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Beyond the Darkness Dark Matter

from Through the Wormhole; You, me, the sun, stars, everything we see has one thing in common. We're all made of atoms. Atoms make up almost all the matter in the known Universe, but there is a whole lot more to the cosmos, a side we're only just beginning to see. Our bodies, our homes, our world, even the vast void of space is teeming with a mysterious substance a form of matter so strange that many scientists once doubted its very existence. But in 2009, an incredibly sensitive particle detector caught the first glimpse of it. It's an Earth-shaking discovery, and it's forcing us to radically reassess our place in the Universe and even our eventual fate. As a boy, I used to lie in my room at night, gripped by fear that something was out there in the darkness. In the 1960s, a young astronomer called Vera Rubin decided to explore an area of space that was little-studied. Vera Rubin knew if she studied something sexy, like black holes, other astronomers would end up beating her to publication. It took us about two years to get velocities of 90 stars in the Andromeda galaxy. And the results were rather startling. We found that all of the stars were moving at the same velocity, the same number, 250 kilometers per second. For the next few years, every galaxy Vera looked at gave her the same seemingly crazy results. All the stars all the way to the edge of the galaxies were moving at the same speed, completely different from the way the solar system works. The only explanation was that the force of gravity did not get weaker the further a star was from the center of a galaxy. But that could only happen if the galaxies had more mass than astronomers could see. The explanation was that there must be very significant amounts of matter that are invisible. In fact, perhaps 90% or 95% of the material in the galaxy is invisible. This was a truly revolutionary idea. Galaxies might be filled with an unseeable substance, something scientists could only think to call "Dark Matter." But such a radical theory demanded ironclad evidence. Soon dozens of astronomers were checking Vera's observations. Across the Atlantic in England, leading cosmologist Carlos Frenk began to investigate the idea of Dark Matter, using not telescopes but equations. Take Newton's laws of gravity and feed them into a highly sophisticated computer simulation. This is the cosmology machine, a very large supercomputer whose only purpose is to simulate the Universe. It's made up of 1,300 computers all working together. Even then, it takes months to complete a simulation of a small part of our Universe. This is awesome computing power almost beyond imagination, but that's what it takes if you want to emulate the Universe. In Edinburgh, Scotland, Richard Massey is still trying to answer that question and is pioneering a new way of detecting Dark Matter, gravitational lensing. It's all thanks to the genius of this man. Albert Einstein saw space in a new way, as a bendable, malleable material that is influenced by gravity. Anything that has mass, a star or a galaxy, can bend the fabric of space and act like a lens. As it bends space, so the light traveling past it is also bent. Dark Matter doesn't reflect light, it doesn't absorb light, it doesn't emit light. Light just passes straight through it unaffected. So we have to look for something else, the way it affects, gravitationally, things around it that we can see. Now, this idea of light being deflected and bent by warped space-time sounds crazy, but actually it's very familiar. We see light being bent all the time, every time you look through the bottom of a wineglass. Let me show you what I mean. Although the bottom of the wineglass is transparent and light passes straight through it, you know it's there because of these distorted images in the background. Dark Matter is exactly the same. It bends light, through a different physical effect, but the net result is the same, that these images of very distinct galaxies appear distorted whenever there's some Dark Matter in front of them. What we can see is but the tip of an iceberg in the Universe, most of it is Dark Matter. Everywhere astronomers look, they are starting to sense the heavy presence of Dark Matter. And what Richard has done for one corner of the sky, Carlos Frenk has now done with a simulation of the whole Universe. We can see here the intricate patterns that the Dark Matter forms, this network of filaments and lumps that we refer to as the cosmic Web. The Dark Matter doesn't interact in any way, so it just passed straight through the collision. And when the two lumps of dark matter smashed into each other, they didn't even notice. They just passed straight through. Cosmic disasters halfway across the Universe have proved that Dark Matter is out there and unlike anything we know, invisible, intangible, almost like a ghost. We can't see it... We can't touch it... But it's everywhere. Billions of dark-matter particles pass through our bodies every second. Now, if science can somehow trap one of these particles and study it, then we might finally understand what most of the Universe is made of and what this really means for us. In the past century, physicists have worked out that all matter is built from about 20 basic subatomic particles. They go by names like bosons, electrons, quarks, and neutrinos. But they also suspect other more exotic particles exist. There are plenty of theories out there for what Dark Matter might be. We're gradually working through the list and trying to rule them out one by one. That's the scientific method. The favorite theory for what Dark Matter is is a supersymmetric particle, that is to say that all the ordinary particles that we know about have this sort of a mirror image, that there's this extra set of particles that is in the dark sector that don't interact in any way with the ordinary material except through the force of gravity, which is very weak. Scientists have another name for these dark-matter particles, weakly interacting massive particles, "wimps" for short. Dan Bauer has found the perfect place to hunt for wimps, down an abandoned Minnesota iron mine half a mile underground. We're now heading down underground into the Soudan Underground Laboratory. Two events, two possible wimp impacts in one year of 24-hour-a-day detecting. For the first time, we may have actually trapped pieces of this elusive Dark Matter. This could be a giant leap toward understanding what Dark Matter really is. But Dan's not 100% sure that what he has are even wimps at all. So the search must go on. It's exciting, but you have to temper that excitement as a scientist and realize that you haven't proven it yet. But just as scientists begin to feel they're getting a handle on Dark Matter, they discover something very strange. Dark Matter may be the stuff that's allowed our galaxy to form, but it's not the end of the story. At the dawn of the 21st century, a space probe found something else hiding in the darkness. While Dark Matter strives to hold us all together, this force might be preparing to destroy the entire Universe. We now know that the visible Universe is nothing more than a layer of foam floating on a vast sea of Dark Matter. Astronomers find themselves adrift on this unfamiliar ocean. Saul Perlmutter has been navigating these waters for the past two decades, trying to determine what Dark Matter might mean for our eventual fate. As a young student in physics, I very much wanted to measure something that seemed fundamental, which is, what's the fate of the Universe? Will the Universe last forever, or someday will it come to a halt and collapse? Saul chose to walk in the footsteps of the 20th century's most illustrious astronomer, Edwin Hubble. Back in the 1920s, Hubble began a meticulous survey of dozens of galaxies in the night sky. But he noticed something strange. Almost all of the galaxies were tinged red. Just as sound coming from objects moving away from us gets lower light gets redder. Hubble deduced that every galaxy in the Universe is actually hurtling away from us. There was only one conclusion, the Universe must be expanding. But he couldn't tell how fast. Why? Because galaxies that are close and relatively dim look very similar to those that are far away but very bright, so he couldn't judge their distance. Of course, the tricky thing is that you need to know how bright the actual galaxies are if you're going to tell how far away they are. If you're a sailor out at sea and you're looking at a distant lighthouse through the fog, you don't know whether it's a very bright lighthouse and you're very far away or whether it's a very faint lighthouse and you're very nearby. This is the fundamental problem, then, that astronomers have had to struggle with through the last centuries. But there is a solution to this problem. Astrophysicists have known since the 1980s about a particular type of star explosion called a type 1A Supernova. When a star slightly bigger than our sun runs out of fuel to burn, it shrinks down into a dimmer, denser state known as a white dwarf. David Spergel is a WMAP scientist. Atoms make up about 5%, 4.6% to be precise. Dark Matter makes up about 23%. And what's very strange is, 72% is made up of this Dark Energy. Put another way, Dark Matter dwarfs us, but Dark Energy, a mysterious, repulsive force that scientists do not understand at all, dwarfs Dark Matter. It makes up very nearly 3/4 of the Universe. Dark Energy rules the Universe, and it appears to be growing stronger day by day. How long will it be before this mysterious force rips apart every atom in the cosmos? Peering into the darkness is revolutionizing the way we see the cosmos and ourselves. Only 5% of the Universe is made of atoms, the stuff we're made of. Almost 1/4 of the Universe is Dark Matter, a substance that allowed galaxies to form. And 3/4 is Dark Energy, an inexplicable force that's trying to push everything apart. How will this struggle end? Could it eventually tear our Universe to pieces? Brenna Flaugher plans on solving this puzzle by measuring just how powerful Dark Energy is. And this is the device she's going to use. It's the digital eye of a new telescope called the Dark Energy camera. So, we want to understand Dark Energy as best we can. We need to gather as much information as possible. This sensor has an incredible 520 megapixels. Each one, chilled by liquid helium, is capable of picking up particles of light that have traveled across the Universe for billions of years. We're going deeper than other cameras have in the past, so we're measuring stuff further and further back in time and also doing it quickly with this big camera. The Dark Energy camera will be able to cover huge swaths of the sky in a single night and will keep on doing so for five years, slowly building up more detail in its images, searching for clues about how Dark Energy has evolved as our Universe has evolved. Right now the information that we have about Dark Energy is that it's getting stronger and stronger and the Universe is expanding faster and faster. And we don't know why. And since we don't know why, we don't know what comes next. We want to take these deeper surveys to try to understand that. The hope is that these surveys will reveal our Universe's future by looking back at its 14 billion years of development in unprecedented detail. As best as scientists understand it now, Dark Matter was the dominant force in determining the form of the Universe in its first 7 billion years. It was Dark Matter, after all, that allowed galaxies to form, attracting regular matter with its invisible mass. In its second 7 billion years, Dark Energy grew, overtook Dark Matter, and now seems to be winning the cosmic contest, driving galaxies further and further away from one another. The way that we're going to understand better what is this Dark Energy that's accelerating through the Universe today is to go back in time and look at, when did Dark Energy first start to become important? When did we switch from a Universe that was slowing down to a Universe that's speeding up, and how did that happen? What was the actual history of the switch from slowing to speeding?


  Beyond the Darkness Dark Matter find answers from scientists Vera Rubin, Carlos Frenk, Richard Massey, Dan Bauer, Saul Perlmutter, David Spergel, Brenna Flaugher
Milky Way and his computing simulation
Milky Way and his computing simulation



Billions of dark-matter particles pass through our bodies every second
Billions of dark-matter particles pass through our bodies every second



Soudan Underground Laboratory
Soudan Underground Laboratory



Digital eye of a new telescope
Digital eye of a new telescope
  If you can get a very detailed history of the expansion of the Universe, that will differentiate between these different theories of Dark Energy. And that's one of the jobs that we're tackling right now. Where will this mighty battle end... A truce or a crushing victory for one side? It all depends on what Dark Energy actually is, and there are several competing theories. One of the more ominous calls it "Phantom Energy." Out of all these many theories of Dark Energy, one of them is that it's this Phantom Energy, it's called. And that has this interesting consequence that as it's accelerating the expansion of the Universe, making it bigger and bigger, its acceleration gets faster and faster and faster. If Dark Energy is this phantom energy, it's accelerating the expansion of the Universe so much that the Universe gets bigger and bigger, more rarified and diluted, and eventually galaxies will start to get torn apart. Even after that, solar systems will get pulled apart, and then stars, and eventually even the constituent atoms and particles that the Universe is made of will get ripped apart in what is known as the big rip. But there is one bright spot in this dark and threatening picture. One thing that we know little about, Dark Matter, may end up being the best tool to study Dark Energy. Dark Energy is a force that's trying to push the Universe apart. Dark Matter is trying to clump things together.     And it's the interplay of these two things that has led to the formation of the structures that we see in the Universe today. And so by understanding how fast the galaxy clusters form and clump together, that tells us about Dark Matter but also about how much Dark Energy was pushing it apart at the same time. Scientists using something they barely understand to try to get a handle on something they don't understand at all. These are truly strange days in cosmology. We have come a long way in a quest to understand the Universe. I remember 30 years ago, when the mere concept of Dark Matter was deemed to be revolutionary. It was speculative. It was even somewhat heretical. I would have never dreamt then that 30 years later, truly alien concepts like Dark Matter and Dark Energy are actually taken for granted. Turns out I was right. There really is something in the shadows. But I never knew just how important it was. From the corner of my own bedroom to the farthest reaches of space, darkness dominates the Universe... And controls our fate. So far, the struggle between Dark Matter and Dark Energy has been good to us. After all, without it, there would be no galaxies, no planets, no you, no me. But our days may be numbered. One day Darkness could extinguish the light forever. Until we fully understand these colossal forces, what ultimately lies in store, heaven only knows.
List with pictures of the scientists, in order of their appearance in Through the Wormhole Beyond the Darkness Dark Matter documentary, who share us their knowledges:
Vera Rubin
Vera Rubin (astronomer)
  Carlos Frenk
Carlos Frenk (cosmologist)
  Richard Massey
Richard Massey (Royal Observatory Edinburgh)
  Dan Bauer
Dan Bauer (Cryogenic Dark Matter Search project manager)
  Saul Perlmutter
Saul Perlmutter (Lawrence Berkeley Laboratory)
  David Spergel
David Spergel (WMAP scientist)
  Brenna Flaugher
Brenna Flaugher (scientist, Dark Energy camera)