There's an interesting volley online right now between two science journalists I admire, Michael Moyer and Robert Krulwich, over the color pink. In a blog post for NPR last week, Krulwich was shocked to learn from a video that pink does not exist, and Monday Moyer responded with his own ontological take.
Pink is not found in the ROYGBIV electromagnetic spectrum. But that does not mean it isn't a color! There's a key distinction between colors of light and of pigment, between additive color and subtractive color, that everyone seems to be glossing over.
The World Health Organization estimates that around one sixth of the world lacks access to clean drinking water. Since those billion people are also the poorest people in the world, water purification techniques need to be cheap to help those most in need. Since it activates under plain visible light, this new water-purifying photocatalyst may help bring purer water to the world's neediest people.