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Sci-Fi Science

It Takes 2.99 Gigajoules To Vaporize a Human Body 272

Posted by Soulskill
from the just-so-you-know dept.
Have you ever wondered how much energy is needed to power a phaser set to kill? A trio of researchers at the University of Leicester did, so they ran some tests and found out it would take roughly 2.99 GJ to vaporize an average-sized adult human body. Quoting: "First, consider the true vaporization – the complete separation of all atoms within a molecule – of water. With a simple molecular structure containing an oxygen atom bonded to two hydrogen atoms, it takes serious energy to break these bonds. In fact, it takes 460 kilojoules of energy to break just one mole of oxygen-hydrogen bonds — around the same energy that a 2,000-pound car going 70 miles per hour on the highway has in potential. And that's just 18 grams of water! So as you can see, it would take a gargantuan amount of energy to separate all the atoms in even a small glass of water — especially if that glass of water is your analog for a person. The human body is a bit more complicated than a glass of water, but it still vaporizes like one. And thanks to our spies spread across scientific organizations, we now have the energy required to turn a human into an atomic soup, to break all the atomic bonds in a body. According to the captured study, it takes around three gigajoules of death-ray to entirely vaporize a person — enough to completely melt 5,000 pounds of steel or simulate a lightning bolt."
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It Takes 2.99 Gigajoules To Vaporize a Human Body

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  • well done (Score:2, Funny)

    by Anonymous Coward

    Just in time now that Texas can't get Sodium Thiopental.

  • Hmm (Score:5, Funny)

    by Mitchell314 (1576581) on Friday September 13, 2013 @06:41PM (#44844845)
    It's gonna take a mighty big shark to carry around that kind of firepower . . .
    • It's gonna take a mighty big shark to carry around that kind of firepower . . .

      Don't give the Sci-Fi -- I mean SyFy (sigh) -- channel any ideas. Sharknado [wikipedia.org] was bad enough.

    • Dr. Emmett Brown: No, no, no, no, no, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need.

    • by Darinbob (1142669)

      This is also more than the 1.21 gigawatts needed to go back to the future!

      • Nonsense. 2.99GJ is simply 1.21GW over 2.47 seconds.

        • "Nonsense. 2.99GJ is simply 1.21GW over 2.47 seconds."

          But it's all irrelevant, because OP's main premise is obviously false.

          If we want to take the situation even a little bit literally, then a phaser could not be "vaporizing" its target. If it did, there would be a tremendous explosion. In fact, 2.99 GJ worth of "boom".

          But we don't see that. Therefore a phaser could not be a "vaporizer" at all. Nor could it be a "molecular dissociation" device because the result could be the same.

          I would have to theorize that it was some kind of device to send matter

    • If the shark doesn't have enough power I suppose the shark could always hook onto a clocktower at precisely the right moment as lightening strikes.
  • Disintegration (Score:5, Interesting)

    by BasilBrush (643681) on Friday September 13, 2013 @06:42PM (#44844849)

    Phasers don't vaporise a person. They disintegrate them.

    Since we don't yet know the physics behind this phenomenon we can't say how much energy it needs.

    • The normal maximum setting on a hand phaser would vaporize a humanoid lifeform or a Human-size android with a single hit. (TOS: "What Are Little Girls Made Of?"; TNG: "The Vengeance Factor"; Star Trek: First Contact) This was also called disintegration. (ENT: "In a Mirror, Darkly, Part II")

      - memory-alpha.org

      Though I suspect the Star Trek phaser suffered from the same problems as the StarGate zat'n'ktel, in that the effect would be a wee bit too convenient for plot reasons - as I've rarely seen them use i

      • Re:Disintegration (Score:5, Insightful)

        by SuricouRaven (1897204) on Friday September 13, 2013 @07:12PM (#44845105)

        Often on TV, killing is actually easier than dealing with the bodies. The network censors really hate bloody corpses, but have less objection to the process of making them. A common solution is to introduce either mooks that conveniently diappear when dead (See Buffy, Charmed - the prefered fantasy solution) or weapons which leave no body (See half the weapons in Doctor Who or STs phasors - the prefered sci-fi solution).

        The vaporisation option usually ignores the difficulty of where approximately eighty kilograms of water vapor is going to end up - boiling a human in such a short time would result in a blast of high-pressure superheated steam and organic soup.

        • Re: (Score:3, Insightful)

          by westlake (615356)

          Often on TV, killing is actually easier than dealing with the bodies. The network censors really hate bloody corpses, but have less objection to the process of making them. A common solution is to introduce either mooks that conveniently diappear when dead...

          Saves money, Saves time.

          You don't have to show the blood and bodies on screen. You don't have to remove the blood and bodies on screen.

          The same reasons why Star Trek and Dr. Who have teleportation. Why the TARDIS is bigger on the inside than the outside.

    • by VortexCortex (1117377) <VortexCortex.project-retrograde@com> on Friday September 13, 2013 @06:53PM (#44844949)

      They're called "Phasers". I like to think that they don't disintegration or vaporize people, they just phase them into another dimension, a dimension where all the other folks who got zapped are hanging out, bitching about the Federation in some kind of distributed cosmic basement...

      ...and that's why the A.C.s here are so maladjusted.

    • What do disrupters do then?

      • Re: (Score:2, Insightful)

        by msobkow (48369)

        Disrupt molecular bonds, I guess.

        While phasers phase molecular bonds.

        In some theoretical sci-fi future, there is a difference.

        Perhaps the reason they are hand-held is they actually produce the energy needed as part of their discombobulation process by capturing the existing energy of the molecular bonds and redirecting it, sort of like a nuclear chain reaction. So it only needs a little zap of energy to kickstart the process.

    • by shrikel (535309)
      Agreed. I don't see why "vaporization" must be defined as "completely separating all atoms within a molecule." Evaporation and boiling are two means of vaporizing (making into vapor) without complete atomic separation.
      • by ultranova (717540)

        I don't see why "vaporization" must be defined as "completely separating all atoms within a molecule." Evaporation and boiling are two means of vaporizing (making into vapor) without complete atomic separation.

        Because most molecules in the human body are simply too big: the energy needed to separate them from each other is greater than the energy needed to break them apart. You can observe this behavior if you have a fireplace: a log of wood will first burn with a flame as volatiles evaporate and mix with

        • Most of the molecules in the body are not too big, as most of the body's molecules are water molecules. That is why the researchers used water as the body analogue. But when you talk about vaporizing water, you are just talking about turning it into water vapor, not separating it into its atomic parts. So to really get an accurate energy estimate for a phaser set to disintegrate, you need to calculate the energy required to turn the water fraction of the body into water vapor, plus the energy required to br

    • by riverat1 (1048260)

      I think the most logical way a phaser on disintegrate setting could work would be some effect that neutralizes the strong nuclear force. [wikipedia.org] Then whatever you hit with it would just disintegrate to a cloud of quarks.

    • Vaporize or ionize? (Score:5, Informative)

      by swamp_ig (466489) on Friday September 13, 2013 @08:23PM (#44845527)

      Hang on a moment... TFA isn't talking about vaporizing - turning water to steam. It's talking about ionizing, which is clearly going to require a much bigger quantity of energy.

      For actual vaporization, making a very rough calculation - 60kg person, 2,270 kJ/kg latent heat of vaporization of water = 136 MJ,
      Sure there's specific heat to add in there too, but the vaporization of water is the dominant term, so it's at least out by an order of magnitude.

      Lesson learned - don't try and be 'all sciency' and use the wrong jargon!

      • by petes_PoV (912422) on Saturday September 14, 2013 @03:22AM (#44847155)
        From TFA

        the complete separation of all atoms within a molecule

        And then what? You have <however> many moles of highly reactive ions in a location. What are they going to do? React again. So all you've done is apply energy to a mass, liberated a bunch of ions that will then recombine as soon as the input power goes away (or they dissipate from out of its field) and then release the energy of ionisation that they had absorbed. Result: Boom! All that 3GJ comes back at you as a chemical explosion.

    • by Darinbob (1142669)

      I thought a phaser basically writes someone out of a script.

    • Vaporization is not the same as hydrolysis. Vaporisation means liquid turning to vapor.

  • Bad science (Score:5, Interesting)

    by Dunbal (464142) * on Friday September 13, 2013 @06:43PM (#44844877)
    Since when does "vaporization" involve breaking chemical bonds inside a molecule? When you boil water you're not turning it into hydrogen and oxygen, you're just overcoming the vanderWaals bonds keeping the liquid together and giving them enough energy to float away. Likewise if you "vaporize" someone. You need enough energy to turn them from a solid/colloid state to a gaseous state, not the energy required to reduce the person to elemental atoms.
    • Re:Bad science (Score:4, Insightful)

      by DarkOx (621550) on Friday September 13, 2013 @06:53PM (#44844957) Journal

      Even so when you go from a liquid to a gas let alone a solid to a gas you increase volume by well allot! Considering the epic calamity that is ~man sized boiler, say the type that was used to power to power stream tractors makes when it bursts; it should be clear that a phaser blast is not turning the victim into a gas or plasma. If it did that, it would be very disruptive and probably harmful to anyone in the immediate vicinity. Yet in Star Trek you can safely stand next to someone that is being disintegrated by phaser/disruptor.

    • Re:Bad science (Score:5, Interesting)

      by mysidia (191772) on Friday September 13, 2013 @07:02PM (#44845031)

      You need enough energy to turn them from a solid/colloid state to a gaseous state, not the energy required to reduce the person to elemental atoms.

      I can't wait to see how much energy people say the transporter requires.

      I assume it is a similar principle.... except the phaser set to disintegrate just has to scramble and disperse their molecules, so that the person or thing no longer exists in a recognizable form; the transporter has to reassemble people.

    • > 2013
      > Not vaporizing your water with electrolysis.

      > Not enjoying the rich flavor of combustion brewed tea.
      At least ditch that wet drip coffee and try Fuel-Air-Coffee -- It's the bomb.

    • van der Waals forces are not the main factor that keeps water molecules together - it's hydrogen bridges and dipole-dipole interactions.
      In fact, in a water molecule, van der Waals forces are tiny.

    • Water is kept liquid more by hydrogen bonds than van der Waals. Compare boiling points of water (0 C, two free electron pairs to participate in H bonds), ammonia (-33 C, one free electron pair to H bond), and methane (-164 C, no free pairs).
  • by harvestsun (2948641) on Friday September 13, 2013 @06:45PM (#44844889)
    The phasers I remember just made their target clutch their chest and fall to the ground dramatically.
    • by multisync (218450)

      The phasers I remember just made their target clutch their chest and fall to the ground dramatically

      The phasers you remember were obviously set to Stun.

      • by mysidia (191772)

        The phasers you remember were obviously set to Stun.

        Even kill didn't do anything other than make the target drop dead.

        That is what disruptors do.

        At some point the Enterprise hand phasers got a Disrupt-B or Maximum setting besides overload, that makes the target glow, and vanish.

        You have to remember that star trek is a TV show; and the disintegration was clearly for dramatic affect. They were essentially making the phaser like alien death rays that had appeared in other television shows.

        The phas

        • by yurtinus (1590157)
          Vhy don't zey just waporize them?

          There's always room for another setting on a prop dial!
    • It happens in the presence of Khan Noonien Singh. Clearly the extra energy required to vaporize is derived from the presence of Ricardo Montalban [imdb.com].
  • by Zan Lynx (87672) on Friday September 13, 2013 @06:48PM (#44844907) Homepage

    Directly providing the power to vaporize a person is not the elegant way to do it. The correct, elegant mad scientist method is to use the power contained in the vaporized mass to power the vaporization.

    Consider if you develop a means to "program" a plasma such that it generates a contracting magnetic field that causes fusion inside the vaporizing object and then absorbs some of the energy from this fusion reaction to power itself.

    Now you're talking! Now you've got an effect that can vaporize any object provided you can provide the initial energy requirement.

    There could be variants on this. Perhaps you've got an effect that flips matter into antimatter and absorbs some of the released energy to continue the effect.

    If this is an expanding effect instead of a collapsing effect you've got a world killer like the weapons in Ender's Game.

  • by Tumbleweed (3706) on Friday September 13, 2013 @06:52PM (#44844945)

    *turns knob up to 8*

    Ready Player One...

  • by wonkey_monkey (2592601) on Friday September 13, 2013 @06:54PM (#44844967) Homepage

    around the same energy that a 2,000-pound car going 70 miles per hour on the highway has in potential.

    Wouldn't that be kinetic?

    • Could be an elevated highway...

    • Perhaps it is both? Speed it all relative, you really only realise that energy if you apply the breaks of hit something. So it is really just potential energy.
      Going really fast is like being really high, you have easily accessible potential energy.

  • ...do to the immediate environment? I suspect the poor soul that god disintegrated would be the lucky one.
  • by Sponge Bath (413667) on Friday September 13, 2013 @07:01PM (#44845025)
    Vaporization isn't needed to kill. I assume that's what death rays are all about. I suppose it would take a little extra to make the remains difficult to identify. If you've gone the death ray route, using lots of power is part of the "send a message" image thing anyway. For an eco-friendly kill, it is still best to club the victim and let hungry pigs dispose of the corpse.
  • Doesn't take gigajoules, just what is commonly done in crematoriums, but done at much faster speed for cinematic effect. I am sure most people will not mind a small puddle of calcium-based ashes, but if they do we can focus on sublimating that and still save lots of juice. For even more savings, add corrosive acid that would produce residue with lower sublimation point.

  • by JoeyRox (2711699) on Friday September 13, 2013 @07:12PM (#44845109)
    If successful we can work our way down list with future kickstarters:

    Ashton Kutcher
    Miley Cyrus
    Kate Perry
    Guy from Verizon Wireless commericals
    Congress
  • On things I've never wondered about, this would be pretty much right at the top of the list...now how much energy is required on the 'stun' setting?

    Must be Friday the 13th or something. :)

  • So does this also give an indication of how much energy an transporter(Star Trek like) would consume(assuming 100% efficiency of course)?

    I've always wondered how much energy would be needed for transportation like that. Always wanted to see if its more/less efficient than driving your SUV to work.

  • by craighansen (744648) on Friday September 13, 2013 @08:08PM (#44845447)

    I'm going to do some rough calculations - the paper's computation is also pretty rough - just to get the right order of magnitude.

    First of all, to vaporize water, you don't even need to boil it. Spill some water on the floor and it vaporizes pretty darn quick just from the ambient environment - it changes from liquid water at room temperature to water vapor at room temperature. The only heat that needs to be added is the "Enthalpy of vaporization" which is 2260 kJ/Kg. For the 78kg human described in the paper, if it were all water, that would only be 176 Megajoules. Given that a human is normally at about 37C and room temperature about 25C, you can also take away 4kJ/Kg*78Kg*(37-25) = 4 Megajoules that the water vapor releases as you cool it from 37C to 25C. The net result is that with 172 Megajoules, you can turn a human body's mass of water to vapor.

    However, as the paper suggests, the body isn't all water - it's about 85% water and 15% "dried pork." That means 172MJ*0.7 for the water, 146MJ, and the 11.7Kg of pork releases about 4KCal/g when oxidized (4 dietary Calories/g), 1 Kcal=4.2KJ, so burning the "dried pork" releases 196MJ. Assuming the "dried pork" gets fully oxidized (i.e burned) into CO2, the result is a gas. So overall, vaporizing a human body (in the sense of turning all the body into a gas) can release more energy than you started with - about 50MJ.

    The paper estimates the energy required to break every molecular bond. However, all those bonds are going to reassemble into something else, whether into H2, O2, or H2O, or including the "dried pork," CO2, releasing much of the energy back.

  • Holocaust deniers keep prattling on about how hard it would be to incinerate 6 million Jews. They full of sh*t because, as Nazis, Holocaust deniers know about the secret Nazi weapon that could vaporize entire cities and boil oceans [youtube.com]. With such a super Nazi death ray it was a sinch to vaporize millions of human bodies.
  • To turn 75kg of water (165lbs) starting at 37C to steam at 100C requires 190 megajoules. Wouldn't that be enough to vaporize a human body? I suppose the bones would be left behind.
  • It is ridiculous to use "roughly" and "2.99" in the same measurement. Seriously?!? A professor informed my engineering class that adding extra decimal places implied that that level of precision was known and/or required. It is at all plausible that the variability in the "average" human body is less than a one part per thousand?

    Sounds a lot like Karl Marx when he took material costs in "round numbers", "assumed" costs for spindles and rates of waste, arbitrarily "put" wear and tear at 10% and "supposed" a

    • Did you miss the "giga" that came after the 2.99? So that would be 2,990,000,000 Joules. Roughly.
      • by Zordak (123132)
        Yes, but order of magnitude has nothing to do with the number of significant digits. Didn't you take 7th grade science?
  • what happens when you use that at 88MPH?

  • How does that energy compares to what is needed to send a human body in the sun? That get the same result in the end.
  • by istartedi (132515) on Friday September 13, 2013 @09:44PM (#44845943) Journal

    Everybody knows that when set to kill the phaser emits high energy polarized tachyons that send most of the mass into other dimensions. From the PoV of the infinite other universes a harmless burst of neutrinos occurs at several random locations. The matter that doesn't get transferred by the tachyons may remain as a dusty residue, but that's only if the phase correlator is poorly adjusted. Properly maintained phasers set to kill won't do that.

    And yes, I just made all that up, and some of it is mumbo-jumbo. That's how Star Trek technology works. Dammit Jim, I'm a Slashdot poster, not a phaser technician. Why do I have to explain this?

  • The only "reasonable" explanation within the Star Trek canon (if the term applies) is that the corpses are pushed "out of phase" or into subspace or something. Otherwise, there really is no place for the mass to go.

  • I know where we are heading with this.

  • Phasers set on stun probably is the green way to go for energy savings! :)
  • That means a fully equipped DeLorean could vaporize you in 1.35 seconds of time travel.

  • Not roughly 3 GJ, but roughly 2.99!!!!! Clearly not written by anyone who understands engineering!
  • I'll leave my phasor set to "stun" in future. It will help extend the battery life.

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