Tag: space

The True Origins of Gold in Our Universe May Have Just Changed, Again

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By MICHELLE STARR

When humanity finally detected the collision between two neutron stars in 2017, we confirmed a long-held theory – in the energetic fires of these incredible explosions, elements heavier than iron are forged.

And so, we thought we had an answer to the question of how these elements – including gold – propagated throughout the Universe.

But a new analysis has revealed a problem. According to new galactic chemical evolution models, neutron star collisions don’t even come close to producing the abundances of heavy elements found in the Milky Way galaxy today.

“Neutron star mergers did not produce enough heavy elements in the early life of the Universe, and they still don’t now, 14 billion years later,” said astrophysicist Amanda Karakas of Monash University and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) in Australia.

“The Universe didn’t make them fast enough to account for their presence in very ancient stars, and, overall, there are simply not enough collisions going on to account for the abundance of these elements around today.”

Stars are the forges that produce most of the elements in the Universe. In the early Universe, after the primordial quark soup cooled enough to coalesce into matter, it formed hydrogen and helium – still the two most abundant elements in the Universe.

The first stars formed as gravity pulled together clumps of these materials. In the nuclear fusion furnaces of their cores, these stars forged hydrogen into helium; then helium into carbon; and so on, fusing heavier and heavier elements as they run out of lighter ones until iron is produced.

Iron itself can fuse, but it consumes huge amounts of energy – more than such fusion produces – so an iron core is the end point.

“We can think of stars as giant pressure cookers where new elements are created,” Karakas said. “The reactions that make these elements also provide the energy that keeps stars shining bright for billions of years. As stars age, they produce heavier and heavier elements as their insides heat up.”

To create elements heavier than iron – such as gold, silver, thorium and uranium – the rapid neutron-capture process, or r-process, is required. This can take place in really energetic explosions, which generate a series of nuclear reactions in which atomic nuclei collide with neutrons to synthesise elements heavier than iron.

But it needs to happen really quickly, so that radioactive decay doesn’t have time to occur before more neutrons are added to the nucleus.

We know now that the kilonova explosion generated by a neutron star collision is an energetic-enough environment for the r-process to take place. That’s not under dispute. But, in order to produce the quantities of these heavier elements we observe, we’d need a minimum frequency of neutron star collisions.

To figure out the sources of these elements, the researchers constructed galactic chemical evolution models for all stable elements from carbon to uranium, using the most up-to-date astrophysical observations and chemical abundances in the Milky Way available. They included theoretical nucleosynthesis yields and event rates.

They laid out their work in a periodic table that shows the origins of the elements they modelled. And, among their findings, they found the neutron star collision frequency lacking, from the early Universe to now. Instead, they believe that a type of supernova could be responsible.

These are called magnetorotational supernovae, and they occur when the core of a massive, fast-spinning star with a strong magnetic field collapses. These are also thought to be energetic enough for the r-process to take place. If a small percentage of supernovae of stars between 25 and 50 solar masses are magnetorotational, that could make up the difference.

“Even the most optimistic estimates of neutron star collision frequency simply can’t account for the sheer abundance of these elements in the Universe,” said Karakas. “This was a surprise. It looks like spinning supernovae with strong magnetic fields are the real source of most of these elements.”

Previous research has found a type of supernova called a collapsar supernova can also produce heavy elements. This is when a rapidly rotating star over 30 solar masses goes supernova before collapsing down into a black hole. These are thought to be much rarer than neutron star collisions, but they could be a contributor – it matches neatly with the team’s other findings.

They found that stars less massive than about eight solar masses produce carbon, nitrogen, fluorine, and about half of all the elements heavier than iron. Stars more massive than eight solar masses produce most of the oxygen and calcium needed for life, as well as most of the rest of the elements between carbon and iron.

“Apart from hydrogen, there is no single element that can be formed only by one type of star,” explained astrophysicist Chiaki Kobayashi of the University of Hertfordshire in the UK.

“Half of carbon is produced from dying low-mass stars, but the other half comes from supernovae. And half the iron comes from normal supernovae of massive stars, but the other half needs another form, known as Type Ia supernovae. These are produced in binary systems of low mass stars.”

This doesn’t necessarily mean that the estimated 0.3 percent of Earth’s gold and platinum traced back to a neutron star collision 4.6 billion years ago has a different origin story. It’s just not necessarily the whole story.

But we’ve only been detecting gravitational waves for five years. It could be, as our equipment and techniques improve, that we find neutron star collisions are much more frequent than we think they are at this current time.

Curiously, the researchers’ models also turned out more silver than observed, and less gold. That suggests something needs to be tweaked. Perhaps it’s the calculations. Or perhaps there are some aspects of stellar nucleosynthesis that we are yet to understand.

The research has been published in The Astrophysical Journal.

https://www.sciencealert.com/neutron-star-collisions-may-not-be-making-much-gold-after-all

Astronomers Spot Possible Signs Of Extraterrestrial Life In Venus’s Clouds

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There may be bizarre microbes living in the sulfuric acid-laden clouds of the hothouse planet, scientists said.

By Seth Borenstein

Astronomers have found a potential sign of life high in the atmosphere of neighboring Venus: hints there may be bizarre microbes living in the sulfuric acid-laden clouds of the hothouse planet.

Two telescopes in Hawaii and Chile spotted in the thick Venutian clouds the chemical signature of phosphine, a noxious gas that on Earth is only associated with life, according to a study in Monday’s journal Nature Astronomy.

Several outside experts — and the study authors themselves — agreed this is tantalizing but said it is far from the first proof of life on another planet. They said it doesn’t satisfy the “extraordinary claims require extraordinary evidence” standard established by the late Carl Sagan, who speculated about the possibility of life in the clouds of Venus in 1967.

“It’s not a smoking gun,” said study co-author David Clements, an Imperial College of London astrophysicist. “It’s not even gunshot residue on the hands of your prime suspect, but there is a distinct whiff of cordite in the air which may be suggesting something.”

As astronomers plan for searches for life on planets outside our solar system, a major method is to look for chemical signatures that can only be made by biological processes, called biosignatures. After three astronomers met in a bar in Hawaii, they decided to look that way at the closest planet to Earth: Venus. They searched for phosphine, which is three hydrogen atoms and a phosphorous atom.

On Earth, there are only two ways phosphine can be formed, study authors said. One is in an industrial process. (The gas was produced for use as chemical warfare agent in World War I.) The other way is as part of some kind of poorly understood function in animals and microbes. Some scientists consider it a waste product, others don’t.

Phosphine is found in “ooze at the bottom of ponds, the guts of some creatures like badgers and perhaps most unpleasantly associated with piles of penguin guano,” Clements said.

Study co-author Sara Seager, an MIT planetary scientist, said researchers “exhaustively went through every possibility and ruled all of them out: volcanoes, lightning strikes, small meteorites falling into the atmosphere. … Not a single process we looked at could produce phosphine in high enough quantities to explain our team’s findings.”

That leaves life.

The astronomers hypothesize a scenario for how life could exist on the inhospitable planet where temperatures on the surface are around 800 degrees (425 degrees Celsius) with no water.

“Venus is hell. Venus is kind of Earth’s evil twin,” Clements said. “Clearly something has gone wrong, very wrong, with Venus. It’s the victim of a runaway greenhouse effect.”

But that’s on the surface.

Seager said all the action may be 30 miles above ground in the thick carbon-dioxide layer cloud deck, where it’s about room temperature or slightly warmer. It contains droplets with tiny amounts of water but mostly sulfuric acid that is a billion times more acidic than what’s found on Earth.

The phosphine could be coming from some kind of microbes, probably single-cell ones, inside those sulfuric acid droplets, living their entire lives in the 10-mile-deep clouds, Seager and Clements said. When the droplets fall, the potential life probably dries out and could then get picked up in another drop and reanimate, they said.

Life is definitely a possibility, but more proof is needed, several outside scientists said.

Cornell University astronomer Lisa Kaltenegger said the idea of this being the signature of biology at work is exciting, but she said we don’t know enough about Venus to say life is the only explanation for the phosphine.

“I’m not skeptical, I’m hesitant,” said Justin Filiberto, a planetary geochemist at the Lunar and Planetary Institute in Houston who specializes in Venus and Mars and isn’t part of the study team.

Filiberto said the levels of phosphine found might be explained away by volcanoes. He said recent studies that were not taken into account in this latest research suggest that Venus may have far more active volcanoes than originally thought. But Clements said that explanation would make sense only if Venus were at least 200 times as volcanically active as Earth.

David Grinspoon, a Washington-based astrobiologist at the Planetary Science Institute who wrote a 1997 book suggesting Venus could harbor life, said the finding “almost seems too good to be true.”

“I’m excited, but I’m also cautious,” Grinspoon said. “We found an encouraging sign that demands we follow up.”

NASA hasn’t sent anything to Venus since 1989, though Russia, Europe and Japan have dispatched probes. The U.S. space agency is considering two possible Venus missions. One of them, called DAVINCI+, would go into the Venutian atmosphere as early as 2026.

Clements said his head tells him “it’s probably a 10% chance that it’s life,” but his heart “obviously wants it to be much bigger because it would be so exciting.”

https://www.huffpost.com/entry/venus-possible-life_n_5f5f878ac5b68d1b09c5ab9b

There’s a Theory Beyond Relativity That Would Allow You to Fly Through a Wormhole

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By Matt Williams

Wormholes are a popular feature in science fiction, the means through which spacecraft can achieve faster-than-light (FTL) travel and instantaneously move from one point in spacetime to another.

And while the General Theory of Relativity forbids the existence of “traversable wormholes”, recent research has shown that they are actually possible within the domain of quantum physics.

The only downsides are that they would actually take longer to traverse than normal space and/or likely be microscopic.

In a new study performed by a pair of Ivy League scientists, the existence of physics beyond the Standard Model could mean that there are wormholes out there that are not only large enough to be traversable, but entirely safe for human travelers looking to get from point A to point B.

The study, titled “Humanly traversable wormholes,” was conducted by Juan Maldacena (the Carl P. Feinberg Professor of theoretical physics from the Institute of Advanced Study) and Alexey Milekhin, a graduate of astrophysics student at Princeton University. The pair have written extensively on the subject of wormholes in the past and how they could be a means for traveling safely through space.

The theory regarding wormholes emerged in the early 20th century in response to Einstein’s General Theory of Relativity. The first to postulate their existence was Karl Schwarzschild, a German physicist and astronomer whose solutions to Einstein’s field equation (the Schwarzschild metric) resulted in the first theoretical basis for the existence of black holes.

A consequence of the Schwarzschild metric was what he referred to as “eternal black holes,” which were essentially connections between different points in spacetime. However, these Schwarzschild wormholes (aka. Einstein–Rosen bridges) were not stable as they would collapse too quickly for anything to cross from one end to the other.

As Maldacena and Milekhin explained to Universe Today via email, traversable wormholes require special circumstances in order to exist. This includes the existence of negative energy, which is not permissible in classic physics – but is possible within the realm of quantum physics.

A good example of this, they claim, is the Casimir Effect, where quantum fields produce negative energy while propagating along a closed circle:

“However, this effect is typically small because it is quantum. In our previous paper [“Traversable wormholes in four dimensions”] we realized that this effect can become considerable for black holes with large magnetic charge. The new idea was to use special properties of charged massless fermions (particles like the electron but with zero mass). For a magnetically charged black hole these travel along the magnetic field lines (In a way similar to how the charged particles of the solar wind create the auroras near the polar regions of the Earth).”

The fact that these particles can travel in a circle by entering one spot and emerging where they started in ambient flat space, implies that the “vacuum energy” is modified and can be negative.

The presence of this negative energy can support the existence of a stable wormhole, a bridge between points in spacetime that won’t collapse before something has a chance to traverse it.

Such wormholes are possible based on matter that is part of the Standard Model of particle physics. The only problem is, these wormholes would have to be microscopic in size and would only exist over very small distances.

For human travel, the wormholes would have to be large, which requires that physics beyond the Standard Model be employed.

For Maldacena and Milekhin, this is where the Randall-Sundrum II model (aka. 5-dimensional warped geometry theory) comes into play. Named after theoretical physicists Lisa Randall and Raman Sundrum, this model describes the Universe in terms of five-dimensions and was originally proposed to solve a hierarchy problem in particle physics.

“The Randall-Sundrom II model was based on the realization that this five-dimensional spacetime could also be describing physics at lower energies than the ones we usually explore, but that it would have escaped detection because it couples with our matter only through gravity. In fact, its physics is similar to adding many strongly interacting massless fields to the known physics. And for this reason it can give rise to the required negative energy.”

From the outside, Maldacena and Milekhin concluded that these wormholes would resemble intermediately-sized, charged black holes that would generate similarly-powerful tidal forces that spacecraft would need to be wary of. To do that, they claim, a potential traveler would need a very large boost factor as they pass through the center of the wormhole.

Assuming that can be done, the question remains of whether or not these wormholes could act as a shortcut between two points in spacetime? As noted, previous research by Daniel Jafferis of Harvard University (which also considered the work of Einstein and Nathan Rosen) showed that while possible, stable wormholes would actually take longer to traverse than normal space.

According to Maldacena and Milekhin’s work, however, their wormholes would take almost no time to traverse from the perspective of the traveler. From the perspective of an outsider, the travel time would be much longer, which is consistent with General Relativity – where people traveling close to the speed of light will experience time dilation (i.e. time slows down). As Maldacena and Milekhin put it:

“]F]or astronauts going through the wormhole it would take only 1 second of their time to travel 10,000 light-year distance (approximately 5000 billion miles or 1/10 of Milky Way size). An observer who does not go through the wormhole and stays outside sees them taking more than 10,000 years. And all this with no use of fuel, since the gravity accelerates and decelerates the spaceship.”

Another bonus is that traversing these wormholes could be done without the use of fuel since the gravitational force of the wormhole itself would accelerate and decelerates the spaceship. In a space exploration scenario, a pilot would need to navigate the tidal forces of the wormhole to position their spacecraft just right, and then let nature do the rest.

A second later, they would emerge on the other side of the galaxy!

While this might sound encouraging to those who think wormholes could be a means of space travel someday, Maldacena and Milekhin’s work presents some significant drawbacks as well.

For starters, they emphasize that traversable wormholes would have to be engineered using negative mass since no plausible mechanism exists for natural formation.

While this is possible (at least in theory), the necessary spacetime configurations would need to be present beforehand. Even so, the mass and size involved are so great that the task would be beyond any practical technology we can foresee. Second, these wormholes would only be safe if space were cold and flat, which is not the case beyond the Randall Sundrum II model.

On top of all that, any object that enters the wormhole would be accelerated and even the presence of pervasive cosmic background radiation would be a significant hazard.

However, Maldacena and Milekhin emphasize that their study was conducted for the purpose of showing that traversable wormholes can exist as a result of the “subtle interplay between general relativity and quantum physics.”

In short, wormholes are not likely to become a practical way to travel through space – at least, not in any way that’s foreseeable. Perhaps they would not be beyond a Kardashev Type II or Type III civilization, but that’s just speculation. Even so, knowing that a major element in science fiction is not beyond the realm of possibility is certainly encouraging!

https://www.sciencealert.com/there-s-a-theory-of-relativity-that-could-allow-you-to-fly-through-a-wormhole

A Strange Form of Life Could Flourish Deep Inside of Stars, Physicists Say

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by Michelle Starr

When searching for signs of life in the Universe, we tend to look for very specific things, based on what we know: a planet like Earth, in orbit around a star, and at a distance that allows liquid surface water. But there could, conceivably, be other forms of life out there that look like nothing that we have ever imagined before.

Just as we have extremophiles here on Earth – organisms that live in the most extreme and seemingly inhospitable environments the planet has to offer – so too could there be extremophiles out there in the wider Universe.

For instance, species that can form, evolve, and thrive in the interiors of stars. According to new research by physicists Luis Anchordoqui and Eugene Chudnovsky of The City University of New York, such a thing is indeed – hypothetically, at least – possible.

It all depends on how you define life. If the key criteria are the ability to encode information, and the ability for those information carriers to self-replicate faster than they disintegrate, then hypothetical monopole particles threaded on cosmic strings – cosmic necklaces – could form the basis of life inside stars, much like DNA and RNA form the basis of life on Earth.

“Information stored in the RNA (or DNA) encodes the mechanism of self-replication,” Chudnovsky told ScienceAlert.

“Its emergence must have been preceded by the massive formation of random RNA sequences until a sequence was formed capable of self-replication. We believe that a similar process would occur with necklaces in a star, leading to a stationary process of self-replication.”

Strings and monopoles are thought to have emerged in the early Universe, as it cooled down from the Big Bang, and the particle soup of quark-gluon plasma that filled it underwent a symmetry-breaking phase transition and condensed into matter – like vapour condensing into liquid.

Although we have yet to detect cosmic strings (one-dimensional linear objects) or monopoles (elementary particles with only one magnetic pole), a lot of thought has gone into how they might behave.

In 1988, Chudnovsky and his colleague, theoretical physicist Alexander Vilenkin of Tufts University, predicted that cosmic strings could be captured by stars. There, the turbulence would stretch the string until it formed a network of strings.

According to the new study, cosmic necklaces could form in a sequence of symmetry-breaking phase transitions. In the first stage, monopoles emerge. In the second, strings.

This can produce a stable configuration of one monopole bead and two strings, which in turn could connect to form one-, two-, and even three-dimensional structures – much like atoms joined by chemical bonds, the researchers say.

A one-dimensional necklace would be unlikely to carry information. But more complex structures potentially could – and they could survive long enough to replicate, feeding off the fusion energy generated by the star.

“Compared to the lifetime of a star, its lifetime is an instantaneous spark of light in the dark. What is important is that such a spark manages to produce more sparks before it fades away, thus providing a long lifespan of the species,” the researchers write.

“The complexity evolving through mutations and natural selection increases with the number of generations passed. Consequently, if lifetimes of self-replicating nuclear species are as short as lifetimes of many unstable composite nuclear objects are, they can quickly evolve toward enormous complexity.”

Hypothetically speaking, it’s perhaps possible that such a life-form could develop intelligence, and maybe even serious smarts, Chudnovsky says.

What such a species would look like is a feast for the imagination. But we don’t have to know what they look like to search for signs of their presence. Because such organisms would use some of the energy of their host star to survive and propagate, stars that seem to cool faster than stellar models can account for could be hosts for what the researchers call “nuclear life”.

Several such stars have been observed, and their slightly accelerated cooling is still a mystery. Stars that dim erratically without explanation could be a good place to look, too – like EPIC 249706694. The researchers are careful to note that to link these stars to nuclear life would be an extremely long bow to draw. But there are interesting anomalies out there. And interesting possibilities too.

“Since they would be evolving very fast, they could find a way to explore the cosmos beyond their star, as we have done,” Chudnovsky told ScienceAlert. “They could establish communication and travel between stars. Maybe we should look for their presence in space.”

It’s all extremely theoretical, but wild ideas can be a good way to make new discoveries. The researchers plan to continue their line of inquiry by developing simulations of cosmic necklaces in stars. It may not lead us to glittering star aliens – but even if it doesn’t, it could give us a better understanding of cosmic strings and monopoles.

“It is a fascinating thought that the Universe may be packed with intelligent life that is so different from ours that we failed to recognise its existence,” Chudnovsky said.

The research has been published in Letters in High Energy Physics.

https://www.sciencealert.com/physicists-argue-that-life-based-on-cosmic-strings-may-be-possible-inside-stars

This Could Be the First Record of Someone Getting Killed by a Meteorite

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A drawing of a meteorite falling in Ukraine in 1866.

By Ryan F. Mandelbaum

A team of scientists think they’ve found the oldest evidence of a meteorite striking and killing a person, according to a new report published in the journal journal Meteoritics & Planetary Science.

Given the hype around space rocks hitting Earth, there are surprisingly few records of meteorites striking people, much less killing anyone. But scientists at the Ego University and Trakya University in Turkey and the SETI Institute in the United States found a 1888 record from General Directorate of State Archives of the Presidency of the Republic of Turkey that contains three manuscripts that seem to recount a death-by-meteorite event.

The first manuscript, written on September 13, 1888, details a fireball occurring the month before in the evening, over a village whose exact location the scientists couldn’t determine. Smoke and fire accompanied the flash, and meteorites rained from the sky for 10 minutes. One man died and another was injured and paralyzed as a result of the event. A second manuscript contained a request forwarded to Sultan Abdul Hamid II asking what should be done about the event. A third also recounts the events and mentions that a man named Ahmed Munir Pasha sent a letter with “a stone piece” to the Grand Vizier.

Basically, on August 22, 1888, a meteor exploded over a village in Turkey, killing one man and paralyzing another. On September 13, a local legislator reported the event; the central government heard about it on October 8; and the sultan heard about it on October 9, according to the translations in the new paper, titled “Earliest evidence of a death and injury by a meteorite.”

Translating these documents came with its challenges—Ottoman Turkish is difficult to read, the scientists explained. The researchers noted that there are still a lot more records awaiting digitization, and they don’t have any physical evidence of the 1888 impact. Regardless, this would be the earliest known record definitively stating that a meteorite killed someone.

Meteorite deaths are exceedingly rare. Most recently, a bus driver in India named V. Kamaraj died in an apparent meteorite strike in Natrampalli back in 2016, though scientific experts, including at NASA, refuted the claim. The National Resource Council estimates that 91 people should die in meteorite-related accidents every year, but there aren’t records of these deaths. Injury-by-meteorite is perhaps more common—over 1,600 people were injured when a meteor fell over Chelyabinsk in Russia in 2013, and famously, Ann Hewlett Hodges was hit and slightly hurt by a meteorite in Alabama in 1954.

Earth is big enough that the odds of dying from a meteorite impact are exceedingly slim.

https://gizmodo.com/this-could-be-the-first-record-of-someone-getting-kille-1843045054

Long space flights can increase the volume of astronauts’ brains

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Astronauts’ brains increase in volume after long space flights, causing pressure to build up inside their heads. This may explain why some astronauts experience worsened vision after prolonged periods in space.

“This raises additional concerns for long-duration interplanetary travel, such as the future mission to Mars,” says Larry Kramer at the University of Texas Health Science Center at Houston, who led the study.

Kramer and his colleagues scanned the brains of 11 astronauts before they spent about six months on the International Space Station, and at six points over the year after they returned to Earth. They found that all the astronauts had increased brain volume – including white matter, grey matter and cerebrospinal fluid around the brain – after returning from space.

Under normal gravity, it is thought that fluid in the brain naturally moves downwards when we stand upright. But there is evidence that microgravity prevents this, resulting in accumulation of fluid in the brain and skull.

The astronauts’ brain volume increased by 2 per cent on average and the increases were still present one year after they returned to Earth, which could result in higher intracranial pressure, Kramer says. He suspects this might press on the optic nerve, potentially explaining the vision problems frequently reported by astronauts.

Kramer and his team also observed that part of the brain called the pituitary gland was deformed in six out of the 11 astronauts. These results add to a body of evidence suggesting that brain structure can be altered after space flight.

“This study is important because it provides data, for the first time in NASA astronauts, demonstrating the persistence of structural brain changes even up to one year following return to Earth,” says Donna Roberts at the Medical University of South Carolina.

“We are currently working on methods to counteract the changes we are observing in the brain using artificial gravity,” says Kramer. These methods to pull blood back towards the feet could include a human-sized centrifuge that would spin a person around at high speed, or a vacuum chamber around the lower half of the body.

“Hopefully one of these or other methods will be tested in microgravity and show efficacy,” he says.

Journal reference: Radiology, DOI: 10.1148/radiol.2020191413

Read more: https://www.newscientist.com/article/2240405-long-space-flights-can-increase-the-volume-of-astronauts-brains/#ixzz6Jh5CtujT

Aliens definitely exist and they could be living among us on Earth, says Britain’s first astronaut

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By Rob Picheta

Aliens definitely exist, Britain’s first astronaut has said — and it’s possible they’re living among us on Earth but have gone undetected so far.

Helen Sharman, who visited the Soviet Mir space station in 1991, told the Observer newspaper on Sunday that “aliens exist, there’s no two ways about it.”

“There are so many billions of stars out there in the universe that there must be all sorts of different forms of life,” she went on. “Will they be like you and me, made up of carbon and nitrogen? Maybe not.”

Then, in a tantalizing theory that should probably make you very suspicious of your colleagues, Sharman added: “It’s possible they’re here right now and we simply can’t see them.”
Sharman was the first of seven Britons to enter space.

The chemist spent eight days as a researcher on the space mission when she was 27, making her one of the youngest people to enter orbit.

NASA rovers are trawling Mars for evidence of past or present life forms, but humankind’s endless fascination with extraterrestrial life forms has so far proved fruitless.

Sharman is not the only person to speculate that we’ve had brushes with aliens, though.

A former Pentagon official who led a secret government program to research potential UFOs, revealed in 2017, told CNN at the time that he believes there is evidence of alien life reaching Earth.

Elsewhere in her interview, Sharman said there is “no greater beauty than looking at the Earth from up high.”

“I’ll never forget the first time I saw it,” she added.

Sharman also discussed her frustration with observers defining her by her sex. “People often describe me as the first British woman in space, but I was actually the first British person. It’s telling that we would otherwise assume it was a man,” she said.

“When Tim Peake went into space, some people simply forgot about me. A man going first would be the norm, so I’m thrilled that I got to upset that order.”

https://www.cnn.com/2020/01/06/uk/helen-sharman-aliens-exist-scli-scn-gbr-intl/index.html

For the first time, physicists have calculated exactly what kind of singularity lies at the center of a realistic black hole.

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by Steve Nadis

In January 1916, Karl Schwarzschild, a German physicist who was stationed as a soldier on the eastern front, produced the first exact solution to the equations of general relativity, Albert Einstein’s radical, two-month-old theory of gravity. General relativity portrayed gravity not as an attractive force, as it had long been understood, but rather as the effect of curved space and time. Schwarzschild’s solution revealed the curvature of space-time around a stationary ball of matter.

Curiously, Schwarzschild noticed that if this matter were confined within a small enough radius, there would be a point of infinite curvature and density — a “singularity” — at the center.

Infinities cropping up in physics are usually cause for alarm, and neither Einstein, upon learning of the soldier’s result, nor Schwarzschild himself believed that such objects really exist. But starting in the 1970s, evidence mounted that the universe contains droves of these entities — dubbed “black holes” because their gravity is so strong that nothing going into them, not even light, can come out. The nature of the singularities inside black holes has been a mystery ever since.

Recently, a team of researchers affiliated with Harvard University’s Black Hole Initiative (BHI) made significant progress on this puzzle. Paul Chesler, Ramesh Narayan and Erik Curiel probed the interiors of theoretical black holes that resemble those studied by astronomers, seeking to determine what kind of singularity is found inside. A singularity is not a place where quantities really become infinite, but “a place where general relativity breaks down,” Chesler explained. At such a point, general relativity is thought to give way to a more exact, as yet unknown, quantum-scale description of gravity. But there are three different ways in which Einstein’s theory can go haywire, leading to three different kinds of possible singularities. “Knowing when and where general relativity breaks down is useful in knowing what theory [of quantum gravity] lies beyond it,” Chesler said.

The BHI group built on a major advance achieved in 1963, when the mathematician Roy Kerr solved Einstein’s equations for a spinning black hole — a more realistic situation than the one Schwarzschild took on since practically everything in the universe rotates. This problem was harder than Schwarzschild’s, because rotating objects have bulges in the center and therefore lack spherical symmetry. Kerr’s solution unambiguously described the region outside a spinning black hole, but not its interior.

Kerr’s black hole was still somewhat unrealistic, as it occupied a space devoid of matter. This, the BHI researchers realized, had the effect of making the solution unstable; the addition of even a single particle could drastically change the black hole’s interior space-time geometry. In an attempt to make their model more realistic and more stable, they sprinkled matter of a special kind called an “elementary scalar field” in and around their theoretical black hole. And whereas the original Kerr solution concerned an “eternal” black hole that has always been there, the black holes in their analysis formed from gravitational collapse, like the ones that abound in the cosmos.

First, Chesler, Narayan and Curiel tested their methodology on a charged, non-spinning, spherical black hole formed from the gravitational collapse of matter in an elementary scalar field. They detailed their findings in a paper posted on the scientific preprint site arxiv.org in February. Next, Chesler tackled the more complicated equations pertaining to a similarly formed rotating black hole, reporting his solo results three months later.

Their analyses showed that both types of black holes contain two distinct kinds of singularities. A black hole is encased within a sphere called an event horizon: Once matter or light crosses this invisible boundary and enters the black hole, it cannot escape. Inside the event horizon, charged stationary and rotating black holes are known to have a second spherical surface of no return, called the inner horizon. Chesler and his colleagues found that for the black holes they studied, a “null” singularity inevitably forms at the inner horizon, a finding consistent with prior results. Matter and radiation can pass through this kind of singularity for most of the black hole’s lifetime, Chesler explained, but as time goes on the space-time curvature grows exponentially, “becoming infinite at infinitely late times.”

The physicists most wanted to find out whether their quasi-realistic black holes have a central singularity — a fact that had only been established for certain for simple Schwarzschild black holes. And if there is a central singularity, they wanted to determine whether it is “spacelike” or “timelike.” These terms derive from the fact that once a particle approaches a spacelike singularity, it is not possible to evolve the equations of general relativity forward in time; evolution is only allowed along the space direction. Conversely, a particle approaching a timelike singularity will not inexorably be drawn inside; it still has a possible future and can therefore move forward in time, although its position in space is fixed. Outside observers cannot see spacelike singularities because light waves always move into them and never come out. Light waves can come out of timelike singularities, however, making them visible to outsiders.

Of these two types, a spacelike singularity may be preferable to physicists because general relativity only breaks down at the point of singularity itself. For a timelike singularity, the theory falters everywhere around that point. A physicist has no way of predicting, for instance, whether radiation will emerge from a timelike singularity and what its intensity or amplitude might be.

The group found that for both types of black holes they examined, there is indeed a central singularity, and it is always spacelike. That was assumed to be the case by many, if not most, astrophysicists who held an opinion, Chesler noted, “but it was not known for certain.”

The physicist Amos Ori, a black hole expert at the Technion in Haifa, Israel, said of Chesler’s new paper, “To the best of my knowledge, this is the first time that such a direct derivation has been given for the occurrence of a spacelike singularity inside spinning black holes.”

Gaurav Khanna, a physicist at the University of Massachusetts, Dartmouth, who also investigates black hole singularities, called the BHI team’s studies “great progress — a quantum leap beyond previous efforts in this area.”

While Chesler and his collaborators have strengthened the case that astrophysical black holes have spacelike singularities at their cores, they haven’t proved it yet. Their next step is to make more realistic calculations that go beyond elementary scalar fields and incorporate messier forms of matter and radiation.

Chesler stressed that the singularities that appear in black hole calculations should disappear when physicists craft a quantum theory of gravity that can handle the extreme conditions found at those points. According to Chesler, the act of pushing Einstein’s theory to its limits and seeing exactly how it fails “can guide you in constructing the next theory.”

https://www.quantamagazine.org/black-hole-singularities-are-as-inescapable-as-expected-20191202/?utm_source=Nature+Briefing&utm_campaign=6cddda34dd-briefing-dy-20191206&utm_medium=email&utm_term=0_c9dfd39373-6cddda34dd-44039353

How a Meteorite Ruined an Alabama Woman’s Afternoon 65 Years Ago

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Ann Hodges (center) poses with her meteorite, underneath the point where it crashed through her house, with Sylacauga, Alabama mayor Ed Howard (left) and the town’s police chief W.D. Ashcraft. Hodges was struck by the meteorite while on her couch on Nov. 30, 1954. She donated it to the University of Alabama’s Museum of Natural History in 1956.

By Chelsea Gohd

Sixty-five years ago, a few days after Thanksgiving, Ann Hodges was snuggled up on the sofa in her Alabama home when a 4.5-billion-year-old meteorite crashed through the ceiling and struck the left side of her body. Not the best interruption to the holiday season.

The cosmic event, which took place on Nov. 30, 1954, was the first known reported instance of a human being struck by a meteorite and suffering an injury. The softball-size space rock, weighing about 8.5 lbs. (3.8 kilograms), burst through the roof of Hodges’ house in Sylacauga at 2:46 p.m. local time, bouncing off a large radio console before striking her and leaving a large, dark bruise.

The meteorite that struck Hodges, who was 31 at the time, turned out to be one-half of a larger rock that split in two as it fell toward Earth. The piece that didn’t hit Hodges landed a few miles away and is now in the collections of the Smithsonian’s National Museum of Natural History. In 2017, a 10.3-gram piece of the space rock that hit Hodges sold at auction for $7,500.

Before it ended up leaving a serious welt on Hodges’ side, people across eastern Alabama say they saw a bright light in the sky. Reports poured in of a reddish light, and some observers even described a fireball that trailed smoke and left an arc of light in the afternoon sky. After Hodges was struck and the meteorite landed, she and her mother, who was home at the time, tried to figure out what had happened.

Dust filled the house after the crash, but as it settled and they spotted the rock and the enormous bruise on Hodges, the two women called the police and fire department.

Now, as a local geologist was called to the scene to verify what the object was, word quickly spread about what happened. However, the event occurred in 1954, and not everyone was convinced that this strange rock was a meteorite. Some thought it could’ve been debris from a plane crash, and some thought it could have even come from what was then the Soviet Union.

Still, despite a few skeptics, people from all over flocked to Hodges’ home to see the woman hit by a space rock, a crowd that Hodges’ husband found as he returned from work that night. “We had a little excitement around here today,” Ann Hodges told the Associated Press. “I haven’t been able to sleep since I was hit,” she said. With all of this commotion around her, Hodges was soon hospitalized, though, despite the massive mark on her side, was not too seriously injured.

“Think of how many people have lived throughout human history,” Michael Reynolds, who wrote the book “Falling Stars: A Guide to Meteors and Meteorites,” said to National Geographic. “You have a better chance of getting hit by a tornado and a bolt of lightning and a hurricane all at the same time.”

Shockingly, Hodges is not the only person to have been hit by a meteorite, but it is still exceptionally rare.

In 2009, a 14-year-old German boy, Gerrit Blank, was hit in the hand by a pea-size meteorite. While he wasn’t seriously injured, the rock did leave a scar and gave the boy quite a fright. “When it hit me it knocked me flying and then was still going fast enough to bury itself into the road,” said Blank.

https://www.space.com/meteorite-hit-alabama-woman-65-years-ago.html?utm_source=notification

Sugars essential to life detected in meteorites, a first

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Scientists found three bio-essential sugars, including ribosome, in samples from a pair of meteorites. Photo by Yoshihiro Furukawa

By Brooks Hays

For the first time, scientists have identified sugars essential to life inside meteorites.

The discovery, described this week in the journal PNAS, supports the theory that a bombardment of meteorites provided ancient Earth with the building blocks required for the origin of life.

An international team of scientists identified a trio of bio-essential sugars, including ribose, arabinose and xylose, inside two carbon-rich meteorites.

“Ribose is an essential sugar for present life as a building block of RNA, which could have both stored information and catalyzed reactions in primitive life on Earth,” researchers wrote in their new paper.

Scientists have previously found other biomolecules in meteorites, including amino acids, which form proteins, and nucleobases, the building blocks of DNA and RNA. But until now, scientists hadn’t been able to find sugars.

“The research provides the first direct evidence of ribose in space and the delivery of the sugar to Earth,” Yoshihiro Furukawa, researcher at Tohoku University in Japan, said in news release. “The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth which possibly led to the origin of life.”

To find the sugars, scientists used gas chromatography mass spectrometry to analyze the chemical components of powdered meteorite samples. The method identifies molecules by measuring their mass and electric charge.

The research team used isotopic analysis to confirm the sugar’s interplanetary origins. Their tests showed a higher concentration of carbon 13 in the sugars. Carbon 13 is a heavier carbon isotope that is less abundant in terrestrial samples.

While planetary scientists continue to search for signs of life on other planets, researchers are still trying to figure out how biology — or the first living organisms — emerged from non-biological chemical processes here on Earth.

While some scientists theorize that RNA and DNA evolved together, or emerged simultaneously, others estimate that RNA came first and evolved DNA. RNA can catalyze chemical reactions, as well as make copies of itself, something DNA can’t do. Some research suggests metabolism preceded both RNA and DNA.

The latest discovery supports the theory that RNA was the initial conductor of life’s assembly.

“The sugar in DNA, 2-deoxyribose, was not detected in any of the meteorites analyzed in this study,” said study co-author Danny Glavin, researcher at NASA’s Goddard Space Flight Center. “This is important since there could have been a delivery bias of extraterrestrial ribose to the early Earth which is consistent with the hypothesis that RNA evolved first.”

Scientists hope to gain additional insights into life’s origins as they probe other meteorite samples for evidence of sugar’s abundance.

https://www.upi.com/Science_News/2019/11/19/Sugars-essential-to-life-detected-in-meteorites-a-first/4421574186445/?sl=1