  Towards the end of the 19th century, Kelvin pronounced as the "clouds of
physics" 1) the failure of the Michelson-Morely experiment to detect an ether
wind, 2) the violation of the classical mechanical equipartition theorem in
statistical thermodynamics. And he believed that the removal of these clouds
would bring physics to an end. But as we know, the removal of these clouds led
to the two great breakthoughts of modern physics: 1) The theory of relativity,
and 2) to quantum mechanics. Towards the end of the 20th century more clouds of
physics became apparent. They are 1) the riddle of quantum gravity, 2) the
superluminal quantum correlations, 3) the small cosmological constant.
Furthermore, there is the riddle of dark energy making up 70% of the physical
universe, the non-baryonic cold dark matter making up 26% and the very small
initial entropy of the universe. An attempt is made to explain the importance
of these clouds for the future of physics. Conjectures for a possible solution
are presented. they have to do with Einstein's last query: "Can quantum
mechanics be derived general relativity", and with the question is there an
ether?
