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(Possibly stupid) LHC question...

  • 10-09-2008 11:25am
    #1
    cornbb
    Registered Users, Registered Users 2 Posts: 6,790 ✭✭✭


    If the proton beams are travelling in opposite directions at "close to the speed of light", then what is the closing speed of the beams? :confused:


Comments

  • #2
    koolkakool
    Closed Accounts Posts: 74 ✭✭koolkakool


    I have actually been thinking about that same thing...


  • #3
    Spear
    Moderators, Computer Games Moderators, Technology & Internet Moderators, Help & Feedback Category Moderators Posts: 25,758 CMod ✭✭✭✭Spear


    cornbb wrote: »
    If the proton beams are travelling in opposite directions at "close to the speed of light", then what is the closing speed of the beams? :confused:

    Stick in your numbers and there you go.

    http://en.wikipedia.org/wiki/Lorentz_equations


  • #4
    timmywex
    Registered Users, Registered Users 2 Posts: 2,626 ✭✭✭timmywex


    They are accelerated to the speed of light, but when they come back around, they will be at about 99.9% speed of light aparently, even though its in a vacum, there is obiously some kind of friction being created with whatever way they made the vacum....if that makes sense!


  • #5
    Podge_irl
    Moderators, Sports Moderators Posts: 28,138 Mod ✭✭✭✭Podge_irl


    timmywex wrote: »
    They are accelerated to the speed of light, but when they come back around, they will be at about 99.9% speed of light aparently, even though its in a vacum, there is obiously some kind of friction being created with whatever way they made the vacum....if that makes sense!

    They are not accelerated to the speed of light, they are accelerated to close to the speed of light. No massive particle can actually be accelerated to the velocity of light (in a vacuum).

    As regards the closing speeds of the beams, it will be slightly closer to the speed of light then the individual beams, but still less then the speed of light. Addition of velocities is highly non-linear at velocities that close to c.


  • #6
    timmywex
    Registered Users, Registered Users 2 Posts: 2,626 ✭✭✭timmywex


    Podge_irl wrote: »
    They are not accelerated to the speed of light, they are accelerated to close to the speed of light. No massive particle can actually be accelerated to the velocity of light (in a vacuum).

    As regards the closing speeds of the beams, it will be slightly closer to the speed of light then the individual beams, but still less then the speed of light. Addition of velocities is highly non-linear at velocities that close to c.


    Well, there ya go! I had been told that it is accelerates to the speed of light, but tbh podge's version above sounds better/more right!


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  • #7
    cornbb
    Registered Users, Registered Users 2 Posts: 6,790 ✭✭✭cornbb


    Podge_irl wrote: »
    They are not accelerated to the speed of light, they are accelerated to close to the speed of light. No massive particle can actually be accelerated to the velocity of light (in a vacuum).

    As regards the closing speeds of the beams, it will be slightly closer to the speed of light then the individual beams, but still less then the speed of light. Addition of velocities is highly non-linear at velocities that close to c.

    Aaah well that's the only thing that makes sense I get. Damn you Theory of Relativity, messing with my perception of the universe...

    I suspect your answer is the same as Spear's, only in human-readable form :pac:


  • #8
    kelly1
    Registered Users, Registered Users 2 Posts: 5,026 ✭✭✭kelly1


    Podge_irl wrote: »
    They are not accelerated to the speed of light, they are accelerated to close to the speed of light. No massive particle can actually be accelerated to the velocity of light (in a vacuum).

    As regards the closing speeds of the beams, it will be slightly closer to the speed of light then the individual beams, but still less then the speed of light. Addition of velocities is highly non-linear at velocities that close to c.
    That's an interesting paradox, if that's the correct word. Intuitively, you would expect their relative velocites to double up but maybe it's more like effectively halving the mass of each particle?


  • #9
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    kelly1 wrote: »
    That's an interesting paradox, if that's the correct word. Intuitively, you would expect their relative velocites to double up but maybe it's more like effectively halving the mass of each particle?

    The mass of a particle is invariant. It does not change with velocity. There's a convention which invovles the increase of 'relativistic mass' with velocity but it's horrible.

    And I wouldn't say it's a paradox. Relativity certainly has paradoxes, but the nonlinear addition of velocities simply means (v1) + (v2) does not equal (v1 + v2)


  • #10
    dudara
    Registered Users, Registered Users 2 Posts: 33,518 ✭✭✭✭dudara


    kelly1 wrote: »
    That's an interesting paradox, if that's the correct word. Intuitively, you would expect their relative velocites to double up

    This is what happens in Gallilean relativity (based on everyday speeds etc)

    However, this does not hold at relativistic speeds (ie close to the speed of light). Use the Lorentz equations as posted by a previous poster to determine the combined velocity of both particles.


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