Question: How does the ALMA use radio waves to detect what compounds/molecules/elements are in different parts of space?
I am currently doing a project looking in depth at radio waves and how they can analyse different compounds in space and thought that the ALMA was the best example.
Many Thanks. — Josh
Answer: Atoms and molecules absorb and emit at discrete frequencies that we can measure spectroscopically. What we do is take the radio-wavelength light that we gather with our radio telescopes and spread it out into its constituent frequencies, much in the same that a prism spreads visible light into the colors of the rainbow). This then allows us to measure the intensities of the discrete emission and absorption frequencies from atoms and molecules, which in-turn allows us to study the properties of the gas that emitted the atomic and molecular emission.