Quantum black hole study opens bridge to another universe

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Quantum black hole study opens bridge to another universe

Physicists have long thought that the singularities associated with gravity (like the inside of a black hole) should vanish in a quantum theory of gravity. It now appears that this may indeed be the case. Researchers in Uruguay and Louisiana have just published a description of a quantum black hole using loop quantum gravity in which the predictions of physics-ending singularities vanish, and are replaced by bridges to another universe.

Singularities, such as the infinitely strong crushing forces at the center of a black hole, in a physical theory are bad. What they tell you is that your description of the universe fails miserably to explain what happens as you approach the singularity. Tricks can sometimes resolve what appears to be singular behavior, but essential singularities are signs of a failure of the physical description itself.

Satellite orbiting Earth is guided by the spacetime curvature generated by the Earth's mass (Photo: NASA)

Satellite orbiting Earth is guided by the spacetime curvature generated by the Earth’s mass (Photo: NASA)

General relativity has been summed up by the late John Wheeler’s phrase: “Spacetime tells matter how to move, matter tells spacetime how to curve.” Relativity is riddled with essential singularities, because gravity is both attractive and nonlinear – curvature in the presence of mass tends to lead to more curvature, eventually leading to trouble.

The result is rather similar to a PA system on the verge of producing a feedback whistle. If you whisper into the microphone (small gravitational fields) the positive feedback isn’t enough to send the PA into oscillation, but talking at a normal volume (larger gravitational fields) produces that horrible howl. Whispering is the comparable to the familiar actions of gravity that keep the planets and stars in their courses. The howl is the process that eventually leads to a singularity as the end result of gravitational collapse.

Let’s follow this analogy a bit further. On a PA system, the volume of the feedback is limited by the power capacity of the amplifier, so it can’t reach truly destructive levels (other than to our eardrums.) However, gravity as described by general relativity doesn’t have such a limit. Since gravity is always attractive, and eventually becomes stronger than all the (known) forces that normally give volume to matter, there is nothing to keep gravitational collapse from proceeding until the curvature of the spacetime tends toward infinity – i.e. a singularity.

Remember that this is the prediction of the classical theory of gravity, general relativity. Classical physical theories contain no fundamental limitation on mass-energy density or on the size of spacetime curvature. While this may be (and probably is) incorrect, we rarely run into a problem caused by this error, so have largely ignored the problem for centuries.

Then along came gravitational collapse and black holes. First proposed by geologist John Mitchell in 1783, a black hole is a region of spacetime from which gravity prevents anything, even light, from escaping.

Black holes are formed when large stars run out of fuel. When a star’s core cools, the star shrinks. As the star’s layers fall inward, they are compressed by the unbalanced force of gravity, and heat up until a new balance is established. This can only go on so long, as the star (on average) gets smaller at each step of the process of collapse. Eventually the heating driven by this gravitational collapse becomes too small to hold the star up.

At this point, the size of the star depends mostly on its mass, as the force of gravity is only balanced by the ability of the star’s material to resist pressure. If a star is heavy enough (8-10 times the mass of our Sun), there is no known source of material pressure which is large enough to resist gravity. In that case, the star collapses without end, and forms a black hole, from which even light cannot escape.

Black holes really began to be understood in the late 1950s, when David Finkelstein, then a professor at the Stevens Institute of Technology, found that the odd behavior at the Schwartzchild radius was actually “… a perfect unidirectional membrane: causal influences can cross it but only in one direction.” In other words, what falls into a black hole stays there.

In the spacetime diagram below, known as a causal diagram, the exterior and interior of a classical black hole are sketched. The yellow lines outside and the blue lines inside the black hole show the paths along which light travels. All particles have to follow slower paths that are sandwiched between these “light cones.” The red line at the center of the black hole is a curvature singularity.

Nothing can emerge from a classical black hole, and at the center lies a curvature singularity...

Nothing can emerge from a classical black hole, and at the center lies a curvature singularity (Image: Alexandre Van de Sande as adapted by B. Dodson)

As you approach the black hole, gravity causes light and particles to curve toward the black hole, which is seen as tipping of the light cones (middle). At points inside the black hole (top), the light cone is tilted so that all light, and hence all particles, can only travel deeper into the black hole. Past the event horizon of a classical black hole, there is no escape.

At the center of a black hole, all matter and light are forced to move inward at ever increasing speeds. This forces whatever enters a black hole into a single point of space right at the center. This point exhibits infinite curvature, making it a curvature singularity. At that point, no known combination of conventional quantum mechanics and general relativity can tell us what happens to the matter and light – the theories break down.

Shortly after Finkelstein’s work, Roger Penrose, Steven Hawking, and Robert Geroch showed that gravitational collapse is essentially always followed by formation of essential singularities, disappointing those who hoped that singularities only formed in highly symmetric geometries. As the prediction of a singularity tells you that your physics is wrong, this emphasized the need for a better theory of gravity.

Schrodinger's Cat points out the strange paradoxes of quantum theory (Image: Doug Hatfield)

Schrodinger’s Cat points out the strange paradoxes of quantum theory (Image: Doug Hatfield)

Well, the other fairly comprehensive and insanely accurate description of what happens in the universe is quantum theory. Moreover, one might guess that quantum uncertanity and fuzziness might keep curvature singularities from occurring, so it seems reasonable to try to solve the limitations of general relativity by developing a quantum theory of gravity.

Easier said than done. Hawking radiation predicts that a black body radiation is emitted by black holes as a result of quantum effects taking place very near the event horizon, which immediately leads to a serious conflict between general relativity and quantum mechanics.

Hawking radiation results from the trapping of one member of a virtual particle-antiparticle pair inside the...

Hawking radiation results from the trapping of one member of a virtual particle-antiparticle pair inside the event horizon of a black hole (Image: B. Dodson)

Roughly speaking, what happens is that a vacuum fluctuation near the event horizon produces a virtual particle-antiparticle pair. One of the pair falls into the black hole, and the other becomes real and escapes from the black hole, as the first cannot reemerge through the black hole to recombine with the first particle.

Here’s the problem. When matter and light fall into a black hole, it appears that whateverinformation that matter and light may have carried along with them vanishes in the process. Indeed, the sum of all Hawking radiation emitted during the life of a black hole informs you of the mass, spin, and electric charge of what fell into the hole, but nothing else.

Unfortunately, one of the fundamental tenets of quantum mechanics is that information isnever destroyed. It appears that the first “successful” result combining general relativity and quantum effects leads to a fundamental conflict. This difficulty is known as the black hole information paradox.

The model used to predict Hawking radiation is pretty simplistic, consisting of ordinary quantum field theory modified to work on a curved background space. The shape of this background space is fixed, so cannot change its shape in response to the movement of light and particles. This is an example of a semiclassical model. More sophisticated semiclassical models would allow small changes in spacetime geometry, but still essentially function in a fixed background geometry.

As more and more semiclassical research has been carried out in an attempt to get a handle on what a quantum theory of gravity might look like, more and more apparent paradoxes have appeared. We won’t describe these, but they become increasingly unpleasant. It appears that believing the fundamental assumptions of general relativity leads almost inevitably to fundamental problems in quantum mechanics, and vice versa.

But we don’t want to wait for a full quantum theory of gravity to investigate what happens at the center of a black hole. There isn’t one in sight, although some version of string theory may be the best bet on the horizon. Instead, it might be reasonable to use a model, called loop quantum gravity, which treats spacetime as a fine structure woven of Planck-sized loops. In this description of physics, there is simply no concept of lengths smaller than the Planck length. While something of the sort is likely to be true in a full quantum theory of gravity, it is expected that this structure should emerge from the theory, rather than be made a basic assumption of the theory. Even though this model may not be a viable candidate for a full theory of quantum gravity, it might give some insight into what happens at the central singularity of a quantum black hole.

This brings us to the new work of Rodolfo Gambini and Jorge Pullin, recently published inPhysical Review Letters. Gambini and Pullin have developed and solved the first well-behaved model of a quantum black hole, in which the central curvature singularity vanishes, and is replaced by a bridge that appears to lead into another universe. Other details of their treatment offer promise for reconciling other apparent paradoxes associated with blending general relativity and quantum mechanics. They are currently trying to extend their work to study of an evaporating quantum black hole.

Despite the limitations of this result, it is encouraging to know that the best model of a quantum black hole currently available appears consistent with what generations of physicists had hoped would be the case; that quantum effects prevent singularities.

Source: Loop quantization of the Schwarzschild black hole via ArXiv [PDF]


NASA peers into huge hole in the sun

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NASA peers into huge hole in the sun


Although we're not sure what causes them, coronal holes can have a dramatic impact on our ...

Although we’re not sure what causes them, coronal holes can have a dramatic impact on our magnetosphere (Credit: NASA)

While you might think the sun has pretty much just one weather pattern – blistering and violent with a chance of radiation poisoning – it can actually be quite varied. One of the lesser-known weather phenomena on the sun’s surface are coronal holes, like the massive one that was recently captured by NASA’s Solar Dynamics Observatory (SDO) and featured this week in a short video from the space agency.

“Coronal holes are low-density regions of the sun’s atmosphere, known as the corona,” says NASA. “Because they contain little solar material, they have lower temperatures and thus appear much darker than their surroundings. Coronal holes are visible in certain types of extreme ultraviolet light, which is typically invisible to our eyes, but is colorized here in purple for easy viewing.” The holes are also visible in x-ray wavelengths.

Although it’s not clear what causes the coronal holes to appear on the sun, it is known that the patches are the source of a super-fast solar wind that can be up to three times more rapid than solar winds from other parts of the sun. The solar wind is a stream of plasma containing charged particles that shoots off the sun. When such a stream contacts the Earth’s magnetosphere, it can cause storms that lead to pleasant results like the aurora borealis, or more destructive results like disrupting power supplies and communications.

During solar minimums – approximately 11-year-long periods during which the sun is relatively quiet – coronal holes appear near the solar poles, as this one does. That makes sense because this video was created from images taken by the SDO in early May, and we are currently on the downslope from a solar maximum that peaked in 2013, and was itself relatively weak.

The SDO was launched in 2010 and consists of a series of instruments specifically designed to observe the sun. It has been returning some pretty astounding images since being put into orbit around Earth.

This video showing the coronal hole adds to the impressive eye-candy the SDO has been sending back of our nearest and dearest star for much of the decade.

Source: NASA

Superbugs could kill 10 million people a year by 2050, report warns

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Superbugs could kill 10 million people a year by 2050, report warns


A review on antimicrobial resistance warns that superbugs could kill 10 million people a year by ...

A review on antimicrobial resistance warns that superbugs could kill 10 million people a year by 2050, but outlines ways we can prevent or lessen the threat.

In July 2014, the UK government commissioned the Review on Antimicrobial Resistance (AMR) to address the ever-growing concern that superbugs, resistant to current antibiotics, could eventually evolve to the point that our drugs simply don’t work. The report’s findings were released this week, including a comprehensive action plan to prevent the world being “cast back into the dark ages of medicine.”

Economist Jim O’Neill, the Chairman of the Review on AMR, predicts that superbugs, if left unchecked, could kill up to 10 million people per year by 2050, equivalent to one person every three seconds. The report outlined 10 areas where the world needs to take action to prevent or lessen the threat, and suggested strategies to do so.

The most immediate suggestion involves setting up a global public awareness campaign on the problem as soon as possible, coordinated between industry, government and non-government organizations, with a potential formal launch at the UN General Assembly in September.

Over-prescription is a major contributing factor to the issue, and the report recommends that the world reduces the use of antibiotics, and tighten restrictions on when they should be prescribed. This should slow the evolution of bacteria and viruses, and make our current drugs effective for longer.

As existing antibiotics inevitably become ineffective, however, new ones need to be able to take their place. And although we’ve seen some promising developments, the review calls for additional funding and rewards from bodies like the G20 to incentivize researchers to develop new drugs, as well as encourage more people to enter the field professionally.

The report also pointed to overuse of antibiotics in agriculture, where they are given to animals, often unnecessarily, when they could be vital to humans. Cutting back on these, as well as our own use, could be instrumental in maintaining our current stocks until replacements can be developed.

Of course, these methods and incentives won’t come cheap, and the report outlines how these guidelines could be paid for. A “very small percentage of G20 countries’ existing healthcare” could go towards funding this goal, and implementing a tax on antibiotic use and pharmaceutical companies who don’t invest in AMR research could help raise capital as well as discourage wasteful prescription.

According to the paper, the cost of action is estimated to be US$40 billion over 10 years, but it makes clear that the cost of inaction will be far greater: up to a staggering $100 trillion, not to mention the widespread loss of life.

With international cooperation critical to any approach, the report calls on the World Health Assembly, G7, G20, and the UN to deliver the policy proposals recommended in the report and turn them into action.

Source: AMR Review

Wound-plugging XStat syringe saves its first life on the battlefield

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Wound-plugging XStat syringe saves its first life on the battlefield


The XStat syringe was first approved for battlefield use in 2014 and has now been used ...

The XStat syringe was first approved for battlefield use in 2014 and has now been used for the first time.

With the capacity to stem severe bleeding within around 20 seconds, the XStat sponge-filled syringe could be a real game-changer when it comes to medical care. It has just proved its worth in the most testing of environments, with battlefield surgeons successfully using the device to plug a soldier’s gunshot wound for the first time.

The syringe, which was first approved for battlefield use in 2014, works by filling a wound with small cellulose sponges. These are made from wood pulp and covered in chitosan, an antimicrobial compound found in crustacean shells. This not only fights off bacteria, but also causes blood clotting that combines with the expanding sponges to apply pressure and quickly stop arterial bleeding.

When a coalition forces soldier received a gunshot wound to the left thigh, opening up the femoral artery and vein to leave a gaping cavity, doctors were unable to stem the residual bleeding even after around seven hours of surgery.

The team then called on the XStat syringe to fill the wound, applying a single syringe to the cavity which almost immediately stopped the flow of blood. The soldier then became stable and was moved to a definitive care facility.

“The first-in-human experience with XStat is the culmination of tremendous effort on the part of both RevMedx and our military collaborators,” says Andrew Barofsky, president and CEO of RevMedx. “We are pleased to see XStat play a critical role in saving a patient’s life and hope to see significant advancement toward further adoption of XStat as a standard of care for severe hemorrhage in pre-hospital settings.”

The civilian version of the syringe, called XStat 30, was cleared by the FDA for use by the general population in December last year. Because the dressing can be used for up to four hours and contains x-ray detectable markers for surgical removal later on, it is hoped first responders can use it to limit civilian deaths that result from haemorrhaging before they reach the hospital.

Source: RevMedX

US Army and Marine Corps PowerWalk into wearable battery trials

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US Army and Marine Corps PowerWalk into wearable battery trials


Bionic Power is teaming up with the US Army and Marine Corps to conduct field trials ...

Bionic Power is teaming up with the US Army and Marine Corps to conduct field trials of PowerWalk.

Development of piezoelectric and triboelectric generators that harvest the kinetic energy generated by movement has been gaining momentum over the past few years, and now the US Army and Marine Corps are taking the technology into the field. Vancouver-based Bionic Power will soon supply troops with its PowerWalk Kinetic Energy Harvester, a lightweight device worn around the knee that recharges batteries while soldiers walk.

Two PowerWalk devices can produce an average of 10 to 12 watts

Two PowerWalk devices can produce an average of 10 to 12 watts

The PowerWalk features a gearbox that mechanically converts the knee’s rotation speed into a higher speed that is more efficient for the onboard power generator to then convert to electrical power. The result is 10 to 12 watts of electricity, which is itself then converted to charge Li-ion or NiMH batteries.

Wearing a PowerWalk on each leg, users can apparently generate enough electricity to charge four smartphones after an hour of walking at a reasonable pace. The PowerWalk is also able to analyze the wearer’s gait to determine the most efficient time to generate power, and Bionic Power claims a secondary benefit of reducing muscle fatigue during downhill walking, lowering the risk of knee injury.

The PowerWalk kinetic energy harvester wraps around the knee and recharges batteries while soldiers walk

The PowerWalk kinetic energy harvester wraps around the knee and recharges batteries while soldiers walk

The applications for the military are clear. Electricity is vital in the field, with communications, navigation and optics devices all requiring power, which usually involves carrying heavy battery packs.

“A soldier typically carries 16 to 20 lbs (7 to 9 kg) in batteries on a 72-hour mission,” says Noel Soto, US Army Systems Engineer. “If a soldier can generate power with wearable energy-harvesting devices, it means we can not only reduce the weight on his or her back, we also minimize the unit’s reliance on field resupply, making it possible for us to extend the duration and effectiveness of a mission.”

The US Army and US Marine Corps will begin field trials of the PowerWalk in 2017

The US Army and US Marine Corps will begin field trials of the PowerWalk in 2017

The contract between Bionic Power and the US Army and Marine Corps will see PowerWalk units tested in the field in early to mid-2017. Beyond that, Bionic Power hopes to bring the device to other professional and general consumer markets.

The PowerWalk kinetic energy harvester wraps around the knee and recharges batteries while soldiers walk

The PowerWalk kinetic energy harvester wraps around the knee and recharges batteries while soldiers walk

Two PowerWalk devices can produce an average of 10 to 12 watts

Two PowerWalk devices can produce an average of 10 to 12 watts

The PowerWalk device is designed to lessen the need for soldiers to carry bulky batteries

The PowerWalk device is designed to lessen the need for soldiers to carry bulky batteries

Source: Bionic Power

This Is the Best Look at Pluto’s Surface We’re Going to Get

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 This Is the Best Look at Pluto’s Surface We’re Going to Get

Friday 1:40pm

Image: NASA/New Horizons

New Horizons may be millions of miles beyond Pluto in the Kuiper Belt right now, but that hasn’t stopped the spacecraft from continuing to beam back glorious imagery of its encounter with our solar system’s weirdest little ice world. A new NASA video reveals the most detailed images of Pluto’s surface yet—and they’re spellbinding.

The video below stitches together all of the highest-resolution images captured by New Horizons as it zipped past Pluto on July 14th, 2015. From a distance of 9,850 miles (15,850 kilometers), the spacecraft’s Long Range Reconnaissance Imager achieved a resolution of 260 feet (80 meters) per pixel across a 55 mile-wide strip of the dwarf planet’s encounter hemisphere. From cratered uplands to craggy badlands to blocky plains of nitrogen ice, Pluto’s rugged and diverse surface pops to life as if you’re cruising overhead in a helicopter.

Unless somebody funds another trip to Pluto, these are the best images of the three billion mile-distant world we’re going to see in our lifetimes. But the story is far from over. As scientists continue to study the wealth of data collected by New Horizons, we can expect to reveal more of Pluto’s incredible secrets for years to come.


Maddie is a staff writer at Gizmodo

Watch This Cheetah Run With a GoPro On Its Back

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 Watch This Cheetah Run With a GoPro On Its Back

Sunday 1:00pm

This cat doesn’t care.

Can you imagine riding a cheetah? Besides the fact that it would probably hate you being there, it would also be pretty incredible. Just watch this video simulating what that would be like.

Cincinnati Zoo & Botanical Garden officials outfitted one of their cheetahs, Savannah, with a GoPro camera to capture what a cheetah in full run looks like. Zoo officials said putting the harness on Savannah was easier than you would expect, since all the cheetahs are hand-raised from a young age.

“We put it on Savannah and she could really care less,” said Alicia Sampson of the cat ambassador program at the zoo.

The video shows Savannah running at full speed and in slow motion. The unedited footage is erratic and incredibly shaky, but the slowed-down video shows how the cheetah’s head stays generally still while running, even if the rest of the body is jerking around.

[Cincinnati Zoo & Botanical Garden]

Weekend editor for Gizmodo. Mostly “Hamilton” trash.