
If this type of dark matter existed, people would be dying of unexplained wounds - gilad
https://www.sciencemag.org/news/2019/07/if-type-dark-matter-existed-people-would-be-dying-unexplained-gunshot-wounds
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gus_massa
It's an interesting article in spite of the silly title. The researchers made
a joke article and it went more popular than the serious research article :(.

I propose to change the title to "Dark matter detection in traces in granite
(and humans)" but it breaks all the official and unofficial guidelines.

Note that the volume and lifetime of granite is much bigger than humans, so if
they didn't find any trace in granite they don't expect to find one in humans.
Also, IIUC there is nothing special about organic matter.

How "loud" would it be an event like this in the middle of the sea? Can it be
heard with the acoustic detectors to detect roge nuclear explosions?

~~~
bromuro
Do you really find weird (or bad) that a joke is more popular than a boring
research paper? It’s a good way to wake people’s curiosity about topics they
never think about. Probably, it worked on you too as you have read the article
:)

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ben_w
Hm. They claim to have zero unexplained gunshot-like injuries in Canada, the
United States, and Western Europe over a ten year period. I find this hard to
believe. Even if every gun injury was currently attributed to an identifiable
shooter (a claim which would itself surprise me) miscarriages of justice are a
known thing and people do get convictions overturned.

It’s still an interesting idea, but where did “none” come from?

~~~
msbarnett
The article alludes to the answer, but the paper is linked in the article, and
answers this more preciselyat the beginning:

> Hence their destructive effect is likely to be qualitatively different from
> that of a bullet; a macro impact typically heats the cylinder of tissue
> carved out along its path to a temperature of 10^7 K[18, 19], resulting in
> an expanding cylinder of plasma inside the body. While some studies have
> been done on collisions of hypersonic, micron-sized projectiles with fixed
> targets[23], these differed significantly from macro collisions in that the
> experimental projectiles were of much lower density, and the targets were
> “hard” rather than “soft”. Nonetheless, it is reasonable to take the kinetic
> energy deposited by a macro as a threshold for significant damage to the
> human body. Energy con- servation requires that the macro energy ultimately
> be deposited in the body in some form, whether mechanical or thermal, which
> will result in an equivalent amount of damage.

Victims would look they’d been shot with a laser bullet out of sci-fi. As is
mentioned in the article, they found no evidence of bullet wounds that also
featured vaporization of tissue.

> These deaths would not go unnoticed—they would leave victims dead or dying
> with a tubular wound where their flesh was vaporized.

~~~
tomatotomato37
Presumably odd angles of entry would also be a clue. A shot that enters near
verically while the victim was standing would be extremely unusual in a one-
story building if you aren't expecting the "bullet" to have come from space

~~~
pure-awesome
Also, wouldn't there be a tunnel all the way from the top of the building and
through the person?

People would wonder if a government agency wasn't using some sort of drone or
satellite weapon to eliminate targets.

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dasm
From a terminal ballistics background, it seems very unlikely that this injury
would appear to be a gunshot wound.

Bullets behave very differently according to their mass and velocity, not just
their energy. A wound channel for this a particle would likely be very
different from any bullet.

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flatline
Purely anecdotal at this point but I remember hearing on the news in the mid
90s about a woman in the Boulder/Denver area who was killed by a “stray
bullet” of unknown origin while sitting in her house. So these types of deaths
are not _entirely_ unheard of, if we just go by the scant details of this
article.

~~~
ceejayoz
Deaths featuring bullets that cause _tissue vaporization_ are pretty unheard
of, though. These would cause a _very_ different sort of wound versus that of
a bullet.

~~~
saalweachter
Also, if they find a bullet in you, it's a different sort of "unexplained
stray bullet".

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new_guy
Maybe this is what spontaneous human combustion is? People burst into flames
randomly.

If this hit a human body and expanded as a ball of plasma, it might not look
like a bullet wound like they think but it'd just burn the person alive, and
there's plenty of recorded accounts of that happening.

Previously it's been attributed to the body losing control of its ability to
regulate its temperature (homeostasis) but this mechanism seems way more
plausible, they get hit by a particle of this that expands as a super heated
ball of plasma and burns them alive inside out.

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jayd16
This is a joke article, right? Isn't this like trying to prove meteorites by
unexplained stonings?

~~~
dodobirdlord
It's clearly intended to be funny, but the reasoning is perfectly sound. If a
particular kind of dark matter candidate existed, it would need to be
distributed with a density that would result in occasional very obvious, very
fatal collisions with people. Since we have no record of people dying due to
inexplicably having large columns vaporized through their bodies, we can
exclude this particular class of dark matter candidate particles.

The more serious component of the research focused on searching for these
events in old deposits of granite.

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ChuckMcM
This is an interesting outcome. It is something that I've also been bothered
by the Dark Matter hypothesis which is how it is always "somewhere else". Dark
energy theories tweak the equations the other way and are equally troublesome.
The idea a bunch of people can be used as a detector is pretty humorous too.

I expect that resolving this question will be the source of many Nobel prizes.

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Nasrudith
Reminds me of the concept of negative mass matter as dark matter. That would
make getting hit by it very difficult as it repels and is repelled by regular
matter and thus would constantly flee all normal mass. Not sure it would be
very consistent with the observed universe though.

~~~
a1369209993
Actually, a: negative mass would have the _opposite_ effect as dark matter -
gravitationally repelling all nearby matter - so you'd need even more dark
matter to make up for it; b: negative mass is actually _attracted_ to positive
mass[0], so quantaties of dark negative mass small enough to not have
noticable gravitational effects would follow the same orbital trajectories as
positive dark matter.

0: Eg, if you have two particles with equal and oppositely-signed mass in
otherwise free space, they'll "fall" in the direction of the positive
particle. The two-particle system has zero mass, zero kinetic energy and zero
force driving its accelleration, which could be taken as a pretty good
argument that negative-mass particles don't actually exist.

~~~
anchpop
Does this mean if you had a rock of negative-mass and a rock of positive mass
in space they would chase each other?

~~~
a1369209993
Yes; see second paragraph. It's probably highly unstable if there are any
other gravity sources involved, but I don't have a good physics simulator on
hand to check.

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mxcrossb
Finally a Kennedy assassination theory I can believe

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gattr
On a similar note: "How close would you have to be to a supernova to get a
lethal dose of neutrino radiation?" [0].

BTW, this happens in the novel "Iron Sunrise" by Charles Stross, where people
on an Earth-like planet suffer the misfortune of their star reaching
(artificially) the supernova stage.

[0] [https://what-if.xkcd.com/73/](https://what-if.xkcd.com/73/)

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tomxor
What is the probability of this occurring within a noticeable time-frame?

Without an estimate a lack of occurrence does not disprove anything. Even if
dark matter is supposed to make up 85% of the universe it is unlikely to be
distributed in the same way as other matter. For example if it does not
interact with gravity, or as strongly, it could be comparatively uniformly
distributed or at least more dispersed compared to matter. In which case the
probability of a particle intersecting a human would be astronomical.

Just opening this door, but some actual estimates from those with the domain
knowledge and experience would be nice.

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mikewarot
What if we just took a bunch of old steel I-beams, cut them into sheets,
ground and polished them flat, then scanned with a scanning tunnelling
electron microscope and looked for evidence of interaction with dark matter?
You could run an experiment with observations going back to the production of
the steel... 100+ years of data at the get go.

~~~
tlb
That sounds much more expensive, per cubic meter of material, than observing
humans. You can observe a hundred million cubic meters of human just by
reading medical reports.

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klingonopera
What exactly was it again that leads humanity to assume dark matter is a
thing?

Last I checked, it was the unexplained speed of the outer parts of spiral
galaxies that lead us to assume that dark matter must be the cause.

Have there been any recent developments to further solidify that dark matter
is a thing?

~~~
ajkjk
No, there are dozens of distinct verifications; its presence is established
essentially beyond the shadow of a doubt. It is anything but an assumption.

See for instance
[https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...](https://en.wikipedia.org/wiki/Dark_matter#Observational_evidence)

Also
[https://www.reddit.com/r/space/comments/a8vgm9/how_many_of_y...](https://www.reddit.com/r/space/comments/a8vgm9/how_many_of_you_think_that_dark_matter_is_just_a/)
has a good summary.

~~~
ianai
...and yet I find it weirder than what I understand of QM.

~~~
ajkjk
Then you don't know enough qm.

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rsynnott
Well, we probably wouldn’t; if it was common enough in that universe we’d
probably have evolved to deal with it. And we might be very different.

~~~
dodobirdlord
Evolutionary processes aren't going to select for resistance to rare high-
energy events. They are not common enough to significantly impact fitness and
too drastic for small mutations to influence survival. Humans evolved from
millions of years of hominid evolution on the African savanna, and have have
evolved no immunity to lightning.

~~~
rsynnott
Well, yeah, if it was pretty rare it wouldn’t have any effect.

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nharada
> a macro impact typically heats the cylinder of tissue carved out along its
> path to a temperature of 10^7 K[18, 19], resulting in an expanding cylinder
> of plasma inside the body

bummer

