Allan Adams What the Discovery of Gravitational Waves Means

8/16/2019 Allan Adams What the Discovery of Gravitational Waves Means

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00:111.3 billion years ago, in a distant, distant galaxy, two black holes locked

into a spiral, falling inexorably towards each other and collided, converting

three Suns' worth of stu into pure energy in a tenth of a second. !or that brief

"o"ent in ti"e, the glow was brighter than all the stars in all the galaxies in

all of the known #niverse. $t was a very big bang.

00:%&ut they didn't release their energy in light. $ "ean, you know, they're

black holes. (ll that energy was pu"ped into the fabric of space and ti"e

itself, "aking the #niverse explode in gravitational waves.

01:0%)et "e give you a sense of the ti"escale at work here. 1.3 billion years

ago, *arth had +ust "anaged to evolve "ulticellular life. Since then, *arth has

"ade and evolved corals, sh, plants, dinosaurs, people and even -- od save

us -- the $nternet. (nd about / years ago,a particularly audacious set of

people -- ai 2eiss at $4, 5ip 4horne and onald 6rever at 7altech -- decided

that it would be really neat to build a giant laser detector with which to search

for the gravitational waves fro" things like colliding black holes.

01:%8ow, "ost people thought they were nuts. ut enough people reali9ed

that they were brilliant nuts that the #S 8ational Science !oundation decided to

fund their cra9y idea. So after decades of develop"ent, construction and

i"agination and a breathtaking a"ount of hard work, they built their detector,

called )$: 4he )aser $nterfero"eter ravitational-2ave bservatory.

0/:1!or the last several years, )$'s been undergoing a huge expansion in

its accuracy, a tre"endous i"prove"ent in its detection ability. $t's now called

(dvanced )$ as a result.

0/:/;$n early Septe"ber of /01, )$ turned on for a nal test run while they

sorted out a few lingering details. (nd on Septe"ber 1% of /01, +ust days after

the detector had gone live,the gravitational waves fro" those colliding black

holes passed through the *arth. (nd they passed through you and "e. (nd

they passed through the detector.

0/: Scott ?ughes: 4here's two "o"ents in "y life "ore e"otionally

intense than that.ne is the birth of "y daughter. 4he other is when $ had to

say goodbye to "y father when he was ter"inally ill. @ou know, it was the

payo of "y career, basically. *verything $'d been working on -- it's no longer

science ctionA =)aughs>


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face. $nstead, we use sound to listen for features like pitch and tone and

rhyth" and volu"e to infer a story behind the sounds.4hat's (lice

talking. 4hat's ob interrupting. Silly ob.

0F:3/So, the sa"e is true of gravitational waves. 2e can't use the" to "ake

si"ple i"ages of things out in the #niverse. ut by listening to changes in the

a"plitude and freGuency of those waves, we can hear the story that those

waves are telling. (nd at least for )$, the freGuencies that it can hear are in

the audio band. So if we convert the wave patterns into pressure waves and

air, into sound, we can literally hear the #niverse speaking to us. !or exa"ple,

listening to gravity, +ust in this way, can tell us a lot about the collision of two

black holes, so"ething "y colleague Scott has spent an awful lot of ti"e

thinking about.

0;:1F=(udio> S?: $f the two black holes are non-spinning, you get a very si"ple

chirp: whoopA $f the two bodies are spinning very rapidly, $ have that sa"e

chirp, but with a "odulation on top of it, so it kind of goes: whir, whir, whirA $t's

sort of the vocabulary of spin i"printed on this wavefor".

0;:3%((: So on Septe"ber 1%, /01, a date that's denitely going to live in "y

"e"ory, )$ heard this:

0;:%/H2hirring soundI

0;:%So if you know how to listen, that is the sound of --

0;:0=(udio> S?: ... two black holes, each of about 30 solar "asses, that were

whirling around at a rate co"parable to what goes on in your blender.

0;:


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core, and the core is hidden behind thousands of kilo"eters of iron and carbon

and silicon. 2e'll never see through it, it's opaGue to light. ravitational waves

go through iron as if it were glass -- totally transparent. 4he ig ang: $ would

love to be able to explore the rst few "o"ents of the #niverse, but we'll

never see the", because the ig ang itself is obscured by its own

afterglow. 2ith gravitational waves, we should be able to see all the way back

to the beginning. Kerhaps "ost i"portantly, $'" positive that there are things

out there that we've never seen that we "ay never be able to see and that we

haven't even i"agined -- things that we'll only discover by listening.

0&:%/(nd in fact, even in that very rst event, )$ found things that we didn't

expect. ?ere's "y colleague and one of the key "e"bers of the )$

collaboration, att *vans, "y colleague at $4, addressing exactly that:

0&:=(udio> att *vans: 4he kinds of stars which produce the black holes that

we observed here are the dinosaurs of the #niverse. 4hey're these "assive

things that are old, fro" prehistoric ti"es, and the black holes are kind of like

the dinosaur bones with which we do this archeology. So it lets us really get a

whole nother angle on what's out there in the #niverse and how the stars ca"e

to be, and in the end, of course, how we ca"e to be out of this whole "ess.

10:/1((: ur challenge now is to be as audacious as possible. 4hanks to )$,

we know how to build exGuisite detectors that can listen to the #niverse, to the

rustle and the chirp of the cos"os. ur +ob is to drea" up and build new

observatories -- a whole new generation of observatories -- on the ground, in

space. $ "ean, what could be "ore glorious than listening to the ig ang

itselfL ur +ob now is to drea" big. 6rea" with us.

10:14hank you.

10:/=(pplause>

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Allan Adams What the Discovery of Gravitational Waves Means