{"id":89542,"date":"2023-01-24T19:43:00","date_gmt":"2023-01-25T01:43:00","guid":{"rendered":"https:\/\/milesfortis.com\/?p=89542"},"modified":"2023-01-24T19:43:00","modified_gmt":"2023-01-25T01:43:00","slug":"89542","status":"publish","type":"post","link":"https:\/\/milesfortis.com\/?p=89542","title":{"rendered":""},"content":{"rendered":"

Earth\u2019s inner core may be reversing its rotation<\/a><\/p>\n

Our planet may have had a recent change of heart.<\/p>\n

Earth\u2019s inner core\u00a0may have temporarily stopped rotating<\/a>\u00a0relative to the mantle and surface, researchers report in the January 23\u00a0Nature Geoscience<\/em>. Now, the direction of the inner core\u2019s rotation may be reversing \u2014 part of what could be a roughly 70-year-long cycle that may influence the length of Earth\u2019s days and its magnetic field \u2014 though some researchers are skeptical.<\/p>\n

\u201cWe see strong evidence that the inner core has been rotating faster than the surface, [but] by around 2009 it nearly stopped,\u201d says geophysicist Xiaodong Song of Peking University in Beijing. \u201cNow it is gradually mov[ing] in the opposite direction.\u201d<\/p>\n

Such a profound turnaround might sound bizarre, but Earth is volatile<\/a>\u00a0(SN: 1\/13\/21<\/em>). Bore through the\u00a0ever-shifting<\/a>\u00a0crust and you\u2019ll enter the titanic\u00a0mantle<\/a>, where behemoth masses of rock flow viscously over spans of millions of years, sometimes\u00a0upwelling<\/a>\u00a0to excoriate the overlying crust (SN: 1\/11\/17, SN: 3\/2\/17, SN: 2\/4\/21<\/em>). Delve deeper and you\u2019ll reach Earth\u2019s liquid outer core. Here, circulating currents of molten metals conjure our planet\u2019s\u00a0magnetic field<\/a>\u00a0(SN: 9\/4\/15<\/em>). And at the heart of that melt, you\u2019ll find a revolving, solid metal ball about 70 percent as wide as the moon.<\/p>\n

<\/p>\n

This is the\u00a0inner core<\/a>\u00a0(SN: 1\/28\/19<\/em>). Studies have suggested that this solid heart may rotate within the liquid outer core, compelled by the outer core\u2019s magnetic torque. Researchers have also argued the mantle\u2019s immense gravitational pull may apply an erratic brake on the inner core\u2019s rotation, causing it to oscillate.<\/p>\n

Evidence for the\u00a0inner core\u2019s fluctuating rotation first emerged in 1996<\/a>. Geophysicist Paul Richards of Columbia University\u2019s Lamont-Doherty Earth Observatory in Palisades, N.Y., and Song, then also at Lamont-Doherty, reported that over a span of three decades, seismic waves from earthquakes took different amounts of time to traverse Earth\u2019s solid heart.<\/p>\n

The researchers inferred that the inner core rotates at a different speed than the mantle and crust, causing the time differences. The planet spins roughly 360 degrees in a day. Based on their calculations, the researchers estimated that the inner core, on average, rotates about 1 degree per year faster than the rest of Earth.<\/p>\n

But other researchers have questioned that conclusion, some suggesting that the core spins slower than Song and Richards\u2019 estimate or doesn\u2019t spin differently at all.<\/p>\n

In the new study, while analyzing global seismic data stretching back to the 1990s, Song and geophysicist Yi Yang \u2014 also at Peking University \u2014 made a surprising observation.<\/p>\n

Before 2009, seismic waves generated by sequences and pairs of repeating earthquakes \u2014 known as multiplets and doublets \u2014 traveled at different rates through the inner core. This indicated the waves from recurring quakes were crossing different parts of the inner core, and that the inner core was rotating at a different pace than the rest of Earth, aligning with Song\u2019s previous research.<\/p>\n

But around 2009, the differences in travel times vanished. That suggested the inner core had ceased rotating with respect to the mantle and crust, Yang says. After 2009, these differences returned, but the researchers inferred that the waves were crossing parts of the inner core that suggested it was now rotating in the opposite direction relative to the rest of Earth.<\/p>\n

The researchers then pored over records of Alaskan earthquake doublets dating to 1964. While the inner core appeared to rotate steadily for most of that time, it seems to have made another reversal in rotation in the early 1970s, the researchers say.<\/p>\n

Song and Yang infer that the inner core may oscillate with a roughly 70-year periodicity \u2014 switching directions every 35 years or so. Because the inner core is gravitationally linked to the mantle and magnetically linked to the outer core, the researchers say these oscillations could explain known 60- to 70-year variations in the length of Earth\u2019s days and the behavior of the planet\u2019s magnetic field. However, more work is needed to pin down what mechanisms might be responsible.<\/p>\n

But not all researchers are on board. Yang and Song \u201cidentif[y] this recent 10-year period [that] has less activity than before, and I think that\u2019s probably reliable,\u201d says geophysicist John Vidale of the University of Southern California in Los Angeles, who was not involved in the research. But beyond that, Vidale says, things get contentious.<\/p>\n

In 2022, he and a colleague reported that\u00a0seismic waves from nuclear tests<\/a>\u00a0show the inner core may reverse its rotation every three years or so. Meanwhile, other researchers have proposed that the inner core isn\u2019t moving at all. Instead, they say,\u00a0changes to the shape of the inner core\u2019s surface\u00a0<\/a>could explain the differences in wave travel times.<\/p>\n

Future observations will probably help disentangle the discrepancies between these studies, Vidale says. For now, he\u2019s unruffled by the purported chthonic standstill. \u201cIn all likelihood, it\u2019s irrelevant to life on the surface, but we don\u2019t actually know what\u2019s happening,\u201d he says. \u201cIt\u2019s incumbent on us to figure it out.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Earth\u2019s inner core may be reversing its rotation Our planet may have had a recent change of heart. Earth\u2019s inner core\u00a0may have temporarily stopped rotating\u00a0relative to the mantle and surface, researchers report in the January 23\u00a0Nature Geoscience. Now, the direction of the inner core\u2019s rotation may be reversing \u2014 part of what could be a … Continue reading “”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[55],"tags":[],"class_list":["post-89542","post","type-post","status-publish","format-standard","hentry","category-they-made-a-movie-about-this"],"_links":{"self":[{"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/posts\/89542","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/milesfortis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=89542"}],"version-history":[{"count":1,"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/posts\/89542\/revisions"}],"predecessor-version":[{"id":89543,"href":"https:\/\/milesfortis.com\/index.php?rest_route=\/wp\/v2\/posts\/89542\/revisions\/89543"}],"wp:attachment":[{"href":"https:\/\/milesfortis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=89542"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/milesfortis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=89542"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/milesfortis.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=89542"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}