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How Hot Would a Light Saber Really Be? 410

Posted by Cliff
from the whizzz-vroom dept.
Datagod asks: "Has anyone ever calculated the temperature you would need to be able to slice through steel like it was thin air? How hot would a light saber really need to be? Also, I am assuming that at least some of the metal would be vaporized and the expanding gas would fling bits of molten metal at the saber wielder. Wouldn't your average Jedi be horribly scarred from all this."
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How Hot Would a Light Saber Really Be?

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  • Duh (Score:4, Insightful)

    by TheRealMindChild (743925) on Saturday April 01, 2006 @01:49AM (#15040287) Homepage Journal
    A real Jedi would jusst use the force to repel any bits away from him!
  • by tuxlove (316502) on Saturday April 01, 2006 @01:51AM (#15040302)
    Light sabers work at the subatomic level, disintegrating matter. However, heat is generated within resistant materials, giving the impression that the sabers themselves are actually hot. Don't the slashdot guys know this?
  • by Bananatree3 (872975) on Saturday April 01, 2006 @01:54AM (#15040315)
    Looking at this comment I found [bautforum.com], the author makes a good arguement: If the light sabre were hot enough to easily melt stuff, wouldn't it radiate so much heat that it would burn the user?
  • Shadows (Score:3, Insightful)

    by Bombula (670389) on Saturday April 01, 2006 @01:55AM (#15040319)
    I remember getting scolded by some fanboys for suggesting that lightsabers should cast no shadows (apparently they must cast shadows since shadows were present in Episode 4...) because the cutting edge - whether plasma or whatever else - would need to be hairline-thin regardless of temperature in order to slice through things without causing unmanageable explosions of melted and vaporized target material.
  • by heiders (811021) on Saturday April 01, 2006 @02:01AM (#15040348)
    Dunno about you, but I've never seen "steel" on my periodic table. Maybe I have the unpatched version...
  • by Centurix (249778) <centurix@gmai l . c om> on Saturday April 01, 2006 @02:02AM (#15040350) Homepage
    They are of course running at room temperature. You think it's heat that cuts through this mental abstraction you call 'matter'?
  • so it depends (Score:2, Insightful)

    by ridgecritter (934252) on Saturday April 01, 2006 @02:04AM (#15040362)
    on how thick the light sabre active region is. If it's only a few molecules thick, the amount of material vaporized will be relatively low, given that most stuff it's slicing doesn't have very high thermal conductivity (limits heat spread away from the blade). It's too late at night to push the specific heat & volume numbers, but as a guess, if the active region could dump, say, 100KW minimum into a 10nm x 2" x 60" volume, there would be plenty of energy to immediately vaporize any material in that small volume. Since there's not much material being vaporized, there won't be much damage to surrounding entities (like the Jedi sword wielder) or fixtures. As for temperature, I think that will depend on the specific heat of the material being sliced, if we assume that the energy integrated over time being dumped into the material is constant. Something with a low specific heat (air, wood) will get to a higher temperature than something like water or flesh. Once you get over around 5000K, everything's a gas. Another way to determine the temperature would be to look at the emission spectrum of the air when the blade is energized. That would tell you how hot the air is within the blade active region. However, there seem to be big differences between the emission spectra of the Good Guys vs. the Bad Guys. That could complicate the determination of temperature. Just like the 4/1 Slashdot color scheme.....
  • by jd (1658) <.moc.oohay. .ta. .kapimi.> on Saturday April 01, 2006 @02:08AM (#15040378) Homepage Journal
    However, it's not a simple plasma. It would have to be a high energy density plasma, in order to look solid and act solid.


    The example I found of a Tocamac plasma [pppl.gov] is only red, but is 20-30 million degrees C. However, the lightsabers in the original (and therefore One True) Star Wars were white. This means they must be considerably hotter. The page I found on near-solid high energy density plasmas [utoronto.ca] also talks about tens of millions of degrees - my gut feeling would be that to produce totally solid white plasma would require 40-50 million degrees C.


    Now, plasmas at that kind of temperature could quite reasonably be expected to slice through almost anything - steel included. Furthermore, anything that was vaporised would be repelled by the magnetic field and thus travel AWAY from the wielder. This does mean that if you are fighting someone with a lightsaber, you will get sprayed with high-energy plasma every time they hit something.


    There is one minor problem, though. Energy. If you want to maintain something at 50 million degrees, AND a containment field, a couple of duracel batteries won't cut it. Even lithium batteries will go flat very quickly. My guess is that the handle of the lightsaber, therefore, contains a wormhole linked to a gigantic anti-matter reactor.


    All you REALLY need to do, then, is find out where your opponent's reactor is hidden and turn it off. Their lightsaber will then be useless.

  • Re:Mod me please? (Score:5, Insightful)

    by 4D6963 (933028) on Saturday April 01, 2006 @02:13AM (#15040392)
    It's all good, today is not a good day to have mod points anyways, I guess.

    Seeing how the grand-parent got modded, I conclude that I hardly understand any logic in the modders mind anyways. Instead of considering using quasars for encryption, they should rather consider using /. mods.

  • by Dr. Spork (142693) on Saturday April 01, 2006 @02:15AM (#15040401)
    I always pictured the light saber to be something like tamed lightning. As it cuts metal, it doesn't melt it from heat but from the actual cutting action of really fast elecrons (or whatever) colliding with and knocking loose whatever the light saber touches. Except it couldn't be electrons because they'd be grounded out by the metal they're cutting, so it's some other sort of particle.
  • by RsG (809189) on Saturday April 01, 2006 @02:20AM (#15040412)
    Eh, suspension of disbelief only goes so far.

    It's been awhile since I watched the movies. I do remember that it wasn't just the ewoks that bothered me, in terms of suspension of disbelief. Most of what I found hard to swallow about the series was either science/engineering stuff ("laser" weapons that shoot bolts, a planet sized spacecraft with an unprotected vent leading down into the reactor), or plot holes. However, those can be excused if you take a step back and look at star wars as fantasy, rather than sci-fi. It may be unrealistic, but it's mostly internally consistant.

    What bothers people about ewoks is that they break from that internal consistancy. Here we have a mighty empire, ruling thousands of systems, with energy weapons, walking tanks and armoured soldiers - and they get their asses kicked by teddy bears with spears. How the hell are we supposed to see the empire as being this massive military superpower, when pointy sticks are all it takes to kick their asses?

    I think most people would have been fine with ewoks if they'd at least been carrying stolen imperial guns or something. It still would have been silly, but suspending disbelief would have been simpler.
  • by jakethejuggalo (718693) on Saturday April 01, 2006 @02:28AM (#15040432)
    agreed. one of the tests to see if you built a lightsaber properly is to hold the blade near your hand and see if it emits heat. if it does not, you've built it properly. (i believe that was in one of the jedi academy books)
  • by Jeremi (14640) on Saturday April 01, 2006 @03:15AM (#15040588) Homepage
    Sure. No one said Jedis were omnipotent


    I'm going off topic, but I think today's as good a day as any to do so... is it possible that at some point God renounced his omnipotence? As an omnipotent being, he would certainly have the power to do so... but of course he might not be able to undo it afterward, being no longer omnipotent. Perhaps he painted himself into a corner that way.


    It would certainly explain the steep decline in the quality of miracles these days [bbc.co.uk]...

  • by ThosLives (686517) on Saturday April 01, 2006 @11:19AM (#15041707) Journal
    It's more concise to answer:

    "I cannot answer your question because it contains inconsistent assumptions."

  • by Eric Coleman (833730) on Saturday April 01, 2006 @12:25PM (#15041986)
    Can God create a rock that he can't lift? To give background information on this riddle, it is of the form where you have a card or piece of paper. On one side it says "The statement on the other side of this paper is true." On the other side it says "The statement on the other side of this paper is false." I'm not sure what the logical term for this type of paradox is called, but the God/Rock idea is very similar. The circular reference in the quoted riddle should be obvious. The solution to this riddle is not a question of God's power. As with most riddles the answer is found by using a vague or misleading definition of a word. The key term in this riddle is "lift." If God created a rock that consumes(replaces) all of spacetime then there is no concept of "up", therefore the rock can not be "lifted" in the normal sense of the term since "lifting" is relative to some other object. With this solution you have achieve a dual state instead of a nonsense state. If an entity can create this hypthetical "omnirock" then the free will of God comes into play. He can create a state where he can not lift the rock and can also create a state where he can by creating a smaller object in space move/lift the first rock; ultimately allowing relative movemnent. The final solution is that both states are possible and exist simultaneously. Look up 'Schrodinger cat' on google. QED

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