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## PowerPoint Slideshow about ' Gravitational waves' - harding-mercer

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Presentation Transcript

Overview of the talk

- What are gravitational waves?
- Measuring gravitational waves
- What we @ Nikhef / Vu are doing
- Conclusions

1st Law: motion in straight lines if there is no force.

What are gravitational waves?Wait, what is gravity in the first place?

Gravity is a force!

v

F

Earth’s path is not straight, but bent by a force

Gravity is not a force; it’s the curvature of space (and time)

What are gravitational waves?- Newton does not agree with Relativity,
- All matter behaves the same under gravity

Einstein disagreed..

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!

What are gravitational waves?Q: What curves spacetime? A: energy does!

Ok, good. Now about those gravitational waves..

Flat spacetime, plus a little curvature

What are gravitational waves?Curvature in the vacuum?

A wave equation: a curvature hμυ oscillates through space!

What are gravitational waves?

An example: gravitational waves produced by a binary star system

We want to measure these waves!

Binary stars: source of GW’s

Us

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!

Measuring gravitational wavesWait! Why would we do that in the first place?

Measuring gravitational waves

A blessing and a curse: GW’s interact

very weakly

Blessing: once produced, they can’t be disturbed

Curse: very difficult to measure them ourselves!

Note: a million times smaller than a proton!

Measuring gravitational wavesAmplitude and frequency of gravitational waves emitted by a binary system of masses M1 and M2 at separation r

Fabry-Perot cavities: increase the arm length

Measuring gravitational wavesQ: 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

5 106 km arms

Launch: ~2015

Measuring gravitational wavesThese things actually exist!

LIGO (US)

4 km arms

VIRGO (EU)

3 km arms

Hardware, data analysis,.…

You?

What we @ Nikhef/Vu are doingNikhef has taken and carried out the initiative to start a research group focusing on gravitational waves

Management

Conclusions

- Gravitational waves are ripples in spacetime that travel with velocity c;
- They can teach us a lot about binary star systems, Dark Matter/Dark Energy, the Big Bang.. etc etc;
- Measuring GW’s is difficult; it can be done by using interferometers;
- Nikhef is working (both experimentally as theoretically) on Virgo and LISA

Conclusions

Interested to do a Masters?

Contact Tjeerd Ketel ( [email protected]) or

Jo van den Brand ( [email protected])

The end

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