Episode 5 seems to want to convey that Luke was on Dagobah for a while, and mastery of the Force is a slow, incremental process requiring training, even though it’s hard to understand how Luke could have been on Dagobah for long given the overall plot logistics.
Well, if you’re willing to inject some hard sci-fi into your space fantasy, without a hyperdrive, the Falcon would’ve had to travel from Hoth to Bespin in real space at near-light velocity, which would’ve subjected the crew to relativistic time dilation. So everyone aboard the Falcon may’ve only experienced an hours’-long trip while six months elapsed for the rest of the galaxy.
After having watched the Empire Strikes Back probably over 100 times, I just now noticed that the movie does in fact provide at least a minimum required training time duration of 1.5 days for Luke’s training with Yoda.
The first actual training session with Yoda is the scene where Luke is running around with Yoda on his back. Midway through this scene, before Luke enters the vision cave, Yoda says the following: “Nothing more will I teach you today. Clear your mind of questions.”
So Yoda says he won’t teach Luke anything further today. The next time we see Luke training with Yoda is the scene where he’s doing a headstand and lifting a rock. So the earliest this must be happening is the following day, but it could also be any number of days later.
So this sets a minimum time requirement of 1.5 days. Since it is night time on Dagobah when Luke leaves for Cloud City, the absolute shortest time the training could be is 1.5 days, if we assume every single training scene after the first happened on the same day that Luke leaves for Cloud City.
But the fact that, during the first training scene (Luke running around with Yoda on his back), Yoda ends the training by saying essentially “we’ll resume tomorrow”, suggests to me that we’re supposed to see the different training scenes as happening over a longer time period, with Luke living and sleeping on Dagobah each night.
But the longer we try and stretch out the total training time, the more creative we need to be to explain how Han and Leia were either waiting around inside that giant worm doing nothing for like a year, or else invoke General Relativity for the Hoth to Bespin trip.
We all know Irvin Kershner did not have Einstein in mind when working on this movie. But if we explore this just for fun, we still run into difficulty. We also have to account for the perspectives of Boba Fett and Darth Vader. Boba Fett seems to just follow Solo from the asteroid field to Bespin, meaning Boba Fett is also traveling at relativistic speeds in the same reference frame as Han Solo. Or maybe Fett calculated Solo’s most likely destination and jumped ahead via hyperspace. Either way, assuming Bespin is one star system away from Hoth (a weird coincidence that Han’s friend Lando lives next door to the remote Rebel base), the distance would be around 4 light years. This means that for anyone not traveling in the same reference frame as Han Solo, at least 4 years would have passed from the time Han left the asteroid field to the time he arrived at Cloud City. So… did Boba Fett call up Darth Vader and say “Okay I found the Millennium Falcon, and I know where it’s headed based on its current trajectory. Meet me in Cloud City in 4 years.” I guess Vader spent those 4 years thinking about the perfect way to surprise them, settling on an elaborate dinner party and a cool one-liner.