Soru

Passage:
For early twentieth-century astronomers, interstellar space was largely conceived as an unmeasurable void, primarily because optical telescopes could not penetrate the dense clouds of cosmic dust that obscured the Milky Way’s galactic plane. The advent of radio astronomy in the 1930s initially met with skepticism from a discipline entrenched in visual observation. However, the theoretical prediction of the 21-centimeter neutral hydrogen spectral line by H. C. van de Hulst in 1944, followed by its experimental detection by Harold Ewen and Edward Purcell in 1951, fundamentally transformed observational astrophysics. Rather than merely confirming the existence of interstellar gas, the detection of the 21-centimeter line provided astronomers with a powerful diagnostic tool capable of mapping the spiral structure of the Milky Way through cosmic dust clouds. Consequently, radio astronomy transitioned from a peripheral engineering curiosity to a central discipline of modern astrophysics. By demonstrating that non-optical electromagnetic radiation could unveil previously invisible galactic structures, Ewen and Purcell’s empirical breakthrough invalidated the assumption that optical observational boundaries defined the limits of cosmic inquiry.

Based on the passage, which of the following statements accurately express the main idea or primary purpose of the text? Select all that apply.