What is redshifts?

Answer 1

Redshift is an example of a phenomenon called the Doppler Effect in which light waves are elongated when an object moves away from the observer. The Doppler Effect occurs when something that emits wave energy (commonly light or sound) is traveling toward an observer or away from an observer, and in doing so, causes the wavelengths that the observer records to be compressed or elongated.

Traffic noise is a common example of the Doppler Effect. Everyone has had the experience of standing beside a road and listening to the pitch of a fast moving car change as the car passes by you. Before the car passed you, it was traveling toward you, and the sound waves emanating from the car were compressed before they reached you, giving the car an apparently higher pitched noise than it really emitted. After the car passed by, and was by then travelling away from you, the sound waves from the car were elongated before they reached you, making the pitch of car's noise apparently lower than before it passed you.

Light waves are subject to the same phenomenon. When a distant star

moves toward our planet, we observe compressed light waves as they reach Planet Earth, and we perceive the shortened wavelengths as colors universally shifted toward the blue end of the spectrum (called blue shifting). Similarly, when a distant star moves away from Planet Earth, we perceive the emitted light waves to be elongated, and the stretched wavelengths appear to us as colors shifted toward the red end of the spectrum (called red shifting).

In astronomy, we can compute the exact amount of shifting for certain stars by passing the incoming starlight through a spectrographic sensor, and then by comparing the received light wavelengths against the known wavelengths of emission. There are four universal wavelengths of hydrogen emission, for example. By comparing a hydrogen burning star's received starlight to the known wavelengths of hydrogen emission, we can calculate not only if the light is blue shifted (the star is travelling toward us) or red shifted (away from us), but also by how much. Thus we can accurately measure the velocity at which the star is traveling (the shift) along the radial axis from Planet Earth to the star.

For a complete discussion of red shifting, follow the Related Link below to a Wikipedia article on Red Shifting.

Note that the term redshift is usually applied to visible light, or light of optical wavelengths. But the Doppler effect applies to any electromagnetic waves generated by these receding objects. A link can be found below.

Answer 2

Hubble said "redshifting" "is a hitherto unknown principle of nature." Unfortunately, not too many physicists listen to Hubble. Red shifting is a measure of direction not motion.

Redshifting indicates direction away from the center. If the direction is perpendicular to the radial center there is no shift. If toward the center there is blue shift, if away form the center there is redshift. The shift is cos(z) when the cosine is positive there is red shift. If the cosine is negative there is blue shift. If the cosine is zero there is no shift it is perpendicular.

Answer 3

A method for determining the distance stars uses a concept call red shift where light from a star is more red due to its motion.