We live in a universe dominated by unseen matter, and on the largest scales, galaxies and everything they contain are concentrated into filaments that stretch around the edge of enormous voids. Thought to be almost empty until now, a group of astronomers based in Austria, Germany and the United States now believe these dark holes could contain as much as 20% of the 'normal' matter in the cosmos and that galaxies make up only 1/500th of the volume of the universe. The team, led by Dr Markus Haider of the Institute of Astro- and Particle Physics at the University of Innsbruck in Austria, publish their results in a new paper in Monthly Notices of the Royal Astronomical Society.
Looking at cosmic microwave radiation, modern satellite observatories like COBE, WMAP and Planck have gradually refined our understanding of the composition of the universe, and the most recent measurements suggest it consists of 4.9% 'normal' matter (i.e. the matter that makes up stars, planets, gas and dust), or 'baryons', whereas 26.8% is the mysterious and unseen 'dark' matter and 68.3% is the even more mysterious 'dark energy'.
Complementing these missions, ground-based observatories have mapped the positions of galaxies and, indirectly, their associated dark matter over large volumes, showing that they are located in filaments that make up a 'cosmic web'. Haider and his team investigated this in more detail, using data from the Illustris project, a large computer simulation of the evolution and formation of galaxies, to measure the mass and volume of these filaments and the galaxies within them.
Illustris simulates a cube of space in the universe, measuring some 350 million light years on each side. It starts when the universe was just 12 million years old, a small fraction of its current age, and tracks how gravity and the flow of matter changes the structure of the cosmos up to the present day. The simulation deals with both normal and dark matter, with the most important effect being the gravitational pull of the dark matter.
When the scientists looked at the data, they found that about 50% of the total mass of the universe is in the places where galaxies reside, compressed into a volume of 0.2% of the universe we see, and a further 44% is in the enveloping filaments. Just 6% is located in the voids, which make up 80% of the volume.
But Haider's team also found that a surprising fraction of normal matter -- 20% -- is likely to be have been transported into the voids. The culprit appears to be the supermassive black holes found in the centres of galaxies. Some of the matter falling towards the holes is converted into energy. This energy is delivered to the surrounding gas, and leads to large outflows of matter, which stretch for hundreds of thousands of light years from the black holes, reaching far beyond the extent of their host galaxies.
Apart from filling the voids with more matter than thought, the result might help explain the missing baryon problem, where astronomers do not see the amount of normal matter predicted by their models.
Dr Haider comments: "This simulation, one of the most sophisticated ever run, suggests that the black holes at the centre of every galaxy are helping to send matter into the loneliest places in the universe. What we want to do now is refine our model, and confirm these initial findings."
Illustris is now running new simulations, and results from these should be available in a few months, with the researchers keen to see whether for example their understanding of black hole output is right. Whatever the outcome, it will be hard to see the matter in the voids, as this is likely to be very tenuous, and too cool to emit the X-rays that would make it detectable by satellites.

Story Source:
The above post is reprinted from materials provided by Royal Astronomical Society (RAS). Note: Materials may be edited for content and length.
Scientists on the DZero collaboration at the U.S. Department of Energy's Fermilab have discovered a new particle -- the latest member to be added to the exotic species of particle known as tetraquarks.
Quarks are point-like particles that typically come in packages of two or three, the most familiar of which are the proton and neutron (each is made of three quarks). There are six types, or "flavors," of quark to choose from: up, down, strange, charm, bottom and top. Each of these also has an antimatter counterpart.
Over the last 60 years, scientists have observed hundreds of combinations of quark duos and trios.
In 2008 scientists on the Belle experiment in Japan reported the first evidence of quarks hanging out as a foursome, forming a tetraquark. Since then physicists have glimpsed a handful of different tetraquark candidates, including now the recent discovery by DZero -- the first observed to contain four different quark flavors.
DZero is one of two experiments at Fermilab's Tevatron collider. Although the Tevatron was retired in 2011, the experiments continue to analyze billions of previously recorded events from its collisions.
As is the case with many discoveries, the tetraquark observation came as a surprise when DZero scientists first saw hints in July 2015 of the new particle, called X(5568), named for its mass -- 5568 megaelectronvolts.
"At first, we didn't believe it was a new particle," says DZero co-spokesperson Dmitri Denisov. "Only after we performed multiple cross-checks did we start to believe that the signal we saw could not be explained by backgrounds or known processes, but was evidence of a new particle."
And the X(5568) is not just any new tetraquark. While all other observed tetraquarks contain at least two of the same flavor, X(5568) has four different flavors: up, down, strange and bottom.
"The next question will be to understand how the four quarks are put together," says DZero co-spokesperson Paul Grannis. "They could all be scrunched together in one tight ball, or they might be one pair of tightly bound quarks that revolves at some distance from the other pair."
Four-quark states are rare, and although there's nothing in nature that forbids the formation of a tetraquark, scientists don't understand them nearly as well as they do two- and three-quark states.
This latest discovery comes on the heels of the first observation of a pentaquark -- a five-quark particle -- announced last year by the LHCb experiment at the Large Hadron Collider.
Scientists will sharpen their picture of the quark quartet by making measurements of properties such as the ways X(5568) decays or how much it spins on its axis. Like investigations of the tetraquarks that came before it, the studies of the X(5568) will provide another window into the workings of the strong force that holds these particles together.
And perhaps the emerging tetraquark species will become an established class in the future, showing themselves to be as numerous as their two- and three-quark siblings.
"The discovery of a unique member of the tetraquark family with four different quark flavors will help theorists develop models that will allow for a deeper understanding of these particles," says Fermilab Director Nigel Lockyer.
Seventy-five institutions from 18 countries collaborated on this result from DZero.


Scientists have successfully simulated a black hole shaped like a very thin ring, which gives rise to a series of 'bulges' connected by strings that become thinner over time. These strings eventually become so thin that they pinch off into a series of miniature black holes, similar to how a thin stream of water from a tap breaks up into droplets.
Credit: Pau Figueras, Markus Kunesch, and Saran Tunyasuvunakool; Image courtesy of University of Cambridge
Researchers have shown how a bizarrely shaped black hole could cause Einstein's general theory of relativity, a foundation of modern physics, to break down. However, such an object could only exist in a universe with five or more dimensions.
The researchers, from the University of Cambridge and Queen Mary University of London, have successfully simulated a black hole shaped like a very thin ring, which gives rise to a series of 'bulges' connected by strings that become thinner over time. These strings eventually become so thin that they pinch off into a series of miniature black holes, similar to how a thin stream of water from a tap breaks up into droplets.
Ring-shaped black holes were 'discovered' by theoretical physicists in 2002, but this is the first time that their dynamics have been successfully simulated using supercomputers. Should this type of black hole form, it would lead to the appearance of a 'naked singularity', which would cause the equations behind general relativity to break down. The results are published in the journal Physical Review Letters.
General relativity underpins our current understanding of gravity: everything from the estimation of the age of the stars in the universe, to the GPS signals we rely on to help us navigate, is based on Einstein's equations. In part, the theory tells us that matter warps its surrounding spacetime, and what we call gravity is the effect of that warp. In the 100 years since it was published, general relativity has passed every test that has been thrown at it, but one of its limitations is the existence of singularities.
A singularity is a point where gravity is so intense that space, time, and the laws of physics, break down. General relativity predicts that singularities exist at the centre of black holes, and that they are surrounded by an event horizon -- the 'point of no return', where the gravitational pull becomes so strong that escape is impossible, meaning that they cannot be observed from the outside.
"As long as singularities stay hidden behind an event horizon, they do not cause trouble and general relativity holds -- the 'cosmic censorship conjecture' says that this is always the case," said study co-author Markus Kunesch, a PhD student at Cambridge's Department of Applied Mathematics and Theoretical Physics (DAMTP). "As long as the cosmic censorship conjecture is valid, we can safely predict the future outside of black holes. Because ultimately, what we're trying to do in physics is to predict the future given knowledge about the state of the universe now."
But what if a singularity existed outside of an event horizon? If it did, not only would it be visible from the outside, but it would represent an object that has collapsed to an infinite density, a state which causes the laws of physics to break down. Theoretical physicists have hypothesised that such a thing, called a naked singularity, might exist in higher dimensions.
"If naked singularities exist, general relativity breaks down," said co-author Saran Tunyasuvunakool, also a PhD student from DAMTP. "And if general relativity breaks down, it would throw everything upside down, because it would no longer have any predictive power -- it could no longer be considered as a standalone theory to explain the universe."
We think of the universe as existing in three dimensions, plus the fourth dimension of time, which together are referred to as spacetime. But, in branches of theoretical physics such as string theory, the universe could be made up of as many as 11 dimensions. Additional dimensions could be large and expansive, or they could be curled up, tiny, and hard to detect. Since humans can only directly perceive three dimensions, the existence of extra dimensions can only be inferred through very high energy experiments, such as those conducted at the Large Hadron Collider.
Einstein's theory itself does not state how many dimensions there are in the universe, so theoretical physicists have been studying general relativity in higher dimensions to see if cosmic censorship still holds. The discovery of ring-shaped black holes in five dimensions led researchers to hypothesise that they could break up and give rise to a naked singularity.
What the Cambridge researchers, along with their co-author Pau Figueras from Queen Mary University of London, have found is that if the ring is thin enough, it can lead to the formation of naked singularities.
Using the COSMOS supercomputer, the researchers were able to perform a full simulation of Einstein's complete theory in higher dimensions, allowing them to not only confirm that these 'black rings' are unstable, but to also identify their eventual fate. Most of the time, a black ring collapses back into a sphere, so that the singularity would stay contained within the event horizon. Only a very thin black ring becomes sufficiently unstable as to form bulges connected by thinner and thinner strings, eventually breaking off and forming a naked singularity. New simulation techniques and computer code were required to handle these extreme shapes.
"The better we get at simulating Einstein's theory of gravity in higher dimensions, the easier it will be for us to help with advancing new computational techniques -- we're pushing the limits of what you can do on a computer when it comes to Einstein's theory," said Tunyasuvunakool. "But if cosmic censorship doesn't hold in higher dimensions, then maybe we need to look at what's so special about a four-dimensional universe that means it does hold."
The cosmic censorship conjecture is widely expected to be true in our four-dimensional universe, but should it be disproved, an alternative way of explaining the universe would then need to be identified. One possibility is quantum gravity, which approximates Einstein's equations far away from a singularity, but also provides a description of new physics close to the singularity.
The COSMOS supercomputer at the University of Cambridge is part of the Science and Technology Facilities Council (STFC) DiRAC HPC Facility.
A team of quantum physicists at Aalto University led by Dr. Sorin Paraoanu managed to tame a so-called "dark state," created in a superconducting qubit. A superconducting qubit is an artificial atom fabricated on a silicon chip as an electrical circuit made of capacitors and tunnel junctions.
This technology is one of the most promising for the realization of quantum computers.
In the experiment, the circuit was operated in a regime where it no longer absorbs or emits electromagnetic waves of certain frequency, as if it would be hiding under an invisibility cloak -- hence the term "dark state." Then, by using a sequence of carefully-crafted microwave pulses, the team employed the dark state to realize a transfer of population from the ground energy level to the second energy level, without populating the first energy level. The amount of energy transferred in this process corresponds to a single microwave photon with about the same frequency as those in mobile phones or microwave ovens. This is verified by quantum tomography -- a technique of reconstructing the wave function (in general the density matrix) by applying rotations in an abstract qubit space followed by measurements.
"The matching between the experimental data and the theoretical model is quite remarkable, and this gives us confidence that we understand what is happening and we can control this quantum system. This demonstrates that three-level systems (also called qutrits) can be used in quantum processors instead of the standard two-level qubits," says Antti Vepsäläinen, who implemented this technique and perfomed numerical simulations.
And there is another dazzling fact about the experiment: to perform the transfer, the researchers used a so-called non-intuitive sequence, applying in the beginning a pulse that couples the first level with the second level and only after some time the pulse that couples the ground level to the first level.
"Suppose you want to travel from Helsinki to New York and you have to change your flight in London," explains Sorin Paraoanu. "Normally you would first fly on a plane from Helsinki to London, then wait for some time in the airport in London, then board the flight London-New York. But in the quantum world, you would be better off boarding a plane from Helsinki to London sometime after the flight London-New York took off. You will not spend any time in London and you will arrive in New York right at the time when the plane from Hesinki lands in London." This is mind-boggling but the experiment shows that it is indeed happening.
Besides the relevance for quantum computing, the result also has deep conceptual implications. Much of our understanding of the reality is based on the so-called continuity principle: the idea that influences propagate from here to there by going through all the places in-between. Real objects don't just appear somewhere from nothing. But the experiment seems to defy this. Like in a great show of magic, quantum physics allows things to materialize here and there, apparently out of nowhere.
The team would like to acknowledge the excellent scientific environment created in the Low Temperature Laboratory (part of OtaNano) at the Department of Applied Physics.

Professor Brian Greene answers everything you wanted to know about string theory and the multiverse

Professor Brian Greene answers everything you wanted to know about string theory and the multiverse


Lateline asked you to send in science questions for famed physicist Professor Brian Greene.
Professor Greene is the author of The Elegant Universe, a Peabody Award winner, and director of Colombia's Institute for Strings, Cosmology and Astroparticle Physics.
He spoke to Lateline about the multiverse, string theory and what could be out there.
In case you are wondering, string theory is the idea that the fundamental element of all matter and the forces of nature are even tinier than the smallest particle, and are in fact vibrating filaments of energy of different shapes and sizes that look like strings.
These strings use different vibrations to ultimately create both the chaos of sub-atomic matter and the smoothness of interstellar gravity waves.
Here is what you asked and Professor Greene's answers:

Time in parallel universes?

Bruce Cornell: Professor Greene, you say that in parallel universes there may be more or less dimensions than in ours. Is it obligatory that in parallel universes, time be one of those dimensions?
Professor Greene: It's a great question and again, we are talking hypothetical here. We do not know whether there are extra dimensions or multiverse. Let's go forward with the possible ideas that come out of the mathematics. It's hard for us to imagine a universe that would have no time at all. Time allows change to take place and the very evolution of the universe is what requires some conception of time. Mathematically can we write down a universe that doesn't have time? Sure. Do we think that would be realised in the larger reality that is out there? None of us take that possibility seriously.

Something from nothing?

David Richardson: If there was a beginning, how did something (the universe or the multiverse) come from nothing?
Professor Greene: I have absolutely no idea and nor does anybody else on the face of planet Earth. So again that's one of those great questions at the cutting edge. We do have ideas, suggestions, possibilities — for instance it could be that the state of nothingness is unstable. That is, you can have nothingness, absolute nothingness for maybe a tiny fraction of a second, if a second can be defined in that arena, but then it falls apart into a something and an anti-something. And that something is then what we call the universe. But can we really understand that or put rigorous mathematics or testable experiments against that? Not yet. So one of the big holy grail of physics is to understand why there is something rather than nothing.

The practical applications of gravitational waves?

Bevan John Kirkland: Does Brian believe that the recent discovery of gravitational waves will have practical applications to benefit humankind? If yes, can Brian list the applications?
Professor Greene: Well it depends what you mean by practical applications. If you mean building some new iPhone or widget or something, no, I don't think so. But if you think about a practical implication of enriching your life and giving you a sense of being part of a larger cosmos and possibly being able to use this as a tool in the future maybe to listen not just to black holes colliding, but maybe listen to the big bang itself, those kind of applications may happen in the not too distant future.

The song of the universe?

Ivan de Vulder: If string theory is about vibrations having differing effects on the environment, so too do sound waves. One of the most profound effects on us via sound waves is music. With this in mind, what do you think the universe (string theory) song sounds like?
Professor Greene: Well I wish I could hum it for you. In essence, we string theorists have been trying to work out the score of the universe, the harmonies of the universe, the mathematical vibrations that the strings would play. So musical metaphors have been with us in science since the beginning. The beauty of string theory is the metaphor kind of really comes very close to the reality. The strings of string theory are vibrating the particles, vibrating the forces of nature into existence, those vibrations are sort of like musical notes. So string theory, if it's correct, would be playing out the score of the universe.

What about alien life?

Macy Percival: Does Brian Green believe there is another planet like Earth somewhere in the universe where life as we know it has or is evolving?
Professor Greene: Obviously nobody knows the answer to that so it's just wild speculation, but if you asked me to speak form my gut, my intuition, yeah I think so. So many galaxies, so many planets out there in the universe circling so many stars... it just feels like there's a very good chance that there is another Earth-like planet out there that is able to support some kind of life similar to what we're familiar with. So my guess would be yes.

Bonus Question

Dr Karl Kruszelnicki: Both General Relativity and Quantum Mechanics are perfectly valid ways of exploring our understanding of the universe around us. They both work really well. But they are built on completely different assumptions. In Quantum Mechanics there is no real causality but in General Relativity there is. In Quantum Mechanics, time and space are fixed, but in General Relativity they are as flexible as rubber, a kind of "timey-wimey" Doctor Who insubstantial mess. How can these two systems work on completely opposing bases?
Professor Greene: In quantum mechanics there is A causing B. The equations do not stand outside that usual paradigm of physics. The real issue is that the kinds of things you predict in quantum mechanics are different from the kinds of things you predict using general relativity. Quantum mechanics, that big, new, spectacular remarkable idea is that you only predict probabilities, the likelihood of one outcome or another. That's the new idea. General relativity is in the old Newtonian framework where you predict what will happen, not the probability of what will happen. And putting together the probabilities of quantum mechanics with the certainty of general relativity, that's been the big challenge and that's why we have been excited about string theory, as it's one of the only approaches that can put it together.


In December 2015, the United Nations passed a resolution to recognise on February 11 each year women's contributions to the field.
The UN's research showed females "continued to be excluded from participating fully in science", with the number of science graduates significantly lower than males.
That doesn't mean women have not excelled in science — far from it.
The ABC spoke to a number of Australian female scientists and researchers at the top of their field.

Michelle Simmons

Michelle Simmons has been tasked with creating the next supercomputer that could change the face of international business, weather forecasting and drug design.
While traditional computers complete calculations in sequential order, the quantum computer will complete the tasks simultaneously, potentially resulting in a device millions of times faster.
Right now, the quantum physicist is busy assembling her team at the University of New South Wales, having recently being granted $46 million through government and corporate funding.
Professor Simmons said the goal was to create a commercially available quantum computer in the next decade.
"I think everyone recognises it's a transformational change in the way computers operate," she said.She likens the international race to build the quantum computer to the space race of the 20th Century.
"The rationale for expanding now is we are leading internationally and for a number of years I've felt that if we don't keep that lead, the money will be transferred overseas."
The computer will not be a pocket-size device, but neither will it be like the first supercomputers that took up an entire room. Professor Simmons said it would be something in between.
"My focus has been that we build something practical," she said.
Professor Simmons said she would like to see more women working in quantum computing, but does not believe she has faced barriers or obstacles because of her gender.
"I’d encourage more women to go for it because it's a great field," she said.
"It'd be nice to have female colleagues around but in terms of the research, when you're working at the cutting edge everyone is part of the team."

Rachael Dunlop

Dr Rachael Dunlop believes Australian scientists should communicate better with the public, which in turn would lead to much-needed funding.
Dr Dunlop, who was part of a team that identified a link between an amino acid in blue green algae and motor neurone disease, said any cuts to science were worrying.
"The brain drain in this country is real and it's going to have a huge impact on us," she said.
"In terms of the return on investment for medical science, the return is three or four-fold. Economically it makes no sense to cut money from an industry that is making money.
"I think we have a responsibility to explain to the public what we're doing. Sometimes when our funding gets cut, we haven't got the support for the public."
Economically it makes no sense to cut money from an industry that is making money.
Dr Rachael Dunlop
Dr Dunlop was optimistic about equality in her field, saying the gender split was about half.
"That's not to say there's not inequity. Women aren't paid as much and there's not as much mentorship that goes on," she said.
Dr Dunlop is a visiting associate at Macquarie University, and is working in conjunction with the Institute of EthnoMedicine in Wyoming, USA, on more motor neurone disease research.
Further work is needed to determine what exactly causes the disease, but scientists do know its prevalence is higher in coastal areas where there is greater exposure to the toxic algae.
"It probably requires a faulty gene, combined with the toxin, combined with something like a head injury," Dr Dunlop said.
Nicknamed Dr Rachie, Dr Dunlop regularly writes about health in the media, is the vice-president of Australian Skeptics Inc and has an active presence on social media.
She is also a passionate pro-vaccine campaigner, and said she was "infuriated" by the anti-vaccine movement.
"The myths they perpetuate could lead to illness and, in the worst case scenario, death in children," she said.
"We need to maintain trust in the public health initiatives and they undermine that."

Janet Lanyon

University of Queensland researcher Janet Lanyon has spent more than 30 years researching dugongs — docile creatures known as the "ladies of the sea".
Dr Lanyon leads a research team that examines the mammals along Queensland's coast — an area where population numbers have fallen in recent decades.
"Dugongs are dependent on seagrass ... if something leads to degradation of seagrass then dugongs are in strife," she said.
We have a fantastic team of volunteers. The same people have been working with me for years and they're so dedicated.
Dr Janet Lanyon
"They're susceptible to being captured in nets, harvested for food, they get hit by boats and there may be health issues as well."
While regular water pollution is a hazard, events such as floods and cyclones also cause problems for dugongs because sediment washes into their habitats and can kill seagrass.
Dr Lanyon's research found dugongs behaved differently to whales when it came to migration — they don't travel huge journeys and instead prefer to spend the bulk of their lives in set areas.
Over time that has led to small genetic differences between groups.
Dr Lanyon's team, which has assistance from Sea World, is now conducting further genetic research in Queensland.
"We have a fantastic team of volunteers. The same people have been working with me for years and they're so dedicated," Dr Lanyon said.
Getting dugong samples can be quite the process if researchers want in-depth information such as faecal samples or conducting ultrasounds.
The animals need to be caught and then hoisted onto a boat, where they stay for about half an hour and are then released.
"Once you capture them they just sit quietly in the water, many will try to get away from you in the first minute or two," Dr Lanyon said.
"They're pretty docile, like cows in a way."

Tamara Davis

Tamara Davis first became interested in space when she saw Halley's Comet as a child.
Thirty years on, Professor Davis is working with Nobel Prize-winning astrophysicist Brian Schmidt and several hundred of the brightest international minds to find out more about dark energy.
A relatively recent discovery, dark energy suggests the universe is expanding at an accelerated rate.
Professor Davis's speciality is measuring how soundwaves from the early universe have affected gas patterns millions of kilometres away.
"Once you have measured these soundwaves in the distribution of galaxies, it's like laying grid paper over the universe," she said.
"You can measure how much the universe is expanding and you can measure how fast galaxies are growing."
We've discovered anti-gravity, so if we can harness that maybe we will have new forms of propulsion ... Maybe we will have a way to make a new type of clean energy.
Dr Tamara Davis
Professor Davis believes dark energy could hold the key to extraordinary technological advances on earth and in space.
But she admitted the researchers' "a ha moment" had not quite come yet.
"We've discovered anti-gravity, so if we can harness that maybe we will have new forms of propulsion," she said.
"Maybe we will have a way to make a new type of clean energy."
Professor Davis said she had felt nothing but support from male colleagues, but said being a female in the astrophysics field had been challenging.
Finding work-related female role models was tough, and she believed there were sometimes subtle biases that make it harder for women.
"Sometimes when I'm the expert in the room I'm not the person called on to answer the question," Professor Davis said.
"But I just get on with it ... I've never felt any slight."

Alice Williamson

Alice Williamson says the outbreak of the Zika virus, and news a vaccine is years away, is proof scientists need to work together more.
Finding cures for diseases or designing drugs can often be a top-secret project, with groups of competitive scientists working independently of each other around the world.
Dr Williamson, a malaria specialist at the University of Sydney, is part of a project aiming to buck the trend.
If this resistance spreads where the majority of cases are, it would be a real disaster so we need to have a medicine ready
Dr Alice Williamson
She is part of the Open Source Malaria group, trying to find a new treatment for the disease before strains of the parasite that resist existing medication reach Africa.
"If this resistance spreads where the majority of cases are, it would be a real disaster so we need to have a medicine ready. There is a real urgency," she said.
Open Source Malaria members publish their research in real time and make the data available — a policy Dr Williamson said would hopefully reduce overlapping and scientists making the same mistakes as each other.
It means lucrative patents may be forfeited, but for a disease like malaria — which had an estimated 438,000 victims in 2015 — but Dr Williamson said scientists had a "responsibility" to produce affordable cures.
"If we don't put patents on our drugs and we find something good, hopefully we can get it to market as soon as possible," she said.
Sometimes a major discovery - like finding evidence to support the theory of dark matter - just requires a bit of creative thinking over a curry, as Dr Karl explains.
When professional astronomers design new telescopes, it takes forests of paperwork, big buckeroonies (tens of millions of dollars minimum), and at least a decade.
But hoorah for lateral thinking and hobbies. An astronomer's interest in nature photography led him to a radical new telescope very quickly and cheaply - and also got us one step closer to solving the mystery of how galaxies spring into existence.
One top theory of how galaxies form involves dark matter. Way, way back, over 13 billion years ago, just a few thousand years after the big bang, practically all the mass in the universe was this mysterious dark matter.
The dark matter began to clump together, thanks to gravity, and began to shape itself into roughly spherical objects - which began to collapse inwards.
Various gases (such as hydrogen and helium) collected at the centres of these spheres, turning into the first stars - and the first galaxies.
After a few billion years, the small galaxies merged with each other, eventually evolving into giant galaxies, like our own Milky Way.
But there's a catch with this dark matter theory. If galaxies formed that way, there should be (around each big galaxy) vast messy debris fields left over from the creation process. We would expect to see random ejected stars, partially eaten halos of gas, bulges and streams of matter, and lots and lots of very faint dwarf galaxies. But we can't find them. What cosmic dust bin have they been swept into? Or is the theory wrong?
You need to know a bit about telescopes to understand the next bit.
Most telescopes are inherently not very good at seeing this left-over debris - because it's soft and fuzzy and faint. And this is because the overwhelming majority of professional telescopes catch the incoming light with curved mirrors, not curved lenses. Curved mirrors are really good are seeing small bright objects - which is the exact opposite of what we are looking for.
One good thing about curved mirrors is that you can make them really big. Over the last half-century, there have been tremendous advances and improvements in the performance of mirror-type telescopes. In the specific field of gathering light from small bright objects, they're 100 times better than before.
But when it comes to gathering faint light from large diffuse objects, mirror-type telescopes have had no real improvement over the last half-century. This is for various technical reasons. First, the mirrors themselves cause scattering of the light, due to micro-roughness and dust. Also the secondary mirror in mirror-telescopes creates a large obstruction in the light path, and furthermore, the supports that hold this secondary mirror cause diffraction and bending of the incoming light.
So the ideal telescope for looking at large faint objects would have no mirrors and no obstructions to the incoming light- in other words, it would use lenses, not mirrors. But apart from solar telescopes, professional astronomers haven't used lens-type telescopes for a century.
Now back in 2011, two professional astronomers, Roberto Abraham and Pieter van Dokkum, were in a Nepalese restaurant. After curry and rice and lots of beer, they were shooting the breeze (as you do) about how to find these large faint bits of debris that they believed should be there - left over from the creation of galaxies.
Pieter can Dokkum was a keen nature photographer, and he suddenly realized that a recently released camera lens with a wonder coating on the front might just be perfect for their needs. It was a 400 mm f2.8 SuperTelephoto lens, costing around $10-15,000. The lens coating was called Subwavelength Structure Coating - actually, countless tiny cones or pyramids, on the front of the lens, all pointing outwards. These cones are microscopic - smaller than the wavelengths of visible light. The Physics is complicated, but the end result is that less light is scattered inside the lens - so there's less of what the photographers call "ghosts" or "flares".
And though it's not what this lens is designed for, it can pick up very faint objects.
By March 2012, they had spent about $15,000, done some testing, and found that their single off-the-shelf lens had captured what other astronomers had previously only got hints of. They saw a clear, but very faint, halo of diffuse matter surrounding the galaxy called M51.
Well, if one lens is good, surely three must better. So they swiped the credit card, got another two lenses, and built a special structure so that all three lenses were perfectly lined up. Very shortly afterwards, in September 2012, they got some results - yah! it all worked. By 2013, they were running eight lenses in parallel. In 2014, they published their findings that the galaxy called M101, or the Pinwheel Galaxy, had three previously undiscovered very faint dwarf galaxies orbiting around it.
The astronomers (who admit they can't leave well enough alone) have since upgraded their telescope to 50 lenses. They can now get images in hours, not weeks. Their credit card bill has run up to about half-a-million dollars - but it's still a lot less than tens of millions of dollars, and it was much quicker because the camera company had done all the expensive design work.
They call their array of professional lenses the Dragonfly Telephoto Array for two reasons. First, with 50 commercial telephoto lenses, it looks like the eye of a dragonfly - not a mirror to the soul, but a lens to previously hidden galaxies. And second, Pieter van Dokkum really likes taking photos of dragonflies …

What Are Gravitational Waves And Why Do They Matter?


What Are Gravitational Waves And Why Do They Matter?

If we detect them, it could mean a lot about the universe


Simulation of Gravitational Waves

NASA/C. Henze
Simulation of Gravitational Waves
NASA researchers simulated the gravitational waves that would be produced when two black holes merged.
Physicists have been buzzing (or rather, tweeting) about the possibility that the Laser Interferometer Gravitational-Wave Observatory (LIGO) experiment finally discovered gravitational waves. LIGO has been searching for these cosmic ripples for over a decade. Last September, it upgraded to Advanced-LIGO, a more sensitive system that's also better at filtering out noise. Advanced-LIGO has a much stronger chance of collecting concrete evidence of gravitational waves—if it hasn't already.
Scientists may be excited, but talk of gravitational waves leaves most people scratching their heads. What are these cosmic vibrations, and why are they making waves in the scientific community?

What are gravitational waves?

Gravitational waves are disturbances in the fabric of spacetime. If you drag your hand through a still pool of water, you'll notice that waves follow in its path, and spread outward through the pool. According to Albert Einstein, the same thing happens when heavy objects move through spacetime.
But how can space ripple? According to Einstein's general theory of relativity, spacetime isn't a void, but rather a four-dimensional "fabric," which can be pushed or pulled as objects move through it. These distortions are the real cause of gravitational attraction. One famous way of visualizing this is to take a taut rubber sheet and place a heavy object on it. That object will cause the sheet to sag around it. If you place a smaller object near the first one, it will fall toward the larger object. A star exerts a pull on planets and other celestial bodies in the same manner.
While the rubber sheet analogy is not an exact representation of how spacetime works, it demonstrates that what we think of as a void can be visualized as a dynamic substance. Any accelerating body should create ripples in this substance. But small ripples would fade out relatively quickly. Only incredibly massive objects—such as neutron stars or black holes—will create gravitational waves that continue to spread all the way to Earth.

How can we detect them?

Inside LIGO

Matt Heintze/Caltech/MIT/LIGO Lab
Inside LIGO
A LIGO technician inspects one of the interferometer's mirrors.
A few different experiments are currently underway to search for these waves. The latest rumors are coming from LIGO, which looks for gravitational waves by tracking how they affect spacetime: As a wave passes by, it stretches space in one direction and shrinks it in a perpendicular direction.
LIGO aims to detect these changes using an instrument called an interferometer. This device splits a single laser beam into two and sends both beams shooting off perpendicularly to each other. If the beams travel equal distances, bounce off mirrors, and come back, the waves that make them up should still be in alignment when they return. But a passing gravitational wave can actually change the distance of each arm, which would change the distance that each beam travels relative to its sibling. When the beams return to their source, scientists would be able to detect this change. However, gravitational waves change the length of the interferometer's arms by an incredibly tiny amount: roughly 1/10,000th the width of an atom's nucleus. To pick up such a tiny change, LIGO must filter out all other sources of noise, including earthquakes and nearby traffic. Although LIGO found no gravitational waves in nearly a decade of operation, its recent upgrade to Advanced-LIGO should give it a better chance.
Advanced-LIGO will have to compete with the European Space Agency's (ESA) Laser Interferometer Space Antenna, or LISA. LISA, which will act like a giant LIGO in space, is getting a dry run this year—the ESA launched the LISA Pathfinder in December. It will stay in space for a few months to test the technology that will eventually be deployed in future LISA missions.
But lasers aren't the only way to detect changes in spacetime. For example, the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, looks for gravitational waves by looking at the bursts of radio waves emitted by the neutron stars called pulsars. These radio wave pulses are normally strictly timed, so if they arrive early or late, it could be because a gravitational wave interfered with their journey to Earth.
BICEP2

Steffen Richter, Harvard University
The BICEP2 Telescope At Twilight
In March 2014, the BICEP2 telescope announced the detection of gravitational waves from the Big Bang. Unfortunately, the finding didn't pan out.
Other experiments look for a specific type of gravitational waves created in the aftermath of the Big Bang. They do so by observing the radiation left over from the Big Bang. If the Big Bang made gravitational waves, scientists would expect to see swirls in this radiation's polarization. Programs like Background Imaging of Cosmic Extragalactic Polarization (BICEP), Harvard's series of experiments at the south pole, observe the leftover radiation in an attempt to find the telltale polarization patterns.

What's the point of finding gravitational waves?

Facebook question about gravitational waves


A reader's question about gravitational waves, as posted to the Popular Science Facebook page
Well, gravitational waves give us another way to observe space. For example, waves from the Big Bang would tell us a little more about how the universe formed. Waves also form when black holes collide, supernovae explode, and massive neutron stars wobble. So detecting these waves would give us a new new insight into the cosmic events that produced them.
Finally, gravitational waves could also help physicists understand the fundamental laws of the universe. They are, in fact, a crucial part of Einstein's general theory of relativity. Finding them would prove that theory—and could also help us figure out where it goes astray. Which could lead to a more accurate, more all-encompassing model, and perhaps point the way toward a theory of everything.

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