[CENTRAAL] Wetenschap & Technologie in het Nieuws 3

HOW OCTOPUSES CO-ORDINATE THEIR ARMS

By Victoria Gill
Science reporter, BBC News

16 April 2015


The study is the first to examine how octopuses co-ordinate their eight, flexible limbs as they crawl

With the aid of high-speed cameras, scientists have revealed how octopuses co-ordinate their arms to crawl.

Researchers from the Hebrew University of Jerusalem filmed crawling octopuses to work out exactly how the animals used their almost limitlessly flexible arms when they move.

This revealed the surprising simplicity of their motion; they just choose which arm to use to push themselves along.

The findings are published in the journal Current Biology.

The study is the first detailed analysis of exactly how octopuses manages to move without a rigid skeleton.

How octopuses control and move their soft bodies is of interest to engineers who aim to design biologically inspired robots.

"People want to build soft robots for medical purposes and rescue operations," said Dr Guy Levy, one of the researchers involved in the project.

Such soft-bodied, octopus-inspired arms would not be limited by fixed joints, he explained. This could be useful to access narrow, difficult to reach spaces - perhaps getting help to people trapped at the scene of a collapsed building.

Pick a leg

To find out the secrets of the octopus's remarkably efficient movement, Dr Levy and his colleague Prof Benny Hochner videoed the animals from underneath as they crawled, and analysed their motion frame by frame.

"The octopus has found a very simple solution to a potentially complicated problem"
Guy Levy , Hebrew University of Jerusalem

This detailed study showed that, by shortening and lengthening, each arm pushed the body in only one direction.

"So the octopus only has to decide which arm to use for the pushing - it doesn't need to decide which direction this arm will push," explained Dr Levy.

"[It has] found a very simple solution to a potentially complicated problem - it just has to pick which arm to recruit."

And because the creatures are able to push off any of their eight legs, they are able to crawl in any direction - no matter which way their body is facing. And, uniquely, there is no rhythm or pattern to their undulating limb movements

The scientists' next step is to delve into the internal circuitry of the octopus nervous system, to find out exactly how this co-ordinated crawling is controlled.

Dr Levy added: "Every time we try to understand something new about the octopus, there are new surprises."

http://www.bbc.com/news/science-environment-32319705

THE LARGEST KNOWN STRUCTURE IN THE UNIVERSE IS A HOLE 1.8 BILLION LIGHT-YEARS ACROSS

Literally a whole lot of nothing.

FIONA MACDONALD

21 APR 2015

Astronomers have stumbled across the biggest object ever detected in the Universe… and it’s a void that stretches for 1.8 billion light years.

Distinguishable by its emptiness, the ‘supervoid’, as it's being called, isn't the only hole in the Universe, but it's the biggest patch we've found, and is abnormal in the typically evenly distributed Universe.
The supervoid was spotted by scientists trying to explain an unusually cool patch in the radiation left over from the Big Bang, known as the Universe’s cosmic microwave background. You can see this patch, which researchers named the 'Cold Spot', circled in the image above, taken by the European Space Agency's (ESA) Planck telescope.

For the past decade, researchers have been extremely interested in the Cold Spot, because it doesn't fit with our current understanding of how the Universe evolved. While a few small warm and cold patches are expected, we shouldn't see such big cold patches, according to the current model.

So an international team of astronomers decided to investigate further, and stumbled across the hole. Although the void isn’t entirely empty, there are an estimated 10,000 galaxies missing from the patch of sky.

Previous studies had missed the supervoid as they were looking too far back - the researchers used the Pan-STARRS1 telescope in Hawaii, and NASA's Wide Field Survey Explorer to count the number of galaxies in a patch of sky just 3 billion light years away.

"This is the greatest supervoid ever discovered," one of the researchers András Kovács, from the Eötvös Loránd University in Budapest, told Hannah Devlin over at The Guardian. "In combination of size and emptiness, our supervoid is still a very rare event. We can only expect a few supervoids this big in the observable universe."

The supervoid isn't actually a vacuum, but because it's so sparse - it contains around 20 percent less matter than the rest of the Universe - it sucks energy from light travelling through it, partially contributing to the Cold Spot's unusually low temperature.

But, frustratingly, it still doesn't fully explain why that region of the sky is so cold.

"The void itself I’m not so unhappy about. It’s like the Everest of voids – there has to be one that’s bigger than the rest," Carlos Frenk, a cosmologist from the University of Durham in the UK, who wasn't involved in the research, told Devlin. "But it doesn’t explain the whole Cold Spot, which we’re still in the dark about."

The one thing the slow-down of light as it passes through the supervoid does support, however, is the fact that the Universe is expanding at an accelerating rate. As Devlin explains:

"This is because the photons convert kinetic energy to gravitational potential as they travel to the heart of the void and get further from denser surrounding patches of universe - think of it as climbing a hill. In a stationary universe, the situation would be symmetrical and so the photons would regain the lost energy on the way out of the void (down the hill) and exit at the same speed.

In an accelerated expansion of the universe, however, everything is effectively becoming less dense as space is stretched out, so voids become relatively shallower over time. This means by the time the light descends the virtual hill, the hill has become flatter and the light cannot pick up all the speed it lost on the way in."

So if you weren't already feeling like the Universe was a cold, lonely place, don't worry, there are now holes out there thousands of times bigger than our entire galaxy.



http://www.sciencealert.c(...)n-light-years-across

quote:

NASA May Have Accidentally Created a Warp Field

_{April 24, 2015 Paul Seaburn}

quote:

To get around the theory of relativity, physicist Miguel Alcubierre came up with the concept of a bubble of spacetime which travels faster than the speed of light while the ship inside of it is stationary. The bubble contracts spacetime in front of the ship and expands it behind it. The warp drive would look like a football inside a flat ring. The tremendous amount of energy it would need made this idea prohibitive until Harold “Sonny” White of NASA’s Johnson Space Center calculated that making the ring into a donut shape would significant reduce the energy needs.

Meanwhile, in the lab, NASA and other space programs were working on prototypes of the EmDrive or RF resonant cavity thruster invented by British aerospace engineer Roger J. Shawyer. This propulsion device uses a magnetron to produce microwaves for thrust, has no moving parts and needs no reaction mass for fuel. In 2014, Johnson Space Center claimed to have developed its own low-power EmDrive.

Which brings us to today’s warp field buzz. Posts on NASASpaceFlight.com, a website devoted to the engineering side of space news, say that NASA has a tool to measure variances in the path-time of light. When lasers were fired through the EmDrive’s resonance chamber, it measured significant variances and, more importantly, found that some of the beams appeared to travel faster than the speed of light. If that’s true, it would mean that the EmDrive is producing a warp field or bubble.

Het artikel is langer.

CHILE'S HUGE VOLCANIC ERUPTION MAKES LIGHTNING, CAN BE SEEN FROM SPACE

Devastatingly beautiful.



FIONA MACDONALD

25 APR 2015

Earlier this week, Chile's Cabulco volcano started erupting for the first time in 43 years, spraying dust and ash at least 15 kilometres into the sky, and causing the evacuation of up to 2,000 local residents.

Thankfully there have been no casualties or serious injuries reported, but the volcano has put on one hell of a show, producing a breathtaking display of volcanic lightning with its second eruption and blasting out red-hot rocks and lava. You can marvel at the power of nature in the incredible time-lapse footage below.


What causes volcanic lightning? As Bec Crew wrote for ScienceAlert last month, this eerily beautiful phenomenon is triggered when giant ash clouds spew out of a volcano's mouth: "As the individual ash particles make contact and rub against each other, they produce enough static electricity to convert into bursts of lightning."

This ash cloud has since caused flight cancellations as it blows across South America, and has produced a plume that can be seen from space. The below infrared image was taken by the Suomi NPP satellite on 23 April.



NASA’s Terra satellite also snapped a natural-colour photo of the ash plume, below:



And there have been no shortage of amazing Earth-bound images across Twitter.

https://twitter.com/LKrauss1

You can see the volcano's initial eruption unfolding below, and follow Indefinitely Wild's coverage for updated footage and photos.

Bron: http://www.sciencealert.c(...)n-be-seen-from-space

Met een muziekje erbij



[ Bericht 5% gewijzigd door Kijkertje op 25-04-2015 23:00:45 ]

ARE SPACE AND TIME AN ILLUSION?

Thanks to this explainer, you no longer have to pretend you understand the concept of spacetime!

28 APR 2015


What exactly is spacetime? Well, it's a mathematical model that combines measurements of both space and time into a single continuum, with space consisting of three dimensions, and time consisting of one dimension - known as the fourth dimension. Simple! Okay, it's really not, but the video above by the PBS Space Time channel is here to explain it all to you in the easiest way possible.

First off, if we can already quantify both space and time, why do we need to combine them into an entirely new measurement? As Gabe Perez-Giz explains in the video above, we need it because we could have two 'observers' of space and time - two different types of particles, for example - and they could both disagree on how much space there is between things at any given point in time.

They could even disagree about the actual sequence of events that have occurred. But as long as their measurements are consistent, neither observer is wrong. Both particles have the correct measurements of space and time, despite coming up with completely different answers.

Put simply, this means that an event in someone's past could be in someone else's future, and there would be nothing 'wrong' about either of their realities. "Any disagreement means that there is no universal division of events in the past, present, and future, which opens major philosophical cans of worms for things like free will, and our belief that we can change the future," says Gabe. "So is everyone's experience of the Universe entirely subjective? If time and space as we usually conceive of them aren't part of objective reality, then what is?"

If you're confused, that's okay, if you're intrigued, good! The video above has the answers you need, and you just might come out of it with a brand new, much clearer understanding of one of the most important concepts in physics (and a thoroughly blown mind). You're welcome.

Bron: http://www.sciencealert.com/watch-are-space-and-time-an-illusion

MATHEMATICIANS DISPUTE CLAIMS THAT THE 'GOLDEN RATIO'IS A NATURAL BLUEPRINT FOR BAUTY


Experts blast 'myth that refuses to go away', saying that sums alone cannot define which faces are easy on the eye

Revered as the formula that defines beauty, the golden ratio is a mathematically derived principle claimed by many to be embodied in objects as diverse as a spiralled seashell and the Parthenon.


But the widespread belief that the golden ratio is the natural blueprint for beauty is pseudo-scientific “hocus-pocus” and a “myth that refuses to go away”, according to leading mathematicians.

The issue has flared up again, after one of the United States’s leading scientific organisations, the Smithsonian, promoted highly contentious claims about the ratio at the National Math Festival in Washington DC earlier this month.


Theories that the Parthenon in Athens, pictured, and Great Pyramid in Egypt were built according to the golden ratio have also been disproved (EPA)

Eve Torrence, a professor at Randolph–Macon College in Virginia, said she was appalled to find a Smithsonian-branded stall which claimed the golden ratio is found in the human body. It offered visitors the chance to put their head through an oval, allegedly to demonstrate whether their face was in accordance with what is also known as the “divine proportion”.

“The idea that there’s this one rectangle [based on the golden ratio] that’s this perfect one... and is reflected in the human body, that’s one of the most silly things. Human beings are so different,” she said.

“There are lots of ratios and proportions in the human body, but they are not all the golden ratio and they are not all precisely the golden ratio. It’s a very loosey-goosey, pseudo-science kind of thing that they are promoting.

“There’s not this number that’s got this perfection in the way people think it does. It feels dirty to mathematicians. It’s hocus-pocus.”

However, there is genuine maths behind the ratio itself. First described by Euclid, it is created by dividing a line into two unequal sections in such a way that the ratio between the whole line and the longer section is the same as the ratio between the longer and shorter sections. This works out at approximately 1.618:1.

The ratio can be used to create different shapes such as a rectangle, triangle or a spiral. The spiral shapes are found in some plants.

But Dr Keith Devlin, a Stanford University mathematician, said Euclid had never claimed the ratio had any aesthetic qualities, an idea largely invented by Gustav Theodor Fechner, a 19th-century German psychologist. More recently it appeared in a 1959 educational cartoon, Donald in Mathmagic Land, and Dan Brown’s The Da Vinci Code.


The ratio can be used to create different shapes such as a rectangle, triangle or a spiral. The spiral shapes are found in some plants (Rex)

Dr Devlin, who campaigns against myths associated with the golden ratio, pointed to “considerable evidence” that people do not find golden rectangles more appealing than others. On the contrary, they tend to favour aspect ratios they are familiar with, such as an A4 piece of paper or a computer screen.

He also said the popular idea that the navel divides the human body in accordance with the golden ratio is false. The figures are close, but there is considerable variation.

Theories that the Parthenon in Athens and Great Pyramid in Egypt were built according to the golden ratio have also been disproved, he said. “The golden ratio stuff is in the realm of religious belief. People will argue it is true because they believe it, but it’s just not fact.”

Such views are dismissed by believers such as Dr Stephen Marquardt, a plastic surgeon and chief executive of Marquardt Beauty Analysis in California, who has patented facial grids derived from the golden ratio to guide surgery.


The golden ratio is a mathematically derived principle but is not present in the spiral of a Nautillus shell (Rex)

Asked about the mathematicians’ objections, he said: “I would say they haven’t done their homework... Mathematicians have their heads up their asses about half the time.”

Dr Marquardt said Marilyn Monroe’s face was “not perfect” but “pretty close”, while Angelina Jolie was “all right [but] her lips are a little large”. The closest fits to golden-ratio defined perfection were Audrey Hepburn and Pierce Brosnan.

The Smithsonian refused to discuss the claims made on its stall.

Bron: http://www.independent.co(...)beauty-10204354.html

THIS NEW METAL BOX COULD HELP TAKE PHYSICS BEYOND THE STANDARD MODEL

Welcome to the weakest magnetic field in the Solar System.


FIONA MACDONALD 14 MAY 2015

Researchers in Germany have created a shield that can cut magnetic fields more than a million-fold, and they've used it to create one of the most exciting metal boxes on the planet right now.

The 4.1-cubic-metre space has the weakest magnetic field in our Solar System, and it will allow scientists to finally conduct the high-precision experiments that could reveal physics beyond the Standard Model.

The Standard Model of particle physics, also known as 'The Theory of Almost Everything', is the best set of equations we have to explain the behaviour and interactions of the fundamental particles in the Universe.

But although the model has served us well, there are a whole lot of gaps, such as the fact that the Standard Model doesn't explain gravity, or why matter and antimatter from the Big Bang didn't annihilate each other completely. It also can't predict the behaviour of particles at very high energies.

Large-scale experiments such as the Large Hadron Collider are helping to improve our understanding in these areas, but are limited by the natural and artificial magnetic fields on Earth, which have the unfortunate habit of easily penetrating all kinds of matter.

But now, researchers from Technische Universität Müchen (TUM) in Germany have managed to eliminate magnetic fields to previously unheard-of levels, opening up a whole new world of experiments. In fact, their box's magnetic field is even weaker than the average ambient magnetic field experienced in the interstellar medium between galaxies.

"Precision experiments are able to probe nature up to energy scales which might not be accessible by current and next generation collider experiments," Tobias Lins, a doctoral student who worked on the magnetic shield, said in a press release. This is because the existence of exotic new particles could be detected by tiny alterations in the properties of already known particles, but we currently can't track those changes because of the background 'noise' from magnetic fields.

The shield, which involves several layers of a specially made, highly magnetic nickel-and-iron alloy, acts like a sponge that absorbs and redirects a magnetic field. The researchers describe its design and performance in the Journal of Applied Physics.

Astrid Eckert/Technische Universität Müchen

"The apparatus might be compared to cuboid Russian nesting dolls," said Lins. "Like the dolls, most layers can be used individually and with an increasing number of layers the inside is more and more protected."

They're already planning to use their shield to determine the charge distribution in neutrons - referred to by physicists as the electric dipole moment. Essentially what they're looking for is the brief moment when a neutron has a tiny magnetic charge - generally a neutron is electrically neutral because its three quarks cancel each other out. If they find that this moment lasts for longer than predicted by the Standard Model, it could suggest the existence of a new particle.

"This kind of measurement would be of fundamental significance in particle physics and swing wide open the door to physics beyond the Standard Model of particle physics," explained the team leader, Peter Fierlinger, in a statement.

The team also wants to use the shield to search for the long-theorised, but never detected, magnetic monopoles using a SQUID detector, which can detect extremely subtle magnetic fields.

Both of these experiments, as well as the many others that can now be conducted inside this small, metal box, could take us into a brave new world of physics, and we can't wait to see some results. We've said it before, and we'll say it again: what an incredible time to be alive.

http://www.sciencealert.c(...)d-the-standard-model

AN ELECTRONIC MEMORY CELL HAS BEEN CREATED THAT MIMICS THE HUMAN BRAIN

Bionic brains are getting closer.

FIONA MACDONAL 18 MAY 2015

Scientists have built a tiny, long-term memory cell that can both store and process information at the same time, just like the human brain. This is one of the first multi-state electronic memory cells, and it represents a crucial step towards building a bionic brain.

Not only does this new cell - which is 10,000 times thinner than a human hair - open up the potential to store and process way more data than ever before, scientists are even more excited about the fact that it has 'memristive' abilities. This means that it's able to retain remember and be influenced by information that has previously been stored on it - something that our current storage devices aren't capable of.

This is the closest we have come to creating a brain-like system with memory that learns and stores analog information and is quick at retrieving this stored information," project leader Sharath Sriram, from RMIT University in Australia said in a press release. "The human brain is an extremely complex analog computer ... its evolution is based on its previous experiences, and up until now this functionality has not been able to be adequately reproduced with digital technology."

The cell's new abilities add another dimension beyond the on/off memory cells we currently use to store our data on conventional devices, such as USBs, which are only capable of storing one binary digit (either a 0 or a 1) at a time. The researchers are comparing this to the difference between a regular light switch, which either turns the light on or off, and a dimmer switch, which gives you access to all the shades of light in-between.

"It can give you much more flexibility in terms of what information you store and what functionality you get," one of the researchers, Hussein Nili, told Jessica Kidd over at ABC News.

Publishing in Advanced Functional Materials, the researchers explain that the cells are made out of a functional oxide material in the form of an ultra-thin film. The team created the material last year, and demonstrated that it was highly stable and reliable. But they've now successfully introduced controlled defects into the film, which allow the cell to be influenced by previous events.

"We have now introduced controlled faults or defects in the oxide material along with the addition of metallic atoms, which unleashes the full potential of the 'memristive' effect - where the memory element's behaviour is dependent on its past experiences," Nili explained in the release.

All this means that the cells could one day be used to build an artificial system that mimics the extraordinary abilities of the human brain, which is extremely fast, requires very little energy input, and has almost limitless memory storage. While the benefits to artificial intelligence and computing are obvious, such a 'bionic brain' could also greatly help human health by allowing researchers to create and study diseases such as Alzheimer's and Parkinson's outside of the body.

"In terms of those diseases, there are two problems: it is very hard to read what is going on inside a live brain, and the ethical aspect - you cannot experiment on live subjects without repercussions," Nili told Ariel Bogle from Mashable. "If you can have a bionic brain and you can replicate those kinds of [diseased] brains ... it will make research much easier and accessible."

We're pretty excited to see what these little cells can do.

http://www.sciencealert.c(...)mics-the-human-brain

IMAGES OF SUPERNOVAE MINUTES AFTER IGNITION CHALLENGES MAIN THEORY OF FORMATION

They can occur, it seems, when stars collide.

MYLES GOUGH 22 MAY 2015

An international team of scientists has captured the earliest images of supernovae in action - only minutes after ignition - and they say these massive stellar explosions are occurring after stars collide, challenging theories that supernova occur in a uniform way.

A supernova is a stellar explosion that can briefly outshine an entire galaxy, comprised of billions of stars. Using the Kepler space telescope, researchers photographed three of these cosmic events between 600 and 1.8 billion light-years from Earth.

They were looking specifically at type Ia supernovae, which involve the explosive deaths of ageing white dwarf stars that exist in a binary orbit with a sister star.

"We were able to capture the supernovae in the first minutes of the explosion, the earliest previously had been two-and-a-half hours after the event," astrophysicist and team member Brad Tucker, from the Australian National University, told Stuart Gary at ABC Science.

The team tracked the explosions in detail until they reached their pinnacle of brightness three weeks later, and then monitored the subsequent declines, as their light signatures faded away over the next few months.

They found that the initial stages of their supernovae didn't fit very well with prevailing theories about how they occur.

"The stars all blow up uniquely. It doesn't make sense," Tucker said in a press release. "It's particularly weird for these supernovae because even though their initial shockwaves are very different, they end up doing the same thing."

Before their study offered an unprecedented glimpse into the early stages of this stellar phenomena, astronomers only had information about what was happening in type Ia supernovae 2.5 hours after the star's explosive dying process had commenced.

What they observed was that after this 2.5-hour mark, the dying stars all followed an identical pattern. This led to theories that they might also originate in identical ways.

The prevailing theory has been that these explosions occur when the compact white dwarf - or the dying star - uses its gravity to pull hot material from its companion star onto its surface. Eventually, the added heat and pressure causes the star's core to explode.

But the team found no evidence of the supernovae ejecta interacting with a companion star, as might be expected.

"Somewhat to our surprise the results suggest an alternative hypothesis, that a violent collision between two smallish white dwarf stars sets off the explosion," lead researcher Robert Olling from the University of Maryland in the US, said in a press release.

The team's results, which were recently published in Nature, provide new insight into how some of these explosions form and could help astronomers use their light signatures to more accurately gauge cosmic distances between galaxies.

But it doesn't cancel out the other formation theory: a second paper published in the same issue of Nature by a different team has found evidence to support the view that these events can still be triggered by stars accreting matter from their companions.

The team from the California Institute of Technology used NASA's Swift space telescope to study a supernova 300-million-light-years away. They found that as the ejected material expanded outwards it eventually collided with the companion star. They say this provides evidence that the explosion is resulting from a single degenerating star, rather than a collision.

"As the blast wave hits the companion star it interacts with it and generates ultraviolet emissions which we detected with Swift," lead author and graduate student, Yi Cao, told ABC Science.

"We realised that this was probably the supernova companion interaction and we were very excited because we have been searching for this signal for a while."


http://www.sciencealert.c(...)-theory-of-formation

http://www.abc.net.au/science/articles/2015/05/21/4239232.htm



[ Bericht 5% gewijzigd door Kijkertje op 22-05-2015 15:34:29 ]

AMPUTEES CAN NOW CONTROL BIONIC LEGS WITH THEIR MIND

The future looks so good.


BEC CREW 21 MAY 2015

Scientists in Iceland have invented new bionic prosthetic limbs that can be controlled by a person’s thoughts alone, and they’re so good, two patients are already trialling the technology.

Developed by a company called Ossur, the world-first technology involves surgically implanting 5 mm by 3 mm myoelectric sensors (IMES) into a person’s residual muscle tissue to measure and interpret the signals travelling between its nerve-endings and the brain. Leg movement is triggered by a connected receiver, and the process is so streamlined, it allows a patient to perform actions subconsciously.

"The brain power, when it takes over, actually gives impulses through the brain into the muscles, then the muscles contract," orthopaedic surgeon and director of research and development at Ossur, Thorvaldur Ingvarsson, told Amy Pollack at Reuters. "We put sensors into the muscles, and the muscles would pick up the signals, and the signals move their way into the prosthetics, and then the prosthetics react as your brain wants."

The technology differs from similar mind-controlled prosthetics because it doesn’t require muscle tissue to be transplanted from another part of the body into the affected area, says Pollock. This requires an intense amount of mental training by the patient, because their brain has to get used to their muscle tissue functioning in a completely different region of the body.

One of the two amputees who has been trialling the bionic legs for the past 12 months, Gummi Olafsson, described to Pollock the bizarre feeling of controlling a piece of technology like it was a natural part of his body:

"As soon as I put my foot on, it took me about 10 minutes to get control of it. I could stand up and just walk away. Come back, sit down, use my muscles to move my foot in the position I wanted to use it. It was like you couldn't believe the feeling when you were moving your ankle. It was really strange. I couldn't explain it. It was like, I was moving it with my muscles, there was nobody else doing it, the foot was not doing it, I was doing it, so it was really strange and overwhelming."

Olafsson added that practice is everything when it comes to figuring out how to better manipulate the bionic legs, and is now working on diversifying his skills to get him uphill, downhill, upstairs, downstairs, and sitting and standing on a chair.

And what’s really awesome about this technology is that it's compatible with current bionic legs that amputees around the world have already gotten used to. Patients will now be able to upgrade their existing prosthetics, which have already been adapted to their individual walking style, with the capacity for mind-control.

Ingvarsson says that the next step for the technology might be to embed a network of sensors into the prosthetic limbs to create a feedback loop about what’s going on in the surrounding environment, similar to how sensors in driverless cars create an impression of the pathways and obstacles around them.

Watch the technology being tested here:


http://www.sciencealert.c(...)legs-with-their-mind

OCTOPUSES AND THEIR RELATIVES SENSE LIGHT THROUGH SKIN

Sensors in their skin detect changes in the colour of light, and in response the animals change colour to camouflage themselves

Whether it's a dull sandy seabed or a multi-coloured coral reef, octopuses change the colour of their skin to blend in perfectly with their environment. It now seems their skin is not just obeying instructions from the octopus's brain: it also has local sensors that can perceive light and trigger a colour change.

Soft-bodied cephalopods like octopuses, squid and cuttlefish rely on camouflage to escape from predators. In the highly colourful undersea world, this means constantly changing their skin to match the environment.

Their eyes perceive the surroundings, then the brain processes the information and sends signals directly to the skin, causing dramatic changes of colour and pattern in a matter of milliseconds.

But it's not just the brain that controls the skin patterning, according to two studies in the Journal of Experimental Biology.


A California two-spot octopus (Octopus bimaculoides) (Credit: Visuals Unlimited/NPL)

Desmond Ramirez and Todd Oakley of the University of California Santa Barbara cut out bits of skin from California two-spot octopuses and kept them in their lab. They found that even though the piece of skin was not "alive" and connected to an octopus, it could still respond to light.

Octopus skin is covered with specialised pigmented organs called chromatophores, which are basically tiny bags filled with coloured chemicals. If the muscles around the chromatophore contract, the bag gets stretched out, revealing the colour.

When Ramirez exposed the biopsied skin to white light, the chromatophores expanded significantly: five-fold in adult skins and two-fold in hatchling skins.

The response was slower than in whole octopuses. Once they were exposed to white light, adult chromatophores took about 6s to start responding, and another 5s to expand fully. "In whole animals, the changes in the chromatophores happen much more quickly," says Ramirez.


A broadclub cuttlefish (Sepia latimanus) (Credit: Inaki Relanzon/NPL)

Animals have specialised proteins called opsins that respond to light. He and Oakley found that the genes coding for opsins were activated in the octopus skin.

It was the same type of opsin found in the octopus eye, contained in sensory neurons that were packed into the entire surface of each octopus's mantle, head and arms.

The same seems to be true of other cephalopods, according to a second study in the same journal by Thomas Cronin of the University of Maryland Baltimore County and his colleagues.


A pair of common cuttlefish (Sepia officinalis) (Credit: Alex Mustard/NPL)

Working with two cuttlefish and a squid, the group was able to show that all the proteins involved in light detection in the cephalopods' eyes were also found in the skin -- specifically, inside their chromatophores.

The findings suggest that cephalopods have two ways of controlling their skin colour. One is central, driven by the brain, and the other is spread throughout their skin.

"What we do not yet know is how these two inputs come together to control chromatophores in the whole animal," says Ramirez.



http://www.bbc.com/earth/(...)-see-with-their-skin

NASH'S MIND LEFT A BEAUTIFUL LEGACY

Death of game theory pioneer ends a genius’s dramatic story

by Tom Siegfried 3:50pm, May 24, 2015


Mathematician John Nash died in a car accident May 23 at the age of 86, ending a dramatic story of genius.

His mind was beautiful, but troubled. His math was just beautiful.

John Forbes Nash Jr., who died in a traffic accident on May 23, gained more fame than most mathematicians, though not only on account of his math. His battle with schizophrenia, described artfully by Sylvia Nasar in her book A Beautiful Mind, made for drama suitable for a movie. Russell Crowe played Nash in the 2001 film, which garbled the math but made the point that despite his affliction, Nash accomplished works of genius — particularly in the theory of games.

That genius emerged in the 1940s when Nash was an undergraduate at Carnegie Tech, the forerunner to Carnegie Mellon University, in Pittsburgh. He started out as an electrical engineering student, but soon shifted to chemical engineering and then just plain chemistry. But the lab was not for him. He switched to math, and by age 20 he was on his way to graduate school at Princeton with a one-sentence letter of recommendation from a Carnegie professor: “This man is a genius.”

At Princeton, Nash revolutionized economic theory, showing how the freshly developed game theory of the great John von Neumann and Oskar Morgenstern could be made more relevant to real life. In their book, Theory of Games and Economic Behavior, von Neumann and Morgenstern had attempted to derive a mathematics of strategy. They showed how participants in an economy could choose the most profitable behaviors. Von Neumann, one of the foremost mathematicians of his time, and Morgenstern, an economist, realized that their math could be applied to human behavior more broadly, evaluating strategic choices in realms from poker to warfare.

But the original theory offered rigorous solutions only for two-person games where the winner won what the loser lost (hence the label “zero-sum” game). Nash extended game theory both to cooperative situations (where win-win scenarios were possible) and to competitive games with multiple players.

Out of this work came the concept of the “Nash equilibrium,” the set of strategies that guaranteed the best possible payoff for all participants. Nash’s genius was to prove that at least one such set of strategies was always possible. In other words, as the economist Samuel Bowles once put it, there is always “a situation in which everybody is doing the best they can, given what everybody else is doing.”

In such situations, “equilibrium” means that as long as everybody else maintains the same strategy, anybody changing strategies would suffer a worse outcome. So equilibrium describes a stable situation, in which nobody has any incentive to change strategies.

Nash’s equilibrium became the bedrock upon which game theory’s future was built. “The concept of the Nash equilibrium is probably the single most fundamental concept in game theory,” Bowles said. And the economist Roger Myerson called it “one of the outstanding intellectual advances of the 20th century … comparable to that of the discovery of the DNA double helix.”

One of the deepest insights stemming from game theory is the notion that rarely is it wise to stick to a single strategy. In any but the simplest situations, Nash equilibrium is achieved only when players pursue a “mixed strategy.” In other words, a behavior is chosen from a probability distribution — a mix — of different specific strategies. In poker, for instance, a smart player with a losing hand sometimes bluffs and sometimes folds; game theory’s probability distribution tells you what percentage of the time to choose each strategy. This concept of mixed strategies explains all sorts of things about the natural world, from why ecosystems contain so many different species to why some people are cooperators while others are selfish.

Nash made other significant contributions to mathematics in the 1950s, but the dark specter of schizophrenia removed his mind from active engagement in the intellectual world for decades. But eventually his symptoms subsided. And then he was awarded the economics Nobel Prize in 1994, leading to the recognition of his work in both the book and movie A Beautiful Mind.

My own book on game theory emphasized the intellectual fallout from Nash’s math in fields other than economics. His methods were adopted, or adapted, in fields ranging from international diplomacy to evolutionary biology. Today it is widely acknowledged that game theory provides a common mathematical language for analyzing research across the entire spectrum of the social sciences. Game theory provides a method for quantifying human behavior, even though humans don’t always behave in the way a naïve application of game theory would suggest.

Game theory’s reach has extended beyond social sciences and biology. The probabilities involved in computing mixed game theory strategies are similar to those in other fields, such as statistical physics, information theory and even quantum mechanics, in the form of quantum game theory.

Nash, in fact, derived his notion of equilibrium in the first place from an analogy to physical science. When he studied chemistry, he encountered the law of mass action, the math describing how chemical reactions reach equilibrium. It’s a purely physical process of course, governed by the laws of thermodynamics, which drive natural systems to a state of energetic stability. Nash showed how a thoroughly analogous process, governed by the math of game theory, can drive economic or other social systems to a state of stability.

As I wrote recently, there are indications that game theory could prove useful in solving mysteries ranging from how to cure cancer to the origin of life. Perhaps game theory generally, and the Nash equilibrium in particular, captures something about relationships in the world that goes deeper than mere analogy. If so, that would be beautiful.

https://www.sciencenews.o(...)utiful-legacy?tgt=nr

UNCOMFORTABLY NUMB: THE PEOPLE WHO FEEL NO PAIN.

Researchers have identified a third gene that causes congenital insensitivity to pain when mutated


Dental syringe and lignocaine ampules. Photograph: Wellcome Images

Being unable to feel pain may sound appealing, but it would be extremely hazardous to your health. Pain is, for most of us, a very unpleasant feeling, but it serves the important evolutionary purpose of alerting us to potentially life-threatening injuries. Without it, people are more prone to hurting themselves and so, because they can be completely oblivious to serious injuries, a life without pain is often cut short.

Take 16-year-old Ashlyn Blocker from Patterson, Georgia, who has been completely unable to sense any kind of physical pain since the day she was born. As a newborn, she barely made a sound, and when her milk teeth started coming out, she nearly chewed off part of her tongue. Growing up, she burnt the skin off the palm of her hands on a pressure washer that her father had left running, and once ran around on a broken ankle for two whole days before her parents noticed the injury. She was once swarmed and bitten by hundreds of fire ants, has dipped her hands into boiling water, and injured herself in countless other ways, without ever feeling a thing.

Ashlyn is one of a tiny number of people with congenital insensitivity to pain. The condition is so rare, in fact, that the doctor who diagnosed her in 2006 told her parents that she may be the only one in the world who has it. But later that year, a research team led by Geoffrey Woods of the University of Cambridge, identified three distinct mutations in the SCN9A gene, all of which cause the same condition in members of three large families in northern Pakistan, and in 2013, Ashlyn’s doctor Roland Staud and his colleagues reported that her condition is the result of two other mutations in the same gene.

Now, Woods and his colleagues have discovered yet more mutations that cause congenital insensitivity to pain. They studied 11 families form around the world, and identified within them 158 individuals, all of whom suffer from either congenital pain insensitivity or hereditary sensory and autonomic neuropathy, another rare condition that also causes loss of pain sensation by damaging the nerves that carry pain signals up the spinal cord and then into the brain.

Using state-of-the-art DNA sequencing techniques, the researchers analysed and compared their genomes, and identified no less than 10 different mutations that cause congenital insensitivity to pain, all within a gene called PRDM12, located on the long arm of chromosome 9.

Individuals carrying two defective copies of this gene produce a non-functional PRDM12 protein, and as a result of this have been unable to feel any kind of physical pain, or to distinguish between painfully hot and cold temperatures, from birth. Most of them have experienced numerous, painless injuries. As infants and young children, they bit their fingers, toes, and lips so often that they are severely mutilated, and hurt themselves many times and in many other ways. The worst affected have suffered repeated infections while growing up, injuries that scarred their skin and deformed their bones.

PRDM12 is the third human gene to be associated with congenital insensitivity to pain. SCN9A was the first such gene to be discovered, and we now know of at least 13 different mutations in it, all of which cause congenital insensitivity to pain. In 2013, another research team reported that they had identified a mutation in a related gene, called SCN11A, which also causes the condition. SCN9A and SCN11A encode sodium channel proteins that pain-sensing fibres need to generate nervous impulses.

Mutations in SCN9A produce a non-functional sodium channel, so that pain fibres can still detect painful stimuli but are unable to send signals about them to the brain. The SCN11A mutation produces over-active sodium channels that interfere with the pain fibres’ ability to produce and send their impulses.

The PRDM12 mutations cause pain insensitivity another way. When Woods and his colleagues examined biopsies from several of the affected people they studied, they found that the skin in their legs contains no nerve endings whatsoever, and that one of the sensory nerves in their legs contains about half the normal number of pain-sensing fibres. This led them to speculate that PRDM12 plays an important role in the development of pain-sensing neurons and their fibres.

Exploring further, they examined the distribution of PRDM12 in developing mouse embryos, and in pain neurons generated from human stem cells. This revealed that the protein is synthesized at the exact time when pain neurons are forming, and in exactly the right places – in the region where immature pain neurons are first created, along the migration route they take before maturing, and in the dorsal root ganglia and superficial layers of the spinal cord, where their cell bodies and fibres end up, respectively.

The researchers then reduced the amount of PRDM12 protein synthesized by developing frog embryos, and found that this significantly altered the distribution of pain nerves. The PRDM12 protein is a transcription factor, or a “master control gene” that regulates the activity of dozens of other developmental genes. Woods and his colleagues performed one final set of experiments which suggest that it does so by means of epigenetic modifications that switch these genes on or off by altering chromosome structure.

These results confirm that PDRM12 is essential for the development of pain-sensing neurons, and neatly explain why it causes pain insensitivity when mutated. Whereas people with a mutation in SCN9A or SCN11A have pain fibres that don’t send signals, those carrying a PDRM12 mutation fail to develop pain fibres altogether.

Pain is a major global health problem that affects a significant proportion of the world’s population, and has an estimated annual cost of at least $560 billion in the U.S. alone. Management of chronic pain – defined as any pain lasting longer than 3 months – can be especially difficult, as it often presents itself with no underlying physical cause.

These new findings open up promising avenues for understanding pain, and suggests that it may be possible to develop new analgesics that target PRDM12 and provide relief by epigenetic “reprogramming” of over-active pain neurons.

http://www.theguardian.co(...)ple-who-feel-no-pain

HUMANS WILL BE CYBORGS WITHIN 200 YEARS, EXPERT PREDICTS

“It will be the greatest evolution in biology since the appearance of life.”

FIONA MACDONALD 29 MAY 2015

Within the next 200 years, humans will have become so merged with technology that we’ll have evolved into “God-like cyborgs”, according to Yuval Noah Harari, an historian and author from the Hebrew University of Jerusalem in Israel.

Harari researches the history of the human species, and after writing a new book on our past, he now believes that we’re just a few short centuries away from being able to use technology to avoid death altogether - if we can afford it, that is.

“I think it is likely in the next 200 years or so Homo sapiens will upgrade themselves into some idea of a divine being, either through biological manipulation or genetic engineering of by the creation of cyborgs: part organic, part non-organic,” Harari said during his presentation the Hay Festival in the UK, as Sarah Knapton reports for the Telegraph. “It will be the greatest evolution in biology since the appearance of life … we will be as different from today’s humans as chimps are now from us.”

Obviously, we should take Harari’s predictions with a grain of salt, but while they sound more suited to science fiction than real life, they're not actually that out-there. Many researchers believe that we’ve already started down the path towards a cyborg future; after all, many of us already rely on bionic ears and eyes, insulin pump technology and prosthetics to help us survive. And with researchers recently learning how to send people’s thoughts across the web, subconsciously control bionic limbs and use liquid metal to heal severed nerves, it’s not hard to imagine how we could continue to use technology to supplement our vulnerable human bodies further.

Interestingly, Harare’s comments came just a few days after UK-based neuroscientist Hannah Critchlow from Cambridge University got the Internet excited by saying that it could be possible to upload our brains into computers, if we could build computers with 100 trillion circuit connections. “People could probably live inside a machine. Potentially, I think it is definitely a possibility,” Critchlow said during her presentation at the festival.

But Harari warned that these upgrades may only be available to the wealthiest members of society, and that could cause a growing biological divide between rich and poor - especially if some of us can afford to pay for the privilege of living forever while the rest of the species dies out.

If that sounds depressing, the alternative is a future where instead of us taking advantage of technology, technology takes advantage of us, and artificial intelligence poses a threat to our survival, as Elon Musk, Stephen Hawking, and Bill Gates have all predicted.

Either way, one thing seems pretty clear - our future as a species is now inextricably linked with the technology we've created. For better or for worse.


http://www.sciencealert.c(...)ears-expert-predicts

WATCH: THE ARCHER'S PARADOX IN SLOW MOTION

Because arrows don't actually fly straight.

FIONA MACDONALD 29 MAY 2015


If you're anything like me, you probably think that an arrow shoots pretty straight - hence the saying 'straight as an arrow', right? But it turns out, that's not the case at all, as Destin reveals so spectacularly in the latest episode of Smarter Every Day, where he sets out to uncover the physics behind the Archer's Paradox.

So what is this paradox? In order to shoot an arrow, you need to place it either to the right or left of your bow. But in order to hit your target, you need your arrow to fly in a straight line. So somehow archers manage to curve their arrows around that obstacle in order to hit their target... and as Destin proved in another recent episode, archers are able to hit some incredibly tiny targets.

To figure it out, Destin sets up his Phantom slow-motion camera, and experiments with a range of different bows. What he finds is that the solution to this paradox all comes down to the arrow, which actually isn't rigid at all. In fact, it not only bends once to get around the bow, once it's released, it curves the whole way to the target, creating a wave pattern complete with nodal points through the air, which keeps it on a straight path.

But how do archers know how their arrow's spine is going to curve in order to have such incredible accuracy? That's actually a pretty cool process, which requires some serious science. Watch the episode above to find out, and fully appreciate how talented archers really are.

http://www.sciencealert.c(...)radox-in-slow-motion

THE STRANGE FATE OF A PERSON FALLING INTO A BLACK HOLE

If you fell into a black hole, you might expect to die instantly. But in fact your fate would be far stranger than that

It could happen to anyone. Maybe you're out trying to find a new habitable planet for the human race, or maybe you're just on a long walk and you slip. Whatever the circumstances, at some point we all find ourselves confronted with the age-old question: what happens when you fall into a black hole?

You might expect to get crushed, or maybe torn to pieces. But the reality is stranger than that.

The instant you entered the black hole, reality would split in two. In one, you would be instantly incinerated, and in the other you would plunge on into the black hole utterly unharmed.


Heavy objects warp the fabric of space itself (Credit: Julian Baum/SPL)

A black hole is a place where the laws of physics as we know them break down. Einstein taught us that gravity warps space itself, causing it to curve. So given a dense enough object, space-time can become so warped that it twists in on itself, burrowing a hole through the very fabric of reality.

A massive star that has run out of fuel can produce the kind of extreme density needed to create such a mangled bit of world. As it buckles under its own weight and collapses inward, space-time caves in with it. The gravitational field becomes so strong that not even light can escape, rendering the region where the star used to be profoundly dark: a black hole.

The outermost boundary of the hole is its event horizon, the point at which the gravitational force precisely counteracts the light's efforts to escape it. Go closer than this, and there's no escape.

The event horizon is ablaze with energy. Quantum effects at the edge create streams of hot particles that radiate back out into the universe. This is called Hawking radiation, after the physicist Stephen Hawking, who predicted it. Given enough time, the black hole will radiate away its mass, and vanish.

As you go deeper into the black hole, space becomes ever more curvy until, at the centre, it becomes infinitely curved. This is the singularity. Space and time cease to be meaningful ideas, and the laws of physics as we know them — all of which require space and time — no longer apply.

What happens here, no one knows. Another universe? Oblivion? The back of a bookcase? It's a mystery.


In a black hole, space becomes infinitely curved (Credit: Henning Dalhoff/SPL)

So what happens if you accidentally fall into one of these cosmic aberrations? Let's start by asking your space companion — we'll call her Anne — who watches in horror as you plunge toward the black hole, while she remains safely outside. From where she's floating, things are about to get weird.

As you accelerate toward the event horizon, Anne sees you stretch and contort, as if she were viewing you through a giant magnifying glass. What's more, the closer you get to the horizon the more you appear to move in slow motion.

You can't shout to her, as there's no air in space, but you might try flashing her a Morse message with the light on your iPhone (there's an app for that). However, your words reach her ever more slowly, the light waves stretching to increasingly lower and redder frequencies: "Alright, a l r i g h t, a l r i…"

When you reach the horizon, Anne sees you freeze, like someone has hit the pause button. You remain plastered there, motionless, stretched across the surface of the horizon as a growing heat begins to engulf you.

According to Anne, you are slowly obliterated by the stretching of space, the stopping of time and the fires of Hawking radiation. Before you ever cross over into the black hole's darkness, you're reduced to ash.

But before we plan your funeral, let's forget about Anne and view this gruesome scene from your point of view. Now, something even stranger happens: nothing.


The boundary of a black hole might be a blazing firewall (Credit: Equinox Graphics/SPL)

You sail straight into nature's most ominous destination without so much as a bump or a jiggle – and certainly no stretching, slowing or scalding radiation. That's because you're in freefall, and therefore you feel no gravity: something Einstein called his "happiest thought".

After all, the event horizon is not like a brick wall floating in space. It's an artefact of perspective. An observer who remains outside the black hole can't see through it, but that's not your problem. As far as you're concerned there is no horizon.

Sure, if the black hole were smaller you'd have a problem. The force of gravity would be much stronger at your feet than at your head, stretching you out like a piece of spaghetti. But lucky for you this is a big one, millions of times more massive than our Sun, so the forces that might spaghettify you are feeble enough to be ignored.

In fact, in a big enough black hole, you could live out the rest of your life pretty normally before dying at the singularity.


The event horizon is not a solid barrier (Credit: Richard Kail/SPL)

How normal could it really be, you might wonder, given that you're being sucked toward a rupture in the space-time continuum, pulled along against your will, unable to head back the other way?

But when you think about it, we all know that feeling, not from our experience with space but with time. Time only goes forwards, never backwards, and it pulls us along against our will, preventing us from turning around.

This isn't just an analogy. Black holes warp space and time to such an extreme that inside the black hole's horizon, space and time actually swap roles. In a sense, it really is time that pulls you in toward the singularity. You can't turn around and escape the black hole, any more than you can turn around and travel back to the past.

At this point you might want to stop and ask yourself a pressing question: What the hell is wrong with Anne? If you're chilling inside the black hole, surrounded by nothing weirder than empty space, why is she insisting that you've been burned to a crisp by radiation outside the horizon? Is she hallucinating?


"Hawking radiation" flows out of the event horizon (Credit: Richard Kail/SPL)

Actually, Anne is being perfectly reasonable. From her point of view, you really have been burned to a crisp at the horizon. It's not an illusion. She could even collect your ashes and send them back to your loved ones.

In fact, the laws of nature require that you remain outside the black hole as seen from Anne's perspective. That's because quantum physics demands that information can never be lost. Every bit of information that accounts for your existence has to stay on the outside of the horizon, lest Anne's laws of physics be broken.

On the other hand, the laws of physics also require that you sail through the horizon without encountering hot particles or anything out of the ordinary. Otherwise you'd be in violation of Einstein's happiest thought, and his theory of general relativity.

So the laws of physics require that you be both outside the black hole in a pile of ashes and inside the black hole alive and well. Last but not least, there's a third law of physics that says information can't be cloned. You have to be in two places, but there can only be one copy of you.

Somehow, the laws of physics point us towards a conclusion that seems rather nonsensical. Physicists call this infuriating conundrum the black hole information paradox. Luckily, in the 1990s they found a way to resolve it.


Once you fall in, there's no coming out (Credit: Science Photo Library)

Leonard Susskind realized that there is no paradox, because no one person ever sees your clone. Anne only sees one copy of you. You only see one copy of you. You and Anne can never compare notes. And there's no third observer who can see both inside and outside a black hole simultaneously. So, no laws of physics are broken.

Unless, that is, you demand to know which story is really true. Are you really dead or are you really alive?

The great secret that black holes have revealed to us is that there is no really. Reality depends on whom you ask. There's Anne's really and there's your really. End of story.

Well, almost. In the summer of 2012, the physicists Ahmed Almheiri, Donald Marolf, Joe Polchinski and James Sully, collectively known as AMPS, devised a thought experiment that threatened to upend everything we thought we knew about black holes.


Nobody is sure what lies inside a black hole (Credit: Henning Dalhoff/SPL)

They realized that Susskind's solution hinged on the fact that any disagreement between you and Anne is mediated by the event horizon. It didn't matter if Anne saw the unlucky version of you scattered amongst the Hawking radiation, because the horizon prevented her from seeing the other version of you floating along inside the black hole.

But what if there was a way for her to find out what was on the other side of the horizon, without actually crossing it?

Ordinary relativity would say that's a no-no, but quantum mechanics makes the rules a little fuzzier. Anne might sneak a peek behind the horizon, using a little trick that Einstein called "spooky action-at-a-distance".

This happens when two sets of particles that are separated in space are mysteriously "entangled". They are part of a single, indivisible whole, so that the information needed to describe them can't be found in either set alone, but in the spooky links between them.


Widely-separated particles can be spookily "entangled" (Credit: Victor de Schwanberg/SPL)

The AMPS idea went something like this. Let's say Anne grabs hold of a bit of information near the horizon — call it A.

If her story is right, and you are a goner, scrambled amongst the Hawking radiation outside the black hole, then A must be entangled with another bit of information, B, which is also part of the hot cloud of radiation.

On the other hand, if your story is the true one, and you're alive and well on the other side of the event horizon, then A must be entangled with a different bit of information, C, which is somewhere inside the black hole.

Here's the kicker: each bit of information can only be entangled once. That means A can only be entangled with B or with C, not with both.


Black holes can pull material away from nearby stars (Credit: NASA/CXC/M. Weiss)

So Anne takes her bit, A, and puts it through her handy entanglement-decoding machine, which spits out an answer: either B or C.

If the answer turns out to be C, then your story wins, but the laws of quantum mechanics are broken. If A is entangled with C, which is deep inside the black hole, then that piece of information is lost to Anne forever. That breaks the quantum law that information can never be lost.

That leaves B. If Anne's decoding machine finds that A is entangled with B, then Anne wins, and general relativity loses. If A is entangled with B, then Anne's story is the one true story, which means you really wereburned to a crisp. Instead of sailing straight through the horizon, as relativity says you should, you hit a burning firewall.

So we're back where we started: what happens when you fall into a black hole? Do you glide right through and live a normal life, thanks to a reality that's strangely observer-dependent? Or do you approach the black hole's horizon only to collide with a deadly firewall?


Black holes distort passing light rays, causing "lensing" (Credit: Ute Kraus, CC by 2.5)

No one knows the answer, and it's become one of the most contentious questions in fundamental physics.

Physicists have spent more than a century trying to reconcile general relativity with quantum mechanics, knowing that eventually one or the other was going to have to give. The solution to the firewall paradox should tell us which, and point the way to an even deeper theory of the universe.

One clue might lie in Anne's decoding machine. Figuring out which other bit of information A is entangled with is an extraordinarily complicated problem. So physicists Daniel Harlow of Princeton University in New Jersey and Patrick Hayden, now at Stanford University in California, wondered how long it would take.

In 2013 they calculated that, even given the fastest computer that the laws of physics would allow, it would take Anne an extraordinarily long time to decode the entanglement. By the time she had an answer, the black hole would have long evaporated, disappearing from the universe and taking with it the threat of a deadly firewall.


Centaurus A has a black hole (Credit: ESO/WFI/MPIfR/APEX/A. Weiss/NASA/CXC/CfA/R. Kraft)

If that's the case, the sheer complexity of the problem could prevent Anne from ever figuring out which story is the real one. That would leave both stories simultaneously true, reality intriguingly observer-dependent, all the laws of physics intact, and no one in danger of running into an inexplicable wall of fire.

It also gives physicists something new to think about: the tantalizing connections between complex calculations (like the one Anne apparently can't do) and space-time. This may open the door to something deeper still.

That's the thing about black holes. They're not just annoying obstacles for space travellers. They're also theoretical laboratories that take the subtlest quirks in the laws of physics, then amplify them to such proportions that they can't be ignored.

If the true nature of reality lies hidden somewhere, the best place to look is a black hole. It's probably best to look from the outside, though: at least until they figure out this whole firewall thing. Or send Anne in. It's her turn already.

http://www.bbc.com/earth/(...)hole-would-clone-you



[ Bericht 0% gewijzigd door Kijkertje op 31-05-2015 18:11:00 ]

REALITY DOESN'T EXIST UNTIL WE MEASURE IT, QUANTUM EXPERIMENT CONFIRMS

Mind = blown.


FIONA MACDONALD 1 JUN 2015

Australian scientists have recreated a famous experiment and confirmed quantum physics's bizarre predictions about the nature of reality, by proving that reality doesn't actually exist until we measure it - at least, not on the very small scale.

That all sounds a little mind-meltingly complex, but the experiment poses a pretty simple question: if you have an object that can either act like a particle or a wave, at what point does that object 'decide'?

Our general logic would assume that the object is either wave-like or particle-like by its very nature, and our measurements will have nothing to do with the answer. But quantum theory predicts that the result all depends on how the object is measured at the end of its journey. And that's exactly what a team from the Australian National University has now found.

"It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it," lead researcher and physicist Andrew Truscott said in a press release.

Known as John Wheeler's delayed-choice thought experiment, the experiment was first proposed back in 1978 using light beams bounced by mirrors, but back then, the technology needed was pretty much impossible. Now, almost 40 years later, the Australian team has managed to recreate the experiment using helium atoms scattered by laser light.

"Quantum physics predictions about interference seem odd enough when applied to light, which seems more like a wave, but to have done the experiment with atoms, which are complicated things that have mass and interact with electric fields and so on, adds to the weirdness," said Roman Khakimov, a PhD student who worked on the experiment.

To successfully recreate the experiment, the team trapped a bunch of helium atoms in a suspended state known as a Bose-Einstein condensate, and then ejected them all until there was only a single atom left.

This chosen atom was then dropped through a pair of laser beams, which made a grating pattern that acted as a crossroads that would scatter the path of the atom, much like a solid grating would scatter light.

They then randomly added a second grating that recombined the paths, but only after the atom had already passed the first grating.

When this second grating was added, it led to constructive or destructive interference, which is what you'd expect if the atom had travelled both paths, like a wave would. But when the second grating was added, no interference was observed, as if the atom chose only one path.

The fact that this second grating was only added after the atom passed through the first crossroads suggests that the atom hadn't yet determined its nature before being measured a second time.

So if you believe that the atom did take a particular path or paths at the first crossroad, this means that a future measurement was affecting the atom's path, explained Truscott. "The atoms did not travel from A to B. It was only when they were measured at the end of the journey that their wave-like or particle-like behaviour was brought into existence," he said.

Although this all sounds incredibly weird, it's actually just a validation for the quantum theory that already governs the world of the very small. Using this theory, we've managed to develop things like LEDs, lasers and computer chips, but up until now, it's been hard to confirm that it actually works with a lovely, pure demonstration such as this one.

The full results have been published in Nature Physics.

http://www.sciencealert.c(...)-experiment-confirms

HOW WILL THE UNIVERSE END, AND COULD ANYTHING SURVIVE?

Science has outlined four ways that our universe could meet its doom. They're called the Big Freeze, the Big Crunch, the Big Change and the Big Rip

Don't panic, but our planet is doomed. It's just going to take a while. Roughly 6 billion years from now, the Earth will probably be vaporized when the dying Sun expands into a red giant and engulfs our planet.

But the Earth is just one planet in the solar system, the Sun is just one of hundreds of billions of stars in the galaxy, and there are hundreds of billions of galaxies in the observable universe. What's in store for all of that? How does the universe end?

The science is much less settled on how that will happen. We're not even sure if the universe will come to a firm, defined end, or just slowly tail off. Our best understanding of physics suggests there are several options for the universal apocalypse. It also offers some hints on how we might, just maybe, survive it.


Our universe has been expanding since it began (Credit: Chris Butler/SPL)


Our first clue to the end of the universe comes from thermodynamics, the study of heat. Thermodynamics is the wild-eyed street preacher of physics, bearing a cardboard placard with a simple warning: "THE HEAT DEATH IS COMING".

Despite the name, the heat death of the universe isn't a fiery inferno. Instead, it's the death of all differences in heat.

This may not sound scary, but the heat death is far worse than being burnt to a crisp. That's because nearly everything in everyday life requires some kind of temperature difference, either directly or indirectly.

For instance, your car runs because it's hotter inside its engine than outside. Your computer runs on electricity from the local power plant, which probably works by heating water and using that to power a turbine. And you run on food, which exists thanks to the enormous temperature difference between the Sun and the rest of the universe.


The universe will end in one of four ways (Credit: Carlos Clarivan/SPL)


However, once the universe reaches heat death, everything everywhere will be the same temperature. That means nothing interesting will ever happen again.

Every star will die, nearly all matter will decay, and eventually all that will be left is a sparse soup of particles and radiation. Even the energy of that soup will be sapped away over time by the expansion of the universe, leaving everything just a fraction of a degree above absolute zero.

In this "Big Freeze", the universe ends up uniformly cold, dead and empty.

After the development of thermodynamics in the early 1800s, heat death looked like the only possible way the universe could end. But 100 years ago, Albert Einstein's theory of general relativity suggested that the universe had a far more dramatic fate.


Galaxies like M74 are rushing away from us (Credit: Chris Butler/SPL)


General relativity says that matter and energy warp space and time. This relationship between space-time and matter-energy (stuff) — between the stage and the actors on it — extends to the entire universe. The stuff in the universe, according to Einstein, determines the ultimate fate of the universe itself.

The theory predicted that the universe as a whole must either be expanding or contracting. It could not stay the same size. Einstein realized this in 1917, and was so reluctant to believe it that he fudged his own theory.

Then in 1929, the American astronomer Edwin Hubble found hard evidence that the universe was expanding. Einstein changed his mind, calling his previous insistence on a static universe the "greatest blunder" of his career.

If the universe is expanding, it must once have been much smaller than it is now. This realization led to the Big Bang theory: the idea that the universe began as something incredibly small, and then expanded incredibly quickly. We can see the "afterglow" of the Big Bang even today, in the cosmic microwave background radiation – a constant stream of radio waves, coming from all directions in the sky.


The cosmic microwave background (Credit: ESA Planck Collaboration/SPL)


The fate of the universe, then, hinges on a very simple question: will the universe continue to expand, and how quickly?

For a universe containing normal "stuff", such as matter and light, the answer to this question depends on how much stuff there is. More stuff means more gravity, which pulls everything back together and slows the expansion.

As long as the amount of stuff doesn't go over a critical threshold, the universe will continue to expand forever, and eventually suffer heat death, freezing out.

But if there's too much stuff, the expansion of the universe will slow down and stop. Then the universe will begin to contract. A contracting universe will shrink smaller and smaller, getting hotter and denser, eventually ending in a fabulously compact inferno, a sort of reverse Big Bang known as the Big Crunch.


The universe might collapse on itself, in a "Big Crunch" (Credit: Mark Garlick/SPL)


For most of the 20th century, astrophysicists weren't sure which of these scenarios would play out. Would it be the Big Freeze or the Big Crunch? Ice or fire?

They tried to perform a cosmic census, adding up how much stuff there is in our universe. It turned out that we're strangely close to the critical threshold, leaving our fate uncertain.

That all changed at the end of the 20th century. In 1998, two competing teams of astrophysicists made an astonishing announcement: the expansion of the universe is speeding up.

Normal matter and energy can't make the universe behave this way. This was the first evidence of a fundamentally new kind of energy, dubbed "dark energy", which didn't behave like anything else in the cosmos.

Dark energy pulls the universe apart. We still don't understand what it is, but roughly 70% of the energy in the universe is dark energy, and that number is growing every day.


The Big Crunch would bring our universe to a fiery end (Credit: Mehau Kulyk/SPL)


The existence of dark energy means that the amount of stuff in the universe doesn't get to determine its ultimate fate.

Instead, dark energy controls the cosmos, accelerating the expansion of the universe for all time. This makes the Big Crunch much less likely.

But that doesn't mean that the Big Freeze is inevitable. There are other possibilities.

One of them originated, not in the study of the cosmos, but in the world of subatomic particles. This is perhaps the strangest fate for the universe. It sounds like something out of science fiction, and in a way, it is.


Water can sometimes stay liquid below its freezing point (Credit: Tomas Sobek, CC by 2.0)


In Kurt Vonnegut's classic sci-fi novel Cat's Cradle, ice-nine is a new form of water ice with a remarkable property: it freezes at 46 °C, not at 0 °C. When a crystal of ice-nine is dropped into a glass of water, all the water around it immediately patterns itself after the crystal, since it has lower energy than liquid water.

The new crystals of ice-nine do the same thing to the water around them, and in the blink of an eye, the chain reaction turns all the water in the glass — or (spoiler alert!) all of Earth's oceans — into solid ice-nine.

The same thing can happen in real life with normal ice and normal water. If you put very pure water into a very clean glass, and cool it just below 0°C, the water will become supercooled: it stays liquid below its natural freezing point. There are no impurities in the water and no rough patches on the glass, so there's nowhere for the ice to start forming. But if you drop a crystal of ice into the glass, the water will freeze rapidly, just like ice-nine.

Ice-nine and supercooled water may not seem relevant to the fate of the universe. But something similar could happen to space itself.


Empty vacuum could suddenly drop to a lower energy level (Credit: Richard Kail/SPL)


Quantum physics dictates that even in a totally empty vacuum, there is a small amount of energy. But there might also be some other kind of vacuum, which holds less energy.

If that's true, then the entire universe is like a glass of supercooled water. It will only last until a "bubble" of lower-energy vacuum shows up.

Fortunately, there are no such bubbles that we're aware of. Unfortunately, quantum physics also dictates that if a lower-energy vacuum is possible, then a bubble of that vacuum will inevitably dart into existence somewhere in the universe.

When that happens, just like ice-nine, the new vacuum will "convert" the old vacuum around it. The bubble would expand at nearly the speed of light, so we'd never see it coming.


Even completely empty space contains energy (Credit: Equinox Graphics/SPL)


Inside the bubble, things would be radically different, and not terribly hospitable.

The properties of fundamental particles like electrons and quarks could be entirely different, radically rewriting the rules of chemistry and perhaps preventing atoms from forming.

Humans, planets and even the stars themselves would be destroyed in this Big Change. In a 1980 paper, Physicists Sidney Coleman and Frank de Luccia called it "the ultimate ecological catastrophe".

Adding insult to injury, dark energy would probably behave differently after the Big Change. Rather than driving the universe to expand faster, dark energy might instead pull the universe in on itself, collapsing into a Big Crunch.


Phantom dark energy could destroy everything (Credit: Detlev van Ravenswaay/SPL)


There is a fourth possibility, and once again dark energy is at centre stage. This idea is very speculative and unlikely, but it can't yet be ruled out. Dark energy might be even more powerful than we thought, and might be enough to end the universe on its own, without any intervening Big Change, Freeze, or Crunch.

Dark energy has a peculiar property. As the universe expands, its density remains constant. That means more of it pops into existence over time, to keep pace with the increasing volume of the universe. This is unusual, but doesn't break any laws of physics.

However, it could get weirder. What if the density of dark energy increases as the universe expands? In other words, what if the amount of dark energy in the universe increases more quickly than the expansion of the universe itself?

This idea was put forward by Robert Caldwell of Dartmouth College in Hanover, New Hampshire. He calls it "phantom dark energy". It leads to a remarkably strange fate for the universe.


The Big Rip would begin by tearing galaxies apart (Credit: Detlev van Ravenswaay/SPL)


If phantom dark energy exists, then the dark side is our ultimate downfall, just like Star Wars warned us it would be.

Right now, the density of dark energy is very low, far less than the density of matter here on Earth, or even the density of the Milky Way galaxy, which is much less dense than Earth. But as time goes on, the density of phantom dark energy would build up, and tear the universe apart.

In a 2003 paper, Caldwell and his colleagues outlined a scenario they called "cosmic doomsday". Once the phantom dark energy becomes more dense than a particular object, that object gets torn to shreds.

First, phantom dark energy would pull the Milky Way apart, sending its constituent stars flying. Then the solar system would be unbound, because the pull of dark energy would be stronger than the pull of the Sun on the Earth.

Finally, in a few frantic minutes the Earth would explode. Then atoms themselves would shatter, a fraction of a second before the universe itself ripped apart. Caldwell calls this the Big Rip.


The Big Rip would literally tear planets and stars apart (Credit: Nicolle R. Fuller/SPL)


The Big Rip is, by Caldwell's own admission, "very outlandish" – and not just because it sounds like something out of an over-the-top superhero comic.

Phantom dark energy flies in the face of some fairly basic ideas about the universe, like the assumption that matter and energy can't go faster than the speed of light. There are good reasons not to believe in it.

Based on our observations of the expansion of the universe, and particle physics experiments, it seems much more likely that the ultimate fate of our universe is a Big Freeze, possibly followed by a Big Change and a final Big Crunch.

But this is a remarkably grim portrait of the future — aeons of cold emptiness, finally terminated by a vacuum decay and a final implosion into nothingness. Is there any escape? Or are we doomed to book a table at the Restaurant at the End of the Universe?


All this shall pass, but not for a very long time (Credit: Allan Morton/Dennis/Milon/SPL)


There's certainly no reason for us, individually, to worry about the end of the universe. All of these events are trillions of years into the future, with the possible exception of the Big Change, so they're not exactly an imminent problem.

Also, there's no reason to worry about humanity. If nothing else, genetic drift will have rendered our descendants unrecognizable long before then. But could intelligent feeling creatures of any kind, human or not, survive?

Physicist Freeman Dyson of the Institute for Advanced Studies in Princeton, New Jersey considered this question in a classic paper published in 1979. At the time, he concluded that life could modify itself to survive the Big Freeze, which he thought was less challenging than the inferno of the Big Crunch.

But these days, he's much less optimistic, thanks to the discovery of dark energy.

"If the universe is accelerating, that's really bad news," says Dyson. Accelerating expansion means we'll eventually lose contact with all but a handful of galaxies, dramatically limiting the amount of energy available to us. "It's a rather dismal situation in the long run."

The situation could still change. "We really don't know whether the expansion is going to continue since we don't understand why it's accelerating," says Dyson. "The optimistic view is that the acceleration will slow down as the universe gets bigger." If that happens, "the future is much more promising."

But what if the expansion doesn't slow down, or if it becomes clear that the Big Change is coming? Some physicists have proposed a solution that is solidly in mad-scientist territory. To escape the end of the universe, we should build our own universe in a laboratory, and jump in.


Just after it was born, the universe inflated rapidly (Credit: David Parker/SPL)


One physicist who has worked on this idea is Alan Guth of MIT in Cambridge, Massachusetts, who is known for his work on the very early universe.

"I can't say that the laws of physics absolutely imply that it's possible," says Guth. "If it is possible, it would require technology vastly beyond anything that we can foresee. It would require huge amounts of energy that one would need to be able to obtain and control."

The first step, according to Guth, would be creating an incredibly dense form of matter — so dense that it was on the verge of collapsing into a black hole. By doing that in the right way, and then quickly clearing the matter out of the area, you might be able to force that region of space to start expanding rapidly.

In effect, you would jump-start the creation of an entirely new universe. As the space in the region expanded, the boundary would shrink, creating a bubble of warped space where the inside was bigger than the outside.


The Big Bang: the birth of a universe (Credit: Detlev van Ravenswaay/SPL)


That may sound familiar to Doctor Who fans, and according to Guth, the TARDIS is "probably a very accurate analogy" for the kind of warping of space he's talking about.

Eventually, the outside would shrink to nothingness, and the new baby universe would pinch off from our own, spared from whatever fate our universe may meet.

It's far from certain that this scheme would actually work. "I would have to say that it's unclear," says Guth. "We don't really know if it's possible or not."

However, Guth also points out that there is another source of hope beyond the end of the universe – well, hope of a sort.


Other universe may be appearing all the time (Credit: Detlev van Ravenswaay/SPL)


Guth was the first to propose that the very early universe expanded astonishingly fast for a tiny fraction of a second, an idea known as "inflation". Many cosmologists now believe inflation is the most promising approach for explaining the early universe, and Guth's plan for creating a new universe relies on recreating this rapid expansion.

Inflation has an intriguing consequence for the ultimate fate of the universe. The theory dictates that the universe we inhabit is just one small part of a multiverse, with an eternally inflating background continually spawning "pocket universes" like our own.

"If that's the case, even if we're convinced that an individual pocket universe will ultimately die through refrigeration, the multiverse as a whole will go on living forever, with new life being created in each pocket universe as it's created," says Guth. "In this picture, the multiverse as a whole is genuinely eternal, at least eternal into the future, even as individual pocket universes live and die."

In other words, Franz Kafka may have been right on the money when he said that there is "plenty of hope, an infinite amount of hope—but not for us."

This is a bit of a bleak thought. If it upsets you, here is a picture of a cute kitten.


Cheer up, by the time it happens we'll all be long gone (Credit: Alan Huett, CC by 2.0)


http://www.bbc.com/earth/story/20150602-how-will-the-universe-end