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How possible would it be to become totally invisible?

  1. Apr 22, 2003 #1
    Ive not seen this hanging around here before so i thought i MIGHT bring it up :) how possible would it be to become totally invisible?

    I knwo there is this stuff about the natural phase (??) of everything, and if the phase can be changed then you become invisible? Is this possible? If so how far in the future are we lookign at building invisible machines!

    I mean, id be all for invisibility, but there would be certain risks involved, like for instance! Someone murders someone while invisible! or decloaks murders someone then recloaks so as not to be seen! maybe there would have to be certain inplants in the invisible device so it tracks where you are all the time! (unless your james bond ;);))

    any thoughts ?
  2. jcsd
  3. Apr 22, 2003 #2


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    Erm... I think the phase stuff is another one of theoretical science's concepts that got lost in the translation to popular media. I haven't seen any details about how any of these things can induce invisibility...
  4. Apr 22, 2003 #3


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    The idea is that if the incoming wave


    is returned back 180o out of phase the troughs of the reply will combine with the highs of the original to cancel out.
    ....\/\/\/\/\/\/\/\/ -->

    This is the basic idea behind stealth technology, where the fact that radar waves have wavelengths in the centimeter range gives them the opportunity to fudge things with shapes.
  5. Apr 23, 2003 #4
    How can photons cancell each other out?
  6. Apr 23, 2003 #5
    its an quantum mechanical issue, and is difficult to think about conceptuallly.

    try thinking about the energy involved...
  7. Apr 23, 2003 #6


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    Greetings !
    I suppose he meant locally in the observer device -
    that would be intentional invisibility, won't it ?

    A material the main orbital energy differences
    and ionisation energies of which are not in the
    visible wavelenght range and that is transparent
    to visible wavelenghts (like glass I think ?)
    is invisible.

    I think that we can use an optical cables' cover
    that can absorb and then emmit light coupled to
    a proper computer system (the simpler technology
    of capturing sun-light and transferring it into
    a building - like a window, already exists).
    - "We're right behind them, commander !"
    - "Good, we will eat their cowardly hearts for
    dinner tonight ! Arm all disruptor cannons and photon
    torpedoes ! Today IS a good day to die ! Decloack !
    Fire all weapons ! Q'apla ! "

    Live long and prosper.
  8. Apr 23, 2003 #7
    sta rtrek takes cloaking to a tee doesnt it :D:D:D

    and yes, cancelling out photons, thats where i rememebr it from :) we were doing cancellations and reinforcements in physics the other week and i thought of this...

    i tihnk to create this wouldnt be too difficult to conceive, hard to buiild but less difficult to conceivce, you build some kind of force shield, like an em bubble around you which repulses photons at juuuust the right time! very tricky and stuff but i suppose it could happen :) the problem is, are you actually invisible?

    what i mean is, the photons are not goign to the other guys eye riught, thus he cannot see you. However, you are blocking the photons from behind you getting to the geeezers eye, so would you just become a shadow of sorts? a black spot in a room!
  9. Apr 23, 2003 #8


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    Greetings !

    Bunting, it is not possible to really cancel
    out photons. (If two opposite radio waves
    would destroy each other and dissappear it will
    really mess up your energy conservation formulas
    and your reception. :wink:) What you can do is
    transmit photons of the same frequency in the
    opposite direction and allow them to cancel out
    locally in the area where they pass through
    each other. (Very high frequency - energy photons
    are so small and have such high momentum that
    they can experience non-elastic collisions with
    normal particles, like electrons.)

    Live long and prosper.
  10. Apr 23, 2003 #9


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    selfadjoint: But that wouldn't make you invisible. It would just prevent signals from you reaching the observer. ie. you would simply look BLACK. To cloak, you need to be transparent, not cancel out the waves.
  11. Apr 23, 2003 #10
    yeah, ok right so that isnt h answer, buuuut how about this.

    Evrything has a natural frequency right. It is theoretically possible to just walk right through a wall if you and the wall happen to have the same (or opposite, ive only touched on this subject) frequency at the same time. So MAYBE to cloak you need to be able to control this natural frequency.

    Any thoghts?
  12. Apr 23, 2003 #11
    I've never heard that before; I thought it was a variety of electromagnetic repulsion that keeps me from going through walls...
  13. Apr 24, 2003 #12
    well, thats what my physics teacher tells us anyway :)
  14. Apr 24, 2003 #13


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    I think the Army's approach to invisibility is much simpler. Put a camera in the back of your shirt, with the video feed cable running to the front. The front of your shirt is a video display that shows whatever the camera sees. So people looking at the front of you will see what the camera sees; they will see what is behind you. A similar camera in the front of your shirt carries a signal to the back. With a good enough camera and display screen, you should dissappear completely!
  15. Apr 25, 2003 #14
    ive also considered this, however i dont think it would be too great in built up areas and such, itd be great for desets and maybe jungles and places like that, but thwen there is alot going on itd be a bit crap :)
  16. Apr 25, 2003 #15
    To go through the walls you need high energy, ala cosmic x-rays. To get yourself to such energies, you'd look quite a lot like a nuke. Maybe quite viable idea - after seeing a nuke, its hard to believe they'd spot you afterwards

    Camera isn't very good, as it would work only in specific angle of view. You want to be transparent from all angles. Similar idea, and afaik has also been tried, is using fiber optic strands in thousands, pulling them from one side to other in ideal star topology. If density of strands is high enough, light refraction will make such "surface" look like flat. Even if not completely transparent, this gives very high degree of chameleon camouflage. Could be made in form of clothes. Though, angle problems remain also, even though this is like hundreds of cams and screens. Some holographic woodoo might help here.

    There's another quite simple and possibly doable idea. human eye sees shortest frame of about 10ms. All you need to do is to not stay in same spot for longer than 10ms and move randomly around. You'll vanish for a naked human eye. Difficulty to overcome is quite heavy instant acceleration due to required nonlinear movement and need to not return to same spot sooner than in about 1 sec, ie you'd need more space around you.
    You can test that method easily by shaking pencil violently and trying to notice how much of it you can see. You'll see blur because of linear motion. With random motion you'd hardly see anything.

    To become transparent at quantum level, it may be possible by reducing your body energy density to that of air or vacuum. I bet that hurts.
  17. Apr 25, 2003 #16


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    Hm..isnt this what happens in quantum tunneling..but with particles instead of people?..I just know the general idea of this, but its like borrowing energy for very short periods of time?

    OK..and the 10 ms idea....thats you popping up in random places 100 times in a second....

    I think your eyes see something like 30 pictures per second? so that would be one every 30 or so milliseeconds right?so..wouldnt there be a one in 3 chance for them to see you every time you bounce around? or is my logic flawed here....hm..maybe its my units...heh..milli is 10^-3.yea..right?
  18. Apr 25, 2003 #17
    30ms is when eye is able to create movie. Single snapshot under 10ms goes undetected to you, completely (unless its overflashed). 3 snapshots under 10ms in same place makes it 30ms for your eye. small movements in between, and you see movie. Thats why its important to be at random points and very shortly - eye would be unable to grab the image. Brain will fill in what was behind you before and after.
  19. Apr 28, 2003 #18
    Maybe sometime scientists good genetically engineer humans who have no pigment whatsoever in there system, kinda like albinos, but instead, none of there body has any color. You know, make them translucent and stuff. Sign me up! lol
  20. Apr 28, 2003 #19
    Even if our bodies were transparent, we'd still be visible because our tissues would distort the light going through us.
  21. Apr 29, 2003 #20
    Forgive me if someone else has already posted this, but has anyone else seen, on the news, about that cloth devloped that allowed people to be invisible? Unfortunately I caught the very end of it, so perhaps it was just a joke or something.
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