We can know about distant stars temperature,its elements etc by observing its spectra... But that star has a velocity related to us... The spectra will be shifted... Then how do we know the correct spectra?
Another ques... Suppose, something emits a X ray... Then will its characteristic will change(gamma or visible light) for observers with relative velocity?
Another ques... Suppose, something emits a X ray... Then will its characteristic will change(gamma or visible light) for observers with relative velocity?