Complex sentence: These questions, aswell as many others, were much debated all through the seventeenth century, with many theories circulating through the astronomical community, and with Galileo claiming that comets were an optical phenomena, and that this made their parallaxes impossible to measure.
Split into simpler sentences: These questions, along with many others, were heavily debated during the seventeenth century, with many theories circulating within the astronomical community. Galileo claimed that comets were an optical phenomena, and that this made their parallaxes impossible to measure.