Gravitational waves
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Transcript of Gravitational waves
Gravitational wavesGravitational waves
Gideon KoekoekGideon KoekoekJanuary 10January 10thth 2007 2007
Research done at NikhefResearch done at Nikhef
Overview of the talkOverview of the talk
What are gravitational waves?What are gravitational waves?
Measuring gravitational wavesMeasuring gravitational waves
What we @ Nikhef / Vu are doingWhat we @ Nikhef / Vu are doing
ConclusionsConclusions
What are gravitational waves?What are gravitational waves?Wait, what is Wait, what is gravitygravity in the first place? in the first place?
Earth’s path is not straight, but bent by a Earth’s path is not straight, but bent by a forceforce
1st Law: motion in straight lines if there is no force.
FF
vv
2r
mMGF
Gravity is a force!
What are gravitational waves?What are gravitational waves?Einstein disagreed..Einstein disagreed..
Still a straight line, but in Still a straight line, but in curvedcurved spacetime! spacetime!
Gravity is not a force; it’s the curvature of space (and time)
Newton does not agree Newton does not agree with Relativity,with Relativity,
All matter All matter behaves the behaves the samesame under gravity under gravity
What are gravitational waves?What are gravitational waves?Q:Q: What curves spacetime? What curves spacetime? A:A: energy does! energy does!
T
c
GRgR
4
8
2
1
Ok, good. Now about those gravitational Ok, good. Now about those gravitational waves..waves..
You need a lot of energy to curve You need a lot of energy to curve spacetime;spacetime; gravity is weak! gravity is weak!
This is a very small number! ~ This is a very small number! ~ 1010-45-45 (!!) (!!)
What are gravitational waves?What are gravitational waves?
hg
Flat spacetime, plus a little curvatureFlat spacetime, plus a little curvature
02
1 RgR
A wave equation: A wave equation: a curvature a curvature hhμμυυ oscillates oscillates through space! through space!
01
2
2
22
2
hdt
d
ch
dx
d
Curvature in the vacuum?Curvature in the vacuum?
What are gravitational waves?What are gravitational waves?
An example:An example: gravitational waves gravitational waves produced by a binary star systemproduced by a binary star system
We want to measure these
waves!
UsUsBinary stars: source of GW’sBinary stars: source of GW’s
Measuring gravitational wavesMeasuring gravitational wavesWait!Wait! Why would we do that in the first place? Why would we do that in the first place?
Theory: Theory: is General is General Relativity correct?Relativity correct?
Astronomy: Astronomy: information on information on interesting systems are interesting systems are carried by GW’scarried by GW’s
Cosmology: Cosmology: with GW’s we with GW’s we can see back to the Big can see back to the Big Bang!Bang!
Astronomy: Astronomy: what is Dark what is Dark Matter/Dark Energy made Matter/Dark Energy made of? of?
Measuring gravitational wavesMeasuring gravitational wavesA blessing and a curse: GW’s interact A blessing and a curse: GW’s interact
veryvery weakly weakly
T
c
GRgR
4
8
2
1
1010-45-45 (!!) (!!)
Blessing:Blessing: once produced, they can’t be disturbed once produced, they can’t be disturbed Curse:Curse: very difficult to measure them ourselves! very difficult to measure them ourselves!
2110~
L
L
Measuring gravitational wavesMeasuring gravitational waves
Amplitude and frequency of gravitational waves emitted by a binary system of masses M1 and M2 at separation r
Note: a million times smaller than a proton!
Measuring gravitational wavesMeasuring gravitational wavesQ:Q: How to measure gravitational waves? How to measure gravitational waves? A: A: with an interferometer! with an interferometer!
Idea:Idea:
if a GW comes by, the if a GW comes by, the length of the arms is length of the arms is disturbed: phase disturbed: phase difference between the difference between the arms arms →→interference patterninterference pattern
Fabry-Perot cavities: increase the arm length Fabry-Perot cavities: increase the arm length
Measuring gravitational wavesMeasuring gravitational wavesThese things actually exist! These things actually exist!
LIGO LIGO (US)(US)
VIRGO VIRGO (EU)(EU)
4 km arms4 km arms
3 km arms3 km arms
LISALISA (US + EU)(US + EU)
Launch: ~2015 Launch: ~2015
5 105 1066 km arms km arms
What we @ Nikhef/Vu are doingWhat we @ Nikhef/Vu are doing Nikhef has taken and carried out the initiative to start a Nikhef has taken and carried out the initiative to start a
research group focusing on gravitational waves research group focusing on gravitational waves
ManagementManagement
Hardware, data Hardware, data analysis,.…analysis,.…
Theory of Theory of gravitational gravitational waveswaves
You?You?
ConclusionsConclusions
Gravitational waves are ripples in spacetime that travel with Gravitational waves are ripples in spacetime that travel with velocity velocity c;c;
They can teach us a lot about binary star systems, Dark They can teach us a lot about binary star systems, Dark Matter/Dark Energy, the Big Bang.. etc etc;Matter/Dark Energy, the Big Bang.. etc etc;
Measuring GW’s is difficult; it can be done by using Measuring GW’s is difficult; it can be done by using interferometers;interferometers;
Nikhef is working (both experimentally as theoretically) on Virgo Nikhef is working (both experimentally as theoretically) on Virgo and LISAand LISA
ConclusionsConclusionsInterested to do a Masters?Interested to do a Masters?
Contact Contact
Tjeerd KetelTjeerd Ketel ( ( [email protected]@few.vu.nl ) ) or or
Jo van den BrandJo van den Brand ( ( [email protected]@nat.vu.nl ))
The endThe end