I'm from engineering background and not firmly familiar with cosmological equations and concepts. but i know what Redshift is and how it is related to the Doppler effect.
My question is how scientists know that the Redshift is related to the moving of the object and not related to the local effects such as the material of that object. how they know this Redshift is due to moving and not local events in that object like the nuclear reactions on the object or maybe it's because of the medium between observer(us) and the source. I will appreciate if the answer will be in simple words for non physicists.