On Monday, October 16, the National Science Foundation (NSF) will host an event at the National Press Club in Washington, DC featuring researchers from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations, along with scientists from approximately 70
observatories from around the world. Journalists are also invited to attend the event, which is intended to be the global reveal for new findings on gravitational waves.
First the scientists will discuss the new findings, which are from LIGO, Virgo, and various other observatories from all over the world. Next, telescope teams studying extreme cosmic events in partnership with the LIGO and Virgo collaborations will discuss their recent findings. The event will begin for the press and public at 10:00 a.m., EDT.
On September 14, 2015 the LIGO team first detected gravitational waves, a discovery that they announced in February of 2016. Gravitational waves are created (among other things) by the compacting and releasing of the fabric of spacetime as two black holes orbit each other in a dance of death. The first observed event confirmed Einstein’s general theory of relativity, via which he posited spacetime as a singular and unitary phenomenon, and was a milestone in astronomy and physics that would usher in a new field of gravitational-wave astronomy. Three more detections were confirmed since then, the most recent of which was the first joint LIGO and Virgo detection.
Solving Time-Old Mysteries
Physicists from the LIGO project were recently awarded the Nobel for their work with gravitational waves. Their work detecting gravitational waves has permanently changed astronomy and physics, and not simply because it confirms Einstein’s theory of relativity. The detection of the waves will also offer insight into how the universe is expanding — insight that could never have been accessed without otherwise appealing to dark matter, a term that is ultimately a placeholder for a massive force of we-know-not-what that has long eluded the scientific community. Gravitational wave research is also likely to reveal the nature of dark matter.
Event organizers are asking journalists who wish to attend the event to RSVP as soon as possible to email@example.com, and no later than noon EDT Friday, October 13. The National Press Club is located in Holeman Lounge at 529 14th St. NW, 13th Floor, in Washington, DC.
Scientists at the University of Colorado Boulder’s JILA (formerly the Joint Institute for Laboratory Astrophysics) have developed an incredibly precise quantum atomic clock based on a new three-dimensional design. The project has set a new record for quality factor, a metric used to gauge the precision of measurements.
The clock packs atoms of strontium into a cube, achieving 1,000 times the density of prior one-dimensional clocks. The design marks the first time that scientists have been able to successfully utilize a so-called “quantum gas” for this purpose.
Previously, each atom in an atomic clock was treated as a separate particle, and so interactions between atoms could cause inaccuracies in the measurements taken. The “quantum many-body system” used in this project instead organizes atoms in a pattern, which forces them to avoid one another, no matter how many are introduced to the apparatus. A state of matter known as a degenerate Fermi gas — which refers to a gas comprised of Fermi particles — allows for all of the atoms to be quantized.
“The most important potential of the 3-D quantum gas clock is the ability to scale up the atom numbers, which will lead to a huge gain in stability,” said physicist Jun Ye, of the National Institute of Standards and Technology (NIST), who worked on the project. “We are entering a really exciting time when we can quantum engineer a state of matter for a particular measurement purpose.”
During laboratory tests, the clock recorded errors amounting to just 3.5 parts in 10 quintillion, the first atomic clock to achieve such accuracy.
Watch the Clock
“This new strontium clock using a quantum gas is an early and astounding success in the practical application of the ‘new quantum revolution,’ sometimes called ‘quantum 2.0’,” said Thomas O’Brian, the chief of the NIST’s quantum physics division and Ye’s supervisor. “This approach holds enormous promise for NIST and JILA to harness quantum correlations for a broad range of measurements and new technologies, far beyond timing.”
Atomic clocks have clear-cut applications for tasks like time-keeping and navigation. However, the same technology can be used in various different strands of research — like the ongoing effort to better understand dark matter.
It’s been suggested that monitoring minor inconsistencies in the ticking of an atomic clock might offer insight into the presence of pockets of dark matter. Previous research has shown that a network of atomic clocks, or even a single highly-sensitive system, might register a change in the frequency of vibrating atoms or laser light in the clock if it passed through a dark matter field. Given that this project offers much greater stability than its predecessors, it could contribute to new breakthroughs in solving this persistent cosmic mystery.
Based on a new study, the same equipment that was integral to the work of this year’s winners of the Nobel Prize for Physics — gravitational wave detectors — might be able to provide valuable insight into another enigmatic field of research: dark matter.
“The nature of dark matter is one the greatest mysteries in physics,” the study’s co-author Emanuele Berti noted in a University of Mississippi news release. “It is remarkable that we can now do particle physics – investigate the ‘very small’ – by looking at gravitational-wave emission from black holes, the largest and simplest objects in the universe.”
Berti and an international team of researchers produced calculations that suggest that some kinds of dark matter could form clouds around black holes. The going theory is that these clouds emit gravitational waves that could be detected by certain advanced equipment. “Surprisingly, gravitational waves from sources that are too weak to be individually detectable can produce a strong stochastic background,” explained co-author Richard Brito.
Dark matter is estimated to be five times as abundant as ordinary matter, and yet, no one has been able to directly detect it. It has the potential to unlock all kinds of secrets about the universe, so the great amount of interest in this topic by scientists and astrophysicists isn’t surprising.
If Berti and the rest of his team are correct in their belief that gravitational wave detectors will allow us to finally “see” dark matter, the implications would be tremendous. As Brito noted, “This is a new, exciting frontier in astroparticle physics that could shed light on our understanding of the microscopic universe.”
Scientists have discovered a mismatch between a map of the early universe and measurements of the universe today. If the disparity remains through future measurements, that difference could rewrite physics.
The recent results, part of the ongoing Dark Energy Survey (DES) of a huge portion of the southern sky, reveal how matter is distributed among 26 million galaxies. They also provide one of the clearest and most powerful images of our universe to date.
The new data is also being compared with images taken in 2013 with the Planck satellite, which show the universe as it once was. The comparison enables scientists to get an “in motion” sense of the universe as an evolving system, and to make predictions about the future. And while many astronomers think that dark energy is a constant force, these preliminary results seem to suggest that it might not be.
The Planck images showed that dark matter comprised 34 percent of the universe in its early days, but these new findings indicate that it currently makes up only 26 percent.
Understanding how matter is distributed helps us to know how dark energy and dark matter oppose each other in our universe. Dark energy pulls every galaxy apart as it causes the universe to accelerate; dark energy is the opposing force, physicists think, which pushes galaxies back together. If this is correct, dark matter (which scientists are still searching for) could be losing its cosmic battle to hold things together, changing physics as we know it.
An Uncertain Outcome
The new results arose from the first observational season of the four-meter Victor M. Blanco Telescope. The observational period for the DES lasted only six months, but has already produced this strange result. The survey with the Blanco telescope will continue for five years, yielding more and better data as time passes.
Astronomers are rightly reluctant to come to overly dramatic conclusions based solely upon these initial data. From a statistical perspective, the variation between the early universe and the current version is slight. The mismatch may also disappear with more data, indicating that one or both of the measurements was incorrect.
However, this isn’t the only disparity; for example, results from the South Pole Telescope also conflict with the Planck data.
Although the scientific community has been assuming that the universe would continue to expand while galaxies would remain glued together, this may be wrong. If dark energy continues to increase, it’s possible that one day galaxies and everything inside them — down to atoms themselves — could expand enough to be torn apart.
As unsettling as that thought is, this may be yet another fascinating anomaly about our universe, with context that changes as we continue scanning the skies.
New research conducted as a part of the ongoing Dark Energy Survey (DES) has used the way mass distorts light to produce a bigger, more highly detailed map of the Universe’s dark matter structure.
Not only do the measurements support the view that about 26 percent of the Universe is made up of the mysterious stuff, it’s turned out that its distribution is a little smoother than had been estimated, which if confirmed could hint at undiscovered physics.
Since 2013, the international team behind the DES has been carrying out a deep, wide-area scan of about 1/8th of the night sky in an effort to collect data on some 300 million galaxies billions of light years from Earth, all to figure out what the hell this dark energy business is all about.
Dark energy and dark matter don’t have much in common other than the fact they’re both tight-lipped about their nature.
Dark energy is something of a black box that explains why the Universe seems to be accelerating in its expansion, an observation that has been broadly accepted now for at least two decades.
Whatever it is, it’s no small deal, making up roughly 68 percent of the Universe’s total energy.
On the other hand, dark matter is more about pulling stuff than pushing space apart. Just as mysterious, it’s a black box that explains why galaxies hold together in spite of not seeming to have enough visible matter.
Knowing more about how the Universe spreads out over time, and how its matter clumps together, could reveal more about what exactly these things are. This requires knowing what everything looked like around 14 billion years ago when the Universe still had its baby-smooth skin, a feat that requires a camera that can look back in time.
Snapshot of the Universe
Fortunately that’s exactly what the Planck telescope can do. It provided just such a snapshot in the form of the Cosmic Microwave Background – a map of the radiation still humming through the Universe as an echo of its earliest days.
In 2015, DES released the first of its maps of the cosmos based on data from 2 million galaxies collected by its Dark Energy Camera, giving researchers a relatively more recent ‘now’ to compare with the ‘then’.
Fast forward to today: we now have new map that’s 10 times bigger, based on analysing the shapes of 26 million galaxies using gravitational lensing, a phenomenon predicted by Einstein’s general relativity and first observed in 1919, launching the German born genius into the public spotlight.
Take a look at the fancy new map below.
Today we can use the fact that mass changes space to ‘see’ dark matter by measuring how light behind it distorts as it passes by, giving us a way to measure the amount and distribution of both kinds of matter across a portion of the Universe.
Comparing Planck’s map with the one produced by the DES has supported the consensus on how much dark matter and dark energy there seems to be.
“The DES measurements, when compared with the Planck map, support the simplest version of the dark matter/dark energy theory,” says researcher Joe Zuntz from the University of Edinburgh.
“The moment we realised that our measurement matched the Planck result within 7 percent was thrilling for the entire collaboration.”
That 7 percent is close, but the fact it isn’t exact could also be exciting for a whole other reason – if confirmed, the difference between the two results could mean that mass is clumping more slowly than current physics predicts, hinting at something undiscovered.
It’s a fair bet that additional data will see the numbers draw more closely together in the future. Considering the results are also yet to be peer reviewed, all of the usual cautions apply.
But discoveries in astronomy often start with discrepancies such as this, so it’s well worth a closer look.
“The Dark Energy Survey has already delivered some remarkable discoveries and measurements, and they have barely scratched the surface of their data,” says Fermilab’s director Nigel Lockyer.
“Today’s world-leading results point forward to the great strides DES will make toward understanding dark energy in the coming years.”
With another year to go and only 1/30th of the sky so far mapped, we look forward to an even bigger and better map in the near future.
The current results of the survey can be found on the DES website.
Dark matter is the unseen, mostly unknown material that comprises the bulk of our Universe. However, exactly what dark matter is has long been debated, in large part because it has yet to be directly detected. New research from an international team of cosmologists narrows down the possibilities of what dark matter might be using data from intergalactic space.
The research findings conflict with the concept of “fuzzy dark matter,” and instead suggest the existence of a “cold dark matter” model. These results will change the way scientists search for dark matter, informing what kinds of properties they seek out. “What we have done is place constraints on what dark matter could be—and ‘fuzzy dark matter,’ if it were to make up all of dark matter, is not consistent with our data,” lead author and University of Washington Department of Astronomy postdoctoral researcher Vid Iršič said to Phys.org.
We cannot see dark matter, but we know it exists simply because it has to — without it, the universe cannot exist under our current understanding of natural law. All of the visible mass in the universe only accounts for about 15 percent of the total mass, and something has to make up the other 85 percent.
To account for this disparity, scientists have hypothesized the existence of dark matter, but they are still in the dark about the exact composition of the elusive substance.
Traditionally, scientists believe dark matter consists of weakly interacting particles that we can see influenced by gravity on larger scales. This “cold” form of dark matter meshes well with what we know about the relationship between galaxies within the universe, but it does not translate down to the smaller, single galaxy-scale and the rotations of stars within those galaxies.
Now, two scientists think they may know why that is.
This hypothesis would allow for an additional force outside of gravity to explain galactic behaviors. As particle physicist Tim Tait from the University of California, Irvine, told Quanta Magazine, “It’s a neat idea. You get to have two different kinds of dark matter described by one thing.”
The findings have yet to be peer reviewed, and until the hypothesis can be tested, no one can say for sure whether it’s accurate. However, the research can be looked over on the pre-publication site arXiv.org, and Khoury and Berezhiani are currently developing tools to test their model.
If confirmed, the discovery could have far-reaching implications for the study of our universe and how it operates, but for now, we’ll just have to be content with what appears to be an exciting development in the search to understand dark matter.
University of Zurich (UZH) researchers have simulated the way our Universe formed by creating the largest virtual universe with a large supercomputer. The team turned 2 trillion digital particles into around 25 billion virtual galaxies that together make up this virtual universe and galaxy catalogue. The catalogue will be used on the Euclid satellite, to be launched in 2020 to explore the nature of dark energy and dark matter, to calibrate the experiments.
“The nature of dark energy remains one of the main unsolved puzzles in modern science,” UZH professor of computational astrophysics Romain Teyssier said in a press release. Euclid will not be able to view dark matter or dark energy directly; the satellite will instead measure the tiny distortions of light of distant galaxies by invisible mass distributed in the foreground—dark matter. “That is comparable to the distortion of light by a somewhat uneven glass pane,” UZH Institute for Computational Science researcher Joachim Stadel said in the release.
Scientists at the University of British Columbia have proposed a radical new theory to explain the exponentially increasing size of the universe. Ultimately, it seeks to reconcile two different concepts in physics: Quantum Mechanics and Einstein’s Theory of General Relativity. the researchers argue that instead of dark energy causing the universe’s growth, it could be explained by constant quantum fluctuations of vacuum energy.
In their work, the researchers argue that, instead of dark energy causing the universe’s growth, it could be explained by constant quantum fluctuations of vacuum energy. The paper claims — if their findings are true — that “the old cosmological constant problem would be resolved.” The press release notes the potentially transformative nature of the work: “Their calculations provide a completely different physical picture of the universe.”
Similarly, Bill Unruh, the physics and astronomy professor who supervised P.H.D student Qingdi Wang’s work, stated that the research offers an entirely new take on old problems: “This is a new idea in a field where there hasn’t been a lot of new ideas that try to address this issue.” In the end, their calculations provide a fundamentally different picture of the universe: one in which space-time is “constantly moving,” fluctuating between contraction and expansion. It’s the small net effect towards expansion, though, that drives the expansion of the universe.
Unruh uses the sea as an analogy to explain why we cannot feel the effects: “It’s similar to the waves we see on the ocean […] They are not affected by the intense dance of the individual atoms that make up the water on which those waves ride.”
The Big Why
Previous belief has held that the universe is expanding steadily due to dark energy pushing other matter further and further away. When we apply quantum theories to vacuum energy, it results in an increasing density which could in turn result in universal explosion — due to the gravitational effect of the density.
The discovery that the universe is expanding was made simultaneously by two independent teams in 1998: Supernova Cosmology Project and the High-Z Supernova Search Team. Three members of the two teams have since won Nobel prizes for their work, which measured light using ‘standard candles.’ Since that discovery was made, scientists have tried to work out exactly what this energy is that’s driving the cosmos apart.
Despite the fact that it has been a compelling mystery for decades, there haven’t been that many theories posed. So, while the work of Wang and Unruh may not provide the ultimate answer, they present a new, potential solution to one of the most fundamental problems in cosmology.
Editor’s note: This article has been updated. A previous version mistakenly referred to “dark energy” as “dark matter.”
From the beginning of time, human progress has been driven by our need to understand how and why all things happen. The more we come to understand our surroundings, the deeper we desire to understand them further still. As our ancestors were presented with challenges, they innovated solutions using whatever knowledge and resources were available to them. When we think about how little our earliest ancestors had to work with, it seems all at once marvelous that they achieved anything at all, and almost somewhat boring — as the problems of the past seem so simple when examined through our present gaze, millennia in the future.
Even just a few generations ago, our parents and grandparents found the technology of The Jetsons and Star Trek to be fantastical and purely science fiction. Many of those clever gadgets — whether it be subservient robots or handheld computers — are already so commonplace as to be considered mundane by the newest generation. A generation that has never lived in a world with smallpox, or without an iPhone. As science and technology advance at seemingly warp speed, it may feel as though we know practically everything there is to know. Or, at least, that we are getting very close.
In an op-ed for Scientific American, physicist and author Daniel Whiteson implores us to not become complacent. To not be satisfied by all that we have come to know about the universe around us and within us and beyond us because there is still so much left to learn. “When we teach science to children,” Whiteson advises, “we should certainly describe what we do know, but there should also be a strong emphasis on what we don’t know, to inspire the next generation of explorers.”
What are, then, some of those things we don’t yet know that could serve as inspiration for the next Einstein or Curie? The next Stephen Hawking or Katherine Johnson?
The Mystery of Dark Matter
One of the universe’s greatest tricks, a most profound irony, is that the very evidence that makes physicists and astronomers certain that “dark matter” exists also makes it nearly impossible for anyone to prove its existence. We don’t even recognize dark matter for what it is, because we don’t know what it is — we only register the impact it seems to have on gravity. In other words, we deduce that it’s real because we can see the effect it has on its surroundings. Kind of like a poltergeist moving furniture around in the dark.
The cosmic frustration of these elusive particles is made more challenging because those interactions are so infrequent that we’ve rarely witnessed them. It may also be that these particles are their own matter and anti-matter partners, rendering them invisible to us. And in fact, when it comes to thinking about dark matter, it isn’t simply one problem. The “problem of dark matter” is actually a bunch of problems that all must be solved — which is difficult when you’re not even sure what you’re looking for.
The Deep Blue Sea
As vast and therefore intriguing as the outer limits of our universe may be, here on Earth there are numerous mysteries left to be solved in our oceans. The entire landscape of the deep sea — the world underwater — is as varied as the one above: there are waterfalls, volcanoes, and even lakes, yet we have yet to truly explore the majority of them. And we understand even less about the creatures that live there. We may well understand the topography of the moon better than we do our oceans, strange as that seems. We’ve been looking up when perhaps it would have been just as interesting to look down.
In the deepest, darkest parts of the ocean there are species we’ve barely caught glimpses of and therefore have not thoroughly studied. It’s the stuff of legends — except it’s all real. The “final frontier” may not be the far reaches of space, but the unfathomable depths of our oceans.
The “Hard Problem” of Consciousness
One of the most fascinating, perplexing, and often frustrating unanswered questions is that of consciousness. The human brain continues to be one of the most question-filled foci of science and philosophy alike, and many of those quandaries are based in the question of what it means to be conscious. While we can glean some answers about brain function by using technology like MRIs, consciousness is far more nuanced than even our most refined medical imaging can detect. We know quite a bit about the structure and function of consciousness, but the feeling of it – and the why — have proven so subjective that the challenge of measuring them remains unsolved.
The paradox is that consciousness is, perhaps, the one human experience that each of us knows intensely and intimately — yet to explain it to someone else and have them understand it and share in it seems, at this point anyway, next to impossible.
Are Aliens Out There?
Considering how old and enormous our universe is, the expectation is that there simply must be other lifeforms out there. The question is, why haven’t we made contact with them? Potential solutions to this question, known as Fermi’s Paradox, include everything from “aliens exist and know about us, but think we’re boring and therefore aren’t bothering to say hi” to “aliens don’t know about us at all because we’re located in the universal equivalent to the boondocks.”
As technology advances and allows us to not only see into space farther and more accurately — largely in the form of advance telescopes and satellites — but also allows us to travel into space, if there’s life out there to be found (and that wants to be found), it seems reasonable to think we’ll get there eventually.
Where Did We Come From (And Where Are We Going?)
The question of evolution has plagued humanity since the beginning of time. Our desire to definitively know how we got to where we are now isn’t just important because we care about our own evolutionary history, but because it could give us incredible insight into where we’re headed as a species. It could also, potentially, reveal important information about how evolution could be altered.
It may be that the key to understanding some of the most pressing issues in health and medicine — such as cancer and other illnesses, regenerative medicine, and even longevity — could be lurking in our evolutionary development.
It may well be that these and other greatest mysteries of the universe may not be solved in our lifetime. But our grandparents likely never imagined living in a world where they could put a computer in their pocket or ride in a self-driving car. It may be that in our twilight years, we will try to remember what life was like before we met aliens, colonized Mars, or cured cancer.
Dark matter has been making more headlines than an A-list celebrity in Hollywood over the course these past few months. This might be because the scientific community finally produced an “image” of the elusive substance, fueling our peer-reviewed paparazzi expectations. But what exactly is dark matter and why is it so intriguing?
The brief video below by Minute Physics touches on a few key concepts surrounding dark matter, including how scientists noticed that the universe behaved far differently than they had expected. While researchers expected stars at the far end of a galaxy to taper off in speed and ultimately leave from their galactic orbits, they observed something quite different. The stars as the ends of galaxies actually accelerated to remain in orbit, suggesting that something was providing a strong enough gravitational force to keep them in check.
Minute Physics goes on to explain that this something, which scientists refer to as dark matter, is four times more common in the universe than visible matter and why it’s necessary.
The theory that birthed the concept of dark matter came to be out of necessity. Based on the matter we can see, our universe shouldn’t be able to exist and operate as it does — this visible matter can’t generate the gravity necessary to keep our galaxies held together. Dark matter is a way for scientists to account for this discrepancy. They posit that our universe must contain a kind matter that we cannot see, a kind that doesn’t absorb, reflect, or emit light — a truly dark matter.
For our scientific models to hold true, dark matter must make up more than a quarter of all the matter in the universe. Still, what dark matter is actually made of remains a mystery, and finding evidence of something that cannot be seen is a daunting task. Previously, the gravitational effects of dark matter are the closest thing to proof that scientists have, but now, researchers from the University of Waterloo in Ontario, Canada, have something even better: a composite picture that proves that galaxies are indeed connected by dark matter.
Using a technique known as weak gravitational lensing, the researchers combined images taken over the course of years to show the presence of dark matter. The composite was created using images from more than 23,000 galaxy pairs situated 4.5 billion light-years away.
The Missing Universe
We may not have greater insight as to exactly what this matter is composed of, but at least we now have a physical representation of its existence between galaxies.
“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” explained Mike Hudson, a professor of astronomy at Waterloo, in a press release from the Royal Astronomical Society. “This image moves us beyond predictions to something we can see and measure.”
Indeed, the image is an important step toward legitimizing dark matter and dark energy at a time when other scientists are proposing models that would do away with the need for dark matter to exist entirely. It brings us closer to understanding dark matter and the role it plays in binding the universe together. Existence is an infinitely large puzzle comprising innumerable pieces. Any time we can find a way to connect those pieces we bring the big picture into greater focus and move one step closer to truly understanding the world in which we live.
Whether you’ve played it or not, you might have heard of the Mass Effect series. The series features a space odyssey through which users can play as characters who can control mass effect fields, giving them some extraordinary powers.
Taking a deeper look at these powers, it’s interesting to note that they may be derived from dark matter, something that makes up 23% of the universe. It’s theorized that dark matter is invisible because it doesn’t interact with the electromagnetic spectrum. And although the LHC has yet to conclusively detect dark matter, we know that dark matter exists because the spins of galaxies are affected by something much stronger than visible matter.
In the Mass Effect series, some lifeforms have biotic abilities, meaning they can manifest mass effect fields and manipulate their environment. Characters can warp, pull, slam, lift, and charge, among other abilities. As shown in the Nerdist video, each ability involves a precise manipulation of dark matter while falling within the limitations of physics.
While there is no real evidence that we may one day be able to shape our environment with the help of dark matter, it is interesting to note that one of the largest science fiction video game franchises may not be too far off in their premise.
“Dark energy” is believed to comprise 68 percent of the universe, but a Hungarian-American research team thinks it may not exist at all. The researchers believe that the concept of dark energy is merely filling in the gaps left by existing models of the universe, which fail to account for its changing structure. Once the model is corrected, the gaps disappear, and so does the need for dark energy within the model.
Our universe has been expanding ever since the Big Bang 13.8 billion years ago. Hubble’s law provides the key piece of evidence supporting this expansion. The law states that, on average, the distance between us and a given galaxy and its recessional velocity — the speed with which it moves away from us — are proportional. Astronomers observe the lines in a galaxy’s spectrum to measure the recessional velocity. The faster the galaxy moves away from us, the more the lines shift toward red. All of this led scientists to think that the entire universe is constantly expanding and that it must have begun as a vanishingly minuscule point.
Later, astronomers noticed that they needed something more to explain the motion of stars within galaxies and that brought upon the potential of unseen “dark matter.” Finally, after astronomers observed Type Ia supernovae, white dwarf stars exploding in binary systems, in the 1990s, they concluded that 68 percent of the cosmos is comprised of dark energy, which, along with about 5 percent ordinary matter and 27 percent dark matter, drives the expansion of the universe.
The new work, led by Eötvös Loránd University Phd student Gábor Rácz, suggests an alternative explanation for the expansion of the universe. The team argues that conventional cosmological models ignore the structure of the universe and rely on approximations. This leads to inevitable gaps in models, and that’s what dark energy has been sloppily used to fix.
Reframing the Debate
The team reconstructed the evolution of the universe using a computer simulation to model the ways that gravity affects the distribution of millions of dark matter particles. The reconstruction includes the formation of large scale structures and the early clumping of matter. Taking these structures into account produced a different simulation than conventional models, which show the universe expanding smoothly. This new simulation is consistent with previous models in that it shows an acceleration overall, but in it the expansion of the universe is uneven, with different regions within the cosmos expanding at different rates.
We do not question [the validity of theory of general relativity]; we question the validity of the approximate solutions. Our findings rely on a mathematical conjecture which permits the differential expansion of space, consistent with general relativity, and they show how the formation of complex structures of matter affects the expansion. These issues were previously swept under the rug but taking them into account can explain the acceleration without the need for dark energy.
If upheld, this work could impact future physics research and models of the universe significantly. For two decades, theoretical physicists and astronomers have speculated about the unsolved mystery of the nature of dark energy. With this revised model, an interesting new debate can begin.
Dark energy and matter, two hot-button subjects of physics that have captivated and stumped enthusiasts and experts alike. Since its discovery in 1998, dark energy has been a subject of extensive study and confusion. Theoretically comprising approximately 68% of the known universe, this mysterious form of energy is said to be accelerating the expansion of the Universe. However, despite these past conclusions, new simulations suggest that dark energy might not actually exist at all.
Physicists hailing from Loránd University in Hungary and the Institute for Astronomy at the University of Hawaii mathematically modeled the effect of gravity on “dark matter” (they used millions of particles to represent dark matter). This model showed how matter would have gathered and resembled large scale galaxy structures (or “bubbles” of space and their surrounding galaxies) in the early Universe. And, much like the actual Universe, their model expanded. However, averaging out how these different “bubbles” expanded, the researchers found an overall acceleration.
What Is the Universe Made Of?
Now, this might not seem like a huge deal, but when you think about this study in terms of dark energy, what they really found was an explanation for how the formation of large and complex structures in the universe affects its expansion. And, according to László Dobos from Eötvös Loránd University, “These issues were previously swept under the rug but taking them into account can explain the acceleration without the need for dark energy.”
Their calculations showed that dark energy could have really just been a tool to explain the expansion of the Universe. Dark energy could really just be an illusion of energy that comes from changing structures in the Universe. So…what does this mean? Well, for starters it means that there is both more and less mystery in our Universe. We might be a step closer to better understanding the expansion of the Universe, but this new possibility opens up a lot of new doors and introduces a lot of new questions.
A central goal that modern physicists share is finding a single theory that can explain the entire universe and unite the forces of nature. The standard model, for example, leaves Dark Matter, Dark Energy, and even gravity out of the picture — meaning that it really only accounts for a very small percentage of what makes up the universe.
String Theory stitches Einstein’s conception of the general theory of relativity together with Quantum Mechanics, and the result is quantum theory applied to gravity. This application allows us to break down the universe beyond the subatomic particle level into vibrating strings whose interactions and vibrations make up the universe.
In other words, all matter is made up of atoms, and all atoms are composed of electrons, neutrons, and protons — and these can be broken down further into quarks. Quarks are are made up of these dynamic strings, whose motions in space are the key to understanding the universe, explained Michio Kaku, physicist at the City College of New York. Kaku is the He’s the co-founder of string field theory (a branch of string theory).
What is String Theory & How Does it Work?
Will A “Theory of Everything” Transform Our World?
In an interview with Big Think, Kaku explained String Theory this way: The standard model for physics, including the Higgs Boson, represents the lowest octave of a vibrating string. Dark matter, which makes up around 23 percent of the universe, is the next vibration up. Dark energy happens when the symmetries of the super string are broken, and it comprises about 68 percent of the universe.
So, according to String Theory, each vibrating string corresponds to a different particle, and there are almost certainly more dimensions to the universe than the four we once thought represented everything. String Theory is unique at this time because, as Kaku pointed out, it is the only game in town that truly has the potential to be a Theory of Everything.
One of the great scientific minds of the 21st century, Vera Rubin, passed away at the age of 88. She, along with Kent Ford, were credited with the discovery of evidence for dark matter—which until today remains as one of the universe’s most mysterious substances.
In the late 1960s, Rubin was working on the behavior of spiral galaxies when she noticed certain peculiarities. As she trained her eye on the Andromeda galaxy, she saw that stars on the outskirts of galaxies were moving just as quickly as those in the middle. This defied the then-accepted theoretical predictions; the stars further out the center should have been moving slower. Given that the stars in the Andromeda were hurtling through space at such speeds, the galaxy should have been flying apart. Thinking this was just a fluke, she looked at other galaxies, but the same phenomenon was observed.
This led Rubin to theorize alternatives to the standard Newtonian model. It was either Newton’s gravitation laws failed at the scale of the galaxies, or a huge amount of invisible mass was holding the galaxies together. This unseen substance, by Rubin’s calculations, outnumbered the visible components of galaxies ten-to-one and has since been called dark matter.
Lone, Bright Star
Science has always been a predominantly male field, especially astronomy during Rubin’s time. She was the only astronomy major to graduate Vassar in 1948 and was subsequently rejected by Princeton simply because the university did not allow women into its graduate astronomy program. In 1965, she was the first woman allowed use to the facilities at the Palomar Observatory.
Since then she has received multiple awards in recognition of her pioneering work, being elected to the National Academy of Sciences, awarded the National Medal of Science in 1993, and conferred the Gold Medal of the Royal Astronomical Society in 1996—the first woman since to receive the honor since 1828.
Rubin also strongly advocated for women to start getting into the sciences, believing that there was no problem that can be solved my a man that a woman couldn’t. She acknowledged the discrepancy in opportunities, saying “[w]e all need permission to do science, but, for reasons that are deeply ingrained in history, this permission is more often given to men than to women.”
Carrying on Her Legacy
Most of the astronomical community today accept dark matter, with many experiments detecting the supposed particles through means other than gravity. Those who don’t buy it, on the other hand, are pushing for modifications in accepted models — a stance which Rubin herself said she would have preferred.
In her book’s preface, she wrote, “[w]e have peered into a new world and have seen that it is more mysterious and more complex than we had imagined. Still, more mysteries of the universe remain hidden. Their discovery awaits the adventurous scientists of the future. I like it this way.”
Vera Rubin’s legacy will live on in her work. May she rest in peace.
In 2010, renowned string theory expert Erik Verlinde from the University of Amsterdam and the Delta Institute for Theoretical Physics proposed that gravity is not a fundamental force of nature, but rather an “emergent phenomenon.” And now, one hundred years after Einstein published the final version of his general theory of relativity, Verlinde published his paper expounding on his stance on gravity—with a big claim that challenges the very foundation of physics as we know it.
Verlinde’s emergent gravity theory makes one very important implication: dark matter does not exist. His research makes sense of the behavior of gravity without the need for the existence of a dark matter particle.
Researchers from the Leiden Observatory have studied more than 33,000 galaxies to see if Verlinde’s theory checks out—and the results show that it is, in fact, more accurate at confirming the universe’s gravity distribution than Einstein’s theory of relativity.
Watch the video below to know more about Verlinde’s alternate explanation to gravity.
“A Totally Different Starting Point”
Throughout the years, physicists have been in search of dark matter, which would explain the discrepancies between general relativity and the gravitational lensing observed in light space. While gravity is responsible for this bending of light, the problem is that the bending is not consistent with the amount of matter present, suggesting the presence of invisible particles to account for the additional gravitational force.
A lot of effort, equipment, and funds have been dedicated to the quest for dark matter. If proven right, Verlinde would be putting an end to a four-century long search for the hypothetical particle, and what we know of our universe will drastically change.
Verlinde’s calculations were only applicable to isolated, spherical, and static systems, which means that dark matter is not completely debunked. As with any theory, Verlinde’s emergent gravity theory will undergo modifications as more physicists weigh in on the matter over the next years. Verlinde is optimistic about its progression: “Many theoretical physicists like me are working on a revision of the theory, and some major advancements have been made.”
“We might be standing on the brink of a new scientific revolution that will radically change our views on the very nature of space, time and gravity,” he added.
In the 1600s, astronomers proposed the existence of objects in the universe that emit little or no light and can only be detected by the way their gravitational forces interact with other objects around them. Little did they know that this hypothesis was just the beginning of a mysterious saga that would haunt the world of physics for hundreds of years: what is dark matter?
Four centuries later and we still know very little about what dark matter is. We know it does not absorb or emit light, but its gravitational forces supposedly account for the unexplained bending or lensing of light from the galaxy observed in telescopes, which is the only way we can detect it as of now.
Several candidates for dark matter have been proposed throughout the years. One study even explored the idea that dark matter is actually made of massive gravitons. This is complicated, seeing as scientists would be trying to explain a hypothetical particle using yet another hypothetical particle. Different teams of researchers have published many calculations on what dark matter is or isn’t and how we can capture the elusive particle, and yet even the world’s most sensitive detector—LUX, had nothing to show for it.
Cornering the Enigmatic Particle
In an interview with Scientific American, award-winning theoretical astrophysicist Priyamvada Natarajan shared that she is optimistic that we will be unmasking the enigmatic particles soon.
“What I think is entirely possible is that we are off in terms of our expected properties for the dark matter particle, which might account for why they remain elusive to date,” Natarajan said.
“We are really close to solving this mystery of the missing particle. This is akin to a crime scene, where we have the motive, the weapon as evidence but the body is missing! To me there are several exciting upcoming developments that I keenly look forward to in the coming 3-5 years or so that might break this intellectual impasse.”
Technology is currently progressing at a fast pace, allowing us to see far more than we used to. Physicists are positive we’ll corner the hypothetical particle. “I think we are poised to make an epistemic leap in terms of unraveling the true nature of dark matter very soon,” Natarajan says.
The search for the universe’s missing particles, supposedly taking up as much as 80% of the total mass of the universe, hasn’t really yielded definitive results. Different theories have been put forward to understand dark matter — with some even saying may not really exist. Physicists from Cornell University offer an explanation that changes the way we understand dark matter, and could explain why all the search so far has been for naught.
Supposedly, there used to be more dark matter around in the universe than what we have today. One theory explains that the decrease is based on assuming dark matter particles are WIMPs or weakly-interacting-massive-particles. As the universe cooled, dark matter annihilated away up to a point when thermal equilibrium was attained, when dark matter particles remained mostly constant after ‘freezing-out’.
The Cornell physicists, publishing their study in Physical Review Letters, offer a different take on dark matter freeze-out. Instead of just one particle, several dark sector particles co-decayed producing the current dark matter density observed. One or many of these particles could be dark matter.
Understanding the Universe Better
This new way of looking at how dark matter annihilation might’ve happened, changes our understanding of just how much dark matter is there in the universe right now. “Co-decaying dark matter provides a new mechanism for dark matter to freeze out and obtain its observed relic abundance,” explained researcher Eric Kuflik. “Here dark matter can freeze out early in the universe and obtain the correct abundance we observe today.”
According to the new research, it might be of a smaller density than previously assumed. To explain this correct abundance of dark matter, its annihilation rate must’ve been larger than what’s explained by earlier models, such as the WIMP concept.
In the new concept, dark matter is said to have decoupled from the standard model of particles earlier on, causing disequilibrium. The decay started at a later point and freeze-out began much later, as well.
This type of dark matter’s “properties suggest that the current experiments would not be sensitive to [it], but it can lead to other, unique experimental signatures,” Kuflik said. “Furthermore, the mechanism is quite general and will be realized in many extensions of the standard model of particle physics.” Co-decaying dark matter requires more indirect-detection experiments in order to be found.
Dark matter and dark energy are arguably the most elusive components of the universe. Dark matter in particular has remained undetected. Its existence is observed only through the gravitational effects it’s thought to produce — which exist, basically, to render the theories about it somewhat manageable. But, despite the numerous studies, we remain largely in the dark about dark matter.
Perhaps because of it being mysterious and all, astronomers like Hendrik Hildebrandt from the Argelander-Institut für Astronomie in Bonn, Germany and Massimo Viola from the Leiden Observatory in the Netherlands, continue to study dark matter and ways to find it. Hildebrandt and Viola, together with a team from several international institutions, believe that dark matter may not be as clustered as previously thought. It’s very possible that dark matter is more evenly spread out in space.
According to the study published by the European Southern Observatory (ESO), the astronomers studied images from the Kilo Degree Survey (KiDS), taken by ESO’s VLT Survey Telescope (VST) in Chile, of an area of the sky covering a size about 2,200 times that of the full moon, and encompassing more than 15 million galaxies.
Refining Our Understanding
Using an innovative computer to analyze the images, the team was able to study a phenomenon known as cosmic shear — when light from distant galaxies is slightly warped by the gravitational effects of large amounts of matter, usually large-scale structures in the universe or the hidden dark matter. It’s a more subtle variant of weak gravitational lensing.
“This latest result indicates that dark matter in the cosmic web, which accounts for about one-quarter of the content of the Universe, is less clumpy than we previously believed,” Viola explained. This, however, runs contrary to the results of deductions using the European Space Agency’s (ESA) Planck satellite.
The disagreements between the two sets of data are not really that surprising. In fact, they’re quite expected given how newer technology enables us to refine our understanding of things — and there isn’t a thing bigger than the universe, our understanding of which needs considerable improvement.
“Our findings will help to refine our theoretical models of how the universe has grown from its inception up to the present day,” said Hildebrandt.
The universe is shrouded in mystery—a shroud so dark, in fact, that 27 percent of the matter in it is “dark.” Dark matter does not interact with photons and electromagnetic waves, so it’s invisible to our eyes and to every kind of telescope. Basically, it’s the darkness that surrounds every celestial body, and we only know that it’s there because astronomers observe its gravitational pull on everything else.
A working theory is that – in addition to the four fundamental forces that drive the universe: gravity, electromagnetism, and strong and weak nuclear forces – there’s a fifth force that rules the behavior of dark matter. Physicists from CERN now believe that this force is transmitted by a particle called the dark photon.
“To use a metaphor, an otherwise impossible dialogue between two people not speaking the same language (visible and dark matter) can be enabled by a mediator (the dark photon), who understands one language and speaks the other one,” explained Sergei Gninenko of CERN.
The research facility is now launching the NA64 experiment to search for this particle. The equipment focuses a beam of electrons with a known value of initial energy at a detector. Interactions between the electrons and atoms in the detector produce visible photons. If dark photons exist, they will escape the detector and subtract from the initial electron energy, as by the law of conservation of energy.
The Complex Universe
There’s a lot of work to be done by physicists in order to prove that dark photons exist. Results of the experiment must be replicable and, if the scientists find it, another round of research will be pursued to prove its relation to dark matter.
CERN is an organization of physicists and engineers that probe the universe in pursuit of understanding its fundamental structure. Discoveries from these studies could validate or totally destroy everything we currently know.
While dark matter may seem very far away from us and our daily lives, understanding all these mysteries is another step toward understanding ourselves and this complex universe we live in.