In 1998 the journal Nature published a seminal letter concluding that the mysterious polarization (a particular property of light) that had been recently observed in the solar sodium D1 line implies that the solar chromosphere (a very important layer of the solar atmosphere) is practically unmagnetized, in sharp contradiction with common wisdom. This paradox motivated laboratory experiments and theoretical investigations which, instead of providing a solution, raised new issues and even led some scientists to question the quantum theory of radiation-matter interaction. Here, we have carried

We perform a new test of Einstein's Equivalence Principle which, for the first time, extends to very early cosmological epochs (we have studied its validity in 80% of the history of the Universe). The Einstein Equivalence Principle is essential for generalizing physical laws in the presence of gravity. Our test of the Equivalence Principle is based on one of Einstein's classical predictions: the gravitational redshift of photons. This test has been accurately put into practice in our Solar System and in some stars in our Galaxy (e.g. Sirius B). However, so far it has not been applied to

The black holes at the centres of galaxies are the most mysterious objects in the Universe, not only because of the huge quantities of material within them, millions of times the mass of the Sun, but because of the incredibly dense concentration of matter in a volume no bigger than that of our Solar System. When they capture matter from their surroundings they become active, eventually giving rise to the ejection of huge amounts of energy. It is however difficult to detect the black hole during these capture episodes because the event is rare. We detected l ong and narrow dust filaments