Una variación de apenas unos milímetros puede alterar un punto de referencia esencial para los satélites que orbitan el planeta. El desplazamiento estacional del agua, el hielo y el aire mueve el centro de masa de la Tierra respecto de su centro geométrico, según una investigación liderada por científicos del Laboratorio de Propulsión a Chorro de la NASA en California.

El fenómeno no modifica la forma visible del planeta ni supone un cambio brusco en su rotación. Aun así, importa para los sistemas que requieren una localización precisa desde el espacio, como la navegación por satélite, la elaboración de mapas y las mediciones de altitud. El estudio, publicado en la revista Geophysical Journal International, plantea además que el movimiento anual es menor de lo calculado en estimaciones anteriores.

La Tierra no es una esfera rígida y homogénea. La acumulación de nieve, las lluvias, el desplazamiento de agua entre continentes y océanos, la pérdida de hielo y los cambios en la atmósfera redistribuyen grandes cantidades de masa a lo largo del año.

Esa redistribución provoca que el geocentro, el punto que representa el centro de masa del planeta, se desplace respecto del centro geométrico. En términos sencillos, el centro geométrico sería el punto medio de una esfera perfecta; el centro de masa, en cambio, depende de dónde se concentra el peso de todo lo que compone la Tierra.

Los movimientos llegan a varios milímetros, una distancia reducida para la vida cotidiana, pero relevante para instrumentos que calculan posiciones desde miles de kilómetros de altura. La NASA indicó que dos estimaciones internacionales realizadas en 2017 y 2023 diferían en siete milímetros, una brecha casi equivalente a la magnitud del fenómeno que buscaban medir.

Por ese motivo, el equipo encabezado por el geocientífico Donald Argus, del Laboratorio de Propulsión a Chorro de la NASA (JPL), desarrolló un método destinado a reducir la incertidumbre.

“Ahora calculamos que el desplazamiento anual del centro de masa de la Tierra es cerca de la mitad de lo que creíamos hace ocho años”, afirmó Argus. El investigador añadió que los resultados sugieren que el volumen de agua y aire que se traslada entre hemisferios es menor de lo supuesto hasta ahora.

La nieve del hemisferio norte desplaza el geocentro hacia el Polo Norte

La investigación agrupó las causas de la oscilación anual en tres grandes categorías: océanos, atmósfera y agua continental. Esta última incluye los glaciares, la nieve, los ríos, los lagos, la humedad del suelo y las reservas de agua subterránea.

Uno de los cambios más claros ocurre en marzo. Durante ese mes, la acumulación de nieve en América del Norte y Eurasia alcanza su nivel máximo. Esa carga adicional de agua congelada mueve el centro de masa terrestre unos tres milímetros hacia el Polo Norte.

El patrón cambia semanas después. En abril, la cantidad de agua asociada a las precipitaciones en la cuenca del Amazonas llega a un máximo estimado de 2.400 gigatoneladas. Una gigatonelada equivale a mil millones de toneladas. Ese aumento de masa desplaza el geocentro alrededor de 2,2 milímetros hacia América del Sur.

Las lluvias monzónicas del sudeste asiático también forman parte de la oscilación. En noviembre, el agua vinculada al monzón alcanza unas 600 gigatoneladas en la región y aporta un componente adicional al ciclo anual.

El estudio no plantea que el planeta cambie de posición en el espacio. Lo que varía es la ubicación interna de su punto de equilibrio, como consecuencia de la distribución desigual de masas sobre la superficie y debajo de ella.

El océano Pacífico tiene un peso particular en esta dinámica debido a su extensión. Entre agosto y octubre, el agua procedente del deshielo y de las lluvias hace que el nivel del mar aumente en distintas áreas oceánicas, con un efecto que lleva el centro de masa de la Tierra hacia el Pacífico Sur.

Los autores observaron que las variaciones de masa en ese océano superan los cambios registrados en otras cuencas. Los mares Mediterráneo, Rojo, del Norte, Báltico y de Barents también influyen, aunque con una contribución menor.

El aire frío del invierno también altera el equilibrio del planeta

La atmósfera participa en el desplazamiento del centro de masa. El aire frío es más denso que el cálido, por lo cual concentra más masa en las regiones donde se acumula durante el invierno.

Con un modelo elaborado por el Centro Europeo de Previsiones Meteorológicas a Medio Plazo, los investigadores estimaron el efecto de esas variaciones. Los cálculos indican que el aire invernal, frío y denso, contribuye a desplazar el equilibrio sobre Arabia, Asia y el norte de África cerca del 21 de diciembre. Un patrón comparable ocurre alrededor del 21 de junio sobre América del Sur y Sudáfrica.

Felix Landerer, coautor del trabajo e investigador del JPL, sostuvo que la escala reducida de estos movimientos no disminuye su importancia para las tecnologías actuales. “Aunque estos movimientos puedan parecer insignificantes, nuestro mundo moderno depende de mediciones de posicionamiento extremadamente precisas”, señaló.

Landerer explicó que una mejor comprensión de los procesos que alteran los sistemas de referencia puede mejorar la cartografía y la navegación. Entre las aplicaciones mencionó la logística marítima global y la agricultura de precisión.

Satélites láser y GPS permitieron mejorar la medición

Para calcular el geocentro, los científicos combinaron distintos sistemas de observación. Una de las herramientas centrales fueron los satélites LAGEOS 1 y LAGEOS 2, lanzados en 1976 y 1992. Ambos poseen reflectores que permiten medir con láser su distancia respecto de estaciones terrestres distribuidas en más de 20 países.

Los satélites orbitan alrededor del centro de masa de la Tierra debido a la gravedad. Por eso, una modificación pequeña en la distancia que los separa de una estación terrestre puede revelar un cambio en la ubicación del geocentro.

El nuevo método incorporó datos de GPS y observaciones orbitales de varios satélites de órbita baja. También incluyó un aspecto que podía distorsionar los cálculos: el peso del agua y del hielo deforma la corteza terrestre y desplaza levemente las estaciones de medición.

La investigación comparó sus resultados con las observaciones de la misión Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), integrada por dos satélites gemelos lanzados en 2018. La misión detecta variaciones mensuales en la gravedad terrestre, que reflejan sobre todo el movimiento de grandes masas de agua.

El trabajo apunta a perfeccionar los sistemas de referencia usados para medir un planeta cuya masa nunca permanece exactamente en el mismo lugar.

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President Donald Trump’s crackdown on government fraud is getting unexpected backup from a majority of House Democrats, including Minority Leader Hakeem Jeffries, D-N.Y.

More than 140 House Democrats voted with all Republicans to make the National Fraud Enforcement Division permanent on Wednesday. The bill passed in an overwhelming 352 to 72 vote, with all of its opponents being Democrats as well.

Trump’s White House first announced the creation of a new division within the Department of Justice (DOJ) to combat fraud in January 2026, primarily targeting «fraud affecting the federal government, federally funded programs, and private citizens,» according to a release by the administration.

It was notably used as a cudgel against Trump’s political enemies earlier this year, when Vice President JD Vance referred Minnesota Gov. Tim Walz and state Attorney General Keith Ellison to the fraud division for a potential criminal investigation.

WHITE HOUSE PUSHES ‘WATERSHED’ FRAUD-FIGHTING REFORM IN CONGRESS AS VANCE CONVENES TASK FORCE

Republicans accused Walz and Ellison of helping facilitate what’s become a ballooning fraud scandal affecting Minnesota’s social welfare programs. Both have acknowledged that taxpayer dollars were taken advantage of but accused GOP actors of casting the situation as worse than it actually is as a political attack.

VANCE REFERS TIM WALZ, MINNESOTA ATTORNEY GENERAL TO DOJ FOR CRIMINAL INVESTIGATION OVER STATE’S ALLEGED FRAUD

The Trump administration’s announcement of the fraud division also touted its actions in Minnesota, which it said was experiencing a «fraud epidemic.»

Rep. Jamie Raskin, D-Md., a top House progressive, said he would give «tepid support» to the legislation, while pointing out a fraud division has already existed within the DOJ for decades.

REPUBLICANS DECLARE WAR ON ‘ORGANIZED THEFT’ WITH GOVERNMENT FRAUD CRACKDOWN

«This is hardly some kind of great breakthrough in law enforcement or criminal justice, but it is perhaps the least offensive piece of legislative flotsam and jetsam that has washed ashore in the last 48 hours of Republican chaos and retreat here in the House of Representatives,» Raskin said on the House floor.

Rep. Jeff Van Drew, R-N.J., responded, «This conversation is about a piece of legislation. It’s about a piece of legislation that we want to be enacted into law. It’s not a partisan initiative. It’s a permanent, nonpartisan commitment that we do something better because the people who are listening here … the people who are watching, they’re getting tired of it.»

«They’re getting tired of all the money that has been wasted. And to try to pretend that just a few years ago, a couple of years ago, everything was perfect, everything was taken care of and that there was no corruption, we know better,» Van Drew said.

Raskin spent a significant amount of time accusing Trump and his administration allies of corruption at the expense of prosecuting actual fraud cases, something Republicans pushed back against.

«What has come out of Minnesota over the last year, what has been exposed, is absolutely criminal in nature,» said Rep. Harriet Hageman, R-Wyo. «I think what is coming, what is being exposed in blue cities and blue states run by Democrats, demonstrates that it’s probably higher by an order of magnitude.»

Raskin then targeted Van Drew directly in his comments: «My dear friend from New Jersey wants to make it sound like I’m doing something partisan. I’m joining his bill.»

«It would be very easy for me to say I reject everything you do because you’re on the side of this pro-fraud president, but I’m not doing that. Your bill says, let’s call this the ‘National Fraud Enforcement Unit. I say, fine, that makes sense to me,» Raskin said. «Why don’t you cross the aisle and say it’s wrong for them to be pardoning white-collar fraudster after white-collar fraudster, or at least pardoning them from having to pay the fines and the restitution back? It’s an honest question. Do you really think that $1.7 billion should go from what was going to be the pockets of the victims back into the bank account of the perpetrators?»

Van Drew responded, «The gentleman has his numbers. He has his vision, he has his partisan ideas, and that’s up to him. But I’m trying to point out today … we’re trying to make something that is right now just an executive order and make it law to help the people.»

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Former Vice President Kamala Harris is set to join Michigan Democratic Senate nominee Abdul El-Sayed at an upcoming roundtable in Michigan, according to his campaign.

The two will appear at a Black maternal health roundtable next Tuesday, raising questions about whether Harris might be trying to court the progressive wing of the party in preparation for a 2028 presidential run.

«I’m just really looking forward to having her here, and she is somebody who so many folks in communities like Detroit look up to as an inspirational leader,» El-Sayed told Politico in an interview on Wednesday.

DEMOCRATS’ CIVIL WAR HEADS TO MICHIGAN WHERE PROGRESSIVES FACE BIGGEST TEST YET IN HIGH-STAKES SENATE SHOWDOWN

«I’m grateful that she’s coming in and having conversations about what it takes to get the turnout up, so that we can get on to working on some of these issues in the U.S. Senate,» he continued.

The scheduled roundtable comes after Harris endorsed El-Sayed last month, praising his stance on issues like affordability.

«Dr. Abdul El-Sayed understands the power is with the people, and that the stakes couldn’t be higher in this election. While Michiganders struggle to afford everyday essentials — housing, gas, groceries, health care and child care — Trump and Republicans in Congress are giving away $1 trillion in tax breaks to the wealthy and powerful,» Harris wrote.

«Abdul knows that we need bold solutions to the crises facing America’s working families and he is ready to take on this fight,» Harris continued. «I proudly stand with him to ensure we win a Democratic Senate majority in Nov.»

The news of Harris’ upcoming visit to Michigan comes as The Detroit News, a prominent Michigan newspaper, endorsed El-Sayed’s Republican rival, Mike Rogers, for Senate on Wednesday.

«Mike Rogers is the prototype of a United States Senator,» the paper said in its endorsement, referencing his 14 years in the House, Army career, and private sector experience dealing with cybersecurity.

On the other hand, the paper skewered El-Sayed for his radical rhetoric, saying he «has worked so hard covering his tracks leading up to this Senate race that it’s impossible to know who he really is or where he would stand in the Senate.»

«He has deleted social media posts that reportedly called into question his attitude about America in the aftermath of the 9/11 terrorist attacks. He’s taken down roughly 100 YouTube videos that paint an unflattering picture of him and his cultural views,» the paper concluded. «A candidate who feels the need to hide his past from voters is not someone who can be trusted to be the same person after Election Day as he was on the campaign trail.»

In addition to Harris’ visit, El-Sayed is expected to have a busy final stretch of his campaign before the November election as he attends multiple fundraisers in California and New York. 

In late September, El-Sayed is scheduled to attend a Hollywood fundraiser at the home of George Soros’ nephew, Jeffrey Soros, who is a movie producer. In addition to Soros and his wife, the host committee includes several Obama alums, including Crooked Media’s «Pod Save America» hosts Tommy Vietor and Jon Favreau. Ben Rhodes, the failed architect of Obama’s Iran deal, is also on the host committee.

El-Sayed will also be visiting San Francisco during this West Coast swing.

12 RACES SCRAMBLE SENATE BATTLEFIELD AS DEMOCRATS EYE COMEBACK

Next month, El-Sayed will also be going to New York City to attend a fundraiser hosted by several far-left activists, where the price to attend ranges from $250 to $57,800.

Harris’ endorsement of El-Sayed marks just her second major progressive candidate endorsement in the 2026 midterms. She is also supporting Troy Jackson, the Democratic nominee in Maine who is backed by the Democratic Socialists of America (DSA).

Before the midterms, Harris also supported New York City Mayor Zohran Mamdani, who was also DSA-endorsed, but only stated that she «supported the Democrat in the race.»

For his own part, El-Sayed has rejected terms like «progressive» and «moderate» and is not backed by the DSA.

But like Mamdani, El-Sayed has made affordability — and the role of government — key pieces of his campaign. In addition to calling for lowering housing costs, he’s advocated for Medicare for All, opposes corporate tax carve-outs, and he supports tuition-free access to higher education.

Harris has also received support from El-Sayed in the past.

Notably, after now-former President Joe Biden dropped out of the 2024 election, El-Sayed called on the party to rally behind Harris, citing her «potential» for leadership.

«Considering all the dangers of the Republican nominee … it’s time for all of us to unite behind Kamala Harris to defeat Trump,» El-Sayed wrote in a post in July 2024.

DEMOCRATS WHO ‘NEVER VOTED REPUBLICAN’ BACK ROGERS OVER EL-SAYED IN RAZOR-CLOSE RACE

El-Sayed’s campaign did not respond to requests for comment from Digital on whether El-Sayed might support Harris if she decided to run for the White House in 2028.

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