
A tale of the unending hunt for dark matter - devy
https://www.wired.co.uk/article/dark-matter-worth-searching-for-null-results
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JBReefer
Dark matter/energy always sounds like a restatement of aether - unknowable and
unreachable, conceived to fill gaps in the knowledge of the period. I'm
probably wrong, but the parallels are strong.

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tarboreus
My instinct says this as well. "My equation isn't balancing, there must be
something sitting on the seesaw!"

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simcop2387
It's more like, my equations that work for everything else don't match what we
observe in a few cases. But if there's something sitting on the seesaw that I
can't see then it works everywhere. And there being a particle (or particles)
that doesn't interact with the EM force is a testable theory. We've used
particle accelerators to continually exclude areas of energy that the
particles themselves would exist in, and eventually we're going to detect
everything that we've predicted with the standard model or we'll find
something new in an area that we didn't predict and start to know where things
are actually wrong. Either in the particle side of things, or possibly the
gravitational side of things. We know there's something missing or wrong
between the two of them but they appear to work correctly for every case that
we've found a way to test for so far, even if they don't seem to be possible
to merge together.

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jamesrcole
> _This is the epic tale of the unending hunt for dark matter ... Despite huge
> pots of money being poured since the 1970s into dark matter experiments on,
> under or above Earth, despite endless late nights spent doing calculations,
> and despite plenty of media coverage, researchers keep getting nowhere_

It's ridiculous to refer to about 50 years of work so far as an "unending"
hunt, and it's a sign of the very short-term thinking of our age.

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JohnJamesRambo
Well we’ve found a lot of other things in that same timespan, for reference.

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jamesrcole
And a lot of things took much longer, thus my statement.

Also, just because something's been going on for some amount of time says
nothing about how much longer it might take to get the answers.

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Entangled
Forgive my utter ignorance but, what if black holes are not "holes" but solid
spheres of massive density? There you may have your dark matter to boot.

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erik_landerholm
[https://www.sciencedaily.com/releases/2018/10/181002102723.h...](https://www.sciencedaily.com/releases/2018/10/181002102723.htm)

“Based on a statistical analysis of 740 of the brightest supernovas discovered
as of 2014, and the fact that none of them appear to be magnified or
brightened by hidden black hole "gravitational lenses," the researchers
concluded that primordial black holes can make up no more than about 40
percent of the dark matter in the universe. Primordial black holes could only
have been created within the first milliseconds of the Big Bang as regions of
the universe with a concentrated mass tens or hundreds of times that of the
sun collapsed into objects a hundred kilometers across.”

“An as-yet unpublished reanalysis by the same team using an updated list of
1,048 supernovas cuts the limit in half, to a maximum of about 23 percent,
further slamming the door on the dark matter-black hole proposal.”

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Entangled
So, how dense you think the black hole at the center of the milky way is?
Twice the whole galaxy at least? Or just a tiny fraction?

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GW150914
If you really meant dense then you have to rememberer that the average density
of a black hole enjoys an inverse proportionality to its volume. In other
words a supermassive black hole is far less dense on average than a much
smaller hole. However it is still far far denser than a whole galaxy, which is
mostly empty space and diffuse dust.

I don’t think you meant dense though, I think you meant mass, because that’s
sort of how your post seems to be phrased. The answer then is that it is a
minute fraction of the mass of the galaxy. Sag A* is about 4 million solar
masses, and the Milky Way has 250 billion stars, many of which are far more
massive than Sol. Even ignoring other objects like stellar remnants and
nebulae, the mass of the central black hole is negligable on the scale of the
whole galaxy.

