Physics of lightsabers in stories.

[Vyk]

This is fantasy and doesn't have to keep technology to strict physics, so if a book approved by Lucas says the blade is weightless, but behaves with inertia and momentum, then that's what I'd follow, even if the special effects and actors struggle to properly simulate the appearance of weightless movement with momentum disproportionate to the actual mass of their props.

There's a big difference between "a book approved by Lucas" and "a book approved by Lucasfilm".  I'm not aware of any book other than the movie novelizations that had any input from Lucas himself; if you find otherwise, I'd be interested to know that.

In any event, whether the blade has weight or not is all but irrelevant; I suspect that it would be impossible to tell the difference in handling between a blade with gravitational mass and one without so long as their inertial mass was identical.  What matters is if it has inertia, which it clearly does.  (I also strongly suspect that a gyroscopic effect would be visible in a lightsaber's behavior when thrown, but it's been a long time since I studied rotational dynamics and wouldn't trust my calculations even if I were daring enough to try them.  In other words, I think it would be possible to prove the lack of gyroscopic effect, but not possible for me to prove it. )

I was hoping to find out if the books or otherwise stated clearly a reason for lock up. I'd even be satisfied if a skilled swordsman could explain why it would be problematic to attempt sliding blades.

I've never seen it stated what the actual physical effects are that cause lockup.  I'd be really reluctant to trust anything written about the technical details anyway.  Lightsabers defy modern physics; if they didn't, somebody would have made one by now!  That means that we can't explain how they function, merely describe how they behave.

"It's simply not done in the movie" could be changed at any time by another movie or book. A new director working with a choreographer who shows him/her something the director likes could blast all our inferences out the window with a different combat style. Did Luke do spins like prequel Obi? Did Vader do what Anakin did? How much of what we see is just Kendo, special effects, neat choreography or just our inferred guess?

For the record, the PT lightsaber style changes were deliberate based on the idea of showing lightsaber fighting at its peak, with the OT fighting all being limited in some fashion (age, injuries, or lack of experience).  I've heard mixed stories about the ANH fighting, whether it was a limitation of how far they had evolved the idea of saber fighting, whether it was a limitation of Obi-wan as an aging character, or whether it was a limitation of Sir Alec Guinness as an aging actor; my guess would be it's mostly the first and third, and the second is basically a retcon, but that's just my opinion really.  I can't say there won't be fight-choreography changes in upcoming movies, but thus far, with TFA, there seems to be a deliberate decision to stay with a degenerated lightsaber style--the most degenerated yet, actually.  I predict that, probably in Ep 9, we'll see one last PT-level-of-skill fight-to-end-all-fights, but only time will tell.

So, yes, we could have a director just decide they want to do things differently, whether it makes sense or not... but I don't think we will.

I'm attempting to be cautious about fiction.

What counts as cautious?  The most cautious would be to draw no conclusions at all and go only off of what's clearly visible or explicitly explained on screen.  At that point, you basically can't draw any conclusions about lightsaber physics at all, since almost every behavior we can see can be hand-waved away by "well, so-and-so was using the Force to affect it".

Yes, I'm that pathetic.

I don't find that pathetic at all.  On the other hand, I find it perfectly reasonable to watch entire lightsaber duels in slow-motion, so perhaps my support is not particularly helpful here! 

In reference to your specific question on blade lock up:  sliding your blade down your opponent's blade towards their hand, wrist or even forearm is a valid technique.

I'd argue that it is not a valid technique, for two reasons.  First, we never see it done, even when it would make sense to do so; Obi-wan visibly disengages before cutting Grievous's wrist, even though just sliding the blade would have been easier.  Second, if somebody sliding their blade down were a realistic technique, and if materials existed that cannot be cut by lightsabers, lightsabers would have hand guards.  They do not have hand guards, yet we know materials exist that cannot be cut by lightsabers, so sliding the blade is not a realistic technique.  (There is also the possibility that nobody has ever considered the possibility of putting a guard on a lightsaber despite there being an obvious need for it.  That seems highly unlikely to me; it would require that, over the history of the lightsaber, not one Jedi has ever encountered a bladed weapon with a hand guard and thought, "hey, wait a sec...!" nor seen somebody be injured that way and thought, "I know how we could stop that....")

[GregG124]

Saber canon has always been a bit blurry (especially from the filmmaking end) some say the blade is SUPER heavy, others say the blade is 100% weightless.

[ithekro]

The blade is supposedly weightless, but the energy output is suppose to make it wield like a huge sword.  Mark Hamel repeatedly tells about how he was told to act like it was a heavy Excalibur type sword where you needed both hands one it.  Later on as they got better, as Lucas put it, the young Jedi could take a hand off it from time to time.   And back in the day, when you had fully trained Jedi in their prime, they could do whatever with their lightsabers, because they were that good.

[Obese Wan Kenobese]

We're getting back to assuming a hilt repulsion or 'sticky' blade to prevent sliding toward the hand. But, again, if there is a strategical combat reason, I would be satisfied with no need for the saber design/physics assumptions. My true assumption is that real swords have hilt guards, so real combat doesn't try to slide to the hand, so choreographers didn't put that in the film. The rest is fun for imagination, but my brother in law wants to try to cut my fingers off, so I need to tell him why he can't do that, cuz it's the safe zone, or that's all we're ever gonna do when in combat, and it's boring.

Kanan has something like a hilt guard, but that's Disney who also have saber-copters and saber-blasters that shoot what looks like electric cotton balls.

[Vyk]

We're getting back to assuming a hilt repulsion or 'sticky' blade to prevent sliding toward the hand. But, again, if there is a strategical combat reason, I would be satisfied with no need for the saber design/physics assumptions. My true assumption is that real swords have hilt guards, so real combat doesn't try to slide to the hand, so choreographers didn't put that in the film.

I'm curious to know why they didn't just put some sort of guard on there in the first place; kendo shinai have them, after all.  In ANH, Obi-wan's saber has a disc on the emitter that is sort of like a shinai's tsuba (although it isn't very large), but there's nothing of the sort on the other two sabers.

The rest is fun for imagination, but my brother in law wants to try to cut my fingers off, so I need to tell him why he can't do that, cuz it's the safe zone, or that's all we're ever gonna do when in combat, and it's boring.

Because if he does it you're going to kick him. 

[ithekro]

Well the original lightsabers were just flash attachments from press cameras.  That and the concept was that the little cylinder on the stormtroopers back was going to be their lightsabers.  Back when everyone had them, rather than them being the thing the powerful magic users carried only.

The concepts progressed from there, but the props didn't as much, staying close to what they had for Obi-wan, Luke, and Vader in ANH.

[Obese Wan Kenobese]

I read that Vader's saber was missing in ESB filming, so they had to get another one, which went missing when they filmed ROTJ, so they used Luke's ESB saber to convert into Vader's ROTJ saber, and they used Obi Wan's ANH saber to make Luke's ROTJ saber.

The hilts themselves are thicker than the blade, so maybe it's considered enough. We can either assume 'sticky' blades, hilt repulse, saber emitters are enough of a guard or it's just not a strategy employed by the inexperienced Luke and Vader who toyed with him, nor by any of the prequel Jedi we saw. Of all the possible moves, we haven't seen them all.

ANH brought us our first lightsaber fight. Both Vader and Obi used two hands. ESB brought us flips, more saber stuff, Vader using one hand, stopping blasters bolts with the Force and moving things with the Force. ROTJ brought us a green lightsaber, the temptations of the Dark Side and Force lightning. Phantom Menace brought us speed runs, more flips, one handed saber spins, dual sided lightsabers and more understanding of how the Jedi did things as a group. Attack of the Clones brought us curved hilt lightsabers, catching Force lightning, Force jumping to an extreme and dual lightsaber wielding. Revenge of the Sith brought us throwing Force lightning back and lots of moving heavy things with the Force jumping, as well as essential understanding of the advantages of having the high ground. TFA brought us cross guards/ancient saber vents, mind reading and catching blaster bolts in mid air and holding them indefinitely. Perhaps the next installment will bring us sliding blades or an explanation of why it can't be done. If it can be done, Kylo's 'guards' won't guard much, as he has 3 emitters that could be cut the same as single emitters. I think it's for use just as we saw in the film, and as vents stated in other Disney Star Wars guides. If Rey builds her own next, Disney can make their own rules in detail.

[Vyk]

ANH brought us our first lightsaber fight. Both Vader and Obi used two hands. ESB brought us flips, more saber stuff, Vader using one hand, stopping blasters bolts with the Force and moving things with the Force.

If I remember correctly, ESB was the first with an actual sword expert in the suit.  In ANH, David Prowse did all the sword work, while in ESB, it was Prowse some of the time but a sword expert at other times.  (I can't remember the expert's name, and it's almost 4AM and I'm not going to go looking right now. )  Anyway, just some real-world explanation for Vader's style change (aside from the combat being more fluid and mobile in general).

[Darth Tepes]

If I remember correctly, ESB was the first with an actual sword expert in the suit.  In ANH, David Prowse did all the sword work, while in ESB, it was Prowse some of the time but a sword expert at other times.  (I can't remember the expert's name, and it's almost 4AM and I'm not going to go looking right now. )  Anyway, just some real-world explanation for Vader's style change (aside from the combat being more fluid and mobile in general).

The Late great Bob Anderson is the expert you are speaking of..... Choreographer for The Princess Bride, Highlander, Lord of the Rings..the list goes on.  Wonder how it would have been if Toshiro Mifune had been cast like Lucas wanted.

[Vyk]

The Late great Bob Anderson is the expert you are speaking of..... Choreographer for The Princess Bride, Highlander, Lord of the Rings..the list goes on.  Wonder how it would have been if Toshiro Mifune had been cast like Lucas wanted.

Thank you!  I had meant to go look him up, and forgot.

I was unaware that Lucas wanted Toshiro Mifune.  I can't say I'm particularly surprised, given Lucas's love of Kurosawa films, but it's news to me.

[Darth Tepes]

Thank you!  I had meant to go look him up, and forgot.

I was unaware that Lucas wanted Toshiro Mifune.  I can't say I'm particularly surprised, given Lucas's love of Kurosawa films, but it's news to me.

Yea, Lucas wanted him for Vader or Obi-Wan..whichever he would have taken (if he had accepted).

[Vyk]

Yea, Lucas wanted him for Vader or Obi-Wan..whichever he would have taken (if he had accepted).

Wow, Toshiro Mifune as Obi-wan.  That would've been pretty wild!

[BurceChuat]

Yea, Lucas wanted him for Vader or Obi-Wan..whichever he would have taken (if he had accepted).

Wow, Toshiro Mifune as Obi-wan.  That would've been pretty wild!

Shame he didn't accept...the Kenobis/Skywalkers could've been Asian!

[Obese Wan Kenobese]

Darth Maul: Shadow Hunter states the phrase "frictionless edge of a lightsaber."

In Book of Sith, Quinlan Vos states that lightsabers should have hand guards.

[Obese Wan Kenobese]

Rebels Spoilers!!

So, now we know the saber is heavy for the inexperienced who have not connected with the saber/crystal. I'll presume this covers Luke's using the saber as a heavy weapon. I would've preferred it be more the combat style thing. Two hands vs. one hand technique can still play a part.

The blades are now indeed 'sticky' as they are 'drawn to one another'. I still don't know for sure if the blades would slide as the plastic does. Disney Canon is whatever they decide to explain things as they use fan ideas. The appearance of the blades sticking in the OT acting didn't fit the 'frictionless blade' in a book that is no longer canon. The attraction is stated explicitly in the new canon. I'll assume the lightning of the Visla dark saber is indicative of the magnet like connection between the blades. So, perhaps sliding becomes difficult or slow, which is why we don't see them taking advantage of the lack of hand guards.