Cosmos: "When Knowledge Conquered Fear"

Original Air Date:  March 23, 2014

The episode begins with Dumbledore dropping Harry Potter off at Neil deGrasse Tyson's house in the middle of a desert.  Wait, no... that's not right.

Neil tells the story of how ancient cultures were able to use pattern recognition to read the night sky to determine their location and the time of year.  To be able to predict migrations, seasons, plant ripening, etc.  And when a comet breaks that cycle by affecting the night sky, these early civilizations would read these celestial bodies as signs of an impeding disaster.  In fact, the word "disaster" comes from a Greek word meaning "bad star".

However, our knowledge of what a comet is, and where is comes from, conquered the fear associated with these alien flaming balls of doom.  The show introduces us to the Oort Cloud, an area of the solar system where asteroids reside.  These asteroids, covered in ice, are pulled into an elliptical orbit and become comets.   The cloud, Tyson explains was named for Dutch astronomer Jan Oort, who first proposed the notion of the cloud.  Oort is quite the astronomical superhero -- not only did he deduce the existence of this cloud, he also was the first to accurately measure our sun's distance of the center of our galaxy, as well as be the first astronomer to use a radio telescope map the Milky Way.

We follow a comet from the Oort cloud through the outer solar system to Mars, where heat from the sun begins to melt the ice in a comet and create its tail.  The comet is scene on Earth, in 1664.  A plague and the Great Fire of London soon followed -- assuredly these were predicted by the comet!  Edmund Halley, then a child, was fascinated by this comet and other heavenly bodies.  Haley was the first person to completely map the night sky of the southern hemisphere -- an important map to merchants and explorers as it helped them navigate.

Next we move on to scientific bad-ass and all around grumpy gus Robert Hooke.  I have to admit that by this point in the episode, I started getting a little concerned that we were going off on a tangent.  Hooke created Hooke's law of elasticity, invented the compound microscope, and was a serious drug addict.  Where are we going with this, Neil?

At a random coffee house, Hooke and Halley would chat with other greats of their time, like Christopher Wren.  The three of them got stuck on a specific problem -- why did planets move the way they did through the night sky?  Wren and Hooke could not do the calculations, but apparently there was someone who could -- Isaac Newton.  Halley went looking for Newton, who was in hiding after getting in a public dispute with Hooke over his work on the light spectrum.  Newton apparently had already calculated the mathematical formula for describing the force of gravity, along with describing universal laws of motion.  Halley encouraged Newton to write three volumes on the laws of motion and gravity, which were then edited and published by Halley.  One of Newton's ideas was that it was possible for a projectile to be launch with enough force to leave the gravity of Earth.  Newton also explained comets -- not only what they were, but why they moved the way they did.

One of the most interesting things I learned this episode was all of the things Edmund Halley had accomplished:  He was the first to map the magnetic field of the Earth, perfected the diving bell, invented the weather map, measured the distance from the Earth to the Sun, and discovered that all stars are in motion.  And, of course, he also studied the eyewitness accounts of all comet over a three hundred year period, eventually discovering the occurrence of a particular comet -- one that reappears every 76 years.

While the beginning of this episode made it sound like it was about comets, in reality it was about the discovery of the laws of gravity -- an essential event in or scientific maturation as a civilization.  The episode seems to meander a little as it took some time to talk about Robert Hooke, but got back on track as is focused on Halley and Newton.