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Redshift & Blueshift

What causes Redshifts & Blueshifts? And based on what causes them, what are they exactly?

We are really getting into the physics of things. These shifts are complicated things to explain, however here goes.


The picture above is a good starting point, so look at it again after you understand more about these shifts, as it will make more sense to you.

Its all about wavelengths for both Redshifts & Blueshifts. Wavelengths expanding for a Redshift, and wave lengths reducing for a Blueshift. 

Redshifts Explained

Redshifts are, for a start, Red. Redshifts are based the ‘Doppler Effect’ that was named after scientist Christian Doppler who is credited with coming up with the system of explaining Redshifts as proof that the universe is forever expanding. The effect is a change in frequency of a wave of acceleration in the universe. A good simple example of explaining the Doppler Effect would be to imagine and ambulance coming towards out with its siren on. When approaching you the noise of the siren is compressed together, giving the wave a high frequency. When the ambulance reaches you, you can hear the true sound, and when it passes you, a different sound is made from the wave, giving a low frequency as it passes, until the wave is gone, and you cannot hear the ambulance anymore. This is shift in wave, of a Doppler Shift. When stars are moving away from other stars or objects at acceleration, this is a Redshift. This is noticeable by the Red tint in the star when observed.

Blueshifts Explained

Blueshifts are Blue and are the opposite of Redshifts. So its a little complicated, because if the very widely known theory of the continued expansion of the universe, and acceleration of stars away from each other is 100% accurate, how can a Blueshift occur? Good question. Take the galaxy next to us, Andromeda. While stars in that galaxy may be moving away from each other in the galaxy, it is widely confirmed that our nearest neighbour is actually moving towards the Milky Way, where at some stage in the very distant future both galaxies will collide, to form a new super galaxy. This is happening already, and is also noticeable by the Blue tint when observing the galaxy.


So, Redshifts are Red and Blueshifts are Blue, and this is proven by the colour of light emitted from the stars. Told you it was complicated, however you should understand more about these shifts now.


Kids Fun Facts Corner

# 1. Redshifts are in fact Red in color.

# 2. Blueshifts are in fact Blue in color.

# 3. Scientist Edwin Hubble has been credited with further confirming the Redshift phenomenon through extensive study now known as Hubble’s Law.   

# 4. Light and wave lengths from the Andromeda galaxy are Blueshifts.


Q&A Corner

Q. What color light is emitted from Redshifts? 

Q. What color light is emitted from Blueshifts? 

Q. Do the wave lengths of Redshifts expand or reduce?

Q. Do the wavelengths of Blueshifts expand or reduce?

Q. What is the law known confirming Redshifts?

Download questions about Shifts here: Shifts (answers are on this page)

For further reading and more information on Shifts visit 

  Key Vocabulary Galaxy. Milky Way. Andromeda. Wavelengths. Frequency. Expand. Reduce.


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