If this type of dark matter existed, people would be dying of unexplained wounds | Hacker News Reader

If this type of dark matter existed, people would be dying of unexplained wounds

sciencemag.org

97 pointsgilad58 comments

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?

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 :)

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?

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.

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

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.

> heats the tissue to a temperature of 107 K In case this confused anyone else, it should be 10^7 K, ten million degrees.

Cheers, the caret got lost in the copy paste

I think copy-paste implementations should be changed to insert a space when the input text changes height like that.

Thanks, I’d read but not understood the implications there.

An actual gunshot-injury would would necessarily leave an entry wound.

The dark matter particle they searched for would, if it exists, would enter the body undetected and interact inside the body, producing the gunshot-like damage inside the body, and I guess likely an exit wound, without any entry wound.

That's basically how the current dark matter searches work that I know of, albeit with different media than a human body.

If you were a doctor or a forensics pathologist, and saw a hole in a body, how much evidence would you need to convince yourself that this was caused by something occurring inside and work its way outwards, rather defaulting to thinking its was caused by something outside that went in?

This isn’t a rhetorical question by the way, I genuinely do not know if the mere absence of a bullet at the deep end would be sufficient, or if entrance and exit wounds look so radically different from each other that no one could possibly mistake one for the other.

I know nothing, wild speculation follows.

I'm pretty sure it's "easy" to tell an entrance from an exit, especially with a hollow point bullet (basically like an explosion out of the exit). Even without the explosion thing, I'd be shocked to learn that there are not tell-tale signs because an object pushing inward at a high speed will leave the tissue at certain angles, like maybe the soft tissue caved a little inward around the entrance, the bones broken in the direction the bullet was traveling, that sort of thing.

But all those thing depend on the object being ballistic, like a fast moving object flying through the body. With a "laser beam" sort of wound, I'm not sure any of that would apply.

I assume that looking at a wound caused by a laser would be pretty baffling -- a roughly cylindrical, cauterized void with no apparent directionality. Even if the cause wasn't clear, I think it would look weird enough for a professional to say "Wait, something is super weird here."

I read an autobiography of a forensics pathologist recently and he spent a lot of time obsessing about the shape of wounds (to the point of upsetting his family by stabbing their Sunday roasts so he could inspect the resulting wounds).

[The book is "Unnatural Causes" by Dr Richard Shepherd - strongly recommended even if it is just a wee bit gruesome in places.]

Considering that the wound would be heated to 10^7K, it'll likely create a very unique type of hole in the body.

I dont understand why you claim gunshots necessarily leave an entry wound.

Massive amounts of research was done to prevent bullets from doing exactly that.

Have you reversed "entry" and "exit," or is this a reference to something like the CIA's alleged heart attack gun?

> zero unexplained gunshot-like injuries in Canada, the United States, and Western Europe over a ten year period. I find this hard to believe.

If this was a thing, it would presumably be constant throughout history, even before guns were invented. Heck, you'd see it as cause of death in fossilized dinosaurs.

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.

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.

Well, if the bullet was found in the ensuing investigation, it was not a death from an unexplained wound.

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.

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

if the bullet could not be found, wouldn't that be noted too, as that would make it even more mysterious?

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.

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

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.

Well... haven't the dinosaurs experienced such a phenomena?

"Beyond reasonable doubt", I believe, are the keywords...

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.

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.

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.

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

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.

Finally a Kennedy assassination theory I can believe

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/

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.

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.

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.

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?

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...

Also https://www.reddit.com/r/space/comments/a8vgm9/how_many_of_y... has a good summary.

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

Then you don't know enough qm.

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.

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.

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

> 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

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