I can imagine that the sun does not always emit the same amount of radiation of the various frequencies everywhere. Could it be that, for example, I see my blue vase bluer one moment than the next (hypothetically not counting the rotation of the earth)?
Answer
Indeed, the sun does not emit the same amount of radiation at every frequency, but the amount of radiation at a certain frequency is really constant. So if you were to measure outside the Earth’s atmosphere at, for example, 450 nm (blue), at 550 nm (green) and at 650 (red), you will always get the same result, at least over a period of billions of years.
If your vase sometimes looks different, it has everything to do with the fact that your vase is located within the atmosphere. The color will therefore be influenced by the atmospheric conditions (amount of clouds…) and the time of day (is the sun high or low on the horizon, because at a low position you get a redder sunlight).
So if we were to place your vase in a vacuum outside the atmosphere, it would always look the same.
Answered by
prof.dr. Paul Hellings
Department of Mathematics, Fac. IIW, KU Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.