[HN Gopher] Mars Has Influence on Earth's Oceans and Climate, Re...
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Mars Has Influence on Earth's Oceans and Climate, Repeating Every
2.4M Years
Author : pseudolus
Score : 122 points
Date : 2024-03-17 13:44 UTC (9 hours ago)
(HTM) web link (www.smithsonianmag.com)
(TXT) w3m dump (www.smithsonianmag.com)
| AndrewKemendo wrote:
| The paper for this was published a few days ago here to no
| response:
|
| https://news.ycombinator.com/item?id=39729053
|
| Admittedly I struggled on my first read through, but it's one of
| the bigger discoveries in climate research in a while
|
| It might give us some answers on why the Younger-Dryas happened
| argubly leading to the Quaternary Extinction event, as there's
| some dissent around the causes
|
| If it was a concurrent epicycle that stacked up that could be a
| pretty compelling argument
|
| https://en.m.wikipedia.org/wiki/Younger_Dryas
| jimmytucson wrote:
| Jury is still out on an astronomical explanation for the apparent
| 26M year periodicity[0] of mass extinction events. Lisa Randall
| has an entertaining theory[1] that it's due to the sun passing
| through dark matter in its orbit around the galaxy.
|
| [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC344925/
|
| [1]
| https://en.m.wikipedia.org/wiki/Dark_Matter_and_the_Dinosaur...
| indigobunting wrote:
| Except that the orbital period around the galaxy is ~230M
| years.
| __MatrixMan__ wrote:
| Maybe dark matter bodies orbit faster.
| exe34 wrote:
| Orbital speed is a fixed function of central mass and
| distance from that mass.
| thfuran wrote:
| In theory. On the other hand, dark matter is pretty much
| just a name we give to a discrepancy in current theory.
| 4ad wrote:
| No, that is dark energy.
|
| From the pov. of gravity dark matter is simply regular
| matter that we can't see.
| exe34 wrote:
| Not quite. Dark matter is the hypothesis that the
| discrepancy between theory and observation is due to a
| form of matter that interacts gravitationally but not
| electromagnetically. So we can't see it, and thus "dark".
|
| There are other competing ideas including a family of
| modified Newtonian dynamics models, but nothing comes as
| close as explaining the observations as dark matter does.
|
| There was a paper recently that showed that the
| discrepancy may be the higher order terms from general
| relativity that is often neglected because they are
| believed to be small - but that idea still needs to be
| proven to work for a large variety of cases.
|
| The observations in question for this Dark matter
| hypothesis include the rotation velocity of stars in
| galaxies and a few other things like gravitational
| lensing.
|
| Dark energy is a different discrepancy with theory. It's
| a term that we have to add to Einstein's field equations
| to account for the observation that the universal
| expansion is accelerating instead of slowing down. Again
| there are competing hypotheses, like non uniform density
| on the largest scales, but nothing quite explains
| everything as dark energy.
| thfuran wrote:
| I don't think that's really an accurate description.
| There's a discrepancy between observations relating to
| gravitation and general relativity's predictions. The
| discrepancy could be accounted for by significant extra
| mass, but no non-gravitational observations seem to
| confirm the presence of that extra mass. So "dark matter"
| is the supposition that there's a significant amount of
| extra mass that interacts only with gravity but not, for
| example, light, making it categorically different from
| ordinary matter. And I don't think there's any evidence
| that this dark matter follows the same gravitational
| constant as ordinary matter.
| adrian_b wrote:
| It does not matter whether it "follows the same
| gravitational constant as ordinary matter" or not.
|
| For any kind of matter, normal or "dark", which is
| observed only through gravitational effects, you cannot
| determine separately its mass and the gravitational
| constant that applies to it. You can determine only the
| product between mass and gravitational constant (which is
| the cause of measurable forces).
|
| Therefore for many astronomical objects the product
| between their mass and the gravitational constant is
| known with a much greater precision than their mass
| (because the gravitational constant is known with very
| poor precision even for ordinary matter).
|
| The same applies for "dark matter". You cannot compute
| the distribution in space of the mass of the dark matter,
| but only the distribution in space of the product between
| its mass and whatever gravitational constant is
| applicable to it.
|
| So even if a different gravitational constant were
| applicable to "dark matter" that fact would be irrelevant
| for any mathematical model that is fitted to the
| observations.
| thfuran wrote:
| Nevertheless, mass is a separate quantity, which means
| that the original claim that orbital speed is determined
| solely by mass and orbital radius is not supportible in
| the context of dark matter.
| exe34 wrote:
| You could oscillate up and down across the orbital plane many
| times during one orbit. Not saying that's what's happening
| here, but it's a possibility.
| ckcheng wrote:
| That's the argument I think. Per that Wikipedia link:
|
| > Randall hypothesizes a plane of dark matter exists
| roughly on the plane of the Milky Way galaxy. As the Sun
| oscillates in its orbit around the center of the galaxy, it
| passes through the dark matter.
| exe34 wrote:
| Ah that's probably where I learnt it from then!
| jagged-chisel wrote:
| What would cause the oscillation?
| roywiggins wrote:
| If you're not smack bang in the middle of the galactic
| plane, you're going to be accelerated towards it by
| gravity, so you'll tend to bob up and down, like a
| pendulum.
| cwillu wrote:
| I'm not sure I buy that the oscillation around the plane
| can have a period other than the orbital period.
| mattsan wrote:
| I haven't done the math but I would think it's possible
| due to interactions from other solar systems. Similar to
| how satellites oscillate around Lagrange points
| exe34 wrote:
| The up down oscillation is completely decoupled from the
| orbit itself, assuming the orbital potential is uniform.
| It's like the galaxy wasn't rotating at all. You put
| something above the disk, and it gets accelerated
| downwards, but doesn't stop at the disk, it keeps going,
| until it gets dragged back up. Think of it like a
| pendulum.
| partitioned wrote:
| do you think motion in X is always dependent on motion in
| Y?
| frutiger wrote:
| It doesn't even have to be dark matter, most of the (non-dark)
| galactic mass is in the galactic plane and the sun oscillates
| up and down passing through the plane as it orbits the centre.
| api wrote:
| That's just how often the local dark forest reaper aliens fire
| a relativistic velocity impactor at every biosphere they can
| detect within range. Keep resetting to make sure nothing too
| complex evolves.
|
| How much longer do we have to bug out before the next one?
| ilove_banh_mi wrote:
| Having read the Nature article [0] it looks like we're near a
| local maximum of that cycle [1].
|
| [0] https://www.nature.com/articles/s41467-024-46171-5
|
| [1] https://www.nature.com/articles/s41467-024-46171-5/figures/2
| vincengomes wrote:
| Man, this study is going to be paraded as the proof that
| astrology is scientific and ancient people were more
| knowledgeable than us.
| icepat wrote:
| You are being downvoted, but it is completely true. This is
| going to be used in the gurusphere in the way Deepak Chopra
| abuses the language of quantum physics to justify quackery.
| While things like this are always interesting, part of me can't
| help be be depressed knowing it's going to go into the firehose
| of nonsense we're being sprayed by every day.
|
| It's happening in this very thread in a few places already...
| readyplayernull wrote:
| People is born in seasons, constellations and planets appear
| in seasons, and so ancient smart people made a connection.
|
| Then the largest actor interested in destroying Astrology is
| the Catholic Church for reasons. The church also had wrong
| astronomical theories. Science evolved, but we inherited a
| dead horse to beat.
| ghthor wrote:
| The ancients were more knowledgeable then us.
|
| https://youtu.be/J6OsDczx5iM?si=2BcthvU-6X_svTmw
| ghthor wrote:
| I'm sure the Down voters watched the entire lecture I linked
| before casting their votes. /s
| pfannkuchen wrote:
| Astrology is misunderstood today IMO.
|
| Cycles exist on Earth. Cycles exist in astral bodies. If an
| astral cycle aligns with some earth cycle, you can legitimately
| use the astral cycle to track the earth cycle. There is nothing
| wrong with doing this, it's a useful tool.
|
| The problem came when people confused correlation with
| causation. There's also some spurious correlations used as well
| as some scale extrapolation issues.
|
| But what was probably the root mechanism is sound. That is why
| ancients seem so weirdly obsessed with the stars, it actually
| works in some cases (non causally of course).
| bamboozled wrote:
| _ancient people were more knowledgeable than us._
|
| Almost sounds like a phobia.
|
| I do think ancient people seem to have displayed more wisdom
| than us. We're the brainiacs.
| aaomidi wrote:
| Definitely more wise, even if accidental.
|
| More knowledgeable? No
| dakom wrote:
| Asimov and Silverberg's Nightfall novel seems related- a great
| sci-fi story about a civilization on an alien planet that isn't
| prepared for the long cycle of astronomical movements (they go
| crazy during an eclipse every 2000 years or so). Fun read :)
| KineticLensman wrote:
| Asimov and Silverberg confused me for a moment - Nightfall was
| an Asimov-only short story from 1941. Still think it's one of
| his best. TIL there was a collaborative novel as well, which
| carried on after the events of the short story.
|
| * * *
|
| If you like novels that explore civilisations that have long
| astronomical cycles, the other classic is the Helliconia
| trilogy by Brian Aldiss. It's set in a double star system where
| the main planetary orbit takes 2500 Earth years, and the
| seasons last for Earth centuries. Civilisation tends to
| collapse when winter comes, but gradually approaches semi-
| industrial levels of technology by autumn.
| a_gnostic wrote:
| Milankovitch cycles describe the collective effects of changes in
| the Earth's movements on its climate over thousands of years. The
| term was coined and named after the Serbian geophysicist and
| astronomer Milutin Milankovic. In the 1920s, he hypothesized that
| variations in eccentricity, axial tilt, and precession combined
| to result in cyclical variations in the intra-annual and
| latitudinal distribution of solar radiation at the Earth's
| surface, and that this orbital forcing strongly influenced the
| Earth's climatic patterns.[1]
|
| 1] https://en.m.wikipedia.org/wiki/Milankovitch_cycles
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