• Question: how is it possible to attempt to guess the size of the universe and how can scientist be sure how the universe was created?

    Asked by 08abarnes to Evan on 15 Jun 2011. This question was also asked by jackmorris.
    • Photo: Evan Keane

      Evan Keane answered on 15 Jun 2011:

      Good question!

      Well one way is to work out what the furthest away thing we can see is, because the Universe must be at least that big, right? Astronomers do this by measuring the “redshift” of galaxies. I’ll explain what that means. You know when an ambulance drives past and as it gets closer to you the sound gets more high-pitched? And then when it goes past you it gets lower-pitched as it moves away? Well the pitch is from the frequency of the sound waves, high frequency = high pitched, low frequency = low pitched. The same thing happens with light, because it has a frequency too. With light, when something moves away from you it appears to have a lower frequency as well. And as red light is low frequency (blue light is high frequency) it seems redder if it is moving away from us. This is what astronomers call “red shift”. So if a galaxy is moving away from us it appears redder (red-shifted) and if it is moving towards us it appears bluer (blue-shifted).

      Looking at galaxies we can see that they are almost all redshifted (moving away from us, because the Universe is expanding). If we measure the redshift we can measure how far away they are and get a guess of how big the Universe is. BIG!

      There is a really cool animation you can look at to see the different sizes of EVERYTHING IN THE WHOLE UNIVERSE!! Here it is:

      http://www.primaxstudio.com/stuff/scale_of_universe/

      You can zoom all the way inside atoms and all the way out to the whole Universe!

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