Visible light is only a narrow sliver of what's actually out there. The full electromagnetic spectrum runs from long, low-energy radio waves through microwave, infrared, the visible rainbow, ultraviolet, X-ray, and finally short, high-energy gamma rays. Every band carries different information: cool gas and dust glow in infrared and radio; the blazing-hot surfaces of young stars shine brightest in ultraviolet; violent, high-energy events — black holes feeding, exploding stars — show up strongest in X-ray and gamma-ray.
Earth's atmosphere is not equally transparent to every wavelength. Only two bands pass through easily enough to observe comfortably from the ground: visible light and radio waves. Infrared is partially blocked — usable from a dry mountaintop or an aircraft, but often better from space. Ultraviolet, X-ray, and gamma-ray radiation are blocked almost entirely; observing in those bands requires a telescope in orbit, above the atmosphere altogether.
Click a band to see whether Earth's atmosphere lets it through.
A radio telescope works on the same basic principle as an optical reflector — a curved dish collects and focuses the incoming waves — but radio wavelengths are thousands of times longer than visible light, which relaxes the precision needed in the dish's surface. That's part of why radio dishes can be enormous: the 500-meter FAST telescope in China dwarfs any optical mirror ever built.
Radio astronomers also combine multiple dishes into an interferometer — arrays like the VLA (27 dishes) or ALMA (66 dishes) — letting widely separated telescopes act together as one much larger, much sharper virtual instrument.
A real instrument pitch has to line up three decisions at once: wavelength (what does the science question actually need to detect?), location (does that wavelength reach the ground, or does it need space?), and aperture and design (how much light-gathering and resolving power does the target demand, and does that favor a lens, a mirror, or a dish?).
Your science question: map the cold gas and dust inside a star-forming nebula, in detail too fine for existing telescopes to resolve.