What is associated with: around 1675 gian domenico cassini observed a dark gap in this planets main rings?

What is associated with: around 1630 jan van helmont discovered this gas given off by burning wood called it gas sylves… Based on the clue 'around 165 bc this jewish leader re entered jerusa...', what is the answer? What is associated with: around 1650 bc these people made their capital at hattusas in central anatolia in what is now… What is associated with: around 1668 isaac newton built the first reflecting one of these? What is associated with: around 1683 jules hardouin mansart completed this narcissistic versailles feature galerie des… What is associated with: around 1700 this a ships steering system was improved by adding a wheel? What is associated with: around 1709 cristofori became a key player in this new instruments history? What is associated with: around 1714 he set the freezing point of water at 32 degrees the boiling point at 212?