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Physicists Turn Pull Into Push

Posted by samzenpus on from the push-me-pull-you dept.

sciencehabit writes "It's textbook physics: An electric charge near the surface of a material gets pulled toward the surface. However, if the charge is spread out into the right shape and moves fast enough, that attraction becomes a repulsion, one physicist calculates. The odd finding could help physicists avoid unexpected effects when guiding beams of particles such as electrons."

38 of 60 comments (clear)

  1. Repulsion Engines Online by lawnboy5-O · · Score: 3, Interesting

    Make it so!

    1. Re:Repulsion Engines Online by earls · · Score: 1

      Amen. Antigravity, finally.

    2. Re:Repulsion Engines Online by Tough+Love · · Score: 4, Insightful

      If it works, it's antigravity just as much as a table leg is. In that sense, we have already had antigravity for some time. What you really meant to say is: land speeder, finally.

      --
      When all you have is a hammer, every problem starts to look like a thumb.
    3. Re:Repulsion Engines Online by able1234au · · Score: 1

      Where's my tractor beam?

    4. Re:Repulsion Engines Online by tepples · · Score: 1

      He wanted a hoverboard instead, helluva lot more convenient.

      Not over water, it isn't, unless you've got power.

  2. They could have just asked any geek by Anonymous Coward · · Score: 2, Funny

    They seem to have that repulsion charge with girls.

    1. Re:They could have just asked any geek by Anonymous Coward · · Score: 5, Funny

      So you are saying that if a geek guy stops and listens to a girl, that she'll find him attractive?

    2. Re:They could have just asked any geek by MightyYar · · Score: 1

      That wears off around 30 or so...

      --
      W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.
    3. Re:They could have just asked any geek by OneAhead · · Score: 1

      Well played sir or madam. Very well played.

    4. Re:They could have just asked any geek by somersault · · Score: 2

      I have data points that indicate this to be correct at least some of the time. There may be just a little more to it of course, but I'm sure future physics papers will give us some more hints.

      --
      which is totally what she said
    5. Re:They could have just asked any geek by somersault · · Score: 5, Insightful

      Yeah that is about when the average female starts to think a solid mate who will provide for her and care about her, is a tad more important than playing idiotic mindgames, teasing, and whoring for attention

      Counter-point: it's also when your average geek has settled into a well paying job/career.

      --
      which is totally what she said
    6. Re:They could have just asked any geek by Nerdfest · · Score: 3, Insightful

      A more jaded person would say it wears off around $100K or so.

    7. Re:They could have just asked any geek by besalope · · Score: 3, Funny

      I have data points that indicate this to be correct at least some of the time. There may be just a little more to it of course, but I'm sure future physics papers will give us some more hints.

      Pretty sure those are just outliers. Are you sure p from your dataset is remotely close to 0.05?

    8. Re:They could have just asked any geek by I+Mean,+What · · Score: 3, Funny

      Wait, who's bitter and angry?

    9. Re:They could have just asked any geek by somersault · · Score: 2

      Only one of them was into that type of thing, so we'll never know.

      --
      which is totally what she said
  3. Other applications by Anonymous Coward · · Score: 1

    How long till we can turn this technology into space ship energy shields? I'm sure they'd be handy with all the space junk we've created...

    1. Re:Other applications by Anonymous Coward · · Score: 1

      If you ever need to repel very specifically shaped/timed and energy pulses of charged particles, it would be perfect for a space craft if you don't mind other charged particles still being attracted and it doing nothing for neutral objects.

  4. Great explanations by jez9999 · · Score: 4, Funny

    It's textbook physics: An electric charge near the surface of a material gets pulled toward the surface. However, if the charge is spread out into the right shape and moves fast enough, that attraction becomes a repulsion, one physicist calculates.

    This finally explains so much about women's behaviour towards me.

    --
    == Jez ==
    Do you miss Firefox? Try Pale Moon.
    1. Re:Great explanations by Impy+the+Impiuos+Imp · · Score: 2

      Even quoting to her how Tony Stark's repulsor rays work?

      --
      (-1: Post disagrees with my already-settled worldview) is not a valid mod option.
  5. For the door that you push instead of pull by Anonymous Coward · · Score: 1

    Now you won't look so bad.

  6. They should work on the reverse by Spy+Handler · · Score: 2

    we already know lots of ways to push things... jet engines to push planes, gunpowder to push bullets out of a gun, etc.

    What we need is a way to PULL things, so we can make a tractor beam. So far we got... nothing.

    1. Re:They should work on the reverse by multiben · · Score: 4, Funny

      Sure we do. Rope!

    2. Re:They should work on the reverse by Tough+Love · · Score: 5, Funny

      Why didn't I think of that? A matter beam. Brilliant.

      --
      When all you have is a hammer, every problem starts to look like a thumb.
    3. Re:They should work on the reverse by Carewolf · · Score: 4, Funny

      All personal at battle stations: Fire the matter beam!!

      *poke*

    4. Re:They should work on the reverse by jeffb+(2.718) · · Score: 1

      This is my new favorite euphemism of the day.

  7. Re:ION engines? by Anonymous Coward · · Score: 4, Informative

    It isn't like an ion engine at all. What they are saying is that electrostatic induction is not always attractive but it takes very specific conditions to make it repulsive. An ion engine doesn't use induction. Induction is the force between a neutrally charged object and a charged object.

  8. Re:ION engines? by Anonymous Coward · · Score: 1

    Ion drives require no such trickery; positive ions are accelerated by the electrical field between a positive and negative grid with enough energy to carry them clear of the negative grid once they've passed through it. There's no attraction turning into repulsion or vice versa, just the basic physics that you learnt at school.

  9. This is not news by G3ckoG33k · · Score: 1

    I woke up one morning and the attraction I had felt the night before had turned into repulsion.

    So what is new? That it is on Slashdot?

    1. Re:This is not news by Tablizer · · Score: 1

      And it had nothing to do with those 8 beers you had?

      --
      Table-ized A.I.
  10. theoretical bs by illestov · · Score: 1
    sigh.. another ridiculous claim from some random physicist grabs the headlines because it "violates the laws of physics"

    And if a charge moves through the glass faster than light can, it creates a shockwave of light

    1. Re:theoretical bs by Chuckstar · · Score: 4, Informative

      Nothing in the article violates the laws of physics. It's merely a question of who did the math more accurately for the specific case of the given arrangement of electrons.

      Cherenkov radiation is a well understood phenomenon. What you are missing is that the cosmic speed limit is the speed of light in a vacuum. Where the speed of light is slower (i.e. glass), it does not violate the laws of physics for a particle to move faster than that speed. In the given example: the electrons move faster in glass than light moves in glass, but still slower than light moves in a vacuum.

    2. Re:theoretical bs by History's+Coming+To · · Score: 4, Informative

      Nope, they're referring to Cerenkov radiation, it's a known effect and produces a very pretty blue light in nuclear reactors. It occurs when the phase velocity travels faster than the speed of light in that medium which is all fine and dandy and breaks no rules at all.

      --
      Please consider this account deleted, I just can't be bothered with the spam anymore.
    3. Re:theoretical bs by illestov · · Score: 1

      For Cherenkov Radioation , doesn't the charged particle have to move through a dialectic medium, not above its surface?

    4. Re:theoretical bs by Anonymous Coward · · Score: 1

      Yes, but in this case the particles moving in the glass are being forced by the passing electron outside it.

    5. Re:theoretical bs by Muad'Dave · · Score: 2

      For Cherenkov Radioation , doesn't the charged particle have to move through a dialectic medium, not above its surface?

      I don't think the charges use spirit guides to exchange logical arguments to resolve disagreements.

      --
      Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
    6. Re:theoretical bs by Muad'Dave · · Score: 2

      Not in the least. I've been in the 'core' of a couple of small research-grade swimming pool reactors (including this one), and you can see the blue light quite well and with no danger from radiation.

      --
      Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
  11. It's obvious when you think about it by beer_maker · · Score: 1

    I was a starship trooper till I took a matter beam to the knee ...

    --
    Hmmm. Your ideas are intriguing to me and I wish to subscribe to your newsletter.
  12. All you need to do is... by jeffb+(2.718) · · Score: 1

    ...keep your velocity higher than 80% or so of c. If your velocity drops below the velocity of light in the repelling surface, the Cherenkov radiation goes away, there's no more repulsion, and you land on the surface cruising at .5c or so. Hope the tires on your landing gear are properly inflated.

    Actually, now that I think about it, you'd probably get plenty of backup lift from the relativistic plasma formerly constituting the repulsive surface and the bottom of your vehicle. I withdraw my objection.