It is 100 years since Albert Einstein submitted his Theory of General Relativity, a pillar of modern physics that has transformed our understanding of space, time and gravity. <br />Most of the predictions that he made back in 1915 have subsequently been confirmed. But one remains elusive - the direct detection of gravitational waves. <br />Now, a number of observatories around the world are trying to get a glimpse of these phenomena for the first time. <br />BBC Science Correspondent Rebecca Morelle went to see one of the wave-hunting machines - Advanced Virgo, near to Pisa, in Italy.
