Tyson's story of light starts in the caves humans originally lived it. Did a passing shadow inspire the first cave artists? Some cute kid with a wig and a piece of charcoal turns into a visionary.
Tyson leaves speculation and starts getting into history with Mozi, a Chinese philospher alive about 400 years BCE, who was the first to discover the camera obscura, which is literally a small hole through which light can enter a darkened room. The light is reflected onto a white surface, and presto!
Upside down TV!
Despite the fact you'd have to watch hanging upside down from the ceiling, the camera obscura was pretty neat and also is similar to how we see, which might have tipped off ancient scientists. Mozi also contributed a pacificism to rival Ghandi's and a 3-part test for believing in any faith system: What is the belief based on? How is the belief applied? Who benefits from the belief? Instead of building on Mozi's work, future rulers of the new Ch'in Empire banned and burned it whenever they could find it, leaving only fragments of Mozi for us to find.
Ibn Al-Haytham (Al-Hazen) was a bit luckier, living in Iraq during the 10th and 11th centuries. During this time, it was the Islamic world that had the best libraries and places to study. Arab scientists named the stars, and gave the world algebra and the number 0. They also conducted experiments to understand the physical properties of their world. Al-Haytham, when he wasn't pretending to be crazy, studied light, and how it worked. Al-Haytham took the work of Mozi and reproduced it with a tent, making the smallest possible hole. discovering that light actually moves in straight lines through any one medium. He, to the relief of moviegoers everywhere, discovered focus, which is really just making an aperture smaller to capture light from a tighter area. When Galileo finally used a telescope in 1609, the principle of using a lens to collect more image from the sky, and another lens to focus the image, it was based on Al-Haytham's work centuries before.
Al-Haytham didn't stop there. Like other Arab scientists at the time, he wanted a way to know if he was at least on the right track to knowledge and truth. But how does one discover things no god has told you about? How do people discover things on their own? Al-Haytham began defining something we would later call the scientific method. And it's ennabled humanity to stop taking anything on faith. Al-Haytham's was a little simpler than the current one, with only three principles: question what others say; use evidence from experiment; and question your own assumptions. In other words, try to eliminate stupid mistakes.
Failed at controlling the Nile, though
Newton expanded on Al-Haytham's work. Where Al-Haytham "focused" (ha-ha) on aperture, Newton focused on medium. Intellectuals knew that light refracted, but they only knew the half of it. Newton worked with prisms to separate out the colors of white light, and by noting the difference between the shape of light hitting the prism, and the shape of light as it exited the prism, could deduce that colors were different properties of the light themselves, that traveled in slightly different directions due to some property of that color of light.
William Herschel, played by a silent Patrick Stewart this time, takes Newton's discoveries further. Herschel, by accident, figured out that red light "had" more heat than blue, and decided to figure out how much. So, he set up a prism with light so that each color was separated out, then placed a thermometer inside each color stream. In order to provide a "control" to measure the other colors by, he placed a thermometer off to the side of the red, just in the shade. Now, he'd have a neutral color. Or so he thought. When he examined that thermometer, it was warmer than all the others, even the red light. Herschel had just discovered infrared light. And he opened up a whole new "spectrum".
Really, he just helped expand the electromagnetic spectrum beyond the colors. We would later discover that each new ray we find is a whole new way of seeing: gamma rays help see exlplosions and distant galaxies; microwaves help us 'see' the Big Bang itself.
Distant galaxies above the NYC Skyline
But Joseph von Fraunhofer found out enough about the spectrum to invent a whole new form of astronomy. Fraunhofer, orphaned in early childhood, found himself "adopted" by a greedy tyrant who worked Joseph day and night in his glass factory and home. What could have been a tragedy for Joseph turned out to be his life's great stroke of luck when his adopted "dad"'s house caved in. Two men responded to the tragedy - future emperor Maximilian I Joseph, and Max's main councilor, Joseph Utzschneider. Both took some sort of shine to Joseph, some poor orphan kid who was probably woefully undernourished and, due to the evil adopted "father", uneducated. Max and Joe helped little Joseph attend school over the wishes of evil adopted "father", and later provided for his education and research in a top-secret government lab.
Emperor Max's brush with scientific greatness
Back in the early 1800s, top-secret work for the Bavarian military-industrial complex was done at a Benedictine Monastery, full of monks with no lives and vows of silence. And the work was making glass. The best glass on the planet. Fraunhofer turned out to be a great investment by the Bavarian Emperor; he went on to create the best light-bending glass in the world for his time. He was so important, as he lay dying in 1826, only the Minister of Coin had the necessary security clearance to take down Fraunhofer's knowledge of glass-making.
But not light. That Fraunhofer released to the public whenever his experiments bore fruit. Fraunhofer didn't realize, but he layed the groundwork for discovering photons later, by identifying one of their most important qualities: they are the building blocks of light (as well as the rest of the spectrum), and they travel at different speeds in different mediums. Not only that, but different wavelengths of photons travel at different speeds in the same medium. Each photon "bumps" into the atoms that make up whatever they're traveling through, and atoms of different elements block each wavelength differently.
Inventing astrophysics
That sounds ridiculously complicated. Long story short: when you put a magnifying glass between a prism and the surface getting the rainbow, you'll see a collection of dark lines scattered throughout the spectrum. Those dark lines represent light photons that got blocked by an atom of a particular element. That particular element will always block the same light photons in the spectrum. So, if you blow a gas through a vacuum, you can see the light "signature" of that gas in the spectrum. Combine them for every gas in our atmosphere, and you have the light "signature" of our atmosphere. Fraunhofer invented the Spectrometer.
The light signature for my butt
Learn the signatures of every element, and you can point your prism/telescope at the other planets and figure out what's in their atmospheres. And you can realize that it corresponds to the same elements you've already found all over Earth. And you can realize that the same elements are scattered throughout the universe.
Fraunhofer's work established that by using light rays differently, we could actually discover new information. So, whenever someone discovers a new ray on the electromagnetic spectrum, we can discover new information about the universe. We can even discover stuff out there and confirm it neither reflects, absorbs or emits light. We can call it dark matter, and discover even more cool stuff about light itself by studying things that do something (or nothing) with light that we don't know about. Yet.
We call it "unlight"
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