Welcome to the Science Asylum.
I am Nick Lucid.
So I was watching Star Wars recently and noticed Han Solo said this:
“It’s the ship that made the Kessel Run in less than 12 parsecs.”
Actually, a “parsec” is a unit of distance, so that claim makes no physical sense.
Hmmm, we’re going to try to make some sense of it anyway.
For those you who don’t know, the Kessel Run is an 18 parsec strip of space in the
Star Wars galaxy that smugglers like Han Solo use to transport spice.
It’s kinda tough to get through because it’s monitored by imperial forces.
Not that imperial forces are known for being good shots or even all that smart.
Anyway, let’s start with a little dose of reality about writing stories.
In the revised 4th draft of the script of Star Wars: A New Hope
Immediately following that line from Han, it says:
“Ben reacts to Solo's stupid attempt to impress them with obvious misinformation.”
which seems to suggest Han was purposefully giving them a load of crap.
However!
In the official audio commentary, George Lucas claims:
Han used units of parsecs because the Millennium Falcon’s navigation system is so sophisticated,
that it can calculate a straighter path through hyperspace.
Which seems to suggest Han was telling the truth.
Back Peddle, Back Peddle, Back Peddle
See, totally inconsistent.
Yes, it's inconsistent
but we like to think of books and movies as though they contain completely self-consistent
worlds that actually exist.
So what would it take to actually shorten 18 parsecs to 12?
First, if we’re going to use a unit like “parsec” then we better know what it means.
It’s actually short for “Parallax of an arc-second”.
To make some sense of it, we’re going to have to zoom out.
No no, like way out.
Ugh just keep going until I tell you to stop.
Keep going, Keep going.
OK, stop!
Out here, you can see the entire orbit of the Earth.
If we look at this near-by star, it looks like it’s by these distance stars.
6 months later though, it looks like it’s over here.
It’s kind of like when you’re driving down the road and the far away things look
like they’re moving a lot slower than the closer things.
That difference is called “parallax,” which is the same thing your two eyes use
to give you depth perception.
Camera one, Camera two, Camera one, Camera two.
An “arc-second” is an angle measurement.
1/3600th of a degree to be precise Just like how a second is 1/3600th of an hour.
So, like, a super small angle!
Divisions like this are left over from Ancient Babylon, where they…
HEY!!!
If the Earth’s parallax of a near-by star forms an angle of one arc-second,
then the star is said to be one parsec away from Earth,
which is about three and a quarter light years or 19 trillion miles .
He couldn’t have used the unit anyway because Earth doesn’t exist in the
Star Wars galaxy.
Maybe not, but human’s evolved on Earth partly because the Sun is just the right size and
Earth is at just the right distance away.
Any fictional planet that evolves humans would have a comparably-sized orbit.
Boom!
So the question remains: How do we turn 18 parsecs into 12?
The ships in Star Wars jump into something called “hyperspace.”
Actually, hyperspace is completely fictional.
It doesn’t matter if it’s fictional.
Just go with me here.
We can assume the fictional physics of hyperspace doesn’t shortened distances because, if
that were true, Han wouldn’t be boasting about distance.
It doesn’t make any sense.
We can also assume hyperspace isn’t just slang for “almost light speed” because,
at nearly light speed, even 12 parsecs would take about 40 years.
The delivery dates would be totally impractical.
We also know everything with mass travels slower than the speed of light,
which leaves us with only one option for hyperspace: It’s a portion of space where the speed
of light is faster than usual so, inside hyperspace, you can travel much faster than usual.
And the navigation computer just has a map of where it all is and which parts are safe.
Since the speed of light is faster, you’re still not moving at a significant fraction
of it, so special relativity doesn’t apply, but
general relativity still can!
As we’ve seen before, gravity affects objects by changing what straight lines look like.
Changing the shape of space is also going to change its size, but a small star like
the Sun isn’t going to cut it.
We’re going to need a bigger mass.
Star Wars fans have suggested Han used a set of black holes called the Maw Cluster.
Actually, that’s not Star Wars canon.
That’s Expanded Universe, which makes it Star Wars Legends.
Didn’t you get that memo?
Fine!
18 parsecs is a pretty big region of space.
We can assume somewhere there’s at least one black hole.
Completely empty space is described by this equation.
The space around a black hole is described by this equation.
The identical stuff shows how space is unaffected by the black hole, so we’ll ignore those.
We’re also only interested in space, not time, so we’ll ignore this too.
And we can see now, the black hole only affects space along radial lines.
If we take a ruler and…
Wait a second!
The distances are bigger when you’re closer to the black hole!
Getting close to black holes makes the Kessel Run longer, not shorter.
Ha! I win!
So, have you ever thought this deeply about a fictional world?
If so, which one?!
Let us know in the comments.
And until next time, remember, it’s OK to be a little crazy.