What is redshift and blueshift?

Assuming a star is speeding toward Earth, its light waves will be compressed, or pushed together. In fact, the entire spectrum of an approaching star appears to be slightly shifted toward the blue end of the spectrum, a phenomenon known as the "blue shift," because shorter wavelengths of light are characteristics of both violet and blue light.

The red shift is the slight shift in the spectrum that results from a star moving away from the earth, which causes the light waves to appear longer than they actually are. Since longer wave lengths are associated with the red end of the spectrum, the red shift is the result of the star's spectrum appearing to be slightly expanded.

Redshift and blueshift are terms used in astronomy to describe the shift in the wavelength of light emitted by an object due to its motion relative to an observer. Redshift occurs when an object is moving away from the observer, causing the wavelength of light to appear longer and shifting towards the red end of the spectrum. Blueshift occurs when an object is moving towards the observer, causing the wavelength of light to appear shorter and shifting towards the blue end of the spectrum. These phenomena are a result of the Doppler effect, where the relative motion between the source of light and the observer causes a change in the observed wavelength.