2685: Where Do Black Holes Lead?

SCIENCE

Where does a black hole go?

So there you are, about to leap into a black hole. What could possibly await should — against all odds — you somehow survive? Where would you end up and what tantalizing tales would you be able to regale if you managed to clamor your way back?

The simple answer to all of these questions is, as Professor Richard Massey explains, “Who knows?” As a Royal Society research fellow at the Institute for Computational Cosmology at Durham University, Massey is fully aware that the mysteries of black holes run deep. “Falling through an event horizon is literally passing beyond the veil — once someone falls past it, nobody could ever send a message back,” he said. “They’d be ripped to pieces by the enormous gravity, so I doubt anyone falling through would get anywhere.”

If that sounds like a disappointing — and painful — answer, then it is to be expected. Ever since Albert Einstein’s general theory of relativity was considered to have predicted black holes by linking space-time with the action of gravity, it has been known that black holes result from the death of a massive star leaving behind a small, dense remnant core. Assuming this core has more than roughly three-times the mass of the sun, gravity would overwhelm to such a degree that it would fall in on itself into a single point, or singularity, understood to be the black hole’s infinitely dense core.

Related: 9 Ideas About Black Holes That Will Blow Your Mind

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The resulting uninhabitable black hole would have such a powerful gravitational pull that not even light could avoid it. So, should you then find yourself at the event horizon — the point at which light and matter can only pass inward, as proposed by the German astronomer Karl Schwarzschild — there is no escape. According to Massey, tidal forces would reduce your body into strands of atoms (or ‘spaghettification’, as it is also known) and the object would eventually end up crushed at the singularity. The idea that you could pop out somewhere — perhaps at the other side — seems utterly fantastical.

What about a wormhole?

Or is it? Over the years scientists have looked into the possibility that black holes could be wormholes to other galaxies. They may even be, as some have suggested, a path to another universe.

Such an idea has been floating around for some time: Einstein teamed up with Nathan Rosen to theorise bridges that connect two different points in space-time in 1935. But it gained some fresh ground in the 1980s when physicist Kip Thorne — one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity — raised a discussion about whether objects could physically travel through them.

“Reading Kip Thorne’s popular book about wormholes is what first got me excited about physics as a child,” Massey said. But it doesn’t seem likely that wormholes exist.

Indeed, Thorne, who lent his expert advice to the production team for the Hollywood movie Interstellar, wrote: “We see no objects in our universe that could become wormholes as they age,” in his book “The Science of Interstellar” (W.W. Norton and Company, 2014). Thorne told Space.com that journeys through these theoretical tunnels would most likely remain science fiction, and there is certainly no firm evidence that a black hole could allow for such a passage.

Artist’s concept of a wormhole. If wormholes exist, they might lead to another universe. But, there’s no evidence that wormholes are real or that a black hole would act like one.
(Image credit: Shutterstock)

But, the problem is that we can’t get up close to see for ourselves. Why, we can’t even take photographs of anything that takes place inside a black hole — if light cannot escape their immense gravity, then nothing can be snapped by a camera. As it stands, theory suggests that anything which goes beyond the event horizon is simply added to the black hole and, what’s more, because time distorts close to this boundary, this will appear to take place incredibly slowly, so answers won’t be quickly forthcoming.

“I think the standard story is that they lead to the end of time,” said Douglas Finkbeiner, professor of astronomy and physics at Harvard University. “An observer far away will not see their astronaut friend fall into the black hole. They’ll just get redder and fainter as they approach the event horizon [as a result of gravitational red shift]. But the friend falls right in, to a place beyond ‘forever.’ Whatever that means.”

Maybe a black hole leads to a white hole

Certainly, if black holes do lead to another part of a galaxy or another universe, there would need to be something opposite to them on the other side. Could this be a white hole — a theory put forward by Russian cosmologist Igor Novikov in 1964? Novikov proposed that a black hole links to a white hole that exists in the past. Unlike a black hole, a white hole will allow light and matter to leave, but light and matter will not be able to enter.

Scientists have continued to explore the potential connection between black and white holes. In their 2014 study published in the journal Physical Review D, physicists Carlo Rovelli and Hal M. Haggard claimed that “there is a classic metric satisfying the Einstein equations outside a finite space-time region where matter collapses into a black hole and then emerges from a while hole.” In other words, all of the material black holes have swallowed could be spewed out, and black holes may become white holes when they die.

Far from destroying the information that it absorbs, the collapse of a black hole would be halted. It would instead experience a quantum bounce, allowing information to escape. Should this be the case, it would shed some light on a proposal by former Cambridge University cosmologist and theoretical physicist Stephen Hawking who, in the 1970s, explored the possibility that black holes emit particles and radiation — thermal heat — as a result of quantum fluctuations.

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“Hawking said a black hole doesn’t last forever,” Finkbeiner said. Hawking calculated that the radiation would cause a black hole to lose energy, shrink and disappear, as described in his 1976 paper published in Physical Review D. Given his claims that the radiation emitted would be random and contain no information about what had fallen in, the black hole, upon its explosion, would erase loads of information.

This meant Hawking’s idea was at odds with quantum theory, which says information can’t be destroyed. Physics states information just becomes more difficult to find because, should it become lost, it becomes impossible to know the past or the future. Hawking’s idea led to the ‘black hole information paradox’ and it has long puzzled scientists. Some have said Hawking was simply wrong, and the man himself even declared he had made an error during a scientific conference in Dublin in 2004.

So, do we go back to the concept of black holes emitting preserved information and throwing it back out via a white hole? Maybe. In their 2013 study published in Physical Review Letters, Jorge Pullin at Louisiana State University and Rodolfo Gambini at the University of the Republic in Montevideo, Uruguay, applied loop quantum gravity to a black hole and found that gravity increased towards the core but reduced and plonked whatever was entering into another region of the universe. The results gave extra credence to the idea of black holes serving as a portal. In this study, singularity does not exist, and so it doesn’t form an impenetrable barrier that ends up crushing whatever it encounters. It also means that information doesn’t disappear.

Maybe black holes go nowhere

Yet physicists Ahmed Almheiri, Donald Marolf, Joseph Polchinski and James Sully still believed Hawking could have been on to something. They worked on a theory that became known as the AMPS firewall, or the black hole firewall hypothesis. By their calculations, quantum mechanics could feasibly turn the event horizon into a giant wall of fire and anything coming into contact would burn in an instant. In that sense, black holes lead nowhere because nothing could ever get inside.

This, however, violates Einstein’s general theory of relativity. Someone crossing the event horizon shouldn’t actually feel any great hardship because an object would be in free fall and, based on the equivalence principle, that object — or person — would not feel the extreme effects of gravity. It could follow the laws of physics present elsewhere in the universe, but even if it didn’t go against Einstein’s principle it would undermine quantum field theory or suggest information can be lost.

Related: 11 Fascinating Facts About Our Milky Way Galaxy

Artist’s impression of a tidal disruption event which occurs when a star passes too close to a supermassive black hole.
(Image credit: All About Space magazine)

A black hole of uncertainty

Step forward Hawking once more. In 2014, he published a study in which he eschewed the existence of an event horizon — meaning there is nothing there to burn — saying gravitational collapse would produce an ‘apparent horizon’ instead.

This horizon would suspend light rays trying to move away from the core of the black hole, and would persist for a “period of time.” In his rethinking, apparent horizons temporarily retain matter and energy before dissolving and releasing them later down the line. This explanation best fits with quantum theory — which says information can’t be destroyed — and, if it was ever proven, it suggests that anything could escape from a black hole.

Hawking went as far as saying black holes may not even exist. “Black holes should be redefined as metastable bound states of the gravitational field,” he wrote. There would be no singularity, and while the apparent field would move inwards due to gravity, it would never reach the center and be consolidated within a dense mass.

And yet anything which is emitted will not be in the form of the information swallowed. It would be impossible to figure out what went in by looking at what is coming out, which causes problems of its own — not least for, say, a human who found themselves in such an alarming position. They’d never feel the same again!

One thing’s for sure, this particular mystery is going to swallow up many more scientific hours for a long time to come. Rovelli and Francesca Vidotto recently suggested that a component of dark matter could be formed by remnants of evaporated black holes, and Hawking’s paper on black holes and ‘soft hair’ was released in 2018, and describes how zero-energy particles are left around the point of no return, the event horizon — an idea that suggests information is not lost but captured.

This flew in the face of the no-hair theorem which was expressed by physicist John Archibald Wheeler and worked on the basis that two black holes would be indistinguishable to an observer because none of the special particle physics pseudo-charges would be conserved. It’s an idea that has got scientists talking, but there is some way to go before it’s seen as the answer for where black holes lead. If only we could find a way to leap into one.

livescience
21/09/2019
By David Crookes – All About Space magazine

 

Something Is Killing the Universe’s Most Extreme Galaxies

And scientists are looking for the killer.

The spiral galaxy NGC 4330 is located in the Virgo Cluster. Ram-pressure stripped hot gas is shown in red, and a blue overlay shows star-forming gas.
(Image: © Fossatie et al. (2018),

In the most extreme regions of the universe, galaxies are being killed. Their star formation is being shut down and astronomers want to know why.

The first ever Canadian-led large project on one of the world’s leading telescopes is hoping to do just that. The new program, called the Virgo Environment Traced in Carbon Monoxide survey (VERTICO), is investigating, in brilliant detail, how galaxies are killed by their environment.

As VERTICO’s principal investigator, I lead a team of 30 experts that are using the Atacama Large Millimeter Array (ALMA) to map the molecular hydrogen gas, the fuel from which new stars are made, at high resolution across 51 galaxies in our nearest galaxy cluster, called the Virgo Cluster.

Commissioned in 2013 at a cost of US$1.4 billion, ALMA is an array of connected radio dishes at an altitude of 5,000 metres in the Atacama Desert of northern Chile. It is an international partnership between Europe, the United States, Canada, Japan, South Korea, Taiwan and Chile. The largest ground-based astronomical project in existence, ALMA is the most advanced millimetre wavelength telescope ever built and ideal for studying the clouds of dense cold gas from which new stars form, which cannot be seen using visible light.

Large ALMA research programs such as VERTICO are designed to address strategic scientific issues that will lead to a major advance or breakthrough in the field.

Galaxy clusters

Where galaxies live in the universe and how they interact with their surroundings (the intergalactic medium that surrounds them) and each other are major influences on their ability to form stars. But precisely how this so-called environment dictates the life and death of galaxies remains a mystery.

Galaxy clusters are the most massive and most extreme environments in the universe, containing many hundreds or even thousands of galaxies. Where you have mass, you also have gravity and the huge gravitational forces present in clusters accelerates galaxies to great speeds, often thousands of kilometres-per-second, and superheats the plasma in between galaxies to temperatures so high that it glows with X-ray light.

In the dense, inhospitable interiors of these clusters, galaxies interact strongly with their surroundings and with each other. It is these interactions that can kill off — or quench — their star formation.

Understanding which quenching mechanisms shut off star formation and how they do it is the main focus of the VERTICO collaboration’s research.

The life cycle of galaxies

As galaxies fall through clusters, the intergalactic plasma can rapidly remove their gas in a violent process called ram pressure stripping. When you remove the fuel for star formation, you effectively kill the galaxy, turning it into a dead object in which no new stars are formed.

In addition, the high temperature of clusters can stop hot gas cooling and condensing onto galaxies. In this case, the gas in the galaxy isn’t actively removed by the environment but is consumed as it forms stars. This process leads to a slow, inexorable shut down in star formation known, somewhat morbidly, as starvation or strangulation.

While these processes vary considerably, each leaves a unique, identifiable imprint on the galaxy’s star-forming gas. Piecing these imprints together to form a picture of how clusters drive changes in galaxies is a major focus of the VERTICO collaboration. Building on decades of work to provide insight into how environment drives galaxy evolution, we aim to add a critical new piece of the puzzle.

An ideal case study

The Virgo Cluster is an ideal location for such a detailed study of environment. It is our nearest massive galaxy cluster and is in the process of forming, which means that we can get a snapshot of galaxies in different stages of their life cycles. This allows us to build up a detailed picture of how star formation is shut off in cluster galaxies.

Galaxies in the Virgo cluster have been observed at almost every wavelength in the electromagnetic spectrum (for example, radio, optical and ultraviolet light), but observations of star-forming gas (made at at millimeter wavelengths) with the required sensitivity and resolution do not exist yet. As one of the largest galaxy surveys on ALMA to date, VERTICO will provide high resolution maps of molecular hydrogen gas — the raw fuel for star formation — for 51 galaxies.

With ALMA data for this large sample of galaxies, it will be possible to reveal exactly which quenching mechanisms, ram pressure stripping or starvation, are killing galaxies in extreme environments and how.

By mapping the star-forming gas in galaxies that are the smoking gun examples of environment-driven quenching, VERTICO will advance our current understanding of how galaxies evolve in the densest regions of the Universe.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

LiveScience
By Toby Brown – McMaster University
19/09/2019

 

2606: 3 Asteroids Are Zipping Past Earth Today

But don’t worry — they’re at least as far away as the moon is.

Hundreds of orbiting comets and asteroids are thought to present some risk of colliding with Earth, but the threat is typically very small.
(Image: © Shutterstock)

Three asteroids are expected to hurtle past Earth today (Sept. 9). One will pass as near as 310,000 miles (500,000 kilometers) — closer than any potential asteroid near-miss for the next three months.

Asteroid 2019 QZ3 flew by at 6:49 a.m. ET; asteroid 2019 RG2 follows at around 3:13 p.m. ET, and the third, asteroid 2019 QY4, flashes past at 9:10 p.m. ET, the International Business Times reported.

QZ3 is the biggest of the trio, with a diameter of 220 feet (67 meters), while RG2 and QY4, respectively measure approximately 66 feet (20 m) and 52 feet (16 m) in length, according to NASA’s Center for Near-Earth Object Studies (CNEOS).

Space rocks such as these, known as near-Earth objects (NEOS), are nudged by the gravity of neighboring planets into orbital paths that carry them fairly close to our cosmic address. But “close” in space is a relative term: At the closest point in their passage, all three of today’s asteroid visitors will be farther from Earth than the moon is, according to CNEOS.

RG2 is the fastest asteroid, speeding by at a velocity of nearly 50,000 miles per hour (80,000 kilometers/hour), while QY4 is moving at just over 17,000 mph (27,000 km/h). QZ3 is the slowpoke of the group, at 16,700 mph (26,800 km/h), according to IBT. Though QZ3 is the biggest asteroid, it is also the furthest from Earth, at a distance of approximately 2.3 million miles from our planet, CNEOS reported.

Another asteroid — 2006 QV89 — was previously thought to potentially follow a trajectory that could slam into Earth, with a 1-in-7,299 chance of an impact on Sept. 9. But experts announced in July that the asteroid did not appear in the area of the sky where it would have shown up if it were on a collision course with our planet, representatives with the European Southern Observatory (ESO) said in a statement.

CNEOS representatives confirmed on Aug. 15 that QV89 was no threat to Earth, and that the asteroid would instead rocket past our planet on Sept. 27 “at a comfortable distance of 4.3 million miles (6.9 million km), about 18 times the distance of the Moon.”

Currently, there are 878 NEOs that demonstrate some risk — however small it might be — of colliding with Earth, according to a list maintained by the European Space Agency (ESA). Of these, the biggest (and second on the list) is asteroid 1979 XB. Measuring about 2,300 feet (700 m) in length and traveling at more than 58,000 mph (93,300 km/h), the massive space rock is expected to come calling on Dec. 14, 2113, ESA reported.

Live Science
By Mindy Weisberger – Senior Writer
09/09/2019

 

‘Einstein’s Biggest Blunder’ May Have Finally Been Fixed

The cosmological constant has plagued physicists for more than a century.

There is a fundamental problem in physics.

A single number, called the cosmological constant, bridges the microscopic world of quantum mechanics and the macroscopic world of Einstein’s theory of general relativity. But neither theory can agree on its value.

In fact, there’s such a huge discrepancy between the observed value of  this constant and what theory predicts that it is widely considered the worst prediction in the history of physics. Resolving the discrepancy may be the most important goal of theoretical physics this century.

Lucas Lombriser, an assistant professor of theoretical physics at the University of Geneva in Switzerland, has introduced a new way of evaluating Albert Einstein’s equations of gravity to find a value for the cosmological constant that closely matches its observed value. He published his method online in the Oct. 10 issue of the journal Physics Letters B.

Related: The Biggest Unsolved Mysteries in Physics


An illustration of galaxies bending the fabric of space-time (green), and the smooth effect of dark energy (purple), which dominates the effects of gravity.(Image: © NASA/JPL-Caltech)

How Einstein’s biggest blunder became dark energy

The story of the cosmological constant began more than a century ago when Einstein presented a set of equations, now known as the Einstein field equations, that became the framework of his theory of general relativity. The equations explain how matter and energy warp the fabric of space and time to create the force of gravity. At the time, both Einstein and astronomers agreed that the universe was fixed in size and that the overall space between galaxies did not change. However, when Einstein applied general relativity to the universe as a whole, his theory predicted an unstable universe that would either expand or contract. To force the universe to be static, Einstein tacked on the cosmological constant.

Nearly a decade later, another physicist, Edwin Hubble, discovered that our universe is not static, but expanding. The light from distant galaxies showed they were all moving away from each other. This revelation persuaded Einstein to abandon the cosmological constant from his field equations as it was no longer necessary to explain an expanding universe. Physics lore has it that Einstein later confessed that his introduction of the cosmological constant was perhaps his greatest blunder.

In 1998, observations of distant supernovas showed the universe wasn’t just expanding, but the expansion was speeding up. Galaxies were accelerating away from each other as if some unknown force was overcoming gravity and shoving those galaxies apart. Physicists have named this enigmatic phenomenon dark energy, as its true nature remains a mystery.

In a twist of irony, physicists once again reintroduced the cosmological constant into Einstein’s field equations to account for dark energy. In the current standard model of cosmology, known as ΛCDM (Lambda CDM), the cosmological constant is interchangeable with dark energy. Astronomers have even estimated its value based on observations of distant supernovas and fluctuations in the cosmic microwave background. Although the value is absurdly small (on the order of 10^-52 per square meter), over the scale of the universe, it is significant enough to explain the accelerated expansion of space.

“The cosmological constant [or dark energy] currently constitutes about 70% of the energy content in our universe, which is what we can infer from the observed accelerated expansion that our universe is presently undergoing. Yet this constant is not understood,” Lombriser said. “Attempts to explain it have failed, and there seems to be something fundamental that we are missing in how we understand the cosmos. Unraveling this puzzle is one of the major research areas in modern physics. It is generally anticipated that resolving the issue may lead us to a more fundamental understanding of physics.”

Related: 8 Ways You Can See Einstein’s Theory of Relativity in Real Life

The worst theoretical prediction in the history of physics

The cosmological constant is thought to represent what physicists call “vacuum energy.” Quantum-field theory states that even in a completely empty vacuum of space, virtual particles pop in and out of existence and create energy — a seemingly absurd idea, but one that has been observed experimentally. The problem arises when physicists attempt to calculate its contribution to the cosmological constant. Their result differs from observations by a mind-boggling factor of 10^121 (that’s 10 followed by 120 zeroes), the largest discrepancy between theory and experiment in all of physics.

Such a disparity has caused some physicists to doubt Einstein’s original equations of gravity; some have even suggested alternative models of gravity. However, further evidence of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) have only strengthened general relativity and dismissed many of these alternative theories. Which is why instead of rethinking gravity, Lombriser took a different approach to solve this cosmic puzzle.

“The mechanism I propose does not modify Einstein’s field equations,” Lombriser said. Instead, “it adds an additional equation on top of Einstein’s field equations.”

The gravitational constant, which was first used in Isaac Newton’s laws of gravity and now an essential part of Einstein’s field equations, describes the magnitude of  the gravitational force between objects. It is considered one of the fundamental constants of physics, eternally unchanged since the beginning of the universe. Lombriser has made the dramatic assumption that this constant can change.

In Lombriser’s modification of general relativity, the gravitational constant remains the same within our observable universe but may vary beyond it. He suggests a multiverse scenario where there may be patches of the universe invisible to us that have different values for the fundamental constants.

This variation of gravity gave Lombriser an additional equation that relates the cosmological constant to the average sum of matter across space-time. After he accounted for the estimated mass of all the galaxies, stars and dark matter of the universe, he could solve that new equation to obtain a new value for the cosmological constant — one that closely agrees with observations.

Using a new parameter, ΩΛ (omega lambda), that expresses the fraction of the universe made of dark matter, he found the universe is made up of about 74% dark energy. This number closely matches the value of 68.5% estimated from observations — a tremendous improvement over the huge disparity found by quantum field theory.

Although Lombriser’s framework might solve the cosmological constant problem, there’s currently no way to test it. But in the future, if experiments from other theories validate his equations,  it could mean a major leap in our understanding of dark energy and provide a tool to solve other cosmic mysteries.

Originally published on Live Science.
By Tim Childers – Live Science Contributor
06/09/2019

 

Earth’s Core Has Been Leaking for 2.5 Billion Years and Geologists Don’t Know Why

Credit: Shutterstock

Earth’s scorching core is not a loner — it has been caught mingling with other, underworldly layers. That’s according to a new study that found the innermost part of the planet leaks some of its contents into mantle plumes, some of which eventually reach Earth’s surface.

This discovery helps settle a debate that’s been raging for decades: whether the core and mantle exchange any material, the researchers said.

“Our findings suggest some core material does transfer into the base of these mantle plumes, and the core has been leaking this material for the past 2.5 billion years,” the researchers wrote in The Conversation, a website where scientists write about their research for the public. [Photos: The World’s Weirdest Geological Formations]

The finding was made possible by the metal tungsten (W), element 74 on the periodic table. If tungsten were to make a dating profile, it would note that it’s a siderophile, or “iron lover.” So, it’s no surprise that a lot of tungsten hangs out in Earth’s core, which is made primarily of iron and nickel.

On its profile, tungsten would also list that it has a few isotopes (an element with a different number of neutrons in its nucleus), including W-182 (with 108 neutrons) and W-184 (with 110 neutrons). While devising their study, the researchers realized that these isotopes could help them solve the core-leaking question.

Another element, hafnium (Hf), is a lithophile, meaning it loves rocks and can be found in Earth’s silicate-rich mantle. With a half-life of 8.9 million years, hafnium’s radioactive isotope Hf-182 decays into W-182. This means that the mantle should have more W-182 than the core does, the scientists reasoned.

“Therefore, chemical exchange between the core and the source of mantle plumes could be detectable in the 182W/184W ratio of ocean island basalts,” which come from plumes in the mantle, the researchers wrote in the study.

But this difference in tungsten would be incredibly small: The tungsten-182 composition in the mantle and core were expected to differ by only about 200 parts per million (ppm). “Fewer than five laboratories in the world can do this type of analysis,” the researchers wrote in The Conversation.

Furthermore, it’s not easy to study the core, because it begins at a depth of about 1,800 miles (2,900 kilometers) underground. To put that into perspective, the deepest hole humans have ever dug is the Kola Superdeep Borehole in Russia, which has a depth of about 7.6 miles (12.3 km).

So, the researchers studied the next best thing: rocks that oozed to Earth’s surface from the deep mantle at the Pilbara Craton in Western Australia, and the Réunion Island and Kerguelen Archipelago hotspots in the Indian Ocean.

The amount of tungsten in these rocks revealed a leak from the core. Over Earth’s lifetime, there was a big change in the W-182-to-W-184 ratio in Earth’s mantle, the researchers found. Oddly, Earth’s oldest rocks have a higher W-182-to-W-184 ratio than most modern-day rocks do, they discovered.

“The change in the 182W/184W ratio of the mantle indicates that tungsten from the core has been leaking into the mantle for a long time,” the researchers wrote in The Conversation. [Photos: Geologists Home-Brew Lava]

Earth is about 4.5 billion years old. The planet’s oldest mantle rocks, however, didn’t have any significant changes in tungsten isotopes. This suggests that from 4.3 billion to 2.7 billion years ago, there was little or no exchange of material from the core to the upper mantle, the researchers said.

But in the past 2.5 billion years, the tungsten isotope composition in the mantle has changed substantially. Why did this happen? If mantle plumes are rising from the core-mantle boundary, then perhaps, like a see-saw, material from Earth’s surface is going down into the deep mantle, the researchers said. This surface material has oxygen in it, an element that can affect tungsten, the researchers said.

Subduction, the term used for rocks from Earth’s surface descending into the mantle, takes oxygen-rich material from the surface into the deep mantle as an integral component of plate tectonics,” the researchers wrote in The Conversation. “Experiments show that [an] increase in oxygen concentration at the core-mantle boundary could cause tungsten to separate out of the core and into the mantle.”

Or, maybe as the inner core solidified after Earth formed, the oxygen concentration in the outer core increased, the researchers said. “In this case, our new results could tell us something about the evolution of the core, including the origin of Earth’s magnetic field,” they wrote in The Conversation.

The study was published online June 20 in the journal Geochemical Perspectives Letters.

Originally published on Live Science.

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2174: Breaks in the Perfect Symmetry of the Universe Could Be a Window Into Completely New Physics

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The bible of particle physics is dying for an upgrade. And physicists may have just the thing: Some particles and forces might look in the mirror and not recognize themselves. That, in itself, would send the so-called Standard Model into a tailspin.

Just about all fundamental reactions between the universe’s subatomic particles look the same when they are flipped around in a mirror. The mirror-image, called parity, is then said to be symmetrical, or to have parity symmetry, in physics speak.

Of course, not everyone follows the rules. We know that, for instance, reactions involving the weak nuclear force, which is also weird for a whole bunch of other reasons, violates parity symmetry. So it stands to reason other forces and particles in the quantum world are also rule-breakers in this area.

Physicists have some ideas about these other hypothetical reactions that wouldn’t look the same in the mirror and hence would violate parity symmetry. These strange reactions could point us toward new physics that could help us move past the Standard Model of particle physics, our current summary of all things subatomic.

Unfortunately, we will never see most of these strange reactions in our atom smashers and laboratories. The interactions are just too rare and weak to detect with our instruments, which are tuned to other kinds of interactions. But there might be some rare exceptions. Researchers at the world’s largest atom smasher, the Large Hadron Collider (LHC), located near Geneva, have been hunting for these rare interactions. So far, they’ve come up empty-handed, but even that result is illuminating. Those negative results help weed out fruitless hypotheses from consideration, allowing physicists to focus on more-promising avenues in the hunt for new physics. [18 Times Quantum Particles Blew Our Minds]

One of the most important concepts in all of physics is that of symmetry. You could even reasonably argue that physicists are just symmetry hunters. Symmetries reveal the fundamental laws of nature that govern the innermost workings of reality. Symmetry is a big deal.

So what is it? A symmetry means that if you change one element in a process or interaction, the process stays the same. Physicists then say that the process is symmetric with respect to that change. I’m being deliberately vague here because there are so many different kinds of symmetry. For example, sometimes you can change the sign of the charges on particles, sometimes you can run processes forward or backward in time, and sometimes you can run a mirror-image version of the process.

This last one, looking at a process in the mirror, is called the symmetry of parity. Most subatomic interactions in physics give you the exact same result whether they’re done right in front of you or in the mirror. But some interactions violate this symmetry, like the weak nuclear force, especially when neutrinos are produced in interactions involving that force.

Neutrinos always spin “backward” (in other words, the axis of their spin points away from their direction of motion), while antineutrinos spin “forward” (their axis of spin points straight ahead as they fly around). That means there are very subtle differences in the numbers of neutrinos and antineutrinos produced when you run a regular, versus a mirror-flipped experiment that relies on the weak nuclear force. [Strange Quarks and Muons, Oh My! Nature’s Tiniest Particles Dissected]

As far as we know, the weak nuclear force and the weak nuclear force alone violates the symmetry of parity. But maybe it’s not alone.

We know that physics beyond what we currently understand must exist. And some of those hypothetical ideas and concepts also violate the symmetry of parity. For example, some of these theories predict subtle asymmetries in otherwise-normal interactions that involve the kinds of particles the LHC typically examines.

Of course, these hypothetical ideas are exotic, complex and very hard to test. And in many cases, we’re not exactly sure what we’re looking for.

The problem is that while we know that our current conception of the particle world, called the Standard Model, is incomplete, we don’t know where to look for its replacement. Many physicists hoped that the LHC would reveal something — a new particle, a new interaction, anything at all — that would point us toward something new and exciting, but so far all those searches have failed.

Many of the former front-runner theories for what’s beyond the Standard Model (like supersymmetry) are slowly being ruled out. This is where parity-symmetry violation might come in handy.

Almost all common hypothetical extensions to the Standard Model include the limitation that only the weak nuclear force violates parity symmetry. (This is baked into the fundamental mathematics of the models, in case you were wondering how this works.) That means concepts like supersymmetry, axions and leptoquarks all keep this symmetry breaking exactly where it is, and nowhere else.

But look, folks, if these common extensions aren’t panning out, maybe it’s time to broaden our horizons.

For that reason, a team of researchers searched for parity violations in a cache of data released by the Compact Muon Solenoid (CMS) experiment at the LHC; they detailed their results in a study published April 29 to the preprint server arXiv. This was a pretty tricky search, since the LHC isn’t really set up to look for parity violations. But the researchers cleverly figured out a way to do it by examining the leftovers in interactions between other particles.

The result: No hints of parity violation were found. Hooray for the Standard Model (again). Though it’s a tad disappointing that this research didn’t open up a new frontier of physics, it will help clarify future searches. If we keep searching and still turn up no evidence for parity violation outside of the weak nuclear force, then we know that whatever lies beyond the Standard Model must have some of the same mathematical structures as that mainstay theory and allow only the weak nuclear force to look different in the mirror.

Originally published on Live Science.

By Paul Sutter, Astrophysicist

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2140: This Asteroid Has a 1-in-7,000 Chance of Hitting Earth This Fall

Credit: Shutterstock

This fall, Earth has about a 1-in-7,000 chance of getting an uninvited extraterrestrial visitor: asteroid 2006 QV89.

The space rock is expected to whiz by our planet on Sept. 9, 2019, according to European Space Agency’s (ESA) list of space objects that could collide with Earth. That list was updated online June 6. Out of 10 objects on the list, 2006 QV89 ranked fourth.

Compared to the 6-mile-long (10 kilometers) asteroid that killed the nonavian dinosaurs about 66 million years ago, 2006 QV89 is pretty dinky, measuring just 130 feet (40 meters) in diameter, or about the length of two bowling alleys placed end to end. [Images: Russian Meteor Explosion]

The ESA is monitoring the asteroid’s route, but the space rock is unlikely to careen into Earth. According to the ESA’s modeling, 2006 QV89 will likely get as close as about 4.2 million miles (6.7 million km) to the planet. To put that in perspective, the moon is 238,900 miles (384,400 km) away.

That said, there is a 1-in-7,299 chance that 2006 QV89 will hit the planet, the ESA said.

As its name suggests, asteroid 2006 QV89 was discovered on Aug. 29, 2006; it was spotted by the Catalina Sky Survey, an organization based at an observatory near Tucson, Arizona. The asteroid is actually quite a frequent visitor to our planet. After its 2019 flyby, the object is expected to swoop by Earth in 2032, 2045 and 2062, the ESA reported.

NASA, which also tracks near-Earth objects, paired up with the ESA last month to live-tweet information about how the government and scientists should handle an actual asteroid strike. However, fans of the movie “Armageddon” should forget about blowing up big asteroids with bombs. A study that came out in March in the journal Icarus found that the larger the asteroid, the harder it will be to blow up.

Originally published on Live Science.
By Laura Geggel, Associate Editor

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2120: Physicists Search for Monstrous Higgs Particle. It Could Seal the Fate of the Universe.

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We all know and love the Higgs boson — which to physicists’ chagrin has been mistakenly tagged in the media as the “God particle” — a subatomic particle first spotted in the Large Hadron Collider (LHC) back in 2012. That particle is a piece of a field that permeates all of space-time; it interacts with many particles, like electrons and quarks, providing those particles with mass, which is pretty cool.

But the Higgs that we spotted was surprisingly lightweight. According to our best estimates, it should have been a lot heavier. This opens up an interesting question: Sure, we spotted a Higgs boson, but was that the only Higgs boson? Are there more floating around out there doing their own things?

Though we don’t have any evidence yet of a heavier Higgs, a team of researchers based at the LHC, the world’s largest atom smasher, is digging into that question as we speak. And there’s talk that as protons are smashed together inside the ring-shaped collider, hefty Higgs and even Higgs particles made up of various types of Higgs could come out of hiding. [Beyond Higgs: 5 Elusive Particles That May Lurk in the Universe]

If the heavy Higgs does indeed exist, then we need to reconfigure our understanding of the Standard Model of particle physics with the newfound realization that there’s much more to the Higgs than meets the eye. And within those complex interactions, there might be a clue to everything from the mass of the ghostly neutrino particle to the ultimate fate of the universe.

Without the Higgs boson, pretty much the whole Standard Model comes crashing down. But to talk about the Higgs boson, we first need to understand how the Standard Model views the universe.

In our best conception of the subatomic world using the Standard Model, what we think of as particles aren’t actually very important. Instead, there are fields. These fields permeate and soak up all of space and time. There is one field for each kind of particle. So, there’s a field for electrons, a field for photons, and so on and so on. What you think of as particles are really local little vibrations in their particular fields. And when particles interact (by, say, bouncing off of each other), it’s really the vibrations in the fields that are doing a very complicated dance. [The 12 Strangest Objects in the Universe]

The Higgs boson has a special kind of field. Like the other fields, it permeates all of space and time, and it also gets to talk and play with everybody else’s fields.

But the Higgs’ field has two very important jobs to do that can’t be achieved by any other field.

Its first job is to talk to the W and Z bosons (via their respective fields), the carriers of the weak nuclear force. By talking to these other bosons, the Higgs is able to give them mass and make sure that they stay separated from the photons, the carriers of electromagnetic force. Without the Higgs boson running interference, all these carriers would be merged together and those two forces would merge together.

The other job of the Higgs boson is to talk to other particles, like electrons; through these conversations, it also gives them mass. This all works out nicely, because we have no other way of explaining the masses of these particles.

This was all worked out in the 1960s through a series of complicated but assuredly elegant math, but there’s just one tiny hitch to the theory: There’s no real way to predict the exact mass of the Higgs boson. In other words, when you go looking for the particle (which is the little local vibration of the much larger field) in a particle collider, you don’t know exactly what and where you’re going to find it. [The 11 Most Beautiful Mathematical Equations]

In 2012, scientists at the LHC announced the discovery of the Higgs boson after finding a few of the particles that represent the Higgs’ field had been produced when protons were smashed into one another at near light-speed. These particles had a mass of 125 gigaelectronvolts (GeV), or about the equivalent of 125 protons — so it’s kind of heavy but not incredibly huge.

At first glance, all that sounds fine. Physicists didn’t really have a firm prediction for the mass of the Higgs boson, so it could be whatever it wanted to be; we happened to find the mass within the energy range of the LHC. Break out the bubbly, and let’s start celebrating.

Except that there are some hesitant, kind-of-sort-of half-predictions about the mass of the Higgs boson based on the way it interacts with yet another particle, the top quark. Those calculations predict a number way higher than 125 GeV. It could just be that those predictions are wrong, but then we have to circle back to the math and figure out where things are going haywire. Or the mismatch between broad predictions and the reality of what was found inside the LHC could mean that there’s more to the Higgs boson story.

There very well could be a whole plethora of Higgs bosons out there that are too heavy for us to see with our current generation of particle colliders. (The mass-energy thing goes back to Einstein’s famous E=mc^2 equation, which shows that energy is mass and mass is energy. The higher a particle’s mass, the more energy it has and the more energy it takes to create that hefty thing.)

In fact, some speculative theories that push our knowledge of physics beyond the Standard Model do predict the existence of these heavy Higgs bosons. The exact nature of these additional Higgs characters depends on the theory, of course, ranging anywhere from simply one or two extra-heavy Higgs fields to even composite structures made of multiple different kinds of Higgs bosons stuck together.

Theorists are hard at work trying to find any possible way to test these theories, since most of them are simply inaccessible to current experiments. In a recent paper submitted to the Journal of High Energy Physics, and published online in the preprint journal arXiv, a team of physicists has advanced a proposal to search for the existence of more Higgs bosons, based on the peculiar way the particles might decay into lighter, more easily-recognizable particles, such as electrons, neutrinos and photons. However, these decays are extremely rare, so that while we can in principle find them with the LHC, it will take many more years of searching to collect enough data.

When it comes to the heavy Higgs, we’re just going to have to be patient.

Originally published on Live Science.
By Paul Sutter, Astrophysicist



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1969: Inside Giant Atom Smasher, Physicists See the Impossible: Light Interacting with Light

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In case you didn’t realize it, photons are tiny little bits of light. In fact, they’re the smallest bit of light possible. When you turn on a lamp, gigantic numbers of photons spring from that bulb and slam into your eyes, where they are absorbed by your retina and turned into an electrical signal so that you can see what you are doing.

So, you can imagine just how many photons surround you at any one time. Not just from the lights in your room, but photons also stream in through the window from the sun. Even your own body generates photons, but all the way down in infrared energies, so you need night vision goggles to see them. But they’re still there.

And, of course, all the radio waves and ultraviolet rays and all the other rays constantly bombard you and everything else with an endless stream of photons.

It’s photons everywhere.

These little packets of light aren’t supposed to interact with each other, essentially having no “awareness” that the others even exist. The laws of physics are such that one photon just passes by another with zero interaction. [The 18 Biggest Unsolved Mysteries in Physics]

That’s what physicists thought, at least. But in a new experiment inside the world’s most powerful atom smasher, researchers got a glimpse of the impossible: photons bumping into each other. The catch? These photons were a little off their game, meaning they weren’t acting like themselves and instead had temporarily become “virtual.” By studying these super-rare interactions, physicists hope to reveal some of the fundamental properties of light and possibly even discover new high-energy physics, like grand unified theories and (maybe) supersymmetry.

Usually, it’s a good thing that photons don’t interact with each other or bounce off each other, because that would be a total madhouse with photons never going anywhere in any sort of straight line. So, thankfully, two photons will simply slip by each other as if the other didn’t even exist.

That is, most of the time.

In high-energy experiments, we can (with a lot of elbow grease) get two photons to strike each other, though this happens very rarely. Physicists are interested in this sort of process because it reveals some very deep properties of the nature of light itself and could help to uncover some unexpected physics. [18 Times Quantum Particles Blew Our Minds]

Photons so rarely interact with one another because they connect only with particles that have electric charges. It’s just one of those rules of the universe that we have to live by. But if this is the rule of the universe, then how could we ever get two photons, which have no charge, to connect with each other?

The answer lies in one of the most inscrutable and yet delicious aspects of modern physics, and it goes by the funky name of quantum electrodynamics.

In this picture of the subatomic world, the photon isn’t necessarily a photon. Well, at least, it’s not always a photon. Particles like electrons and photons and all the other -ons continually flip back and forth, changing identities as they travel. It seems confusing at first: How could, say, a beam of light be anything other than a beam of light?

In order to understand this wacky behavior, we need to expand our consciousness a little (to borrow an expression).

In the case of photons, as they travel, every once in a while (and keep in mind that this is extremely, extremely rare), one can change its mind. And instead of being just a photon, it can become a pair of particles, a negatively charged electron and a positively charged positron (the antimatter partner of the electron), that travel together.

Blink and you’ll miss it, because the positron and electron will find each other, and, as happens when matter and antimatter meet, they annihilate, poof. The odd pair will turn back into a photon.

For various reasons that are way too complicated to get into right now, when this happens, these pairs are called virtual particles. Suffice it to say that in almost all cases you never get to interact with the virtual particles (in this case, the positron and electron), and you only ever get to talk to the photon.

But not in every case.

In a series of experiments run by the ATLAS collaboration at the Large Hadron Collider beneath the French-Swiss border and recently submitted to the online preprint journal arXiv, the team spent way too much time slamming lead nuclei into each other at nearly the speed of light. However, they didn’t actually let the lead particles hit each other; instead, the bits just came very, very, very, very close. [Photos: The World’s Largest Atom Smasher (LHC)]

This way, instead of having to deal with a gigantic mess of a collision, including a lot of extra particles, forces and energies, the lead atoms just interacted via the electromagnetic force. In other words, they just exchanged a whole lot of photons.

And every once in a while — extremely, incredibly rarely — one of those photons would briefly turn into a pair composed of a positron and an electron; then, another photon would see one of those positrons or electrons and talk to it. An interaction would occur.

Now, in this interaction, the photon just sort of bumps into either the electron or the positron and goes off on its merry way without any harm. Eventually, that positron or electron finds its mate and returns to being a photon, so the result of two photons hitting each other is just two photons bouncing off each other. But that they were able to talk to each other at all is remarkable.

How remarkable? Well, after trillions upon trillions of collisions, the team detected a grand total of 59 potential intersections. Just 59.

But what do those 59 interactions tell us about the universe? For one, they validate this picture that a photon isn’t always a photon.

And by digging into the very quantum nature of these particles, we could learn some new physics. For example, in some fancy models that push the boundaries of known particle physics, these photon interactions occur at slightly different rates, potentially giving us a way of exploring and testing these models. Right now, we don’t have enough data to tell the differences among any of these models. But now that the technique is established, we might just make some headway.

And you’re going to have to excuse the very obvious closing pun here, but hopefully soon, we can shed some light on the situation.

livescience
By Paul Sutter, Astrophysicist
April 25, 2019 07:14am ET


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1919: Navy Plans to Document UFO Sightings, But Keep Them Confidential

Credit: Shutterstock

Extraterrestrials, take note: The U.S. Navy plans to set up an official reporting and investigative system that will monitor reports from its pilots about unidentified flying objects.

But while this “X-Files”-worthy operation sounds newsy, don’t expect to hear details about it anytime soon. The Navy doesn’t intend to make the data public, citing the privileged and classified information that these reports usually include, according to The Washington Post.

“Military aviation safety organizations always retain reporting of hazards to aviation as privileged information in order to preserve the free and honest prioritization and discussion of safety among aircrew,” Joe Gradisher, a spokesman for the Office of the Deputy Chief of Naval Operations for Information Warfare, told The Washington Post. [7 Things Most Often Mistaken for UFOs]

In fact, beyond the announcement that the Navy is setting up this UFO-reporting procedure, “no release of information to the general public is expected,” Gradisher said.

The upcoming procedure comes in the wake of other government-related UFO news. In late 2017, word came out that the Pentagon had a secret “UFO” office that spent $22 million over five years to study strange and threatening aeronautical events. Although funding for the venture, called the Advanced Aerospace Threat Identification Program (AATIP), ended in 2012, the program didn’t entirely stop, according to those reports.

When news of AATIP became public in 2017, the Defense Department released two declassified videos, which showed pilots talking about a bizarre aircraft that appeared to accelerate quickly, even though it had no recognizable means of propulsion. These aircraft, which looked like blobs on the video, could allegedly drive thousands of feet in an instant.

By creating this new program, the Navy hopes to destigmatize any reporting associated with incidents that involve UFOs, which could, after all, be militarized aircraft from other parts of the world.

“There have been a number of reports of unauthorized and/or unidentified aircraft entering various military-controlled ranges and designated air space in recent years,” the Navy told Politico, which broke the story. “For safety and security concerns, the Navy and the [U.S. Air Force] takes these reports very seriously and investigates each and every report.”

The public may get a whiff of these incidents eventually, although the details may be scarce. For instance, perhaps unclassified parts, broad overviews or statistics about the number of sightings could be released, Luis Elizondo, an intelligence officer who ran AATIP before leaving the Pentagon, told The Washington Post.

“If it remains strictly within classified channels, then the ‘right person’ may not actually get the information,” Elizondo said. “The right person doesn’t necessarily mean a military leader. It can be a lawmaker. It can be a whole host of different individuals.”

The government is making a smart move by announcing its intentions to formally document and analyze these UFOs, said Seth Shostak, a senior astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California.

“It will make everybody happy because it sounds like a move toward transparency,” Shostak told Live Science.

With this announcement, the Navy benefits not only because it will formally investigate these strange sightings, which may well be reconnaissance or enemy aircraft from other nations; the Navy is also winning a nod from the roughly two-thirds of Americans who think that the government isn’t divulging everything it knows about extraterrestrials and UFOs, said Shostak, citing a 2002 study on attitudes about aliens.

That said, the government probably isn’t formalizing this program because it’s looking for E.T.

“The military is interested in this stuff not because they think that Klingons are sailing in the skies, but i think because maybe they think the Chinese or the Russians are sailing through the skies,” Shostak said.

Originally published on Live Science
By Laura Geggel, Associate Editor
May 2, 2019 03:38pm ET

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1909: Mystery Sea Opened Up During the Antarctic Winter. Now, Scientists Know Why.


A polynya in Antarctica’s Weddell Sea.
Credit: Wolfgang Kaehler/LightRocket via Getty Images

A swath of ice-free sea that regularly opens up during the frigid Antarctic winters is created by cyclones.

Sea ice in Antarctica is thickest in the winter, so the appearance of open water is perplexing. These open seas are called polynyas. In 2017, scientists spotted one in the Lazarev Sea, which they called the Maud Rise polynya because it sits over an ocean plateau called Maud Rise.

Now, researchers led by Diana Francis, a New York University Abu Dhabi atmospheric scientist, find that cyclonic winds push ice in opposite directions, causing the pack to open up and expose open sea. [Antarctica: The Ice-Covered Bottom of the World (Photos)]

In mid-September 2017, the Maud Rise polynya was 3,668 square miles (9,500 square kilometers) in size. By mid-October, it had grown to 308,881 square miles (800,000 square km).

The Maud Rise polynya in September 2017.
Credit: NASA Worldview

An analysis of high-resolution satellite imagery explained the rapid growth. Warm, moist air flowing in from the western South Atlantic hit cold air headed northward from the south, setting the stage for violent storms. The resulting cyclones rated 11 on the Beaufort storm scale, meaning they involved wind speeds of up to 72 mph (117 km/h) and waves up to 52 feet (16 meters) high anywhere they encountered open sea.

These swirling winds pushed ice away from the cyclonic centers, Francis and her colleagues wrote April 24 in the journal JGR Atmospheres.

Polynyas aren’t new or necessarily harmful. According to the National Snow and Ice Data Center (NSIDC), they can provide important ocean access for Antarctic animals and habitat for phytoplankton.

However, polynyas may change in a warming future, Francis and her colleagues speculated. Antarctica is expected to experience stronger cyclones as the climate changes, because models show that storms are likely to form more often toward the poles and to be more intense, according to the NSIDC.

If those predictions are correct, Antarctica might see more open water in future winters.

Originally published on Live Science.
By Stephanie Pappas, Live Science Contributor 
April 30, 2019 06:59am ET

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1898: Why Does the Earth Rotate?

Credit: Shutterstock

This story was updated at 9:40 a.m. E.D.T. on Monday, Sept. 10.

Every day, the Earth spins once around its axis, making sunrises and sunsets a daily feature of life on the planet. It has done so since it formed 4.6 billion years ago, and it will continue to do so until the world ends — likely when the sun swells into a red giant star and swallows the planet. But why does it rotate at all?

The Earth formed out of a disk of gas and dust that swirled around the newborn sun. In this spinning disk, bits of dust and rock stuck together to form the Earth, according to Space.com, a sister site of Live Science. As it grew, space rocks continued colliding with the nascent planet, exerting forces that sent it spinning, explained Smadar Naoz, an astrophysicist at the University of California, Los Angeles. Because all the debris in the early solar system was rotating around the sun in roughly the same direction, the collisions also spun the Earth — and most everything else in the solar system — in that direction. [Photo Timeline How the Earth Formed]

But why was the solar system spinning in the first place? The sun, and the solar system, formed when a cloud of dust and gas collapsed due to its own weight. Most of the gas condensed to become the sun, while the remaining material went into the surrounding, planet-forming disk. Before it collapsed, the gas molecules and dust particles were moving all over the place, but at a certain point, some gas and dust happened to shift a bit more in one particular direction, setting its spin in motion. When the gas cloud then collapsed, the cloud’s rotation sped up — just as figure skaters spin faster when they tuck their arms and legs in.

Because there isn’t much in space to slow things down, once something starts rotating, it usually keeps going. The rotating baby solar system in this case had lots of what’s called angular momentum, a quantity that describes the object’s tendency to keep spinning. As a result, all the planets likely spun in the same direction when the solar system formed.

Today, however, some planets have put their own spin on their motion. Venus rotates in the opposite direction as Earth, and Uranus’ spin axis is inclined 90 degrees. Scientists aren’t sure how these planets got this way, but they have some ideas. For Venus, maybe a collision caused its rotation to flip. Or maybe it began rotating just like the other planets. Over time, the sun’s gravitational tug on Venus’ thick clouds, combined with friction between the planet’s core and mantle, caused the spin to flip. A 2001 study published in Nature suggested that gravitational interactions with the sun and other factors might have caused Venus’ spin to slow down and reverse.

In the case of Uranus, scientists have suggested that collisions — one huge crash with a big rock or maybe a one-two punchwith two different objects — knocked it off kilter, Scientific American reported.

Despite these kinds of disturbances, everything in space rotates in one direction or another. “Rotating is a fundamental behavior of objects in the universe,” Naoz said.

Asteroids rotate. Stars rotate. Galaxies rotate (it takes 230 million years for the solar system to complete one circuit around the Milky Way, according to NASA). Some of the fastest things in the universe are dense, whirling objects called pulsars, which are the corpses of massive stars. Some pulsars, which have a diameter about the size of a city, can spin hundreds of times per second. The fastest one, announced in Science in 2006 and dubbed Terzan 5ad, rotates 716 times per second.

Black holes can be even faster. One, called GRS 1915+105, may be spinning anywhere between 920 and 1,150 times per second, a 2006 study in the Astrophysical Journal found.

But things slow down, too. When the sun formed, it spun once around its axis every four days, Naoz said. But today, it takes about 25 days for the sun to spin once, she said. Its magnetic field interacts with the solar wind to slow its rotation, Naoz said.

Even Earth’s rotation decelerates. Gravity from the moon pulls on Earth in a way that ever so slightly slows it down. A 2016 analysis in the journal Proceedings of the Royal Society A of ancient eclipses showed that Earth’s rotation slowed by 1.78 milliseconds over a century.

So, while the sun will rise tomorrow, it just may be a tad late.

Originally published on Live Science.

Editor’s Note: This story was updated to remove an incorrect calculation. Earth’s rotation did not slow down by 6 hours over the last 2,740 years.

By Marcus Woo, Live Science Contributor
August 26, 2018 07:02am ET

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1892: The Universe Is Moving Too Fast and Nobody Knows Why

A cepheid in the Milky Way, RS Puppis, is seen through the Hubble Space Telescope.
Credit: Hubble Space Telescope

The universe is moving too fast and nobody knows why.

Back in the early years of the universe, right after the Big Bang, everything blasted away from everything else. We can still see the light from that blast, by observing very faraway parts of the universe where light takes billions of years to reach our telescopes. And we can measure how fast things were moving in those faraway spotsBased on that speed, we can calculate how fast the universe should be expanding today.

But when astronomers have tried to directly measure how fast the universe is expanding today — a more difficult task, because everything is farther apart now — things seem to be moving faster than those calculations would predict. And a new paper, based on highly detailed observations taken using the Hubble Space Telescope, appears to confirm that finding: Everything is moving about 9 percent too fast.

And still, nobody knows why. [Does the Universe Have an Edge?]

Earlier observations of that increased speed still had a 1 in 3,000 chance that astronomers were wrong, which is considered pretty high for an astrophysics result. This new paper improves astronomers’ confidence, with just a 1 in 100,000 chance of being based on an observational error. It’s due for publication in the April 25 issue of The Astrophysical Journal Letters, and is available on the preprint server arXiv.

“This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This is not what we expected,” lead author Adam Riess, a Johns Hopkins University Nobel laureate and astrophysicist, said in a statement.

The researchers relied on the same tool that astronomer Edwin Hubble used to show that the universe was expanding back in 1929: a class of pulsing stars called cepheids.

Cepheids, the astronomer Henrietta S. Leavitt had shown in a 1908 paper in the journal Annals of the Harvard College Observatory, pulse in direct proportion to their brightness. That means that astronomers can figure out exactly how bright a cepheid should be based on how fast it’s pulsing. Then, by seeing how dim it looks from Earth, they can tell how much light it’s lost along the way, and thus how far away it is.

To measure the rate of the universe’s expansion, astronomers check the distance to cepheids in nearby and faraway galaxies. But that’s usually a slow task to do precisely, with the Hubble able to precisely measure just one distant cepheid at a time. The researchers developed a method to allow the space telescope to “drift” as it images the stars, imaging more than one at the same time and drastically increasing the precision of their overall distance measurement.

What they found directly contradicts predictions made based on observations from the European Space Agency’s Planck satellite, which measured the speed of the universe 380,000 years after the Big Bang.

So what does it mean that the universe is almost certainly moving too fast?

“This is not just two experiments disagreeing,” Riess said. “We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”

Riess doesn’t know what the missing thing is, but for now, he plans to keep refining his measurements.

Originally published on Live Science.
By Rafi Letzter, Staff Writer 
April 26, 2019 08:18am ET

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One of Stephen Hawking’s Most Famous Theories About Black Holes Just Suffered a Huge Blow


An image of the Andromeda Galaxy captured with the Hyper-Suprime-Cam. A recent snapshot of Andromeda found only one signal that could have come from a medium-sized primordial black hole, or one that formed soon after the Big Bang.
Credit: Copyright HSC-SSP and NAOJ

One of Stephen Hawking’s most famous theories about dark matter — that this mysterious and invisible substance is made up of primordial black holes — recently suffered a huge blow. That conclusion comes from a massive telescope that captured an image of an entire galaxy in one shot.

The findings don’t completely rule out Stephen Hawking’s famous notion. But they suggest that primordial black holes would have to be truly tiny to explain dark matter.

Dark matter is the name given by physicists to explain a particularly mysterious phenomenon: Everything in the universe moves, orbits and rotates as if there were more mass than we can detect. Explanations for dark matter range from ghostly particles called neutrinos to unknown particles, to new laws of physics. In the 1970s, Stephen Hawking and his colleagues theorized that the Big Bang may have created a large number of relatively small black holes — each about the size of a proton. These tiny, ancient black holes would be difficult to see, yet would exert a large gravitational pull on other objects — the two known properties of dark matter. [The 11 Biggest Unanswered Questions About Dark Matter]

Until now, this theory could only be tested for primordial black holes heavier than the moon. But as technology has improved, scientists have been able to take sharper and sharper pictures of outer space. The Hyper Suprime-Cam (HSC) digital camera on the Subaru telescope in Hawaii is an advanced piece of imaging technology that can take a picture of the entire Andromeda galaxy (the nearest galaxy to our own) in one shot. Masahiro Takada and his team at the Kavli Institute for the Physics and Mathematics of the Universe in Japan used this camera to search for primordial black holes;; their results were published earlier this month in the journal Nature Astronomy.

Black holes emit no light, though,supermassive black holes, like the one at the heart of galaxy Messier 87, are fringed by bright disks of hot matter. Primordial black holes, however, are billions of times smaller and have no visible, glowing matter surrounding them. Instead, searching for small black holes means looking for places where their powerful gravitational fields bend light — a phenomenon called microlensing.

Telescopes find microlensing black holes by taking many different pictures of a star over time. A black hole passing in front of that star will distort its light, making it flash; the smaller the black hole, the quicker the flash. “If a microlensing object has, let’s say one solar mass,” Takada told Live Science, referring to the mass of the sun, “the timescale [of the microlensing ‘flash’] is like a few months or a year.” But the primordial black holes they were looking for had only a small fraction of that mass, approximately the mass of the moon. That means their flashes would be much shorter. The HSC is “unique,” Takada said, in that it let them take images of all the stars in the Andromeda galaxy at once, at breathtakingly fast (to astronomers) exposure intervals — each interval was just 2 minutes long.

Takada and his team took about 200 pictures of the Andromeda galaxy over 7 hours on a clear night. They found just one potential microlensing event. If primordial black holes made up a significant fraction of dark matter, Takada said, they should have seen approximately 1,000 microlensing signals.

“Microlensing is the gold standard for detecting black holes or ruling them out,” said Simeon Bird, a black- hole physicist at the University of California — Riverside, who was not involved in the work. “This work rules out primordial black holes as dark matter in a range of masses where the previous constraints were not as strong nor as robust as this new one. It’s a very nice result.”

Was this the final nail in the coffin? Is Hawking’s theory really dead? Not so, according to Bird and Takada, who say that primordial black holes of a certain range of masses still haven’t been totally eliminated as candidates. [Stephen Hawking’s Most Far-Out Ideas About Black Holes]

“There are still some masses where the constraints are weak, around 20-30 solar masses,” Bird told Live Science. “Those could still be 1% to 10% of dark matter … and there’s still a window at lower masses, like the mass of a very small asteroid.”

“Our physicists are very excited because there is still a window,” Takada said. The data can’t rule out those teensy tiny black holes because the flashes from those black holes would be much too short, “so we need to think of another method to do it.”

There was, however, one “flash” detected in their survey. While it was a single, preliminary result, it could end up being incredibly important: the very first detection of a primordial black hole, which would be a groundbreaking validation of some of Hawking’s work.

“Only one observation is not that convincing,” Takada said. “We need more observations to confirm. If it was really [a primordial black hole], we should continue to find the same thing” as they continue to use the HSC to look for more microlensing.

Livescience
By Meredith Fore, Live Science Contributor
April 25, 2019 07:15am ET

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