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Gravitational waves

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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Gravitational waves

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  1. Research done at Nikhef Gravitational waves Gideon Koekoek January 10th 2007

  2. Overview of the talk • What are gravitational waves? • Measuring gravitational waves • What we @ Nikhef / Vu are doing • Conclusions

  3. What are gravitational waves?

  4. 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

  5. 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!

  6. 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..

  7. Flat spacetime, plus a little curvature What are gravitational waves? Curvature in the vacuum? A wave equation: a curvature hμυ oscillates through space!

  8. 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

  9. Measuring gravitational waves

  10. 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 waves Wait! Why would we do that in the first place?

  11. 10-45 (!!) 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!

  12. Note: a million times smaller than a proton! Measuring gravitational waves Amplitude and frequency of gravitational waves emitted by a binary system of masses M1 and M2 at separation r

  13. A: with an interferometer! Fabry-Perot cavities: increase the arm length Measuring gravitational waves 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

  14. LISA(US + EU) 5 106 km arms Launch: ~2015 Measuring gravitational waves These things actually exist! LIGO (US) 4 km arms VIRGO (EU) 3 km arms

  15. What we @ Nikhef/Vu are doing

  16. Theory of gravitational waves Hardware, data analysis,.… You? What we @ Nikhef/Vu are doing Nikhef has taken and carried out the initiative to start a research group focusing on gravitational waves Management

  17. Conclusions

  18. 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

  19. Conclusions Interested to do a Masters? Contact Tjeerd Ketel ( TJ.Ketel@few.vu.nl) or Jo van den Brand ( jo@nat.vu.nl) The end

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