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[–]meteoritehunter 4267 points4268 points  (188 children)

Geochemist here. I work on meteorites, including some isotope geochemistry.

I'd like to believe the study, but the 53Mn data they've posted look seriously questionable to me. Just look at the spread in error bars across the board. You could also make an argument for a supernova at 6-6.5 Ma based on their data, and an anomalous low in 53Mn at around 5 Ma. It all falls within the noise of their data.

I'd love to see a statistical justification for what they're claiming, because the data they've posted looks...bad. Just look at their running average (red line) in the above graph. The error bars on that low 53Mn value at 1.5 Ma don't come anywhere near it, which means that the analysis is wrong or the error bars are too small. Their dataset is full of points that don't agree with their running average, and they're basing their groundbreaking conclusions on a cluster of three points whose stated errors (the error bars that we know have to be an underestimate) could make them consistent with a completely flat running average at a C/C0 of 0.9.

This looks really bad to me.

[–]Ocean_Chemist 1743 points1744 points  (112 children)

Yeah, fellow isotope geochemist here. This data looks like absolute garbage. There is no statistically significant deviation in the 53Mn/Mn at 2.5Ma. They should also be plotting the 53Mn/10Be ratios relative from that expected from cosmogenic production. I honestly can't believe this paper got published

[–]bihari_baller 365 points366 points  (69 children)

I honestly can't believe this paper got published

I find this concerning. How can an academic paper with such misleading data get published? I looked up the journal, The Physical Review Letters, and it has an impact factor of 8.385.

[–][deleted] 195 points196 points  (20 children)

I work in academic publishing and might be able to shed some light...

Like any decent journal Physical Review Letters is peer reviewed. Peer review only ensures that a paper doesn't have egregious errors that would prevent publication, like using 4.14159 for pi in calculations, or citing a fact that's so obviously false ("Hitler was born in 1917 in the small town of Moosejaw, Saskatchewan."). Peer review does not check calculations or data interpretations for accuracy. That part is left to the scientific community to question, follow-up, write up, and debate.

So, does bad data get through? A lot more often than you'd probably like to know. On a personal and academic level, a problem I have is the distinct lack of replication studies, so you can toss just about any data out there, pad your CV, and really offer nothing of substance to the library of human knowledge. The geochemists above make very good, very valid points about what they've seen in the paper and I'd absolutely love to see someone write up why the results are questionable. Sometimes publications get retracted , sometimes they get resubmitted with errata ("forgot to carry the 1!"). It's important that garbage data is not just left to stand on its own.

[–][deleted] 20 points21 points  (5 children)

That is sad because “peer review” used to mean something. Peer review used to mean (and still does in dictionaries) that a peer reviewed all of the work, checked out your statements and data, and then said “based on the review, this is good to share with the academic community via a scientific journal or publication.”

I get a little steamed on this because I teach a class on understanding data, and have to significantly alter the weight I give academic journals as reliable, due to this specific situation.

[–][deleted] 20 points21 points  (0 children)

I think it harkens back to an era where academics (and, hence, peer reviewers) had substantial statistical education. Today, that's often not the case, and statistics, as a field, has developed significantly over the past decades. Unless a researcher has at least a minor in statistics, over and above the one or two statistical methods courses required of undergrads/grad students, they'd be better off anonymizing their data and handing it off to a third-party statistician to crunch the numbers. This would eliminate a TON of bias. However, that doesn't help peer reviewers that don't have a background in statistics to be able to determine what's "appropriate".

That said, studies that don't have statistically significant results are just as important to the library of human knowledge. However, the trend in academia is that such studies are "meaningless" and often don't get published because the results aren't "significant". This reveals a misunderstanding between "signficance" and "statistical significance" that REALLY needs to be sorted out, in my opinion.

[–]Kaexii 83 points84 points  (39 children)

ELI5 impact factors?

[–]Skrazor 157 points158 points  (20 children)

It's a number that tells you how impactful a scientific paper is. You get it by comparing the number of articles published by a journal over the last two years to the number of times articles of this paper got cited in other people's work over the last two years. And a higher impact factor is "better" because it means the things the journal published were important and got picked up by many other scientists.

So if a journal has a high impact factor, that means that it has published many articles that are so exciting, they made a lot of people start to work on something similar to find out more about it.

Though keep in mind that all of this says nothing about the quality of the articles published by a journal, it only shows the "reach" of the journal.

[–]jpivarski 205 points206 points  (6 children)

As a physicist, often involved in data analysis, I wouldn't say this plot looks inconsistent with the conclusion. It looks "bad" in the sense of being unconvincing—I'd also want to see pull plots and p-value plots and other models fit to the same data to determine whether I believe it or not. Before passing judgement on it, we'd have to see the paper, or if the full argument isn't there, then the supporting documents that contain the full argument.

None of these data points look more than 2.5 or 3 sigma from the model: they're consistent, at least. The problem is that the big error bars take up a lot of page space—only the smaller, better hidden ones matter. If the data were binned (combining points and thereby reducing error bars by averaging) it might be a more convincing display, but the fit gets most of its statistical power from being unbinned.

But my main point is that we can't look at that plot and say that the data analysis is wrong. A lot of good data analyses would have plots that look like that if you insisted on showing raw data only.

[–]jpivarski 8 points9 points  (2 children)

Since this got so much attention, I read it more carefully today.

  • Phys. Rev. Letters is indeed a prestigious journal, the flagship journal of physics. (Not geophysics, astrophysics, etc.: physics. That's why it has such a high impact factor.)
  • Articles in this journal are not allowed to be longer than 4 pages. It's for getting the word out about something, and often there will be a longer paper with more details in another journal.
  • This is a rather simple fit. But it's not wrong and the conclusions are not misleading. More points below.
  • The chi2 is not "very high": it's 58.9 out of 50 degrees of freedom. The reduced chi2 (58.9/50) is what's supposed to be close to 1. The chi2 probability is 82%, not too close to 0% or 100%.
  • The fact that the chi2 is easily within range is the same as the statement that the points are not too far from the fitted line, given their error bars. The problem with the "look" of the plot is that big error bars mean more ink on the page, so your eye is drawn to the wrong part. It's the cluster of points must the peak of the Gaussian that drive this fit—the rest are a self-calibration. (See below.)
  • The model is simplistic (Gaussian with fixed width and flat background), but without strong constraints from the data, you want a simple model to give a rough estimate like this.
  • It would have been nice to see local p-value vs t0 (horizontal position of the peak) to see if there are any other significant peaks at different times. However, there's a 4-page limit, and you have to interpret local p-value carefully. (What particle physicists call the "look elsewhere effect," but I think it has different names in different communities.)
  • If the width had been allowed to float, there would have been a lot of false minima in this dataset. You could fit a narrow peak to any one of those highly fluctuating points.
  • But if the width is fixed, you need a strong theoretical reason to do so. They cite two papers for that—it rests on the strength of those papers and the applicability of those results here, which I can't speak to. I'm not an expert.
  • Including the flat baseline in the fit is a way of using the data to calibrate itself. The null hypothesis is a flat line of unit ratio, so that calibration had better come out as 1.0. it does: 0.928 ± 0.039 (within 2 sigma).
  • The "excess" they're taking about is the fact that the height of the Gaussian fit (a) is significantly bigger than zero: 0.29 ± 0.10 is almost 3 sigma.
  • They said "more than 3 sigma" elsewhere because you could ignore the self-calibration and take the theoretically motivated belief that the background is 1.0 and then it's about 3.5 sigma. The self-calibrating fit is a kind of cross-check, and since b came out being smaller then 1.0 (the 0.928 ± 0.39 above), that weakens the claim with the full fit down to only 3 sigma.
  • Nobody claims 3 sigma is a discovery, not because it's on the border of plausibility (look at enough data and you'll eventually see some purely statistical 3 sigmas), and they're not claiming it's a discovery, either. It's an "excess." It means we need more data. Some communities take 5 sigma as the threshold for discovery, others don't have a hard-and-fast rule, because even 5 sigma cases can be mistaken due to mistreatment of the data.

So the bottom line is: there's nothing wrong with this data analysis. (I can't speak to the applicability of the data to the claim, because I'm not an expert—just the handling of the data as presented in the paper.) The fit is a kind of cross-check, loosening the native interpretation in which we just assume the baseline is 1.0 to a somewhat-less-native, but best-one-can-hope-to-do-with-these-data three-fit. In fact, the fit weakens the claim and it's still significant.

On the other hand, the result of this analysis is not, "We discovered supernovae!" but "if this holds up with more data, were might discover supernovae!"

It's the popular article that's overstating the claim, not the paper.

[–]whupazz 34 points35 points  (2 children)

Just look at their running average (red line) in the above graph

That's not a running average, that's a gaussian fit. Those are two very different things. I agree that that plot looks suspect at first glance, but your criticism is very strongly worded given that you misunderstand the basic methods used and haven't even read the abstract, which clearly states what the red line is.

The error bars on that low 53Mn value at 1.5 Ma don't come anywhere near it, which means that the analysis is wrong or the error bars are too small.

This is again a misunderstanding of the methods used. For repeated applications of the same measurement procedure, the true value will be within the 1-sigma error bar in 68% of cases. Therefore there absolutely should be points where the error bars don't touch the line, otherwise you've likely overestimated your errors.

You should edit your post.

I would at first glance be suspicious of that plot, too, but I haven't read the paper and I don't think you can make strong claims about the quality of their analysis without a more careful inspection and a thorough understanding of the statistical methods used.

[–]cherbug[S] 4970 points4971 points  (1031 children)

Among all of the hazards that threaten a planet, the most potentially calamitous might be a nearby star exploding as a supernova.

When a massive enough star reaches the end of its life, it explodes as a supernova (SN). The hyper-energetic explosion can light up the sky for months, turning night into day for any planets close enough.

If a planet is too close, it will be sterilized, even destroyed. As the star goes through its death throes, it produces certain chemical elements which are spread out into space.

[–]InspiredNameHere 508 points509 points  (289 children)

The most likely yes, but fairly high on the totem pole on "Things the universe can do to totally ruin your day."

In no particular order: Wandering black holes, wandering stars, wandering planets, False Vacuum decay, Edit: Strange matter (Thanks RunnyMcGun).

Note: FVD and Strange matter are still extremely hypothetical, so hey, they might not actually happen!

Now almost hopefully none of these are common enough to actually threaten our world, but...it's still possible, and they are out there.

[–][deleted] 342 points343 points  (74 children)

Don't forget gamma ray bursts aimed right at the planet.

[–][deleted] 109 points110 points  (127 children)

Someone wanna drop an ELI5 on false vacuum decay?

[–]InspiredNameHere 378 points379 points  (99 children)

Generally speaking, everything in the universe wants to be at the lowest possible energy level; every thing wants to be lazy. Some scientists theorize that there is a lower possible lazy than currently observed in the universe. Should this lazy be correct, than some particles, called Higgs Bosons may spontaneously become this lazy; creating an ever expanding field that forcefully converts every particle in its path to this new unheard of level of lazy. It expands in all directions at the speed of light, and eliminates the relatively active amount of energy in the process, which is currently being used to build things such as atoms, molecules, stars and planets, and you.

At the theoretical point of true lazyness, nothing we understand as matter is possible. If False vacuum decay exists, you won't just die, the matter that creates you doesn't exist anymore.

[–]xiaoli 265 points266 points  (24 children)

And here I am, worried about parking.

[–]dgriffith 121 points122 points  (1 child)

Space is big.

Space is dark.

It's hard to find

A place to park.

[–]dominion1080 64 points65 points  (19 children)

You sound pretty lazy to me. How do we know this hasn't already happened?

[–]helldeskmonkey 91 points92 points  (13 children)

There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory mentioned, which states that this has already happened.

[–]eve222- 25 points26 points  (7 children)

So some kids tripped acid and then 2020 happened?

[–]TistedLogic 11 points12 points  (5 children)

And Douglas Adams was the only one to remember.

[–]Sinavestia 23 points24 points  (1 child)

“You know," said Arthur, "it's at times like this, when I'm trapped in a Vogon airlock with a man from Betelgeuse, and about to die of asphyxiation in deep space that I really wish I'd listened to what my mother told me when I was young."
"Why, what did she tell you?"
"I don't know, I didn't listen.”

[–]phunkydroid 78 points79 points  (23 children)

And you'll never see it coming, as it expands at the speed of light. One microsecond you exist, the next microsecond you don't.

[–]CaptainJAmazing 72 points73 points  (1 child)

Pretty sure I’ve had coworkers made of that material.

Rimshot

[–]KaizokuShojo 20 points21 points  (21 children)

So, my understanding of all this is basic layman, so I'm confused and would like clarification if you're able.

It was my understanding that when something changes state, it was because something acted upon it, and the excess energy/matter was transferred in some regard. If I throw a ball, energy from my arm goes to the ball and makes it go. It's lazy, so it won't "want" to stop and will keep going unless something (gravity, friction, a ball glove closing around it) makes it stop.

So, when the matter/energy gets moved to its "extra lazy" state...what happened to the energy it had?

I get why everything would just not exist, I think, but I'm stuck somewhere understanding this.

[–]iListen2Sound 22 points23 points  (1 child)

Quantum tunneling. In classical physics, there are some pretty self-evident, seemingly unbreakable rules. In that sense, you'd be right: if you had an object on the second floor of your house, you'd need to push it to the stairs to make it go down. What's it gonna do? Pass through the floor? Well with quantum physics, that's actually relatively likely.

Turns out, in the universe's highest zoom level, it's not so much that the regular rules of physics break, just that they're a little bit fuzzier than we thought like how pictures can seem pretty sharp until you zoom in. Anyway, where in regular physics, we would say things don't change state without anything happening to it, in quantum, literally anything can happen it's just a matter of it very, very likely won't but there's always a very, very small chance that it can and when you have a bunch of particles those small chances add up and you'll probably see at least one of them do exactly the thing they're not supposed to.

So if you've got an entire universe worth of stuff and the Higgs field isn't in the lowest possible energy state then it's very scary to consider that maybe it already did the thing it's not supposed to somewhere and we're just waiting for it to get to us.

[–]HighDagger 62 points63 points  (11 children)

The difference here is that we're not talking about the energy that an object has but about the stability of fundamental forces themselves. As theory goes, all 4 fundamental forces and fundamental particles were one and the same at the Big Bang, when the universe was in a super high energy state in what's called "symmetry". As it cooled with expansion, all 4 forces froze out of that original force and the same is true for fundamental particles that exist as excitations in the related fields.

That's the backdrop. And if something like vacuum decay happened and turned out to be true, then physical reality (the laws of physics, the types of possible particles, the forces themselves) would disappear and be rearranged completely because some particle somewhere chanced upon and unlocked this lower energy state.

It's not objects, it's reality itself.

[–]pizza_engineer 23 points24 points  (1 child)

...whoa...

[–]potato_aim87 8 points9 points  (0 children)

Yea dude. This will probably be deleted because it contributes nothing but I'm in the same spot. Contemplating what it even means to be alive right before I try to go to sleep.

[–]MrHall 66 points67 points  (19 children)

some fields in space have a certain amount of energy, if they find a lower energy state they will fall into it, and the change will spread out at the speed of light. all particle interactions will change as soon as it washes over us and we will cease to exist.

the higgs field, for instance, has energy at every point in space. however, it could be in an energy valley, with higher energy states in all adjacent configurations. quantum tunneling means it could spontaneously find a lower energy state on the other side of a "hill" in configurations it couldn't normally move to.

if that happens anywhere in the universe the bubble of new vacuum will spread out and eventually engulf/destroy the whole universe. it might have already happened, it could reach us at any instant and earth would simply dissolve.

Edit: article here - https://cosmosmagazine.com/physics/vacuum-decay-ultimate-catastrophe/

[–]NtARedditUser 25 points26 points  (8 children)

This is analagous to "ice-nine" by Vonnegut?

[–]travellering 24 points25 points  (1 child)

Ice-9 meets the Nothing from Neverending story...

[–]spamzauberer 45 points46 points  (5 children)

Perfect for kicking death anxiety into overdrive 👌🏻

[–]MrHall 29 points30 points  (2 children)

it's a good one. you'd never feel it tho so it doesn't worry me much 🤷‍♂️

[–]Starlord1729 148 points149 points  (40 children)

There is actually a gamma-ray burst candidate pointing right at us.

We’re not completely sure if it will cause a GRB but the plane of rotation is pointing at us

https://www.nature.com/articles/news.2008.653

[–]allenout 196 points197 points  (15 children)

They studied it further and it's actually pointing 30-40 degrees away from us so we are safe.

[–]ellinger 42 points43 points  (4 children)

But like, not really. If you're talking about that Wolf-Rayat star, "right at us" means a super-wide arc, and at its present distance, would miss us by a substantial amount.

[–]Spartacas23 13 points14 points  (8 children)

What exactly is a GRB? Is it similar to a super nova? And I assume if one does hit us it wouldn’t be good

[–]r4zorsoft 47 points48 points  (0 children)

A supernova is strictly a stellar explosion, where as a GRB can be caused by a variety of different events. A star going supernova can cause a GRB if the detonation is energetic enough, but there are even more fascinating causes:

  1. Hypernova - big-bada-boom
  2. Starquake - what#Starquake)
  3. Magnetar flare - dislikes credit cards

There are other causes as well - check out Gamma-ray burst progenitors!

I also think it's pretty cool we are here discussing big explosions while existing in a universe that was created by an explosion so big, it is still going on right now.

[–][deleted] 18 points19 points  (1 child)

A GRB is a Gamma Ray Burst, a big old beam of not good. They form from a few extremely high energy events, like neutron stars merging. The effects vary based on how far away it was started from, but the range to be dangerous is significantly larger than a supernova, though it requires much poorer luck to actually be hit. In general, worst case scenario is Earth loses half its atmosphere, and most/all of the people on that side, and global temperatures skyrocket as the atmosphere spreads across the planet to an overall less effective shield. Many would die, and extinction is a distinct possibility.

[–]FaceDeer 11 points12 points  (2 children)

Are there any such supernova candidates close enough to Earth that their explosion would be harmful, though?

[–]pocket_geek 10 points11 points  (1 child)

It totally messed up Romulus.

[–]kopixop 686 points687 points  (33 children)

Same SuperNova that coinsides with earth extinction events?

https://en.m.wikipedia.org/wiki/List_of_extinction_events

[–]Astromike23PhD | Astronomy | Giant Planet Atmospheres 622 points623 points  (12 children)

Already proposed 18 years ago (Benitez, et al, 2002):

We find that the deposition on Earth of 60Fe atoms produced by these explosions can explain the recent measurements of an excess of this isotope in deep ocean crust samples. We propose that ~2 Myr ago, one of the SNe exploded close enough to Earth to seriously damage the ozone layer, provoking or contributing to the Pliocene-Pleistocene boundary marine extinction.

[–]NationalGeographics 87 points88 points  (11 children)

Is 60 fe, like super iron?

[–]Jaceking11 22 points23 points  (0 children)

It is kind of. It's an isotope, and a rare one at that.

[–]scaradin 40 points41 points  (0 children)

There is an unknown about 2 million years ago that could have been from a super nova

[–]Rootbeer48 614 points615 points  (118 children)

for the person not so familiar. this really is that long ago given the age of the earth?

[–]HammerheadInDisguise 940 points941 points  (112 children)

Earth is 4.6 billion years old. This is very recent in geological time. First human made fire occurred1.5 million years ago, we are very new to earth.

[–]TheStaggeringGenius 248 points249 points  (4 children)

For context, 4.6 billion seconds is about 146 years; 1.5 million seconds is 17 days.

[–][deleted] 62 points63 points  (0 children)

I like this one. Thanks.

[–]chunkycornbread 12 points13 points  (0 children)

This is a very easy to comprehend comparison. Time scales that large are just hard to wrap your head around.

[–]RetardedCrobar1 38 points39 points  (31 children)

When you say human i thought homosapien had been round for top estimates of 250,000 years?

[–]Indianaj0e 113 points114 points  (22 children)

There were "early humans" around for a few million years, using tools, before "anatomically modern humans" became the sole surviving species of that line.

[–]mssngthvwls 81 points82 points  (32 children)

So how would this work, hypothetically speaking?

Would everything we know suddenly illuminate in a fraction of a second and vaporize with a nuclear-like flash? Or, would it gradually get brighter and hotter, signalling to us in a few seconds/minutes/hours/days that something is immensely and imminently wrong?

Or, something else?

[–]sindelic 30 points31 points  (2 children)

I bet we’d get at least 10 minutes

[–]Grarr_Dexx 28 points29 points  (12 children)

The ozone layer evaporates. That's all this planet needs to destroy all carbon-based life forms. The sun is no longer held at bay and we die from radiation damage affecting our DNA.

Edited for correctness.

[–]worldspawn00 16 points17 points  (3 children)

I don't think extra UV from the sun would heat the ocean, there would just be a lot more UV hitting the surface, UV doesn't heat much, the earth has gone through periods with no ozone before, while it damages organic matter, it shouldn't be that much more energy hitting the surface and shouldn't cause a massive rise in water temperature.

[–]noluckatall 67 points68 points  (13 children)

What was the estimated distance of the supernova?

[–]supremedalek925 41 points42 points  (1 child)

Wow, 2.5 million years is EXTREMELY recent relatively speaking

[–]cantsay 57 points58 points  (68 children)

I always wonder if galaxies orbit something the way that stars and planets do, and if so what potential unseen hazards might our galaxy --or galaxy supercluster-- pass through that we wouldn't necessarily see coming?

[–]Aekiel 98 points99 points  (10 children)

They do, possibly. The Great Attractor is the central gravitational point of our supercluster and is pulling on all of the galaxies within it, which likely makes for some extremely large and long orbits.

[–]silent_femme 44 points45 points  (38 children)

From my understanding, galaxies usually hang out with other galaxies in their own clusters, and the biggest hazard they face is a galactic collision with another galaxy, which is what scientists have predicted will happen to the Milky Way galaxy in4.5 billion years when it collided with the Andromeda galaxy.

[–]MarlythAvantguarddog 58 points59 points  (35 children)

Yes but nothing hits nothing. The spaces between things in space are so large that while gravity will disrupt large scale structures, it is not as if suns fall into each other or planets merge.

[–]Decapitated_Saint 45 points46 points  (13 children)

Andromeda will be super cool looking for anyone alive in the galaxy just before the merger begins. It'll be like at the end of Empire strikes back.

[–]mrcmnstr 21 points22 points  (1 child)

Talking about the final plot on the page:

Above: The merged data from all four sampling areas. The C/C0 on the vertical axis represents the 53Mn/Mn ratios measured in the samples. There's a clear spike at the 2.5 million years ago mark.

People only talk about how "clear" their conclusions are when there is real doubt about them. It's like how text book authors only say something is obvious when either they are too lazy to prove it, or it is not obvious at all and they don't want you questioning it right now.

[–]Morguard 9 points10 points  (4 children)

Do we know the max distance for a supernova that we know would effect us?