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

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

#111

Post by kamaal » Sat, Oct 13, 2018, 3:44 PM UTC

CydeWeys wrote: post #93

chongli wrote: post #72

Earlier quoted context omitted.

This carries the implicit assumption that all forces fall off monotonically with distance. Maybe gravity doesn't? Maybe it has a curve similar to a meteor impact crater: raised in the middle, a deep valley, and raised at the outer edge? Of course, with more evidence, such as the observations of the Bullet cluster, these simple explanations fall apart. But at any rate, it's not enough to take one observation and assum…

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.

If I'm not wrong, Newton's laws can still be held to be true in some cases even inside GR?

Some where in the past, some one could come up with a new model which could show us new truths, and yet could contain GR to be true in some cases.

In GEB, Hofstadter show us part of the ways so see intelligence emerging from noise and garbage, is to understand when you design a system, you start with axioms, truths and rules that are true in a system, could be total garbage in another.

Models are what we use to understand things, That's not how things are.

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

#112

Post by cygx » Sat, Oct 13, 2018, 3:46 PM UTC

sanxiyn wrote: post #104

foobarbecue wrote: post #78

Earlier quoted context omitted.

How do you know it won't cure cancer? Marie Curie checked out some invisible physics and discovered radioactivity. Now we use it to treat cancer. I suspect that practical outcomes and technologies arising from understanding dark matter will be huge. Also, I think you're missing the point of astronomy. "astronomers" today are generally astrophysicists or planetary scientists, and they are studying fundamental, mostly…

> I suspect that practical outcomes and technologies arising from understanding dark matter will be huge. I doubt it. More than 50 years after discovery of neutrinos, we are yet to find any practical outcomes or technologies.

So you're saying a better understanding of nuclear reactions has not had practical implications? Just because the particle itself is 'useless' from a technological perspective doesn't imply the same is true for the accompanying theory...

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

#113

Post by kamaal » Sat, Oct 13, 2018, 3:46 PM UTC

darawk wrote: post #98

Can someone that knows a bit more about this explain why we believe that this dark matter substance must exist and not simply that we have an incorrect model of gravitation?

For a very simple reason that, you have to start explaining things from the concepts you already know are true.

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

#114

Post by [deleted] » Sat, Oct 13, 2018, 3:47 PM UTC

iandanforth wrote: post #110

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…

The article invites that kind of response by presenting arguments for the existence of dark matter as if they are undeniable. In reality the road to consensus was anything but smooth. Science works best when you are skeptical of claims, test alternatives, and find evidence that contradict the alternative hypothesis. If you want to discuss controversial science you need to anticipate objections, show the work has been…

[deleted]

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

#115

Post by [deleted] » Sat, Oct 13, 2018, 3:49 PM UTC

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.

[deleted]

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

#116

Post by bordercases » Sat, Oct 13, 2018, 3:50 PM UTC

gmjoe wrote: post #63

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…

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…

Not sure I'd want to play the psychologizing game here. It could just as easily be used to explain the success of Dark Matter as a topic of discourse in the public imagination.

"Wow, look how insignificant it makes us feel, how insightful", or, "Just imagine how much is hidden from us every day!"

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

#117

Post by user812 » Sat, Oct 13, 2018, 3:52 PM UTC

williamdclt wrote: post #13

user812 wrote: post #7

Earlier quoted context omitted.

Indeed. Physics is wrong on many fundamental levels, but everytime physicists find fundamental errors, they propose another entirely theoretical layer of complexity, with the "benfit" that no one is able to practically refute it.

It's not adding a layer of complexity, it's peeling off a layer of abstraction. With the "benefit" that it describes better what we observe and that it allows to successfully make new predictions. What's your alternative to the scientific method exactly?

100 or so years ago physics went into the wrong direction, ignoring people like Tesla who argued for the aether model.

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

#118

Post by bordercases » Sat, Oct 13, 2018, 3:52 PM UTC

CydeWeys wrote: post #93

chongli wrote: post #72

Earlier quoted context omitted.

This carries the implicit assumption that all forces fall off monotonically with distance. Maybe gravity doesn't? Maybe it has a curve similar to a meteor impact crater: raised in the middle, a deep valley, and raised at the outer edge? Of course, with more evidence, such as the observations of the Bullet cluster, these simple explanations fall apart. But at any rate, it's not enough to take one observation and assum…

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.

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

#119

Post by user812 » Sat, Oct 13, 2018, 3:53 PM UTC

geertj wrote: post #100

user812 wrote: post #7

Earlier quoted context omitted.

Indeed. Physics is wrong on many fundamental levels, but everytime physicists find fundamental errors, they propose another entirely theoretical layer of complexity, with the "benfit" that no one is able to practically refute it.

> Physics is wrong on many fundamental levels Physics, when practiced according to the principles of the scientific method, is never wrong (or right). Physical laws try to explain the world around us using mathematical models. Those models can be tested over a certain domain of experimental parameters D. A physicist, when speaking accurately, would never say that a physical law L is correct. They would say that L cor…

No, it is fundamentally wrong in itself, because it went into the wrong direction 100 or so years ago, when physicists ignored the aether model.

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

#120

Post by cygx » Sat, Oct 13, 2018, 3:54 PM UTC

darawk wrote: post #98

Can someone that knows a bit more about this explain why we believe that this dark matter substance must exist and not simply that we have an incorrect model of gravitation?

Because such a minimal change to the model ("there's just some more stuff we can't see") fixes a number of problems in one fell swoop (off the top of my head, galactic rotation curves, observations of gravitational lensing, a cosmological model compatible with obervations of CMB fluctuations, structure formation, cosmic evolution).

Theories of modified gravity can fix those individually, but as far as I'm aware, no alternative has been shown to be viable once taken in combination.