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question stems from the following answer on SciFi StackExchange: http://scifi.stackexchange.com/questions/6404/in-stargate-is-there-an-in-universe-explanation-of-the-cumulative-effect-of-zat/6405#6405

This answer was basically an attempt to propose (in very general terms) a "realistic" implementation of a Zat'nik'tel (Zat guns) in "Stargate SG-1" sci-fi show that have the same effects as those in a show.

The effects shown are:

  • First shot stuns the victim
  • Second shot kills the victim
  • Third shot disintegrates the body of the victim completely.

The answerer tried to explain the first two effects with a certain degree of plausibility by the fact that the Zat gun fires an electron beam. A first shot overwhelms human neural system with the electric charge, the second overloads it to death with additional charge. So far so plausible, at least for certain values of plausible. For the purposes of this question let's assume these work as described.

The problem - and the meat of my actual Physics question - is the fact that - to explain the disintegration effect of a third shot - the answerer proposed that the gun fires not electrons but positrons.

This seems like a completely unworkable approach to me, for 3 reasons:

  1. First of all, positrons would only annihilate the electrons in victim's body. NOT protons and neutrons. I don't think that would lead to disintegration effect.

  2. Second, being a "ray gun", wouldn't the annihilation happen in the small area of the ray's impact on the body, NOT affecting the entire body?

  3. Most importantly, it seems to me that if the ray gun emits positrons, it would NOT have the original 2 effects attributed to electron-emitting energy weapon. Namely, would not stun and then kill the victim by overloading the neural system with the electrical charge.

THE QUESTION:

Making the assumption that we can somehow make a positron based energy weapon, are the 3 concerns above regarding its effects NOT being the same as SG-1's Zat gun correct assuming all the standard physics laws?

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We should discuss the Kill-O-Zap from Hitchhikers Guide first, because it is older. –  Georg Oct 25 '11 at 5:49
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it would create a small nuclear explosion near the gun itself, because of air molecules themselves.. –  Vineet Menon Oct 25 '11 at 5:51
    
This explosion would start in the outlet window of that fantastic "positron tube". –  Georg Oct 25 '11 at 6:02
    
I guess it is going to need some serious 'earthing' too! –  Nic Oct 25 '11 at 11:01
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The Lazy gun (Against a dark background) is the only ultimate weapon with a sense of humour –  Martin Beckett Oct 25 '11 at 15:15

2 Answers 2

Lets tackle this bit by bit.

  1. First of all, positrons would only annihilate the electrons in victim's body. NOT protons and neutrons. I don't think that would lead to disintegration effect.

    The resulting energy in the blast (converting the rest energy of the lepton pair into photons) might be enough to annihilate the rest of the body, though the resulting flash would not be signature of the weapon.

  2. Second, being a "ray gun", wouldn't the annihilation happen in the small area of the ray's impact on the body, NOT affecting the entire body?

    See the answer above, it might be 'possible' that it would cause a chain reaction and destroy the whole body. Though unlikely.

  3. Most importantly, it seems to me that if the ray gun emits positrons, it would NOT have the original 2 effects attributed to electron-emitting energy weapon. Namely, would not stun and then kill the victim by overloading the neural system with the electrical charge.

    The positron ball/beam would still be highly positively charged, causing damage to the nervous system. Whether this would happen before or after the positrons annihilated is dubious at best.

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The most significant thing is that an electron beam is highly charged, and would blow itself up. Similarly for a positron beam. –  Ron Maimon May 26 '12 at 2:38
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@RonMaimon Charged particle beams inside the atmosphere can self-focus (under certain conditions). See page 10 of this report for more details and fig. 9 of this other report for (very low quality) images of endoatmospheric beams. –  mmc May 26 '12 at 6:29
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@mmc: This is surprising, but true for electron beams, thanks for the link--- it seems the electron beam will produce an positive ion channel in the atmosphere where they can propagate without exploding, like carving out a lightning bolt path which conducts the current from the source to the target. I am pretty sure the same isn't true of positrons, since you can't create a negative charge balancing region by shoving out electrons, so you need an electron-filled channel, and there might be high losses from annihilation in the atmosphere in the channel itself. It depends on the cross section. –  Ron Maimon May 26 '12 at 7:53

The answer is really much simpler than all the answers indicate: the answer is, 'no'. That is not the way such massive gamma radiation affects the body. Yet gamma rays would be the main result of a positron ray gun. Gamma rays do not stun, they damage tissue. It is like a sunburn on your insides in addition to doing more subtle damage to rapidly dividing cells.

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