Lightsaber blade "weight" in-universe

Question

In-universe, a lightsaber is basically a controlled, fixed-length plasma stream that can be used as a sword. As such, the blade wouldn't have any mass (or infinitesimal mass if you want to get technical about E=mc²).

Anyone familiar with fencing or swordplay knows that the weight of the handle and blade, and thus the overall balance of the weapon, is critically important while fighting. A sword that is too blade-heavy is unwieldy; it is difficult to start, stop, and change the path of the blade as it's swung, which is vital to outmaneuvering your opponent in a duel. Conversely, a sword with too light a blade (equivalently, too heavy a hilt) is too easy to swing around. it's hard to "feel" where the blade is, and thus to make the minute changes needed to block a blow or land one. It can also be just as exhausting, in a different way, to wield such a sword; because most of the mass is behind your hand, it takes muscle power to point the blade forward instead of upward, while a balanced weapon would point directly forward from the user's hands. You also get no mechanical advantage while swinging it.

Obviously, out-of-universe the props were full "swords" that were then rotoscoped to paint the beam blade over the white wooden (later plastic) dowel that protruded from the saber. This gives the actual prop used by the actors a more realistic weight and balance, which can be seen in the duels (Darth Maul has to heave a bit to get that double-saber staff moving, and you can see the effort behind a full baseball swing of the sword by Luke or Vader in the original trilogy).

Was there any attempt in-universe to explain the weight and balance that an active lightsaber seemed to possess?

Answer 1

There have been a few attempts (mostly in EU novels) to discuss the properties of the blade, but most analysis instead explains why Jedi (and Sith) could use the blade effectively despite the objections you correctly raise.

Here are the things we know:

The weight of a lightsaber is comparatively light, and the mass is entirely in the handle. (We don't know the weight of the handles; they're thicker than a real sword hilt but hollow and filled with electronics. It's probably comparable to a heavy longsword hilt.)

The 'blade' is a magnetic 'bottle' containing the plasma generated by the lightsaber. It generates a strong electromagnetic field. This means that the blade will have a little resistance to motion when in the presence of ferrous metals (most of the time, in SW). The blade will, therefore, 'bounce' off some metallic substances, even as it melts them. (The duel in ESB has some good examples.) The dense magnetic bottles are certainly the reason the blades 'bind' on each other rather than passing through each other.

(Note that when Jedi burn through bulkheads and doors, they always insert the lightsaber at right-angles, point first. Clearly this is to avoid lateral resistance from the magnetic field.)

Apart from these magnetic effects, the blade is effectively weightless.

The basic handling, therefore, would be extremely hilt-heavy. The natural balance point is probably all the way back inside the user's grip.

As you correctly point out, this would make the blade extremely hard to 'feel'. This goes a long way to explain why only Jedi wield lightsabers. (This also explains the usefulness of the training remotes; they cure the tendency to overcorrect the blade. The first lesson Jedi are taught is to discard their physical senses and feel the blade position with the Force. Clearly this is not just a teaching style but a practical necessity.)

Jedi must develop extremely strong wrists. This is not a problem; like medieval knights, Jedi begin training at a very early age, including lightsaber training from day one. Clearly this is, in part, to build wrist and arm muscle. Note that Luke - who does not have this training - consistently uses his lightsaber two-handed at first. He doesn't (and clearly can't) use it one-handed until he's gained much more experience and practice.

The heavy two-handed styles in common use in the original trilogy are clearly, therefore, a matter of control. As with real longswords, the extra hand on the hilt provides control and direction, not power. (Lucas directed the actors in the original trilogy to behave as if the blades were extremely heavy... hence the kendo-like styles. This makes sense; an old man and a wounded cyborg would no longer have their youthful wrist strength and control, and would have to be cautious.)

These drawbacks conceal advantages in disguise. Sure, they're a problem in a swordfight. But Jedi aren't primarily duellists, they're police. Their 'typical opponent' is a room full of people with blasters. The blade-light overcorrection that harms 'feel' in the bind also gives you rapid tip movement to stop a flying blaster bolt - if you have a Force sense telling you where the tip should go.

(Note that Sith, who typically do expect other swordsmen as enemies, frequently seem to wipe the floor with Jedi in a straight swordfight. Compare Dooku's tight, defensive style - and note the curved hilt of his lightsaber, letting him keep the blade forward without pronation of the wrist. Likewise, Maul's staff-style avoids the whole 'feel' problem, at the cost of reach - and an intense danger of cutting off his own leg.)

This is why non-force users don't wield lightsabers - without the precise Force sense of blade location and combat movement, they're likely to overcorrect and hurt themselves. And without the intense training, they wouldn't have the strength and stamina to control it. (This is canon; note that in the EU, Talon Karrde considers the lightsaber at Luke's belt to be proof of his identity by itself. "You were either Luke Skywalker, Jedi, or else someone with a taste for antiques and an insufferably high opinion of his swordsmanship." Clearly, without Force training it's not possible to develop sufficient control to use the saber effectively.)

Answer 2

The very issues you mention are part of why they were traditionally the weapons of Jedi alone. Other variations existed, in forms closer to pikes and naginata, but using one as a sword gave the user tremendous flexibility. The trade-off is that it requires tremendous skill to use a lightsaber. Partially due to the weightlessness of the blade, but also due to the inherent gyroscopic tendency of the looping plasma. Much like the physics demonstration where a user pushes on a spinning wheel and it moves at an angle where the user attempts to push it to, so too does a lightsaber not move in the way you would intuitively assume.

From Wookieepedia:

Due to the weightlessness of plasma and the strong gyroscopic effect generated by it, lightsabers required a great deal of strength and dexterity to wield, and it was extremely difficult—and dangerous—for the untrained to attempt using. However, in the hands of an expert of the Force, the lightsaber was a weapon to be greatly respected and feared. To wield a lightsaber was to demonstrate incredible skill and confidence, as well as masterful dexterity and attunement to the Force.

In general though, the physics you see that appear to be from the blade possessing weight are actually from the gyroscopic effect the looping plasma causes. In real life, looping plasma wouldn't do that (at least not on that noticeable of a scale), but this is Star Wars. :)

Answer 3

The blade of the lightsaber is controlled by a...gyroscopic...effect. This term is probably not a perfect explanation, but it is the closest thing to our own science that fits. The hilt emits a beam of plasma with such infinitesimal mass that it should be weightless, and it would on its own. However the blade is contained as an elliptical continuation, or perhaps a parabolic arc that exits and returns to the hilt. This is made possible by an electromagnetic containment field (aka forcefield) which forces it to continue its cycle as it is emitted, then bent at the tip of the field, and then returned to the hilt. The gyroscopic effect comes into play because of the fact that the rate at which it is exiting and returning to the hilt causes a very powerful pull which simulates the feeling of "weight" in the blade. However instead of just pulling the entire hilt away from you, the pull is held in place by the containment field, sort of like how a wheel's edges want to continue turning even if the center stops moving. Thus with this simulated weight it acts basically the same as a perfectly balanced sword.

Of course this is all conjecture based on canon literature which has now sadly been de-legitimized by the release of the newest movie. It is however still very fun to think about, and provides the most plausible explanation for the implausible weapon.