Science of the Rainbow

The spectrum depends upon light of different colours being slowed by different amounts: the refractive index of a given substance, say glass or water, is greater for blue light than for red. You could think of blue light as being a slower swimmer than red, getting tangled up in the undergrowth of atoms in glass or water because of its short wavelength. Light of all colours gets less tangled up among the sparser atoms of air, but blue still travels more slowly than red. In a vacuum, where ther...

 Why Plants Evolved to be Green

why is green the dominant color of terrerestrial plants? That's easy. Chlorophyll molecules absorb light at the red and blue ends of the spectrum. It is the middle of the spectrum (the green part) that is reflected and gives plants their characteristic color. A more efficient photosynthetic pigment would be black, absorbing all colors, soaking up all the energy of sunlight, reflecting nothing. The reflected green light of plants is wasted energy. So perhaps the real question is. Why isn't gra...

 How Photosynthesis Builds Energy Against Entropy

No law of physics is more basic than the law of entropy, the tendency of the universe to move toward disorder and death. But life bucks the tide. using available free energy wherever it can get it, and hereabouts the most abundant source of energy is sunlight. The mayflower constructs its tiny oasis of order by drawing upon a corresponding increase of disorder at the center of the Sun, where hydrogen is fused into helium. There, deep at the heart of our planet's star, is the source of the ene...