What key observational uncertainty drove the 18th and 19th-century 'Great Debate'?
Answer
Whether spiral nebulae were local gas clouds within the Milky Way or distant, external star systems.
The Great Debate centered on the scale of the universe; observers could only measure angular size and brightness, making it impossible to distinguish if spiral nebulae were local phenomena or separate 'island universes' far away.
Related Questions
What is the literal meaning of the Latin term *nebula*?What was Charles Messier's primary motivation for cataloging deep-sky objects?What type of astronomical object is Messier 1 (M1), the Crab Nebula?What key observational uncertainty drove the 18th and 19th-century 'Great Debate'?What analytical tool became crucial in differentiating true nebulae from spiral nebulae (galaxies)?What do true nebulae, distinct from spiral nebulae, primarily consist of and where are they located?Why were planetary nebulae so named, despite having nothing to do with planets?What object remains at the core of a star after it sheds its outer layers to form a planetary nebula?Which modern instrument capability allows astronomers to see protostars hidden within star-forming regions?How has the focus of astronomical discovery shifted regarding nebulae since the time of early catalogers?