How do we know that supergiants are larger than giants?
This is a great question! Quirkie is correct, here is an explanation of his answer… The terms “interferometry” and “interferometer” are both derived from the word interference. Interference is a phenomenon that occurs when one has waves of any kind — sound waves, light waves, ocean waves, seismic waves from earthquakes — it makes no difference. Whenever two waves comes together at the same time and place, interference occurs. Resonance, beat frequencies, hetrodyning, dissonance, are also all interference phenomena. Interference can be visualized as the adding together of two waves with each other. Depending on wave size (amplitude) and the degree to which they are in or out of step with each other (phase), they will either add together or cancel. The canceling out is still really an “addition”; in this case, it’s like adding plus one to minus one. In astronomy, we will be dealing with the interference of two light waves. If both waves are in step or in phase, that is, the crest
