Fundamental Physics with the SKA:Strong-Field Tests of Gravity Using Pulsars and Black Holes

The Square-Kilometre-Array (SKA) will be a radio telescope with a collecting area that will exceed that of existing telescopes by a factor of a hundred or so. This contribution summarises one of the key-science projects selected for the SKA. The sensitivity of the SKA allows us to perform a Galactic Census of pulsars which will discover a large fraction of active pulsars beamed to us, including the long-sought for pulsar-black hole systems. These systems are unique in their capability to probe the ultra-strong field limit of relativistic gravity. By using pulsar timing we can determine the properties of stellar and massive black holes, thereby testing the Cosmic Censorship Conjecture and the No-Hair theorem. The large number of millisecond pulsars discovered with the SKA will also provide us with a dense array of precision clocks on the sky. These clocks will act as the multiple arms of a huge gravitational wave detector, which can be used to detect and measure the stochastic cosmological gravitational wave background that is expected from a number of sources.