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Crisis On Two Earths es la mejor película de superhéroes del multiverso

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El multiverso no es ciencia ficción completa. Por supuesto, su existencia no está demostrada, pero tiene una base teórica en la física cuántica real. Se dice que la función de onda (la expresión matemática de un sistema cuántico, que puede proporcionar la probabilidad de dónde encontrar la partícula) “colapsa” después de realizar una medición final. La “interpretación de muchos mundos”, iniciada por el físico Hugh Everett, propone en cambio que cuando se mide un sistema cuántico, todos Posibles mediciones se desarrollan en muchos universos.

comparar El experimento mental del gato de SchrödingerElla misma deriva de la idea de cuantificación; Si pones un gato en una caja cerrada con llave, no hay forma de estar seguro de si el animal está vivo o muerto, por lo que técnicamente es ambas cosas y ninguna de las dos.

Los expertos han notado Cómo ver el mundo de esta manera crea algunas implicaciones filosóficas horribles; Como individuos y como colectivo de toda la humanidad, apreciamos nuestra singularidad. Si cada permutación de “nosotros” existiera en un plano de existencia, esta unicidad sería eliminada. Éste es el origen del nihilismo de Ullmann, aunque define la realidad como una bifurcación que depende de las elecciones de las personas, no del comportamiento de las partículas (este es el origen del nihilismo de Ullmann). Él es Novela basada en personajes).

“Cada decisión que tomamos no tiene sentido porque en algún lugar, en una Tierra paralela, ya hemos tomado la decisión contraria”, explica Ullman. “No somos nada. Menos que nada”. Su análisis no es erróneo en sí mismo. Es fríamente racional bajo cierta lente. Pero habría que ser bastante inmoral para concluir que esto hace que la vida humana “carezca de sentido” – y eso es lo que es Owlman, por lo que quiere destruir la “Tierra-Prime” original, creyendo que esto conducirá al colapso de todos los demás. realidades. “La única acción que uno puede tomar y que tiene algún propósito”, la llama, porque la destrucción de toda la realidad es la única decisión que no podría haber ocurrido de manera contraria en otro mundo.

Woods ofrece una actuación escalofriante como Owlman; Tranquilo y siniestro, lo opuesto a su papel de voz más famoso como el hablador Hades en Hércules. Por otro lado, “Crisis en dos Tierras” se habría beneficiado de elegir a Kevin Conroy como Batman nuevamente, en lugar de reemplazar a Billy Baldwin, ya que esto le habría dado un impulso adicional a la ya gran batalla de Batman y Owlman.

Puedo escuchar a Conroy decirle las líneas de Batman a Ullman con tanta claridad en mi mente, especialmente su despedida: “Hay una diferencia entre tú y yo. Ambos miramos hacia el abismo, pero cuando él nos miró… parpadeé”. Ambos hombres se enfrentaron a la desesperación, pero sólo uno sucumbió a ella.

El personaje de Ullman. Él es Batman es un villano, sí, pero es más profundo que la simple novedad de tener al Caballero Oscuro como villano; Representa un contraste con el espíritu de voluntad y determinación de Batman de que una persona puede marcar la diferencia. Owlman preferiría destruirlo todo antes que vivir con la “ilusión del libre albedrío”, mientras que Batman ve el mundo tal como es, oscuro y claro, y se esfuerza por mejorarlo creyendo que otros, incluso sus enemigos, pueden hacerlo. Él es mejor. Si hay algo que nos enseña “La Liga de la Justicia: Crisis en dos Tierras” es que todos somos la suma de nuestras distintas elecciones.

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Climate change is slowing Earth’s rotation

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Three Gentoo penguins stand together on top of a small melting iceberg off the coast of King George Island, Antarctica.

As polar ice has melted and moved mass towards the Equator, it has slowed Earth’s rotation.Credit: Alessandro Dahan/Getty

Melting ice caps are slowing the rotation of the Earth and could delay the next leap second by three years. Adding or removing seconds every few years keeps official atomic-clock time in line with the natural day, which varies slightly in line with the planet’s rotation rate. Since the early 1990s, the flow of water away from Earth’s axis of rotation and towards the Equator has worked to slightly slow down its spin. “It’s yet another way of impressing upon people just how big a deal [climate change] is,” says geophysicist and study author Duncan Agnew.

Nature | 6 min read

Reference: Nature paper

Earlier this month, editors at the linguistics journal Syntax publicly announced their resignations in response to changes to the manuscript-handling process imposed by its publisher, Wiley. The move is the latest in what seems to be an emerging form of protest: the mass resignation of academic editors. Many such events are in response to changes to business models in the publishing industry. “The big theme [of mass resignations] is this tension of competing priorities,” says Ivan Oransky, co-founder of Retraction Watch.

Nature | 4 min read

Antibodies rejuvenate immune responses in old mice by targeting stem cells that replenish white and red blood cells. The balance of these stem cells changes as mice (and humans) age — this might be one reason why older animals mount less of an immune response against pathogens. Aged mice that received the antibody treatment had a stronger reaction to vaccination, and were better able to fend off viral infection, than untreated rodents.

Nature | 4 min read

Read an expert analysis by developmental biologist Yasar Arfat Kasu and stem-cell biologist Robert Signer in the Nature News & Views article (8 min read, Nature paywall)

Reference: Nature paper

Features & opinion

Injecting particles into the upper atmosphere could deflect some sunlight back into space — but experiments to test this remain controversial. Recently, Harvard University cancelled their solar geoengineering project amid opposition. Advocates say geoengineering might one day provide emergency relief from the worst impacts of climate change. Critics argue that artificially cooling the planet could have unintended consequences and that the idea could reduce pressure on leaders to tackle climate change. “For better or worse, momentum is growing in this space,” says environmental engineer Shuchi Talati.

Nature | 6 min read

The Chipko movement, named after the Hindi word ‘to cling’, began 50 years ago this week when Gaura Devi, an ordinary woman from a village in the Western Himalayas, hugged a tree, using her body as a shield to stop the tree from being cut down. The Chipko movement led to India’s Forest Conservation Act of 1980, and a 15-year moratorium on tree felling. But the villagers’ dreams of bottom-up development never materialized. “Ironically, Chipko, which had set these laws in motion, resulted in local communities losing access to the very forests that met their livelihood and subsistence needs,” writes sustainability researcher Seema Mundoli. Yet Chipko continues to inspire other protest movements led by marginalized communities today.

Nature | 9 min read

Author Rodrigo Culagovski has a murderous time grappling with mind-bending time-travel paradoxes in the latest short story for Nature’s Futures series.

Nature | 6 min read

A moisture-wicking adhesive patch makes wearable electronics more comfortable and stops them from losing signal quality or falling off when the user is sweating. A material that channels perspiration to the edges of the patch ensures that electronic components in the centre stay dry. In a week-long test, a sweat-wicking electrocardiogram (ECG) patch provided stable heart-rate readings, stuck to the skin better and was cooler to wear than other ECG patches.

Nature | 2 min video

Reference: Nature paper

Quote of the day

Programme manager Monica Tomaszewski pranked her Canadian PhD advisor for years by convincing him that his cactus collection smelled like maple syrup in springtime. (Nature | 9 min read)

This week, Leif Penguinson is visiting the mangroves in the Princess Alexandra National Park on the Turks and Caicos Islands. Can you find the penguin?

As always, thanks to Briefing photo editor and penguin wrangler Tom Houghton for his efforts convincing Leif to cling, lounge and hang in such surprising locations each week.

Flora Graham, senior editor, Nature Briefing

With contributions by Gemma Conroy, Katrina Krämer and Sarah Tomlin

Want more? Sign up to our other free Nature Briefing newsletters:

• Nature Briefing: Anthropocene — climate change, biodiversity, sustainability and geoengineering

• Nature Briefing: AI & Robotics — 100% written by humans, of course

• Nature Briefing: Cancer — a weekly newsletter written with cancer researchers in mind

• Nature Briefing: Translational Research covers biotechnology, drug discovery and pharma

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Climate change has slowed Earth’s rotation — and could affect how we keep time

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Climate change is starting to alter how humans keep time.

An analysis1 published in Nature on 27 March has predicted that melting ice caps are slowing Earth’s rotation to such an extent that the next leap second — the mechanism used since 1972 to reconcile official time from atomic clocks with that based on Earth’s unstable speed of rotation — will be delayed by three years.

“Enough ice has melted to move sea level enough that we can actually see the rate of theEarth’s rotation has been affected,” says Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography in La Jolla, California, and author of the study.

According to his analysis, global warming will push back the need for another leap second from 2026 to 2029. Leap seconds cause so much havoc for computing that scientists have voted to get rid of them, but not until 2035. Researchers are especially dreading the next leap second, because, for the first time, it is likely to be a negative, skipped second, rather than an extra one added in.

“We do not know how to cope with one second missing. This is why time metrologists are worried,” says Felicitas Arias, former director of the Time Department at the International Bureau of Weights and Measures in Sèvres, France.

In metrology terms, the three-year delay “is good news”, she says, because even if a negative leap second is still needed, it will happen later, and the world might see fewer of them before 2035 than would otherwise have been anticipated.

But this should not be seen as a point in favour of global warming, Agnew says. “It’s completely outweighed by all the negative aspects.”

Synchronizing clocks

For millennia, people measured time using Earth’s rotation, and the second became defined as a fraction of the time it takes for the planet to turn once on its axis. But since 1967, atomic clocks — which tick using the frequency of light emitted by atoms — have served as more precise timekeepers. Today, a suite of around 450 atomic clocks defines official time on Earth, known as Coordinated Universal Time (utc), and leap seconds are used every few years to keep utc in line with the planet’s natural day.

Atomic clocks are better timekeepers than Earth, because they are stable over millions of years, whereas the planet’s rotation rate varies. In his analysis, Agnew used mathematical models to tease apart the contributions of known geophysical phenomena to Earth’s rotation and to predict their effects on future leap seconds.

Many metrologists anticipated that leap seconds would only ever be added, because on the scale of millions of years, Earth’s spin is slowing down, meaning that, occasionally, a minute in utc needs to be 61 seconds long, to allow Earth to catch up. This reduction in the planet’s rotation rate is caused by the Moon’s pull on the oceans, which creates friction. It also explains, for example, why eclipses 2,000 years ago were recorded at different times in the day from what we would expect on the basis of today’s rotation rate, and why analyses of ancient sediments suggest that 1.4 billion years ago a day was only around 19 hours long.

But on shorter timescales, geophysical phenomena make the rotation rate fluctuate, says Agnew. Right now, the rate at which Earth spins is being affected by currents in the liquid core of the planet, which since the 1970s have caused the rotation speed of the outer crust to increase. This has meant that added leap seconds are needed less frequently, and if the trend continues, a leap second will need to be removed from utc.

Agnew’s analysis finds that this could happen later than was previously thought, because of climate change. Data from satellites mapping Earth’s gravity show that since the early 1990s the planet has become less spherical and more flattened, as ice from Greenland and Antarctica has melted and moved mass away from the poles towards the Equator. Just as a spinning ice skater slows down by extending their arms away from their body (and speeds up by pulling them in), this flow of water away from Earth’s axis of rotation slows the planet’s spin.

The net result of core currents and of climate change is still an accelerating Earth. But Agnew found that without the effect of melting ice, a negative leap second would be needed three years earlier than is now predicted. “Human activities have a profound impact on climate change. The postponing of a leap second is just one more example,” says Jianli Chen, a geophysicist at the Hong Kong Polytechnic University.

Precision problems

A delayed leap second would be welcomed by metrologists. Leap seconds are a “big problem” already, because in a society that is increasingly based on precise timing, they lead to major failures in computing systems, says Elizabeth Donley, who heads the time and frequency division at the National Institute of Standards and Technology in Boulder, Colorado.

An unprecedented negative leap second could be even worse. “There’s no accounting for it in all the existing computer codes,” she says.

Agnew’s paper is useful in making predictions, but Donley says that there is still high uncertainty about when a negative leap second will be needed. The calculations rely on Earth’s acceleration continuing at its present rate, but activity in the inner core is almost impossible to predict, cautions Christian Bizouard, an astrogeophysicist at the International Earth Rotation and Reference Systems Service in Paris, which is responsible for deciding when to introduce a leap second. “We do not know when that mean acceleration will stop and reverse itself,” he says.

Agnew hopes that seeing the influence of climate change on timekeeping will jolt some people into action. “I’ve been around climate change for a long time, and I can worry about it plenty well without this, but it’s yet another way of impressing upon people just how big a deal this is,” he says.

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Geologists reject the Anthropocene as Earth’s new epoch — after 15 years of debate

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After 15 years of discussion and exploration, a committee of researchers has decided that the Anthropocene — generally understood to be the age of irreversible human impacts on the planet — will not become an official epoch in Earth’s geological timeline. The ruling, first reported by The New York Times, is meant to be final, but is being challenged by two leading members of the committee that ran the vote.

Twelve members of the international Subcommission on Quaternary Stratigraphy (SQS) voted against the proposal to create an Anthropocene epoch, and only four voted for it. That would normally constitute an unqualified defeat, but a dramatic challenge has arisen from the chair of the SQS, palaeontologist Jan Zalasiewicz at the University of Leicester, UK, and one of the group’s vice-chairs, stratigrapher Martin Head at Brock University in St Catharines, Canada.

In a 6 March press statement, they said that they are asking for the vote to be annulled. They added that “the alleged voting has been performed in contravention of the statutes of the International Commission on Stratigraphy” (ICS), including statutes governing the eligibility to vote. Zalasiewicz told Nature that he couldn’t comment further just yet, but that neither he nor Head had “instigated the vote or agreed to it, so we are not responsible for procedural irregularities”.

The SQS is a subcommittee of the ICS. Normally, there would be no appeals process for a losing vote. ICS chair David Harper, a palaeontologist at Durham University, UK, had confirmed to Nature before the 6 March press statement that the proposal “cannot be progressed further”. Proponents could put forward a similar idea in the future.

If successful, the proposal would have codified the end of the current Holocene epoch, which has been going on since the end of the last ice age 11,700 years ago, and set the start of the Anthropocene in the year 1952. This is when plutonium from hydrogen-bomb tests showed up in the sediment of Crawford Lake near Toronto, Canada, a site chosen by some geologists to be designated as a ‘golden spike’ as capturing a pristine record of humans’ impact on Earth. Other signs of human influence in the geological record include microplastics, pesticides and ash from fossil-fuel combustion.

But pending the resolution of the challenge, the lake and its plutonium residue won’t get a golden spike. Selecting one site as such a marker “always felt a bit doomed, because human impacts on the planet are global”, says Zoe Todd, an anthropologist at Simon Fraser University in Burnaby, Canada. “This is actually an invitation for us to completely rethink how we define what the world is experiencing.”

A cultural concept

Although the Anthropocene probably will not be added to the geological timescale, it remains a broad cultural concept already used by many to describe the era of accelerating human impacts, such as climate change and biodiversity loss. “We are now on a fundamentally unpredictable planet in ways that we have not experienced for the last 12,000 years,” says Julia Adeney Thomas, a historian at the University of Notre Dame, in Indiana. “That understanding of the Anthropocene is crystal clear.”

The decision to reject the designation was made public through The New York Times on 5 March, after the SQS had concluded its month-long voting process, but before committee leaders had finalized discussions and made an official announcement. Philip Gibbard, a geologist at the University of Cambridge, UK, who is on the SQS, says that the crux of the annulment challenge is that Zalasiewicz and Head objected to the voting process kicking off on 1 February. The rest of the committee wanted to move forward with a vote and did so according to SQS rules, Gibbard says. “There’s a lot of sour grapes going on here,” he adds.

Had the proposal made it through the SQS, it would have needed to clear two more hurdles: first, a ratification vote by the full stratigraphic commission, and then a final one in August at a forum of the International Union of Geological Sciences.

Frustrated by defeat

Some of those who helped to draw up the proposal, through an Anthropocene working group commissioned by the SQS, are frustrated by the apparent defeat. They had spent years studying a number of sites around the world that could represent the start of a human-influenced epoch. They performed fresh environmental analyses on many of the sites, including studying nuclear debris, fossil-fuel ash and other markers of humans’ impact in geological layers, before settling on Crawford Lake.

“We have made it very clear that the planet we’re living on is different than it used to be, and that the big tipping point was in the mid-twentieth century,” says Francine McCarthy, a micropalaeontologist at Brock University who led the Crawford Lake proposal1. Even though the SQS has rejected it, she says she will keep working to highlight the lake’s exceptionally preserved record of human activities. “Crawford Lake is just as great a place as it ever was.”

“To be honest, I am very disappointed with the SQS outcome,” says working-group member Yongming Han, a geochemist at the Institute of Earth Environment of the Chinese Academy of Sciences in Xi’an. “We all know that the planet has entered a period in which humans act as a key force and have left indisputable stratigraphic evidences.”

For now, the SQS and the ICS will sort out how to handle Zalasiewicz and Head’s request for a vote annulment. Meanwhile, scientific and public discussions about how best to describe the Anthropocene continue.

One emerging argument is that the Anthropocene should be defined as an event in geological history — similar to the rise of atmospheric oxygen just over two billion years ago, known as the Great Oxidation Event — but not as a formal epoch2. This would make more sense because geological events unfold as transformations over time, such as humans industrializing and polluting the planet, rather than as an abrupt shift from one state to another, says Erle Ellis, an ecologist at the University of Maryland Baltimore County in Baltimore. “We need to think about this as a broader process, not as a distinct break in time,” says Ellis, who resigned from the Anthropocene working group last year because he felt it was looking at the question too narrowly.

This line of thinking played a part in at least some of the votes to reject the idea of an Anthropocene epoch. Two SQS members told Nature they had voted down the proposal in part because of the long and evolving history of human impacts on Earth.

“By voting ‘no’, they [the SQS] actually have made a stronger statement,” Ellis says: “that it’s more useful to consider a broader view — a deeper view of the Anthropocene.”

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Earth’s earliest forest revealed in Somerset fossils

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The oldest fossilised forest known on Earth — dating from 390 million years ago — has been found in the high sandstone cliffs along the Devon and Somerset coast of South West England.

The fossils, discovered and identified by researchers from the Universities of Cambridge and Cardiff, are the oldest fossilised trees ever found in Britain, and the oldest known fossil forest on Earth. This fossil forest is roughly four million years older than the previous record holder, which was found in New York State.

The fossils were found near Minehead, on the south bank of the Bristol Channel, near what is now a Butlin’s holiday camp. The fossilised trees, known as Calamophyton, at first glance resemble palm trees, but they were a ‘prototype’ of the kinds of trees we are familiar with today. Rather than solid wood, their trunks were thin and hollow in the centre. They also lacked leaves, and their branches were covered in hundreds of twig-like structures.

These trees were also much shorter than their descendants: the largest were between two and four metres tall. As the trees grew, they shed their branches, dropping lots of vegetation litter, which supported invertebrates on the forest floor.

Scientists had previously assumed this stretch of the English coast did not contain significant plant fossils, but this particular fossil find, in addition to its age, also shows how early trees helped shape landscapes and stabilise riverbanks and coastlines hundreds of millions of years ago. The results are reported in the Journal of the Geological Society.

The forest dates to the Devonian Period, between 419 million and 358 million years ago, when life started its first big expansion onto land: by the end of the period, the first seed-bearing plants appeared and the earliest land animals, mostly arthropods, were well-established.

“The Devonian period fundamentally changed life on Earth,” said Professor Neil Davies from Cambridge’s Department of Earth Sciences, the study’s first author. “It also changed how water and land interacted with each other, since trees and other plants helped stabilise sediment through their root systems, but little is known about the very earliest forests.”

The fossil forest identified by the researchers was found in the Hangman Sandstone Formation, along the north Devon and west Somerset coasts. During the Devonian period, this region was not attached to the rest of England, but instead lay further south, connected to parts of Germany and Belgium, where similar Devonian fossils have been found.

“When I first saw pictures of the tree trunks I immediately knew what they were, based on 30 years of studying this type of tree worldwide” said co-author Dr Christopher Berry from Cardiff’s School of Earth and Environmental Sciences. “It was amazing to see them so near to home. But the most revealing insight comes from seeing, for the first time, these trees in the positions where they grew. It is our first opportunity to look directly at the ecology of this earliest type of forest, to interpret the environment in which Calamophyton trees were growing, and to evaluate their impact on the sedimentary system.”

The fieldwork was undertaken along the highest sea-cliffs in England, some of which are only accessible by boat, and revealed that this sandstone formation is in fact rich with plant fossil material from the Devonian period. The researchers identified fossilised plants and plant debris, fossilised tree logs, traces of roots and sedimentary structures, preserved within the sandstone. During the Devonian, the site was a semi-arid plain, criss-crossed by small river channels spilling out from mountains to the northwest.

“This was a pretty weird forest — not like any forest you would see today,” said Davies. “There wasn’t any undergrowth to speak of and grass hadn’t yet appeared, but there were lots of twigs dropped by these densely-packed trees, which had a big effect on the landscape.”

This period marked the first time that tightly-packed plants were able to grow on land, and the sheer abundance of debris shed by the Calamophyton trees built up within layers of sediment. The sediment affected the way that the rivers flowed across the landscape, the first time that the course of rivers could be affected in this way.

“The evidence contained in these fossils preserves a key stage in Earth’s development, when rivers started to operate in a fundamentally different way than they had before, becoming the great erosive force they are today,” said Davies. “People sometimes think that British rocks have been looked at enough, but this shows that revisiting them can yield important new discoveries.”

The research was supported in part by the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI). Neil Davies is a Fellow of Churchill College, Cambridge.

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