“You’ve never heard of the Millennium Falcon?…  It’s the ship that made the Kessel Run in less than twelve parsecs.” – Han Solo

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From the way it’s used in Star Wars: Episode IV- A New Hope, a parsec sounds like a really cool unit of time.  In reality, a parsec isn’t a measure of time- it’s a measure of distance.

Parsec” is an abbreviation of “parallax of one arcsecond.”  An arcsecond is a unit of angular measurement (one arcsecond is 1/3600 of a degree), and parallax refers to the effect where the position of an object appears to change when viewed at different points.  For example, when looking at an analog clock directly from the front, you may see the time at 2:38.  When viewed from the far right, the minute hand appears to shift, making the time appear to be 2:40.

Historically, a parsec was defined as the distance at which two objects, separated by one astronomical unit, appear to be separated by an angle of one arcsecond.  (An astronomical unit is the average distance from Earth to the Sun- about 150 million kilometers or 93 million miles.)

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A parsec is equal to about 3.26 light-years, or 31 quadrillion kilometers, or 19 trillion miles.  This isn’t a particularly useful unit of measurement for life on earth.  (“How far is Detroit from here?”  “Oh, about 0.00000000000469398 parsecs.”)  Even within our Solar System the parsec would be overwhelming- on average, Pluto is 0.000191 parsecs from the sun.  But considering just how vast the Universe is, parsecs are convenient for those large distances measured in astrophysics and astronomy.

It seems a little silly, then, that Han would claim that the Millennium Falcon can make the Kessel Run in 12 parsecs.  It would be similar to a runner saying they ran a 5K in 5 kilometers.  Physicists have been bothered by this apparent misuse of units for decades.  Neil deGrasse Tyson is particularly annoyed with the statement.

So why does Han made this claim?  There are three possibilities.

  1. The screenwriters made an error and were just trying to sound cool.
  2. Han is just plain full of it and was trying to convince Luke and Obi-Wan to hire him.
  3. It actually is an impressive accomplishment.

In the Expanded Universe, the Kessel Run is a smuggling route that typical measures 18 parsecs through the Maw, a cluster of black holes.  Black holes have incredibly strong gravitational effects- if you get too close, you would never be able to escape.  Instead of taking the safer 18 parsec route, Han and Chewie decided to skirt closer to the edges of the black holes, cutting the distance down.  The claim, then, is less about how fast the Millennium Falcon is, and more about how great the navigation system is and how skilled Han is as a pilot.

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After all, Han was able to navigate an asteroid field, even though the odds of success were three-thousand seven-hundred twenty to one.

Keep calm and science on.

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