
Dark Matter May Be Trapped in All the Black Holes - dnetesn
http://nautil.us/blog/dark-matter-may-be-trapped-in-all-the-black-holes
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KirinDave
Meanwhile, the evidence for unbound WIMPS is sorta growing:
[http://earthsky.org/space/waterloo-image-dark-matter-
cosmic-...](http://earthsky.org/space/waterloo-image-dark-matter-cosmic-
web-2017)

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ajross
And the X-Ray axion evidence from a few years ago looks OK too.

But honestly: my money would have to go on this one. Black holes are by far
the most boring and conventional of the existing theories, and the easiest to
refute. aLIGO will tell us if it's right or not within years.

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Florin_Andrei
> _Black holes are by far the most boring and conventional of the existing
> theories_

I was ready to start arguing, but then I realized you were speaking in the
context of dark matter theories. :)

I feel there's gonna be a few interesting years or couple decades ahead. Maybe
not as big as the early 1900s. Maybe as big. Maybe even bigger.

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throwaway7645
That's all options :)

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Florin_Andrei
Well, uncertainty is exciting. :)

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philipov
May you live in uncertain times.

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nerfhammer
May all your predictions be either jointly exhaustive or not jointly
exhaustive.

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KirinDave
Threads like this are what keep me coming back to orange website. They are
rare & touchingly innocent flowers amongst a field of awash with metaphorical
blood.

Thank you.

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sixothree
At the top of the article, is that real imagery or some sort of mock-up?

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Florin_Andrei
Of course it's a mock-up. Black holes have never been imaged from up-close.
Maybe the background is an actual photo, but not the thing in the middle.

But it does seem to be a more or less realistic simulation of light ray
distortion in the gravitational field of a black hole.

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sixothree
I thought NASA usually described these sorts of things as "artist depictions",
and that maybe I had not been paying attention and some wonderful imagery had
arisen.

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notzorbo3
Basically non of the images you ever see from anything in outer space are
real. It's always composite images or colored in or spectrum-shifted into our
visible light range.

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Florin_Andrei
I am actually active in the field of astrophotography. What you're describing
is a common-enough opinion, but it's inaccurate to the point of being
misleading.

When imaging outside of the visible spectrum, you have no choice. You must
translate it into visible light, or else you could not see it. So, yes, there
are many false-color images out there, and for a good reason - they show us
the invisible part of the EM spectrum.

Of those taken with visible light, there are several categories.

Some of them are indeed false color. Examples: imaging the Sun with a narrow
monochromatic filter such as hydrogen alpha, or some "magic" wavelengths like
540 nm. These should be displayed in their respective colors (red for hydrogen
alpha, green for 540 nm, etc), but often arbitrary color choices are made,
because the original image is monochromatic anyway, so it should not matter
what color is displayed in as long as its nature is understood by the viewer.

And then there's a very broad slice of the pie where the colors are basically
real, they're just not perceived that way by the human eye, or even by the
camera - and yet they do represent the original spectral content of the
incoming EM radiation.

For example, when observing a galaxy or a nebula, all the human eye can see is
a black-and-white smudge. Even in a telescope, you almost never see color with
your own eyes when looking at these objects. Why is that? Because we have two
kinds of light receptors in our eyes, and the ones that actually see color do
not work in low light conditions - we are all colorblind there.

But attach a camera to a telescope, have the instrument track the nebula for a
long time, open the shutter and let the sensor collect photons for a while.
Then look at the result. Suddenly, you see colors. Why is that? Because with
long exposure, the camera can actually see colors. That's something that our
eyes cannot do.

But are those images "enhanced" somehow in post-processing in ways that make
those colors unnatural? It depends. For objects like the Orion nebula, or the
Horsehead, the colors are strong enough to not need much post-processing. In
other cases, you may have to apply fairly strong contrast and saturation
boosts.

So there's a whole continuum of images taken in visible light, where the
amount of post-processing varies from quite lightweight to pretty heavy. With
some experience, you can tell which is which. I've taken images of the Moon in
high resolution and I've left it alone in post - you can tell because the
colors are drab, it looks like the surface of an asphalt road. I've also taken
moonshots where I've applied very heavy saturation boosting - you can tell
because you can start seeing colors in an otherwise gray landscape. This
allows you to detect surface, terrain, and mineral features that would not be
apparent otherwise, things like ejecta from impacts and so on.

[http://i.imgur.com/le5vrzh.jpg](http://i.imgur.com/le5vrzh.jpg)

And finally there are many, many images of planets such as Jupiter or Saturn,
where the colors basically match the imagery taken by space probes hovering
nearby, and would match what people would see with their own eyes if they were
in actual orbit there.

\---

TLDR: The real answer is "it depends". Some colors are totally fake. Some are
real, but boosted. Some are real, it's just that the human eye could not see
them due to our scotopic vision characteristics. And others are actually quite
realistic in every way. It's a broad continuum. You learn to tell them apart
by being involved in actually making them.

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andy_ppp
What semi accessible books are available on the subject?

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gfodor
A universe peppered with black holes may also explain the Fermi paradox. A
terrifying but logical thought.

~~~
ythn
Could black holes also be masking an infinite number of stars?

Stephen Hawking notes in his book "A Brief History of Time" that we know that
there aren't infinite stars because otherwise the night sky would have no
patches of darkness since an infinite number of stars would imply that you
could shoot out an arbitrary ray from earth and it would always reach a star.

However, black holes (lots of them!) could trap light and obscure line-of-
sight stars.

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coliveira
This line of reasoning works only in a static universe. In a expanding
universe, stars can move apart faster than the speed of light. Thus there
might be a lot beyond the observable universe that can never be detected.

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Neeek
I mean... isn't it still technically correct though? We have an opaque horizon
of light, it's just all in the microwave spectrum.

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vectorEQ
nonsense context makes science very hard to understand.

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stutterSpeaker
So the way I understand it dark matter doesn't even have any physical
interaction with matter. But it must be affected by gravity, or else it
wouldn't end up trapped in black holes right?

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ww520
Dark matter does interaction with matter via gravity. It just doesn't interact
via electromagnetism, the weak nuclear force, or the strong nuclear force. Our
usual observation techniques with electromagnetism can't detect it.

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37
Yes. In fact, this is how we detect DM, by measuring the speeds of the
galaxies, rotating around the galactic core. Our calculations point to a
slower speed than observed, thus implying some mass of "matter" which we
cannot see.

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TekMol
I am sceptical about dark matter. It feels like it was invented because the
theories we have do not match our observations.

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ngold
That is kinda the hole point.

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zhengyi13
I see what you did there.

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AnimalMuppet
I'm missing it...

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kafkaesq
So if, hypothetically, dark matter had some detrimental effect in those parts
of the universe where it appears in overly high concentrations (making the
universe less "interesting" in those parts... less able to produce life-
bearing planets, say) --

\-- then black holes would, in effect, be (our) universe's GC mechanism. Or at
least, its "janitors" in some form.

Pretty cool.

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qubex
Except they don't relinquish what they gobble up, so they're not making a
finite resource (memory) available for re-use, they're a total resource sink.

Whether that's ’cool’ or not is a matter of persona preference.

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tdb7893
Don't black holes emit radiation or something?

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bitshiffed
Hawking radiation, yes. They eventually evaporate.

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_FKS_
Hawking radiation is speculation AFAIK, there's no observation to back it up.

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KGIII
Some light reading on it:

[https://medium.com/the-physics-arxiv-blog/first-
observation-...](https://medium.com/the-physics-arxiv-blog/first-observation-
of-hawking-radiation-9d77fa8c8055)

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macspoofing
OP isn't wrong. That we haven't proven the existence of Hawking Radiation is
the only reason why Hawking hasn't won a Nobel.

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KGIII
No, just some light reading where we have reason to believe it has been
observed and may be able to devise further methods to observe it.

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macspoofing
I don't dispute that. I think the consensus has accepted Hawking radiation as
real ... but we haven't seen evidence yet (and we may never, your link
notwithstanding, given how tiny the effect is).

