Red shift
From Simple English Wikipedia, the free encyclopedia
Red shift is a way astronomers use to tell the distance of any object that is very far away in the Universe. To understand how they detect red shift, you have to understand the Doppler effect.
[edit] Doppler effect
The easiest way to imagine the Doppler effect is to listen to a moving train. As the train moves towards you, the sound it makes as it comes towards you sounds like it has a higher tone, since the frequency of the sound is squeezed together a little bit. As the train speeds away, the sound gets streched out, and sounds lower in tone. The same happens with light when an object that emits light moves very fast. An object, like a star or a galaxy that is far away and moving toward us, will look more blue than it normally does, and a star or galaxy moving away from us will look more red than it should, which is where red shift got its name, since the colors are shifted red.
The reason astronomers can tell how far the light gets shifted is because certain chemical elements, like the calcium in your bones or the oxygen you breathe has a unique fingerprint of light that no other chemical element has. They can see what colors of light are coming from a star, and see what it is made of. Once they know that, they check to see the difference between where the fingerprint, called spectral lines, are actually at, and then look at where they are supposed to be. When they see that, they can tell how far the star is, whether it is moving toward us or away from us, and also how fast it is going, since the faster it goes, the farther the distance the spectral lines are from where they should be.
[edit] Overall importance
The reason red shift is as important as it is, is because astronomers used it to figure out that the Universe is expanding, and even expanding faster than they thought it was before, which was a question many astronomers asked, and couldn't figure out before they discovered how to use red shift.
