Let There Be Light, Review, Cosmos Episode 5
At start, no has lyte. An Ceiling Cat sayz, i can haz lite? An lite wuz —Lolcat Bible
Note :1nm = 10-9m
It is as if Neil De Grasse Tyson read my last review, and decided to give us the physics behind the light show of last week. He covered a lot of ground, this week. This episode began its exploration of light with geometric optics and pinhole cameras and ended with speculation about dark matter. This week’s history lesson told us about the contributions of the ancient Chinese experimentalist and philosopher, Mozi, and the Arab philosopher-scientist Alhazen, of the ancient Indian mathematical concept of zero. An excellent counterpoint to those who insist that Christianity was an essential aspect of the scientific revolution. Unfortunately Mozi’s teachings did not survive the Chinese thought police. Like the Inquisition era Catholic Church they too were afraid of the open exchange of ideas. No one has a monopoly on either the smart or the stupid but the cultures that allow an open exchange of ideas flourish, while those who stifle them, don’t in the long run.
Continuing our exploration of light, Tyson revisited Isaac Newton and his discovery of the spectrum of visible light. Newton figured out that sunlight or white light is a composite of the seven primary colors, VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange and Red). Newton was not the main star of Sunday’s Cosmos, instead it was Joseph Fraunhofer, for his contributions to spectroscopy. He was the first to observe the solar spectrum with a telescope and analyze it. De Grasse Tyson then described the atomic structure of hydrogen, and quantum mechanical explanation of its spectrum. He then generalized it to atoms of elements more complicated than hydrogen. Thus looking at the spectrum of a heavenly body we can figure out what it is made of.
In a brilliant graphic Tyson demonstrated how the New York skyline changed when we focused on the different parts of the electromagnetic spectrum. The different parts coinciding with different wavelengths. To explain the concept of a wavelength, Tyson compared light waves and sound waves. Missing however was any mention of Thomas Young, who experimentally proved the existence of the wave nature of light. Also, there was no mention of Newton’s corpuscular theory of light which had to be eventually discarded since it could not explain interference and diffraction.
What I love about physics in particular and science in general, that it does not matter whether you are Newton or Einstein, if what you say does not agree with experiment your theories have to go. Put up or shut up. Physics does not bow to the rules of the thought police.
Tyson still has to discuss the wave-particle duality. Though, he briefly touched on quantum mechanics while discussing the hydrogen atom he has yet to talk about the Uncertainty Principle. I am sure that the quantum revolution of the early part of the last century will be the subject of a future episode. The changes it brought about, in how we perceive both matter and light were radical. As is always the case, that revolution too had its own thought police.