[HN Gopher] Earth Has a 27.5M-Year 'Heartbeat', but We Don't Kno...
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Earth Has a 27.5M-Year 'Heartbeat', but We Don't Know What Causes
It
Author : CarCooler
Score : 76 points
Date : 2021-06-22 15:36 UTC (7 hours ago)
(HTM) web link (www.sciencealert.com)
(TXT) w3m dump (www.sciencealert.com)
| dzdt wrote:
| Looks like bogus statistics to me. (Caveat: I only read the
| sciencealert link not the underlying publication). But with a
| sample of 89 "events" over a purported 10-cycle period we are in
| the small sample realm where it is easy to get spurious apparent
| relationships.
|
| People love to see patterns, and if you aren't really careful you
| can "prove" a pattern in essentially random data.
| nosianu wrote:
| If you had read the article you would have been informed that
| this publication is one in a long line of similar ones going
| back as far as 1920 who all came to similar numbers.
|
| You are right, if there was only this one paper it would be
| entirely unremarkable and informing the general public would be
| wrong. But that is not the case because the article fortunately
| does not limit itself to pointing to just that publication.
| SeanLuke wrote:
| Just because everyone's seeing the same pattern in random
| data doesn't mean there's a pattern at all. For very good
| evolutionary reasons, humans are extraordinarily good
| pattern-recognition machines: we see ghosts in data when
| nothing exists. Our collective false positives are quite
| high.
| wrycoder wrote:
| Underlying:
|
| https://www.sciencedirect.com/science/article/pii/S167498712...
| chris_va wrote:
| Section 3.3 there, the Fourier analysis, looks really weak.
|
| If you just plot 89 random numbers between 0 to 270 it'll
| have strong spectral peaks. Their method:
|
| > _After permuting the order of the intervals, a new time
| series was re-calculated based on the new set of intervals.
| This method ensures that the test time series are between 0
| and 260 Ma and the number of events remains at 89.
| Ultimately, only ~ 4% of the test datasets produced a higher
| spectral power at 27.5 Myr, indicating a confidence level of
| at least 96% for that period._
|
| ... seems very fishy to me. I could believe that the spectral
| power at that frequency is the mode in the data. I don 't see
| a proof that the particular spectral power associated with
| 27.5 is statistically significant given a random set of
| events.
| brylie wrote:
| Could this be related to our solar system orbiting through our
| galaxy?
| eloff wrote:
| I saw two independently published papers the other day showing a
| 27.5M year cycle. One was this paper talking about cycles in
| volcanic activity, another was talking about mass extinctions.
| Article here: https://phys.org/news/2020-12-mass-extinctions-
| land-dwelling... . I'm going to hazard a guess that the former is
| very likely a direct cause of the latter. We suspect this to be
| true of most of the worst mass extinctions, like the Permian
| extinction. With the dinosaurs it might have been the Chicxulub
| asteroid impact, or that might have merely been the finishing
| blow to a system under severe stress from the Decan Traps flood
| basalt eruptions in India that had been underway for millions of
| years by that point. There are plenty of indications that species
| were declining well before the impact.
|
| The solar system takes 230 million years to make one complete
| orbit around the Milky Way, so I don't think this is likely
| caused by our passage through the galaxy. It's more likely an
| internal rhythm in activity deep within the Earth.
| sliken wrote:
| I believe the solar system actually cycles from below the plane
| of the galaxy to above the plane of the galaxy. I've heard
| numbers between 25M years and 40M years. Debris on that plane
| could shake comets loose from the oort cloud. Other theories on
| dark matter support the idea that crossing through dark matter
| could increase the temperature in the cores of planets, leading
| to increased seismic activity.
| eloff wrote:
| Those are good points. Maybe it does have to do with our
| galactic orbit.
| tejtm wrote:
| In addition to the galactic orbit the disk itself has it's
| own local gravitational pull that keeps stars in the plane
| by pulling up/down when a stars trajectory takes it
| below/above the local disk. When we are out of the plane we
| loose the protective cover all the shielding the disk
| provides from the galactic core (electrons go zing). When
| in the middle of the disk there is a higher density of
| mater to interact with (rocks go boom). Our typical
| exposure to "orbits" earth & moon tends to be that they are
| roundish flat & smooth and we might be tempted to think the
| suns orbit around the galactic core is smooth, but it may
| be better to think of us as also bobbing up and down the
| highth of the disk as we go.
| contravariant wrote:
| I wouldn't be too quick in dismissing the Galaxy. The galaxy
| isn't uniform so something could easily be related to one of
| the harmonics. And 27.5M years happens to be quite close 1/8th
| of a galactic year, so something to do with the earth passing
| in/out galactic arms or similar is not out of the question.
| _ah wrote:
| To be slightly pedantic: our sun is a star in the galaxy, so
| as the entire galaxy rotates we would not pass in and out of
| a galactic arm. We would rotate with it.
| jazzyjackson wrote:
| Not pedantic at all, I for one have never speculated about
| galactic dynamics
|
| So in the solar system the inner planets have faster orbits
| than the outer planets, I assume it would be the same on a
| galactic level - if we're a slow poke out on the edge,
| could there be some region of the galaxy that orbits the
| core 8x faster than us such that we're periodically
| effected by it?
|
| Edit LOL my sibling comments have filled in some info for
| me on the mean time
| lasc4r wrote:
| Maybe not.
| https://en.wikipedia.org/wiki/Density_wave_theory
| wlesieutre wrote:
| The galaxy isn't a rigid spinning object though, it's
| composed of many stars acting under gravitational
| influences. Like our solar system, objects closer in will
| orbit faster than objects further out. Rather than fixed
| structures, the arms are more like a standing wave of
| greater density.
|
| Some related links
|
| https://en.wikipedia.org/wiki/Density_wave_theory
|
| https://en.wikipedia.org/wiki/Galaxy_rotation_curve
|
| https://www.nature.com/articles/s41550-018-0627-5
| mjw1007 wrote:
| As I understand it, galaxies don't rotate like rigid
| bodies: stars further from the centre take longer to go
| round than ones closer in, much like planets further from
| the sun take longer to complete an orbit.
|
| If stars that start off inside an arm remain so, but the
| outer part of the arm goes round more slowly, the arm would
| get wound 'tighter' as time goes on, and this doesn't seem
| to happen.
|
| I think what's really going on isn't yet well understood,
| but it's likely to be that the arms are something more like
| a standing pattern, and stars do indeed move in and out of
| the arms as time goes on (something like the way a traffic
| jam can move more slowly than the individual cars that it's
| made of).
| _ah wrote:
| Fair point. So maybe we should say that our sun would
| occasionally be a part of the galactic arm as the pattern
| morphs and re-forms. A fun concept.
| ananonymoususer wrote:
| It turns out that the stars further from the center don't
| take as long as one might think. Observations of this
| phenomenon led to the development of the theory of dark
| matter.
|
| https://en.wikipedia.org/wiki/Galaxy_rotation_curve
| [deleted]
| mensetmanusman wrote:
| I like the idea that it is a slow charge buildup from galactic
| ambient high energy rays.
|
| These would cause a very slow charge build up, and the piezo
| electric effect of the earth would come into play. E.g. a very
| slow quartz crystal clock cycle.
| nn3 wrote:
| For mass extinctions there is the common explanation that it
| takes a long time after each extinction before enough diversity
| is built up again for another major extinction.
|
| For example after the current Anthropocene one we likely won't
| have another one any time soon because there is not enough
| diversity left for a true mass extinction.
|
| That gives a natural effect where mass extinctions are spaced
| with some minimum interval. They're not independent events.
| abc_lisper wrote:
| That's a great point. But it's not necessary for the events to
| be periodic.
| mistrial9 wrote:
| on the other hand, it is well-known in medical science that
| people who have say, a serious traumatic brain injury (TBI),
| are far more likely to get many other serious injuries soon
| afterwards and also at high risk for a long time afterwards for
| another TBI.
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