• Question: How can a red shift look red when there would still be the same amount of blue visible, it's just the gamma rays which are just shifted? Because the visible light is just in the middle of the spectrum, surely it wouldn't make a difference?

    Asked by anon-106860 to Adrian, Gaia, Jim, Scott, Vicky on 10 Mar 2016.
    • Photo: Adrian Buzatu

      Adrian Buzatu answered on 10 Mar 2016:

      All the colours, either visible, or invisible, would be shifted a bit to larger wavelengths, so more towards red. The spectrum would shift to the right. Some of the visible light would become infrared and thus not visible. Some of the non visible light (ultraviolet) would become violet and thus visible.

    • Photo: Scott Lawrie

      Scott Lawrie answered on 10 Mar 2016:

      Thanks for the question, Ki. I understand where you’re coming from: how is there ‘room’ for just visible light to move around? Red-shift is a bit of a poor name. If you know about wavelengths, then red is long wavelength and blue is shorter wavelength. This is just visible light, though, and you’re right that it forms only a tiny part of the entire spectrum: longer wavelengths than visible light are things like microwave and radio; shorter wavelengths are UV, gamma etc. By ‘red-shift’ we mean ALL wavelengths are moved toward the longer end of the spectrum. It could very well have been called ‘Radio-shift’!

      I hope that makes sense 🙂

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