Question: What is red shift and is there an explanation for dark matter

Thomas Barrett answered on 10 Mar 2015:

Red shift is part of the doppler effect. The Doppler effect is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. Red shift means it is moving away from us, and blue shift means it is coming towards us.

Dark matter is basically something we need to make all our equations work. No one is really sure what it is or why it is so hard to find.

Here is a video on Dark matter
http://www.open.edu/openlearn/science-maths-technology/science/across-the-sciences/60-second-adventures-astronomy-0?track=8

Small explanation of Doppler Effect
http://www.open.edu/openlearn/science-maths-technology/science/across-the-sciences/60-second-adventures-astronomy-0?track=13