[thedoc (OP)]

Grant Skinner asked the Naked Scientists:
   it seems that there is an opposite for most things - matter, anti-matter and so on.  Is there such a thing as the opposite of light such as an anti-light or dark-light (rather than just dark)
What do you think?

[Colin2B]

As discussed here http://www.thenakedscientists.com/forum/index.php?topic=65608.0

[the5thforce]

mass reflects light, and since a true vacuum is impossible even opposites are part of the same spectrum- in this case mass is the opposite of light on the energy spectrum.