Daily Archives: July 14, 2017

Earths magnetic field does way more than guide our compasses and cause occasional worry. Its part of the reason theres life at all on this planetit protects us from harmful solar radiation that might otherwise blow our ozone layer away.

But theres still a lot about the magnetic field scientists dont understand. Most importantly, theyre having trouble figuring out why its so strong. One team decided to take a closer look at the role of the individual elements inside the planet that are thought to influence the field. Turns out, the way nickel behaves at the smallest scales might help explain the magnetic fields strength, to the point that some existing models would need to be rethought. And understanding the Earths magnetic field has implications for everything that relies on it, including activities that require drilling underground.

This is a new idea put into the geophysics research line that nickel has been neglected for the explanation of the geodynamo, the mechanism for creating the magnetic field, study author Giorgio Sangiovanni from the Institute for Theoretical Physics and Astrophysics at the University of Wrzburg in Germany told Gizmodo.

At its most basic level, the Earth probably gets its magnetic field from temperature gradients in the outer core causing metal to convectthis is more or less the way water moves around in a pot of boiling water. Metals can conduct electricity. So, moving metals combined with Earths rotation could create tubes of electric current that point to the poles. Loops of electric current generate magnetic fields through them, so the entire Earth ends up looking like a magnet where the poles align with the tops and bottoms of the tubes.

The problem, which people have been talking about for a while now, is that theres another way for heat to transfer between elements around the core, conduction, that doesnt require metals to physically move. In that case, the energy just gets passed between the atoms as they bump into one another, like how heat travels down the handle of the pot of water youre boiling. But if the outer core loses too much heat through conduction, then theres not enough energy to drive the convection creating the magnetic field. Scientists think that might be the case, and are looking for a source of extra energy that could generate the magnetic field they observe.

Sangiovanni and his colleagues decided to make calculations about the metals in the inner core, to see if they could find some of the missing energy. But unlike the outer core, which is mostly iron, the inner core is 20 percent nickel. The team decided to examine how nickel and irons specific quantum mechanical properties in the Earths solid core impact the magnetic field.

These properties arent fundamental enough to require you to bend over backward imagining Schrdingers cat. They describe the structure of nickel and iron atoms at high temperatures, how electrons interact in collections of these atoms, and how these elements behaviors change at high pressures. It turns out that nickels shape in a solid slows its electrons down. The electrons also interact and scatter off of each other, preventing nickel from being a good conductor of heat, according to the paper published yesterday in Nature Communications. Iron, meanwhile, has a high conductivity at the temperatures and pressures found in the inner core.

In short, the researchers think nickel could reduce the overall conductivity of the core, causing it to retain extra energy that drives convection. And this new insight might have a large enough effect that models of the Earths magnetic field need some reconsidering.

But the researchers findings cant be taken as fact yetthey still need to calculate other properties relating to how nickel conducts heat. But it is promising, said Sangiovanni. Well see after we calculate other important observables, like the thermal and electrical conductivity.

Sangiovanni said that others he spoke to were surprisedmany folks are looking at how lighter elements like silicon influence the physics of Earths core. I would say that people for a long time have discussed the possible presence of nickel in the Earths core, Dario Alf, physics professor at University College, London told Gizmodo, but no one has really discussed it in the way Giorgios paper points out, the effect of nickel on the conductivity of the core.

All that being said, just take solace in the fact that if you dont think you understand the Earths magnetic field, scientists arent completely sure how it works, either.

[Nature Communications]

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Quantum Mechanics Could Shake Up Our Understanding of Earth's ... - Gizmodo

Of the five electric guitars owned by experimental quantum physicist David Reilly, he likes this one the best. Themustard-yellow Fender Telecaster has two pickups, a maple fretboard and country-rock twang. When he's not in the laboratory pondering the mysteries of life, the universe and everything, he likes to lay down tracks on his axe at home, alone. "It's a fantastic way of switching off."

Electric guitar and quantum science are surprisingly similar, he says. To start with, neither pursuit presents an inherentlystable career path. "There are many scientists I know who drive taxis because it's not easy to get a job, like musicians," he says.

Professor Reilly directs the quantum nanoscience laboratory at the University of Sydney and spends timecogitating"spooky" questions, such as: "What does the world look like when I am not observing it?" and "What is the '80s sound?" He's intoJohn Mayer and quantum entanglement. Steely Dan and cryogenic electronics.

Music and quantum physics are quite alikemathematically, he says. "The physics of sound and the construction of tonal systems, such as the way in which a guitar is laid out, captures a lot of the essence of what quantum physics is," he says. "Quantum physics tells us the world is made up of vibrations or waves, just like the waves when you pluck a guitar string."

The rockstar scientist in blue jeans and brown suede shoes who is left-handed but usesregular right-handedguitars will discuss such parallels while playing on stage at the City Recital Hall on August 14, as part of the This Sounds Like Sciencefree lunchtime series.

"There's an enormous amount of electronics and instrumentation and experimental physics wrapped up in music," he says. "It's total nerd heaven."

Professor Reilly started playing guitar at the age of nine and practised every day until his late teens, when he had to choose between the lotof a musician or a scientist. Do you ever wish you were a professional rock guitarist, I ask. "At certain times I flirt with that idea," he says.

But quantumphysics and guitar riffs can feed off each other, he adds. "Science is very much like music, it's about thinking outside the box. Somehow, tapping other parts of your brain musically opens up different thought processes.

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"A lot of people talk about having ideas in the shower. I would say that playing guitar gives me scientific ideas."

He has played in various bands over the years, at wedding receptionsand in pubs. The 1238-seat City Recital Hall, in Angel Place, will be his largest gigby far. He has something special planned for the show. "My hope is that I can tune the configuration of the guitar strings to match that of the hydrogen atom," he says.

"Can you tune your guitar to hydrogen or helium or lithium? I am not sure how good that is going to sound."

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Rockstar scientist David Reilly takes the axe to quantum physics - The Sydney Morning Herald

Scientists have successfully teleported something into space for the first time ever.

The experiment saw Chinese scientists send a photon up away from Earth, further than ever before.

Teleportation of this kind uses the bizarre effects of quantum entanglement, rather than physically hurlingthe object itself over distances. Instead it transfers the information about a photon to another point in space creating a faithful replication of the object.

It marks the first ever time that effect has been tested over long distances. The success could bring with it a whole range of uses including a quantum internet that connects different parts of the world atseemingly impossible speed.

Until now, experiments had been restricted to short distances because of problems with the wires or signals that would carry the information.

But the new test saw scientists teleport up to a satellite. That is likely to be the way that such teleportation will work in practice sending objects up to space and then back down again to wherever they are needed, since it means there arerelatively clear paths between all of the different points.

Teleportation has become fairly common on the Earth, where scientists can instantly shoot information about photonsover small distances. But the new study moves towards making that effect more practically useful.

"This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet," the scientists write in their paper, which has been published online.

The satellite itself named Micius after an ancient Chinese philosopher was sent up from the Gobidesert last year, by the team in charge of the project. It dropped off the rocket that carried it to space and it has been in orbit above the Earth ever since.

Micius itself canreceive photons and is sensitive enough to catch and spot them;the team on the ground had kit that could send those photons up into space. Together, that kit could allow the scientists to test how the team on Earth were able to interact with photons floating way above our planet.

It works by harnessing the strange effects of quantum entanglement, which Einstein described as "spooky action at a distance". The effect describes the behaviour where particles seem to act on each other instantly and in bizarre ways.

That entanglement is notconstrained by distances, meaning that two particles can interact despite being a very long way apart. Scientists hope to be able to use that effect for their own ends,includingsending messages that are received far more quickly than using traditional means, for example.

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Scientists teleport particle into space in major breakthrough for quantum physics - The Independent

One of the most well-accepted physical theories makes no logical sense. Quantum mechanics, the theory that governs the smallest possible spaces, forces our human brains to accept some really wacky, uncomfortable realities. Maybe we live in a world where certain observations can force our universe to branch into multiple ones. Or maybe actions in the present influence things earlier in time.

A team of physicists did some thinking, and realized this latter idea, called retrocausality, is a consequence of certain interpretations of quantum mechanics, and therefore, certain interpretations of the nature of reality. Their new paper is more of a what-if, an initial look at how to make some of those quantum mechanical interpretations work. Some people I asked thought the work was important, some thought it didnt matter. Others felt their own interpretation of quantum mechanics avoids the problems posed by the new paper. But no matter what, quantum mechanics will force us to make some uncomfortable conclusions about the world.

The foundations of quantum theory are very controversial. We all agree how to use the theory but theres no consensus about the reality it gives us, study author Matthew Leifer from Chapman University told Gizmodo. This is an unusual situation for a theory in physics, since other theories are mostly based on intuitive things we can see and test. Quantum mechanics math, and its predictions, describe the world perfectly, but its sort of impossible to fully grasp whats actually happening beyond the equations.

Quantum mechanics starts with the observation that at the smallest scale, stuff, whether it be light or a piece of an atom, can act simultaneously like a wave and a particle. That means that scientists deal with some level of probability when it comes to tiny things. Send one electron through a pair of parallel slits in a barrier, and youll see it hit the wall behind the barrier like a dot. But if you send many electrons, youll see a striped pattern as if they traveled like a light wave. You cant predict exactly where one electron will hit, but you can create a list of the most likely spots.

Trouble is, describing particles with probabilities leads to some messy stuff. If you have two particles interacting and ones innate physical properties relies on the others, then their associated probabilities, and therefore their identities, are intertwined. As an example, lets say there are two bags, and each has one of two balls, red or green. You give a bag to your friend. Quantum mechanics only gives the probabilities that your bag contains either ball color, and thats all you know before making the observation. At human scales, each bag already contains a red or green ball. But on the particle scale, quantum mechanics says both balls are red and green at the same timeuntil you look.

Thats weird on its own, but it gets worse. If you look at your ball, the other ball automatically takes on the other color. How does the other ball know that you looked? Maybe there is hidden physics, or faster-than-light travel that allows the information to be communicated. One popular interpretation is that we live in a multiverse. In that case, the probabilities dont say anything about the ball, but about which universe we live in. Seeing a certain ball color just means that youre in the universe where your bag had the green ball. In the other universe, you saw a red ball.

Quantum mechanics is weird as hell, where the rules of the world you experience dont apply. Even

So, researchers want to know which of these interpretations is correct. In their new paper, they specifically tackled cases where observing the first ball directly influences the ball in the other bag, through some form of communication. At first glance, this requires information to travel faster than the speed of light. And that sucks, because theres already a theory that says nothing can travel faster than light. But thats okay, say the researchers, if things can influence other things back in time. Forwards in time, Id look at my red ball, then your bag would mysteriously contain a green ball. The retrocausality case says that backwards in time, we already know both ball colors, and my ball must be red because you already knew your ball was green. Then, the balls go hidden into the bag where they become red and green simultaneously. Basically, in this case, you cant run an experiment where you can control for the effects the future has on the past.

This idea of events in the present influencing things in the past is a mathematical consequence of a pair of the authors assumptions. The first assumption is that quantum mechanics should satisfy their definition of time-symmetry, like lots of other physics theories. That means that particles should behave the same way both forward and played in reversea billiard ball hitting a stationary ball looks the same no matter how you play the tape. The theory should also be real, as Leifer says. This means that the particles are more than a list of numbers, but are instead actual things that behave the same yesterday as they will tomorrow, and have properties that are innate, whether or not the experimenter is able to observe them.

Add the math, and according to the new paper published in Proceedings of the Royal Society A this past week, boom. If you want your theory to be time symmetric, and work the same every day, retrocausality is required.

Most would say this is horrible, of course. If things can influence other things in the past, then who cares about all of science? Why test something at all if the result could be causing the cause? Leifer does offer a solutiona sort of block universe, where events in space and time dont cause one another, but instead fit together like a jigsaw puzzle. But this idea hasnt been developed into a mathematical theory, yet.

Basically, if retrocausality is true, then cause-and-effect is an illusion due to the fact that humans only see things in one direction. The paper is only dealing in what-ifs here, and doesnt get into the specifics of how this effect would manifest, aside from in experiments. But the effect would be built into the very fabric of the universe.

Some physicists didnt find this idea compelling. Christopher Fuchs from the University of Massachusetts, Boston told me that these so-called block universes are neither living nor forced nor momentous for me. He takes these terms from the philosopher William James, and means that the hypothesis doesnt sound like a genuine possibility. It doesnt force him to make a decision one way or the other, and essentially, it isnt groundbreaking. In my mind a far more viable path has already been blazed through very different considerations, treating the observer of the universe as the most important agent, and sort of avoiding the impossible-to-observe.

Physicist Sean Carroll from CalTech thought the new paper was interesting, but he happens to like the already-strange many worlds theory, that says different results manifest in different universes described under the same probabilistic description. Thats the one where, in the red/green ball case, there are actually two universes, one where I saw the red ball and one where I saw the green ball. It is perfectly time-symmetric and reversible under the conventional definitions, he said. And it certainly doesnt require retrocausality. So as usual, if you are willing to take seriously the many worlds inside the wave function... much less weirdness is implied by quantum mechanics in other ways. Essentially, hes willing to trade the weirdness of retrocausality for the weirdness of many worlds.

But another expert I spoke with was far more forgiving, and instead thought of this work as an important go/no-go idea for this line of thinking. This paper makes a mathematical statement around retrocausality, said Renato Renner from ETH Zurich in Switzerland. It says maybe we need it if we want time symmetry, a theory that still works if you play the physics in reverse.He thought this paper was one of the first pieces of research make such a well-defined statement about that concept.

So now, researchers have sat and wracked their brains about a solution to a problem that only arises if they assume certain things about the worldin other words, its a new idea, its only a requirement of the universe if you assume certain other things, and its kind of fringe. But as of now, no matter how you want to understand the fabric of the universe, youre going to need to accept something that feels ridiculous, be it a multiverse, faster-than-light communication, or maybe even a world where the future influences the past.

Theres a substantial group of people trying to understand the question of whats really going on, and can we construct a theory based on stuff that really exists out there, said Leifer. The more different approaches we can think of and try out the better.

[Proceedings of the Royal Society A]

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Basic Assumptions of Physics Might Require the Future to Influence ... - Gizmodo

Quantum physics has spawned its share of strange ideas and hard-to-grasp concepts - from Einsteins spooky action at a distance to the adventures of Shroedingers cat. Now a new study lends support to another mind-bender - the idea of retrocausality, which basically proposes that the future can influence the past and the effect, in essence, happens before the cause.

At this point, retrocausality does not mean that you get to send signals from the future to the past - rather that an experimenters measurement of a particle can influence the properties of that particle in the past, even before making their choice.

The new paper argues that retrocausality could be a part of quantum theory. The scientists expound on the more traditionally accepted concept of time symmetry and show that if that is true, then so should be retrocausality. Time symmetry says that physical processes can run forward and backwards in time while being subject to the same physical laws.

The scientists describe an experiment where time symmetry would require processes to have the same probabilities, whether they go backwards or forward in time. But that would cause a contradiction if there was no retrocausality, as it requires these processes to have different probabilities. What the paper shows is that you cant have both concepts be true at the same time.

Eliminating time symmetry would also get rid of some other sticky problems of quantum physics, like Einsteins discomfort with entanglement which he described as spooky action at a distance. He saw challenges to quantum theory in the idea that entangled or connected particles could instantly affect each other even at large distances. In fact, accepting retrocausality could allow for a reinterpretation of Bell tests that were used to show evidence of spooky action. Instead, the tests could be supporting retrocausailty.

The paper, published in the Proceedings of the Royal Society A, was authored by Matthew S. Leifer at Chapman University in California and Matthew F. Pusey at the Perimeter Institute for Theoretical Physics in Ontario. The scientists hope their work can lead towards a fuller understanding of quantum theory.

"The reason I think that retrocausality is worth investigating is that we now have a slew of no-go results about realist interpretations of quantum theory, including Bell's theorem, Kochen-Specker, and recent proofs of the reality of the quantum state," said Leifer to Phys.org. "These say that any interpretation that fits into the standard framework for realist interpretations must have features that I would regard as undesirable. Therefore, the only options seem to be to abandon realism or to break out of the standard realist framework.

george-musser-explains-spooky-action

Are we going to have time travel as a result of this? In one idea proposed by Richard Feynman,existence of retrocausality could mean that positrons,antimatter counterparts of electrons, would move backwards in time so that they could have a positive charge. If this was proven to be true, time travel could involve simply changing the direction of moving particles in the single dimension of time.

Leifer doesnt go as far as time travel in his explanation, but speculates that if retrocausality does exist in the universe, then there could be evidence of it in the cosmological data, saying that there are certain eras, perhaps near the big bang, in which there is not a definite arrow of causality.

Is this idea ready for the big time? It is supported by Huw Price, a philosophy professor at the University of Cambridge who focuses on the physics of time and is a leading advocate of retrocausality. Leifer and Pusey are taking things in stride, however, realizing that much more work needs to be done.

"There is not, to my knowledge, a generally agreed upon interpretation of quantum theory that recovers the whole theory and exploits this idea. It is more of an idea for an interpretation at the moment, so I think that other physicists are rightly skeptical, and the onus is on us to flesh out the idea, said Leifer.

There are no experiments underway by the physicists to test their theory, but they hope this work will question the assumptions of quantum mechanics and lead to new discoveries down the line.

You can read the study here.

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A New Quantum Theory Predicts That the Future Could Be Influencing the Past - Big Think