowing. At some point that viewpoint changed and we now believe it is accelerating, hence the emergence of so called dark matter. Anyway, this led me to envision a fourth dimension, a sphere. Imagine that our universe began at any arbitrary point on the inside of this sphere, and then orient the sphere so that we are at the bottom (like a penny inside of an inflated balloon). Now imagine (don’t believe, just imagine) that our universe is expanding at a constant rate. As we approach the equator of this sphere, the area that we must cover grows larger, but once we pass the equator it begins to grow smaller. And so what might appear to us as slowing down and speeding up could just be the shape of space changing, and not the speed of expansion. Again, just food for thought.