Summary
Highlights
A parsec is defined as the distance at which half of the parallax angle to a star is one arcsecond. This unit is equivalent to 3.26 light-years. Neil highlights the issue: no star is exactly one parsec away, making it a theoretically defined unit without a direct celestial counterpart at that specific distance.
He argues that 'light-year' is a far more intuitive and easily understandable unit of distance, despite occasional confusion about it being a unit of time. He expresses frustration that despite its complexity and lack of immediate practical distance, parsecs are still used by some astronomers.
Neil criticizes Star Wars for Han Solo's line about completing the Kessel Run in 'less than 12 parsecs,' which incorrectly uses parsecs as a measure of time or speed rather than distance. He likens this to saying one ran a marathon in '20 inches,' emphasizing the importance of correct units.
He expresses his exasperation with Star Wars' scientific inaccuracies but acknowledges that it's a fantasy. He contrasts this with Star Trek, which used parsecs correctly as a unit of distance. Neil concludes by reiterating his dislike for the unit and how it’s poorly defined.
Neil demonstrates parallax using a thumb and eye experiment, showing how the apparent shift of an object changes with distance. He explains how astronomers use Earth's orbit around the Sun to measure the parallax of stars over six months, determining their distances from us.
Neil deGrasse Tyson introduces the parsec, a unit of distance used in astrophysics that he finds embarrassing. He notes its appearance in Star Trek and Star Wars, indicating its real-world origin but also his disdain for it as an astrophysicist.
The discussion moves to the ancient Babylonian system of 360 degrees in a circle, with each degree divided into 60 minutes and each minute into 60 seconds (arcminutes and arcseconds). This historical context is crucial for understanding the definition of a parsec.