Dark matter is stuff in space that has gravity, but it is unlike anything scientists have ever seen before. Together, dark matter and dark energy make up 95% of the universe. That only leaves a small 5% for all the matter and energy we know and understand.This might be a surprise, but we don’t know what most of the universe is made of.

Critics Consensus: Dark Matter's premiere benefits from likable characters and a concluding twist, but its gaping plot holes and worn premise add up to an aimless episode. 2015, SyFy, 13 episodes.

Seriously, we don’t. You might be thinking, “But of course we do! It’s made of galaxies, stars, planets, black holes, comets, asteroids, and all the other cool space stuff!”Yes, there is a lot of amazing space stuff, but if we add it all up, it’s just a very small part of the entire universe. There’s a lot more out there. And we don’t fully understand what it is.When scientists study our universe, they see that it’s expanding.

But if the universe is only made of the galaxies, stars, planets, and other things that we know about, it shouldn’t be expanding. Something else is out there. There has to be energy that is making the universe expand. We just don’t know what this energy is. We also don’t know where it comes from.

But we can tell that it’s there. Scientists named this energy dark energy.We don’t know much about dark energy, but we do know there is a lot of it.

Dark energy makes up 68%, about two-thirds, of the universe.There is also stuff out there in space that has gravity. We can see its pull on matter like stars and galaxies. But it’s not regular matter. It’s not a black hole. It’s not anything that we have ever heard of. But it’s definitely there.

Scientists named this stuff dark matter.Just like dark energy, we don’t know a whole lot about dark matter. But it seems that 27% of the universe, or about one quarter, is made up of the strange stuff.Together, dark energy and dark matter make up 95% of the universe. That’s almost all of it!

That only leaves a small 5% for all the matter and energy we know and understand. Energy like light, heat, and X-rays, together with matter like people, elephants, planet Earth, the sun, and all the galaxies only makes up 5% of the universe!

That’s not very much.Dark matter and dark energy raise some of the biggest questions in the study of space and physics. Lots of scientists are using observations and math to figure out what these are. This will help us understand more about our amazing universe, where there is always more to discover and more to learn.

• Posted 06.25.08
• NOVA scienceNOW

(This program is no longer available for online streaming.) Host Neil deGrasse Tyson reports from a half mile underground in an abandoned mine, where scientists are using special detectors to look for evidence of a ghostly substance that they believe makes up most of the matter of the universe—a hypothetical entity called dark matter.

Transcript

DARK MATTER

PBS Airdate: June 25, 2008

NEILdeGRASSE TYSON: Hi. I'm NeildeGrasse Tyson. Welcome to a new season of NOVA scienceNOW.

Now,I'm an ordinary guy, and that means, of course, I'm made up ofordinary matter: basically, atoms. And when we gaze out into space, everythingwe see—galaxies, stars—is also ordinary, made of atoms.

Buta lot of scientists say there's something else in the universethat's NOT ordinary.

Wait,who said that?

NEIL'SJACKET SLEEVE: And by the way, there seemsto be way more of this weird stuff than ordinary guys like you..

NEILdeGRASSE TYSON: Hey, watch it!

Andeven though it's invisible, it's getting harder and harder toignore.

Everyday, a crew squeezes into an 80-year-old elevator in Minnesota and commutes towork a half a mile down, into the depths of an abandoned mine.

They'renot searching for gold or diamonds. Instead, they're mining for somethingeven more coveted and harder to find, something called dark matter.

RICHARDMASSEY: Dark matter is one of the biggestmysteries.

TALIFIGUEROA: Dark matter iseverywhere.

RICHARDMASSEY: We wouldn't be here if itweren't for the dark matter. Life wouldn't be possible.

TALIFIGUEROA: The problem iswe have no clue what the dark matter is.

JOCELYNMONROE (Massachusetts Institute ofTechnology): We know it'sout there, and we just have to find it.

NEILdeGRASSE TYSON: One of the peoplenow trying to find dark matter is physicist Tali Figueroa.

TALIFIGUEROA: Discoveringdark matter is going to be one of the greatest finds of the century.

NEILdeGRASSE TYSON: So, they reallymine iron in this place.

Hissearch takes place a half-mile under ground, where this old iron mine has beentransformed into a cavernous, space-age physics lab. Parkitecture style houses.

WhenI visited, I didn't notice any dark matter, but I did see quite a bit ofdead matter.

Whoa,what is this thing?

TALIFIGUEROA: That's abat.

NEILdeGRASSE TYSON: It doesn'tlook very alive.

TALIFIGUEROA: Probably isn't.

NEILdeGRASSE TYSON: Whoa, there'sone there..another, another.

TALIFIGUEROA: They'reall over the place.

NEILdeGRASSE TYSON: That's nasty.

TALIFIGUEROA: It is, kindof.

NEILdeGRASSE TYSON: Nasty. So thatdoesn't creep you out?

TALIFIGUEROA: You get usedto it.

NEILdeGRASSE TYSON: Down here,surrounded by the dead bats, Tali and his colleagues monitor and care for acomplex contraption specially designed to detect particles of dark matter.

Sothis is it, huh?

TALIFIGUEROA: Yup.

NEILdeGRASSE TYSON: This elaborateendeavor is all to solve a mystery that's been plaguing astrophysicistsfor more than 70 years.

Itmight seem bizarre and even a bit crazy, but there's a chance that mostof the matter in the universe is not stars or planets or gas or anything familiarto us, but is in the form of some mysterious invisible substance. We'velabeled it 'dark matter,' but why do we think it exists at all?

Itcomes down to gravity and speed. Ever since Isaac Newton, we've knownthat it's gravity that holds objects in orbit, just as the sun holdsEarth and the rest of the planets.

Thestronger the gravity pulling it inward, the faster an object can go and stay inorbit. It's kind of like spinning a heavy ball around: the harder youpull on the ball, the faster the ball will travel. If the ball gets moving toofast, even a strong guy like this has got to let go.

PETERFISHER (Massachusetts Institute ofTechnology): The faster you wantsomething to go—like, you know, David throwing his slingshot—themore you have to pull on it. And the thing that's pulling on something tomake it orbit is gravity.

NEILdeGRASSE TYSON: And where doesgravity come from? Well, we know it can be things with mass like stars, houses,planets, trains, clouds, jellyfish; they all have gravity.

So,in the universe, the more stuff, the more gravity, and the faster objects canmove and remain in their orbits. The problem is when we look out beyond oursolar system, like at stars orbiting within galaxies, or galaxies moving withingalaxy clusters. They're all orbiting faster than we'd expect.

JOCELYNMONROE: The speed at which the stars aregoing around at is too fast. You would expect that it should just escape, butthose stars don't escape. They're still going around.

NEILdeGRASSE TYSON: There's gotto be a lot of gravity holding them all together, but apparently there'snot enough matter to account for it.

PETERFISHER: Andthere's not enough stuff. There's just not enough stuff to keepthem all going around each other.

NEILdeGRASSE TYSON: Regardless of howwe probe the cosmos for this missing matter—using visible light, radiowaves, x-rays—we still come up short. Either we've got the laws ofgravity completely wrong, or there's got to be more stuff. Actually, we'dneed about five times more stuff. It's stuff we can't see, but whatexactly is it?

RICHARDMASSEY: What is dark matter?

MAXTEGMARK (Massachusetts Institute ofTechnology): What is the darkmatter?

RICHARDMASSEY: Yeah, that is a big question.

TALIFIGUEROA: We don'tknow what it is.

RICHARDMASSEY: It's completely invisible.

TALIFIGUEROA: It'sdark. It doesn't glow.

MAXTEGMARK: So,whatever the dark matter is..

TALIFIGUEROA: We can'tpoint a telescope up and actually see it.

MAXTEGMARK: ..itsure ain't made of atoms.

NEILdeGRASSE TYSON: Everything aroundus that we can see and touch, ordinary matter, is made of atoms. But one thingwe know is dark matter is not ordinary.

RICHARDMASSEY: We know its not ordinary matter,because ordinary matter has all this whole other variety of interactions. Ithas electric fields and magnetic fields. It emits light.

NEILdeGRASSE TYSON: One idea is, sinceit's not made of ordinary atoms, dark matter might be made of some exoticparticle. Right now, physicists around the world are racing to build a detectorsensitive enough to capture one, so they can figure out exactly what it is.

Buthow do you catch a particle that's so shy?

TALIFIGUEROA: Thefundamental problem is that this dark matter does not interact with matter verymuch. And so, in order to detect it, we have to build these really specialized,very sensitive detectors.

NEILdeGRASSE TYSON: At this undergroundlab, Tali Figueroa is monitoring one kind of dark matter detector, asuperconducting crystal made from the element germanium.

So,one of your detectors, huh?

TALIFIGUEROA: Yes, this is aprototype of one of the 30 detectors. And when you look at the surface of ourdetector, you'll see a metal grid.

NEILdeGRASSE TYSON: The grid picks uptiny temperature changes, produced when a particle hits the crystal and setsall its atoms vibrating. But to detect those vibrations, the atoms in thecrystal have to start out as still as possible, something atoms don'tnormally like to do.

TALIFIGUEROA: The problem isthat naturally, at room temperature, the atoms are vibrating themselves.

NEILdeGRASSE TYSON: So, how does theteam manage to slow down the detector's atoms? They put it in a freezer,a very powerful freezer.

Sothe whole point of this is to simply keep the experiment cold?

TALIFIGUEROA: Yes. We haveto keep the experiment at about 50 milliKelvin, which is 50/1000 of a degreeabove absolute zero.

NEILdeGRASSE TYSON: Just a fraction ofa degree above absolute zero? Translated into Fahrenheit, that's, like,460 degrees below zero. So, in other words, it's cold enough so that theair we breathe freezes solid.

TALIFIGUEROA: Absolutely.

NEILdeGRASSE TYSON: And sothere's frost everywhere.

Butnow there's another problem. The frozen detector is so hyper-sensitive,lots of things could set it off, like cosmic rays, particles that shower Earthfrom space. So this is why the whole lab is deep under ground.

Sothe bedrock..

TALIFIGUEROA: The half amile of rock..

NEILdeGRASSE TYSON: ..above..

TALIFIGUEROA: ..is ashield.

NEILdeGRASSE TYSON: ..is a shield. Sothe cosmic rays..these are high energy particles from space?

TALIFIGUEROA: From space.

NEILdeGRASSE TYSON: Okay. Soyou're protecting yourself from space.

Andit's not just cosmic rays. Even under ground, there are other tinyparticles flitting around us, including photons and neutrons that can fly outof the surrounding rock. So the detectors are cloaked in layer upon layer ofshielding, all in an effort to filter out everything but the dark matter. Andhow are things going so far?

Okay,how many dark matter particles have you found so far?

TALIFIGUEROA: None.

NEILdeGRASSE TYSON: None?

TALIFIGUEROA: None.

NEILdeGRASSE TYSON: It's not toosurprising. The quest for dark matter here on Earth has only just begun, andbigger and more sensitive detectors are already in the works. Still, you mightwonder, could it be that dark matter is something that's just out therein space and not down here with us?

AstrophysicistRichard Massey says, 'not likely.' He's got the first-ever,3-D dark matter maps to back him up. But how do you map the unseeable?

RICHARDMASSEY: So we can't see dark matterdirectly; it's completely invisible. But we can work out where it is byits effects on the ordinary matter that we can see.

NEILdeGRASSE TYSON: In other words, youcan see dark matter's gravity. That's because, according toEinstein and nearly a century of experiments, what gravity does in the universeis bend space. Massive objects like the sun actually bend and stretch thecontours of space. That's what keeps smaller objects, like Earth, inorbit.

Andif space is bent, so is any light that passes through it.

RICHARDMASSEY: So let's debunk the wholeidea that light travels in straight lines. Light travels in what it thinks arestraight lines. And because space is warped and bent, even the straight linesthat light rays travel along are actually bent themselves.

NEILdeGRASSE TYSON: The phenomenon iscalled gravitational lensing. Think of what a thick magnifying glass can do thetext of a book.

RICHARDMASSEY: When we put a magnifying glass infront of it, we start seeing a distorted image, and gravitational lensing tofind dark matter works in a very similar way.

NEILdeGRASSE TYSON: A huge clump ofdark matter and the enormous gravity it creates would bend areas of space somuch, it would act like a giant cosmic lens, distorting our view of distantgalaxies.

Themore distortion, the more gravity, and, Massey assumes, the more dark matterlies between them and us.

RICHARDMASSEY: So, the final result is that weend up having this map of where the dark matter is in the universe.

NEILdeGRASSE TYSON: Maps such as theseare now revealing that galaxies like ours are completely enveloped by giantclouds of dark matter.

RICHARDMASSEY: Wherever there's ordinarymatter, so even here, there is some dark matter. It's everywhere. The tworeally have gone together, hand in hand.

NEILdeGRASSE TYSON: In fact, as the universeevolved after the Big Bang, dark matter may have served as a kind ofcosmological glue that, over time, helped pull stars together to form galaxies.

The Wall Street Journal. Mars marshall. Retrieved December 18, 2016.

RICHARDMASSEY: We owe everything to dark matter,in two ways: firstly, it holds the whole universe together; but then it also,crucially..inside that, it forms this scaffolding in which the ordinary mattercan lay to grow.

MAXTEGMARK: We are solucky to have dark matter, because we wouldn't even be here otherwise. Itwas the gravitational attraction from dark matter that pulled together thisdiffused gas that eventually formed our Milky Way galaxy that we live in. Andif there were no dark matter, then our galaxy would, in fact, never haveformed.

NEILdeGRASSE TYSON: If that'strue, then it's not just our Milky Way. Across the universe, none of thebillions of galaxies out there would have formed without the gravity of thismysterious stuff.

Now,we just need to find out what it is.

MAXTEGMARK: It'sreally astonishing that there's five times more stuff out there than weknow of, and that we've been at this, as a community, for over 70 years. Andyet it might be now, in the next few years, that we'll figure it all out.It's just incredible.

Credits

Dark Matter

Edited by

Doug Quade

Written,Produced and Directed by

Julia Cort

NOVA scienceNOW

Executive Producer

Samuel Fine

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NeildeGrasse Tyson

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Sound Recordists

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Three dimensional brain animation

Courtesy Dr. Arthur W. Toga,Laboratory of Neuro Imaging at UCLA

Archival Material

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Special Thanks

BriarwoodHealthcare and Rehabilitation Center, Needham, MA
Douglas Clowe
Bamidele Faboyede
Prasad Jayanti
Kimo Johnson
Eric Kee
Sue Moen
Soudan Underground Mine - A Minnesota State Park
Twin Cities Public Television
Jeff Woodward

Neil deGrasse Tyson

is director of the Hayden Planetarium in theRose Center for Earth and Space at the American Museum of Natural History.

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This material is based upon work supported by the NationalScience Foundation under Grant No. 0638931. Any opinions, findings, andconclusions or recommendations expressed in this material are those of theauthor(s) and do not necessarily reflect the views of the National ScienceFoundation.

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