Scientists have used the Dark Energy Spectroscopic Instrument (DESI) to create the most detailed 3D map of the universe so far. The catalog includes over 7.5 million galaxies, more than all other redshift surveys combined. These kinds of maps are essential to unraveling the nature of the universe and its evolution. Particularly, scientists are interested in understanding dark energy, the mysterious force thought to be responsible for the accelerated expansion of the universe.
DESI consists of over 5,000 optical fibers mounted on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory in Arizona. These many fibers allow the instrument to capture detailed color spectrum images of millions of galaxies across more than a third of the sky. By breaking down the spectrum of colors, researchers can determine just how much the light has been redshifted — meaning how much it has been stretched toward the red end of the spectrum by the expansion of the universe.
American astronomer Edwin Hubble, after whom the famous Hubble Space Telescope is named, first linked the redshift phenomenon to the expansion of the universe in the 1920s, writing: “This redshift appeared to be larger for faint, presumably further, galaxies. Hence, the farther a galaxy, the faster it is receding from Earth.”
These redshifts allowed DESI to translate a flat observation of the sky into depth, which researchers use to create a 3D map of the universe. DESI has only been online for seven months — just 10% of the way through its five-year mission — but it has already surpassed in size and scope all other similar surveys before it.
By the time the DESI survey is completed, more than 35 million galaxies will have been mapped. The catalog will provide astronomers with copious amounts of data points, an intricate web of complexity that can reveal both the past and future movements of the universe.
“There is a lot of beauty to it,” said Berkeley Lab scientist Julien Guy during a Berkeley Lab-hosted webinar called CosmoPalooza. “In the distribution of the galaxies in the 3D map, there are huge clusters, filaments, and voids. They’re the biggest structures in the universe. But within them, you find an imprint of the very early universe, and the history of its expansion since then.”
“Our science goal is to measure the imprint of waves in the primordial plasma,” he added. “It’s astounding that we can actually detect the effect of these waves billions of years later, and so soon in our survey.”
Nearly 70% of the content of the universe is thought to be made of dark energy, a mysterious form of energy believed to drive the expansion of the universe at an accelerated rate. As the universe expands, more dark energy is created, which causes the universe to expand even faster — a self-perpetuating cycle that drives the expansion of the universe seemingly to infinity.
But can the universe truly expand infinitely? Or will it collapse onto itself in a reverse Big Bang (Big Crunch)? To answer such existential questions scientists need to know how dark energy has behaved in the past, which is where DESI comes in.
Until dark energy is demystified, DESI data can also advance science in other ways. For instance, cosmologists can use DESI’s maps to verify whether Einstein’s theory of general relativity holds over immense spans of space and time. DESI data is also allowing scientists to understand the behavior of intermediate-mass black holes that are otherwise impossible to spot using conventional telescopes. Quasars, some of the brightest and most distant objects in the universe, are also important targets for DESI.
“It’s pretty amazing,” said Ragadeepika Pucha, a graduate student in astronomy at the University of Arizona working on DESI. “DESI will tell us more about the physics of galaxy formation and evolution.”
During the 20th century, the idea that the Universe existed in a steady state was seriously challenged and eventually dismissed by the discovery that the Universe is not only expanding but is also doing so at an accelerating rate. The reason for this accelerating expansion is thus far unknown, but scientists have given this force a name–albeit one that is a placeholder–dark energy.
Explaining this accelerating rate of expansion has become one of the most challenging problems in cosmology. The fact that the value for this acceleration varies wildly between theory and practical observations has created a raft of problems in itself. This means that the net result arising from any attempt to explain dark energy creates more questions than it answers.
Dark Energy: The Basics
Dark energy is whatever is causing the expansion of the Universe to accelerate. One of the most striking things about this mysterious energy is just how much ‘stuff’ in the Universe it accounts for. If you consider the contents of the cosmos to be matter and energy –more formally known as the Universe’s mass-energy density–then dark energy accounts for between 68% to 72% of all cosmic ‘stuff.’
Dark matter is the second-largest contributor, with just a tiny proportion of the Universe’s ‘stuff’ made up of the baryonic matter consisting of atoms that we see around us on a day-to-day basis.
This is even more staggering when you consider that all the stars, planets, dust, gas and cosmic bodies that make up the visible Universe are contained in this tiny fraction of cosmic stuff that doesn’t even amount to 5% of the Universe’s contents.
Dark energy could very roughly be described as a force acting in opposition to gravity. Whereas the more familiar everyday force of gravity holds objects like planets and stars together in orbits, dark energy acts as a repulsive force, driving galaxies themselves apart. But, whereas gravity acts upon objects themselves, dark energy acts on the very fabric of spacetime between objects. Because dark matter is the largest contributor to gravity, this means this mysterious substance is locked in what has been termed a ‘cosmic tug of war.’ And it’s clear during our current epoch, dark energy is winning!
A popular analogy for this is the description of the Universe as the surface of a balloon. Galaxies are represented by two marker ink dots on this surface. As the balloon is inflated the points move apart with the very space between them expanding.
Repeat the experiment with three unevenly placed dots and it is clear that the dots that are initially further apart recede away from each other more rapidly. This extremely rough analogy carries over to galaxies. The further apart the galaxies are, the more quickly they recede.
An Expanding Surprise
The discovery that the Universe is expanding came as a considerable shock to the scientific community when it was confirmed by Edwin Hubble in 1929. Hubble had built upon theory provided by George Lemaitre and Alexander Friedman who had used the equations of general relativity to predict that the Universe was non-static, something that very much contradicted the scientific consensus of the time.
Albert Einstein who devised general relativity had also found that his geometric theory of gravity predicted a non-static Universe, something he wasn’t exactly comfortable with. Despite having already killed many of the sacred cows of physics, Einstein was unwilling to do away with the concept of a static Universe. To recover a static Universe that was neither expanding nor contracting, the world’s most famous scientist introduced to his equations a ‘fudge factor’ called the cosmological constant–commonly represented with the Greek letter lambda.
The cosmological constant was in danger from the start. Once Hubble managed to persuade Einstein that the Universe was indeed expanding, the physicist abandoned the cosmological constant, allegedly describing it as his ‘greatest blunder’ in his later years. The cosmological constant wouldn’t stay in the cosmological dustbin for very long, however.
If physicists had been surprised by the discovery at the beginning of the 20th Century that the Universe is expanding, they would be blown away when at the end of that same century when the observations of distant supernovae made by two separate teams of astronomers revealed that not only is the Universe expanding, it is doing so at an accelerating rate.
To understand why this is shocking and how it leads to the conclusion that some repulsive force is driving this expansion, it is necessary to journey to the very beginning of time… Let’s take some balloons too…
Escaping the Big Crunch
When thinking about the initial expansion of the Universe it makes sense to conclude that the introduction of an attractive force within that Universe would slow and eventually halt this expansion. That is exactly what gravity should do, and it seems did do during the early stages of expansion that had nothing to do with dark energy (we think).
Some cosmologists are willing to go a step further. If there is no outward pressure but an inward attractive force, shouldn’t the Universe actually start to contract?
This leads to the theory that the Universe will end in what physicists term the ‘Big Crunch’–an idea that dark energy could make obsolete. Think about how counter-intuitive this was to scientists when the idea was first suggested and evidenced. Let’s return to the balloon analogy; imagine you stop blowing into the balloon, and instead start sucking the air out of it.
How shocked would you be to find that the balloon isn’t contracting, it’s continuing to expand? And not just that, it’s actually expanding faster than it was when you were blowing into it!
With that in mind, consider the initial moments of the Universe. Beginning in an indescribably dense and hot state, squeezed into a quantum speck, the Universe undergoes a period of rapid expansion. This period of expansion wasn’t driven by dark energy. As it expands, the Universe cools allowing electrons to form atoms with protons and neutrons, which in turn frees photons to travel the cosmos.
Soon there is enough matter in the Universe to allow the attractive force of gravity to slow its expansion. And this does seem to be what happened in the early cosmos. The rapid inflation of the infant Universe is believed to have halted at around 10 -32 seconds after the Big Bang, with the Universe still expanding, albeit at a much slower rate.
This period of expansion continued to slow as a result of the growing dominance of matter during what cosmologists call the ‘matter-dominated epoch.’ But, at around 9.8 billion years into the Universe’s 13.8 billion year history, something strange begins to happen. The Universe begins to expand again, this time at an accelerating rate.
This is the dawn of the dark energy dominated epoch.
The Cosmological Constant is Back and Still Causing Trouble
That explains why the accelerating expansion of the Universe is so troubling and the need to introduce the placeholder concept of dark energy to explain it. Yet this accelerating expansion would still need a mathematical representation in equations used to describe the Universe. To do this cosmologists would return to the cosmological constant and its symbol, lambda.
This new iteration of the cosmological constant would be used in a different way to Einstein’s version. Whereas the earlier cosmological constant was used to balance gravity and hold the Universe steady and static, this new version would be used to overwhelm gravity and account for the acceleration of its expansion. But, this revised use of the cosmological constant does not mean it is any less troublesome than Einstein had found its predecessor.
In fact, the difference between the cosmological constant’s measured value, found by measuring the redshift of distant Type Ia supernovae, diverges from the value predicted by quantum field theory and particle physics by a value as large as 10121 (that’s 1 followed by 121 zeroes). Thus, it should come as no surprise that this value has been described as the worst prediction in the history of physics.
And as it represents the action of dark energy, that makes dark energy itself cosmology’s biggest conundrum.
OK… But What is Dark Energy?
So by now, you might well be thinking all of this is all fine and good, but this article specifically asks ‘what is dark energy?’ Isn’t it time to get to answering this question? It should come as no surprise that the answer is no one knows. But, that doesn’t mean that cosmologists don’t have some very good ideas.
One of the explanations for dark energy says that it could be vacuum energy, an underlying background energy that permeates that Universe and is represented by the cosmological constant. The most commonly cited evidence for vacuum energy–the energy of ’empty’ space which manifests as the Casimir effect.
Without delving too deeply into this, as relativity states that energy and mass are equivalent and mass has gravitational effects, then it stands to reason if empty space has vacuum energy, this too should contribute to the effect of gravity across the cosmos. That contribution has been factored in as a negative repulsive influence acting against the attractive influence of gravity.
The big problem with this is that quantum field theory suggests that this negative pressure contribution from vacuum energy should arise from all particles and thus, should give lambda a value that is tremendously larger than that obtain when our astronomers measure the redshift of Type Ia supernovae in distant galaxies.
This problem could be solved by dark energy’s effects being the result of something other than vacuum energy, of course. The Universe’s accelerating expansion could be due to some, as of yet undiscovered fundamental force of nature. Alternatively, it could indicate that our best current theory of gravity–general relativity– is incorrect.
A new generation of cosmologists is currently actively tackling the dark energy puzzle with new and revolutionary ideas. These include the idea that dark energy could have started work in the early Universe, an idea proposed by Early Dark Energy (EDE) models of the Universe. Another alternative is that dark energy does not influence the curvature of the Universe, or perhaps does so weakly–a theory referred to as the ‘well-behaved cosmological constant.’
As unsatisfying an answer as it is, the only honest way of addressing the question ‘what is dark energy?’ right now is by saying; we just don’t know. But, science wouldn’t be anywhere near as fascinating without mysteries to solve, and revolutionary ideas to be uncovered.
The Dark Energy Survey (DES) is an ambitious cosmological project that aims to map hundreds of millions of galaxies. In the process, the project will detail hundreds of millions of galaxies, observe thousands of supernovae, map the cosmic web that links galaxies, all with the aim of investigating the mysterious force that is causing the Universe to expand at an accelerating rate.
Using the 570-megapixel Dark Energy Camera on the National Science Foundation’s Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile, the DES has observed a map of galaxy distribution and morphology that stretches 7 billion light-years and captures 1/8 of the sky over Earth.
Now new results from the DES which collects the work of an international team of over 400 scientists from over 25 institutions from countries including the US, UK, France, Spain, Brazil, and Australia, are in. The findings are detailed in a ground-breaking series of 29 papers and comprises of data collected during the DES’ first three years of operation providing the most detailed description of the Universe’s composition and expansion to date.
The survey was conducted between 2013 to 2019 cataloging hundreds of millions of objects, with the three years of data covered in these papers alone containing observations of at least 226 million galaxies observed over 345 nights.
The fact that some of these galaxies are close to the Milky Way and others are much more distant–up to 7 billion light-years away– gives researchers an excellent picture of the evolution of the Universe over around half of its lifetime.
The results seem to confirm the standard model of cosmology, currently the best-evidenced theory of the Universe’s composition and evolution which suggests the Universe was created in a ‘Big Bang’ event and has a composition of 5% ordinary or baryonic matter, 27% dark matter, and 68% dark energy.
The snapshot of the Universe provided by the DES does seem to show that the Universe is less ‘clumpy’ than current cosmological models suggest, however.
Illuminating the Dark Universe
The fact that the ‘Dark Universe’ consists of 95% of the matter and energy in the known cosmos means that there are huge gaps in our understanding of the evolution of the Universe, its past, present, and its future.
These gaps include the nature of dark matter, whose gravitational influence holds galaxies together, and dark energy, the force that is expanding space between the galaxies driving them apart at an accelerating rate.
These effects seem to be in opposition, with one holding matter together and the other working upon space itself to drive matter apart. And it is this cosmic struggle that shapes the Universe which the DES aimed to investigate.
There are two key phenomena which the survey used to do this. Studying ‘the cosmic web’ that links galaxies together in clusters and loose associations gives hints at the distribution and influence of dark matter.
The second phenomenon used by the DES is the bending of light as it travels past curvatures in spacetime created by objects of tremendous mass like galaxies. This effect predicted by Einstein’s theory of gravity–general relativity–is known as ‘gravitational lensing.’
The DES relied on a form of this effect called ‘weak gravitational lensing’ to assess how dark matter is distributed across the Universe, thus inferring its ‘clumpiness.’
The data collected by the DES was cross-referenced against measurements carried out by the European Space Agency (ESA) operated mission, the Planck observatory. The orbiting observatory, which operated between 2009 and 2013 and studied the cosmic background radiation (CMB)–an imprint leftover from an event shortly after the Big Bang in which electrons and protons connected thus allowing photons to travel freely for the first time.
Observing the CMB reveals conditions that were ‘frozen in’ to it at the time of this event known as the last scattering and thus gives a detailed picture of the Universe when it was just 400 thousand years old for the DES team to draw from.
Setting the Scene for Future Surveys
The DES intensely studied ten regions labeled as ‘deep fields’ which were repeatedly imaged during the course of the survey. These images were stacked which allowed astronomers to observe distant galaxies.
In addition to allowing researchers to see further into the Universe and thus further back in time, information regarding redshift– an increase in wavelength caused by objects receding which can arise as a result of the Universe’s expansion–taken from these deep fields was used to calibrate the rest of the survey. This constituted a major step forward for cosmic surveys providing the researchers with a picture of the Universe painted with stunning precision.
Whilst the DES was concluded in 2019, the sheer wealth of data collected by the survey requires a huge amount of computing power and time to assess. This is why we are only seeing the first three years of observations reported and likely means that the DES still has much more to deliver.
This will ultimately set the scene for the Legacy Survey of Space and Time (LSST) which will be conducted at the Vera C Rubin observatory–currently under construction on the El Penon peak of Cerro Pachon in northern Chile.
Whereas the DES surveyed an inarguably impressive 1/8 of the sky over the earth, the wide-field camera that will conduct the LSST will capture the entire sky over the Southern hemisphere, meaning it will view half of the entire sky over our planet.
A major part of the LSST’s mission will be the investigation of dark matter and dark energy, meaning that when the data from the DES is finally exhausted and its secrets are revealed, a worthy successor will be waiting in the wings to assume its mission of discovery.
A cleverly designed experiment takes us one step closer to a fundamental truth — but there’s still a long way to go.
When something is called “dark energy”, it’s bound to be mysterious and weird, but dark energy is really weird. For starters, we don’t even know what is.
It seems counterintuitive, but our universe is expanding. Not only is it expanding, but this expansion is also accelerating — which seems really bizarre, as you’d expect gravity to slowly clump things closer together. Dark energy is believed to be the reason behind this acceleration.
It seems to permeate all the space in the universe and it’s very homogenous, but it only interacts with the gravitational force and is extremely rarefied, which makes it extremely difficult to study and analyze. This leaves the question “so what is it” very much on the table, with no satisfying answer.
Some physicists have proposed that dark energy is a fifth fundamental force — adding to the well-known gravity, electromagnetic, weak nuclear and strong nuclear forces. This hypothesis has been put to the test by researchers at Imperial College London and the University of Nottingham.
If this were the case and dark energy was a force, you’d expect it to be some sort of repulsive force, something that makes the universe “larger“. To test this, the experiment worked on single atoms, using a device called an atom interferometer. This detects any extra force which might be acting on the atom. The experimental setup featured a small metal sphere placed in a vacuum chamber, with atoms freefalling through the chamber.
In theory, if dark energy was a fifth force, it would be weaker when there is more matter around. So in this design, the freefalling atoms would change paths ever so slightly as they passed by the sphere. However, this turned out to not be the case. The atoms continued unabated as they passed the sphere, essentially ruling out the idea that dark energy is a fundamental force.
This does more than just rule out one possibility — it helps constrain the cosmological models attempting to describe dark energy. Professor Ed Copeland, from the Centre for Astronomy & Particle Physics at the University of Nottingham, explains:
“This experiment, connecting atomic physics and cosmology, has allowed us to rule out a wide class of models that have been proposed to explain the nature of dark energy, and will enable us to constrain many more dark energy models.”
The fact that this experiment is relatively simple but helps to reveal one of the fundamental truths of the universe makes it all the more remarkable, researchers say.
“It is very exciting to be able to discover something about the evolution of the universe using a table-top experiment in a London basement,” said Professor Ed Hinds of the Department of Physics at Imperial.
Map of dark matter in region G12 of the sky. Credit: KiDS survey.
Dark matter and dark energy make up 95% of the observable universe despite the fact that none of our instruments are capable of detecting it. What’s up with that? Scientists would sure like to know as well, although that doesn’t mean they’re completely in the dark. According to one of the most exciting researches on dark matter to date, this elusive form of matter may combine with dark energy to form a fluid with ‘negative mass’.
What does negative mass even mean, you might ask? It’s another a weird thing that physicists have constructed in order to explain even weirder phenomena. A hypothetical type of matter with negative mass would also have negative gravity, which means it would repel other matter around it. Likewise, if you’d push an object with negative mass, it would accelerate towards you.
Just like normal matter, negative mass would become spread out as the universe expands. But our observations suggest that dark energy does not thin out over time, which means it shouldn’t be negative mass. For this reason, many cosmologists have abandoned the idea of associating negative mass with dark energy.
Dr. Jamie Farnes from the University of Oxford is of a different opinion. The scientist has proposed a modification to Einstein’s theory of general relativity that allows negative masses to not only exist, but to be created continuously. This way, both dark matter and dark energy can be unified into a single fluid. When more and more negative mass is being added, the fluid does not dilute during the expansion of the universe.
“We now think that both dark matter and dark energy can be unified into a fluid which possesses a type of ‘negative gravity,” repelling all other material around them. Although this matter is peculiar to us, it suggests that our cosmos is symmetrical in both positive and negative qualities,” Dr. Farnes said in a statement.
Farnes seems to be on to something. His work is not some purely theoretical work either. For instance, the model can predict the observed behavior of dark matter halos — the invisible fabric that keeps galaxies from tearing themselves apart. The video below shows a simulation created by Farnes which predicts how dark matter halos form with properties just like the ones inferred from observations by modern radio telescopes.
What’s more, negative mass isn’t purely theoretical either. Air bubbles in water can be modeled to have negative mass and, quite recently, scientists were able to generate particles that behave exactly as they would if they had negative mass.
[panel style=”panel-info” title=”Dark matter and dark energy” footer=””]Dark matter cannot be detected by our instruments, i.e. it’s completely invisible. Yet scientists know that it must exist because of the gravitational force it exerts on the surrounding matter that we can measure. Dark energy is the repulsive force that is responsible for the expansion of the universe at an accelerating rate.
Until now, the two have been treated separately. Now, Dr. Farnes claims that both are part of the same phenomenon — a unified dark fluid of negative mass. [/panel]
Albert Einstein actually provided the first hint of a dark universe 100 years ago when he introduced a parameter in his equations known as ‘cosmological constant.’ Today, this parameter has become synonymous with dark energy, but Einstein always thought that it represents a failure on his behalf. In some of his notes, Einstein stated that ‘a modification of the theory is required such that “empty space” takes the role of gravitating negative masses which are distributed all over the interstellar space.” So, one might say that Einstein was the first to predict a negative-mass-filled universe.
“Previous approaches to combining dark energy and dark matter have attempted to modify Einstein’s theory of general relativity, which has turned out to be incredibly challenging. This new approach takes two old ideas that are known to be compatible with Einstein’s theory—negative masses and matter creation—and combines them together,” Dr. Farnes said.
“The outcome seems rather beautiful: dark energy and dark matter can be unified into a single substance, with both effects being simply explainable as positive mass matter surfing on a sea of negative masses.”
The new study might help solve some dicey problems in String Theory, which hopes to unify quantum physics with general relativity, but which is also plagued by inconsistencies with observational evidence. One of the tenets of string theory is that energy in empty space must be negative, which fits beautifully with the idea of a negative mass dark fluid. What’s more, a dark fluid could also explain why the Hubble constant — the relationship between the speed and the distance of a galaxy — seems to vary. A negative mass cosmology actually predicts that the Hubble constant should vary, which wouldn’t make it a constant at all, obviously.
Dr. Farnes’ theory will be tested with more scrutiny by the Square Kilometre Array (SKA), the world’s largest telescope. SKA’s main goal will be to measure the distribution of galaxies throughout the history of the universe
“If real, it would suggest that the missing 95% of the cosmos had an aesthetic solution: we had forgotten to include a simple minus sign,” the scientist concluded.
Scientific reference: J. S. Farnes. A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified LambdaCDM framework, Astronomy & Astrophysics (2018). DOI: 10.1051/0004-6361/201832898 , https://arxiv.org/abs/1712.07962
Writing in the journal Acta Astronautica, neuropsychologists Gabriel de la Torre and Manuel García, from the University of Cádiz, say that when it comes to detecting alien signals, we might be looking in the wrong direction. They say that we’re looking for aliens that act similarly to us when that might really not be the case.
“When we think of other intelligent beings, we tend to see them from our perceptive and conscience sieve; however we are limited by our sui generis vision of the world, and it’s hard for us to admit it,” says De la Torre, who prefers to avoid the terms ‘extraterrestrial’ or aliens by its Hollywood connotations and uses more generic terms, such as ‘non-terrestrial’.
“What we are trying to do with this differentiation is to contemplate other possibilities,” he says “for example, beings of dimensions that our mind cannot grasp; or intelligences based on dark matter or energy forms, which make up almost 95% of the universe and which we are only beginning to glimpse. There is even the possibility that other universes exist, as the texts of Stephen Hawking and other scientists indicate.”
The awareness test that inspired the study. Try to count the number of basketball passes. Did you also catch something out of the ordinary?
Hardwired to miss it
In order to test their hypothesis, they had 137 people distinguish aerial photographs with artificial structures (such as buildings or roads) from others with natural elements (such as mountains or rivers). In one of the images, a tiny character disguised as a gorilla was inserted to see if the participants noticed. As expected, participants tended to miss the gorilla. It’s normal because we’re hardwired to miss it — we’re looking for something else. Similarly, if we’re looking for a specific kind of signal, we might completely miss an unrelated type of signal, one we weren’t expecting.
“If we transfer this to the problem of searching for other non-terrestrial intelligences, the question arises about whether our current strategy may result in us not perceiving the gorilla,” stresses the researcher, who insists: “Our traditional conception of space is limited by our brain, and we may have the signs above and be unable to see them. Maybe we’re not looking in the right direction.”
In another example presented in the article, researchers showed participants an apparently geometric structure that can be seen in the images of Occator — an impact crater of the dwarf planet Ceres, famous for its bright spots. Inside the crater appears a strange structure, looking like a square inside a triangle. The point researchers were trying to make is that we sometimes see patterns that just aren’t there, due to the way our brains are wired.
“Our structured mind tells us that this structure looks like a triangle with a square inside, something that theoretically is not possible in Ceres,” says De la Torre, “but maybe we are seeing things where there are none, what in psychology is called pareidolia.”
Image Credits: NASA / JPL-CaltechClose
But the opposite might also be happening, they say. We might have the signal right in front of our eyes, and simply miss it — kind of like a cosmic gorilla effect.
Types of civilizations
We’re not really sure what to expect in terms of potentially advanced alien species, but the most commonly used scale is the Kardashev scale, proposed by Russian astrophysicist Nikolai Kardashev. The scale has three main categories, and it focuses on different stages of energy capture and use, which seems to be a vital requirement for an advanced species:
A Type I civilization (a planetary civilization) can use and store all of the energy which reaches its planet from the parent star.
A Type II civilization (a stellar civilization) can harness the total energy of its planet’s parent star and use it on a planet.
A Type III civilization (a galactic civilization) can control energy on the scale of its entire host galaxy.
If you’ll look at it closely, you’ll see that humans aren’t really even on a Type I level yet, so the Kardashev scale has been extended, both upwards and downwards, including:
A Type 0 civilization (humans) that harvests a significant part of its planet energy, just not yet to its full potential.
A Type IV civilization (a universal civilization) that can control energy on the scale of the entire universe. This is already a virtually indestructible civilization. This hypothetical civilization would be able to interact with and harvest dark matter and dark energy.
A type V civilization (a multiversal civilization) — this already steps into the realm of metaphysics and assumes there is more than one universe, and a civilization that’s able to span and populate several universes.
A type VI civilization (deities) that would have the ability to interact with universes outside of time and space, similar in concept to an absolute deity.
Already, it’s becoming quite clear that we don’t even know how to understand very advanced alien civilizations, assuming that they exist. We might be able to understand a Type 0, I, or II civilization, assuming that they do share some similarities with us. But should we come across the higher levels of civilization, would we even realize what we’re looking at? This is what de la Torre and Garcia are asking. For all we know, dark matter and dark energy might hold the traces of such an advanced civilization. Of course, the researchers themselves admit the inherent shortcomings when you’re classifying something you know nothing about.
“We were well aware that the existing classifications are too simplistic and are generally only based on the energy aspect. The fact that we use radio signals does not necessarily mean that other civilizations also use them, or that the use of energy resources and their dependence are the same as we have,” the researchers point out, recalling the theoretical nature of their proposals.
The duo also proposes a different civilization scale, with 3 types. Type 1 is essentially ours, ephemeral, vulnerable to a planetary cataclysm, either natural or self-made. Type 2 is characterized by the longevity of its members, able to explore galaxies and overall much more durable. Type 3, as you’d expect, would be constituted by exotic creatures with eternal or near-eternal life, with an absolute dominion over the universe.
Naturally, this is all a bit speculative. We don’t really know whether we’re looking for the right thing or not, we don’t even know if there is a right thing or not. How likely are we to miss an alien signal, in the case that it exists? Impossible to tell right now. So this study definitely goes a bit ‘out there’, but it poses some intriguing questions.
If anything, the main takeaway is that we should perhaps take a step back and reconsider what alien life might look like. In other words, we shouldn’t only be counting the passes — we should keep an eye out for any gorillas.
Journal Reference: Gabriel G. De la Torre, Manuel A. Garcia. The cosmic gorilla effect or the problem of undetected non terrestrial intelligent signals. Acta Astronautica, 2018; 146: 83 DOI: 10.1016/j.actaastro.2018.02.036
The image above is a timeline with each frame showcasing a stage in our Universe’s evolution, from humble beginning to present date (left to right), as simulated by the Argonne National Laboratory. Called the Q Continuum simulation, this is the most complete cosmological simulation to date covering a volume of 1300 Mpc on a side (one Mpc = 3.08567758 × 1022 meters) where half a trillion particles evolved for a mass resolution of ~1.5×108 Msun.
The Q Continuum basically imitates the evolution of our universe over the last 13.8 billion years, using data fed by latest generation of high-fidelity sky surveys and crunching it into models of the universe that are larger, higher-resolution, and more statistically accurate than any that have come before. The ultimate goal of these simulations is to unravel the fundamental origin of the universe and nature of dark matter and dark energy. The two are undetectable directly, but together make up 95% of all matter in the Universe. It’s an immense challenge, but work like this is what might finally lead to a breakthrough.
Halo particles in the Q Continuum simulation at z = 0. Shown are a sub-sample of 1% of all particles in halos of mass and above. Halos with less than 500 particles are represented by 5 particles. The first image (left upper corner) shows the full volume; the inset box volume is shown in the next image (upper middle) and so on. The series of images zooms into one of the very largest clusters in the simulation, shown in the last two images (lower panels, middle and right). Overall, approximately 46% of all particles reside in halos with 100 or more particles at z = 0.
This simulation was carried out on Titan, a GPU-CPU system located at Oak Ridge Leadership Computing Facility which is currently the second fastest machine in the world. As you might imagine, it was so intense that it used up 90% of the full machine to achieve the high mass resolution in a large cosmological volume. You can read more about the simulation in the published paper.
This is the first map in a series of maps that will be stitched together to form a grand picture of how dark matter is distributed across the Universe. Dark matter is basically invisible, which is why it’s called dark in the first place, so scientists rely on indirect observations like the gravitational effects it poses to locate and map it. What we’re seeing now is only 3% of the area of sky that the Dark Energy Survey (DES) will document over its slated five-year-long mission.
The map traces the distribution of dark matter across a portion of the sky. The color scale represents projected mass density: red and yellow represent regions with more dense matter. Image: Dark Energy Survey
The map was created using one of the world’s most powerful digital cameras, the Dark Energy Camera, a 570-megapixel imaging device mounted on the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The image processing was handled the National Center for Supercomputing Applications at the University of Illinois in Urbana-Champaign.
Because it doesn’t emit or absorb light, dark matter is virtually invisible to our direct astronomical observations. Despite being so elusive, it accounts however for roughly a quarter of all the substances in the universe. There’s a trick though. By studying gravitational lensing – the distortion that occurs when the gravitational pull of dark matter bends light around distant galaxies – scientists can basically infer where dark matter hot spots are located and map them. This is useful since we can now compare dark matter with visible matter, and test models and cosmological theories. One such theory suggests, for instance, that galaxies form where there’s a greater concentration of dark matter, and hence stronger gravity.
“We measured the barely perceptible distortions in the shapes of about 2 million galaxies to construct these new maps,” said Vinu Vikram of Argonne National Laboratory. “They are a testament not only to the sensitivity of the Dark Energy Camera, but also to the rigorous work by our lensing team to understand its sensitivity so well that we can get exacting results from it.”
Preliminary DES data, like this map, lends credence to the idea of galaxies forming around dark matter clusters. Large filaments of matter along which visible galaxies and galaxy clusters lie and cosmic voids where very few galaxies reside, but only follow-up studies that will probe deeper and in more details will be able to tell us more.
“Our analysis so far is in line with what the current picture of the universe predicts,” said Chihway Chang, another of the lead scientists who is with ETH Zurich. “Zooming into the maps, we have measured how dark matter envelops galaxies of different types and how together they evolve over cosmic time. We are eager to use the new data coming in to make much stricter tests of theoretical models.”
Dark matter and black holes are some of the most mysterious things in the Universe, so a connection between the two is absolutely thrilling. In a new study, astronomers report a strange link between the amount of dark matter in a galaxy and the size of its supermassive black hole. That’s an amazing new black hole fact!
Artist rendition of a supermassive black hole. Image via Red Orbit
Most galaxies have a black hole at their centers – millions or even billions times heavier than our Sun. The origin of supermassive black holes remains an open question, with several competing hypothesis being put forth. The bigger the galaxy is, the bigger and heavier the black hole is… but why does this even happen? Why are the two connected? A new study of football-shaped collections of stars called elliptical galaxies suggests that the key here may be dark matter – the mysterious “thing” which makes up for most of the mass in the Universe. So, an amazing new
“There seems to be a mysterious link between the amount of dark matter a galaxy holds and the size of its central black hole, even though the two operate on vastly different scales,” says lead author Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics (CfA).
Dark matter is really strange – we don’t know what it is and we can’t see it. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the Universe. In other words, we can’t see it, but we can see its effects… and we pretty much have no idea what it is. It’s one of the biggest mysteries of astrophysics, especially when you consider that dark matter outweighs normal matter 6 times.
To investigate the surprising link between dark matter and black holes, Bogdan and his team studied more than 3,000 elliptical galaxies. They used star motions as a tracer to weigh the galaxies’ central black holes and conducted X-Ray measurements to weigh the dark matter halo. The more dark matter a galaxy has, the more hot gas it can hold onto and the bigger halo it has. They found that the more dark matter a galaxy has, the bigger its black hole tends to be – even more so than the logical connection between a black hole and the galaxy’s stars.
It’s not clear exactly why this happens, but the likely explanation is connected to the way a galaxy grows. There are several types of galaxies, the most common ones being elliptical galaxies (smooth, featureless light distributions and appear as ellipses in images), spiral galaxies (consist of a flattened disk, with stars forming a spiral structure) and lenticular galaxies (consist of a bright central bulge surrounded by an extended, disk-like structure but, unlike spiral galaxies, the disks of lenticular galaxies have no visible spiral structure).
Elliptical galaxies form when two smaller galaxies merge, with their stars, planets and black holes mingling together. Because the dark matter is heavier than everything else, it molds the formation and development of the new galaxy, even from the outskirts to the central black hole.
“In effect, the act of merging creates a gravitational blueprint that the galaxy, the stars and the black hole will follow in order to build themselves,” explains Bogdan.
The teacup galaxy. Red/yellow shows the radio emission “bubbles”, blue shows the gas and the bright yellow in the centre shows where the jets are driving into the gas. Image via CNET.
This study, which was conducted on the Teacup Glaaxy, might also provide information about black hole formation and development in galaxies – something on which we have very little information.
“This particular piece of work on the Teacup Galaxy has provided new insight into how the black holes [drive energy] in ordinary galaxies,” Harrison said. “They appear to be capable of driving jets of charged particles that collide into the gas. You could imagine the ‘jet’ as like a water cannon being driven into a crowd of people – the water cannon collides with the crowd and causes it to break up and disperse rapidly. In this analogy, the crowd represents the gas in the galaxy that is trying to form stars, but is destroyed by the jet.”
The fact that our galaxy also has a supermassive black hole at its center further gives astronomers study material. In fact, there may be significant similarities between the Milky Way and the Teacup Galaxy (aside for their beverage names).
“There is a supermassive black hole at the center of our Milky Way,” Harrison added. “There is now good evidence that this black hole has driven large amounts of energy into the galaxy in the past, through the so-called ‘Fermi Bubbles,’ as well as other evidence. It is likely that billions of years ago the Milky Way was forming stars much more rapidly and the black hole may have played a role in shutting this down. However, this is not well understood. It is worth pointing out that the galaxies where we believe supermassive black holes have had the most influence are ‘dead’ with little-to-no stars forming. In contrast, the Milky Way is still forming stars (around one per year).”
Researchers have created a new model that applies our latest understanding of quantum mechanics to Einstein’s theory of general relativity and this is what they came up with – it’s truly hard to wrap your mind around that.
Currently accepted theories state that the Universe is around 13.8 billion years old, and before that everything in existence was squished into a tiny point – also known as the singularity – so incredibly compact that it contained everything that eventually became the Universe (actually, this is pretty hard to wrap your mind as well). As the Big Bang took place, the Universe started to expand, and it is expanding faster and faster to this day.
Image via AMNH.
The problem with current theories is that the math breaks down when you start to analyze what happened during or before the Big Bang.
“The Big Bang singularity is the most serious problem of general relativity because the laws of physics appear to break down there,” co-creator of the new model, Ahmed Farag Ali from Benha University and the Zewail City of Science and Technology, both in Egypt, told Lisa Zyga from Phys.org.
Working in a team which included Sauya Das at the University of Lethbridge in Alberta, he managed to create a new satisfying model in which the Big Bang never occurred, and the Universe simply existed forever.
“In cosmological terms, the scientists explain that the quantum corrections can be thought of as a cosmological constant term (without the need for dark energy) and a radiation term. These terms keep the Universe at a finite size, and therefore give it an infinite age. The terms also make predictions that agree closely with current observations of the cosmological constant and density of the Universe.”
According to this model, the Universe also has no end, which is perhaps even more interesting if you think about it, and that it is filled with a quantum fluid, which might be composed of gravitons – hypothetical particles that have no mass and mediate the force of gravity.
The model shows great promise, but it has to be said – it’s only a mathematical theory at this point. We don’t have the physics to back it up or prove it wrong at the moment, and we likely won’t have it in the near future. Still, it’s remarkable that it solves so many problems at once, and the conclusions are very intriguing.
“It is satisfying to note that such straightforward corrections can potentially resolve so many issues at once,” Das told Zyga.
A newly published study has revealed that dark matter is being swallowed up by dark energy, offering valuable data not only about the nature and structure of these mysterious entities, but also about the future of the Universe.
Artistic representation of dark matter. Image credits: tchaikovsky2, Deviant Art
In case you’re wondering, dark matter and dark energy are not Star Trek concepts – they’re real forms of energy and matter; at least that’s what most astrophysicists claim. Dark matter is a kind of matter hypothesized in astronomy and cosmology to account for gravitational effects that appear to be the result of invisible mass. The problem with it is that it cannot be directly seen with telescopes, and it neither emits nor absorbs light or other electromagnetic radiation at any significant level. It is believed that it does not react with light in any way; the only reason we know about it is that we see its effects. Basically, astronomers have consistently observed something causing a gravitational attraction, so therefore there has to be some matter with mass causing the attraction. They coined the term dark matter, and we still don’t really know what it’s made of.
Meanwhile, dark energy is a hypothetical form of energy which permeates all of space and tends to accelerate the expansion of the universe. Basically, ever since the 1990s, observations have revealed that the Universe is expanding at an accelerating rate. This baffled researchers; ok, it’s clear that it expands, but why is it expanding faster? If anything, it should expand slower, due to all the gravitational attraction. Well, dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. The evidence for dark energy is indirect, just like with dark matter. Dark energy is thought to be very homogeneous, not very dense and have a negative pressure (acting repulsively) in order to explain the observed acceleration of the expansion of the universe.
Image via Discover Magazine.
According to modern measurements, on a mass–energy equivalence basis, the observable universe contains 26.8% dark matter, 68.3% dark energy (for a total of 95.1%) and 4.9% ordinary matter. So everything we know (humans and animals, planets, stars and galaxies) amounts for some 5% of the known Universe – the rest, the huge 95% is made out of dark energy and dark matter – something we still don’t know much about. Naturally, physicists and astronomers are trying to figure out how the two react with ordinary matter and with themselves.
Energy eats matter
Researchers in Portsmouth and Rome have made a stunning discovery, showing that dark matter is being slowly erased, swallowed up by dark energy. Professor David Wands, Director of Portsmouth’s Institute of Cosmology and Gravitation and one of the research member said:
“This study is about the fundamental properties of space-time. On a cosmic scale, this is about our Universe and its fate. If the dark energy is growing and dark matter is evaporating we will end up with a big, empty, boring Universe with almost nothing in it. Dark matter provides a framework for structures to grow in the Universe. The galaxies we see are built on that scaffolding and what we are seeing here, in these findings, suggests that dark matter is evaporating, slowing that growth of structure.”
Interestingly enough, there is no proposed mechanism to how or why this happens. What this type of study shows is that the Standard Model is no longer sufficient to explain all the interactions taking place at a cosmological scale. In other words, we’re missing something pretty important.
Research students Valentina Salvatelli and Najla Said from the University of Rome worked in Portsmouth with Dr Marco Bruni and Professor Wands, and with Professor Alessandro Melchiorri in Rome examined data from several surveys to reach this conclusion. Professor Wands said:
“Valentina and Najla spent several months here over the summer looking at the consequences of the latest observations. Much more data is available now than was available in 1998 and it appears that the standard model is no longer sufficient to describe all of the data. We think we’ve found a better model of dark energy.”
The Universe is expanding at an accelerated rate, something which we are still struggling to understand. Image via Wiki Commons.
The models seem to support these claims; the fact that the Universe is accelerating, but at a slower pace than expected (following 90s observations) also seems to support their hypothesis.
“Since the late 1990s astronomers have been convinced that something is causing the expansion of our Universe to accelerate. The simplest explanation was that empty space – the vacuum – had an energy density that was a cosmological constant. However there is growing evidence that this simple model cannot explain the full range of astronomical data researchers now have access to; in particular the growth of cosmic structure, galaxies and clusters of galaxies, seems to be slower than expected.”
The community still hasn’t had a coherent reaction, but initial reviews seem to be positive. Professor Dragan Huterer, of the University of Michigan feels that other researchers should take not of these findings, and include them in future models and theories.
“The paper does look very interesting. Any time there is a new development in the dark energy sector we need to take notice since so little is understood about it. I would not say, however, that I am surprised at the results, that they come out different than in the simplest model with no interactions. We’ve known for some months now that there is some problem in all data fitting perfectly to the standard simplest model.”
To me, the fact that we can do so much, and yet know so little about 95% of the Universe we live in is stunning. There’s still so much to learn, and so much we have yet to understand. It’s a great time to be a scientist!
Journal Reference: Valentina Salvatelli, et al., “Indications of a Late-Time Interaction in the Dark Sector,” Physical Review Letters, 113, 181301, 30 October 2014; doi:10.1103/PhysRevLett.113.181301
The Illustris project took 5 years of software development and 3 months running on 8000 processors – but it sure was worth it – the result is truly monumental! Now, researchers finally have an accurate model of the development of the universe, which even though is rough around some edges, still blends in well with today’s accepted science, and even makes some valuable predictions.
The Illustris project
Stellar light distributions (g,r,i bands) for a sample of galaxies at z = 0
The vast majority of our Universe is made out of dark energy and dark matter – something which we can’t see directly. Everything we know about them, we infer from indirect observations. Testing this extraordinary scenario requires precise predictions for the formation of structure in the visible matter, the things we can see – stars, galaxies, black holes. Astrophysicists think of these visible elements as organized in a ‘Cosmic Web’ of sheets, filaments, and voids, embedded with the basic units of the cosmic structure: galaxies.
Basically, what Illustris set out to do was project a set of large-scale cosmological simulations, including galaxy formation – one of the more complex processes in the Universe. This was the best model of galaxy formation developed to date, taking into consideration the expansion of the universe, the gravitational pull of matter onto itself, the motion or “hydrodynamics” of cosmic gas, as well as the formation of stars and black holes. The model also takes into consideration the fact that many conditions changed since the early days of the Universe, and also adds that into the fray. Their simulated volume contains tens of thousands of galaxies captured in high-detail, covering a broad range of masses, shapes, sizes and rates of star formation, and apply the properties observed in real life.
Illustris simulation overview poster. Shows the large scale dark matter and gas density fields in projection (top/bottom). The lower three panels show gas temperature, entropy, and velocity at the same scale.
But this model isn’t only a projection of what we already know – it can help us learn new things as well. However, the main problem here, before we start making deductions based on this model, is ensuring that it is an actual reflection of reality – and with the immense complexity and numerical calculations involved, that’s a hard thing to do. Naturally, this leads to the need for some sort of simplification. For starters, some processes, such as the birth of individual stars, cannot be directly captured in a cosmological simulation. But even if you look at just the larger picture, everything has to fit in with the observed data – and while there are still some corrections to be made, in the grand scheme of things, Illustris fits things almost perfectly.
The main achievements of the project
It successfully reproduces a wide range of observable properties of galaxies and the relationships between these properties. A key element here is the so-called “specific star formation rate” – the rate of new stars being formed in a galaxy, divided by the amount of already-existing stars; it fits with the observed values not just for this period, but for all ages throughout the history of the Universe.
It precisely measured the gas content of the universe, and where it resides. Furthermore, where data does not exist, the model can make predictions about the evolution of the gas. Outside of individual galaxies, Illustris also predicts that at the present time, the majority of gas (~81%) remains in the “intergalactic medium” (the space between galaxies), but that this gas contains only a minority (~34%) of the metals so-far produced in the universe.
It investigated “satellite galaxies” and their connection to cosmological evolution. Satellite galaxies are galaxies which revolve around bigger galaxies, much like a planet revolves around its star. Illustris also studied the changes in internal structure as galaxy populations evolve in time, the impact of gas on the structure of dark matter, and it can even produce “mock observations”.
For more information, be sure to check out their website (one of the best presentations I’ve ever seen), which also features several videos:
1 – Time evolution of a 10Mpc (comoving) region within Illustris from the start of the simulation to z=0. The movie transitions between the dark matter density field, gas temperature (blue: cold, green: warm: white: hot), and gas metallicity.
4 – Time evolution of a 10Mpc (comoving) cubic region within Illustris, rendered from outside. The movies shows on the left the dark matter density field, and on the right the gas temperature (blue: cold, green: warm: white: hot). The rapid temperature fluctuations around massive haloes are due to radiative AGN feedback that is most active during quasar phases. The larger ‘explosions’ are due to radio-mode feedback.
7 – Time evolution from high redshift to z=0, demonstrating the formation of a massive elliptical ‘red-and-dead’ galaxy as a result of a multiple merger around z~1. Panels show stellar light (left) and gas density (right) in a region of 1 Mpc on a side.
Scientists have been analyzing high-energy gamma rays originating from the center of our galaxy and they’ve reported that there’s a good chance that at least some of them come from dark matter. This is the best indication of dark matter to ever be found.
What is dark matter?
Artistic representation of dark matter. There is no indication that dark matter is tangled like this.
Think about our universe for a moment – what is it made of? “Well I don’t know”, you might say, “stuff? Stars, planets, all that?”. Mmm, as it turns out, you’d be pretty off with that answer. Planets, stars, and everything that we call matter only makes up 5% of the Universe – that’s what the current understanding is. As for that 95%, dark energy is 68%, and dark matter is the rest, almost 27% – and we don’t know what those things are. We just know they’re there because we see their effects, but we don’t really know what they are. Dark energy is a hypothetical form of energy that permeates all of space and is believed to accelerate the expansion of the universe. But here, we’re more interested in dark matter.
To put it simply, dark matter is the thing which causes some gravitational effects and can’t be explained with anything else. It cannot be seen directly with telescopes; evidently it neither emits nor absorbs light or other electromagnetic radiation. Scientists can’t “see” or detect it directly in any way, but they observed some consistent gravitational effects where there shouldn’t be any gravity; the existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe.
Detecting dark matter
Using data collected from NASA’s Fermi Gamma-ray Space Telescope, scientists from different institutions generated maps of the center of the galaxy. They found that some of the gamma-ray radiations can’t be explained through any known mechanism. It’s not just that they eliminated all the possible causes, they were still stuck with some radiation, and said “hey, look, this must be dark matter”. But then again… it’s not far off from that either.
The thing is, if dark matter particles with a particular mass are destroying each other, this would be a remarkable fit for the remaining emission. There is no real direct evidence to this, but there’s a lot of indirect indications. However, astronomers still warn that there might be other, currently unknown sources.
Elliott Bloom, a member of the Fermi collaboration, underlines that at this point, this can’t be confirmed or refuted as dark matter, but if they find a similar, stronger signal, that could confirm it.
“If we ultimately see a significant signal, it could be a very strong confirmation of the dark matter signal claimed in the galactic center.”
Artist impression of BOSS map, complete with a view of the intergalactic ‘ruler’. (c) BOSS
A new map of a slice of the Universe was recently released by BOSS – Baryon Oscillation Spectroscopic Survey – and it’s the most accurate and comprehensive one so far. The map plots the location of some 1.2 million galaxies with an astonishing accuracy of 99%, nothing short of spectacular – remember, each of these objects is trillions of miles away from each other. The practical applications of an accurate map of the Universe are numerous. Most importantly, it helps paint a better picture of how the Universe formed and how it looks like in its present form. For instance, the findings suggest the Universe is flat and infinite.
“There are not many things in our daily lives that we know to 1% accuracy,” said Prof David Schlegel, a physicist at Lawrence Berkeley National Laboratory and the principal investigator of BOSS.
“I now know the size of the universe better than I know the size of my house.
“Twenty years ago astronomers were arguing about estimates that differed by up to 50%. Five years ago, we’d refined that uncertainty to 5%; a year ago it was 2%.
“One percent accuracy will be the standard for a long time to come.”
To measure the size of the Universe (not THE Universe, just a chunk of it), researchers studied baryon acoustic oscillations (BAOs). These are waves of particles and energy that were release all over the Universe since the Big Bang and continue to do so to this day – like the ripples in a water pond. Because baryon waves move at a constant speed, they’re extremely useful to scientists for referencing purposes. In fact, they’re seen as a sort of intergalactic ruler – one that measures 490 million light years in this case.
BOSS data is acquired by the 2.5m Sloan telescope at Apache Point Observatory in New Mexico. (c) SDSS
With an accurate map, you can tell a lot about how the Universe works and even how it looks like. For instance, the findings tell us that the Universe is probably flat. Not 2-D flat, of course. Think of how people used to think the world is flat. Because the curvature of the Earth can’t be seen from a fixed point on its surface, people would genuinely assume that world is flat, because that was what a false intuition based on their perception and perspective was telling them. In the Universe’s case, scientists have yet to observe a sort of loop. If the Universe wasn’t flat, and it was curved instead, then if you’d continue to travel in a straight direction you’d eventually end up in the same point you’ve started from.
Being relatively flat suggests dark energy in the Universe is constant. If it were to vary in space and time, then we’d have seen a more curved Universe.
The BOSS map also tells us that the Universe is likely infinite, extending forever in space and time. The analysis is 90% complete so far, and an upcoming version of the BOSS map will be even more accurate, projected to include high-quality spectra of 1.3 million galaxies, plus 160,000 quasars and thousands of other astronomical objects, covering 10,000 square degrees.
The results were reported in a paper published on the Arxiv website.
Mysterious and elusive, dark matter has escaped scientists time and time again; yet confirming its existence is quintessential to current efforts of studying the Universe. With this in mind, detecting dark matter has become one of the foremost goals in the physics of the 21st century. An experiment at MIT, called DarkLight, aims to prove or disprove a certain theory that provides a possible solution to uncovering dark matter by creating its constituent bosons in the lab.
Dark matter is said to make about 23% of the mass-energy density of the universe, in comparison to only 4% normal matter (the matter we can observe), while the rest of the mass-energy density is comprised of dark energy. Dark matter makes up more than half of the total mass of most galaxies, including our own Milky Way, and is known to extend well beyond the visible stars. If models are correct, than dark matter is ubiquitous, even in our solar system yet detecting it has proved to be a herculean challenge. Since it was first proposed in the 1930s, numerous theories have tried to account for and provide ways of identifying dark matter. So far there have been no confirmed identifications of dark matter with any known — or postulated — candidate.
Photograph of the prototype constructed by the GEM-TPC collaboration. (C) MIT
One piece of the puzzle is currently being investigated by the DarkLight experiment at MIT. The experiment seeks to prove or disprove a theory which says dark matter is made up of bosons in the 10 MeV to 10 GeV range – heavy photons dubbed A′ (pronounced “A-prime”). The exact mass of such a particle (if it exists) is unknown.
DarkLight will use Jefferson Lab’s Free Electron Laser to bombard an Oxygen target with a stream of high energy electrons with one megawatt of power, and hopefully create this form of theorized dark matter (A’ particles). Studying the resonance peak at the A′ mass in the electron-positron invariant mass spectrum would provide the valuable clues necessary to prove or disprove the presence of dark matter through this experiment.
It might take a while before this will happen though. According to the report released by MIT, it will take a couple of years before the DarkLight experimental rig will become operational and another couple of years of smashing electrons to collect data before any conclusive ideas can be drawn.
Dark energy is the mysterious force that drives the Universe’s expansion at an ever increased pace. Probing and understanding this force is thus imperative for astronomers’ and cosmologists’ efforts of peering through the Universe’s secrets. Recently, a new massive project set on probing the nature of dark energy was launched, called the Dark Energy Survey (DES), and its future findings are already regarded in great promise.
The Dark Energy Camera photographs galaxies from its perch on the Blanco telescope in Chile. (c) Reidar Hahn/Fermilab
DES’ centerpiece is its 570-megapixel digital camera (pictured), capable of imaging 300 million galaxies over one-eighth of the clear night sky from up atop the the 4-metre Blanco telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes. Galaxies and galaxy clusters are its main target since these are the brightest objects in the night’s sky and the camera’s high resolution capability can be most efficient. You see, to probe dark energy, the astronomers will measure weak gravitational lensing – the phenomenon in which incoming light from distant galaxies is skewed and distorted by matter between the galaxies and the point of observation (Earth).
Although measuring weak lensing is difficult, the researchers are confident this can be achieved. How is this important? Well, by measuring the degree of lensing, astronomers can infer and map the matter in between galaxies and Earth. This allow them in turn to create a three-dimensional web that can reveal the fingerprints of dark energy through time. A similar effort to DES has already been operation for quite a while – the Japanese Hyper Suprime-Cam in Hawaii, which relies on an even more detailed, 870-megapixel camera. Although Hyper Suprime can image fainter galaxies, DES can cover a wider patch of the sky. Together, the researchers hope these two projects will help paint a more accurate picture.
Besides weak lensing, DES will also be used to count galaxy clusters and measure their distance away from Earth, and spot distant supernovae, whose otherwise reference light is dimmed as the universe expands. The latter are of great importance since this is how the theory of an accelerating Universe was formed, netting the authors of the paper a Nobel prize in 2011.
Bono of U2 recently let it be known that he was a student of astrophysics (yes, truly!). Upon meeting the 2012 Nobel Prize winner for physics Brian Schmidt, Bono demonstrated a thorough understanding of Schmidt’s work on the evidence for an accelerating universe.
More and more over the last 100 years, scientists have been theorising about the very beginning of the universe – most of us have heard of the Big Bang – and also theorising about how it will end. These theories relate to lengths of time, and concepts that are so removed from the battles of our day to day ordinary lives that there is a kind of disconnect, and as a result we find it hard to understand how these theories could possibly be relevant to our lives. It was the late Douglas Adams’ genius to be able to identify this gulf and turn it into comedy gold, which he did in his famous ‘Hitchhiker’s Guide to the Galaxy’ books.
photo via rfplreads.wordpress.com
For example, thinking that the end of the universe would really be something to see, Adam’s imagination promptly put a restaurant there, right on the edge of the universe’s end, thinking that diner’s would be drawn to the spectacle. He called the restaurant Milliway’s, and patrons from all over the universe came to come to enjoy the view (while they enjoyed a pleasant meal at a reasonable price!).
However, to astrophysicists imagining how the universe must end is a matter of great importance. Brian Schmidt, Saul Perlmutter and Adam Riess’s recent Nobel prizes were awarded for work that showed the universe is not only expanding but that it is expanding at an accelerating rate. Up until recently it was thought that the rate of expansion of the universe must be slowing – which would seem a reasonable assumption given that gravity from the denser, middle part of the universe should be pulling on the matter out toward the edges, and having a braking effect.
However Schmidt and co’s calculations show that instead of contracting, the universe is actually expanding at an ever increasing rate. If they are right the implication is that the universe will eventually be so spread out it will be a very lonely place indeed: “Human beings will look to an empty universe in 100 billion years, as all the galaxies will fade away except the Milky Way we live in,” said Schmidt. It should be noted that such an outcome would not bode well for Milliway’s.
The reason for this acceleration remains shrouded in mystery. Scientists employ the concept of ‘dark matter’ to explain it, although it turns out that what dark matter actually is is shrouded in mystery.
Schmidt said, “We don’t know how dark energy is generated. It seems to be a part of the fabric of space itself. So dark energy makes more space, and more space makes more dark energy, which then makes more space. The universe runs away because of the stuff.” It is not too much of a stretch to describe dark energy as a construction of convenience – something to fill the gaps in our understanding, just as it theoretically fills the gaps in the universe.
Whatever dark matter actually is, its influence isn’t confined to galaxies – it has also influenced previous theories that once held favour, which have now been consigned to the wastebasket because of it. The Big Crunch is one notable casualty.
The Big Crunch was where the outward momentum from the Big Bang was finally arrested by gravity’s influence, and things then started to contract. Slowly at first, then faster and faster until, well…there is a big crunch.
It is a pity that the Big Crunch looks unlikely, because others had speculated that the Big Crunch might very well lead to another Big Bang. Adherents of this theory know it as the Big Bounce – a name that Adams would have been hard pressed to improve on.
Biology would appear to be a long way from astrophysics, but there is a new breed of biologists who posit that the law of physics known as negative entropy is a process that governs not only the development of galaxies but is behind the phenomenon of life as well (the physicist Erwin Schrödingerintroduced the concept of negentropy in his 1944 book What is Life?).
Negative entropy is where open systems progress toward ever greater order by using energy from outside their system. Thinkers as disparate as Teilhard de Chardin, Ilya Prigogine, Paul Davies and Jeremy Griffith see its influence operating at both ends of the spectrum: from the formation of galaxies, to the stirrings of life.
However the biologist that stands out from this group is the Australian Jeremy Griffith. While Griffith agrees that negative entropy is fundamental to understanding what life is, he is the only one to draw attention to the obvious disparity between this progression toward order in open systems, and the behaviour of humanity, namely humanity’s propensity to destructiveness, or less order. Indeed Griffith says “the real frontier for the human race–and most particularly for its designated vehicle for enquiry, science.” The real frontier, he says “was never outer space but inner space, the search for understanding of the human condition.” He also suggests that understanding the ‘human condition’, our historical state of insecurity at being unable to reconcile the so-called good and evil within, is a necessary first step in allowing us to think effectively about all manner of things, saying that “finding understanding of our less-than-ideally-behaved, troubled condition is the crucial insight we need… [which will] enable us to safely entertain deeper thoughts on life, in particular thoughts such as what is life all about, [and] what is the meaning of life.”.
So while outer space certainly has some romance and excitement about it, and the thought of sitting in Milliway’s looking out over the edge of the abyss, with galaxies whirling to their death in the background, sure does give a tingle down the spine, it is in fact an avoidance of the real issue which is our own less-than-ideal behaviour. Beneath the humour of Douglas Adams was an acute awareness of the truth of what Griffith says, that without understanding ourselves first, everything else is folly.
Most certainly, one of the top goals in physics today is proving the existence of dark matter – the elusive form of matter that makes up 85% of all matter in the Universe. Many theories have been proposed and tested, however to this day we only have glimpses and possible hints of dark matter. A newly proposed theory claims dark matter is constructed of particles that have an abnormal, donut-shaped electromagnetic field known as an anapole. The proposal was then analyzed thoroughly by a pair of theoretical physicists at Vanderbilt University: Professor Robert Scherrer and post-doctoral fellow Chiu Man Ho. Their results seem to back-up the theory; a theory that is so elegant in its simplicity that it might actually be true.
Dark matter, as the name implies, is impossible to detect in normal conditions since it doesn’t absorb or emit light or energy. In fact, astronomical observations have basically ruled out the possibility that dark matter particles carry electrical charges. How do we know it exists then? Well, just because we can’t “see” dark matter, it doesn’t mean it’s not there. Observations have found there are consisting anomalies in the rotational rate of galactic clusters or that the rate that stars rotate around individual galaxies is similarly out of sync. Clearly there’s a dramatic gravitational effect that can not be accounted to normal matter, and as such the abstract concept of “dark matter” serves as the best explanation we have at the moment for these anomalies.
“There are a great many different theories about the nature of dark matter. What I like about this theory is its simplicity, uniqueness and the fact that it can be tested,” said Scherrer.
Comparison of an anapole field with common electric and magnetic dipoles. The anapole field, top, is generated by a toroidal electrical current. As a result, the field is confined within the torus, instead of spreading out like the fields generated by conventional electric and magnetic dipoles. (Michael Smeltzer / Vanderbilt)
Scherrer and Ho suggest that dark matter may be constructed of a type of basic particle known as the Majorana fermion – a type of particle like the electron and quark, which are the basic building blocks of matter. The particle’s existence was predicted in the 1930′s, however so far it has eluded detection in particle accelerators.
The Majorana is of great interest to physicists because it’s been predicted to be electrically neutral. This is important to note since dark matter don’t contain electrical charges, but might possess electric or magnetic dipole. In their paper, Scherrer and Ho have shown that these Majorana fermions are uniquely adapted to have an anapole, which causes the particles to have properties that vary from those of particles that have the more common fields possessing two poles. This would serve to explain why the particles are so hard to detect.
“Most models for dark matter assume that it interacts through exotic forces that we do not encounter in everyday life. Anapole dark matter makes use of ordinary electromagnetism that you learned about in school — the same force that makes magnets stick to your refrigerator or makes a balloon rubbed on your hair stick to the ceiling,” said Scherrer. “Further, the model makes very specific predictions about the rate at which it should show up in the vast dark matter detectors that are buried underground all over the world. These predictions show that soon the existence of anapole dark matter should either be discovered or ruled out by these experiments.”
According to Ho, “fundamental symmetries of nature” prevent Majorana fermions from obtaining any electromagnetic properties except the anapole. Particles with familiar electrical and magnetic dipoles, interact with electromagnetic fields even when they are stationary. Particles with anapole fields don’t. They must be moving before they interact and the faster they move the stronger the interaction. As a result, anapole particles would have been have been much more interactive during the early days of the universe and would have become less and less interactive as the universe expanded and cooled. Because dark matter is moving so much more slowly at the present day, and because the anapole interaction depends on how fast it moves, these particles would have escaped detection so far, but only just barely.
The researchers’ findings were reported in a paper published in the journal Physics Letters B.
Hubble just never ceases to surprise. The latest astronomical find discovered using the ever resourceful space telescope is a never before encountered double ring pattern known as an Einstein ring. This very rare pattern is the result of a peculiar optical alignment in which three galaxies are perfectly aligned with each other, like beads on a string. The occurrence isn’t just a silly optical trick in space – studying it, astronomers can learn more about dark matter and dark energy, and even the curvature of the Universe.
The phenomenon that gave rise to this peculiar observation is known as gravitational lensing, in which the light emitted by a galaxy in the background gets bent by the gravitational pull of a massive galaxy in the foreground. In our case, one could say we have a double gravitational lens on our hands since a third massive galaxy lies in the foreground. When two galaxies are exactly lined up, the light gets twisted in such a fashion that it forms a shape that resembles a circle, called Einstein’s ring. When three of them are perfectly lined up, such as the case, two concentric rings form.
“Such stunning cosmic coincidences reveal so much about nature. Dark matter is not hidden to lensing,” added Leonidas Moustakas of the Jet Propulsion Laboratory in Pasadena, California, USA. “The elegance of this lens is trumped only by the secrets of nature that it reveals.“
The odds of such a phenomenon being observable from Earth’s vantage point are so dim, that the discovery can be considered nothing short of jackpot! In fact, the team of astronomers led by Raphael Gavazzi and Tommaso Treu of the University of California, Santa Barbara were extremely lucky to spot it in the first place. SLACS team member Adam Bolton of the University of Hawaii’s Institute for Astronomy in Honolulu first identified the lens in the Sloan Digital Sky Survey (SDSS). “The original signature that led us to this discovery was a mere 500 photons (particles of light) hidden among 500,000 other photons in the SDSS spectrum of the foreground galaxy,” commented Bolton.
The geometry of the two rings allowed the researchers to establish the mass of the middle galaxy precisely to be a value of 1 billion solar masses – a dwarf galaxy. This is actually the first time a dwarf galaxy’s mass was measured at cosmological distance. The comparative radius of the rings could also be used to provide an independent measure of the curvature of space by gravity.
The results were reported at the 211th meeting of the American Astronomical Society in Austin, Texas, USA. A paper has been submitted to The Astrophysical Journal.
Renowned physicist, famous for his study of black holes, galaxies and for authoring a popular book on the origin of the universe, “A Brief History of Time”, recently arrived at Caltech, like every year, where he held a talk in front of 1,000 people who had waited in line for 12 hours to hear him speak. Hawking’s talk, as always, encompassed discussions pertaining to questions like “why are we here?” , “how did the universe came to be?” and such.
Hawking began his talk with an African creation myth, but didn’t stray too far from his theological intro. The physicist noted, possibly in irritation, how some people seeking to find a divine solution to the creation of the Universe prefer to counter the theories of curious physicists with poor arguments. Rather rash or not, he said “What was God doing before the divine creation? Was he preparing hell for people who asked such questions?”
As you can imagine, this stirred a few people in the audience and many more hearing about it on the web. People should have gotten used to this, however. The pope himself picked on Hawking on several occasions for his alleged disdainful claims against god. A few years ago, I wrote a piece on ZME where I also quoted some of Hawking’s answers to questions pertaining to divinity, like the afterlife. Back then, he asserted there is no heaven, nor hell, but nothingness.
How did the Universe came to be? What triggered the Big Bang? Hawking’s talk continued on with discussions relating to various creation theories some still standing, other long debunked by recent findings made possible with modern space telescopes. One of these debunked theories is Fred Hoyle and Thomas Gold’s steady-state theory which held that there isn’t actually a head and a tail to all of this and that space bodies like galaxies, the stars that comprise them are made out of spontaneously formed matter.
Hawking also says that the Big Bang occurred at a moment of singularity, as he and physicist Roger Penrose proved in the 1980s the universe could not “bounce” when it contracted, as had been theorized, and that most likely the Big Bang happened only once. Recent refined measurements that position the Universe’s age at roughly 13.8 billion years are on par with Hawking’s model. Still, what would be a valid theory for the Universe’s inception according to Hawking? He believes the “M-theory”, a hypothesis that is based on ideas first moved forward by lifelong Caltech lecturer Richar Feynman, as the single most valid model he has currently encountered that can explain what he has observed. In fine line, the theory – an extension to string theory – states multiple universes are formed out of nothing. Only a few are capable of creating conditions for supporting life, and even much fewer conditions for intelligent life similar to humans.
Dark matter‘s discovery, which along with dark energy combine to amount to 95% of all matter making the normal matter that can be seen and observed only 5%, is seen by Hawking as the next barrier physics needs to breach. After understanding the nature of dark matter and dark energy, many of today’s missing links could be put together and physicists may finally be able to paint an accurate picture of cosmos. Dark energy, physicists believe, would explain why the universe is expanding at an ever-growing rate instead of collapsing under its own gravity.
“There have been searches for dark matter, but so far no results,” he said. We presume, however, that he is up to date with recent reports from experiments both in space and undergrounds labs where hints suggesting the detection of dark matter have been sighted.
Hawking has been living dreadful disease – Lou Gherig’s disease – for the past 50 years which has deteriorated his motor neurons leaving him unable to move his limbs or any body part for that matter. At the time of his diagnosis he was told he would live for only two more years.