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What is dark matter? A deep dive

If you’ve been following our space articles, you may have come across something called “dark matter”. It’s the most abundant type of matter in the universe — our best models have established that dark matter comprises 84.4% of the matter contained in the known universe — but we still don’t really understand just what it is. Dark matter is something that we know is out there, but we have little idea what it’s made of.

Credit: News-G.

Wait, so how do we know it’s even real?

“Regular” matter (technically called baryonic matter) is made of electrons, protons, and neutrons. Cosmologists define the three particles as baryons –technically speaking, electrons are something else, but that’s beside the point here. Baryons make up gas, gas makes up stars, stars go boom and make planets and other things — including you. Yes, you are made of star stuff — baryonic star stuff, to be precise.

All this is done thanks to the electromagnetic (EM) force that forms chemical bonds, glueing regular atoms together But Dark Matter (DM) plays a different game.

Dark matter doesn’t interact with things the way baryonic matter does. It doesn’t scatter or absorb light, but it still has a gravitational pull. So if there are beings made of dark matter living right here, right now, you probably wouldn’t even know it because the perception of touch is felt when your sensory nerves send the message to your brain, and these nerves work thanks to the EM force.

We can’t touch dark matter, and no optical instruments can detect, so how do we ‘see’ it? Indirectly, for starters. Look for gravity, if there isn’t enough visible mass to explain to explain the gravitational pull felt by a region of the universe, then there something there. Invisible does not mean non-existant. If it weren’t for its gravity effect, there would be little indication of dark matter existing.

The main observational evidence for dark matter is the orbital speeds of stars in the arms of spiral galaxies. If Kepler and Newton were correct, stars’ velocity would decrease with the orbital radius in a specific way. But this was not observed by Vera Rubin and Kent Ford, who tracked this relationship. Instead, Rubin and Ford got a velocity vs radius relation that looked like the stars had a nearly constant behavior from a certain point of the galactic orbit.

This could only be explained if there would be a lot more matter somewhere that we’re not seeing. Something was pulling at these stars gravitationally, and that something is dark matter.

Rotation curve of a typical spiral galaxy: predicted (A) and observed (B). Dark matter can explain the ‘flat’ appearance of the velocity curve out to a large radius. Credits: Phil Hibbs.

Another important evidence of dark matter comes from galaxy superclusters like 1E 0657-558. Astronomers observed that within this cluster, there are two groups of galaxies placed in a peculiar position to one another. 

If you look at the Hubble Space Telescope image below (1st and 2nd), you’ll notice that there are many galaxies on the left and another group on the opposite side. When astronomers observed in X-ray, they concluded that these two clusters collided and left a gas trace of the shock. The faster cluster was like a bullet (it’s even named the Bullet Cluster) passing through the slower one at around 3000–4000 km/s nearly 100-200 million years ago (3rd pic).

Visible light image from the Hubble Space Telescope, NASA, ESA and the Magellan Telescope, University of Arizona
Visible light image from the Hubble Space Telescope, NASA, ESA and the Magellan Telescope, University of Arizona
X-ray light image from the Chandra X-ray Observatory: NASA, CXC

But one of the most convincing evidence of dark matter came with gravitational lensing.

Scientists used gravitational lensing to estimate the mass of the objects involved in the collision. They found that the galaxies which hadn’t collided agreed with the weak lensing detections. This indicates those galaxies are ahead of ‘the X-ray evidence’ (below, 1st image). Since dark matter doesn’t interact with nearly anything, in this phenomenon, we see a bunch of mass (blue) moving faster than the gas (purple), barely affecting the baryonic matter (2nd image).

Dark matter map: NASA, STScI; ESO; University Arizona
Composite image (visible, dark matter map, X-ray): NASA, ESA, ESO, University Arizona

So what is Dark Matter?

Just because we don’t know what dark matter is doesn’t mean we have no idea. In fact, researchers have a few theories and are considering several plausible candidates.

There are three ways to classify dark matter. Cold dark matter describes the formation of the large-scale structure of the universe and is the fundamental component of the matter in the universe. It’s called cold because it moves ‘slowly’ compared to the speed of light.

Weakly interacting massive particles (WIMPs) are the candidates for cold dark matter particles. They supposedly interact via weak nuclear force. The particles which belong to this group are thought to be the lightest particles of the supersymmetric theories. Neutral examples of these particles could have been produced in the early universe, and later participated in the formation of galaxy clusters.

Hot dark matter is the opposite, it moves close to the speed of light. The warm candidate particles are thought to be less interactive than neutrinos.

Another candidate particle for dark matter is the sterile neutrino — a hypothetical particle that interacts only via gravity and not via any of the other fundamental forces. These would be responsible for forming warm dark matter. They also seem to be heavier than the standard neutrino, and have a longer lifetime before they break down.

Neutrinos were thought to be the best candidates for dark matter. Neutrinos are weird particles — they barely interact with things, and even then only gravitationally (which is a weak interaction). Besides, they do not possess electrical charge, which is why they do not interact electromagnetically. However, the neutrino temperature is high and they decouple (stop interacting with other forms of matter) only at relativistic velocities. If dark matter was made of neutrinos, the universe would have looked radically different.

Massive Compact Halo Objects (MACHOs) represent a different type of candidate. They’re no WIMPs at least. They aren’t particles either, but rather brown dwarfs, planets like Jupiter, black holes in galactic haloes. The best possible MACHOs are primordial black holes( PBHs). Different from the ordinary black holes we see in the center of galaxies, PBHs are thought to have been created nearly 10 seconds after the Big Bang. No evidence for such objects has yet been discovered, but it’s still an open possibility.

Detecting dark matter

Many ideas for the detection of each plausible candidate have been developed.

Through cosmology, the main evidence comes from the Cosmic Microwave Background (CMB).  Yes, the same radiation Dr. Darcy Lewis detected (for real) in the TV miniseries WandaVision. It is the remnant electromagnetic radiation from when the universe was a 380,000-year-old baby.

The best CMB observations we have currently are from the Planck satellite 2018 survey. Different amounts of matter have distinct signals in the CMB observations, forming the temperature power spectrum.

Four Possible Models of the Universe. The yellow square marks the present in all four cases, and for all four, the Hubble constant is equal to the same value at the present time. Time is measured in the vertical direction. The first two universes on the left are ones in which the rate of expansion slows over time. The one on the left will eventually slow, come to a stop and reverse, ending up in a “big crunch,” while the one next to it will continue to expand forever, but ever-more slowly as time passes. The “coasting” universe is one that expands at a constant rate given by the Hubble constant throughout all of the cosmic time. The accelerating universe on the right will continue to expand faster and faster forever. Credits: Physics LibreTexts.

If the theory is correct, the shape of the power spectrum is different for different amounts of matter. There’s such a thing known as the critical density of the universe, which describes the density of the universe if it was coasting, expanding but not accelerating, and if it stopped its expansion. When you divide the density of the observable matter by the critical density, you get its density parameter (Ω).

The temperature power spectrum is modeled according to the different amounts of ingredients in the universe, more matter or less matter changes its shape. Planck’s observations have shown that the matter density parameter is Ω h² ~0.14, so if the shape of the graph corresponds to that value we have evidence of the amount of dark matter in the universe.

Temperature power spectrum for different matter densities. Credits: Wayne Hu.

There are also ways to detect dark matter directly, not through cosmology but through particle physics. The Large Hadron Collider (LHC) is the most powerful particle accelerator, can collide protons at extremely high (relativistic) speeds, generating a bunch of scattered particles that are then measured by the detectors.

Physicists hope to find dark matter by comparing the energy before and after the collision. Since the dark matter particles are elusive, the missing energy could explain their presence. However, no experiment has observed dark matter so far — though researchers are still looking.

Another underground experiment uses high purity sodium iodide crystals as detectors. The detectors at DAMA/LIBRA (Large sodium Iodide Bulk for RAre processes), for example, try to observe an annual variation of regular matter colliding with WIMPs due to the planet’s motion around the Sun which means we’re changing our velocity relative to the galactic dark matter halo. The problem is that DAMA’s 20 years’ worth of data didn’t have enough statistical significance. However, in an identical experiment meant to directly detect dark matter, called ANAIS (Annual modulation with NaI Scintillators), in 3 years scientists gathered more reliable data indicating this method is not conducive to finding dark matter anytime soon. 

To get a better picture of the challenge in having a conclusive result, take a look at the image below. All those lines and colorful contours represent the results of different experiments, none of them seem to agree. That’s the problem with dark matter, we still don’t have the evidence to match any theory we came up with — and we can’t really rule out any possibilities either.

WIMP discovery limit (thick dashed orange) compared with current limits
and regions of interest. Credits: J. Billard and E. Figueroa-Feliciano.

The questions of what dark matter is and how it works still have no satisfying answer. There are many detection experiments being planned and conducted in order to explain and verify different hypotheses, but nothing conclusive thus far. Let’s hope we don’t have to wait another 20 years to figure out if one experiment is right or wrong. Unfortunately, groundbreaking discoveries can take a lot of time, especially in astrophysics. While we wait, dark matter will continue to entertain our imagination.

The article was primarily based on the 2020 Review of Particle Physics from Particle Data Group’s Dark Matter category.

The tale of physics’ most famous cat is one that is familiar to many, but what is the inside story of the feline so demanding it requires its own Universe, and how does it illustrate the 'weirdness' of the quantum world?

Superposition! The strange tale of Schrödinger’s cat

The tale of physics’ most famous cat is one that is familiar to many, but what is the inside story of the feline so demanding it requires its own Universe, and how does it illustrate the 'weirdness' of the quantum world?
The tale of physics’ most famous cat is one that is familiar to many, but what is the inside story of the feline so demanding it requires its own Universe, and how does it illustrate the ‘weirdness’ of the quantum world? (Robert Lea)

Of all the counter-intuitive elements of quantum physics introduced to the public since its inception in the early days of the twentieth century, it is quite possible that the idea that a system can be two (or more) contradictory things at once, could be the most challenging.

As well as defying a well-known aspect of logic — the law of non-contradiction — thus irritating logisticians, this idea of the coexistence of states, or superposition, was even a challenge to the fathers of quantum physics. Chief amongst them Erwin Schrödinger, who suggested a diabolical thought experiment that would show what he believed to the ludicrous nature of a system existing in contradictory states. 

The thought experiment would go on to become perhaps the most well-known in the history of physics, weaving its way on to witty t-shirts, hats, bags and badges, infiltrating pop-culture, TV and film. This is the strange tale of Schrödinger’s cat, and what it can teach us about quantum physics and the nature of reality itself. 

Before delving into the experiment that Schrödinger devised, it is worth examining the circumstances that led him to consider the absurd situation of a cat that is both living and dead at the same time. 

Wanted: Dead or Alive! How the cat got put in the box

In many ways, Erwin Schrödinger’s place in the history of quantum mechanics is overshadowed by his feline-based thought experiment. The Austrian physicist was responsible for laying the foundation of a theoretical understanding of quantum physics with the introduction of his eponymous wave equation in 1926. As Joy Manners describes in the book ‘Quantum Physics: An Introduction’:

“The Schrödinger equation did for quantum mechanics what Newton’s laws of motion had done for classical mechanics 250 years before.”

Joy Manners, Quantum Physics: An Introduction

What Schrödinger’s equation shows is that the state of a system — the collection of all of its measurable qualities — can be described as a wavefunction — represented by the Greek letter Psi (Ψ). This wavefunction contains all the information of a system that it is possible to hold. Each wavefunction is a solution to Schrödinger’s equation, but here’s the crazy part; two wavefunctions can be combined to form a third, and this resultant wavefunction can contain completely contradictory information.

When the wavefunctions of a system are combined it is in a ‘superposition’ state. There is also no limit no how many of these wavefunctions cam be combined to form a superposition. 

Yet, infinite though a wavefunction can be, eternal it is not. The act of taking a measurement on the system in question seems to cause the wavefunction to collapse — something there is as yet no physical or mathematical description for. There are, however, interpretations of what happens, which go to the very heart of reality.

Before tackling these interpretations, first, we should get to our cat in the box before he gets too impatient. 

A most diabolical device 

It was in 1935, whilst living in Oxford fleeing the rise of the Nazis, that Schrödinger first published an article that expressed his concern with the idea of measurement, wave function collapse, and contradictory states in quantum mechanics. Little would he know, it would lead to him becoming history’s most infamous theoretical-cat-assassin. 

A common illustration of the Schrodinger’s Cat thought experiment (Dhatfield / CCbySA 3.0)

Below Schrödinger describes the terrible predicament that his unfortunate moggy finds himself in. 

“A cat is placed in a steel chamber with the following hellish contraption… In a Gieger counter a tiny amount of a radioactive substance, so that maybe within an hour one of the atoms decays, but equally probable is that no atom decays…”

So, there is a 1/2 chance that an atom of the substances decays and causes the Gieger to tick over the hour duration of the experiment. 

“If one decays the counter triggers a little hammer which breaks a container of cyanide.” 

So, if the atom decays over the hour, the cat is killed. If it doesn’t, the cat survives. Treating the box and the cat as a quantum system how would we describe its wavefunction (Ψ)?

The wavefunction of the system now exists in a superposition of the individual wavefunction that describes the cat as being alive, and the one that declares it dead. According to the rules of quantum physics, the cat is currently both dead and alive.

Our unfortunate feline isn’t doomed to live out its existence as some bizarre quantum zombie, though. A quick peek inside the box constitutes a measurement of the system. Thus, by opening the box we collapse the wavefunction and determine the fate of Schrödinger’s cat. It really is curiosity that kills the cat, in this case.

Let’s end our analogy on a happy note. We open our box and fortunately the substance has not undergone decay. The cyanide bottle remains intact. Our moggy survives, unscathed if irritated. The wavefunction collapsed leaving the blue sub-wavefunction intact, but what actually just happened here? How was the cat’s fate determined? 

The short answer is, we don’t know, but we have some interpretations. Next, we compare the two most prominent. 

Way more than nine lives. The many-worlds interpretation 

What we have discussed thus far consists of a very rough description of the Copenhagen interpretation of quantum mechanics. The reason it’s common sense to present this first is that it is generally the interpretation that is most widely accepted and taught.

As you’ve seen, the Copenhagen interpretation describes a system with no established values until a measurement occurs or is taken and a value — in our case ‘alive’ — emerges. If this sounds deeply unsatisfactory, well, it is. One of the questions it leaves open is ‘why does the wavefunction collapse?’

In 1957, an American physicist Hugh Everett III, asked a different question: ‘What if the wavefunction doesn’t collapse at all? What if it grows?’ From this emerged Everett’s ‘relative state formulation’, better known to fans of science fiction, comic books and fantasy as the ‘Many Worlds Hypothesis/interpretation’.

Below we see what happens to the wavefunction in the Copenhagen interpretation. The box is opened and the wavefunction collapses. 

So what happens in the ‘many worlds’ interpretation? Rather than collapsing, as the box is opened the wavefunction expands. The cat does not cease to be in a superposition, but that superposition now includes the researchers and the very universe they inhabit. We become part of the system.

In the many-worlds interpretation, the researchers do not open the box to discover if the cat is dead or alive, they open the box to see if they are in the universe where the cat survived or the universe in which it was dispatched. They and their world have become part of the wavefunction. An entirely new universe in superposition with the old. The only difference. 

One less cat.

Schrodinger’s Kittens: Some words of caution

Again, as with the Copenhagen interpretation, there is no real experimental evidence of many worlds concept. In many ways, any interpretation of quantum mechanics is really more a realm of philosophy than science. Also, when considering ‘many worlds’ it’s worth noting that this is a different concept than the idea of a ‘multiverse’ of different universes created at the beginning of time. 

Further to this, there are some real problems with considering the ‘cat in a box’ as a quantum system. Researchers are constantly finding quantum effects in larger and larger systems, the current record seems to be 2,000 atoms placed in a superposition. To put that into perspective; a humble cat treat contains around 10²² atoms!

Many physicists have suggested reasons why larger systems fail to display quantum effects, with Roger Penrose suggesting that any system that has enough mass to affect space-time via Einstein’s theory of general relativity can’t be isolated. Via the influence of gravity, it is constantly having ‘measurements’ taken. This would definitely apply to even the most minuscule moggy. 

It is worth noting here that the general description of the thought experiment and the opening of the box has led some to speculate that it is the addition of a ‘consciousness’ that actually causes the wavefunction collapse. 

This is an idea that has sold a million or so books on ‘quantum woo’ and it arises from the unfortunate nomenclature of quantum physics. The use of the words ‘measure’ and ‘observe’ imply the intervention of a conscious observer. The truth is that any interaction with another system is enough to collapse a quantum wavefunction, as they tend to exist in incredibly delicate, easily disturbed states. 

Sources and further reading

Schrödinger. E,

Griffiths. D. J, ‘Introduction to Quantum Mechanics,’ [2017], Cambridge University Press.

Broadhurst. D, Capper. D, Dubin. D, et al, ‘Quantum Physics: An Introduction,’ [2008], Open University Press.

Nomura. Y, Poirer. B, Terning. J, ‘Quantum Physics, Mini Black Holes, and the Multiverse,’

Orzel. C, ‘How to Teach Quantum Physics to your Dog,’ [2009], Simon & Schuster. 

A 2-D layer of chromium triiodide atoms -- the first single-sheet magnet in the world. Credit: Efrén Navarro Moratalla.

Presenting the first 2D magnet: it will allow scientists to make previously impossible experiments

Two decades ago, the notion of actually working in applied science with 2D materials was seen as a pipedream. But that all changed after graphene was first forged in Manchester, UK, in 2004. Since then, scientists have demonstrated one-atom-thick semiconductors, insulators, even superconductors. Now, a pair of talented physicists has completed the spectrum by adding magnets to the 2D family.

A 2-D layer of chromium triiodide atoms -- the first single-sheet magnet in the world. Credit: Efrén Navarro Moratalla.

A 2-D layer of chromium triiodide atoms — the first single-sheet magnet in the world. Credit: Efrén Navarro Moratalla.

Up until this breakthrough study, scientists weren’t sure a 2D magnet was even possible. Here we are, though.

The discovery could ultimately lead to novel storage devices that work fundamentally different. Quantum computers might also benefit from this. Most of all, however, scientists working in fundamental physics will have their work cut out for them many years ahead as they now have the chance to perform experiments previously thought impossible.  “It’s a matter of principle — there is a big thing missing,” Jarillo-Herrero told Nature.

Previously, the thinnest magnets were demonstrated by a group of Chinese researchers who worked with a crystal made of chromium, germanium, and tellurium. However, when the crystal was stripped to a single-atom layer, it lost its magnetic properties so not a real 2D magnet at all.

To build one, Xu and Jarilo-Herrero literally stripped a chromium triiodide (Crl3) crystal until all was left was a single-atom-thick layer. The reason why they choose this material was that it’s made of stacked sheets that can be separated easily using the so-called “Scotch tape method”, which literally means using adhesive tape to peel off layers off the larger, 3-D crystal form. The technique has been used to make graphene for some time. Secondly, chromium triiodide is ferromagnet (permanent magnet) and is also anisotropic, meaning it has physical properties which vary when measured in different directions. In our case, the material’s electrons spin perpendicular to the plane of the crystal. These were very good hints that suggested chromium triiodide could work as a 2D magnet.

By this point, it’s maybe important to mention what 2D actually means. It’s not the same as in, say, math where 2D means a completely flat plane. After all, this material is made of atoms and an atom is essentially 3D. Functionally, however, the atoms within the monolayer material are considered 2D because the electrons are confined to the atomic sheet, like pieces on a chessboard.

Layer by layer, the two physicists stripped chromium triiodide until it became 2D and low and behold it was magnetic. Moreover, this property arises at a relatively low temperature when working in the atomic domain: -228 degrees Celsius.

Top-view depiction of a CrI3 lattice. Cr atoms are in grey, I atoms are in purple. Credit: Efren Navarro-Moratalla.

Top-view depiction of a CrI3 lattice. Cr atoms are in grey, I atoms are in purple. Credit: Efren Navarro-Moratalla.

Another interesting quirk was that when the material was comprised of two-layered sheets, it stopped being magnetic. They tested it by shining polarized light on the material, which returns a distinct signature in response to ferromagnetism. Adding another third sheet turned the material back into a ferromagnet and remained ferromagnetic when the fourth layer was added as well. The researchers are still investing why.

“2D monolayers alone offer exciting opportunities to study the drastic and precise electrical control of magnetic properties, which has been a challenge to realize using their 3D bulk crystals,” says Xiaodong Xu, lead author of the study, in a statement. “But an even greater opportunity can arise when you stack monolayers with different physical properties together. There, you can get even more exotic phenomena not seen in the monolayer alone or in the 3D bulk crystal.”

This is the culmination of more than five decades worth of searching for an ultrathin magnet. We now got more than anyone bargained for: a 2D magnet. But to be really useful, physicists would like to find a 2D ferromagnet that works at room temperature and ambient conditions, like in the presence of oxygen for instance. Jarillo-Herrero and Xu are currently exploring other magnets in chromium triiodide’s chemical family for clues.

Meanwhile, they also want to layer this 2D magnet with a 2D superconductor to see what happens.

“Does the superconductor destroy the ferromagnet, or does the ferromagnet destroy the superconductor?” Jarillo-Herrero told Nature. “It was just not possible to do this experiment before.”

“Heterostructures hold the greatest promise of realizing new applications in computing, database storage, communications and other applications we cannot even fathom yet,” said Xu.

The findings were reported in the journal Nature.

Astronomers come back from a year on Mars… in Hawaii

NASA’s year-long Mars simulation experiment has concluded today as six scientists emerged after spending 365 days in a geodesic dome set in a Mars-like environment 8,200 feet (2,500 meters) above sea level, on the slopes of the Mauna Loa volcano in Hawaii.

The HI-SEAS crew members exited their Mars simulation habitat on August 28, 2016. Image via NASA.

Exactly one year ago an astrobiologist, a physicist, a pilot, an architect, a journalist, and a soil scientist signed on to one of the longest experiments of this type. The mission was designed to test crew cohesion and performance in isolation, a key component of any long-term space mission.

Before any ground mission on Mars can actually start, the potential pioneers will have to undertake a 6-month long journey. That’s half a year you spend in a cramped-up space with several people before any actual work begins and as you can imagine, that can be very difficult psychologically. Inter-human relationships in this environment are something which needs to be carefully planned and understood before any such endeavor is undertaken, and this is exactly what this kind of experiment is supposed to do.

NASA teamed up with the University of Hawaii (UH) to set up a claustrophobic, geodesic dome, more than 2 km above sea level. The NASA-funded project is called HI-SEAS (Hawaii Space Exploration Analog and Simulation), and it tested the effects of isolation on crewmembers.

The participants involved truly were isolated. For one year, they lived just as if they were on Mars. They would only communicate to the outside world via email, and all communications were delayed by 20 minutes to mimic the communication lag between Earth and Mars. They chose the slopes of the Mauna Loa volcano because it is red and barren, similar in a way to the Martian environment.

“The UH research going on up here is just super vital when it comes to picking crews, figuring out how people are going to actually work on different kinds of missions, and sort of the human factors element of space travel, colonization, whatever it is you are actually looking at,” Tristan Bassingthwaighte, who served as the crew’s architect, said in a statement.
“We’re proud to be helping NASA reduce or remove the barriers to long-duration space exploration,” said University of Hawaii professor Kim Binsted, the project’s principle investigator.

Crew members of the fourth Hawaiʻi Space Exploration Analog and Simulation mission before they entered their Mars simulation habitat on August 28, 2015. Image via University of Hawaii.

Crew members of the fourth Hawaiʻi Space Exploration Analog and Simulation mission before they entered their Mars simulation habitat on August 28, 2015. Image via University of Hawaii.

Dealing with the mental aspects is just as important as dealing with the technological challenges of such a mission. A similar experiment has also been conducted by the European Space Agency, in Concordia, Antarctica, and in Moscow, where participants warned of sleep issues, as well as psychological problems. But the participants from Hawaii seem more optimistic.

“I think the technological and psychological obstacles can be overcome,” Cyprien Verseux said after emerging from the Hawaiian Mars.

A mission to Mars seems more likely than ever, and NASA is taking concrete steps towards this goal.

“I can give you my personal impression which is that a mission to Mars in the close future is realistic. I think the techonological and psychological obstacles can be overcome,” said Cyprien Verseux, a French HI-SEAS crewmember.

Experiment made people feel like they’re invisible

We’ve all had days when we’ve felt invisible metaphorically, but Swedish researchers have taken it to the next level – they’ve made a man actually feel like he’s invisible.

Image via KJN Genealogy.

The experiment, which was conducted on 125 participants, was a variation of the so-called rubber hand illusion – a popular trick which actually holds a lot of insight on how the human brain works. In the rubber hand illusion, you sit with your real hand under a table and out of sight, while a rubber hand sits in front of you. The experimenter strokes the fake hand in time with your real one, and you only get to see the fake one, so you sort of believe that one is yours – sort of like a phantom hand. Henrik Ehrsson from the Karolinska Institute is a master of this illusion, and he wanted to see how far the trick can be taken.

In this new setup, participants wore a virtual reality headset, linked to a nearby downward-pointed camera. A researcher stood at arm’s length from the subject, with a paintbrush in each hand. With one hand, he was actually stroking the participant, while with the other one, he made a similar motion onto what the participant perceived to be his or her invisible body. To make the entire thing more interesting, experimenters had an audience of “seriously looking strangers” assist the entire thing. When the brush motions weren’t synced up, the subjects maintained their sense of self. But when they were, subjects reportedly felt like they actually were the empty space – in other words, they felt invisible.

“Within less than a minute, the majority of the participants started to transfer the sensation of touch to the portion of empty space where they saw the paintbrush move and experienced an invisible body in that position,” explained Arvid Guterstam, lead author from the Karolinska Institutet in Sweden. “The present study demonstrates that the ‘invisible hand illusion’ can, surprisingly, be extended to an entire invisible body,” he noted.

To actually prove that participants felt like they were the invisible space next to them, experimenters made a stabbing motion with a knife, towards the empty space. When the illusion was up, participants were scared and exhibited increased sweat response (in some cases, even a visible reaction).

But this isn’t just a cool experiment to make people feel like they’re invisible, it may have significant implications in terms of understanding and dealing with anxiety. As scientists explain, when people felt invisible, it actually made them significantly less anxious.

“We found that their heart rate and self-reported stress level during the ‘performance’ was lower when they experienced the invisible body illusion,” Guterstam noted.

They’re also interested in studying what feeling invisible does to participants’ sense of morality. If the internet is some sort of indication, feeling invisible will make people bring out the worse in them, but that’s something that still remains to be seen.

“We are planning to expose participants to a number of moral dilemmas under the illusion that they are invisible,” says co-author Arvid Guterstam, “and compare their responses to a context in which they perceive having a normal physical body.”

Journal Reference: Arvid Guterstam, Zakaryah Abdulkarim & H. Henrik Ehrsson. Illusory ownership of an invisible body reduces autonomic and subjective social anxiety responses. Scientific Reports 5, Article number: 9831 doi:10.1038/srep09831

First Universal Two-Qubit quantum processor created

qbitPhysicists from NIST (National Institute of Standards and Technology) have demonstrated what they claim to be the first universal programmable quantum information processor that will be able to run any program allowed by quantum mechanics (the set of principles that describe the atomic and subatomic matter). They managed to accomplish this using two quantum bits (qubits) of information.

This processor could prove to be a major breakthrough for a future quantum computer, that could very well be the ‘evolutionary leap’ in the computers’ life thus resulting the possible solve of problems that are untouchable today. The discovery was presented in the latest edition of Nature Physics and this marks the first time anybody has moved beyond asking a single task from a quantum computer.

“This is the first time anyone has demonstrated a programmable quantum processor for more than one qubit,” says NIST postdoctoral researcher David Hanneke, first author of the paper. “It’s a step toward the big goal of doing calculations with lots and lots of qubits. The idea is you’d have lots of these processors, and you’d link them together.”

The processor basically stores binary information in just two beryllium ions held in an electromagnetic ‘trap’, and then handled with ultraviolet lasers. With these in hand, the NIST team managed to perform 160 different processing routines using just the two qubits. Although practically there is an infinite number of programs you can perform with the two qubits, the 160 are pretty much totally relevant, and they prove that the processor is “universal”, Hanneke says.

Of course there will be many more qubits and logic operations to solve bigger problems, but when you come to think about it, all this was done with just two atoms, basically; and the operations they performed were no easy task. Each program consisted of 31 logic operations, 15 of which were varied during programming.

First sparks of life could have appeared from volcanoes

volcanic eruptionJeffrey Bada is a researcher at Scripps Institution of Oceanography. He and his colleagues reanalyzed the classic experiment concerning the origins of life conducted by Stanley Miller who along with Harold Urey realized what we know today as the Miller-Urey experiment. This experiment showed that organic compounds can be created with no relative difficulty from inorganic substances.

Bada was a student of Miller’s, and he is now a professor of marine chemistry at the UC of San Diego. He worked with Adam Johnson, Indiana University graduate student and reanalyzed samples from the Miller experiment.

“We believed there was more to be learned from Miller’s original experiment,” said Bada, co-author in the paper. “We found that a modern day version of the volcanic apparatus produces a wider variety of compounds.”

Miller’s already famous “primordial soup” is still used today in many schools around the world to teach students about chemical reactions that occur in volcanic eruptions that are rich in vapor. In a closed experiment, they circulated methane, ammonia, water vapor and hydrogen that simulate Earth’s early atmosphere and sent a lightning spark through it. Students can then observe that organic compounds are found in the mixture in just a few days. Also, it is believed that in our planet’s early days, the land mass was represented by many small volcanic islands. Lightning and the gases eliminated by these volcanoes could be what caused life to appear and develop. Bada and his team are the first to follow the experiments that Miller conducted a while ago, and they believe that they can find other things that the brilliant scientist could have missed.

“Historically, you don’t get many experiments that might be more famous than these; they redefined our thoughts on the origin of life and showed unequivocally that the fundamental building blocks of life could be derived from natural processes,” said lead author Adam Johnson, a Indiana University graduate student with the NASA Astrobiology Institute team.