Short answers, pulled from the story.
Belle Époque means "beautiful era" in French. The period lasted from the end of the Franco-Prussian War in 1871 until the outbreak of World War I in 1914. The name was applied in retrospect, after two world wars made the preceding decades appear, by contrast, like a golden age.
Captain Alfred Dreyfus was wrongly convicted of treason using fabricated evidence from French government officials, and antisemitism directed at him was widely tolerated in French society. The affair consumed France for years and drew heavy newspaper coverage. Novelist Émile Zola's open letter J'Accuse...! condemned both government corruption and French antisemitism directly, making the case a landmark of public political controversy.
Henri Becquerel discovered radioactivity in 1896. Marie Skłodowska-Curie won the Nobel Prize for Physics in 1903 and the Nobel Prize for Chemistry in 1911. Louis Pasteur developed pasteurisation and a rabies vaccine. The germ theory of disease was finally established during this era, founding the field of bacteriology.
Art Nouveau was a decorative style characterised by curvilinear forms and nature-inspired motifs. It became prominent from the mid-1890s and spread across Europe and beyond. Hector Guimard applied it to the Paris Métro stations, making it synonymous with the city.
Dancers and singers including Polaire, Mistinguett, Paulus, Eugénie Fougère, La Goulue, and Jane Avril were Paris celebrities. Liane de Pougy, described as dancer, socialite, and courtesan, headlined the top cabarets. Several of these performers modelled for Henri de Toulouse-Lautrec's iconic poster art.
France was a leader in aviation during this period. France established the world's first national air force in 1910. Two French inventors, Louis Breguet and Paul Cornu, each made independent experiments with flying helicopters in 1907.