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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

#71

Post by everdev »

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…

Almost all of our current scientific knowledge has come from challenging the consensus of the times. Scientific skepticism is always healthy and should be welcomed. Even if the original theory is correct, that doubt will simply help science better explain and prove the current understanding. I'd actually be more worried if everyone agreed about something. Even gravity we thought was fully solved until Einstein doubted that we understood it fully. Let's be careful of putting anything in the category of "beyond doubt", especially theories that haven't been tested or confirmed directly.

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

#72

Post by chongli »

tomp wrote: post #54

The simplest “proof” of dark matter - Kepler’s Laws dictate that objects with smaller orbits (closer to center) move faster (in terms o fangular velocity). Our solar system works like that. Our galaxy doesn’t - its spiral shape indicates that the angular velocity varies minimally with radius.

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 assume it holds at all scales.

Look at tiny water droplets. They don't behave at all like large bodies of water.

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

#73

Post by panic »

zvrba wrote: post #64

So my takeaway from this article is: where there is a concentration of mass, there is dark matter. (Quote: "According to models and simulations, all galaxies should be embedded in dark matter halos, whose densities peak at the galactic centers.") Wiiild speculation: perhaps mass is actually a complex number with real and imaginary parts (analogous to how quantum mechanics describes fields), and what we're able to mea…

> So my takeaway from this article is: where there is a concentration of mass, there is dark matter.

Not always: https://www.nature.com/articles/nature25767

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

#75

Post by mikekchar »

beefield wrote: post #59
mikekchar wrote: post #45

Earlier quoted context omitted.

The thing you are missing is that the "missing mass" isn't observable on the scale of the solar system. It's missing on the scale of large scale galactic structures -- i.e. lots and lots of galaxies . When we look at those structures, we can't figure out how they got that way unless there is a whole bunch more mass than there looks to be. Apart from that, we know nothing . People speculate that maybe there is some we…

Okay, let's try to reformulate. What is the average density of dark matter in places we know there is dark matter? Then, assuming here were dark matter with that density in earth, how much that would be? I am just trying trying to get my head around how sparse the dark matter actually is, wherever it actually exists. Would we have one kilogram of dark matter to observe? Damn. Should have googled in the first place. H…

But even then, there's no reason to assume that there is any in that space. For example, imagine that all the dark matter was in a disk around the solar system, way out farther than the asteroid belt. If you could see through it, you would never know. Or maybe it rings galaxies. Or maybe it hangs out in clumps between galaxies. Or... It literally could be anything because we can only measure it on the scale of mind boggingly massive structures.

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

#76

Post by sandworm101 »

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…

>> dark matter seems to repeatedly rub people the wrong way today, more so than any other scientific concept I can think of.

Because, while interesting to a great many scientists, the practical implications of this knowledge are centuries away. Defining dark matter, understanding the backbone of our universe, isn't going to cure cancer. It isn't going to fix global warming. It isn't going to get us to Mars. So when people read of massive experiments throwing unending brainpower and money into the DM hunt, it is natural for them to react as they do. Astronomers give us pictures of far away places that satisfy our natural need to explore. DM hunters stare at numbers and statistics, generating papers and messy diagrams. They aren't fighting an uphill PR battle.

There are also a not-small number of people for whom the DM hunt represents a challenge to their fundamental beliefs. Talk of colliding galaxies billions of light-years away conflicts with the young-earth model that is part of their daily lives. Rather than criticize on that basis and appear ignorant, they lash out on other grounds.

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

#77

Post by jumpywizard »

Anyone trying to use machine learning to make a "black box" mathematical framework? Feeding known measurements as "learning" (including known anomalies and discrepancies)?

Using techniques such as deep learning for program synthesis. https://www.microsoft.com/en-us/research/blog/deep-learning-...

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

#78

Post by foobarbecue »

sandworm101 wrote: post #76
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…

>> dark matter seems to repeatedly rub people the wrong way today, more so than any other scientific concept I can think of. Because, while interesting to a great many scientists, the practical implications of this knowledge are centuries away. Defining dark matter, understanding the backbone of our universe, isn't going to cure cancer. It isn't going to fix global warming. It isn't going to get us to Mars. So when p…

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 invisible, processes and substances.

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

#79

Post by gbrown »

sonnyblarney wrote: post #33
gbrown wrote: post #17

Earlier quoted context omitted.

Perhaps we could call that thing: "dark matter" for now. In seriousness, we can observe the effect, and even map the distribution of the stuff.

"In seriousness, we can observe the effect, and even map the distribution of the stuff." No, we can measure the dissonance between our best theories and reality. And make a conjecture about 'stuff'.

I'm not a physicist, but my basic understanding of the state of the science tells me you're simply incorrect. We can observe the effect of dark matter via gravitational lensing, and folks much smarter than me have devised studies to exclude differential behavior of gravity at classical and galactic scales.

Give me a recent and well supported study indicating that dark matter may be something other than matter, and I'll happily read it.

My understanding is that the existence of dark matter is uncontroversial among physicists, and that the best bet is some sort of WIMP.

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

#80

Post by gbrown »

drewg123 wrote: post #25
gbrown wrote: post #17

Earlier quoted context omitted.

Perhaps we could call that thing: "dark matter" for now. In seriousness, we can observe the effect, and even map the distribution of the stuff.

That assumes that it is "matter". Maybe there is something we just fundamentally don't understand about gravity.

That's not impossible, but I tend to believe the experts when they say it's not likely (and have explicitly ruled out several such explanations).
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