• Question: What is Red Shift? And what is it used for?

    Asked by freddie to Adam, Geoff, Rob, Sheila, Suzie on 15 Mar 2011 in Categories: .
    • Photo: Geoff McBride

      Geoff McBride answered on 14 Mar 2011:

      This comes up in astromomy where the light from a Galaxy coming towards is blueish because the wavelength of the light is squashed [blue shift]. If it is moving away the wavelength is streatched becoming redish [Redshift]. You can’t see it with the naked eye but you can hear the siren of a police car change in tone as it passed in this case the sound waved are squashed and streatched.

    • Photo: Sheila Kanani

      Sheila Kanani answered on 14 Mar 2011:

      Redshift is when light is shifted towards the red end of the spectrum.
      You can hear an equivalent with sound when an ambulance comes towards you and then away from you and the sound of the siren becomes more high pitched then goes back to normal. This is called the Doppler effect and is similar to Redshift.
      The light changes colour because its wavelength increases. The wavelength increases because the light source is moving away from you. You can get blueshift, which is the exact opposite as the light is moving towards you.
      Redshift is useful because it tells us everything is moving away us, and the universe is expanding.
      The higher the redshift, the further away the object is. For example, the cosmic microwave background has a redshift of z = 1089, corresponding to an age of approximately 379,000 years after the Big Bang!

    • Photo: Adam Tuff

      Adam Tuff answered on 14 Mar 2011:

      Red shift is caused by the “stretching” in frequency of sound or light from an object that is moving – you can hear it when an ambulence or a police car goes by as the tone of the siren changes! You can use this to figure out how fast something is moving – red shift means that the frequency is (in the case of light) shifted towards the red end of the spectrum (but it doesn’t mean that is changed to red). If we see light from, say, a star, and the spectrum is red shifted, it’s wavelength is increased, we know the star is moving away from us. We can also get the reverse, which is called blue shift, which we see when an object is moving towards us, and the light is shifted towards the blue end of the spectrum. It is used a lot in astronomy (not just using light, but with radio astronomy and high-energy astronomy), to tell how fast things are moving towards ans away from us.

    • Photo: Robert Simpson

      Robert Simpson answered on 15 Mar 2011:

      Red Shift is a measure of the distortion of light as it is stretched out by the Universe’s expansion, it is used to measure the distance to things in the Universe.

      Remember that light is a wave and imagine a beam of light heading out from a distant galaxy towards you. It’s going to have to travel for a very long time and during that time, the Universe expands a bit. The light is part of the Universe and so it expands as well. If you stretch out a wave, it gets longer and in the case of light, that means it gets ‘redder’ because red light has a longer wavelength than blue light. How much the light has been stretched depends on how much the Universe has expanded since it started travelling.

    • Photo: Suzie Sheehy

      Suzie Sheehy answered on 15 Mar 2011:

      Redshift (or blueshift) happens when a source of light is travelling either toward (red) or away (blue) from you. It can be used to tell how fast an object is travelling toward/away from you!

Comments