Cosmos Recap: We Bet You Didn't Understand All The Stuff About Spectroscopy Either

This week’s episode of Cosmos, “Hiding In The Light,” is all about light and the spectrum, and how an assortment of scientists came to understand something about how light works. This episode seemed somehow shorter and jumpier than others in the series, though I’m not sure I can put a finger on why — maybe it’s just that there’s no single moment in this week’s outing that prompted an “Oh, WOW” as in some of the earlier outings. Even so, it’s still Neil deGrasse Tyson doing history of science, so that makes up for a lot.


We start off in ancient China, with the story of Mo Tzu, the showman in the video up top, who experimented with light and dabbled in the philosophy of science, including, unfortunately for the survival of his works, an insistence upon questioning all ideas and testing whether they can be verified and found to be useful. And then we see Mo Tzu’s books being burned by the first Chinese emperor, Qin, giving Tyson the opportunity to remind us that “Science needs the light of free expression to flourish. It depends on the fearless questioning of authority and the free exchange of ideas.” OK, freedom to question: good.

Next, on to Basra, Iraq, in the 11th century, and Ibn al-Haytham, or Alhazen if you like your Arabic names Latinized (we’ll go with the latter, since that’s the show’s pronunciation). In another mostly animated segment, we get a mini-lesson in the scientific achievements of the Arab world of those times — great, Neil, you’re not satisfied with pissing off the creationists? Now you’re going to stir up the Pam Gellers, too? But we learn about the role they played in preserving the knowledge of the ancient Greeks, and about their importation of what came to be called “Arabic” numerals from India, as well as the concept of zero, “which comes in handy when you want to write billions and billions.” Neil manages not to wink, at least. Among other discoveries, Alhazen discarded the idea that the eye sends beams of light with which it perceives the world — rather, he argued that light comes into the eye. He also determined that light moves in a straight line, and that the key to clear images is a small aperture to admit light — the secret to both the camera obscura and the eye’s pupil. In this telling, Alhazen (voiced by Alfred Molina) was also the first to lay out the basics of the scientific method, setting out a system of testing and sifting out errors, basing conclusions only on “argument and experiment,” and not in received wisdom.

Jump ahead a few more centuries, to Isaac Newton experimenting with prisms and almost — but not quite — discovering what happens if you focus a spectrum from a prism onto a magnifying lens. Tough luck, there. We see last week’s animated hero, William Herschel (sans guest voice actor Patrick Stewart) accidentally discovering infrared light in an experiment to see if the colors in the spectrum have different temperatures — the thermometer he used as a control showed an increase in temperature even though it was not placed in visible light.

And on we travel, to 18th-century Bavaria, and the hellish life of young Joseph Fraunhofer, toiling in the glassworks of Philipp Weichelsberger, where Joseph was both overworked and cheaply animated. Luckily, Weichelsberger’s workshop collapsed one day and Fraunhofer was literally rescued by Prince Maximillian, who took an interest in the boy and gave him the chance to study optics. Fraunhofer went on to make precision optics for the Bavarian military, and while experimenting with shining the refracted sunlight from a prism into a telescope, discovered the existence of dark lines within the spectrum, which turn out to correspond to the gaseous elements within the sun.


I’ll confess that Cosmos lost me a bit here — there’s a lot of pretty atomic-level animation of the electron in a hydrogen atom jumping around on a quantum level, and a kind of an explanation of how this is seen by spectroscopy, but I won’t pretend to have any deeper understanding of it than “you can tell what something’s made of by looking at its spectrum,” — which is about all a liberal arts monkey needs to know anyway. The how of it would require actual study — and for a pretty neat look at internet nerds trying to educate each other further, it’s a hoot to read the episode discussions on Reddit — but the why it matters is clear enough: look at a star’s spectrum, and you can tell what elements that star is made of. And it turns out that everything in the universe is made of the same elements — cue a reprise of the “we are made of star stuff” theme, complete with a visual quotation of the first series, the emblematic dandelion fluff blowing into the wind.

The episode closes with a brief mention of the mystery of dark matter — the stuff that seems to make up a big part of the universe, but whose properties are largely unknown — so far. “We only know it’s there because of its gravity,” which is driving the expansion of our universe. And then on to a rather sweet closing bit in which various kinds of light are represented by various visual effects superimposed on shots of New York City, accompanied by bits of Gershwin’s “Rhapsody in Blue,” eventually coming together in a fully-orchestrated picture. Pity, though, that thanks to a really good ad campaign, all I can think of when I hear that tune is United Airlines.

Cosmos: A Spacetime Odyssey airs on Fox 9:00 Sundays Eastern/Pacific, 8:00 Central/Mountain. Reruns Monday on National Geographic Channel 10:00 Eastern. Episode 5, “Hiding In The Light,” online at

TV Show: Cosmos

You may also like...