Why have the more distant galaxies had their light shifted from visible to infrared wavelengths?
Answer Hello Stephanie, Here is some background information which you may already know, but I want to make sure we are on the same page when the explanation starts. BACKGROUND – Billions of years ago, the universe came into existence through an event called the “big bang” and started rapidly expanding from nothing into the universe we see today. It has been getting bigger ever since. So the first stars and galaxies that formed are now at the edge of the universe and are moving away from the younger ones, increasing in separation as time goes by. Waves coming from objects that are moving with relation to us have their wavelength shifted depending on their motion. Electromagnetic waves coming from approaching objects have their wavelengths shortened. They are lengthened for objects moving away from us. This is the Doppler Effect. This happens with sound waves too. You have probably heard the example of the pitch of a train horn sounding as it approaches and passes you. The pitch of the h
