Tag Archives: Red Shift

Doppler Effect and Red Shift

Today I thought I would write about the Doppler Effect and Red Shift. What are they? Why do they occur? Why do we refer to Red Shift in the field of cosmology and astrology?

Red Shift is the name given to the perceived ‘shifting’ of waves through the spectrum from our perception. It gives us a measure of speed, or expansion, as is often the case. It can also called Blue Shift, and this is essentially the opposite of Red Shift. However, for the purposes of this post I shall refer to both of them as Red Shift unless otherwise stated.

Have you ever noticed the change in pitch when an object passes you at high-speed? Let’s take an ambulance or a Formula 1 car as an example. As it approaches we hear a higher than normal pitch, but as soon as the sound source starts to move away from us we hear a sudden drop in the pitch of the sound emanating from the source. Most people are aware of this phenomenon, but not so many fully understand it. It is useful for us to understand this, as it is almost the same as Red Shift, or at least it shares enough similarities with the Doppler Effect to be very useful towards our understanding of it. The effect I have just described to you has a special name, the Doppler Shift or the Doppler Effect, named after Christian Doppler who first proposed the effect in 1842.

A visual example of the Doppler Effect

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