4. Gravitational waves as the ultimate relics
Because Einstein’s equation describes the cosmological
evolution, one may say that the Universe is powered
by gravity. Thus gravitational waves provide a unique
window on the Universe and its evolution. Even though
there is an indirect evidence of their existence through
the Hulse-Taylor pulsar [18], they remain to be detected
directly, either through the next generation of advanced
P. Binétruy / Nuclear Physics B (Proc. Suppl.) 243–244 (2013) 165–171 169
ground interferometers or through the future space missions,
such as the eLISA mission [19] presently proposed
in the context of the Large missions of the European
Space Agency. Given the focus of this conference,
I will take most examples from the rich programme of
this mission (see also K. Danzmann presentation at this
conference).