A question has been bothering me for some time - when we look at the sun, what are we looking at? The standard answer is - the photosphere. The sun consists mostly of hydrogen and helium, and that the radiation from the photosphere is approximately a black body continuum spectrum at 6000K with some absorption lines in the visible light range. However, in atmospheric physics, we learn that diatomic molecules like O2 and N2 as well as noble gases like Argon neither absorb nor emit infrared nor visible radiation, because they are symmetric and have no dipole moment. Their energy levels are so far apart that they only interact in the UV. This the reason why the atmosphere is transparent to visible light, and why N2 and O2 cannot act as greenhouse gases, whereas H2O and CO2 do. I have a problem trying to reconcile these two pieces of information, which seem to contradict each other. H2 and He are just like O2, N2 and Argon, diatomic or noble gases. If visible light from the photosphere is radiated by He and H2 at 6000K, why do N2 and O2 on earth at 300K not radiate or absorb at infrared wavelengths? I haven't seen any explanation of this contradiction. I suppose either a) the sun's light is not coming from the photosphere but a lower layer or b) O2 and N2 do indeed absorb visible and IR, but the interaction is so minimal that it can be ignored. Is one of these correct, or is there another explanation? T.