Why don't lightsabres make people explode?

[Metrion Cascade]

Question. If lightsabres are so damned hot on contact (and people are full of liquid), why don't people explode into vapor when stabbed with them? You saw what Qui-Gon's weapon did to the Trade Fed blast door in TPM. Unless the door was made of candle wax or solder and lightsabres are weaker than we think, or lightsabres have some "power up/down" control I've not heard of, shouldn't people be exploding when stabbed?

[YT300000]

Lightsabres aren't hot themselves. They strip atoms from the target (which does cause quite a bit of heat [lots of friction]), but nowhere near enough to make someone explode.

[Spanky The Dolphin]

Specifically, lightsabres strip electrons from a material's atoms, so they basically cut by severing atomic bonds. This friction causes atomic vibration, which of course produces heat.

Lightsabre blades produce no heat, but when cutting through matter, the material heats itself.

I should add that I have absolutely no idea why you would think that lightsabres should make people explode on contact, anyway.

[Darth Wong]

Specifically, lightsabres strip electrons from a material's atoms, so they basically cut by severing atomic bonds. This friction causes atomic vibration, which of course produces heat.

Lightsabre blades produce no heat, but when cutting through matter, the material heats itself.

*ahem* you cannot strip electrons from an atom without supplying the necessary energy to make up the difference in electrical potential energy states. That pesky First Law of Thermodynamics again.

I should add that I have absolutely no idea why you would think that lightsabres should make people explode on contact, anyway.

She is suggesting that there should be explosive vapourization of internal body fluids upon contact with the lightsabre blade, given the prodigious heating ability demonstrated in TPM. Of course, we can see that people don't explode when hit by lightsabres, but that can probably be chalked up to a the poor thermal conductivity of the cauterized flesh around the wound (as opposed to the excellent thermal conductivity of molten metal).

[Spanky The Dolphin]

All I know is that the most likely accepted operation theory is that they strip electrons, and that the material heats itself.

[Vympel]

*ahem* you cannot strip electrons from an atom without supplying the necessary energy to make up the difference in electrical potential energy states. That pesky First Law of Thermodynamics again.

Spanky is using Bob Brown here- this wouldn't be one of the arguments that poisoned him against you, would it?

[Metrion Cascade]

Specifically, lightsabres strip electrons from a material's atoms, so they basically cut by severing atomic bonds. This friction causes atomic vibration, which of course produces heat.

Lightsabre blades produce no heat, but when cutting through matter, the material heats itself.

*ahem* you cannot strip electrons from an atom without supplying the necessary energy to make up the difference in electrical potential energy states. That pesky First Law of Thermodynamics again.

I should add that I have absolutely no idea why you would think that lightsabres should make people explode on contact, anyway.

She is suggesting that there should be explosive vapourization of internal body fluids upon contact with the lightsabre blade, given the prodigious heating ability demonstrated in TPM. Of course, we can see that people don't explode when hit by lightsabres, but that can probably be chalked up to a the poor thermal conductivity of the cauterized flesh around the wound (as opposed to the excellent thermal conductivity of molten metal).

Considering the amount of energy involved (someone gave a conservative estimate on what was required for the door in TPM, but I can't find it), I don't see why the difference in specific heat capacities between metals and water should really make much difference in the effect of the blade (other than perhaps slowing the distribution of heat down to some unobservable extent). I just figure the sabre has multiple power settings. Although one must also ask where the flesh from the initial hole goes.

And if lightsabres strip electrons from matter, what does that mean for breaking through forcefields? They do that, don't they?

[Darth Wong]

I'm talking about thermal conductivity of cauterized flesh, not specific heat. The idea is that the damage will be localized.

If lightsabres didn't pump a lot of heat into flesh, then you wouldn't be able to slice off an arm with a swipe and cauterize the stump. But at the same time, we know that a lightsabre can be stuck through a person's body and kept there momentarily with little effect other than the initial hole. Perhaps the forces associated with the lightsabre tend to repulse air molecules, thus reducing its convective heating effect (this wouldn't be an issue with metal which is much harder to push away than air).

[Connor MacLeod]

The door incident involved at least 100 MW sustained output, probably closer to 200-400 MW, low end.

[Metrion Cascade]

I'm talking about thermal conductivity of cauterized flesh, not specific heat. The idea is that the damage will be localized.

Shit. That's right. I tend to think in terms of "higher specific heat = better thermal conductivity." But that would be backwards, yes?

If lightsabres didn't pump a lot of heat into flesh, then you wouldn't be able to slice off an arm with a swipe and cauterize the stump. But at the same time, we know that a lightsabre can be stuck through a person's body and kept there momentarily with little effect other than the initial hole. Perhaps the forces associated with the lightsabre tend to repulse air molecules, thus reducing its convective heating effect (this wouldn't be an issue with metal which is much harder to push away than air).

Watching the movies, I always got the sense that the blade had a weak forcefield or something around it - one that was strong enough to separate the blade from air (explaining why users don't get hot), but not enough to withstand the pressure of contact with an object.

[Connor MacLeod]

I'm talking about thermal conductivity of cauterized flesh, not specific heat. The idea is that the damage will be localized.

If lightsabres didn't pump a lot of heat into flesh, then you wouldn't be able to slice off an arm with a swipe and cauterize the stump. But at the same time, we know that a lightsabre can be stuck through a person's body and kept there momentarily with little effect other than the initial hole. Perhaps the forces associated with the lightsabre tend to repulse air molecules, thus reducing its convective heating effect (this wouldn't be an issue with metal which is much harder to push away than air).

Selective permeability? (sort of like the gungan shields in TPM?) Makes sense. Official literature indicates the lightsaber only expends/loses energy when it is in contact with matter.

However, I'm now wondering why in some instancecs lightsabers appear to slice off limbs (Zam and Anakin's arms and Jango's head in AOTC, or Darth maul in TPM, Luke's hand in TESB), but don't in others (Luke on the skiff in ROTJ) For that matter, what about in ANH (When Obi-Wan slices the criminal's arm off? There's blood there as well as the severed limb.)

Could it have anythign to do with intensity (lightsabers both deliver their energy in a more sustained manner than blasters, and to a much smaller "surface area" - they make microscopic cuts acording to Dark Force Rising)? Thermal resistant properties of body armor/clothing (such materials/clothign does exist according to the Visual Dictionaries) How about hte fact that they seem to make quick cuts or slashes? The blade isn't in contact with enough flesh or with flesh long enough to transmit more energy than is needed for actually cutting?

Another interesting idea - what about Vader's arm? It was sheared through, but none of the wires or materials attached to the limb appeared to be molten.

[Connor MacLeod]

Well we know of official examples where lightsabers can be used undewater (splinter of the Mind's eye andt he Cloen Wars Micro-series) We also know of forcefields that selectively repel matter (TPM, gungan shields.) Since lightsabers do not appear ot vaporize large quantties of water surrounding the blade, this seems to make sense.

Could a lightsaber wielder be required to apply a certain amount of force in order to get whatever field is containing the "blade" to allow the target matter through?

[Darth Wong]

Shit. That's right. I tend to think in terms of "higher specific heat = better thermal conductivity." But that would be backwards, yes?

I would prefer to say that there's not a direct correlation either way. However, it's true that some of the highest thermal-conductivity materials don't have particularly high specific heat.

Watching the movies, I always got the sense that the blade had a weak forcefield or something around it - one that was strong enough to separate the blade from air (explaining why users don't get hot), but not enough to withstand the pressure of contact with an object.

Without getting into the nitty-gritty of what kind of forcefield this might actually be, it makes sense that there is some kind of forcefield, otherwise blades would not clash and lightsabre battles would be really short.

[Spanky The Dolphin]

I wonder if Metrion is aware that it is Canon that lightsabre blades do not generate heat, as stated in the ANH novelisation.

[Darth Wong]

I wonder if Metrion is aware that it is Canon that lightsabre blades do not generate heat, as stated in the ANH novelisation.

I wonder if you are aware that "heat" is not a substance or form of energy; it is a process. And lightsabres definitely do it, as shown in TPM. The mechanism through which they do it is irrelevant.

[Metrion Cascade]

I wonder if Metrion is aware that it is Canon that lightsabre blades do not generate heat, as stated in the ANH novelisation.

Which is contradicted by onscreen events. I'm not saying they generate heat all the time. But they do generate it on contact with solid materials.

[Connor MacLeod]

Could the mechanism be density/material dependent? It doesnt seem to interact with air (and IIRC Obi-Wan's lightsaber did not interact with the rainfall in AOTC... though I could be wrong about that.... and I dont think we saw it interacting with the dust storms we saw on Geonosis during the ground battle either....) In other words, it doesnt seem to interact with gasses or very diffuse forms of matter.. but it interacts pretty well with solids (and maybe some liquids?)

There may also be mass/velocity variables attached to this as well (liek there are with other known SW forcefield techs).. just more speculation

[Metrion Cascade]

Well we know of official examples where lightsabers can be used undewater (splinter of the Mind's eye andt he Cloen Wars Micro-series) We also know of forcefields that selectively repel matter (TPM, gungan shields.) Since lightsabers do not appear ot vaporize large quantties of water surrounding the blade, this seems to make sense.

Could a lightsaber wielder be required to apply a certain amount of force in order to get whatever field is containing the "blade" to allow the target matter through?

Right. If the forcefield can withstand, say, 16 psia of pressure (in order to avoid heating air in most human-friendly environments - Earth having 14.7 psia at sea level), all the user has to do is exert more than that pressure on it to break it down and expose the target to the blade. Underwater, that would require the forcefield to be stronger than atmospheric pressure and the pressure of the Gungan lake at the depths where we saw it used. Hell, maybe the lightsabre can detect where it is and increase the forcefield's power accordingly, assuming it's not done manually?

*EDIT - fixed misplaced decimal point in "14.7"*

[Metrion Cascade]

Could the mechanism be density/material dependent? It doesnt seem to interact with air (and IIRC Obi-Wan's lightsaber did not interact with the rainfall in AOTC... though I could be wrong about that.... and I dont think we saw it interacting with the dust storms we saw on Geonosis during the ground battle either....) In other words, it doesnt seem to interact with gasses or very diffuse forms of matter.. but it interacts pretty well with solids (and maybe some liquids?)

There may also be mass/velocity variables attached to this as well (liek there are with other known SW forcefield techs).. just more speculation

Dust particles would have to have a certain mass and be moving at a certain speed to exert greater pressure than the forcefield around the blade is capable of withstanding. Presumably most dust particles aren't massive enough or moving fast enough.

I'm not sure, but I seem to recall some hissing when Obi-Wan turned on his lightsabre. Like the rain was boiling on contact. I'll take another look at the DVD.

[Spanky The Dolphin]

I wonder if Metrion is aware that it is Canon that lightsabre blades do not generate heat, as stated in the ANH novelisation.

I wonder if you are aware that "heat" is not a substance or form of energy; it is a process. And lightsabres definitely do it, as shown in TPM. The mechanism through which they do it is irrelevant.

I understand that, but I get what you're saying now. Apologies.

[18-Till-I-Die]

Well if i might weigh in, heres how i always saw it:

The lightsaber consists of a very narow beam of 'blaster energy', constantly rebounding in a microthin 'circle' that is inperceptable to the human eye, and held within a forcefield that works one way: everything gets in, nothing can ever get out, other than some heat on contact with a soldi object, because the object bridges the gap between the shield, the beam, and the outside world. Its complicated, but i think it explains almost all the phenomena seen with lightsabers. Feel free to take my theory apart if i'm wrong

[Spanky The Dolphin]

There is already a widely accepted operation theory.

[Metrion Cascade]

There is already a widely accepted operation theory.

Which is?

[Crazedwraith]

There is already a widely accepted operation theory.

Which is?

Maybe the one Spanky's been talking about for the entire thread?
Electron shearing?

[Metrion Cascade]

There is already a widely accepted operation theory.

Which is?

Maybe the one Spanky's been talking about for the entire thread?
Electron shearing?

But his interpretation of that is that the blade does it without directly heating the material. And that all of the heat comes from the atomic vibration caused by the shearing. Which it can't:

*ahem* you cannot strip electrons from an atom without supplying the necessary energy to make up the difference in electrical potential energy states. That pesky First Law of Thermodynamics again.

*EDIT - Hence, Spanky is repeating an argument that's already been refuted. Yes, there is an accepted theory. But it's incorrect (or at best incomplete) and he's been apprised of that.*