Energy gives rise to weight when it is trapped in a system with zero momentum, where it can be weighed. It is also equivalent to mass, and this mass is always associated with it. Mass is also equivalent to a certain amount of energy, and likewise always appears associated with it, as described in mass-energy equivalence. The formula E = mc², derived by Albert Einstein (1905) quantifies the relationship between rest-mass and rest-energy within the concept of special relativity. In different theoretical frameworks, similar formulas were derived by J. J. Thomson (1881), Henri Poincaré (1900), Friedrich Hasenöhrl (1904) and others (see Mass-energy equivalence#History for further information).
In what year did Einstein create E = mc2?
1905

David Attenborough was later granted sabbatical leave from his job as Controller to work with the BBC Natural History Unit which had existed since the 1950s. This unit is now famed throughout the world for producing high quality programmes with Attenborough such as Life on Earth, The Private Life of Plants, The Blue Planet, The Life of Mammals, Planet Earth and Frozen Planet.
When did the BBC Natural History Unit come into existence?
the 1950s

Many women played an essential part in the French Enlightenment, due to the role they played as salonnières in Parisian salons, as the contrast to the male philosophes. The salon was the principal social institution of the republic, and "became the civil working spaces of the project of Enlightenment." Women, as salonnières, were "the legitimate governors of [the] potentially unruly discourse" that took place within. While women were marginalized in the public culture of the Ancien Régime, the French Revolution destroyed the old cultural and economic restraints of patronage and corporatism (guilds), opening French society to female participation, particularly in the literary sphere.
Which event destroyed the former patronage and corporatism of France and allowed women to participate in society?
French Revolution