I was rather concerned by speculation that white dwarf stars could harbour habitable planets simply because these stars emit light at the right wavelengths to sustain photosynthesis (18 August, p 8).
Surely anywhere life evolves it will utilise the dominant wavelengths from the local star. It is not divine providence that has made our eyes most sensitive to the wavelengths emitted most strongly by our sun, and for which plant photosynthesis is optimised. Those wavelengths are what our eyes and plants have evolved to use.
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