Let's listen to a melody from the universe !

Illustration：Sora

Studium Generale 2019. 11. 15 Nagoya University
Seiji Kawamura (Nagoya University)
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Question 1

Do you think
we can listen toa melody fromthe universe?
Sora
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What is gravitational wave?
• Derived from generalrelativity by Einstein• Detected for the firsttime recently• Can propagate invacuum• Same speed as light3/46

We should be able to hear GWs!
GWs

Year drum

http://haservice.jp/chuuji. html

Sora
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Too small to hearGWs

10-24 mAtomSoraImpossible to hear!
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Super ear aid

Super ear aid

GW detector

Sora
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Answer 1

Yes, we canlisten to a
melody from theuniverse with asuper ear aid.
Sora
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Detection method
GWs
MirrorMirrorBeam Splitter

Photodetector
Interfering light

Laser
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GW detectors around the world

U GO (4 km)
https://www.ligo.caltech.e
du/image/ligo20150731e

GEO (600 m)
http://www.geo600.uni-hannover.de/GEOvisit/

KAGRA (3 km)
https://www.ligo.caltech.ed
u/image/ligo20191004b

U GO- ndia (4 km)

U GO (4 km)https://www.ligo.caltech.
edu/image/ligo20150731c

V RGO (3 km)
http://lappweb.in2
p3.fr/virgo/gw.html

https://www.gw.iucaa.in/

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LIGO

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We did it ! (February 2016)

Video removed due to copyright
restrictions

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Coalescence of black hole binary
1.3 G light year awayVideo removed due to copyright
restrictions

29 solar mass

36 solar mass

62 solar mass after coalescence
SXS
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Detected real
GW melody!

LIGO

15

https://www.ligo.c
altech.edu/news/ligo20171206

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Video removed due to copyright restrictions

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Video removed due to copyright restrictions

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Coalescence of neutronstar binary (August 2017)https://www.ligo.caltech.edu/image/ligo20171016d
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Video removed due to copyright restrictions

Detected real GW melody

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Detected real GW melody

LIGO-Virgo/Geoffrey Lovelace, Duncan Brown, Duncan Macleod, Jessica McIver, Alex Nitz

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Spectrogram

LIGO-Virgo/Geoffrey Lovelace, Duncan Brown, Duncan Macleod, Jessica McIver, Alex Nitz

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Question 2Do you thinkthe universe isexpanding?
Sora

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Einstein equation
Einstein tensor

Energy momentum
tensor𝐺𝜇𝜈 = 𝜅𝑇𝜇𝜈
How much spacetime is distorted

How muchenergy exists

Sora
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Solution for the universe
Mathematically
predicted theexpansion of theuniverse from theEinstein equation
https://en.wikipedia.org/wiki/Al
exander_Friedmann

Alexander Friedmann

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Einstein’s belief

The universe
must beeternally static!
Sora

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Cosmological constant
Einstein tensor

Energy momentum
tensor𝐺𝜇𝜈 = 𝜅𝑇𝜇𝜈
+Λ𝑔𝜇𝜈
Sora
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Observation
The universe
was found tobe actually
expanding!
https://en.wikipedia.org/wiki/Edwin_Hubble

Edwin Hubble

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Answer 2
Yes, the universeis expanding.
Sora

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Biggest blunder
Einstein labelled
the cosmologicalconstant his“biggest blunder”.

Sora
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Question 3
Do you think
Einstein reallymade biggest
blunder?
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Acceleration of theexpansion of the universe
The expansion ofthe universe wasfound to beaccelerating!
https://hub.jhu.edu/201
Adam G. Riess 4/11/10/adam-riessbreakthrough-prize/

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Dark energy
Essentiallyvery similar
to thecosmologicalconstant
Figure removed due to copyright
restrictions

Star wars
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The universe consists of…
?
?

?
NASA
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Dark = invisible
What isessential isinvisible to theeye.

The little prince

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Sora

Yes, Einsteinmade a mistakein saying that hemade biggest
blunder.
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Question 4
Do you think we
can listen to thebirth cry of theuniverse?
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Looking far to see the past

M78 nebula:
3 million years ago
https://ja.wikipedia.org/wiki/M7
8_(天体)

Figure removed due tocopyright restrictions

Sirius:9 years ago©pixabayMoon:
1 second ago

Sora
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Going backward in time

©pixabay

13.8 billion year
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How close to the birth of theuniverse can we see
Birth of theuniverse
10-35 second

Gravitational
wave

Electro magneticwave

380 kilo year
13.8 billion year
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Inflation•10-35 second
20•Expanded by 10•Similar to dark energy?

•GWs expected to emit
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Sora

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Answer 4

Sora

Yes, we canlisten to the birth
cry of theuniverse with
DECIGO.
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I want to listen
to the birth cryof the universe

Illustarion: Sora

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If you wantto know
moredetails

Figure removed due to copyright restrictions

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