# We Live in a Flat Universe

Cosmologists generally agree that our universe is flat. But how exactly can that be for our 3-dimensional selves and everything else for that matter? Well, first it’s useful to note that the flatness is a property of geometry, and not topology. So, even though it’s flat, the universe could be folded and/or twisted in any number of different, esoteric ways.

From Space:

The universe is flat. But there’s a lot of subtlety packed into that innocent-looking statement. What does it mean for a 3D object to be “flat”? How do we measure the shape of the universe anyway? Since the universe is flat, is that…it? Is there anything else interesting to say?

Oh yes, there is.

First, we need to define what we mean by flat. The screen you’re reading this on is obviously flat (I hope), and you know that the Earth is curved (I hope). But how can we quantify that mathematically? Such an exercise might be useful if we want to go around measuring the shape of the whole entire universe. [The History & Structure of the Universe (Infographic)]

One answer lies in parallel lines. If you start drawing two parallel lines on your paper and let them continue on, they’ll stay perfectly parallel forever (or at least until you run out of paper). That was essentially the definition of a parallel line for a couple thousand years, so we should be good.

Let’s repeat the exercise on the surface of the Earth. Start at the equator and draw a couple parallel lines, each pointing directly north. As the lines continue, they never turn left or right but still end up intersecting at the North Pole. The curvature of the Earth itself caused these initially parallel lines to end up not-so-parallel. Ergo, the Earth is curved.

The opposite of the Earth’s curved shape is a saddle: on that surface, lines that start out parallel end up spreading apart from each other (in swanky mathematical circles this is known as “ultraparallel”).

Image: The shape of the universe depends on its density. If the density is more than the critical density, the universe is closed and curves like a sphere; if less, it will curve like a saddle. But if the actual density of the universe is equal to the critical density, as scientists think it is, then it will extend forever like a flat piece of paper. Courtesy: NASA/WMAP Science team.

# The Accelerated Acceleration

Until the mid-1990s accepted scientific understanding of the universe held that the cosmos was expanding. Scientists have accepted this since 1929 when Edwin Hubble‘s celestial observations showed that distant galaxies were all apparently moving away from us.

But, in 1998 two independent groups of cosmologists made a startling finding. The universe was not only expanding, its expansion was accelerating. Recent studies show that this acceleration in the fabric of spacetime is actually faster than first theorized and observed.

And, nobody knows why. This expansion, indeed the accelerating expansion, remains one of our current great scientific mysteries.

Cosmologists, astronomers and theoreticians of all stripes have proposed no shortage of possible explanations. But, there is still scant observational evidence to support any of the leading theories. The most popular revolves around the peculiar idea of dark energy.

From Scientific American:

Our universe is flying apart, with galaxies moving away from each other faster each moment than they were the moment before. Scientists have known about this acceleration since the late 1990s, but whatever is causing it—dubbed dark energy—remains a mystery. Now the latest measurement of how fast the cosmos is growing thickens the plot further: The universe appears to be ballooning more quickly than it should be, even after accounting for the accelerating expansion caused by dark energy.

Scientists came to this conclusion after comparing their new measurement of the cosmic expansion rate, called the Hubble constant, to predictions of what the Hubble constant should be based on evidence from the early universe. The puzzling conflict—which was hinted at in earlier data and confirmed in the new calculation—means that either one or both of the measurements are flawed, or that dark energy or some other aspect of nature acts differently than we think.

“The bottom line is that the universe looks like it’s expanding about eight percent faster than you would have expected based on how it looked in its youth and how we expect it to evolve,” says study leader Adam Riess of the Space Telescope Science Institute in Baltimore, Md. “We have to take this pretty darn seriously.” He and his colleagues described their findings, based on observations from the Hubble Space Telescope, in a paper submitted last week to the Astrophysical Journal and posted on the preprint server arXiv.

One of the most exciting possibilities is that dark energy is even stranger than the leading theory suggests. Most observations support the idea that dark energy behaves like a “cosmological constant,” a term Albert Einstein inserted into his equations of general relativity and later removed. This kind of dark energy would arise from empty space, which, according to quantum mechanics, is not empty at all, but rather filled with pairs of “virtual” particles and antiparticles that constantly pop in and out of existence. These virtual particles would carry energy, which in turn might exert a kind of negative gravity that pushes everything in the universe outward.

Image: The universe’s accelerated expansion. Courtesy: NASA and ESA.

# Searching for Signs of Life

Surely there is intelligent life somewhere in the universe. Cosmologists estimate that the observable universe contains around 1,000,000,000,000,000,000,000,000 planets. And, they calculate that our Milky Way galaxy alone contains around 100 billion planets that are hospitable to life (as we currently know it).

These numbers boggle the mind and beg a question: how do we find evidence for life beyond our shores? The decades long search for extraterrestrial intelligence (SETI) pioneered the use of radio telescope observations to look for alien signals from deep space. But, the process has remained rather rudimentary and narrowly focused. The good news now is that astronomers and astrobiologists have a growing toolkit of techniques that allow for much more sophisticated detection and analysis of the broader signals of life — not just potential radio transmissions from an advanced alien culture.

From Quanta:

Huddled in a coffee shop one drizzly Seattle morning six years ago, the astrobiologist Shawn Domagal-Goldman stared blankly at his laptop screen, paralyzed. He had been running a simulation of an evolving planet, when suddenly oxygen started accumulating in the virtual planet’s atmosphere. Up the concentration ticked, from 0 to 5 to 10 percent.

“Is something wrong?” his wife asked.

“Yeah.”

The rise of oxygen was bad news for the search for extraterrestrial life.

After millennia of wondering whether we’re alone in the universe — one of “mankind’s most profound and probably earliest questions beyond, ‘What are you going to have for dinner?’” as the NASA astrobiologist Lynn Rothschild put it — the hunt for life on other planets is now ramping up in a serious way. Thousands of exoplanets, or planets orbiting stars other than the sun, have been discovered in the past decade. Among them are potential super-Earths, sub-Neptunes, hot Jupiters and worlds such as Kepler-452b, a possibly rocky, watery “Earth cousin” located 1,400 light-years from here. Starting in 2018 with the expected launch of NASA’s James Webb Space Telescope, astronomers will be able to peer across the light-years and scope out the atmospheres of the most promising exoplanets. They will look for the presence of “biosignature gases,” vapors that could only be produced by alien life.

They’ll do this by observing the thin ring of starlight around an exoplanet while it is positioned in front of its parent star. Gases in the exoplanet’s atmosphere will absorb certain frequencies of the starlight, leaving telltale dips in the spectrum.

As Domagal-Goldman, then a researcher at the University of Washington’s Virtual Planetary Laboratory (VPL), well knew, the gold standard in biosignature gases is oxygen. Not only is oxygen produced in abundance by Earth’s flora — and thus, possibly, other planets’ — but 50 years of conventional wisdom held that it could not be produced at detectable levels by geology or photochemistry alone, making it a forgery-proof signature of life. Oxygen filled the sky on Domagal-Goldman’s simulated world, however, not as a result of biological activity there, but because extreme solar radiation was stripping oxygen atoms off carbon dioxide molecules in the air faster than they could recombine. This biosignature could be forged after all.

The search for biosignature gases around faraway exoplanets “is an inherently messy problem,” said Victoria Meadows, an Australian powerhouse who heads VPL. In the years since Domagal-Goldman’s discovery, Meadows has charged her team of 75 with identifying the major “oxygen false positives” that can arise on exoplanets, as well as ways to distinguish these false alarms from true oxygenic signs of biological activity. Meadows still thinks oxygen is the best biosignature gas. But, she said, “if I’m going to look for this, I want to make sure that when I see it, I know what I’m seeing.”

Meanwhile, Sara Seager, a dogged hunter of “twin Earths” at the Massachusetts Institute of Technology who is widely credited with inventing the spectral technique for analyzing exoplanet atmospheres, is pushing research on biosignature gases in a different direction. Seager acknowledges that oxygen is promising, but she urges the astrobiology community to be less terra-centric in its view of how alien life might operate — to think beyond Earth’s geochemistry and the particular air we breathe. “My view is that we do not want to leave a single stone unturned; we need to consider everything,” she said.

As future telescopes widen the survey of Earth-like worlds, it’s only a matter of time before a potential biosignature gas is detected in a faraway sky. It will look like the discovery of all time: evidence that we are not alone. But how will we know for sure?

Image: Artist’s Impression of Gliese 581 c, the first terrestrial extrasolar planet discovered within its star’s habitable zone. Courtesy: Hervé Piraud, Latitude0116, Xhienne. Creative Commons Attribution 2.5.

# A Googol Years From Now

If humanity makes it the next few years and decades without destroying itself and the planet, we can ponder the broader fate of our universal home. Assuming humanity escapes the death of our beautiful local star (in 4-5 billion years or so) and the merging of our very own Milky Way and the Andromeda galaxy (around 7-10 billion years), we’ll be toast in a googol years. Actually, we and everything else in the cosmos will be more like a cold, dark particle soup. By the way, a googol is a rather large number — 10100. That gives us plenty of time to fix ourselves.

From Space:

Yes, the universe is dying. Get over it.

Well, let’s back up. The universe, as defined as “everything there is, in total summation,” isn’t going anywhere anytime soon. Or ever. If the universe changes into something else far into the future, well then, that’s just more universe, isn’t it?

But all the stuff in the universe? That’s a different story. When we’re talking all that stuff, then yes, everything in the universe is dying, one miserable day at a time.

You may not realize it by looking at the night sky, but the ultimate darkness is already settling in. Stars first appeared on the cosmic stage rather early — more than 13 billion years ago; just a few hundred million years into this Great Play. But there’s only so much stuff in the universe, and only so many opportunities to make balls of it dense enough to ignite nuclear fusion, creating the stars that fight against the relentless night.

The expansion of the universe dilutes everything in it, meaning there are fewer and fewer chances to make the nuclear magic happen. And around 10 billion years ago, the expansion reached a tipping point. The matter in the cosmos was spread too thin. The engines of creation shut off. The curtain was called: the epoch of peak star formation has already passed, and we are currently living in the wind-down stage. Stars are still born all the time, but the birth rate is dropping.

At the same time, that dastardly dark energy is causing the expansion of the universe to accelerate, ripping galaxies away from each other faster than the speed of light (go ahead, say that this violates some law of physics, I dare you), drawing them out of the range of any possible contact — and eventually, visibility — with their neighbors. With the exception of the Andromeda Galaxy and a few pathetic hangers-on, no other galaxies will be visible. We’ll become very lonely in our observable patch of the universe.

The infant universe was a creature of heat and light, but the cosmos of the ancient future will be a dim, cold animal.

The only consolation is the time scale involved. You thought 14 billion years was a long time? The numbers I’m going to present are ridiculous, even with exponential notation. You can’t wrap your head around it. They’re just … big.

For starters, we have at least 2 trillion years until the last sun is born, but the smallest stars will continue to burn slow and steady for another 100 trillion years in a cosmic Children of Men. Our own sun will be long gone by then, heaving off its atmosphere within the next 5 billion years and charcoaling the Earth. Around the same time, the Milky Way and Andromeda galaxies will collide, making a sorry mess of the local system.

At the end of this 100-trillion-year “stelliferous” era, the universe will only be left with the … well, leftovers: white dwarves (some cooled to black dwarves), neutron stars and black holes. Lots of black holes.

Welcome to the Degenerate Era, a state that is as sad as it sounds. But even that isn’t the end game. Oh no, it gets worse. After countless gravitational interactions, planets will get ejected from their decaying systems and galaxies themselves will dissolve. Losing cohesion, our local patch of the universe will be a disheveled wreck of a place, with dim, dead stars scattered about randomly and black holes haunting the depths.

The early universe was a very strange place, and the late universe will be equally bizarre. Given enough time, things that seem impossible become commonplace, and objects that appear immutable … uh, mutate. Through a process called quantum tunneling, any solid object will slowly “leak” atoms, dissolving. Because of this, gone will be the white dwarves, the planets, the asteroids, the solid.

Even fundamental particles are not immune: given 10^34 years, the neutrons in neutron stars will break apart into their constituent particles. We don’t yet know if the proton is stable, but if it isn’t, it’s only got 10^40 years before it meets its end.

With enough time (and trust me, we’ve got plenty of time), the universe will consist of nothing but light particles (electrons, neutrinos and their ilk), photons and black holes. The black holes themselves will probably dissolve via Hawking Radiation, briefly illuminating the impenetrable darkness as they decay.

After 10^100 years (but who’s keeping track at this point?), nothing macroscopic remains. Just a weak soup of particles and photons, spread so thin that they hardly ever interact.

In case, you’ve forgotten, a googol is 10100 (10 to the power of 100) or 10 followed by 100 zeros. And, yes, that’s how the company Google derived its name.

# See, Earth is at the Center of the Cosmos

A single image of the entire universe from 2012 has been collecting lots of attention recently. Not only is it beautiful, it shows the Earth and our solar system clearly in the correct location — at the rightful center!

Some seem to be using this to claim that the circa 2,000 year old, geo-centric view of the cosmos must be right.

Well, sorry creationists, flat-earthers, and followers of Ptolemy, this gorgeous image is a logarithmic illustration.

Image: Artist’s logarithmic scale conception of the observable universe with the Solar System at the center, inner and outer planets, Kuiper belt, Oort cloud, Alpha Centauri, Perseus Arm, Milky Way galaxy, Andromeda galaxy, nearby galaxies, Cosmic Web, Cosmic microwave radiation and Big Bang’s invisible plasma on the edge. Courtesy: Pablo Carlos Budassi / Wikipedia.

# The Emperor and/is the Butterfly

In an earlier post I touched on the notion proposed by some cosmologists that our entire universe is some kind of highly advanced simulation. The hypothesis is that perhaps we are merely information elements within a vast mathematical fabrication, playthings of a much superior consciousness. Some draw upon parallels to The Matrix movie franchise.

Follow some of the story and video interviews here to learn more of this fascinating and somewhat unsettling idea. More unsettling still: did our overlord programmers leave a backdoor?

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Video: David Brin – Could Our Universe Be a Fake? Courtesy of Closer to Truth.

# It’s Official — Big Rip Coming!

The UK’s Daily Telegraph newspaper just published this article, so it must be true. After all, the broadsheet has been a stalwart of conservative British journalism since, well, the dawn of time, some 6,000 year ago.

Apparently our universe will end in a so-called Big Rip, and not in a Big Freeze. Nor will it end in a Big Crunch, which is like the Big Bang in reverse. The Big Rip seems to be a rather calm and quiet version of the impending cosmological apocalypse. So, I’m all for it. I can’t wait… 22 billion years and counting.

From the Daily Telegraph:

A group of scientists claim to have evidence supporting the Big Rip theory, explaining how the universe will end – in 22 billion years.

Researchers at Vanderbilt University in Nashville, Tennessee, have discovered a new mathematical formulation that supports the Big Rip theory – that as the universe expands, it will eventually be ripped apart.

“The idea of the Big Rip is that eventually even the constituents of matter would start separating from each other. You’d be seeing all the atoms being ripped apart … it’s fair to say that it’s a dramatic scenario,” Dr Marcelo Disconzi told the Guardian.

Scientists observed distant supernovae to examine whether the Big Rip theory, which was first suggested in 2003, was possible.

The theory relies on the assumption that the universe continues to expand faster and faster, eventually causing the Big Rip.

“Mathematically we know what this means. But what it actually means in physical terms is hard to fathom,” said Dr Disconzi.

Conflicting theories for how the universe will end include the Big Crunch, whereby the Big Bang reverses and everything contracts, and the Big Freeze, where as the universe slowly expands it eventually becomes too cold to sustain life.

Previous questions raised over the Big Rip theory include explaining how sticky fluids – that have high levels of viscosity – can travel faster than the speed of light, defying the laws of physics.

However, the Vanderbilt team combined a series of equations, including some dating back to 1955, to show that viscosity may not be a barrier to a rapidly expanding universe.

“My result by no means settles the question of what the correct formulation of relativistic viscous fluids is. What it shows is that, under some assumptions, the equations put forward by Lichnerowicz have solutions and the solutions do not predict faster-than-light signals. But we still don’t know if these results remain valid under the most general situations relevant to physics,” Dr Disconzi told the New Statesman.

Image: Cementerio de Polloe, en Donostia-San Sebastián, 2014. Courtesy of Zarateman. Public domain.

# Active SETI

Seventy years after the SETI (Search for Extra-Terrestrial Intelligence) experiment began some astronomers are thinking of SETI 2.0 or active SETI. Rather than just passively listening for alien-made signals emanating from the far distant exoplanets these astronomers wish to take the work a bold step further. They’re planning to transmit messages in the hope that someone or something will be listening. And that has opponents of the plan rather worried. If somethings do hear us, will they come looking, and if so, then what? Will the process result in a real-life The Day the Earth Stood Still or Alien? And, more importantly, will they all look astonishingly Hollywood-like?

From BBC:

Scientists at a US conference have said it is time to try actively to contact intelligent life on other worlds.

Researchers involved in the search for extra-terrestrial life are considering what the message from Earth should be.

The call was made by the Search for Extra Terrestrial Intelligence institute at a meeting of the American Association for the Advancement of Science in San Jose.

But others argued that making our presence known might be dangerous.

Researchers at the Seti institute have been listening for signals from outer space for more than 30 years using radio telescope facilities in the US. So far there has been no sign of ET.

The organisation’s director, Dr Seth Shostak, told attendees to the AAAS meeting that it was now time to step up the search.

“Some of us at the institute are interested in ‘active Seti’, not just listening but broadcasting something to some nearby stars because maybe there is some chance that if you wake somebody up you’ll get a response,” he told BBC News.

The concerns are obvious, but sitting in his office at the institute in Mountain View, California, in the heart of Silicon Valley, he expresses them with characteristic, impish glee.

##### Game over?

“A lot of people are against active Seti because it is dangerous. It is like shouting in the jungle. You don’t know what is out there; you better not do it. If you incite the aliens to obliterate the planet, you wouldn’t want that on your tombstone, right?”

I couldn’t argue with that. But initially, I could scarcely believe I was having this conversation at a serious research institute rather than at a science fiction convention. The sci-fi feel of our talk was underlined by the toy figures of bug-eyed aliens that cheerfully decorate the office.

But Dr Shostak is a credible and popular figure and has been invited to present his arguments.

Leading astronomers, anthropologists and social scientists will gather at his institute after the AAAS meeting for a symposium to flesh out plans for a proposal for active Seti to put to the public and politicians.

High on the agenda is whether such a move would, as he put it so starkly, lead to the “obliteration” of the planet.

“I don’t see why the aliens would have any incentive to do that,” Dr Shostak tells me.

“Beyond that, we have been telling them willy-nilly that we are here for 70 years now. They are not very interesting messages but the early TV broadcasts, the early radio, the radar from the Second World War – all that has leaked off the Earth.

“Any society that could come here and ruin our whole day by incinerating the planet already knows we are here.”

# The Big Crunch

It may just be possible that prophetic doomsayers have been right all along. The end is coming… well, in a few tens of billions of years. A group of physicists propose that the cosmos will soon begin collapsing in on itself. Keep in mind that soon in cosmological terms runs into the billions of years. So, it does appear that we still have some time to crunch down our breakfast cereal a few more times before the ultimate universal apocalypse. Clearly this may not please those who seek the end of days within their lifetimes, and for rather different — scientific — reasons, cosmologists seem to be unhappy too.

From Phys:

Physicists have proposed a mechanism for “cosmological collapse” that predicts that the universe will soon stop expanding and collapse in on itself, obliterating all matter as we know it. Their calculations suggest that the collapse is “imminent”—on the order of a few tens of billions of years or so—which may not keep most people up at night, but for the physicists it’s still much too soon.

In a paper published in Physical Review Letters, physicists Nemanja Kaloper at the University of California, Davis; and Antonio Padilla at the University of Nottingham have proposed the cosmological collapse mechanism and analyzed its implications, which include an explanation of dark energy.

“The fact that we are seeing dark energy now could be taken as an indication of impending doom, and we are trying to look at the data to put some figures on the end date,” Padilla told Phys.org. “Early indications suggest the collapse will kick in in a few tens of billions of years, but we have yet to properly verify this.”

The main point of the paper is not so much when exactly the universe will end, but that the mechanism may help resolve some of the unanswered questions in physics. In particular, why is the universe expanding at an accelerating rate, and what is the dark energy causing this acceleration? These questions are related to the cosmological constant problem, which is that the predicted vacuum energy density of the universe causing the expansion is much larger than what is observed.

“I think we have opened up a brand new approach to what some have described as ‘the mother of all physics problems,’ namely the cosmological constant problem,” Padilla said. “It’s way too early to say if it will stand the test of time, but so far it has stood up to scrutiny, and it does seem to address the issue of vacuum energy contributions from the standard model, and how they gravitate.”

The collapse mechanism builds on the physicists’ previous research on vacuum energy sequestering, which they proposed to address the cosmological constant problem. The dynamics of vacuum energy sequestering predict that the universe will collapse, but don’t provide a specific mechanism for how collapse will occur.

According to the new mechanism, the universe originated under a set of specific initial conditions so that it naturally evolved to its present state of acceleration and will continue on a path toward collapse. In this scenario, once the collapse trigger begins to dominate, it does so in a period of “slow roll” that brings about the accelerated expansion we see today. Eventually the universe will stop expanding and reach a turnaround point at which it begins to shrink, culminating in a “big crunch.”

Image: Image of the Cosmic Microwave Background (CMB) from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. Courtesy of NASA.

# Universal Amniotic Fluid

Another day, another physics paper describing the origin of the universe. This is no wonder. Since the development of general relativity and quantum mechanics — two mutually incompatible descriptions of our reality — theoreticians have been scurrying to come up with a grand theory, a rapprochement of sorts. This one describes the universe as a quantum fluid, perhaps made up of hypothesized gravitons.

From Nature Asia:

The prevailing model of cosmology, based on Einstein’s theory of general relativity, puts the universe at around 13.8 billion years old and suggests it originated from a “singularity” – an infinitely small and dense point – at the Big Bang.

To understand what happened inside that tiny singularity, physicists must marry general relativity with quantum mechanics – the laws that govern small objects. Applying both of these disciplines has challenged physicists for decades. “The Big Bang singularity is the most serious problem of general relativity, because the laws of physics appear to break down there,” says Ahmed Farag Ali, a physicist at Zewail City of Science and Technology, Egypt.

In an effort to bring together the laws of quantum mechanics and general relativity, and to solve the singularity puzzle, Ali and Saurya Das, a physicist at the University of Lethbridge in Alberta Canada, employed an equation that predicts the development of singularities in general relativity. That equation had been developed by Das’s former professor, Amal Kumar Raychaudhuri, when Das was an undergraduate student at Presidency University, in Kolkata, India, so Das was particularly familiar and fascinated by it.

When Ali and Das made small quantum corrections to the Raychaudhuri equation, they realised it described a fluid, made up of small particles, that pervades space. Physicists have long believed that a quantum version of gravity would include a hypothetical particle, called the graviton, which generates the force of gravity. In their new model — which will appear in Physics Letters B in February — Ali and Das propose that such gravitons could form this fluid.

To understand the origin of the universe, they used this corrected equation to trace the behaviour of the fluid back through time. Surprisingly, they found that it did not converge into a singularity. Instead, the universe appears to have existed forever. Although it was smaller in the past, it never quite crunched down to nothing, says Das.

“Our theory serves to complement Einstein’s general relativity, which is very successful at describing physics over large distances,” says Ali. “But physicists know that to describe short distances, quantum mechanics must be accommodated, and the quantum Raychaudhui equation is a big step towards that.”

The model could also help solve two other cosmic mysteries. In the late 1990s, astronomers discovered that the expansion of the universe is accelerating due the presence of a mysterious dark energy, the origin of which is not known. The model has the potential to explain it since the fluid creates a minor but constant outward force that expands space. “This is a happy offshoot of our work,” says Das.

Astronomers also now know that most matter in the universe is in an invisible mysterious form called dark matter, only perceptible through its gravitational effect on visible matter such as stars. When Das and a colleague set the mass of the graviton in the model to a small level, they could make the density of their fluid match the universe’s observed density of dark matter, while also providing the right value for dark energy’s push.

# MondayMap: Our New Address — Laniakea

Once upon a time we humans sat smugly at the center of the universe. Now, many of us (though, not yet all) know better. Over the the last several centuries we learned and accepted that the Earth spun around the nearest Star, and not the converse. We then learned that the Sun formed part of an immense galaxy, the Milky Way, itself spinning in a vast cosmological dance. More recently, we learned that the Milky Way formed part of a larger cluster of galaxies, known as the Local Group.

Now we find that our Local Group is a mere speck within an immense supercluster containing around 100,000 galaxies spanning half a billion light years. Researchers have dubbed this galactic supercluster, rather aptly, Laniakea, Hawaiian for “immense heaven”. Laniakea is your new address. And, fascinatingly, Laniakea is moving towards an even larger grouping of galaxies named the Shapely supercluster.

From the Guardian:

In what amounts to a back-to-school gift for pupils with nerdier leanings, researchers have added a fresh line to the cosmic address of humanity. No longer will a standard home address followed by “the Earth, the solar system, the Milky Way, the universe” suffice for aficionados of the extended astronomical location system.

The extra line places the Milky Way in a vast network of neighbouring galaxies or “supercluster” that forms a spectacular web of stars and planets stretching across 520m light years of our local patch of universe. Named Laniakea, meaning “immeasurable heaven” in Hawaiian, the supercluster contains 100,000 large galaxies that together have the mass of 100 million billion suns.

Our home galaxy, the Milky Way, lies on the far outskirts of Laniakea near the border with another supercluster of galaxies named Perseus-Pisces. “When you look at it in three dimensions, is looks like a sphere that’s been badly beaten up and we are over near the edge, being pulled towards the centre,” said Brent Tully, an astronomer at the University of Hawaii in Honolulu.

Astronomers have long known that just as the solar system is part of the Milky Way, so the Milky Way belongs to a cosmic structure that is much larger still. But their attempts to define the larger structure had been thwarted because it was impossible to work out where one cluster of galaxies ended and another began.

Tully’s team gathered measurements on the positions and movement of more than 8,000 galaxies and, after discounting the expansion of the universe, worked out which were being pulled towards us and which were being pulled away. This allowed the scientists to define superclusters of galaxies that all moved in the same direction (if you’re reading this story on a mobile device, click here to watch a video explaining the research).

The work published in Nature gives astronomers their first look at the vast group of galaxies to which the Milky Way belongs. A narrow arch of galaxies connects Laniakea to the neighbouring Perseus-Pisces supercluster, while two other superclusters called Shapley and Coma lie on the far side of our own.

Tully said the research will help scientists understand why the Milky Way is hurtling through space at 600km a second towards the constellation of Centaurus. Part of the reason is the gravitational pull of other galaxies in our supercluster.

“But our whole supercluster is being pulled in the direction of this other supercluster, Shapley, though it remains to be seen if that’s all that’s going on,” said Tully.

Read the entire article here or the nerdier paper here.

Image: Laniakea: Our Home Supercluster of Galaxies. The blue dot represents the location of the Milky Way. Courtesy: R. Brent Tully (U. Hawaii) et al., SDvision, DP, CEA/Saclay.

# The Next (and Final) Doomsday Scenario

Personally, I love dystopian visions and apocalyptic nightmares. So, news that the famed Higgs boson may ultimately cause our demise, and incidentally the end of the entire cosmos, caught my attention.

Apparently theoreticians have calculated that the Higgs potential of which the Higgs boson is a manifestation has characteristics that make the universe unstable. (The Higgs was discovered in 2012 by teams at CERN’s Large Hadron Collider.) Luckily for those wishing to avoid the final catastrophe this instability may keep the universe intact for several more billions of years, and if suddenly the Higgs were to trigger the final apocalypse it would be at the speed of light.

From Popular Mechanics:

In July 2012, when scientists at CERN’s Large Hadron Collider culminated decades of work with their discovery of the Higgs boson, most physicists celebrated. Stephen Hawking did not. The famed theorist expressed his disappointmentthat nothing more unusual was found, calling the discovery “a pity in a way.” But did he ever say the Higgs could destroy the universe?

That’s what many reports in the media said earlier this week, quoting a preface Hawking wrote to a book called Starmus. According to The Australian, the preface reads in part: “The Higgs potential has the worrisome feature that it might become metastable at energies above 100 [billion] gigaelectronvolts (GeV). This could mean that the universe could undergo catastrophic vacuum decay, with a bubble of the true vacuum expanding at the speed of light. This could happen at any time and we wouldn’t see it coming.”

What Hawking is talking about here is not the Higgs boson but what’s called the Higgs potential, which are “totally different concepts,” says Katie Mack, a theoretical astrophysicist at Melbourne University. The Higgs field permeates the entire universe, and the Higgs boson is an excitation of that field, just like an electron is an excitation of an electric field. In this analogy, the Higgs potential is like the voltage, determining the value of the field.

Once physicists began to close in on the mass of the Higgs boson, they were able to work out the Higgs potential. That value seemed to reveal that the universe exists in what’s known as a meta-stable vacuum state, or false vacuum, a state that’s stable for now but could slip into the “true” vacuum at any time. This is the catastrophic vacuum decay in Hawking’s warning, though he is not the first to posit the idea.

Is he right?

“There are a couple of really good reasons to think that’s not the end of the story,” Mack says. There are two ways for a meta-stable state to fall off into the true vacuum—one classical way, and one quantum way. The first would occur via a huge energy boost, the 100 billion GeVs Hawking mentions. But, Mack says, the universe already experienced such high energies during the period of inflation just after the big bang. Particles in cosmic rays from space also regularly collide with these kinds of high energies, and yet the vacuum hasn’t collapsed (otherwise, we wouldn’t be here).

“Imagine that somebody hands you a piece of paper and says, ‘This piece of paper has the potential to spontaneously combust,’ and so you might be worried,” Mack says. “But then they tell you 20 years ago it was in a furnace.” If it didn’t combust in the furnace, it’s not likely to combust sitting in your hand.

Of course, there’s always the quantum world to consider, and that’s where things always get weirder. In the quantum world, where the smallest of particles interact, it’s possible for a particle on one side of a barrier to suddenly appear on the other side of the barrier without actually going through it, a phenomenon known as quantum tunneling. If our universe was in fact in a meta-stable state, it could quantum tunnel through the barrier to the vacuum on the other side with no warning, destroying everything in an instant. And while that is theoretically possible, predictions show that if it were to happen, it’s not likely for billions of billions of years. By then, the sun and Earth and you and I and Stephen Hawking will be a distant memory, so it’s probably not worth losing sleep over it.

What’s more likely, Mack says, is that there is some new physics not yet understood that makes our vacuum stable. Physicists know there are parts of the model missing; mysteries like quantum gravity and dark matter that still defy explanation. When two physicists published a paper documenting the Higgs potential conundrum in March, their conclusion was that an explanation lies beyond the Standard Model, not that the universe may collapse at any time.

# The Cosmological Axis of Evil

The cosmos seems remarkably uniform — look in any direction with the naked eye or the most powerful telescopes and you’ll see much the same as in any other direction. Yet, on a grand scale, our universe shows some peculiar fluctuations that have cosmologists scratching their heads. The temperature of the universe, as described by the cosmic microwave background (CMB), shows some interesting fluctuations in specific, vast regions. It is the distribution of these temperature variations that shows what seem to be non-random patterns. Cosmologists have dubbed the pattern, “axis of evil”.

From ars technica:

The Universe is incredibly regular. The variation of the cosmos’ temperature across the entire sky is tiny: a few millionths of a degree, no matter which direction you look. Yet the same light from the very early cosmos that reveals the Universe’s evenness also tells astronomers a great deal about the conditions that gave rise to irregularities like stars, galaxies, and (incidentally) us.

That light is the cosmic microwave background, and it provides some of the best knowledge we have about the structure, content, and history of the Universe. But it also contains a few mysteries: on very large scales, the cosmos seems to have a certain lopsidedness. That slight asymmetry is reflected in temperature fluctuations much larger than any galaxy, aligned on the sky in a pattern facetiously dubbed “the axis of evil.”

The lopsidedness is real, but cosmologists are divided over whether it reveals anything meaningful about the fundamental laws of physics. The fluctuations are sufficiently small that they could arise from random chance. We have just one observable Universe, but nobody sensible believes we can see all of it. With a sufficiently large cosmos beyond the reach of our telescopes, the rest of the Universe may balance the oddity that we can see, making it a minor, local variation.

However, if the asymmetry can’t be explained away so simply, it could indicate that some new physical mechanisms were at work in the early history of the Universe. As Amanda Yoho, a graduate student in cosmology at Case Western Reserve University, told Ars, “I think the alignments, in conjunction with all of the other large angle anomalies, must point to something we don’t know, whether that be new fundamental physics, unknown astrophysical or cosmological sources, or something else.”

Over the centuries, astronomers have provided increasing evidence that Earth, the Solar System, and the Milky Way don’t occupy a special position in the cosmos. Not only are we not at the center of existence—much less the corrupt sinkhole surrounded by the pure crystal heavens, as in early geocentric Christian theology—the Universe has no center and no edge.

In cosmology, that’s elevated to a principle. The Universe is isotropic, meaning it’s (roughly) the same in every direction. The cosmic microwave background (CMB) is the strongest evidence for the isotropic principle: the spectrum of the light reaching Earth from every direction indicates that it was emitted by matter at almost exactly the same temperature.

The Big Bang model explains why. In the early years of the Universe’s history, matter was very dense and hot, forming an opaque plasma of electrons, protons, and helium nuclei. The expansion of space-time thinned out until the plasma cooled enough that stable atoms could form. That event, which ended roughly 380,000 years after the Big Bang, is known as recombination. The immediate side effect was to make the Universe transparent and liberate vast numbers of photons, most of which have traveled through space unmolested ever since.

We observe the relics of recombination in the form of the CMB. The temperature of the Universe today is about 2.73 degrees above absolute zero in every part of the sky. The lack of variation makes the cosmos nearly as close to a perfect thermal body as possible. However, measurements show anisotropies—tiny fluctuations in temperature, roughly 10 millionths of a degree or less. These irregularities later gave rise to areas where mass gathered. A perfectly featureless, isotropic cosmos would have no stars, galaxies, or planets full of humans.

To measure the physical size of these anisotropies, researchers turn the whole-sky map of temperature fluctuations into something called a power spectrum. That’s akin to the process of taking light from a galaxy and finding the component wavelengths (colors) that make it up. The power spectrum encompasses fluctuations over the whole sky down to very small variations in temperature. (For those with some higher mathematics knowledge, this process involves decomposing the temperature fluctuations in spherical harmonics.)

Smaller details in the fluctuations tell cosmologists the relative amounts of ordinary matter, dark matter, and dark energy. However, some of the largest fluctuations—covering one-fourth, one-eighth, and one-sixteenth of the sky—are bigger than any structure in the Universe, therefore representing temperature variations across the whole sky.

Those large-scale fluctuations in the power spectrum are where something weird happens. The temperature variations are both larger than expected and aligned with each other to a high degree. That’s at odds with theoretical expectations: the CMB anisotropies should be randomly oriented, not aligned. In fact, the smaller-scale variations are random, which makes the deviation at larger scales that much stranger.

Kate Land and Joao Magueijo jokingly dubbed the strange alignment “the axis of evil” in a 2005 paper (freely available on the ArXiv), riffing on an infamous statement by then-US President George W. Bush. Their findings were based on data from an earlier observatory, the Wilkinson Microwave Anisotropy Probe (WMAP), but the follow-up Planck mission found similar results. There’s no question that the “axis of evil” is there; cosmologists just have to figure out what to think about it.

The task of interpretation is complicated by what’s called “cosmic variance,” or the fact that our observable Universe is just one region in a larger Universe. Random chance dictates that some pockets of the whole Universe will have larger or smaller fluctuations than others, and those fluctuations might even be aligned entirely by coincidence.

In other words, the “axis of evil” could very well be an illusion, a pattern that wouldn’t seem amiss if we could see more of the Universe. However, cosmic variance also predicts how big those local, random deviations should be—and the fluctuations in the CMB data are larger. They’re not so large as to rule out the possibility of a local variation entirely—they’re above-average height—but cosmologists can’t easily dismiss the possibility that something else is going on.

Image courtesy of Hinshaw et al WMAP paper.

# You May Be Living Inside a Simulation

Some theorists posit that we are living inside a simulation, that the entire universe is one giant, evolving model inside a grander reality. This is a fascinating idea, but may never be experimentally verifiable. So just relax — you and I may not be real, but we’ll never know.

On the other hand, but in a similar vein, researchers have themselves developed the broadest and most detailed simulation of the universe to date. Now, there are no “living” things yet inside this computer model, but it’s probably only a matter of time before our increasingly sophisticated simulations start wondering if they are simulations as well.

From the BBC:

An international team of researchers has created the most complete visual simulation of how the Universe evolved.

The computer model shows how the first galaxies formed around clumps of a mysterious, invisible substance called dark matter.

It is the first time that the Universe has been modelled so extensively and to such great resolution.

The research has been published in the journal Nature.

Now we can get to grips with how stars and galaxies form and relate it to dark matter”

The simulation will provide a test bed for emerging theories of what the Universe is made of and what makes it tick.

One of the world’s leading authorities on galaxy formation, Professor Richard Ellis of the California Institute of Technology (Caltech) in Pasadena, described the simulation as “fabulous”.

“Now we can get to grips with how stars and galaxies form and relate it to dark matter,” he told BBC News.

The computer model draws on the theories of Professor Carlos Frenk of Durham University, UK, who said he was “pleased” that a computer model should come up with such a good result assuming that it began with dark matter.

“You can make stars and galaxies that look like the real thing. But it is the dark matter that is calling the shots”.

Cosmologists have been creating computer models of how the Universe evolved for more than 20 years. It involves entering details of what the Universe was like shortly after the Big Bang, developing a computer program which encapsulates the main theories of cosmology and then letting the programme run.

The simulated Universe that comes out at the other end is usually a very rough approximation of what astronomers really see.

The latest simulation, however, comes up with the Universe that is strikingly like the real one.

Immense computing power has been used to recreate this virtual Universe. It would take a normal laptop nearly 2,000 years to run the simulation. However, using state-of-the-art supercomputers and clever software called Arepo, researchers were able to crunch the numbers in three months.

#### Cosmic tree

In the beginning, it shows strands of mysterious material which cosmologists call “dark matter” sprawling across the emptiness of space like branches of a cosmic tree. As millions of years pass by, the dark matter clumps and concentrates to form seeds for the first galaxies.

Then emerges the non-dark matter, the stuff that will in time go on to make stars, planets and life emerge.

But early on there are a series of cataclysmic explosions when it gets sucked into black holes and then spat out: a chaotic period which was regulating the formation of stars and galaxies. Eventually, the simulation settles into a Universe that is similar to the one we see around us.

According to Dr Mark Vogelsberger of Massachusetts Institute of Technology (MIT), who led the research, the simulations back many of the current theories of cosmology.

“Many of the simulated galaxies agree very well with the galaxies in the real Universe. It tells us that the basic understanding of how the Universe works must be correct and complete,” he said.

In particular, it backs the theory that dark matter is the scaffold on which the visible Universe is hanging.

“If you don’t include dark matter (in the simulation) it will not look like the real Universe,” Dr Vogelsberger told BBC News.

Image: On the left: the real universe imaged via the Hubble telescope. On the right: a view of what emerges from the computer simulation. Courtesy of BBC / Illustris Collaboration.

# You May Be Just a Line of Code

Some very logical and rational people — scientists and philosophers — argue that we are no more than artificial constructs. They suggest that it is more likely that we are fleeting constructions in a simulated universe rather than organic beings in a real cosmos; that we are, in essence, like the oblivious Neo in the classic sci-fi movie The Matrix. One supposes that the minds proposing this notion are themselves simulations…

From Discovery:

In the 1999 sci-fi film classic The Matrix, the protagonist, Neo, is stunned to see people defying the laws of physics, running up walls and vanishing suddenly. These superhuman violations of the rules of the universe are possible because, unbeknownst to him, Neo’s consciousness is embedded in the Matrix, a virtual-reality simulation created by sentient machines.

The action really begins when Neo is given a fateful choice: Take the blue pill and return to his oblivious, virtual existence, or take the red pill to learn the truth about the Matrix and find out “how deep the rabbit hole goes.”

Physicists can now offer us the same choice, the ability to test whether we live in our own virtual Matrix, by studying radiation from space. As fanciful as it sounds, some philosophers have long argued that we’re actually more likely to be artificial intelligences trapped in a fake universe than we are organic minds in the “real” one.

But if that were true, the very laws of physics that allow us to devise such reality-checking technology may have little to do with the fundamental rules that govern the meta-universe inhabited by our simulators. To us, these programmers would be gods, able to twist reality on a whim.

So should we say yes to the offer to take the red pill and learn the truth — or are the implications too disturbing?

#### Worlds in Our Grasp

The first serious attempt to find the truth about our universe came in 2001, when an effort to calculate the resources needed for a universe-size simulation made the prospect seem impossible.

Seth Lloyd, a quantum-mechanical engineer at MIT, estimated the number of “computer operations” our universe has performed since the Big Bang — basically, every event that has ever happened. To repeat them, and generate a perfect facsimile of reality down to the last atom, would take more energy than the universe has.

“The computer would have to be bigger than the universe, and time would tick more slowly in the program than in reality,” says Lloyd. “So why even bother building it?”

But others soon realized that making an imperfect copy of the universe that’s just good enough to fool its inhabitants would take far less computational power. In such a makeshift cosmos, the fine details of the microscopic world and the farthest stars might only be filled in by the programmers on the rare occasions that people study them with scientific equipment. As soon as no one was looking, they’d simply vanish.

In theory, we’d never detect these disappearing features, however, because each time the simulators noticed we were observing them again, they’d sketch them back in.

That realization makes creating virtual universes eerily possible, even for us. Today’s supercomputers already crudely model the early universe, simulating how infant galaxies grew and changed. Given the rapid technological advances we’ve witnessed over past decades — your cell phone has more processing power than NASA’s computers had during the moon landings — it’s not a huge leap to imagine that such simulations will eventually encompass intelligent life.

“We may be able to fit humans into our simulation boxes within a century,” says Silas Beane, a nuclear physicist at the University of Washington in Seattle. Beane develops simulations that re-create how elementary protons and neutrons joined together to form ever larger atoms in our young universe.

Legislation and social mores could soon be all that keeps us from creating a universe of artificial, but still feeling, humans — but our tech-savvy descendants may find the power to play God too tempting to resist.

They could create a plethora of pet universes, vastly outnumbering the real cosmos. This thought led philosopher Nick Bostrom at the University of Oxford to conclude in 2003 that it makes more sense to bet that we’re delusional silicon-based artificial intelligences in one of these many forgeries, rather than carbon-based organisms in the genuine universe. Since there seemed no way to tell the difference between the two possibilities, however, bookmakers did not have to lose sleep working out the precise odds.

#### Learning the Truth

That changed in 2007 when John D. Barrow, professor of mathematical sciences at Cambridge University, suggested that an imperfect simulation of reality would contain detectable glitches. Just like your computer, the universe’s operating system would need updates to keep working.

As the simulation degrades, Barrow suggested, we might see aspects of nature that are supposed to be static — such as the speed of light or the fine-structure constant that describes the strength of the electromagnetic force — inexplicably drift from their “constant” values.

Last year, Beane and colleagues suggested a more concrete test of the simulation hypothesis. Most physicists assume that space is smooth and extends out infinitely. But physicists modeling the early universe cannot easily re-create a perfectly smooth background to house their atoms, stars and galaxies. Instead, they build up their simulated space from a lattice, or grid, just as television images are made up from multiple pixels.

The team calculated that the motion of particles within their simulation, and thus their energy, is related to the distance between the points of the lattice: the smaller the grid size, the higher the energy particles can have. That means that if our universe is a simulation, we’ll observe a maximum energy amount for the fastest particles. And as it happens, astronomers have noticed that cosmic rays, high-speed particles that originate in far-flung galaxies, always arrive at Earth with a specific maximum energy of about 1020 electron volts.

The simulation’s lattice has another observable effect that astronomers could pick up. If space is continuous, then there is no underlying grid that guides the direction of cosmic rays — they should come in from every direction equally. If we live in a simulation based on a lattice, however, the team has calculated that we wouldn’t see this even distribution. If physicists do see an uneven distribution, it would be a tough result to explain if the cosmos were real.

Astronomers need much more cosmic ray data to answer this one way or another. For Beane, either outcome would be fine. “Learning we live in a simulation would make no more difference to my life than believing that the universe was seeded at the Big Bang,” he says. But that’s because Beane imagines the simulators as driven purely to understand the cosmos, with no desire to interfere with their simulations.

Unfortunately, our almighty simulators may instead have programmed us into a universe-size reality show — and are capable of manipulating the rules of the game, purely for their entertainment. In that case, maybe our best strategy is to lead lives that amuse our audience, in the hope that our simulator-gods will resurrect us in the afterlife of next-generation simulations.

The weird consequences would not end there. Our simulators may be simulations themselves — just one rabbit hole within a linked series, each with different fundamental physical laws. “If we’re indeed a simulation, then that would be a logical possibility, that what we’re measuring aren’t really the laws of nature, they’re some sort of attempt at some sort of artificial law that the simulators have come up with. That’s a depressing thought!” says Beane.

This cosmic ray test may help reveal whether we are just lines of code in an artificial Matrix, where the established rules of physics may be bent, or even broken. But if learning that truth means accepting that you may never know for sure what’s real — including yourself — would you want to know?

There is no turning back, Neo: Do you take the blue pill, or the red pill?

Image: The Matrix, promotional poster for the movie. Courtesy of Silver Pictures / Warner Bros. Entertainment Inc.

# MondayMap: The Biggest 3D Map Ever

The Sloan Digital Sky Survey (SDSS) is an ambitious multi-year effort to map the cosmos. Since its inception in 2000 the project has imaged and mapped around 930,000 galaxies and 120,000 quasars. Now thanks to some rather cool computational visualization we can zoom through an animation of the map in 3D.

[tube]aRosM1TLyLw[/tube]

# Impossible Chemistry in Space

Combine the vastness of the universe with the probabilistic behavior of quantum mechanics and you get some rather odd chemical results. This includes the spontaneous creation of some complex organic molecules in interstellar space — previously believed to be far too inhospitable for all but the lowliest forms of matter.

From the New Scientist:

Quantum weirdness can generate a molecule in space that shouldn’t exist by the classic rules of chemistry. If interstellar space is really a kind of quantum chemistry lab, that might also account for a host of other organic molecules glimpsed in space.

Interstellar space should be too cold for most chemical reactions to occur, as the low temperature makes it tough for molecules drifting through space to acquire the energy needed to break their bonds. “There is a standard law that says as you lower the temperature, the rates of reactions should slow down,” says Dwayne Heard of the University of Leeds, UK.

Yet we know there are a host of complex organic molecules in space. Some reactions could occur when different molecules stick to the surface of cosmic dust grain. This might give them enough time together to acquire the energy needed to react, which doesn’t happen when molecules drift past each other in space.

Not all reactions can be explained in this way, though. Last year astronomers discovered methoxy molecules – containing carbon, hydrogen and oxygen – in the Perseus molecular cloud, around 600 light years from Earth. But researchers couldn’t produce this molecule in the lab by allowing reactants to condense on dust grains, leaving a puzzle as to how it could have formed.

### Molecular hang-out

Another route to methoxy is to combine a hydroxyl radical and methanol gas, both present in space. But this reaction requires hurdling a significant energy barrier – and the energy to do that simply isn’t available in the cold expanse of space.

Heard and his colleagues wondered if the answer lay in quantum mechanics: a process called quantum tunnelling might give the hydroxyl radical a small chance to cheat by digging through the barrier instead of going over it, they reasoned.

So, in another attempt to replicate the production of methoxy in space, the team chilled gaseous hydroxyl and methanol to 63 kelvin – and were able to produce methoxy.

The idea is that at low temperatures, the molecules slow down, increasing the likelihood of tunnelling. “At normal temperatures they just collide off each other, but when you go down in temperature they hang out together long enough,” says Heard.

### Impossible chemistry

The team also found that the reaction occurred 50 times faster via quantum tunnelling than if it occurred normally at room temperature by hurdling the energy barrier. Empty space is much colder than 63 kelvin, but dust clouds near stars can reach this temperature, adds Heard.

“We’re showing there is organic chemistry in space of the type of reactions where it was assumed these just wouldn’t happen,” says Heard.

That means the chemistry of space may be richer than we had imagined. “There is maybe a suite of chemical reactions we hadn’t yet considered occurring in interstellar space,” agrees Helen Fraser of the University of Strathclyde, UK, who was not part of the team.

Image: Amino-1-methoxy-4-methylbenzol, featuring methoxy molecular structure, recently found in interstellar space. Courtesy of Wikipedia.

# Everywhere And Nowhere

Most physicists believe that dark matter exists, but have never seen it, only deduced its existence. This is a rather unsettling state of affairs since by most estimates dark matter (and possibly dark energy) accounts for 95 percent of the universe. The stuff we are made from, interact with and see on a daily basis — atoms, their constituents and their forces — is a mere 5 percent.

From the Atlantic:

Here’s a little experiment.

Now put it back down.

In that window of time, your hand somehow interacted with dark matter — the mysterious stuff that comprises the vast majority of the universe. “Our best guess,” according to Dan Hooper, an astronomy professor at the University of Chicago and a theoretical astrophysicist at the Fermi National Accelerator Laboratory, “is that a million particles of dark matter passed through your hand just now.”

Dark matter, in other words, is not merely the stuff of black holes and deep space. It is all around us. Somehow. We’re pretty sure.

But if you did the experiment — as the audience at Hooper’s talk on dark matter and other cosmic mysteries did at the Aspen Ideas Festival today — you didn’t feel those million particles. We humans have no sense of their existence, Hooper said, in part because they don’t hew to the forces that regulate our movement in the world — gravity, electromagnetism, the forces we can, in some way, feel. Dark matter, instead, is “this ghostly, elusive stuff that dominates our universe,” Hooper said.

It’s everywhere. And it’s also, as far as human knowledge is concerned, nowhere.

And yet, despite its mysteries, we know it’s out there. “All astronomers are in complete conviction that there is dark matter,” said Richard Massey, the lead author of a recent study mapping the dark matter of the universe, and Hooper’s co-panelist. The evidence for its existence, Hooper agreed, is “overwhelming.” And yet it’s evidence based on deduction: through our examinations of the observable universe, we make assumptions about the unobservable version.

Dark matter, in other words, is aptly named. A full 95 percent of the universe — the dark matter, the stuff that both is and is not — is effectively unknown to us. “All the science that we’ve ever done only ever examines five percent of the universe,” Massey said. Which means that there are still mysteries to be unraveled, and dark truths to be brought to light.

And it also means, Massey pointed out, that for scientists, “the job security is great.”

You might be wondering, though: given how little we know about dark matter, how is it that Hooper knew that a million particles of the stuff passed through your hand as you raised and lowered it?

“I cheated a little,” Hooper admitted. He assumed a particular mass for the individual particles. “We know what the density of dark matter is on Earth from watching how the Milky Way rotates. And we know roughly how fast they’re going. So you take those two bits of information, and all you need to know is how much mass each individual particle has, and then I can get the million number. And I assumed a kind of traditional guess. But it could be 10,000 higher; it could be 10,000 lower.”

# Looking for Alien Engineering Work

We haven’t yet found any aliens inhabiting exoplanets orbiting distant stars. We haven’t received any intelligently manufactured radio signals from deep space. And, unless you subscribe to the conspiracy theories surrounding Roswell Area 51, it’s unlikely that we’ve been visited by an extra-terrestrial intelligence.

Most reasonable calculations suggest that the universe should be teeming with life beyond our small, blue planet. So, where are all the aliens and why haven’t we been contacted yet? Not content to wait, some astronomers believe we should be looking for evidence of distant alien engineering projects.

From the New Scientist:

ALIENS: where are you? Our hopes of finding intelligent companionship seem to be constantly receding. Mars and Venus are not the richly populated realms we once guessed at. The icy seas of the outer solar system may hold life, but almost certainly no more than microbes. And the search for radio signals from more distant extraterrestrials has so frustrated some astronomers that they are suggesting we shout out an interstellar “Hello”, in the hope of prodding the dozy creatures into a response.

So maybe we need to think along different lines. Rather than trying to intercept alien communications, perhaps we should go looking for alien artefacts.

There have already been a handful of small-scale searches, but now three teams of astronomers are setting out to scan a much greater volume of space (see diagram). Two groups hope to see the shadows of alien industry in fluctuating starlight. The third, like archaeologists sifting through a midden heap on Earth, is hunting for alien waste.

What they’re after is something rather grander than flint arrowheads or shards of pottery. Something big. Planet-sized power stations. Star-girdling rings or spheres. Computers the size of a solar system. Perhaps even an assembly of hardware so vast it can darken an entire galaxy.

It might seem crazy to even entertain the notion of such stupendous celestial edifices, let alone go and look for them. Yet there is a simple rationale. Unless tool-users are always doomed to destroy themselves, any civilisation out there is likely to be far older and far more advanced than ours.

Humanity has already covered vast areas of Earth’s surface with roads and cities, and begun sending probes to other planets. If we can do all this in a matter of centuries, what could more advanced civilisations do over many thousands or even millions of years?

In 1960, the physicist Freeman Dyson pointed out that if alien civilisations keep growing and expanding, they will inevitably consume ever more energy – and the biggest source of energy in any star system is the star itself. Our total power consumption today is equivalent to about 0.01 per cent of the sunlight falling on Earth, so solar power could easily supply all our needs. If energy demand keeps growing at 1 per cent a year, however, then in 1000 years we’d need more energy than strikes the surface of the planet. Other energy sources, such as nuclear fusion, cannot solve the problem because the waste heat would fry the planet.

In a similar position, alien civilisations could start building solar power plants, factories and even habitats in space. With material mined from asteroids, then planets, and perhaps even the star itself, they could really spread out. Dyson’s conclusion was that after thousands or millions of years, the star might be entirely surrounded by a vast artificial sphere of solar panels.

The scale of a Dyson sphere is almost unimaginable. A sphere with a radius similar to that of Earth’s orbit would have more than a hundred million times the surface area of Earth. Nobody thinks building it would be easy. A single shell is almost certainly out, as it would be under extraordinary stresses and gravitationally unstable. A more plausible option is a swarm: many huge power stations on orbits that do not intersect, effectively surrounding the star. Dyson himself does not like to speculate on the details, or on the likelihood of a sphere being built. “We have no way of judging,” he says. The crucial point is that if any aliens have built Dyson spheres, there is a chance we could spot them.

A sphere would block the sun’s light, making it invisible to our eyes, but the sphere would still emit waste heat in the form of infrared radiation. So, as Carl Sagan pointed out in 1966, if infrared telescopes spot a warm object but nothing shows up at visible wavelengths, it could be a Dyson sphere.

Some natural objects can produce the same effect. Very young and very old stars are often surrounded by dust and gas, which blocks their light and radiates infrared. But the infrared spectrum of these objects should be a giveaway. Silicate minerals in dust produce a distinctive broad peak in the spectrum, and molecules in a warm gas would produce bright or dark spectral lines at specific wavelengths. By contrast, waste heat from a sphere should have a smooth, featureless thermal spectrum. “We would be hoping that the spectrum looks boring,” says Matt Povich at the California State Polytechnic University in Pomona. “The more boring the better.”

Our first good view of the sky at the appropriate wavelengths came when the Infrared Astronomical Satellite surveyed the skies for 10 months in 1983, and a few astronomers have sifted through its data. Vyacheslav Slysh at the Space Research Institute in Moscow made the first attempt in 1985, and Richard Carrigan at Fermilab in Illinois published the latest search in 2009. “I wanted to get into the mode of the British Museum, to go and look for artefacts,” he says.

Carrigan found no persuasive sources, but the range of his search was limited. It would have detected spheres around sunlike stars only within 1000 light years of Earth. This is a very small part of the Milky Way, which is 100,000 light years across.

One reason few have joined Carrigan in the hunt for artefacts is the difficulty of getting funding for such projects. Then last year, the Templeton Foundation – an organisation set up by a billionaire to fund research into the “big questions” – invited proposals for its New Frontiers programme, specifically requesting research that would not normally be funded because of its speculative nature. A few astronomers jumped at the chance to look for alien contraptions and, in October, the programme approved three separate searches. The grants are just a couple of hundred thousand dollars each, but they do not have to fund new telescopes, only new analysis.

One team, led by Jason Wright at Pennsylvania State University in University Park, will look for the waste heat of Dyson spheres by analysing data from two space-based infrared observatories, the Wide-field Infrared Survey Explorer (WISE) and the Spitzer space telescope, launched in 2009 and 2003. Povich, a member of this team, is looking specifically within the Milky Way. Thanks to the data from Spitzer and WISE, Povich should be able to scan a volume of space thousands of times larger than previous searches like Carrigan’s. “For example, if you had a sun-equivalent star, fully enclosed in a Dyson sphere, we should be able to detect it almost anywhere in the galaxy.”

Even such a wide-ranging hunt may not be ambitious enough, according to Wright. He suspects that interstellar travel will prove no harder than constructing a sphere. An alien civilisation with such a high level of technology would spread out and colonise the galaxy in a few million years, building spheres as they go. “I would argue that it’s very hard for a spacefaring civilisation to die out. There are too many lifeboats,” says Wright. “Once you have self-sufficient colonies, you will take over the galaxy – you can’t even try to stop it because you can’t coordinate the actions of the colonies.”

If this had happened in the Milky Way, there should be spheres everywhere. “To find one or a few Dyson spheres in our galaxy would be very strange,” says Wright.

Read the entire article after the jump.

Image: 2001: A Space Odyssey, The Monolith. Courtesy of Daily Galaxy.

# Something Out of Nothing

The debate on how the universe came to be rages on. Perhaps, however, we are a little closer to understanding why there is “something”, including us, rather than “nothing”.

[div class=attrib]From Scientific American:[end-div]

Why is there something rather than nothing? This is one of those profound questions that is easy to ask but difficult to answer. For millennia humans simply said, “God did it”: a creator existed before the universe and brought it into existence out of nothing. But this just begs the question of what created God—and if God does not need a creator, logic dictates that neither does the universe. Science deals with natural (not supernatural) causes and, as such, has several ways of exploring where the “something” came from.

Multiple universes. There are many multiverse hypotheses predicted from mathematics and physics that show how our universe may have been born from another universe. For example, our universe may be just one of many bubble universes with varying laws of nature. Those universes with laws similar to ours will produce stars, some of which collapse into black holes and singularities that give birth to new universes—in a manner similar to the singularity that physicists believe gave rise to the big bang.

M-theory. In his and Leonard Mlodinow’s 2010 book, The Grand Design, Stephen Hawking embraces “M-theory” (an extension of string theory that includes 11 dimensions) as “the only candidate for a complete theory of the universe. If it is finite—and this has yet to be proved—it will be a model of a universe that creates itself.”

Quantum foam creation. The “nothing” of the vacuum of space actually consists of subatomic spacetime turbulence at extremely small distances measurable at the Planck scale—the length at which the structure of spacetime is dominated by quantum gravity. At this scale, the Heisenberg uncertainty principle allows energy to briefly decay into particles and antiparticles, thereby producing “something” from “nothing.”

Nothing is unstable. In his new book, A Universe from Nothing, cosmologist Lawrence M. Krauss attempts to link quantum physics to Einstein’s general theory of relativity to explain the origin of a universe from nothing: “In quantum gravity, universes can, and indeed always will, spontaneously appear from nothing. Such universes need not be empty, but can have matter and radiation in them, as long as the total energy, including the negative energy associated with gravity [balancing the positive energy of matter], is zero.” Furthermore, “for the closed universes that might be created through such mechanisms to last for longer than infinitesimal times, something like inflation is necessary.” Observations show that the universe is in fact flat (there is just enough matter to slow its expansion but not to halt it), has zero total energy and underwent rapid inflation, or expansion, soon after the big bang, as described by inflationary cosmology. Krauss concludes: “Quantum gravity not only appears to allow universes to be created from noth ing—meaning … absence of space and time—it may require them. ‘Nothing’—in this case no space, no time, no anything!—is unstable.”

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: There’s Nothing Out There. Courtesy of Rolfe Kanefsky / Image Entertainment.[end-div]

# The Infant Universe

Long before the first galaxy clusters and the first galaxies appeared in our universe, and before the first stars, came the first basic elements — hydrogen, helium and lithium.

Results from a just published study identify these raw materials from what is theorized to be the universe’s first few minutes of existence.

[div class=attrib]From Scientific American:[end-div]

By peering into the distance with the biggest and best telescopes in the world, astronomers have managed to glimpse exploding stars, galaxies and other glowing cosmic beacons as they appeared just hundreds of millions of years after the big bang. They are so far away that their light is only now reaching Earth, even though it was emitted more than 13 billion years ago.

Astronomers have been able to identify those objects in the early universe because their bright glow has remained visible even after a long, universe-spanning journey. But spotting the raw materials from which the first cosmic structures formed—the gas produced as the infant universe expanded and cooled in the first few minutes after the big bang—has not been possible. That material is not itself luminous, and everywhere astronomers have looked they have found not the primordial light-element gases hydrogen, helium and lithium from the big bang but rather material polluted by heavier elements, which form only in stellar interiors and in cataclysms such as supernovae.

Now a group of researchers reports identifying the first known pockets of pristine gas, two relics of those first minutes of the universe’s existence. The team found a pair of gas clouds that contain no detectable heavy elements whatsoever by looking at distant quasars and the intervening material they illuminate. Quasars are bright objects powered by a ravenous black hole, and the spectral quality of their light reveals what it passed through on its way to Earth, in much the same way that the lamp of a projector casts the colors of film onto a screen. The findings appeared online November 10 in Science.

“We found two gas clouds that show a significant abundance of hydrogen, so we know that they are there,” says lead study author Michele Fumagalli, a graduate student at the University of California, Santa Cruz. One of the clouds also shows traces of deuterium, also known as heavy hydrogen, the nucleus of which contains not only a proton, as ordinary hydrogen does, but also a neutron. Deuterium should have been produced in big bang nucleosynthesis but is easily destroyed, so its presence is indicative of a pristine environment. The amount of deuterium present agrees with theoretical predictions about the mixture of elements that should have emerged from the big bang. “But we don’t see any trace of heavier elements like carbon, oxygen and iron,” Fumagalli says. “That’s what tells us that this is primordial gas.”

The newfound gas clouds, as Fumagalli and his colleagues see them, existed about two billion years after the big bang, at an epoch of cosmic evolution known as redshift 3. (Redshift is a sort of cosmological distance measure, corresponding to the degree that light waves have been stretched on their trip across an expanding universe.) By that time the first generation of stars, initially comprising only the primordial light elements, had formed and were distributing the heavier elements they forged via nuclear fusion reactions into interstellar space.

But the new study shows that some nooks of the universe remained pristine long after stars had begun to spew heavy elements. “They have looked for these special corners of the universe, where things just haven’t been polluted yet,” says Massachusetts Institute of Technology astronomer Rob Simcoe, who did not contribute to the new study. “Everyplace else that we’ve looked in these environments, we do find these heavy elements.”

[div class=attrib]Read the entire article here.[end-div]

[div class=attrib]Image: Simulation by Ceverino, Dekel and Primack. Courtesy of Scientific American.[end-div]

# The Universe and Determinism

General scientific consensus suggests that our universe has no pre-defined destiny. While a number of current theories propose anything from a final Big Crush to an accelerating expansion into cold nothingness the future plan for the universe is not pre-determined. Unfortunately, our increasingly sophisticated scientific tools are still to meager to test and answer these questions definitively. So, theorists currently seem to have the upper hand. And, now yet another theory puts current cosmological thinking on its head by proposing that the future is pre-destined and that it may even reach back into the past to shape the present. Confused? Read on!

[div class=attrib]From FQXi:[end-div]

The universe has a destiny—and this set fate could be reaching backwards in time and combining with influences from the past to shape the present. It’s a mind-bending claim, but some cosmologists now believe that a radical reformulation of quantum mechanics in which the future can affect the past could solve some of the universe’s biggest mysteries, including how life arose. What’s more, the researchers claim that recent lab experiments are dramatically confirming the concepts underpinning this reformulation.

Cosmologist Paul Davies, at Arizona State University in Tempe, is embarking on a project to investigate the future’s reach into the present, with the help of a \$70,000 grant from the Foundational Questions Institute. It is a project that has been brewing for more than 30 years, since Davies first heard of attempts by physicist Yakir Aharonov to get to root of some of the paradoxes of quantum mechanics. One of these is the theory’s apparent indeterminism: You cannot predict the outcome of experiments on a quantum particle precisely; perform exactly the same experiment on two identical particles and you will get two different results.

While most physicists faced with this have concluded that reality is fundamentally, deeply random, Aharonov argues that there is order hidden within the uncertainty. But to understand its source requires a leap of imagination that takes us beyond our traditional view of time and causality. In his radical reinterpretation of quantum mechanics, Aharonov argues that two seemingly identical particles behave differently under the same conditions because they are fundamentally different. We just do not appreciate this difference in the present because it can only be revealed by experiments carried out in the future.

“It’s a very, very profound idea,” says Davies. Aharonov’s take on quantum mechanics can explain all the usual results that the conventional interpretations can, but with the added bonus that it also explains away nature’s apparent indeterminism. What’s more, a theory in which the future can influence the past may have huge—and much needed—repercussions for our understanding of the universe, says Davies.

[div class=attrib]More from theSource here.[end-div]

# So the Universe is Flat?

Having just posted an article that described the universe in terms of holographic principles – a 3-D projection on a two dimensional surface, it’s timely to put the theory in context, of other theories of course. There’s a theory that posits that the universe is a bubble wrought from the collision of high-dimensional branes (membrane that is). There’s a theory that suggests that our universe is one of many in a soup of multi-verses. Other theories suggest that the universe is made up of 9, 10 or 11 dimensions.

There’s another theory that the universe is flat, and that’s where Davide Castelvecchi (mathematician, science editor at Scientific American and blogger) over at Degrees of Freedom describes the current thinking.

[div class=attrib]What Do You Mean, The Universe Is Flat? (Part I), from Degrees of Freedom:[end-div]

In the last decade—you may have read this news countless times—cosmologists have found what they say is rather convincing evidence that the universe (meaning 3-D space) is flat, or at least very close to being flat.

The exact meaning of flat, versus curved, space deserves a post of its own, and that is what Part II of this series will be about. For the time being, it is convenient to just visualize a plane as our archetype of flat object, and the surface of the Earth as our archetype of a curved one. Both are two-dimensional, but as I will describe in the next installment, flatness and curviness make sense in any number of dimensions.

What I do want to talk about here is what it is that is supposed to be flat.

When cosmologists say that the universe is flat they are referring to space—the nowverse and its parallel siblings of time past. Spacetime is not flat. It can’t be: Einstein’s general theory of relativity says that matter and energy curve spacetime, and there are enough matter and energy lying around to provide for curvature. Besides, if spacetime were flat I wouldn’t be sitting here because there would be no gravity to keep me on the chair. To put it succintly: space can be flat even if spacetime isn’t.

Moreover, when they talk about the flatness of space cosmologists are referring to the large-scale appearance of the universe. When you “zoom in” and look at something of less-than-cosmic scale, such as the solar system, space—not just spacetime—is definitely not flat. Remarkable fresh evidence for this fact was obtained recently by the longest-running experiment in NASA history, Gravity Probe B, which took a direct measurement of the curvature of space around Earth. (And the most extreme case of non-flatness of space is thought to occur inside the event horizon of a black hole, but that’s another story.)

On a cosmic scale, the curvature created in space by the countless stars, black holes, dust clouds, galaxies, and so on constitutes just a bunch of little bumps on a space that is, overall, boringly flat.