Research done at Nikhef. Gravitational waves. Gideon Koekoek January 10 th 2007. Overview of the talk. What are gravitational waves? Measuring gravitational waves What we @ Nikhef / Vu are doing Conclusions. What are gravitational waves?.
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Research done at Nikhef
January 10th 2007
What are gravitational waves?
1st Law: motion in straight lines if there is no force.
Wait, what is gravity in the first place?
Gravity is a force!
Earth’s path is not straight, but bent by a force
Gravity is not a force; it’s the curvature of space (and time)
Still a straight line, but in curved spacetime!
This is a very small number! ~ 10-45 (!!)
You need a lot of energy to curve spacetime; gravity is weak!
Q: What curves spacetime? A: energy does!
Ok, good. Now about those gravitational waves..
Flat spacetime, plus a little curvature
Curvature in the vacuum?
A wave equation: a curvature hμυ oscillates through space!
An example: gravitational waves produced by a binary star system
We want to measure these waves!
Binary stars: source of GW’s
Measuring gravitational waves
Theory: is General Relativity correct?
Astronomy: what is Dark Matter/Dark Energy made of?
Astronomy: information on interesting systems are carried by GW’s
Cosmology: with GW’s we can see back to the Big Bang!
Wait! Why would we do that in the first place?
A blessing and a curse: GW’s interact
Blessing: once produced, they can’t be disturbed
Curse: very difficult to measure them ourselves!
Note: a million times smaller than a proton!
Amplitude and frequency of gravitational waves emitted by a binary system of masses M1 and M2 at separation r
A: with an interferometer!
Fabry-Perot cavities: increase the arm length
Q: How to measure gravitational waves?
Idea:if a GW comes by, the length of the arms is disturbed: phase difference between the arms →interference pattern
LISA(US + EU)
5 106 km arms
These things actually exist!
4 km arms
3 km arms
What we @ Nikhef/Vu are doing
Theory of gravitational waves
Hardware, data analysis,.…
Nikhef has taken and carried out the initiative to start a research group focusing on gravitational waves