Gravitational Waves 101: How to Hear the Universe

Gravitational Waves 101: How to Hear the Universe

years ago in a galaxy far, far away, two black holes,
each roughly 30 times the mass of our Sun and drawn by their
immense pull of gravity, spiraled inward
towards each other at over half the speed of light. When they collided, the
energy of their impact was so great that it created
a shockwave that could be heard all across the universe. And this is what
it sounded like. [BLIP] OK, so that might not be the
massive explosion you were expecting and as
you’re probably aware, sound doesn’t travel
through outer space. We’ve been lied to our whole
life by movies and television. [PEWING] [EXPLOSION] [GLASS SHATTERING] But that little bitty
thump that you did here was a direct sound translation
of the gravitational waves emitted by the collision
of two black holes. And that little
thump could signify the beginning of a whole new way
of understanding our universe. Or it could just be the
beginning of an EDM song. [BEATBOXING] RYAN WOLFF: Everywhere we
go, we’re surrounded by waves and these waves send us
information about our world. CRAIG BENZINE: Light
waves emitted by the Sun or artificially bounce off of
objects in our environment, telling us about
what they’re made of, their shape, their size. RYAN WOLFF: Sound waves can tell
us about an object’s location and if it’s moving, how fast. And then, there’s just
waves, which are mostly here for visual reference
but they can tell us things, like about the weather
or if the tide’s coming in or if I should go wax
my surfboard right now. But the waves we’re
most interested in today are by far the most
difficult ones to detect. And they could be one
of the most important scientific discoveries
of the past century. On September 14, 2015,
a team of scientists working at the
Laser Interferometer Gravitational-Wave
Observatory, or LIGO, detected a ripple in the
fabric of space-time. This was the first direct
proof of gravity waves but the idea that something
like this could exist arose about 100 years earlier. DANIEL HOLZ: So Einstein came
up with general relativity in 1915. Mm-hmm. And this was his theory
to explain gravity. And Einstein’s key insight was
you can think about gravity as the curvature of space-time. RYAN WOLFF: This is Daniel Holz. He’s a physicist
on the LIGO team and a faculty member at
the University of Chicago in the Department of Physics. DANIEL HOLZ: And the Department
of Astronomy and Astrophysics and the Enrico Fermi Institute
and the Kavli Institute for Cosmological Physics. Yeah, that sounds like a
lot of different institutes. Yes. OK. So Einstein’s great
revelation was that all matter bends space and time. Gravity is actually
just the result of space-time being bent. The more massive the
object, the greater the bend. His analogy was you imagine
you have a bowling ball. You know, it’s heavy. You put it on a trampoline. It bends the trampoline. Now, if you take,
say, a little marble and you shoot it near
the bowling ball, it’ll kind of spiral
around the bowling ball. And gravity does the same thing. You take the Sun. The Sun is massive. It bends all the
space-time around it and the Earth is now
the marble and the Earth is just kind of going around. It thinks it’s going
in a straight line but because the
space-time is curved, it goes around and
around in an orbit. So gravity is pulling us down
but if something changes– suppose the Earth were to move–
then the gravity has to change. The theory of gravity
says those changes are kind of propagated out
through gravitational waves. RYAN WOLFF: Essentially,
gravity waves work like any
other kind of wave. Picture what happens
when an object falls into a pool of water. Waves are created at the
point of impact and propagate outward. The waves will
continue to travel and you could sort of get a
sense of the size of the object by the size of the waves. Gravity waves work the
same way, except instead of ripples through
water, they’re ripples through space-time. And any object, no
matter how massive, will make waves if
it’s moving around. So for example,
I’m– right now, I have some mass and I’m pulling
on the rest of the universe, not very much because
I don’t weigh that much but I’m pulling. And if I were to get up
and run across the room, then I would be pulling in a
slightly different direction. And gravitational waves go out
to the rest of the universe to say I’ve moved. RYAN WOLFF: Even though we’re
surrounded by gravity waves, they’re extremely subtle so
our best chance to detect them is to look for
waves created by the most massive cosmic events possible,
like supernova and collisions between neutron stars
and black holes. So how does one go about
detecting gravitational waves? They’re very, very
hard to detect. They’re very, very weak and so
we need an extremely sensitive instrument. And in fact, we
had to build what’s the most sensitive
instrument ever built and some say it’s the
most sensitive ruler, the most precise
ruler that’s ever been built by far to detect them. And that’s what we’ve done
over the last 20 years or so. This super precise ruler
that Daniel is referring to is known as LIGO. LIGO is comprised of
two separate detectors, one in Hanford, Washington and
one in Livingston, Louisiana. Each detector has two
four-kilometer-long arms that extend out from
the main facility perpendicular to each other. Inside each of these
arms is a laser beam that bounces back and forth
and can measure slight changes in distance, which is
basically what you need to do to detect a gravity wave. So if a wave were coming
through us right now, then what it does is it
changes the distance between us by just a little bit. We get a little closer then
a little farther apart, closer, farther apart, and
it just oscillates like that. And right now, waves are
passing through in every which way all the time. We know that. They’re– they’re–
they’re happening. OK. I don’t– I don’t
feel anything, right? You don’t feel anything. They’re very–
their waves are very small so the changes in
distance are very, very slight. Now, you really want to measure
two distances, the trick– the sort of pattern
you’re looking for that tells you, yes,
this is a gravitational wave, the distance between us and
then the distance between me and some object over here. And I want the distance to
that object to get shorter when the distance between us
gets longer and then for those to oscillate back and forth. RYAN WOLFF: So when a gravity
wave passes through LIGO, it will compress and expand
the space around LIGO and LIGO itself, making one of the
laser arms slightly shorter while the other arm
gets slightly longer. DANIEL HOLZ: Where
“slight” is not just, you know, microscopic, it’s way
smaller than the smallest thing you can normally think about. It’s way smaller than, you know,
a hair or an atom or a proton. It’s tiny, tiny fractions
on this distance. It’s a tiny fraction
of a proton. Like what fraction? What are we talking here? So on four kilometers, which
is the size of the detectors we’ve built, it’s about
1/1,000 of a proton. 1/1,000 of a proton? So– so for something
four kilometers away, that’s the amount of change in
distance you’re talking about, which is really tiny. That’s insane. 1/1,000 of a proton– that’s
like changing the distance between us and the next closest
star outside of our solar system by the width
of one human hair. So not much– Right– Basically. Very tiny. It’s kind of hard to wrap
my mind around this because, like, so we’re talking
about a laser beam that’s four kilometers long. You’re looking for a change
that’s 1/1,000 of a width of a proton. I mean, couldn’t, like–
like, a squirrel or, like, somebody sneezing, like,
cause a change like that? I mean, how do you tell
it’s a gravity wave? Absolutely. What it takes is building this
incredibly sensitive instrument and then ruling out all these. You want to isolate
all these other things. It’s just as you said. If a squirrel walks
by, you can notice that and that’s a problem. If a cloud goes over the
detector, you notice that. If there are waves crashing
on the coast far, far away, you notice that. Anything– you notice, you
know, anything that happens. So you have to control
all of those things very, very carefully. RYAN WOLFF: Even though LIGO
was built in the mid ’90s, it wasn’t until 2010
that the system underwent crucial upgrades to get it
to the sensitivity needed to detect gravity waves. Five years and over
$600 million later, Advanced LIGO was powered
on for the first time. DANIEL HOLZ: In
the last few years, we’ve gotten much better
at isolating the Earth, basically, everything that has
to do with motion of the Earth. But there’s one
thing which I’ve not mentioned which is
crucial to this, which is we have two detectors. We have one in
Hanford, Washington and one in
Livingston, Louisiana. And we want the pattern,
this alternating pattern, to happen in both detectors
essentially simultaneously. So if a squirrel is going
through one detector and causing some sort of
pattern, some oscillation, chances are that at
that very same moment, there isn’t a squirrel
going in the other detector. And then, when we finally–
which we did in September– see something which does
the exact same wiggles in both detectors at the right
travel time, then you say, oh, that’s real. So someone in Washington
calls up someone in Louisiana, like, hey, we got a wiggle. You guys have a wiggle? Exactly. That’s– that’s
basically what– I mean, a computer does it but that’s
basically what we’re doing. RYAN WOLFF: And on
September 14, 2015, two days after Advance LIGO was
powered on for the first time, the two detectors
noticed a wiggle. The nearly simultaneous
and identical patterns fit Einstein’s
prediction perfectly and couldn’t be explained by
anything other than a gravity wave. So was that like the most
exciting thing ever for you? Yeah, most exciting
thing ever by far. I mean, it was
totally incredible. To, you know, turn
on the detectors and there it is– and it
wasn’t kind of marginal, well, we’re not sure. It was like, oh, no,
this is definitely exactly what we predicted. It’s this beautiful waveform. It’s amazing. I mean, it was amazing. It’s still amazing. I still can’t– you
know, you look at it. You just can’t believe,
like, there it is. It’s just what we predicted. RYAN WOLFF: Yeah. It took over a
decade to convince the rest of the physics
community, let’s build this. This’ll really be cool
if we can get it to work. And this is one of these cases. I mean, it’s a
government agency. It’s the National
Science Foundation said, we think it’s worth doing
and spent hundreds of millions of dollars on it, even
though some people said, it’ll never work. And even if it does work. Maybe you won’t detect anything. And they just went and
pushed, pushed, pushed, improved the technology,
and then finally built this advanced detector, turned
it on, and then two days later had this, you know, one of
the most amazing discoveries I think in physics of
the last 50 or 100 years, just like that. OK. So about 100 years ago, Einstein
theorizes gravitational waves and a bunch of other stuff. And so now, they’ve
been discovered but what– what’s the big deal? Like, why is it so significant? OK. So I think there are, you
know, a number of things that make this important. What we’ve detected
is perfectly described by general relativity. And the fact that
that’s true I find, you know, quite remarkable. But I think the thing that
has people most excited, you know, within
the community– I think the thing that
really grabs us is this is just the very first event. This is just the
first thing we’ve happened to detect with this–
with this new technology, this new way of
probing the universe. The comparison that’s usually
made is it’s with Galileo. Galileo pointed, you
know, his telescope. OK, there’s some moons
going around Jupiter. That’s really interesting. But that kind of turned into our
whole notion of the universe. It has a finite age. All these things we’ve
learned about the universe comes from that very
simple first detection. And we’ve now done
the equivalent. It’s– it’s not an
optical telescope. This is now gravitational
waves but it’s opening up this whole new way
to learn about the universe. The analogy we make there is
we’re familiar with seeing and we’ve seen the universe and
we have all these telescopes. And now, we have a way to
listen to the universe. Gravitational waves
are in some ways like listening to the universe. Now, just to be 100%
clear, this is not sound. Sound is something that
happens through air. But you know, the truth
is part of the reason we use this terminology
is because if you take the actual waveform
from these systems and you just take it and you
put it into your speakers and turn up the volume, you
can hear it with the human ear. When a gravitational wave is
generated, from the very heart, you know, right by the
surface of the black holes, they now propagate through the
entire rest of the universe. No matter what’s there, it
goes right through it and right to you because they don’t
interact with anything. Right. So it’s very hard to block. So there’s– there’s
essentially, like, in some ways no limit
to how far away– Right– These waves can be emitted. So that’s– that’s–
so for example, taking that to the natural
extreme, there’s the Big Bang. Right. The Big Bang– Heard of that. There was a lot going
on in the Big Bang. We expect gravitational
waves to have been generated. Those gravitational waves,
once they’ve generated, will travel without
being changed at all throughout the universe. So if we could
detect those, we’re detecting exactly the waves that
were emitted from the Big Bang. The power to do that–
there’s no other way to probe that early
in the universe. We have some ideas of some
of the things we might hear, like black holes
crashing into each other, but there are probably
things we haven’t thought of that are happening
out in the universe and we’re going to
start to hear them. And so it’s the sort
of unknown unknowns that are most exciting. We just have no idea. We’ve just– no one’s ever
been able to do this before. So now, we have this machine
and you know, the summer, we’re going to turn on again and
we’ll– we’ll be the first ones to know what– what
the universe is saying. I mean, that’s
really– so that’s what I think the most
exciting part is, the sort of unknown future. RYAN WOLFF: For
thousands of years, human beings have been
looking into outer space but now for the very first time,
we can finally listen to it. And if we listen
real close, we’ll be able to explore the
depths of the universe further than we ever
thought possible. Hey, thanks for watching. Liking and subscribing
is something that we like and subscribe to. That’s right, Craig. Yeah. Also a big thanks to all of
our Kickstarter supporters for making the summer
season possible. And as always, if you want,
you could support us on Patreon by going to that
link over there. So what do you guys think? Are you excited
about gravity waves? What do you think they’ll
be able to tell us about our universe? Are you excited about
waves in general? Can you surf? I can’t. By the way, this is Ryan. Hi. He’s– he’s just going to
host a few shows this summer. Mm-hmm. And he really like physics. I really like physics. I’m not, like, replacing
Matt or anything and– Matt’s still alive. Yeah. Yeah. He’ll be back. Yeah. I– not only do I like
physics, I live physics. That’s– that’s true. Like, I experience it. That is very true. Last week, we tasted
some beers and talked to the guy who started
the Cicerone program and you had some
things to say about it. So I’m not familiar with
Korean so I can’t pronounce this person’s name but
they’re asking about what is a good-tasting beer. There really is no
“good-tasting” beer. It’s obviously a
matter of opinion and that issue is
kind of complicated when you consider all the kinds
of flavors of beer, especially nowadays. There are saisons and sours
and bitters and sweet. It really comes down
to what you like. Being a Cicerone
isn’t necessarily telling you what is a good beer. It’s– it’s– it’s educating
you about flavors and about how to present a beer to a
customer, about the proper ways of maintaining a beer. Personally, for a beer for
me, it depends on my mood. I often like wheat
or saison beers. Sometimes, I like a
good refreshing pilsner on a hot day, like right now. Hand me a beer. RYAN WOLFF: Oh, man. We don’t– We don’t have beer right now. RYAN WOLFF: It sounds– It’s morning. RYAN WOLFF: It
sounds really good. gmdille, Colin Sterckx,
and a number of you said that Belgium is the best
place in the world for beer. Personally, I really
like Belgian beer and I would love
to fly to Belgium and find out if that’s true,
maybe in a follow-up video. Doug Townsend took issue with
us complaining about there being too many IPAs. We’re not saying
IPA is a bad beer. In fact, I like a lot of IPAs. I’m just a little sick of them
because they’re everywhere and I’ve drank them a lot. I think the point
Ray was making is that it’s so oversaturated
that people are missing out on all sorts of other
flavors of beer. That doesn’t mean you
shouldn’t like IPAs. In fact– Yeah, I– IPA would be
my favorite style of beer, personally. I– I love the hoppiness
and the bitterness of IPAs. Yeah. I find them refreshing
and delicious. Yeah. But I could see what you’re
saying so I– I get it. Mm-hmm. IPAs are IP-A-OK. Dexter commented that Ray
reminded them of JK Simmons. Personally, I don’t agree. JK Simmons! [LAUGHTER] Thank you for watching. Next week, we have a video
all about a light bulb that’s been burning for
a long, long, long time. Whoa. How long are we talking? Three “longs.” Wow– three “longs?” Yeah. Over 100 years, I believe. Oh, OK. So “long” is about 30
years then, basically? It’s like 33 years. Yeah, that’s– look it up. That’s the technical
definition of “long.” OK.

Comments (100)

  1. I feel like there's a serious lack of beards here

  2. Just a note, you occasionally say "gravity waves". This is a different thing from "gravitational waves".

  3. Gravity go home, you're drunk

  4. Interesting stuff. I love how enthusiastic Daniel is. You always seem to choose the perfect person to interview.


  6. You just made the TIE Fighter boring.

  7. Good thing with Ryan on cam 😀

  8. You spelled Laser wrong, it's an acronym for Light Amplification by Stimulated Emission of Radiation, and last time I checked stimulated is not spelled Ztimulated 😉

  9. Just a couple weeks ago, the LISA Pathfinder ( mission results were announced by the European Space Agency. It's a testbed for LIGO-like gravity wave measurements in space. LISA Pathfinder isn't sensitive enough to measure gravity waves but was a test to see if a space-based observatory would work.

    The results are much better than expected. In the next 10 years or so, we should be able to have a space-based gravity wave observatory that is much more sensitive than LIGO!

  10. Doesn't confirming of the existence of gravitational waves after only one recorded instance go against the conventions of the scientific method? Have there been any more detections of gravitational waves since the they were first detected?

  11. If PBS is no longer funding the show then why do you have the PBS logo at the start of each episode?

  12. Beautiful video as always, guys. Keep up the incredible work

  13. Speaking of sound…let's pause for a moment and appreciate the amazing feet of sound engineering you guys pulled off by filming this with audio in such windy conditions with little to no wind noise. 🙂

  14. But how can there be a gravitational wave when the big bang happened, assuming the universe was made at that point.

  15. Imagine if LIGO and other scientific projects had the same funding the US military gets… We would have detected G-waves decades ago…

  16. This guy sounds like he has a piece of twizzler in his mouth.

  17. If gravitation waves don't interact with anything as stated, what exactly are they doing with the LIGO that's causing it to deform?

  18. are we sure we didn't detect aether wind?

  19. You say LIGO, I say Lego.

  20. I'm looking forward to LISA, the ESA's mission to put a gravitational wave detector in space

  21. what if the machine didn't pick up the energy from the black holes at all. maybe it just picked up David Pares' warp drive being switched on.

  22. This is the kind of shit that makes me excited to be alive in this era. Really uplifting.

  23. I live about 5 miles from the Hanford LIGO site. It's a big deal here.

  24. Keep the awesome video coming so stoked you guys could make these!

  25. Wow… I was captivated for the entire 16 minutes, fantastic video guys! Daniel was really interesting to listen to.

  26. Only in Chicago…..

  27. I knew this was a big deal but this video helped me understand how BIG of deal it was, hearing the beginning of the universe that's in the most real meaning of the word truly awesome!

  28. Before I clicked on the video, I thought that was Lil Dicky and a pig's snout. Would have watched the video anyways, but was super confused why the good stuff had Lil Dicky.

  29. I like Ryan's PoPS shirt.

  30. What happened to the pudgy fucker?

  31. Well you made a mistake I think, because that gravitational wave was found before the official launch doing the last test of Advanced LIGO. That said it was a pretty well made presentation of g-waves.

  32. All my life I've been told that science tries to explain away the beauty and mystery in the universe, but look at that guy's face (Daniel Holz). As a scientist myself, that's a face I see a lot – the wonder and awe at the universe itself and how it works. It seems to me like science doesn't take anything away from it, but adds to it.

  33. Has LIGO detected more waves since that first one? How frequent are events that create gravitational waves large enough to be detected?

  34. That man looked like he was so excited he couldn't explain with words what he wanted to say. Definitely interesting (and good) stuff.

  35. Hey there, very nice explanation. You showed us the wave rising, i guess up to peak, but then it gets cut. Is there a falling part of it as well? Thank you.

  36. What happened to Matt??

  37. This really is the good stuff. Thank you.

  38. so wouldn't the gravity waves of the big bang have passed us already?

  39. jk simmons? who writes these jokes? they craig me up every time

  40. congrats on getting such good sound with all that wind. Seriously.

  41. Ryan needs a beard.

  42. He looks so happy.

  43. So they stopped it after the detection? 'Cause I was going to ask if they hadn't detected anything since then

  44. brilliant video! More of this and your channel will be just fine guys ;)! Keep up the good work, bring on the science content. XD

  45. What if the waves from the big bang have already passed?

  46. Breaking News:
    The LIGO team has just announced the second detection of gravitational waves. This time the source was two colliding black holes (with masses 14 times and 8 times the mass of the sun) at a distance of 1.4 billion light years. And, for those who like serendipity, the signal was received on Christmas Day, 2015.

    This second detection emphasizes that the era of gravitational wave astronomy has begun.

  47. thumbnail looks so much like lildicky

  48. I love you guys' science videos because you really make this information easier to understand for people like me who are more art/literature oriented but who still find science wonderfully compelling.

    Also, Ryan was great! Can't wait to see him in front of the camera more.

  49. This a great video.

  50. This is so well timed guys!

  51. What a timing. they measured new waves today!

  52. This video was uploaded juuuuust before we discovered the second one!

  53. Tell Ryan that if he is going to host he needs a beard. I feel like it should be a prerequisite.

  54. long long has a range of long^2, so it's safe to assume long long long has a range of long^3, so that long is probably just shy of 5 years

  55. If they want to be isolated then why isn't there a detector in death Valley? (I'm from the Netherlands so don't know a lot about the USA but I know death Valley is a desert right)

  56. So, what IS the measurement of 1/bazillionth (1/1000th) of a proton? From what I found, it looks like on the scale of attometers (10^-18 meters) Why are so many sources unwilling to give the actual scale/value of the change in distance?

  57. Have I been gone a long time cuzzzzz who dat new guy.

  58. How the fuck this chanel doesnt have a million subscribers yet?

  59. Finally, Finally! A full explanation of this event. Thank you, guys. Thank you, thank you.

  60. question: can a distortion be smaller than a plack-lengt? i whould immagine, for isntance the gravitational wave of an ant whould be smaller than even a plack-leght if it were measured far away in a diffrent galaxy. Does this mean that there is infact no smallest length? or does the wave simply dissapear after it gotten small enough?

  61. Ryan is doing a wonderful job!

  62. Even maybe the reverb from the first G-waves that have since bounced off the edge of universe? Do they move faster than light?

  63. What an amazing time to be alive 🙂

  64. suk it space time

  65. Great video! I thought it would be just another video about gravitational waves, but the interview made it unique! It was awesome! Guys like Daniel and team are the kind people who I see as true heroes of mankind!

  66. Thank to dark matter it"s possible that we may able to find strings
    in the universe and I think we detected dark matter thanks to these waves
    during second detection(source science alert) and also enable to know new
    thing like if waves or faster than light and so on.

  67. There is a big mistake in this video. Gravity waves and Gravitational waves are not the same. Gravity waves is the effect of tidal forces and gravity on fluids, such as oceans and air in the atmosphere. Gravitational waves, on the other hand, are changes in the fabric of space-time itself, like described… Get that sorted out please.


  69. Nice job explaining this on a level that makes it understandable, but without drumming it down to much! Really well done, keep up the good work!

  70. We need three 3-axis LIGOs in space outside of the Earth's gravity well so we can do 3 dimensional location. Time to step up our game. I'm willing to pay an extra dollar/year in taxes for that.

  71. They call it a vibe.

  72. I won't make the comment about either or Craig's moms.

  73. I like the guy that is not matt, I like Matt too but not matt is also good. hope that makes sense.

  74. I wonder if gravitational waves could set off earthquakes.

  75. Knowable things are divided in three categories:
    1) The things we know
    2) The things we don't know
    3) The things we don't know that we don't know

  76. What a complete fucking pack of lies. There is no such thing as "Gravity
    Waves". Anybody that would believe this nonsense is just a stupid as
    the shitheads peddling these lies. Its amazing how you can just show
    people some pretty computer animations and they totally fall for this
    shit hook, line and sinker…

  77. The correct spelling is laser, not lazer, even in American English :).

  78. wow, it's completely incredible.

  79. Ryan did so well as co-host!

  80. Why do the gravitational waves detected at LIGO Hanford not exactly match with the waves detected at LIGO Livingston?

  81. Before you head to Lame Ass Austin, check out Carlyle Brewery in Rockford, IL. The Humulus Lupulos, an IPA, will blow your mind. It's dank beer. Suitable for family and friends, you'll keep it all to yourself anyway.

  82. But how did they know that it was a black holes collision that caused the shock wave? why they didn't assume that it might be a supernova for example or any other massive incident?

  83. Is it just me or did he get a bit choked up? I know I did.

  84. Hahaha that ligo guy sounds a bit like Jar Jar Binks 😂

  85. so space can be warped, and perhaps we can have an warp speed space ship 🙂

  86. Why don't they show footage of the black holes that they supposedly captured on their telescope? oh wait… they don't have footage…. IF THEY HAD ACTUAL FOOTAGE THEY WOULDN'T BE CGI'ing everything.

  87. So you're saying we have gravity waves so massive that they have pulled our planet into an orbit with the sun…. but we can't detect those waves….. but for some reason we can detect the waves from two black holes light years away? uh huh…. i'm calling bullshit on this one. But enjoy my tax dollars….

  88. First ones?????????????

  89. didnt know lil dicky was a physicist

  90. Is it my eyes, or my ears, DETECT his words & body language as if he is an entertainer.


  92. wouldnt the gravity waves generated by the big bang have travelled so far away from the initial centre of the universe that they would be way out at the reaches of infinity somewhere and thus too late for us to detect, gone far far away?

  93. Am I the only one that thinks he looks like lil Dicky?

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