Imagine that Boba Fett is attempting to kill Luke Skywalker. Luke is standing out in the open, and Fett is flying overhead in his spaceship, Slave I. Fett has outfitted his ship with a laser cannon as thick as a man’s thigh, and fires it at Luke. Luke, rather than dodging, brings up his lightsaber to block the bolt.
The lightsaber’s blade is thinner than the blaster bolt. Does the lightsaber deflect the entire bolt, or does some of the bolt leak around the edges, frying Luke where he stands? Assume that Luke summons up the Force to strengthen his arms, so that the bolt doesn’t simply knock the lightsaber out of his hands.
It seems pretty clear in the movie that blaster bolts are treated as though they were indivisible solid “bullets” — we only see blaster bolts bounce or “hit” (and disappear when they “hit”), never fragmenting or splitting, and if it were possible for that to happen we probably would’ve seen it — blaster bolts fly by the thousands in the movies constantly hitting glancing blows off of various objects. Most notably, the blaster bolt Luke fires at the “magnetically sealed” walls in Episode IV richochets several times without ever losing its cohesion until it finally scores a “hit” on a non-“magnetically sealed” wall and vanishes.
Therefore, blaster bolts can only do one of two things when they hit a surface — “hit” and discharge, vanishing with a flash of sparks and doing damage to the surface they hit, or bounce off. The Death Star somehow manages to cause several blaster bolts (in this case “superlaser streams”) to combine, but this is implied to be special technology.
So the real question is whether Boba Fett’s ship cannons’ projectiles are small enough so that they will *only* hit Luke’s lightsaber — in which case they will bounce off, just like anything else — or whether they’re so large that Luke will be incapable of presenting the lightsaber to them as a solid surface without the bolt also impacting enough of Luke’s body for the bolt to discharge, killing him. The bolt “leaking past” Luke’s lightsaber would demonstrate behavior never seen in the movies.
If we jump past movie analysis to the dodgy pseudoscience “technical manuals” of Star Wars, the technobabble backs up what we see in the movies — blaster bolts are “magnetically sealed cylinders” of plasma, which, for all intents and purposes, are single solid objects until the “magnetic force field” holding the plasma inside breaks down, at which point the plasma is all released at once in the eponymous “blast”. Without special technology, individual blaster “bolts” or “streams”, once created, cannot be divided or combined.
This basically means that, yes, lightsabers can be used to deflect even very large blaster projectiles — and we do in fact see Qui-Gon Jinn deflecting bolts from vehicle-mounted cannons in Episode I that are much larger than the bolts from handheld weapons seen in the original trilogy.
On the other hand, the “artillery”-style bolts that we see fired in the major space battles, which are more the size of a man’s chest than a man’s thigh, would be impossible to block with a lightsaber, which is why we never see anyone try. (It’s established that “artillery” attacks on Jedi can and do kill Jedi, such as in the novelization of Episode 3 where many Jedi are killed simply by long-range “shelling” of the area they’re standing in with artillery-piece-sized blasters. Similarly, in video games like Knights of the Old Republic, “auto-kill”-type traps for the player character consist of banks of “assault blasters” that presumably unleash enough firepower to automatically kill you regardless of your skill with a lightsaber.)
Wow, thank you for that extensive analysis… I didn’t remember Qui-Gon’s experiences with large cannons, probably because I was too busy hating Jar-Jar.
Now if I ever have to roleplay a Jedi, I know when to run and when to play blaster baseball 🙂
In a totally non-researched and this-is-what-I-personally-want-to-happen way:
I think he moves the lightsaber fast enough such that he can block the whole bolt by touching all of its leading edge as it approaches. This requires a diagonal force-guided swipe.