Space Warps Talk


  • falconusa1 by falconusa1

    Anupreeta. Do giant gaseous galaxies reflect light and images off into space like a mirror; and in a much more rare event reflect the image of a lens?


  • Tom_Collett by Tom_Collett scientist

    Hi Falcon. No they don't act like mirrors; you need a flat surface that can't be penetrated by light to act as a mirror. Galaxies are very low density, so any external light hitting them travels a long way into the gas before it is likely to be deflected. Because there is no hard flat edge, the photons tend to end up going in pretty much all directions.

    It's a bit like shining a torch into fog - a bit of light might come back at you, but most of it doesn't.

    This effect can be a cool way of weighing clusters (google sunyaev zeldovic effect).


  • falconusa1 by falconusa1 in response to Tom Collett's comment.

    Hi Tom. Thank you for this wonderful answer and example. I understand where the definition of a mirror applies.

    Hopefully soon science will detect and hold the photons in place before they scatter.

    And for your guides to the lateral study.


  • drphilmarshall by drphilmarshall scientist, admin

    I guess Hanny's Voorwerp is a nice example of gas reflecting (some) light!


  • falconusa1 by falconusa1 in response to drphilmarshall's comment.

    O my yes, thank you Dr. Phil for reminding me of this treasure!