1. Garball
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    Garball Sometimes nothing can be a real cool hand. Supporter Contributor

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    FTL atomic shrapnel

    Discussion in 'Science Fiction' started by Garball, Jun 8, 2014.

    Contemplating warp speed or FTL speeds, and after reading another thread that stated aerodynamics would become more important the faster a ship travelled through a not so complete vacuum, would collision with atomic particles be possible at those speeds?

    Stick with me, I'm in a philosophical mood (drunk).

    Being shot with a .22 caliber rifle at 1200ft/s would be the same as me running at a floating bullet at 1200ft/s, correct?

    This becomes a question for the sober mathematicians. If a 70 grain bullet traveling at 1.7 times the speed of sound can be lethal, at what velocity would a small molecule or speck of dust become a deadly projectile?
     
  2. Wreybies
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    Wreybies The Ops Pops Operations Manager Staff Contest Administrator Supporter Contributor

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    Numerous concepts I have perused on the net include an ablative fontal shield, understood to be a "consumable", and thus a one-trip-use item. Other ships, like bussard ramjet ships, don't try to avoid or deflect the oncoming matter, but instead depend on it as their fuel and funnel it via a proposed magnetic cone, the field of which flairs outward from the nose of the ship, guiding the matter down toward the middle and through the ramjet.

    [​IMG]
     
  3. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    What's the kinetic energy required for the projectile to become deadly? (I tried looking it up but found nothing; maybe you'll have better luck.) Set that equal to 0.5 x mass x velocity^2 and solve for the velocity.

    I'm sure I'm simplifying things a lot, but I think this makes for an OK estimate. I'm sure better physicists than I will stumble upon this thread and give you a better answer.
     
  4. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    Whoops, I just realized that you'd have to use the kinetic energy formula from relativity, which actually doesn't work for speeds greater than the speed of light. So I'm at a loss.

    On a related note, I find it amazing that science fiction readers and writers can find clever ways around such problems (for example, the stuff in Wrey's post).
     
  5. Robert_S
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    Robert_S Contributing Member

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    Well, it's not so much the energy a bullet imparts on the target as it is the damage to vital organs it causes. However, the energy of said bullet is:

    KE = 0.5 * m * v * v, with m measured in kg and v in m/s (so I'll have to convert the numbers to SI units to work for me).

    KE = 0.5 * 0.0045359237 kg * (365.76 * 365.76) = 303.4 J

    The mass of subatomics varies on the particle, but at or near c, you have to use Einstein's equation:

    E = mc^2

    I'll use electrons since they're the lightest.

    E = 9.10938291(40)×10−31 * ~9 * 10 ^ 16 = ~ 8.1 * 10 ^ -14 J

    You'll need to determine the density of particulate space because it won't be a single particle that threatens, but a whole lot of them ganging up.
     
  6. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    ^ Wouldn't Einstein's equation no longer hold since you're now talking about going faster than the speed of light?
     
  7. Robert_S
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    Robert_S Contributing Member

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    True, but if we are going there (FTL), then we really shouldn't have to worry about particles because we've already broken a known law of physics.
     
  8. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    I'm thinking maybe it's better to not mention or go into details about such things. Or invent some fake force that pushes particles away from the spaceship at speeds faster than the speed of light. :p Then again, I don't read much sci-fi, so I'm not sure how such things are normally handled.
     
  9. Robert_S
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    Robert_S Contributing Member

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    I wouldn't bog the story down with the details of the technology, unless the story is about the technology. I'm writing my story about two people, 15 distinct sentient civilizations and the effect the tech had on the two and the two on the civilizations. But the story is certainly not about how the tech works, only what it does to a man and how he harnesses the effect to affect civilizations.
     
  10. Lewdog
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    Lewdog Come ova here and give me kisses! Supporter Contributor

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    Silly question here, but if someone had the technology to create a ship to go the speed of light, wouldn't they also be able to take some of the same power source used to create that, to also create some kind of force field to protect the ship?
     
  11. Karwedsky
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    Karwedsky Member

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    As an object's velocity increases so does it's mass. It gets increasingly hard to accelerate an object towards the speed or light or potentially beyond, because the objects gets heavier and heavier the more you accelerate, requiring more and more fuel.

    Most theoretical concepts of FTL or warp drives either use an alternate dimension outside of our universe as a travel medium, or warp the actual space-time around the craft or in front of the craft in order to travel faster than light and get around the seemingly insurmountable fuel requirements.

    So if the craft is traveling through another dimension then it possibly wouldn't interact with particles or objects in our universe along its origin to destination path. If it is warping space-time around the craft to speed along then objects and particles would possibly bend around the craft and never touch it due to space-time being warped and bent.
     
  12. Vandor76
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    Vandor76 Contributing Member

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    FTL is purely fictional at the moment so let's speak about slower than light but very-very-very fast travel.
    As @Robert_S pointed out the kinetic energy of one particle is not really high.
    There are heavy particles (heavy compared to an electron) speeding at almost the speed of light just everywhere in space. These are called cosmic rays and according to the Wikipedia article some of such particles have high kinetic energy :
    http://en.wikipedia.org/wiki/Cosmic_ray

    These are of course particles with the speed of something like 99.9999999999999% of the speed of light so if a ship travels "only" at about 90% of lightspeed it is much safer :)
     
  13. tionA
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    tionA Active Member

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    don't listen to Kawedsky or to the others here. they know nothing about FTL travel. a body's mass does not increase with velocity cuz mass is invariant under a lorentz transform. they are referring to a body's 4-momentum, which is another story. and you can certainly go faster than light if you start at FTL. consider tachyons which travel FTL and are required in many current accepted theories of physics, like quantum field theory and such.
     
  14. Robert_S
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    Robert_S Contributing Member

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    Tachyons are purely hypothetical. There is no proof they exist.

    However, it's true that its bad form to think in terms of relative mass. It's better to think in terms of relative energy or momentum.
     
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  15. Robert_S
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    Robert_S Contributing Member

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    Not really. A 1kg mass is still a 1kg mass at or near c. It's an effect that is purely mathematical as it relates to force and energy which is why its better to think in terms of relative energy or momentum rather than mass. However, you can't get to energy or momentum without a starting mass at rest, but that doesn't mean the mass increases. Only the energy it imparts or the amount of force needed to affect a change in its velocity.
     
  16. tionA
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    tionA Active Member

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    Robert: tachyons do exist, they just haven't been found yet. they naturally fall out of QFT as a prediction, if an inconvenient one at dat. u are also incorrect about mass not increasing. mass does indeed increases with relative motion, cuz that is the whole point of special relativity. proper mass remains the same in the coordinate where u make the measurement.
     
  17. Robert_S
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    Robert_S Contributing Member

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    Then there is no proof they exist and the statement that they are hypothetical stands.
     
  18. tionA
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    tionA Active Member

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    u have much to learn. we are surrounded by fields that are tachyonic in nature. we even take their integral and renormalize them so they appear to respect causality when in fact they travel backwards in time.. read more. use your brains lol
     
  19. Robert_S
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    Robert_S Contributing Member

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    Haha, if you really want your position respected, you need to clean up your atrocious SPaG. Especially if you're going to post to a writing forum.

    As it is, you look like a dogmatic Christian and/or deluded conspiracy theorist.
     
    Last edited: Jul 26, 2014
  20. tionA
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    tionA Active Member

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    lol tionA is not dogmatic or deluded; tionA is a professional relativist. mass does not increase with speed and tachyons are an integral part of field theory, amateurs wannabes and ''atrocious SPaG'' notwithstanding.
     
  21. Robert_S
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    Robert_S Contributing Member

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    It's difficult to see the "professional" through all the terrible writing. As a relativist, you yourself should see the importance of good writing in relation to being professional.
     
  22. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    Apparently the mass of tachyons is imaginary. So how the hell can they exist?
     
  23. Garball
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    Garball Sometimes nothing can be a real cool hand. Supporter Contributor

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    Because my equation says so
     
  24. Simpson17866
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    Simpson17866 Contributing Member Contributor

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    In lay terms, "imaginary" means "doesn't exist." In official, technical, mathematical definitions, "imaginary" does not mean that.

    I could say that negative numbers "don't exist," but economics depends on being able to subtract beyond 0. Likewise, imaginary (mathematical definition, not lay definition) numbers are also important to real world calculations.

    http://en.wikipedia.org/wiki/Complex_number#Applications

    Tachyons having imaginary (mathematical) mass does not mean that they are imaginary (colloquial), it just means that they are out of phase with normal matter in some way.
     
  25. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    Sure, imaginary numbers may be important, but when you're talking about real, measurable properties, I find it hard to believe that mass can actually be imaginary. Just because a solution makes sense mathematically doesn't mean it makes physical sense. As far as I know, no evidence of imaginary mass, or even negative mass, has been found.
     

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