In a type III civilization probably even type II, would have developed solid energy construct resembles force shield which acts like a semi-permeable membrane to allow friend to pass but prohibit strangers. I am imagining an advanced civilization which draws its power directly from the nearby star would eventually develop a lightsaber (object borrowed from star war universe) can conveniently tear through foe like paper but completely useless on friend. Is it possible and how would it work?

Imagine possible application in surgical procedure, this saber can destroy malignant cells while ignore benign one. Updated

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    $\begingroup$ I pity the beta tester. $\endgroup$ – erikpartridge Mar 30 '15 at 2:53
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    $\begingroup$ @erikpartridge there is no need for concern just like star war clone war there are plenty to go around ha ha ha ha... [laughing menacingly] $\endgroup$ – user6760 Mar 30 '15 at 2:55
  • $\begingroup$ Is this comic book science, or science science? $\endgroup$ – Schwern Mar 30 '15 at 6:36
  • $\begingroup$ @Schwern neither $\endgroup$ – user6760 Mar 30 '15 at 8:39

I have my doubts to the plausibility of a discriminating light sabre. For that matter, I have my doubts about any friend-or-foe identifying system that acts fast enough to be a weapon.

First, lets divide the system into two parts;

  1. Identifying friends and foes.
  2. Blocking/cutting/sabre-ing those that you don't like (your foes).

It's impossible to ignore Part 1 because you must be able to handle situations where friend and foe are physically touching, say, holding hands, or one has another in a headlock.

The engineer building this could decide that as a matter of policy, if friend is touching foe, then neither of them are allowed through. This is simple, but creates problems with the proposed cancer-killing-laser-scalpel.

Having your scanner inspect every cell's DNA against a database would be a thorough way of discrimination. But you'll want your scanner to have the following attributes;

  • scan quickly,
  • scan thoroughly,
  • scan at-a-distance (as in without having to scrape a cell sample)
  • and without obliterating the cell while doing so.

This is something I don't think any Type II or Type III civilisation is going to be able to do - it's just a limit of physics that leaves DNA proteins too fragile to work with that quickly.

If you slow the system down, again, you may have a system like modern security screening procedures - one locked door, a walkway, and another locked door. Your identity is checked and confirmed within the walkway. If you pass, the second door unlocks. If not, you get trapped, and armed-guards and attack-dogs are set upon you (that is a joke).

If you didn't go down the DNA verification path, you could try computer-vision with machine learning. This is a bit of a hot topic in academia at the moment as we've just now gotten to the point where computing power is both fast- and cheap-enough to identify objects in pictures and video in real time.

It's never going to be a foolproof system. The problem here is that your foes could just wear masks and make-up to look like friends. We have this problem today, and we get around by testing for unique properties that can't be fabricated - like fingerprints, retinal details, and DNA. Unfortunately, that puts us back at square one.

Part 2: tear through foes like paper (the fun part)

Take your pick! With the energy of a star available, energy efficiency is never going to be a concern.

To me, solid energy construct, and semi-permeable membrane seem to be incompatible with each other. If it's solid, then foes physically can't enter, but then we wouldn't have the spectacular immolation of our foes to witness!

My favourite system would be to hide a particle accelerator under the floor. Specifically, a dirty great electron gun. Point it upwards at your foes' feet, and tune it so that electrons have just the right amount of kinetic energy to tunnel (the quantum-mechanical effect) through the floor-boards, and into the bottom millimetre of your foes' shoes.

That layer instantly melts, vaporises, then blasts away as a sheet of plasma. Gravity takes hold and remainder of your foes' shoes drop to fill the now empty space.

This process repeats until there's no more shoes, no more feet, legs, and finally no more foe! All that's left is a room full of hot, smoky, atoms.

...and two footprints.

  • $\begingroup$ in superman universe a piece of kryptonite can generate a kind of radiation which can cause harmful effect to the biology of clark kent. On Earth we can emit a ultra frequency of sound to shove nasty pest such as mosquito without affecting our health. As for part 2 can I don't mail out invitation cards? because I like to play away more, thanks. $\endgroup$ – user6760 Mar 30 '15 at 6:16
  • $\begingroup$ @user6760 Wow, its in Superman, so it must be possible. Also, HAVE YOU EVER TRIED THOSE ULTRASONIC CRAP? $\endgroup$ – Aron Mar 30 '15 at 9:41
  • $\begingroup$ @Aron chill no need to shout I'll agree with you on the ultrasonic thing it's a piece of decoration nothing more. Drinks on me $\endgroup$ – user6760 Mar 30 '15 at 9:45
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    $\begingroup$ @user6760 You've never lived in a mozzy infested area have you? There are few pleasures like plucking the wings off a live mozzy, the few times I have caught one live. Nay, best they commit suicide than fall in the hands of the foe, muahahhahahahahhahhaah. $\endgroup$ – Aron Mar 30 '15 at 9:48
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    $\begingroup$ "For that matter, I have my doubts about any friend-or-foe identifying system that acts fast enough to be a weapon." We (the US) already have guns with programmable bullets that explode after a specified range (eg shoot over a wall, explode, kill people hiding behind a wall), and video-game-style auto targeting scopes and rangefinder systems. It isn't really a stretch to combine those technologies with things like RFID chips or other similar passive ID technologies to make bullets or turrets or guns behave how we want them to. $\endgroup$ – TylerH Mar 30 '15 at 14:11

Yes, it is possible. Foes would have to wear a "foe badge" that contains a chip that sends out a radio signal indicating that they are a foe. Upon detecting such a signal, the the lightsaber setting would automatically change from training mode (no damage) to kill mode (maximum damage).

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    $\begingroup$ You should probably invert that into "friends should wear a friend badge", if you were being serious. It seems unlikely your foes would be as cooperative. $\endgroup$ – Erik Mar 30 '15 at 5:13
  • $\begingroup$ @Erik But what if a foe were to steal a friend badge? In my solution, badge stealing does not help anything. $\endgroup$ – Atsby Mar 30 '15 at 5:19
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    $\begingroup$ @Erik If I may read between the lines, I think Atsby is pointing out that identifying a Foe is a particularly hard problem, and we have little reason to believe it gets easier for a type II or III civilization. However, if said civilization ever could get the foes to wear a "foe badge," it could work. However, I can think of a few clever ways where we have convinced people to wear a foe badge in the past, so it might actually have some potential. $\endgroup$ – Cort Ammon Mar 30 '15 at 5:41
  • $\begingroup$ Remember in Robocop last year, ED-209 will never target on all green tag also applies to Murphy. The plot pit Murphy against the a human wearing green tag but Murphy still exacted revenge. Maybe we can put Murphy's brain into all lightsaber and that'll put all your argument to rest agree? $\endgroup$ – user6760 Mar 30 '15 at 5:44
  • $\begingroup$ The military use a system called IFF or Identification Friend or Foe. It's like your badge idea, but it only lets you identify friends. Everyone else is just an unknown. I don't know what sort of social engineering would make your enemy broadcast that they're the enemy. $\endgroup$ – Schwern Mar 30 '15 at 6:35

Um, not really, either it would have to be programmed for those you want it to ignore, or they would need a 'beacon' to ignore or it would have to have a telepathic link with the wielder. and all three scenarios could be circumvented or used to the detriment of the wielder.

Beyond that, a lightsaber is an energy weapon, is designed to eliminate enemies with extreme prejudice. being able to swing through a friend to hit the foe behind not touching the friend would basically need to 'teleport' the energy past the friend. At that point why are you in a physical sword fight?

  • $\begingroup$ I'm enrolling in jedi academy and I don't want them to find out I can't use the force, so it gonna be the lightsaber! I don't wanna accidentally strike down my spar buddy you know. $\endgroup$ – user6760 Mar 30 '15 at 14:03
  • $\begingroup$ @user6760 if you're buddy can use the force, you won't! $\endgroup$ – bowlturner Mar 30 '15 at 14:04
  • $\begingroup$ I cheated the entrance exam paid the school fee and going to start lesson on how to swing lightsaber and they say no dummy lightsaber. If I can use the force I will be in complete control and can sense the position of my lightsaber and swing it around without spewing blood everywhere. $\endgroup$ – user6760 Mar 30 '15 at 14:09
  • $\begingroup$ @user6760 My point was, if your classmates can use the force, you won't be able to hit them even if you try. $\endgroup$ – bowlturner Mar 30 '15 at 14:12
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    $\begingroup$ I think you keep changing the goal posts. Also with a lightsaber,whether you have the force or not, the most dangerous target to a novice would be the wielder. Try not to cut off a limb or your head. Regardless, you asked if it was 'possible' I say no, doesn't matter your 'need' for one. $\endgroup$ – bowlturner Mar 30 '15 at 14:17

Sort of; What are the assumptions going into the type III civ? They certainly have the power available to them. The particular physical manifestation that would appear to be the "lightsaber" would never have all of the abilities that you appear to be asking about in the form desired; but that really isn't a problem as the physical lightsaber very well could be basically a prop for the rest of the weapon; as we are dealing with available galactic scale engineering here.

It is fairly obvious that threat detection and determining who is a friend or a foe is going to have to be something that in our own not even quite Type I world will be handled quicker than humans are able to fully handle in the near future so being able to handle that decision at the speeds at which a person is swinging a sword and then selectively damaging or not the foes based on that seems reasonable.

The real question is, why would one be swinging a sword in that situation? If the weapon has the ability to determine who is a friend and a foe and to selectively destroy foes, basically at will, with the stupidly showy display of power of an energy beam sword, then just automatically have it zap all foes in range quicker than one can think and be done with it, unless they aren't really foes and they aren't really dying but you are filming some Star Wars sequel, or trying to have the locals worship you as a god and your AI doesn't have the free will to tell you that you are completely bonkers or something like that.


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