• Question: Why is it called the spectrum?

    Asked by to Mike on 17 Mar 2014. This question was also asked by .
    • Photo: Mike Lee

      Mike Lee answered on 17 Mar 2014:

      Hi,

      Why is the spectrum called the spectrum….

      To me, a spectrum means a range of different things. This is why we use the word to describe light – it’s because it comes in a different range of colours – red, blue, green, purple (my favourite), and so on.

      Did you know that there is some colours that you cannot see? Xrays are just light rays that are bluer than blue. Often, in physics, there seems to be lots of different things, but these turn out to be just examples of the same thing.

      Another thing you might not know is – if something is moving towards you it actually looks bluer, and if it moving away, it looks red. This difference is usually too small to notice, but scientists have used this fact to find out that most of the stuff in the universe is actually moving away from us. From this we reason that the whole universe is expanding. No one knows why the universe is doing this.

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