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Strong gravity theory and gravitational waves U. Sperhake DAMTP , University of Cambridge Cambridge Science Festival Einsteins Legacy: 100 years of general relativity Cambridge, 19 th March 2015 U. Sperhake (DAMTP, University of Cambridge)

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Strong gravity theory and gravitational waves

U. Sperhake

DAMTP , University of Cambridge

Cambridge Science Festival Einstein’s Legacy: 100 years of general relativity Cambridge, 19th March 2015

U. Sperhake (DAMTP, University of Cambridge)

Strong gravity theory and gravitational waves 19/03/2015 1 / 18

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There are 4 fundamental forces

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Gravity is special!

Acts on everything No screening from gravity → feature of spacetime!

U. Sperhake (DAMTP, University of Cambridge)

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General Relativity: Curvature

Curvature generates acceleration No “force”!! Einstein: spacetime is curved!

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How do we calculate this?

Solving this equation is our job...

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We need supercomputers... E.g. Cosmos at DAMTP

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Strong gravity = non-linear

What is non-linear? Think of the stock market: ⇒ linear ⇒ NON-LINEAR!

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Strongest gravity = black hole

Time goes upwards

green = future red = past

Strong curvature ⇒ everything moves inwards ⇒ Black hole

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Black-hole analogy

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Are black holes real?

Since 1960s: very likely yes! X-ray binaries 1964 Stars near galactic center

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Are black holes real?

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Research areas: Black holes have come a long way!

Astrophysics GW physics Gauge-gravity duality High-energy physics Fundamental studies Fluid analogies

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Gravitational Waves

Black-hole / Neutron-Star binaries generate ripples in spacetime Changes in length: < atomic nucleus per km Indirect evidence: 1993 Nobel Prize Hulse & Taylor

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How can we measure this? I On ground

Principle: Michelson-Morley interferometer

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How can we measure this? II In space

∼ Million km interferometer

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How can we measure this? III Using space

See Michael Kramer’s presentation

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What will we learn?

Early Universe Look into neutron stars Test Einstein’s theory Black-hole populations Galaxy formation The Unknown...

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A new window to the Universe... ... often reveals new ideas!

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